JP6015222B2 - Negative electrode plate for secondary battery, secondary battery, and battery pack - Google Patents

Description

  The present invention relates to a negative electrode plate for a secondary battery, a secondary battery, and a battery pack.

  A secondary battery represented by a lithium ion secondary battery has a high energy density and a high voltage, and the battery capacity gradually increases when the battery is charged before being completely discharged, which is called a memory effect at the time of charge / discharge. Since there is no decreasing phenomenon, it is used in various fields such as portable devices, notebook computers, and portable devices.

Currently, as a measure to prevent global warming, efforts to reduce CO ₂ emissions are being carried out on a global scale. By reducing the dependence on oil and allowing it to travel with a low environmental load, it can greatly reduce CO ₂ emissions. There is an urgent need to develop and promote next-generation clean energy vehicles represented by plug-in hybrid vehicles and electric vehicles that can contribute. If secondary batteries can be used as the driving force for these next-generation clean energy vehicles, there is no need to rely on gasoline, which can greatly contribute to CO ₂ reduction and greatly contribute to the prevention of global warming. it can. On the other hand, in order for a secondary battery to be used as a driving force for a next-generation clean energy vehicle, it is required that the battery can be used stably over a long period of time.

  Currently, various proposed secondary batteries include a positive electrode plate, a negative electrode plate, a separator, and a non-aqueous electrolyte. The positive electrode plate is generally provided with a negative electrode active material layer in which positive electrode active material particles are fixed to the surface of a current collector such as a metal foil. Moreover, as a negative electrode plate, what is equipped with the negative electrode active material layer by which the negative electrode active material particle | grains containing various carbon materials adhere to the collector surface, such as copper and aluminum, is common (for example, patent document 1). .

  Silicon-based and tin-based materials are known to have a higher theoretical capacity than carbon materials, and are attracting attention as materials for negative electrode active material particles that replace carbon materials. On the other hand, when an alkali metal ion, for example, lithium ion is electrochemically inserted into the negative electrode active material particles containing a silicon-based or tin-based material, the volume expands to about 3 to 4 times. In order to shrink, when charging and discharging are repeated, the active material particles may be pulverized. In addition, when the negative electrode active material layer expands and contracts during charge and discharge, cracks occur in the negative electrode plate, and the negative electrode active material layer includes negative electrode current collectors and negative electrode active material particles including silicon-based and tin-based materials. In some cases, the fixing interface is broken. Therefore, when negative electrode active material particles having a large volume change when electrochemically inserting alkali metal ions are used, there is a problem that cycle characteristics are liable to deteriorate.

JP 2006-310010 A

  The present invention has been made in view of such circumstances, and has a negative electrode plate for a secondary battery capable of improving cycle characteristics, in particular, a volume when an alkali metal ion is inserted electrochemically. It is a main subject to provide a negative electrode plate for a secondary battery that can improve cycle characteristics even when negative electrode active material particles having a large change are used, and a secondary battery and a battery pack using the same.

The present invention for solving the above problems is a negative electrode plate for an alkali metal ion secondary battery comprising a negative electrode current collector and a negative electrode active material laminate provided on the negative electrode current collector, wherein the negative electrode active material In the material laminate, a first negative electrode active material layer, a conductive layer, and a second negative electrode active material layer are laminated in this order, and the first negative electrode active material layer and the second negative electrode active material layer are , A negative electrode active material capable of occluding and releasing alkali metal ions, and a binder, wherein the conductive layer is a conductive material, a binder contained in the first negative electrode active material layer, and the second negative electrode active material layer. And another binder contained in the conductive layer is more JIS-K- than the binder contained in the first negative electrode active material layer and the second negative electrode active material layer. Large tensile fracture strain according to 7161 (1994) And wherein the tensile modulus conforming to JIS-K-7161 (1994) is small.

Moreover, this invention for solving the said subject is an alkali metal ion secondary battery containing a positive electrode plate, a negative electrode plate, and an electrolyte, Comprising: The said negative electrode plate is a negative electrode collector, The said negative electrode collector. The negative electrode active material laminate includes a first negative electrode active material layer, a conductive layer, and a second negative electrode active material layer, which are laminated in this order. The negative electrode active material layer and the second negative electrode active material layer include a negative electrode active material capable of occluding and releasing alkali metal ions, and a binder. The conductive layer includes a conductive material, and the first negative electrode active material layer. The material layer and another binder different from the binder contained in the second negative electrode active material layer, and the other binder contained in the conductive layer includes the first negative electrode active material layer and the second negative electrode active material layer. Than the binder contained in the negative electrode active material layer of JIS-K-716 (1994) in tensile breaking strain greater compliant, and wherein the tensile modulus conforming to JIS-K-7161 (1994) is small.

