JP2014203781A - Nonaqueous electrolytic secondary battery, and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a nonaqueous electrolytic secondary battery having a coating film of a preferred form on a surface of a negative electrode active material, and arranged so that a predetermined shape of a battery case is kept by suppressing the rise in an internal pressure of the battery case.SOLUTION: A nonaqueous electrolytic secondary battery 10 comprises: an electrode assembly 50 having a positive electrode 64 and a negative electrode 84; a nonaqueous electrolytic solution; and a battery case 15 holding therein the electrode assembly 50 and the nonaqueous electrolytic solution. The negative electrode 84 has a negative electrode mixture layer 86 including at least a negative electrode active material. The negative electrode mixture layer 86 includes a calcium salt of carboxymethyl cellulose. On the surface of the negative electrode active material, a coating film including at least one of phosphorus and boron is formed. The nonaqueous electrolytic solution contains calcium oxalate.

Description

  The present invention relates to a non-aqueous electrolyte secondary battery and a method for manufacturing the same.

  Lithium ion secondary batteries and other non-aqueous electrolyte secondary batteries are becoming increasingly important as on-vehicle power supplies or personal computers and portable terminals. In particular, a lithium ion secondary battery that is lightweight and obtains a high energy density is preferable as a high-output power source mounted on a vehicle.

  By the way, in a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery, a part of the non-aqueous electrolyte is decomposed during charging, and the decomposition product is formed on the surface of the negative electrode active material (for example, natural graphite particles). A film, that is, a SEI (Solid Electrolyte Interface) film may be formed. The SEI film plays a role of protecting the negative electrode active material, but is formed by consuming charge carriers (for example, lithium ions) in the non-aqueous electrolyte. In other words, the charge carriers can no longer contribute to the battery capacity by being fixed in the SEI film. For this reason, if the amount of the SEI film is large, it becomes a factor of reducing the capacity retention rate (decreasing cycle characteristics).

In order to cope with such a problem, various additives are added to the non-aqueous electrolyte in order to form a stable film on the surface of the negative electrode active material in advance instead of the SEI film. In a non-aqueous electrolyte secondary battery having a coating formed by decomposition of an additive, it is known that reaction resistance is reduced and battery life (for example, capacity retention rate) is improved. For example, Patent Document 1 discloses a non-aqueous electrolyte solution in which a non-aqueous electrolyte solution containing an oxalato complex compound containing at least one of element B and element P (hereinafter referred to as “BP-oxalato compound”) is used. A secondary battery is described. Patent Document 2 describes a non-aqueous electrolyte secondary battery in which a non-aqueous electrolyte containing LiB (C ₂ O ₄ ) ₂ is used as an example of a BP-oxalato compound.

JP 2012-243478 A JP 2012-146650 A JP 2012-199198 A

By the way, in a non-aqueous electrolyte secondary battery containing a BP-oxalato compound as an additive, a stable film can be formed on the surface of the negative electrode active material by decomposing the BP-oxalato compound during initial charge / discharge. . Here, the higher the concentration of the BP-oxalato compound contained in the non-aqueous electrolyte, the more likely the film of the preferred embodiment is formed on the surface of the negative electrode active material, but when the film is formed, BP-oxalato Carbon monoxide (CO) and carbon dioxide (CO ₂ ) are mainly generated based on the reductive decomposition of the compound. For this reason, the higher the concentration of the BP-oxalato compound contained in the non-aqueous electrolyte, the more gas (that is, CO and CO ₂ ) based on the reductive decomposition of the BP-oxalato compound exists in the battery case. The internal pressure of the case can increase. If the internal pressure of the battery case becomes too large, the volume in the non-aqueous electrolyte secondary battery increases and the battery case may expand in the thickness direction. Thus, if the battery case expands in the thickness direction, it becomes difficult to constrain a plurality of nonaqueous electrolyte secondary batteries (unit cells) to construct a battery pack having a predetermined shape.

  The present invention has been created to solve the above-described conventional problems, and its purpose is to maintain a predetermined shape (that is, a predetermined thickness) of the battery case by suppressing an increase in the internal pressure of the battery case. In addition, another object of the present invention is to provide a method for producing a non-aqueous electrolyte secondary battery having a coating of a preferred embodiment on the surface of the negative electrode active material.

In order to achieve the above object, the present inventor has conducted various studies, and as a result, the presence of calcium ions in the non-aqueous electrolyte causes gas based on the reductive decomposition of the BP-oxalato complex compound (that is, CO and CO). It was found that the above object can be realized by preventing the occurrence of ₂ ).

  That is, the nonaqueous electrolyte secondary battery manufacturing method disclosed herein prepares a positive electrode having a positive electrode mixture layer containing at least a positive electrode active material and a negative electrode having a negative electrode mixture layer containing at least a negative electrode active material, Here, at least one of the prepared positive electrode mixture layer and the negative electrode mixture layer contains a calcium salt of carboxymethyl cellulose; producing an electrode body using the prepared positive electrode and negative electrode; Injecting a non-aqueous electrolyte containing the oxalato complex compound containing at least one of phosphorus and boron as a constituent element into the battery case to produce an assembly; Initial charging up to a charging voltage of

In this specification, the “non-aqueous electrolyte secondary battery” includes a non-aqueous electrolyte (typically, an electrolyte containing a supporting salt (supporting electrolyte) in a non-aqueous solvent (organic solvent)). Battery.
In the present specification, the term “secondary battery” refers to a battery that can be repeatedly charged and discharged, and is a term that includes a so-called chemical battery such as a lithium ion secondary battery and a physical battery such as an electric double layer capacitor.

According to the method for manufacturing a non-aqueous electrolyte secondary battery provided by the present invention, at least one of phosphorus and boron contained in the non-aqueous electrolyte is configured by subjecting the assembly to a predetermined charging process. The oxalato complex compound contained as an element is decomposed, and a film based on the oxalato complex compound is formed on the surface of the negative electrode active material. A non-aqueous electrolyte secondary battery having such a coating exhibits excellent battery characteristics (low reaction resistance and high capacity retention rate). Moreover, at the time of the said charge process, an oxalate ion will exist in a non-aqueous electrolyte by decomposition | disassembly of the said oxalato complex compound. When oxalate ions are present alone in the non-aqueous electrolyte, the oxalate ions are further reduced and decomposed during the charging process to produce CO and CO ₂ . However, since at least one of the positive electrode mixture layer and the negative electrode mixture layer contains a calcium salt of carboxymethyl cellulose, calcium ions are liberated in the nonaqueous electrolytic solution. The liberated calcium ions react with the oxalate ions in the non-aqueous electrolyte and become calcium oxalate. Thereby, reductive decomposition of oxalate ions can be suppressed, generation of CO and CO ₂ can be prevented, and an increase in internal pressure of the battery case can be suppressed. For this reason, deformation of the shape of the battery case (especially the shape in the thickness direction) accompanying the generation of gas is prevented, and the non-aqueous electrolyte secondary that can stably build the assembled battery with a preset binding force A battery can be manufactured. Further, according to the production method, separately pull process gas (CO and CO ₂₎ based on the decomposition of the oxalate complex compound from the battery case is not required.

In a preferred embodiment of the production method disclosed herein, when the total solid content of the negative electrode mixture layer is 100% by mass, the content of the calcium salt of carboxymethyl cellulose contained in the negative electrode mixture layer is 0. The carboxymethylcellulose calcium salt (CMC-Ca) is included in the negative electrode mixture layer so that the content is 5% by mass or more and 1.2% by mass or less.
According to such a configuration, there is no excess or deficiency in the content of CMC-Ca, and generation of gases (CO and CO ₂ ) based on decomposition of the oxalato complex compound can be better suppressed.

In another preferred embodiment of the production method disclosed herein, the concentration of the oxalato complex compound is 0.02 mol / L to 0.04 mol / L.
According to this configuration, it is possible to produce a nonaqueous electrolyte secondary battery with reduced reaction resistance and an excellent capacity retention rate.

