JP7177990B2 - lithium ion secondary battery - Google Patents

Description

The present invention relates to non-aqueous electrolyte secondary batteries.

In recent years, non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries have been used as portable power sources for personal computers and mobile terminals, and for driving vehicles such as electric vehicles (EV), hybrid vehicles (HV), and plug-in hybrid vehicles (PHV). It is suitable for use as a power source for electric appliances.

A positive electrode of a non-aqueous electrolyte secondary battery generally has a structure in which a positive electrode active material layer is provided on a positive electrode current collector. Further, the positive electrode generally has a portion where the positive electrode current collector is exposed without the positive electrode active material layer being provided for the purpose of current collection. In order to suppress a short circuit between the positive electrode and the negative electrode, there is known a technique of providing an insulating layer at the boundary between the exposed portion of the positive electrode current collector and the positive electrode active material layer (see, for example, Patent Document 1).

Patent Literature 1 describes that the end portion of the positive electrode active material layer has a tapered region in which the thickness gradually decreases, and the insulating layer partially overlaps the tapered region. And, in Patent Document 1, the taper angle (that is, the inner angle of the wedge shape in the cross section perpendicular to the edge of the positive electrode active material layer, or the interface between the positive electrode active material layer and the insulating layer, and the main surface of the positive electrode current collector) angle on the side of the positive electrode active material layer) is preferably 45 degrees or less.

JP 2012-114079 A

However, as a result of intensive studies by the present inventors, the following facts were found.
When the end portion of the positive electrode active material layer has a tapered region, the taper angle is preferably large from the viewpoint of battery capacity and battery resistance. On the other hand, as the non-aqueous electrolyte secondary battery is charged and discharged, the positive electrode active material expands/contracts. Therefore, stress is generated at the interface between the positive electrode active material layer and the insulating layer, and propagates to the interface between the insulating layer and the positive electrode current collector. This stress increases when the taper angle is large. When charging and discharging are repeated, the peel strength between the insulating layer and the positive electrode current collector is reduced due to the repeated stress. As a result, when the non-aqueous electrolyte secondary battery is subjected to external deformation force, the interface between the insulating layer and the positive electrode current collector is likely to be exposed. If a short circuit occurs at the exposed portion of the interface due to entry of foreign matter or the like, there is a problem that the temperature rises significantly.

Therefore, the present invention has a high capacity and low resistance, and suppresses temperature rise due to short circuiting at the exposed portion of the interface between the insulating layer provided on the positive electrode current collector and the positive electrode current collector. An object of the present invention is to provide a non-aqueous electrolyte secondary battery.

A non-aqueous electrolyte secondary battery disclosed herein includes a positive electrode, a negative electrode, and a non-aqueous electrolyte. The positive electrode includes a positive electrode current collector, a positive electrode active material layer, and an insulating layer. The positive electrode current collector has at least one end portion where the positive electrode current collector is exposed. The insulating layer is located at the boundary between the positive electrode active material layer and the exposed portion of the positive electrode current collector. The angle formed by the main surface of the positive electrode current collector and the interface between the positive electrode active material layer and the insulating layer on the side of the positive electrode active material layer is 45 degrees or more and 90 degrees or less. The peel strength between the positive electrode current collector and the insulating layer is greater than the peel strength between the positive electrode current collector and the positive electrode active material layer. The volume density of the positive electrode active material layer is 2.4 g/cm ³ or more and 3.5 g/cm ³ or less.
According to such a configuration, high capacity and low resistance are obtained, and temperature rise due to occurrence of short circuit at the exposed portion of the interface between the insulating layer provided on the positive electrode current collector and the positive electrode current collector is suppressed. A non-aqueous electrolyte secondary battery is provided,

1 is a cross-sectional view schematically showing the internal structure of a lithium ion secondary battery according to one embodiment of the present invention; FIG. 1 is a schematic diagram showing the configuration of a wound electrode body of a lithium ion secondary battery according to one embodiment of the present invention; FIG. 1 is a schematic cross-sectional view of a positive electrode of a lithium ion secondary battery according to one embodiment of the present invention; FIG. 4 is an enlarged view of the inside of the square frame A in FIG. 3; FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments according to the present invention will be described below. In addition, matters other than matters specifically mentioned in this specification and necessary for the implementation of the present invention (for example, the general configuration and manufacturing process of a non-aqueous electrolyte secondary battery that does not characterize the present invention) can be grasped as a design matter of a person skilled in the art based on the prior art in the field. The present invention can be implemented based on the contents disclosed in this specification and common general technical knowledge in the field.