In addition, the present invention for solving the above-described problems includes at least a storage case, an alkali metal ion secondary battery including a positive electrode terminal and a negative electrode terminal, and a protection circuit having an overcharge and overdischarge protection function, A battery pack configured to house the alkali metal ion secondary battery and the protection circuit, wherein the alkali metal ion secondary battery includes a positive electrode plate, a negative electrode plate, and an electrolyte, and the negative electrode plate is A negative electrode current collector and a negative electrode active material laminate provided on the negative electrode current collector, wherein the negative electrode active material laminate comprises a first negative electrode active material layer, a conductive layer, and a second negative electrode active material. The material layers are laminated in this order, and the first negative electrode active material layer and the second negative electrode active material layer include a negative electrode active material capable of occluding and releasing alkali metal ions and a binder, and the conductive layer Is a conductive material, The first negative electrode active material layer and another binder different from the binder contained in the second negative electrode active material layer, and the other binder contained in the conductive layer is the first negative electrode active material The tensile fracture strain according to JIS-K-7161 (1994) is greater than the binder contained in the layer and the second negative electrode active material layer, and the tensile modulus of elasticity according to JIS-K-7161 (1994) Is small.

  According to the negative electrode plate for a secondary battery of the present invention, not only when negative electrode active material particles having a small volume change when an alkali metal ion is inserted electrochemically, but also negative electrode active material particles having a large volume change are used. Even if it is used, cycle characteristics can be improved. In addition, the same effects as described above can be obtained even in a secondary battery or a battery pack using the secondary battery negative electrode plate of the present invention.

It is a schematic sectional drawing which shows an example of the negative electrode plate for secondary batteries of this invention. It is a schematic sectional drawing which shows an example of the negative electrode plate for secondary batteries of this invention. It is a schematic sectional drawing which shows an example of the negative electrode plate for secondary batteries of this invention. It is a schematic sectional drawing which shows an example of the secondary battery of this invention. It is a sectional exploded view showing an example of a battery pack of the present invention.

  Hereinafter, the secondary battery negative electrode plate of the present invention, the secondary battery using the secondary battery negative electrode plate, and the battery pack will be described.

<< Anode plate for secondary battery >>
As shown in FIG. 1, the negative electrode plate 10 for a secondary battery of the present invention (also referred to as the negative electrode plate 10 of the present invention) includes a negative electrode current collector 1 and a negative electrode active material provided on the negative electrode current collector. The laminate 2 is included. Hereinafter, each structure of the negative electrode plate 10 of this invention is demonstrated concretely.

<Negative electrode current collector>
The negative electrode current collector 1 is not particularly limited, and a conventionally known negative electrode current collector used for a negative electrode plate for a secondary battery can be appropriately selected and used. For example, a negative electrode current collector formed of a simple substance such as an aluminum foil, a nickel foil, or a copper foil or an alloy can be preferably used. In addition, the negative electrode current collector includes one in which a material for ensuring conductivity is laminated on the surface thereof, and one in which some surface treatment is performed. As the negative electrode current collector 1 whose surface is processed on its surface, a negative electrode current collector in which a conductive substance is laminated on the surface of a material having a current collecting function, chemical polishing treatment, corona treatment, oxygen plasma treatment are used. Examples thereof include a negative electrode current collector made. That is, the negative electrode current collector 1 includes not only a current collector formed of only a material having a current collecting function, but also a surface in which a substance for ensuring conductivity is laminated, or some surface treatment. Also included are those made.

  The thickness of the negative electrode current collector 1 is not particularly limited as long as it can be used as a negative electrode current collector of a negative electrode plate for a secondary battery, but is preferably 5 to 200 μm, more preferably 10 to 50 μm. preferable.

<Negative electrode active material laminate>
As shown in FIG. 1, a negative electrode active material laminate 2 is provided on the negative electrode current collector 1. In the negative electrode plate 10 of the present invention, the negative electrode active material laminate 2 includes a first negative electrode active material layer 3, a conductive layer 4, and a second negative electrode active material layer 5, and from the negative electrode current collector 1 side, The first negative electrode active material layer 3, the conductive layer 4, and the second negative electrode active material layer 5 are laminated in this order.

  In the negative electrode plate 10 of the present invention, the first negative electrode active material layer 3 and the second negative electrode active material layer 5 include negative electrode active material particles and a binder as essential components, and the conductive layer 4 includes a conductive material. And another binder different from the binder contained in the first negative electrode active material layer 3 and the second negative electrode active material layer 5, and another contained in the conductive layer 4. The binder has a larger tensile fracture strain according to JIS-K-7161 (1994) than the binder contained in the first negative electrode active material layer 3 and the second negative electrode active material layer 5, and JIS-K. It is characterized by a small tensile elastic modulus according to -7161 (1994). Hereinafter, the tensile fracture strain conforming to JIS-K-7161 (1994) and the tensile elastic modulus conforming to JIS-K-7161 (1994) may be simply referred to as tensile fracture strain or tensile elastic modulus.