In another preferred embodiment of the production method disclosed herein, LiPF ₂ (C ₂ O ₄ ) ₂ is used as the oxalato complex compound.
According to such a configuration, it is possible to form a film of a preferred embodiment on the surface of the negative electrode active material.

  According to the present invention, a nonaqueous electrolyte secondary battery is provided as another aspect for realizing the above object. That is, the nonaqueous electrolyte secondary battery disclosed herein includes an electrode body having a positive electrode and a negative electrode, a nonaqueous electrolyte, and a battery case that houses the electrode body and the nonaqueous electrolyte. The positive electrode has a positive electrode mixture layer containing at least a positive electrode active material, the negative electrode has a negative electrode mixture layer containing at least a negative electrode active material, and the positive electrode mixture layer and the negative electrode mixture layer At least one contains a calcium salt of carboxymethyl cellulose, a film containing at least one of phosphorus and boron is formed on the surface of the negative electrode active material, and the non-aqueous electrolyte contains calcium oxalate.

In the non-aqueous electrolyte secondary battery provided by the present invention, at least one of the positive electrode mixture layer and the negative electrode mixture layer contains a calcium salt of carboxymethyl cellulose, and the surface of the negative electrode active material has at least one of phosphorus and boron. The non-aqueous electrolyte contains calcium oxalate.
According to such a configuration, since a film containing at least one of phosphorus and boron is formed on the surface of the negative electrode active material, excellent battery characteristics (low reaction resistance and high capacity retention rate) are exhibited. In the non-aqueous electrolyte, oxalate ions react with calcium ions and exist as calcium oxalate, so that CO and CO ₂ are not generated based on reductive decomposition of oxalate ions. Thereby, even if it charges / discharges, the raise of the internal pressure of a battery case is suppressed. For this reason, deformation of the shape of the battery case (particularly the shape in the thickness direction) accompanying the generation of gas is prevented, and the non-aqueous electrolyte can stably build the assembled battery with a preset binding force It can be a secondary battery.

In a preferred embodiment of the non-aqueous electrolyte secondary battery disclosed herein, the calcium salt of carboxymethyl cellulose is contained in the negative electrode mixture layer, and the total solid content of the negative electrode mixture layer is 100 mass. %, The content of the calcium salt of the carboxymethyl cellulose contained in the negative electrode mixture layer is 0.5% by mass or more and 1.2% by mass or less.
According to such a configuration, the gas (CO and CO ₂ ) does not exist excessively in the battery case, and the internal pressure of the battery case is kept low, so that the predetermined shape (that is, the predetermined thickness) of the battery case is maintained. Has been.

In another preferred embodiment of the nonaqueous electrolyte secondary battery disclosed herein, the concentration of the calcium oxalate is at least 0.01 mol / L. Preferably it is 0.04 mol / L-0.08 mol / L.
According to such a configuration, the reaction resistance is reduced, and a non-aqueous electrolyte secondary battery having an excellent capacity retention rate can be obtained.

In another preferred embodiment of the non-aqueous electrolyte secondary battery disclosed herein, the non-aqueous electrolyte further includes an oxalato complex compound containing at least one of phosphorus and boron as a constituent element.
According to such a configuration, a coating can be further formed on the surface of the negative electrode active material when the non-aqueous electrolyte secondary battery is used, and generation of gas (CO and CO ₂ ) based on decomposition of the oxalato complex compound is suppressed. be able to.

In another preferred embodiment of the non-aqueous electrolyte secondary battery disclosed herein, the non-aqueous electrolyte further includes a gas generating agent capable of decomposing and generating gas when a predetermined battery voltage is exceeded. In addition, the battery case includes a current interrupting mechanism that operates when the pressure in the battery case increases as the gas is generated.
According to this configuration, when the battery voltage of the non-aqueous electrolyte secondary battery exceeds a predetermined battery voltage, the gas generating agent is decomposed, and the internal pressure in the battery case is increased by the generated gas, thereby operating the current interrupting mechanism. Is done. Since the gas (CO and CO ₂ ) does not exist excessively in the battery case and the internal pressure of the battery case is kept low, malfunction of the current interrupt mechanism is prevented.

  Further, the present invention provides, as another aspect, a structure for constructing the nonaqueous electrolyte secondary battery disclosed herein, that is, an electrode body having a positive electrode and a negative electrode, a nonaqueous electrolyte, and the above electrode body And a battery case containing the non-aqueous electrolyte solution, and a non-aqueous electrolyte secondary battery assembly before initial charging. In such an assembly, the positive electrode has a positive electrode mixture layer containing at least a positive electrode active material, and the negative electrode has a negative electrode mixture layer containing at least a negative electrode active material, and the positive electrode mixture layer and the negative electrode compound layer. At least one of the material layers contains a calcium salt of carboxymethyl cellulose, and the nonaqueous electrolytic solution contains an oxalato complex compound containing at least one of phosphorus and boron as a constituent element.

In such an assembly, calcium ions are released into the non-aqueous electrolyte from at least one of the positive electrode mixture layer and the negative electrode mixture layer. Therefore, when the assembly is initially charged to a predetermined charging voltage, oxalate ions generated by reductive decomposition of the oxalato complex compound react with calcium ions to become calcium oxalate. Thereby, reductive decomposition of oxalate ions can be suppressed, generation of CO and CO ₂ can be prevented, and a nonaqueous electrolyte secondary battery in which an increase in internal pressure of the battery case is suppressed can be obtained. Furthermore, in such a non-aqueous electrolyte secondary battery, a film of a preferred embodiment is formed on the surface of the negative electrode active material based on the reductive decomposition of the oxalato complex compound.

In a preferred embodiment of the assembly disclosed herein, the calcium salt of carboxymethyl cellulose is contained in the negative electrode mixture layer, and when the total solid content of the negative electrode mixture layer is 100% by mass, Content of the calcium salt of the said carboxymethylcellulose contained in the said negative electrode compound material layer is 0.5 mass% or more and 1.2 mass% or less.
When initial charging is performed on such an assembly, a non-aqueous electrolyte secondary battery in which generation of gas (CO and CO ₂ ) based on decomposition of the oxalato complex compound is better suppressed can be obtained.

In another preferred embodiment of the assembly disclosed herein, the concentration of the oxalato complex compound in the non-aqueous electrolyte is 0.02 mol / L to 0.04 mol / L.
When initial charging is performed on such an assembly, a non-aqueous electrolyte secondary battery with reduced reaction resistance and an excellent capacity retention rate can be obtained.

In another preferred embodiment of the assembly disclosed herein, the oxalato complex compound is LiPF ₂ (C ₂ O ₄ ) ₂ .
When initial charging is performed on such an assembly, a nonaqueous electrolyte secondary battery in which a film of a preferred embodiment is formed on the surface of the negative electrode active material can be obtained.

In another preferred aspect of the assembly disclosed herein, the non-aqueous electrolyte further includes a gas generating agent capable of decomposing and generating gas when a predetermined battery voltage is exceeded, and the battery case Includes a current interrupt mechanism that operates when the pressure in the battery case increases as the gas is generated.
When initial charging is performed on such an assembly, generation of gas (CO and CO ₂ ) based on decomposition of the oxalato complex compound is suppressed, so that malfunction of the current interrupting mechanism is prevented.

  As described above, any non-aqueous electrolyte secondary battery disclosed herein or a non-aqueous electrolyte secondary battery (for example, a lithium ion secondary battery) obtained by any of the manufacturing methods disclosed herein. Then, since the coating of a preferred embodiment is formed on the surface of the negative electrode active material, the battery performance is excellent, and the increase in the internal pressure of the battery case is suppressed, so that the non-aqueous solution in which the predetermined shape of the battery case is maintained. It can be an electrolyte secondary battery. Therefore, a plurality of (for example, 40 to 80) non-aqueous electrolyte secondary batteries obtained by any of the non-aqueous electrolyte secondary batteries disclosed herein or any of the manufacturing methods disclosed herein. ) Are connected by a predetermined binding force (typically connected in series). It can also be used as a drive power source for vehicles (typically automobiles, particularly automobiles equipped with electric motors such as hybrid cars, electric cars, and fuel cell cars).