As used herein , the term "lithium ion secondary battery" refers to a secondary battery that utilizes lithium ions as charge carriers and that is charged and discharged by charge transfer associated with the lithium ions between the positive and negative electrodes.
Hereinafter, the present invention will be described in detail using a flat prismatic lithium ion secondary battery as an example, but the present invention is not intended to be limited to those described in the embodiments.

The lithium ion secondary battery 100 shown in FIG. 1 is a closed type constructed by housing a flat wound electrode body 20 and a non-aqueous electrolyte 80 in a flat rectangular battery case (that is, an outer container) 30. Battery. The battery case 30 is provided with a positive terminal 42 and a negative terminal 44 for external connection, and a thin safety valve 36 set to release the internal pressure when the internal pressure of the battery case 30 rises above a predetermined level. ing. Further, the battery case 30 is provided with an injection port (not shown) for injecting the non-aqueous electrolyte 80 . The positive terminal 42 is electrically connected to the positive collector plate 42a. The negative terminal 44 is electrically connected to the negative collector plate 44a. As the material of the battery case 30, for example, a metal material such as aluminum that is lightweight and has good thermal conductivity is used.

As shown in FIGS. 1 and 2, the wound electrode body 20 is formed by stacking a long positive electrode sheet 50 and a long negative electrode sheet 60 with two long separator sheets 70 interposed therebetween. It has a configuration in which it is wound in the longitudinal direction.

The positive electrode sheet 50 has, as shown in FIGS. 2 and 3 , an elongated positive electrode current collector 52 and a positive electrode active material layer 54 formed on the positive electrode current collector 52 . In the illustrated example, the positive electrode active material layer 54 is provided on both sides of the positive electrode current collector 52, but may be provided on one side. Further, the positive electrode current collector 52 has a portion (positive electrode current collector exposed portion) 52a where the positive electrode current collector 52 is exposed without the positive electrode active material layer 54 being formed. As shown in FIG. 2, the positive electrode current collector exposed portion 52a is formed so as to protrude outward from one end of the wound electrode assembly 20 in the winding axial direction (that is, in the sheet width direction orthogonal to the longitudinal direction). there is The positive electrode sheet 50 also includes an insulating layer 56 formed on the positive electrode current collector 52 . The insulating layer 56 is adjacent to the positive electrode active material layer 54 and positioned between the positive electrode active material layer 54 and the positive electrode current collector exposed portion 52 a in the surface direction of the positive electrode sheet 50 . In other words, the insulating layer 56 is located at the boundary between the positive electrode active material layer 54 and the positive electrode current collector exposed portion 52a. In the illustrated example, the insulating layer 56 is provided on both sides of the positive electrode current collector 52, but may be provided on one side. As shown in FIG. 2, the positive electrode current collector plate 42a is joined to the positive electrode current collector exposed portion 52a.

Examples of the positive electrode current collector 52 forming the positive electrode sheet 50 include aluminum foil.
The positive electrode active material layer 54 contains a positive electrode active material. Examples of positive electrode active materials include lithium transition metal oxides (eg, LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiNiO ₂ , LiCoO ₂ , LiFeO ₂ , LiMn ₂ O ₄ , LiNi _0.5 Mn _{1 .5O4} , etc.), lithium transition metal phosphate compounds ₍ eg, _LiFePO4 , etc.), and the like. The positive electrode active material layer 54 may contain components other than the active material, such as a conductive material, a binder, lithium phosphate, and the like. Carbon black such as acetylene black (AB) and other carbon materials (eg, graphite) can be suitably used as the conductive material. As the binder, for example, polyvinylidene fluoride (PVDF) or the like can be used.