It is a perspective view which shows typically the external shape of the non-aqueous-electrolyte secondary battery which concerns on one Embodiment of this invention. It is sectional drawing which follows the II-II line | wire in FIG. It is a flowchart for demonstrating the manufacturing method of the nonaqueous electrolyte secondary battery which concerns on one Embodiment of this invention. It is a perspective view which shows typically the assembled battery which combined the nonaqueous electrolyte secondary battery which concerns on one Embodiment of this invention. It is a side view which shows typically the vehicle (automobile) provided with the nonaqueous electrolyte secondary battery which concerns on this invention. It is a graph which shows the relationship between content of the calcium salt of carboxymethylcellulose (CMC-Ca), and gas generation amount. LiPF _{2 (C 2 O 4)} is a graph showing the relationship between the ₂ concentrations and reaction resistance. LiPF _{2 (C 2 O 4)} is a graph showing the relationship between the _two levels and capacity maintenance ratio.

  Hereinafter, preferred embodiments of the present invention will be described. It should be noted that matters other than matters specifically mentioned in the present specification and necessary for carrying out the present invention can be grasped as design matters of those skilled in the art based on the prior art in this field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field. Hereinafter, the case of a lithium ion secondary battery may be described in more detail as a typical example, but the application target of the present invention is not intended to be limited to such a battery.

  As a preferred embodiment of a method for producing a non-aqueous electrolyte secondary battery disclosed herein, a method for producing a lithium ion secondary battery will be described in detail as an example. Is not intended to be limited to such types of secondary batteries. For example, the present invention can also be applied to a non-aqueous electrolyte secondary battery using other metal ions (for example, magnesium ions) as a charge carrier.

  As shown in FIG. 3, the manufacturing method of the lithium ion secondary battery (non-aqueous electrolyte secondary battery) disclosed herein includes a positive / negative electrode preparation step (S10), an electrode body preparation step (S20), A three-dimensional production process (S30) and an initial charging process (S40) are included.

≪Positive electrode preparation process (S10) ≫
First, the positive and negative electrode preparation step (S10) will be described. In the present embodiment, as the positive and negative electrode preparation step, a positive electrode including a positive electrode active material and a negative electrode including a negative electrode active material are prepared. In a preferred embodiment, the method further includes preparing a separator disposed between the positive electrode and the negative electrode.

  The negative electrode of the lithium ion secondary battery disclosed herein includes a negative electrode current collector and a negative electrode mixture layer including at least a negative electrode active material formed on the surface of the negative electrode current collector. The negative electrode mixture layer can contain optional components such as a binder and a thickener as needed in addition to the negative electrode active material.

  As the negative electrode current collector, a conductive member made of a metal having good conductivity is preferably used, like the current collector used in the negative electrode of a conventional lithium ion secondary battery. For example, copper, nickel, or an alloy mainly composed of them can be used. The shape of the negative electrode current collector can vary depending on the shape or the like of the lithium ion secondary battery, and is not particularly limited, and may be various forms such as a foil shape, a sheet shape, a rod shape, and a plate shape.

As the negative electrode active material, one kind or two or more kinds of materials conventionally used for lithium ion secondary batteries can be used without particular limitation. For example, a particulate (or spherical, scale-like) carbon material including a graphite structure (layered structure) at least partially, a lithium transition metal composite oxide (for example, a lithium titanium composite oxide such as Li ₄ Ti ₅ O ₁₂ ), Lithium transition metal composite nitride, etc. Examples of the carbon material include natural graphite, artificial graphite (artificial graphite), non-graphitizable carbon (hard carbon), graphitizable carbon (soft carbon), and the like. The average particle diameter of the negative electrode active material is, for example, in the range of about 1 μm to 50 μm (usually 5 μm to 30 μm), which is based on various commercially available laser diffraction / scattering methods. The median diameter (D50: 50% volume average particle diameter) that can be derived from the particle size distribution measured based on the particle size distribution measuring device. For example, a negative electrode active material at least partially coated with an amorphous carbon film can be obtained by mixing a negative electrode active material with a pitch and baking it.

  As said binder, the thing similar to the binder used for the negative electrode of a general lithium ion secondary battery can be employ | adopted suitably. For example, when an aqueous paste composition is used to form the negative electrode mixture layer, a water-soluble polymer material or a water-dispersible polymer material can be preferably used. Examples of the water dispersible polymer include rubbers such as styrene butadiene rubber (SBR); polyethylene oxide (PEO), vinyl acetate copolymer and the like. Styrene butadiene rubber is preferably used.

  The “aqueous paste-like composition” is a concept indicating a composition using water or a mixed solvent mainly composed of water as a dispersion medium for the negative electrode active material. As a solvent other than water constituting such a mixed solvent, one or more organic solvents (lower alcohol, lower ketone, etc.) that can be uniformly mixed with water can be appropriately selected and used.

  As the thickener, a calcium salt of carboxymethyl cellulose (CMC) (hereinafter sometimes abbreviated as “CMC-Ca”) is used. When the positive electrode mixture layer contains a calcium salt of carboxymethyl cellulose, it is not always necessary to include CMC-Ca in the negative electrode mixture layer. For example, the following water-soluble or water-dispersible polymers may be employed. . Examples of the water-soluble polymer include cellulose polymers such as methyl cellulose (MC), cellulose acetate phthalate (CAP), and hydroxypropyl methyl cellulose (HPMC); polyvinyl alcohol (PVA); In addition, the same materials as those mentioned as the binder can be appropriately employed.

  When the negative electrode mixture layer contains CMC-Ca, the content of calcium salt of carboxymethyl cellulose (CMC-Ca) contained in the negative electrode mixture layer when the total solid content of the negative electrode mixture layer is 100% by mass Is preferably 0.5% by mass or more and 1.2% by mass or less. More preferably, they are 0.5 mass% or more and 1 mass% or less (for example, 0.7 mass% or more and 1 mass% or less). The “content of calcium salt of carboxymethyl cellulose contained in the negative electrode mixture layer” includes the content of carboxymethyl cellulose from which calcium ions are released.

  The negative electrode disclosed here can be suitably manufactured, for example, generally by the following procedure. A paste-like composition for forming a negative electrode mixture layer is prepared by dispersing the above-described negative electrode active material and other optional components (such as a binder and a thickener) in an appropriate solvent (for example, water). . The prepared composition is applied (applied) to a negative electrode current collector, dried, and then compressed (pressed) to thereby form a negative electrode current collector and a negative electrode mixture layer formed on the negative electrode current collector. A negative electrode provided with can be produced. When CMC-Ca is used as the thickener, the produced negative electrode contains CMC-Ca in the negative electrode mixture layer.

  When CMC-Ca is used as the thickener, when the total solid content of the composition for forming a negative electrode mixture layer (that is, the total solid content excluding the solvent) is 100% by mass, The addition amount (content) of the calcium salt of carboxymethyl cellulose (CMC-Ca) contained in the composition is preferably 0.5% by mass or more and 1.2% by mass or less. More preferably, they are 0.5 mass% or more and 1 mass% or less (for example, 0.7 mass% or more and 1 mass% or less). When the content of CMC-Ca is less than 0.5% by mass, the viscosity of the composition for forming a negative electrode mixture layer is too low, so that the composition for forming a negative electrode mixture layer is formed on the negative electrode current collector. There is a possibility that coating (application) may not be possible. That is, a dilatancy phenomenon occurs in the composition for forming a negative electrode mixture layer, and the composition is hardened at the time of coating. Therefore, the composition may not be discharged from the coating machine. Moreover, when content of CMC-Ca is too larger than 1.2 mass%, since the viscosity of the composition for negative electrode mixture layer formation is too high, there exists a possibility that coating (application | coating) nonuniformity may generate | occur | produce.

  The positive electrode of the lithium ion secondary battery disclosed here includes a positive electrode current collector and a positive electrode mixture layer including at least a positive electrode active material formed on the surface of the positive electrode current collector. The positive electrode mixture layer may contain an optional component such as a conductive material and a binder (binder) in addition to the positive electrode active material.

As the positive electrode current collector, aluminum or an aluminum alloy mainly composed of aluminum is used as in the case of the positive electrode current collector used in the positive electrode of a conventional lithium ion secondary battery. The shape of the positive electrode current collector can be the same as the shape of the negative electrode current collector.

Examples of the positive electrode active material include materials capable of inserting and extracting lithium ions, and include lithium-containing compounds (for example, lithium transition metal composite oxides) containing a lithium element and one or more transition metal elements. For example, lithium nickel composite oxide (for example, LiNiO ₂ ), lithium cobalt composite oxide (for example, LiCoO ₂ ), lithium manganese composite oxide (for example, LiMn ₂ O ₄ ), or lithium nickel cobalt manganese composite oxide (for example, LiNi _{1). / 3} Co _1/3 Mn _1/3 O ₂ ), a ternary lithium-containing composite oxide.
In addition, a polyanionic compound (for example, LiFePO ₄₎ whose general formula is represented by LiMPO _4, LiMVO _4, or Li ₂ MSiO ₄ (wherein M is at least one element of Co, Ni, Mn, and Fe), etc. ₄ , LiMnPO ₄ , LiFeVO ₄ , LiMnVO ₄ , Li ₂ FeSiO ₄ , Li ₂ MnSiO ₄ , Li ₂ CoSiO ₄ ) may be used as the positive electrode active material.

  The conductive material is not limited to a specific conductive material as long as it is conventionally used in this type of lithium ion secondary battery. For example, carbon materials such as carbon powder and carbon fiber can be used. As the carbon powder, various carbon blacks (for example, acetylene black, furnace black, ketjen black, etc.), carbon powders such as graphite powder can be used. Among these, acetylene black (AB) is a preferable carbon powder. Such conductive materials can be used singly or in appropriate combination of two or more.

  As said binder (binder), the thing similar to the binder used for the positive electrode of a common lithium ion secondary battery can be employ | adopted suitably. For example, when a solvent-based paste-like composition (a paste-like composition includes a slurry-like composition and an ink-like composition) is used as the composition for forming the positive electrode mixture layer, a polyfluoride is used. Polymer materials that dissolve in an organic solvent (non-aqueous solvent) such as vinylidene chloride (PVDF) and polyvinylidene chloride (PVDC) can be used. Alternatively, when an aqueous paste composition is used, a water-soluble (soluble in water) polymer material or a water-dispersible (water-dispersible) polymer material can be preferably used. Examples thereof include polytetrafluoroethylene (PTFE), sodium salt of carboxymethyl cellulose, calcium salt of carboxymethyl cellulose, styrene butadiene rubber (SBR), and the like. In addition, the polymer material illustrated above may be used as a thickener or other additives in the above composition in addition to being used as a binder.

  Here, the “solvent-based paste composition” is a concept indicating a composition in which the dispersion medium of the positive electrode active material is mainly an organic solvent (non-aqueous solvent). As the organic solvent, for example, N-methyl-2-pyrrolidone (NMP) can be used.

  The positive electrode disclosed here can be suitably manufactured, for example, generally by the following procedure. A paste-like composition for forming a positive electrode mixture layer is prepared by dispersing, in an organic solvent, the above-described positive electrode active material, conductive material, and a binder that is soluble in an organic solvent. A positive electrode comprising a positive electrode current collector and a positive electrode mixture layer formed on the positive electrode current collector by applying the prepared composition to the positive electrode current collector, drying, and then compressing (pressing) the positive electrode current collector. Can be produced. When CMC-Ca is used as the thickener, the produced positive electrode contains CMC-Ca in the positive electrode mixture layer.

  The separator disclosed here can use a conventionally well-known thing without a restriction | limiting in particular. For example, a porous sheet made of resin (a microporous resin sheet) can be preferably used. A porous polyolefin resin sheet such as polyethylene (PE) or polypropylene (PP) is preferred. For example, a PE single layer sheet, a PP single layer sheet, a two layer structure (PE / PP structure) in which a PE layer and a PP layer are laminated, and a three layer structure in which a PP layer is laminated on both sides of the PE layer. A sheet of (PP / PE / PP structure) or the like can be preferably used.

≪Electrode body production process (S20) ≫
Next, the electrode body manufacturing step (S20) will be described. In the electrode body manufacturing step, an electrode body is manufactured using the prepared positive electrode and negative electrode. Typically, an electrode body is produced using the prepared positive electrode, negative electrode and separator. Hereinafter, although the case where CMC-Ca is included in the negative electrode mixture layer will be described as an example, the same applies to the case where CMC-Ca is included in the positive electrode mixture layer.

  An electrode body (for example, a stacked electrode body or a wound electrode body) of a lithium ion secondary battery disclosed herein includes a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode. Yes. Here, the positive electrode formed in a sheet shape, the negative electrode formed in a sheet shape, and a wound electrode body (wound electrode body) including the separator will be described as an example. It is not intended to be limiting.

FIG. 2 shows a wound electrode body 50 according to the present embodiment. As shown in FIG. 2, the wound electrode body 50 is wound in the longitudinal direction in a state where a sheet-like positive electrode 64 and a sheet-like negative electrode 84 are laminated with a total of two long separators 90 interposed therebetween. Then, the flat wound electrode body 50 is produced by crushing the obtained wound body from the side direction and causing it to be ablated.
At the time of the above lamination, the positive electrode mixture layer non-formed portion of the positive electrode 64 (that is, the portion where the positive electrode current collector 62 is exposed without the formation of the positive electrode mixture layer 66) 63 and the negative electrode mixture layer of the negative electrode 84 are not formed. The positive electrode 64 and the negative electrode 84 are arranged in the width direction so that the formation portion (that is, the portion where the negative electrode current collector 82 is not formed without forming the negative electrode mixture layer 86) 83 protrudes from both sides in the width direction of the separator 90. Slightly shift and overlap. As a result, in the lateral direction with respect to the winding direction of the wound electrode body 50, the electrode mixture layer non-formed portions 63 and 83 of the positive electrode 64 and the negative electrode 84 are respectively wound core portions (that is, the positive electrode mixture layer 66 and the positive electrode 64). The negative electrode composite material layer 86 of the negative electrode 84 and the two separators 90 are closely wound around). A positive electrode terminal 60 (for example, made of aluminum) is joined to the positive electrode mixture layer non-formed portion 63 to electrically connect the positive electrode 64 and the positive electrode terminal 60 of the wound electrode body 50 formed in the flat shape. Similarly, a negative electrode terminal 80 (for example, made of nickel) is joined to the negative electrode mixture layer non-forming portion 83 to electrically connect the negative electrode 84 and the negative electrode terminal 80. The positive and negative electrode terminals 60 and 80 and the positive and negative electrode current collectors 62 and 82 can be joined by, for example, ultrasonic welding, resistance welding, or the like.

<< Assembly manufacturing process (S30) >>
Next, the assembly manufacturing process (S30) will be described. In the present embodiment, the produced wound electrode body 50 is accommodated in the battery case 15 and a predetermined nonaqueous electrolyte is injected into the battery case 15 to assemble the assembly (nonaqueous electrolyte secondary battery set). 3D) 70 is produced.

  As shown in FIGS. 1 and 2, the battery case 15 of the present embodiment is a battery case made of metal (for example, made of aluminum, and also preferably made of resin or laminate film), and the upper end is open. A case body (exterior case) 30 having a flat bottomed box shape (typically a rectangular parallelepiped shape) and a lid body 25 that closes the opening 20 of the case body 30 are provided. On the upper surface of the battery case 15 (that is, the lid body 25), a positive electrode terminal 60 that is electrically connected to the positive electrode 64 of the wound electrode body 50 and a negative electrode terminal that is electrically connected to the negative electrode 84 of the wound electrode body 50. 80 is provided. In addition, the lid body 25 is formed with an inlet 45 for injecting a non-aqueous electrolyte described later into the case body 30 (battery case 15) in which the wound electrode body 50 is accommodated. The injection port 45 is sealed with a sealing plug 48 after the nonaqueous electrolyte is injected. Further, as in the case of the conventional lithium ion secondary battery, the lid 25 is provided with a safety valve 40 for discharging the gas generated inside the battery case 15 to the outside of the battery case 15 when the battery is abnormal. ing. The wound electrode body 50 is placed in a case in a posture in which the wound axis of the wound electrode body 50 is laid down (that is, the opening 20 is formed in the normal direction of the wound axis of the wound electrode body 50). Housed in the main body 30. Thereafter, the opening portion 20 of the case body 30 is sealed with the lid body 25, thereby producing the assembly 70. The lid 25 and the case body 30 are joined by welding or the like.