The insulating layer 56 typically contains an inorganic filler and a binder.
The shape of the inorganic filler is not particularly limited, and may be particulate, fibrous, plate-like, flake-like, or the like.
The average particle size of the inorganic filler is not particularly limited, and is, for example, 0.01 μm or more and 10 μm or less, preferably 0.1 μm or more and 5 μm or less, more preferably 0.2 μm or more and 2 μm or less. In addition, the average particle size of the inorganic filler can be obtained by, for example, a laser diffraction scattering method.
As the inorganic filler, one having insulating properties is used. Specifically, for example, inorganic oxides such as alumina (Al ₂ O ₃ ), magnesia (MgO), silica (SiO ₂ ), titania (TiO ₂ ), nitrides, etc. Nitrides such as aluminum and silicon nitride, metal hydroxides such as calcium hydroxide, magnesium hydroxide and aluminum hydroxide, mica, talc, boehmite, zeolite, apatite, clay minerals such as kaolin, and glass fibers. These can be used alone or in combination of two or more. Among them, alumina, boehmite and magnesia are preferred.
Examples of binders include acrylic binders, styrene-butadiene rubber (SBR), polyolefin binders, and the like. Fluoropolymers such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE) can also be used.
The content of the binder in the insulating layer 56 is not particularly limited, but is, for example, 1% by mass or more and 30% by mass or less, preferably 3% by mass or more and 25% by mass or less.

In the present embodiment, the angle formed by the main surface of the positive electrode current collector 52 and the interface between the positive electrode active material layer 54 and the insulating layer 56 on the positive electrode active material layer 54 side is 45 degrees or more and 90 degrees or less. FIG. 4 is an enlarged view of the square frame A of FIG. Therefore, in FIG. 4 , this angle can be expressed as an angle θ on the side of the positive electrode active material layer 54 formed by the boundary line 58 between the positive electrode active material layer 54 and the insulating layer 56 and the positive electrode current collector 52 . If the boundary line 58 is not a straight line, it is preferable to obtain the angle θ by linear approximation. Therefore, if the boundary surface is not a plane, plane approximation should be performed to obtain the above angle.
When the angle θ is 45 degrees or more and 90 degrees or less, the lithium secondary battery 100 has a high capacity and a low resistance. The angle θ is preferably 45 degrees or more and 75 degrees or less, more preferably 50 degrees or more and 70 degrees or less.
The method for producing a positive electrode with a large angle θ is not particularly limited, but the paste for forming the positive electrode active material layer and the paste for forming the insulating layer are simultaneously coated by a die coater or the like, and dried. A simple method is to form the positive electrode active material layer and the insulating layer at the same time. At this time, the angle θ can be further adjusted to some extent by adjusting the solid content concentration, viscosity, etc. of the paste for forming the positive electrode active material layer and the paste for forming the insulating layer.

In this embodiment, the peel strength between the positive electrode current collector 52 and the insulating layer 56 is greater than the peel strength between the positive electrode current collector 52 and the positive electrode active material layer 54 .
Since stress is generated by expansion/contraction of the positive electrode active material during charge/discharge, the stress is applied from the positive electrode active material layer 54 to the insulating layer 56 . By making the peel strength between the insulating layer 56 and the positive electrode current collector 52 that receive stress greater than the peel strength between the positive electrode active material layer 54 that generates stress and the positive electrode current collector 52, the positive electrode collector Separation between the conductor 52 and the insulating layer 56 can be suppressed. Therefore, the interface between the insulating layer 56 and the positive electrode current collector 52 is less likely to be exposed, and temperature rise due to a short circuit at the exposed portion of the interface can be suppressed.
The method for controlling the peel strength between the positive electrode current collector 52 and the insulating layer 56 is not particularly limited. be able to. As for the method for controlling the peel strength between the positive electrode current collector 52 and the positive electrode active material layer 54 , the peel strength can be easily controlled by the type and amount of the binder used for the positive electrode active material layer 54 . Therefore, the binder content (mass %) in the insulating layer 56 is preferably higher than the binder content (mass %) in the positive electrode active material layer 54 .

In this embodiment, the volume density of the positive electrode active material layer 54 is 2.4 g/cm ³ or more and 3.5 g/cm ³ or less. If the volume density is less than 2.4 g/cm ³ , the inorganic filler contained in the insulating layer 56 penetrates into the positive electrode active material layer 54 when the positive electrode active material layer 54 and the insulating layer 56 are formed, thereby increasing the battery resistance. Become. ^On the other hand, the voids in the positive electrode active material layer 54 partially absorb the stress due to the expansion/contraction of the positive electrode active material. The absorption effect is reduced and the stress applied to the insulating layer 56 becomes excessively large. As a result, the interface between the insulating layer 56 and the positive electrode current collector 52 is exfoliated and exposed due to excessive stress, and a short circuit at the exposed portion causes a temperature rise.