  Inside the battery case 15 according to the present embodiment, a current interrupt mechanism (CID) 31 that operates when the pressure in the battery case 15 rises is provided. The current interruption mechanism 31 only needs to be configured to cut a conductive path (for example, a charging path) from at least one of the electrode terminals to the electrode body 50 when the internal pressure of the battery case 15 increases, and has a specific shape. It is not limited to. In the embodiment shown in FIG. 2, the current interruption mechanism 31 is provided between the positive electrode terminal 60 fixed to the lid body 25 and the electrode body 50, and when the internal pressure of the battery case 15 rises, the electrode body 50 extends from the positive electrode terminal 60. It is configured to cut the conductive path leading to.

  More specifically, the current interrupt mechanism 31 may include a first member 32 and a second member 34, for example. When the internal pressure of the battery case 15 increases, at least one of the first member 32 and the second member 34 is deformed and separated from the other, thereby cutting the conductive path. In the embodiment shown in FIG. 2, the first member 32 is a deformed metal plate, and the second member 34 is a connection metal plate joined to the deformed metal plate 32. The deformed metal plate (first member) 32 has an arch shape in which a central portion is curved downward, and a peripheral portion thereof is connected to the lower surface of the positive electrode terminal 60 via a current collecting lead terminal 35. Further, the tip of the curved portion 33 of the deformed metal plate 32 is joined to the upper surface of the connection metal plate 34. A positive electrode current collector plate 61 is joined to the lower surface (back surface) of the connection metal plate 34, and the positive electrode current collector plate 61 is connected to the positive electrode 64 (positive electrode current collector 62) of the electrode body 50. In this way, a conductive path from the positive electrode terminal 60 to the electrode body 50 is formed.

  The current interrupt mechanism 31 includes an insulating case 38 formed of plastic or the like. The insulating case 38 is provided so as to surround the deformed metal plate 32 and hermetically seals the upper surface of the deformed metal plate 32. The internal pressure of the battery case 15 does not act on the upper surface of the hermetically sealed curved portion 33. The insulating case 38 has an opening into which the curved portion 33 of the deformed metal plate 32 is inserted, and the lower surface of the curved portion 33 is exposed from the opening to the inside of the battery case 15. The internal pressure of the battery case 15 acts on the lower surface of the curved portion 33 exposed inside the battery case 15. In the current interrupt mechanism 31 having such a configuration, when the internal pressure of the battery case 15 increases, the internal pressure acts on the lower surface of the curved portion 33 of the deformed metal plate 32, and the curved portion 33 curved downward is pushed upward. The upward push of the curved portion 33 increases as the internal pressure of the battery case 15 increases. When the internal pressure of the battery case 15 exceeds the set pressure, the curved portion 33 is inverted so as to bend upside down and bend upward. Due to the deformation of the curved portion 33, the joint point 36 between the deformed metal plate 32 and the connection metal plate 34 is cut. As a result, the conductive path from the positive electrode terminal 60 to the electrode body 50 is cut, and the overcharge current is cut off.

  The current interrupt mechanism 31 is not limited to the positive terminal 60 side, and may be provided on the negative terminal 80 side. The current interrupt mechanism 31 is not limited to the mechanical cutting accompanied by the deformation of the deformed metal plate 32 described above. For example, the internal pressure of the battery case 50 is detected by a sensor, and the internal pressure detected by the sensor sets the set pressure. An external circuit that cuts off the charging current when exceeded can be provided as a current cut-off mechanism.

  The non-aqueous electrolyte disclosed herein includes an oxalate complex compound (hereinafter referred to as “BP-oxalato compound”) containing at least one of phosphorus and boron as an additive, and a non-aqueous solvent (organic solvent). ) At least. Typically, in addition to these, a nonaqueous electrolytic solution that further contains a lithium compound (supporting salt) that can be dissolved in a nonaqueous solvent to supply lithium ions is used.

The BP-oxalato compound disclosed here is an oxalato complex having a structural portion in which at least one oxalate ion (C ₂ O ₄ ²⁻ ) is coordinated to phosphorus (P) or boron (B). As the BP-oxalato compound, one produced by a known method or one obtained by purchasing a commercially available product is not particularly limited, and one or two or more kinds can be used. As a preferable BP-oxalato compound, a phosphorus-containing oxalato complex compound represented by the following formula (I) is exemplified. Moreover, the boron containing oxalato complex compound represented by following formula (II) is illustrated as a preferable BP-oxalato compound.

Here, A ⁺ in formulas (I) and (II) may be either an inorganic cation or an organic cation. Specific examples of the inorganic cation include alkali metal cations such as Li, Na, and K; alkaline earth metal cations such as Be, Mg, and Ca; other, Ag, Zn, Cu, Co, Fe, Ni, Mn, And metal cations such as Ti, Pb, Cr, V, Ru, Y, lanthanoids and actinoids; protons; and the like. Specific examples of organic cations include tetraalkylammonium ions such as tetrabutylammonium ion, tetraethylammonium ion and tetramethylammonium ion; trialkylammonium ions such as triethylmethylammonium ion and triethylammonium ion; other pyridinium ions and imidazoliums Ion, tetraethylphosphonium ion, tetramethylphosphonium ion, tetraphenylphosphonium ion, triphenylsulfonium ion, triethylsulfonium ion; and the like. Examples of preferred cations include lithium ions, tetraalkylammonium ions and protons.

As the BP-oxalato compound, a compound represented by the formula (I) is preferably used. Of these, LiPF ₂ (C ₂ O ₄ ) ₂ represented by the formula (I) is preferably used. Further, lithium bis (oxalato) borate (LiB (C ₂ O ₄ ) ₂ ) represented by the formula (II) is preferably used.

The concentration of the BP-oxalato compound (for example, LiPF ₂ (C ₂ O ₄ ) ₂ ) in the nonaqueous electrolytic solution is, for example, 0.01 mol / L or more and 0.1 mol / L or less. Preferably, it is 0.02 mol / L or more and 0.06 mol / L or less. More preferably, they are 0.02 mol / L or more and 0.04 mol / L or less. When the concentration of the BP-oxalato compound is in the above range, the effect of the present invention can be exhibited more and higher battery performance can be realized.

As the non-aqueous solvent (organic solvent), aprotic solvents such as carbonates, esters, ethers, nitriles, sulfones, and lactones can be used. For example, carbonates such as ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) are exemplified. Such organic solvents can be used alone or in combination of two or more.
Examples of the supporting salt (lithium compound) include lithium salts such as LiPF ₆ , LiClO ₄ , LiAsF ₆ , Li (CF ₃ SO ₂ ) ₂ N, LiBF ₄ , and LiCF ₃ SO ₃ . These supporting salts can be used alone or in combination of two or more. LiPF ₆ is particularly preferable. The concentration of the supporting salt is not particularly limited, but if it is too low, the amount of charge carriers (typically lithium ions) contained in the non-aqueous electrolyte is insufficient, and the ionic conductivity tends to decrease. On the other hand, when the concentration is extremely high, the viscosity of the non-aqueous electrolyte increases in a temperature range below room temperature (for example, 0 ° C. to 30 ° C.), and ion conductivity tends to decrease. For this reason, the concentration of the supporting salt is, for example, 0.1 mol / L or more (for example, 0.8 mol / L or more) and preferably 2 mol / L or less (for example, 1.5 mol / L or less).

  As shown in FIG. 2, the assembly 70 according to the present embodiment includes a stacked or wound electrode body 50 including a positive electrode 64 and a negative electrode 84 (wound electrode body) 50 and an initial charge including a non-aqueous electrolyte. This is the previous non-aqueous electrolyte secondary battery assembly 70. The negative electrode mixture layer 86 includes at least a calcium salt of carboxymethyl cellulose. The nonaqueous electrolytic solution contains at least an oxalato complex compound containing at least one of phosphorus and boron as a constituent element.

≪Initial charging process (S40) ≫
Next, the initial charging step (S40) will be described. In the present embodiment, the BP-oxalato compound-derived film is formed on the surface of the negative electrode active material in the negative electrode mixture layer 86 by performing initial charging of the assembly 70 to a predetermined charging voltage.

In this step, for example, the assembly 70 is charged at a charging rate of about 0.1 C to 2 C up to an upper limit voltage (e.g., 3.7 V to 4.1 V) when the battery is used. During this initial charge, the BP-oxalato compound is decomposed, and a film derived from the BP-oxalato compound is formed on the surface of the negative electrode active material in the negative electrode mixture layer 86. Oxalate ions are present in the non-aqueous electrolyte due to the decomposition of the BP-oxalato compound, but calcium ions liberated from CMC-Ca contained in the negative electrode mixture layer 86 are present in the non-aqueous electrolyte. Therefore, oxalate ions react with calcium ions to become calcium oxalate. Thereby, reductive decomposition of oxalate ions can be suppressed, generation of CO and CO ₂ can be prevented, and an increase in internal pressure of the battery case 15 can be suppressed. As a result, deformation of the shape (particularly the shape in the thickness direction) of the battery case 15 due to the generation of CO or CO ₂ is prevented. Therefore, it is not necessary to remove the gas generated in the battery case 15 after the charge / discharge process. After charging the assembly 70, the battery is discharged to a predetermined voltage (for example, 3V to 3.2V) at a discharge rate of about 0.1C to 2C. Moreover, it is preferable to repeat the said charging / discharging several times (for example, 3 times). By performing the charging / discharging process on the assembly 70 in this manner, the assembly 70 becomes a usable battery, that is, a lithium ion secondary battery (non-aqueous electrolyte secondary battery) 10 (FIGS. 1 and 2). reference). “1C” means the amount of current that can charge the battery capacity (Ah) predicted from the theoretical capacity of the positive electrode in one hour.

  Next, the lithium ion secondary battery (nonaqueous electrolyte secondary battery) 10 manufactured by the manufacturing method disclosed herein will be described.

  As shown in FIG. 2, the lithium ion secondary battery 10 according to this embodiment includes a stacked or wound electrode body 50 (here, a wound electrode body) 50 including a positive electrode 64 and a negative electrode 84 and a separator 90, and a non- The battery case 15 which accommodates water electrolyte solution, the electrode body 50, and nonaqueous electrolyte solution is provided. Calcium oxalate is present in the non-aqueous electrolyte, and the BP-oxalato compound that has not been decomposed in the charge / discharge process may remain. The positive electrode 64 includes a positive electrode current collector 62 and a positive electrode mixture layer 66 including at least a positive electrode active material formed on the surface of the positive electrode current collector 62. The negative electrode 84 includes a negative electrode current collector 82 and a negative electrode mixture layer 86 including at least a negative electrode active material formed on the surface of the negative electrode current collector 82. The negative electrode mixture layer 86 can include CMC-Ca and CMC. The concentration of calcium oxalate in the non-aqueous electrolyte is at least 0.01 mol / L (for example, 0.01 mol / L to 0.08 mol / L, preferably 0.04 mol / L to 0.08 mol / L). Yes.)

Calcium oxalate contained in the non-aqueous electrolyte is oxalic acid produced by reductive decomposition of calcium ions released from CMC-Ca contained in the negative electrode mixture layer 86 and BP-oxalato compound in the initial charging step S40. It is produced by reaction with ions. Since oxalate ions react with calcium ions and exist as calcium oxalate, reductive decomposition of oxalate ions does not occur even when charging and discharging are performed, and generation of CO and CO ₂ is prevented. For this reason, the rise in the internal pressure of the battery case 15 is suppressed, and deformation of the shape (particularly the shape in the thickness direction) of the battery case 15 is prevented. Moreover, since the film containing at least one of phosphorus and boron is formed in a preferable mode on the surface of the negative electrode active material, the lithium ion secondary battery 10 exhibits excellent battery characteristics. The amount of phosphorus (P) or boron (B) contained in the coating can be grasped by analyzing the coating by ICP (high frequency inductively coupled plasma) emission analysis, ion chromatography or the like.

Next, an example of an assembled battery (typically an assembled battery in which a plurality of single cells are connected in series) 200 including the lithium ion secondary battery 10 as a single battery and a plurality of the single batteries will be described. . In the unit cell 10 according to the present embodiment, since the deformation of the battery case 15 (particularly the shape in the thickness direction) due to the generation of gas is prevented, the assembled battery 200 is stabilized with a preset binding force. Can be built.
As shown in FIG. 4, the assembled battery 200 includes a plurality of (typically 10 or more, preferably about 40 to 80, for example, 50) lithium ion secondary batteries (unit cells) 10 respectively. The wide surfaces of the battery case 15 are arranged in the facing direction (stacking direction) while being inverted one by one so that the positive electrode terminals 60 and the negative electrode terminals 80 are alternately arranged. A cooling plate 110 having a predetermined shape is sandwiched between the arranged cells 10. The cooling plate 110 functions as a heat dissipating member for efficiently dissipating the heat generated in each unit cell 10 during use, and preferably a cooling fluid (typically air) between the unit cells 10. ) (For example, a shape in which a plurality of parallel grooves extending vertically from one side of the rectangular cooling plate to the opposite side are provided on the surface). A cooling plate made of metal having good thermal conductivity or lightweight and hard polypropylene or other synthetic resin is suitable.

  A pair of end plates (restraint plates) 120 and 120 are disposed at both ends of the unit cell 10 and the cooling plate 110 arranged as described above. One or a plurality of sheet-like spacer members 150 as length adjusting means may be sandwiched between the cooling plate 110 and the end plate 120. The unit cell 10, the cooling plate 110, and the spacer member 150 arranged above have a predetermined restraining pressure in the stacking direction by a tightening restraining band 130 attached so as to bridge between the end plates 120, 120. Restrained to join. More specifically, by tightening and fixing the end portion of the restraining band 130 to the end plate 120 with screws 155, the unit cells and the like are restrained so that a predetermined restraining pressure is applied in the arrangement direction. Thereby, restraint pressure is also applied to the wound electrode body 50 housed in the battery case 15 of each unit cell 10. In the unit cell 10 of the present embodiment, since the deformation of the battery case 15 is prevented, substantially the same restraining pressure is applied to each unit cell 10. In addition, between the adjacent unit cells 10, one positive electrode terminal 60 and the other negative electrode terminal 80 are electrically connected by a connecting member (bus bar) 140. Thus, the assembled battery 200 of the desired voltage is constructed | assembled by connecting each cell 10 in series.

  EXAMPLES Examples relating to the present invention will be described below, but the present invention is not intended to be limited to those shown in the examples.

[Test Example 1]
<Example 1>
[Preparation of positive electrode]
The mass ratio of LiNi _1/3 Co _1/3 Mn _1/3 O ₂ as the positive electrode active material, acetylene black (AB) as the conductive material, and PVDF as the binder is 90: 8: 2. Thus, these materials were dispersed in NMP to prepare a paste-like composition for forming a positive electrode mixture layer. The composition was applied to a positive electrode current collector (aluminum foil) having a thickness of 15 μm at a coating amount of 25 mg / cm ² per side and dried, and then subjected to a press treatment so that the mixture density was on the positive electrode current collector. A sheet-like positive electrode A on which a positive electrode mixture layer of 2.8 g / cm ³ was formed was produced.

[Preparation of negative electrode]
Weigh natural graphite, SBR as a binder, and CMC-Ca as a thickener so that the mass ratio is 98.7: 0.3: 1, and disperse these materials in ion-exchanged water. Thus, a paste-like composition for forming a negative electrode mixture layer was prepared. The composition was applied to a negative electrode current collector (copper foil) having a thickness of 10 μm and coated at a coating amount of 20 mg / cm ² on one side and dried, and then subjected to a press treatment so that the mixture density was 1 on the negative electrode current collector. A sheet-like negative electrode A on which a 4 g / cm ³ negative electrode mixture layer was formed was produced.