The negative electrode sheet 60 has, as shown in FIG. 2 , an elongated negative electrode current collector 62 and a negative electrode active material layer 64 formed on the negative electrode current collector 62 . In the illustrated example, the negative electrode active material layer 64 is provided on both sides of the negative electrode current collector 62, but may be provided on one side. Further, the negative electrode current collector 62 has a portion (negative electrode current collector exposed portion) 62a where the negative electrode current collector 62 is exposed without the negative electrode active material layer 64 being formed. The negative electrode current collector exposed portion 62a is formed to protrude outward from the other end of the wound electrode body 20 in the winding axial direction (that is, the sheet width direction orthogonal to the longitudinal direction). A negative electrode collector plate 44a is joined to the negative electrode collector exposed portion 62a.

Examples of the negative electrode current collector 62 forming the negative electrode sheet 60 include copper foil. As the negative electrode active material contained in the negative electrode active material layer 64, for example, a carbon material such as graphite, hard carbon, or soft carbon can be used. The negative electrode active material layer 64 may contain components other than the active material, such as binders and thickeners. As the binder, for example, styrene-butadiene rubber (SBR) or the like can be used. As a thickening agent, for example, carboxymethyl cellulose (CMC) or the like can be used.

Examples of the separator 70 include porous sheets (films) made of resin such as polyethylene (PE), polypropylene (PP), polyester, cellulose, and polyamide. Such a porous sheet may have a single-layer structure or a laminated structure of two or more layers (for example, a three-layer structure in which PP layers are laminated on both sides of a PE layer). A heat-resistant layer (HRL) may be provided on the surface of the separator 70 .

In this embodiment, a non-aqueous electrolyte is used as the non-aqueous electrolyte 80 . Non-aqueous electrolyte 80 typically contains a non-aqueous solvent and a supporting electrolyte.
As the non-aqueous solvent, organic solvents such as various carbonates, ethers, esters, nitriles, sulfones, lactones, etc., which are used in electrolytes of general lithium ion secondary batteries, can be used without particular limitation. can be done. Among them, carbonates are preferable, and specific examples thereof include ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), monofluoroethylene carbonate ( MFEC), difluoroethylene carbonate (DFEC), monofluoromethyldifluoromethyl carbonate (F-DMC), trifluorodimethyl carbonate (TFDMC) and the like. Such non-aqueous solvents can be used singly or in combination of two or more.
Lithium salts such as LiPF ₆ , LiBF ₄ and LiClO ₄ (preferably LiPF ₆ ) can be suitably used as the supporting salt. The concentration of the supporting salt is preferably 0.7 mol/L or more and 1.3 mol/L or less.

The non-aqueous electrolyte 80 includes, for example, a gas generating agent such as biphenyl (BP) and cyclohexylbenzene (CHB); an oxalato complex compound containing a boron atom and/or a phosphorus atom; , film-forming agents such as vinylene carbonate (VC); dispersants; and various additives such as thickeners.

As described above, the angle θ between the main surface of the positive electrode current collector 52 and the boundary surface between the insulating layer 56 and the positive electrode current collector 52 is 45 degrees or more and 90 degrees or less, and the positive electrode current collector 52 is insulated. 3. The peel strength between the layer 56 is greater than the peel strength between the positive electrode current collector 52 and the positive electrode active material layer 54, and the volume density of the positive electrode active material layer 54 is 2.4 g/cm ³ or more. The combination of the configuration of 5 g/cm ³ or less provides high capacity and low resistance, and the occurrence of short circuits at the exposed portion of the interface between the insulating layer provided on the positive electrode current collector and the positive electrode current collector. Provided is a lithium-ion secondary battery 100 in which temperature rise due to is suppressed.

The lithium ion secondary battery 100 can be used for various purposes. Suitable applications include drive power supplies mounted in vehicles such as electric vehicles (EV), hybrid vehicles (HV), and plug-in hybrid vehicles (PHV). The lithium ion secondary battery 100 can also be used typically in the form of an assembled battery in which a plurality of batteries are connected in series and/or in parallel.

As an example, the prismatic lithium ion secondary battery 100 including the flattened wound electrode body 20 has been described. However, the lithium ion secondary battery can also be configured as a lithium ion secondary battery with a laminated electrode body. Also, the lithium ion secondary battery can be configured as a cylindrical lithium ion secondary battery, a laminated lithium ion secondary battery, or the like. In addition, the technology disclosed herein can also be applied to non-aqueous electrolyte secondary batteries other than lithium ion secondary batteries.