[Preparation of separator]
A three-layer separator A in which a porous polypropylene layer was formed on both sides of a porous polyethylene layer was prepared. The thickness of the separator A was 20 μm.

[Production of lithium ion secondary battery (non-aqueous electrolyte secondary battery)]
A separator A was interposed between the prepared positive electrode A and negative electrode A and wound in an elliptical shape to produce a wound electrode body according to Example 1. Electrode terminals are joined to the ends of the positive and negative electrode current collectors of the wound electrode body, and the wound electrode body is placed in an aluminum battery case having a length of 75 mm, a width of 120 mm, a thickness of 15 mm, and a case thickness of 1 mm. Accommodated. Subsequently, the non-aqueous electrolyte solution according to Example 1 was injected into the battery case to produce an assembly according to Example 1. The non-aqueous electrolyte according to Example 1 is a non-aqueous solvent having a volume ratio of EC, DMC, and EMC of 3: 4: 3, LiPF ₂ (C ₂ O ₄ ) ₂ as an additive, and LiPF ₆ as a supporting salt. Used was dissolved. The concentration of LiPF ₂ (C ₂ O ₄ ) _{2 in} the non-aqueous electrolyte according to Example 1 was 0.0125 mol / L, and the concentration of LiPF ₆ was 1 mol / L. After the injection, the assembly according to Example 1 was charged and discharged for the first time. That is, under a temperature condition of 25 ° C., charging is performed at a constant current and a constant voltage up to 4.1 V at a charging rate of 1 C (4 A), and after a pause of 10 minutes, discharging is performed at a constant current up to 3 V at a discharging rate of 1 C (4 A). And paused for 10 minutes. In this way, it provided with a negative electrode on the surface of the anode active material _{LiPF 2 (C 2 O 4)} 2 derived from coating formed, thereby producing a lithium ion secondary battery according to Example 1.

<Example 2 to Example 20>
Example 1 except that the concentration of LiPF ₂ (C ₂ O ₄ ) _{2 in} the non-aqueous electrolyte injected into the battery case and the content of CMC-Ca contained in the negative electrode mixture layer were changed to those shown in Table 1 In the same manner, the assemblies and lithium ion secondary batteries according to Examples 2 to 20 were produced.

<Example 21 to Example 22>
Example 1 except that the concentration of LiPF ₂ (C ₂ O ₄ ) _{2 in} the non-aqueous electrolyte injected into the battery case and the content of CMC-Na contained in the negative electrode mixture layer were changed to those shown in Table 1 In the same manner, the assemblies and lithium ion secondary batteries according to Examples 21 to 22 were produced.

[Measurement of gas generation amount]
About the assembly concerning the produced Examples 1 to 22, the volume of each assembly was measured by Archimedes method. Then, the volume of the battery was measured by the Archimedes method for the lithium ion secondary batteries according to Examples 1 to 22 after the first charge / discharge. Then, the volume B [mL] of the assembly according to each example is subtracted from the volume A [mL] of the lithium ion secondary battery according to each example after the initial charge / discharge, respectively, and the amount of gas generated after the initial charge / discharge ( AB) [mL] was calculated. The measurement results are shown in Table 1. Moreover, the relationship between the gas generation amount [mL] after the first charge / discharge and the gas adsorbent [mmol / g] is shown in FIG. In the Archimedes method, a measurement object (in this example, an assembly and a lithium ion secondary battery) is immersed in a liquid medium (for example, distilled water or alcohol), and the buoyancy that the measurement object receives is measured. This is a method for obtaining the volume of the measurement object.

As shown in Table 1 and FIG. 6, it was confirmed that the amount of gas (typically CO and CO ₂ ) generated was reduced by adding CMC-Ca as a thickener in the negative electrode mixture layer. (See Example 8 and Example 21, Example 18 and Example 22). That is, it was confirmed that the increase in the internal pressure of the battery case was suppressed by adding CMC-Ca to the negative electrode mixture layer. This is because calcium ions are liberated from the CMC-Ca contained in the negative electrode composite layer into the non-aqueous electrolyte, and calcium oxalate is produced by the reaction between the liberated calcium ions and oxalate ions. This is because the generation of carbon monoxide and carbon dioxide based on the decomposition of acid ions is suppressed. When the total solid content of the negative electrode mixture layer is 100% by mass, the amount of gas generated is greatly reduced when the content of CMC-Ca contained in the negative electrode mixture layer is 0.5% by mass or more. Was confirmed.

In addition, in a battery including the above aluminum battery case, when the amount of gas generated exceeds 2.2 mL, the shape of the battery case (particularly the shape in the thickness direction) is deformed, and a plurality of the batteries are set in advance. It was difficult to construct an assembled battery with the restraining force. For this reason, the concentration of LiPF ₂ (C ₂ O ₄ ) _{2 in} the non-aqueous electrolyte injected into the aluminum battery case needs to be 0.02 mol / L or less. However, by adding CMC-Ca into the negative electrode mixture layer, the concentration of LiPF ₂ (C ₂ O ₄ ) _{2 in} the non-aqueous electrolyte injected into the battery case was made higher than 0.02 mol / L. Even in the case (for example, 0.05 mol / L), it was confirmed that only a small amount of gas was present in the battery case, and the increase in the internal pressure of the battery case could be suppressed.

[Test Example 2]
<Example 23 to Example 28>
When the total solid content of the negative electrode mixture layer is 100% by mass, the content of CMC-Ca contained in the negative electrode mixture layer is 0.5% by mass or more, and the concentration of LiPF ₂ (C ₂ O ₄ ) ₂ is Lithium ion secondary batteries according to Examples 23 to 28 were produced in the same manner as Example 1 except that the lithium ion secondary batteries were changed to those shown in Table 2. Note that LiPF ₂ (C ₂ O ₄ ) ₂ was not added to the nonaqueous electrolytic solution according to Example 28.

[Initial reaction resistance measurement]
The lithium ion secondary batteries according to Examples 23 to 28 manufactured as described above were subjected to an appropriate conditioning treatment at a temperature of 25 ° C. (constant current and constant voltage up to 4.1 V at a charging rate of 0.1 C). After performing an operation of charging and an operation of repeating a constant current and a constant voltage discharge to 3.0 V at a discharge rate of 0.1 C three times), the state of charge was adjusted to 40% SOC. And AC impedance measurement was performed at a frequency of 0.001 Hz to 100,000 Hz on a temperature condition of −30 ° C. with respect to the lithium ion secondary batteries of Examples 23 to 28, and the obtained Cole-Cole plot was 0.01 Hz to The diameter of an arc (semicircle) at 30 Hz was measured, and the value was defined as the initial reaction resistance [Ω]. The obtained resistance values are shown in Table 2 and FIG.

[Measurement of reaction resistance after storage]
About the lithium ion secondary battery which concerns on Example 23-Example 28 after measuring the said initial stage reaction resistance, after adjusting to SOC90%, it preserve | saved for 30 days under 60 degreeC temperature conditions. After the lithium ion secondary batteries according to Examples 23 to 28 after storage were adjusted to SOC 40%, AC impedance was measured at a frequency of 0.001 Hz to 100,000 Hz under a temperature condition of −30 ° C., and the obtained Cole− The diameter of an arc (semicircle) at 0.01 Hz to 30 Hz in the Cole plot was measured, and the value was defined as reaction resistance [Ω] after storage. The obtained resistance values are shown in Table 2 and FIG.