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.

<Production of Lithium Ion Secondary Batteries of Examples and Comparative Examples>
A dispersing machine was used to obtain a paste in which acetylene black (AB), polyvinylidene fluoride (PVdF) and N-methyl-2-pyrrolidone (NMP) were mixed as conductive materials. After adding a mixed powder of LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (LNCM) and Li ₃ PO ₄ as a positive electrode active material to this paste, the solid content was uniformly dispersed to form a positive electrode. A paste was prepared. The positive electrode mixture paste was prepared so that LNCM:Li ₃ PO ₄ :AB:PVdF=87:3:8:2 (mass ratio).
An insulating layer paste was prepared by mixing boehmite as an inorganic filler, PVdF as a binder, and NMP using a disperser.
This positive electrode paste was applied in strips on both sides of an elongated aluminum foil and dried to form a positive electrode active material layer. The positive electrode paste was applied along one end of the aluminum foil so as to form a current collector exposed portion where the positive electrode active material layer was not formed.
The insulating layer paste was applied along the portion adjacent to the positive electrode active material layer on the current collector exposed portion, and dried to form an insulating layer.
At this time, when the angle formed by the main surface of the positive electrode current collector and the boundary surface between the positive electrode active material layer and the insulating layer on the positive electrode active material layer side (hereinafter also referred to as “taper angle”) is large, the positive electrode paste and insulating layer paste were applied at the same time. For those with a small taper angle, a positive electrode paste was applied and dried to form a positive electrode active material layer, and then an insulating layer paste was applied and dried to form an insulating layer.
Also, the taper angle and the volume density of the positive electrode active material layer were adjusted by changing the solid content concentrations of the positive electrode paste and the insulating layer paste.
Further, compared to Comparative Examples 1-5, in Comparative Examples 6-13 and Examples 1-6, the amount of binder in the insulating layer paste was increased.
Thus, a positive electrode sheet having the configuration shown in FIG. 3 was produced.
Natural graphite (C) as a negative electrode active material, styrene-butadiene rubber (SBR) as a binder, and carboxymethyl cellulose (CMC) as a thickener were mixed at a mass ratio of C:SBR:CMC = 98:1:1. was mixed with ion-exchanged water to prepare a negative electrode paste. This negative electrode paste was applied in strips on both sides of a long copper foil, dried, and then pressed to prepare a negative electrode sheet.
A porous polyolefin sheet having a three-layer structure of PP/PE/PP was prepared as a separator.
A positive electrode sheet, a separator sheet, and a negative electrode sheet were laminated such that the separator was interposed between the positive electrode sheet and the negative electrode sheet to produce an electrode assembly. At this time, a Ni piece was placed between the insulating layer of the positive electrode sheet and the separator.
Next, terminals were attached to the electrode body and housed in a laminate case.
Subsequently, a non-aqueous electrolyte was injected into the laminate case, and the laminate case was hermetically sealed. The non-aqueous electrolyte includes a mixed solvent containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of EC:EMC:DMC=3:4:3, and a supporting salt. A solution in which LiPF ₆ was dissolved at a concentration of 1.0 mol/L was used.
Thus, a lithium ion secondary battery was produced.

<Taper angle measurement>
The positive electrode produced above was cut, and the cross section was observed with a scanning electron microscope (SEM). From the cross-sectional SEM image, the angle (taper angle) on the side of the positive electrode active material layer formed by the main surface of the positive electrode current collector and the boundary surface between the positive electrode active material layer and the insulating layer was obtained. Table 1 shows the results.

<Measurement of Volume Density of Positive Electrode Active Material Layer>
The positive electrode active material layer was cut into a predetermined size, its weight was determined, and the volume density (g/cm ³ ) was calculated. Table 1 shows the results.

<Peel strength measurement>
The peel strength was measured by a 90° peel test according to JIS Z 0237:2009 (testing method for adhesive tapes and adhesive sheets). Specifically, a test piece of the positive electrode active material layer portion and a test piece of the insulating layer portion were cut out from the positive electrode prepared above. The positive electrode active material layer or insulating layer of the test piece was fixed on a test stand, and the positive electrode current collector was pulled in the 90° direction using a 90° peeling tester (“SV-201-NA-50SL” manufactured by Imada Seisakusho). to measure the peel strength.
The peel strength of the test piece of the positive electrode active material layer portion (that is, the peel strength between the positive electrode active material layer and the positive electrode current collector) and the peel strength of the test piece of the insulating layer portion (that is, the insulating layer and the positive electrode current collector and peel strength) were compared. The layer with the higher peel strength is listed in Table 1.

<Resistance measurement>
After performing an activation process on the produced lithium ion secondary battery, the SOC was adjusted to 50%. This was placed in an environment of -10°C and discharged at a current value of 40A for 10 seconds. The voltage drop amount ΔV at this time was obtained, and the IV resistance was calculated using the current value and ΔV. Table 1 shows the results.

<Capacity measurement>
The lithium ion secondary battery produced above was placed in an environment at 25°C. Using a constant current-constant voltage method, each lithium secondary battery for evaluation was charged at a current value of 1/3C to 4.2V, and then charged at a constant voltage until the current value became 1/50C. Fully charged. After that, the lithium ion secondary battery was subjected to constant current discharge to 3.0 V at a current value of 1/3C. Then, the discharge capacity at this time was measured.
As a reference, a lithium ion secondary battery having no insulating layer was produced in the same manner as described above except that the insulating layer paste was not used, and the discharge capacity was measured in the same manner as described above.
The ratio of the discharge capacity of the lithium ion secondary battery of each example and each comparative example to the discharge capacity of the reference lithium ion secondary battery was determined in percentage. Table 1 shows the results.

<Evaluation of temperature rise due to short circuit>
Pulse charge/discharge was repeated with respect to the lithium ion secondary battery produced above. After that, a temperature sensor was attached to the laminate case. A short circuit was intentionally caused by applying pressure through the laminate case to the portion where the Ni piece was arranged. A temperature sensor was used to monitor the temperature of the lithium ion secondary battery, and the difference between the highest temperature reached and the temperature before the short circuit was obtained. Table 1 shows the results.

From the results in Table 1, the taper angle is 45 degrees or more and 90 degrees or less, and the peel strength between the positive electrode current collector and the insulating layer is higher than the peel strength between the positive electrode current collector and the positive electrode active material layer. It can be seen that when the volume density of the positive electrode active material layer is 2.4 g/cm ³ or more and 3.5 g/cm ³ or less, the resistance is small, the capacity is large, and the temperature rise at the time of short circuit is small.
From the above, according to the non-aqueous electrolyte secondary battery disclosed herein, high capacity and low resistance are obtained, and the interface between the insulating layer provided on the positive electrode current collector and the positive electrode current collector is exposed. It can be seen that the temperature rise due to the occurrence of a short circuit at the part is suppressed.

Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

20 Wound electrode assembly 30 Battery case 36 Safety valve 42 Positive electrode terminal 42a Positive electrode current collector 44 Negative electrode terminal 44a Negative electrode current collector 50 Positive electrode sheet (positive electrode)
52 Positive electrode current collector 52a Positive electrode current collector exposed portion 54 Positive electrode active material layer 56 Insulating layer 58 Boundary line 60 between positive electrode active material layer and insulating layer Negative electrode sheet (negative electrode)
62 Negative electrode current collector 62a Negative electrode current collector exposed portion 64 Negative electrode active material layer 70 Separator sheet (separator)
80 nonaqueous electrolyte 100 lithium ion secondary battery

Claims (1)

a positive electrode;
a negative electrode;
a non-aqueous electrolyte;
A lithium ion secondary battery comprising
The positive electrode includes a positive electrode current collector, a positive electrode active material layer, and an insulating layer,
The positive electrode current collector has at least one end portion where the positive electrode current collector is exposed,
The insulating layer is located at a boundary between the positive electrode active material layer and the exposed portion of the positive electrode current collector,
the angle formed by the main surface of the positive electrode current collector and the boundary surface between the positive electrode active material layer and the insulating layer on the side of the positive electrode active material layer is 45 degrees or more and 66 degrees or less;
The peel strength between the positive electrode current collector and the insulating layer is greater than the peel strength between the positive electrode current collector and the positive electrode active material layer,
The positive electrode active material layer has a volume density of 2.4 g/cm ³ or more and 3.5 g/cm ³ or less.
Lithium-ion secondary battery.

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