[Capacity maintenance rate measurement]
About the lithium ion secondary battery which concerns on the said Example 23-Example 28, the capacity | capacitance maintenance factor [%] after preserve | saving for 30 days on 60 degreeC temperature conditions was measured. First, under the temperature condition of 25 ° C., the lithium ion secondary batteries according to Examples 23 to 28 were subjected to constant current and constant voltage for 3 hours to 4.1 V at a charge rate of 1 C, and rested for 10 minutes. Next, constant current discharge was performed for 6 hours to 3 V at a discharge rate of 1/3 C, and rested for 10 minutes. Further, constant current and constant voltage discharge was performed for 4 hours to 3 V at a discharge rate of 1/3 C, and rested for 10 minutes. The capacity obtained at this time was defined as the initial battery capacity. Next, each lithium ion secondary battery whose initial battery capacity was measured was adjusted to SOC 90% and then stored for 30 days under a temperature condition of 60 ° C. For the lithium ion secondary batteries according to Examples 23 to 28 after storage, the battery capacity after storage (battery capacity after storage) was measured by the same method as the method for measuring the initial battery capacity. Here, the following formula: {(battery capacity after storage) / (initial battery capacity)} × 100 was defined as the capacity retention rate [%] after 30 days storage. The measurement results are shown in Table 2 and FIG.

As shown in Table 2 and FIG. 7, regarding the initial reaction resistance, when the concentration of LiPF ₂ (C ₂ O ₄ ) ₂ contained in the nonaqueous electrolytic solution is 0.02 mol / L to 0.04 mol / L. It was confirmed to show a low value. As for the after storage reaction resistance, non-aqueous concentration of _{LiPF 2 (C 2 O 4)} 2 contained in the electrolytic solution was found to exhibit a low value in case of more than 0.02 mol. Further, as shown in Table 2 and FIG. 8, for the capacity retention rate, the _{LiPF 2 (C 2 O 4)} 2 contained in the nonaqueous electrolytic solution concentration of 0.02mol / L~0.04mol / L It was confirmed that the case shows a high value. From the above, it was confirmed that high battery performance was exhibited when the concentration of LiPF ₂ (C ₂ O ₄ ) ₂ contained in the non-aqueous electrolyte was 0.02 mol / L to 0.04 mol / L.

  As mentioned above, although the specific example of this invention was demonstrated in detail, these are only illustrations and do not limit a claim. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

  The non-aqueous electrolyte secondary battery obtained by the manufacturing method according to the present invention realizes a reduction in battery resistance and a highly reliable battery that ensures a sufficient amount of gas generation when the pressure in the battery case increases. Therefore, it can be suitably used as a driving power source mounted on a vehicle such as an automobile. Therefore, as schematically shown in FIG. 5, the present invention provides a vehicle (as a power source) having such a nonaqueous electrolyte secondary battery 10 (typically, a battery pack 200 formed by connecting a plurality of such batteries 10 in series). A vehicle, typically a vehicle with a motor such as a hybrid vehicle, an electric vehicle, a fuel vehicle) 100 is provided.

10 Lithium ion secondary battery (non-aqueous electrolyte secondary battery)
15 Battery Case 20 Opening 25 Lid 30 Case Body 31 Current Cutoff Mechanism 40 Safety Valve 45 Inlet 48 Sealing Plug 50 Winding Electrode Body 60 Positive Electrode Terminal 62 Positive Electrode Current Collector 63 Positive Electrode Mixing Layer Non-Forming Portion 64 Positive Electrode 66 Positive Electrode Composite material layer 70 Assembly 80 Negative electrode terminal 82 Negative electrode current collector 83 Negative electrode composite material layer non-formed portion 84 Negative electrode 86 Negative electrode composite material layer 90 Separator 100 Vehicle (automobile)
200 batteries

Claims (14)

A non-aqueous electrolyte secondary battery,
An electrode body having a positive electrode and a negative electrode, a non-aqueous electrolyte, and a battery case containing the electrode body and the non-aqueous electrolyte,
The positive electrode has a positive electrode mixture layer containing at least a positive electrode active material,
The negative electrode has a negative electrode mixture layer containing at least a negative electrode active material,
At least one of the positive electrode mixture layer and the negative electrode mixture layer includes a calcium salt of carboxymethyl cellulose,
A film containing at least one of phosphorus and boron is formed on the surface of the negative electrode active material,
The non-aqueous electrolyte solution is a non-aqueous electrolyte secondary battery containing calcium oxalate. The calcium salt of the carboxymethyl cellulose is included in the negative electrode mixture layer,
When the total solid content of the negative electrode mixture layer is 100% by mass, the content of the calcium salt of the carboxymethyl cellulose contained in the negative electrode mixture layer is 0.5% by mass or more and 1.2% by mass or less. The non-aqueous electrolyte secondary battery according to claim 1.   The nonaqueous electrolyte secondary battery according to claim 1 or 2, wherein the concentration of the calcium oxalate is at least 0.01 mol / L.   4. The non-aqueous electrolyte secondary battery according to claim 1, wherein the non-aqueous electrolyte further includes an oxalato complex compound containing at least one of phosphorus and boron as a constituent element. 5. The non-aqueous electrolyte further includes a gas generating agent capable of decomposing and generating gas when exceeding a predetermined battery voltage,
The non-aqueous electrolyte secondary according to any one of claims 1 to 4, wherein the battery case includes a current interruption mechanism that operates when the pressure in the battery case increases with the generation of the gas. battery. A method of manufacturing a non-aqueous electrolyte secondary battery,
Preparing a positive electrode having a positive electrode mixture layer containing at least a positive electrode active material and a negative electrode having a negative electrode mixture layer containing at least a negative electrode active material, wherein at least one of the prepared positive electrode mixture layer and the negative electrode mixture layer One comprises a calcium salt of carboxymethylcellulose;
Producing an electrode body using the prepared positive and negative electrodes,
Housing the electrode body in a battery case, and injecting a non-aqueous electrolyte containing an oxalato complex compound containing at least one of phosphorus and boron into the battery case to produce an assembly;
Performing initial charging to a predetermined charging voltage for the assembly;
A method for producing a non-aqueous electrolyte secondary battery.   When the total solid content of the negative electrode mixture layer is 100% by mass, the calcium salt content of the carboxymethylcellulose contained in the negative electrode mixture layer is 0.5% by mass or more and 1.2% by mass or less. The manufacturing method according to claim 6, wherein the negative electrode mixture layer contains the calcium salt of carboxymethyl cellulose.   The manufacturing method according to claim 6 or 7, wherein the concentration of the oxalato complex compound is 0.02 mol / L to 0.04 mol / L. The production method according to any one of claims 6 to 8, wherein LiPF ₂ (C ₂ O ₄ ) ₂ is used as the oxalato complex compound. A non-aqueous electrolyte secondary battery assembly before initial charging, comprising: an electrode body having a positive electrode and a negative electrode; a non-aqueous electrolyte; and a battery case containing the electrode body and the non-aqueous electrolyte. ,
The positive electrode has a positive electrode mixture layer containing at least a positive electrode active material,
The negative electrode has a negative electrode mixture layer containing at least a negative electrode active material,
At least one of the positive electrode mixture layer and the negative electrode mixture layer includes a calcium salt of carboxymethyl cellulose,
The non-aqueous electrolyte secondary battery assembly includes an oxalato complex compound containing at least one of phosphorus and boron as a constituent element. The calcium salt of the carboxymethyl cellulose is included in the negative electrode mixture layer,
When the total solid content of the negative electrode mixture layer is 100% by mass, the content of the calcium salt of the carboxymethyl cellulose contained in the negative electrode mixture layer is 0.5% by mass or more and 1.2% by mass or less. The non-aqueous electrolyte secondary battery assembly according to claim 10.   The non-aqueous electrolyte secondary battery assembly according to claim 10 or 11, wherein the concentration of the oxalato complex compound in the non-aqueous electrolyte is 0.02 mol / L to 0.04 mol / L. The non-aqueous electrolyte secondary battery assembly according to any one of claims 10 to 12, wherein the oxalato complex compound is LiPF ₂ (C ₂ O ₄ ) ₂ . The non-aqueous electrolyte further includes a gas generating agent capable of decomposing and generating gas when exceeding a predetermined battery voltage,
The non-aqueous electrolyte secondary according to any one of claims 10 to 13, wherein the battery case includes a current interrupting mechanism that operates when a pressure in the battery case increases as the gas is generated. Battery assembly.

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