  In summary, the negative electrode plate 10 of the present invention is characterized by the following two points. The first feature is that the negative electrode active material laminate 2 includes a first negative electrode active material layer 3 and a second negative electrode active material layer 5, in other words, the negative electrode active material laminate 2 has 2 The negative electrode active material layer is included. The second feature is that a conductive layer 4 is provided between the first negative electrode active material layer 3 and the second negative electrode active material layer 5, and another binder contained in the conductive layer 4 is the first The tensile fracture strain is larger than that of the binder contained in the negative electrode active material layer 3 and the second negative electrode active material layer 5, and the tensile elastic modulus is small. According to the negative electrode plate 10 of the present invention having these characteristics, the cycle characteristics are improved for the following reason.

  In describing the effect of the first feature, when the negative electrode active material layer including the negative electrode active material particles has a single layer configuration, the single layer negative electrode active material layer includes two or more negative electrode active material particles including the negative electrode active material particles. When the negative electrode active material layer is divided into two layers, the stress applied to the single-layer negative electrode active material layer and one negative electrode when the single-layer negative electrode active material layer is divided into two or more negative electrode active material layers The stress applied to the active material layer will be described. When alkali metal ions are electrochemically inserted into the negative electrode active material particles, the negative electrode active material particles expand. At this time, stress due to expansion of the negative electrode active material particles is generated in the negative electrode active material layer. In addition, it is thought that the stress concerning a negative electrode active material layer becomes high as the quantity of the negative electrode active material particle contained in a negative electrode active material layer increases.

  Here, when the negative electrode active material layer having a single layer structure is divided into two or more negative electrode active material layers, the amount of the negative electrode active material particles contained in one divided negative electrode active material layer is determined as a single layer structure. This is less than the amount of the negative electrode active material particles contained in the negative electrode active material layer. Therefore, the stress applied to one negative electrode active material layer among the divided negative electrode active material layers is smaller than the stress applied to the single-layered negative electrode active material layer.

  Next, when the negative electrode active material layer having the single-layer structure is provided on the negative electrode current collector, the single-layer negative electrode active material layer is divided into two or more negative electrode active material layers on the negative electrode current collector. A case where one negative active material layer is provided will be described. As described above, the single-layered negative electrode active material layer has a higher stress than that applied to one negative electrode active material layer when the single-layered negative electrode active material layer is divided into two or more negative electrode active material layers. Stress is applied. Therefore, when a negative electrode active material layer having a single layer structure is provided on the negative electrode current collector, a high stress is applied to the negative electrode active material layer having a single layer structure when an alkali metal ion is inserted electrochemically. As a result, the negative electrode active material layer having a single layer structure is likely to warp. When the negative electrode active material layer is warped, the negative electrode active material layer from the negative electrode current collector is easily peeled off, resulting in a decrease in cycle characteristics.

  On the other hand, when a single-layered negative electrode active material layer is divided into two or more negative electrode active material layers, the stress applied to one negative electrode active material layer is smaller than the stress applied to the single-layered negative electrode active material layer. Therefore, in the one divided negative electrode active material layer, occurrence of warpage due to stress applied to the negative electrode active material layer is reduced. In other words, the first feature of the negative electrode plate 10 of the present invention is that the negative electrode active material laminate 2 includes the first negative electrode active material layer 3 and the second negative electrode active material layer 5, so The stress applied to the first negative electrode active material layer 3 present at a position close to the electric current body 1 is reduced, thereby preventing the separation of the first negative electrode active material layer 3 from the negative electrode current collector 1. is there. Further, by reducing the stress applied to the first negative electrode active material layer 3 and the second negative electrode active material layer 5, the conductivity in the first negative electrode active material layer 3 and the second negative electrode active material layer 5 is reduced. The collapse of the path and the binder that fixes the negative electrode active material particles to each other are also prevented.

  Next, the negative electrode active material layer having a single layer structure is divided into two or more negative electrode active material layers, and provided on the negative electrode current collector so that the divided negative electrode active material layers are in direct contact with each other. The state of each negative electrode active material layer when alkali metal ions are electrochemically inserted into the negative electrode active material particles included in each negative electrode active material layer in contact with the electrode will be described.

  As described above, the stress applied to each negative electrode active material layer is reduced by dividing the negative electrode active material layer into two or more negative electrode active material layers. The negative electrode active material layer expands at a certain rate, and a volume change occurs in the negative electrode active material layer. Since the negative electrode current collector does not substantially expand or hardly expand, one negative electrode active material layer provided on the closest position on the negative electrode current collector is in a direction away from the negative electrode current collector. Inflates towards. At this time, the other negative electrode active material layer provided on one of the negative electrode active material layers and in direct contact with the negative electrode active material layer follows the volume change due to expansion of the one negative electrode active material, and collects the negative electrode active material layer. Since the conductive path between one negative electrode active material layer and the other negative electrode active material layer collapses because it is pushed up in the direction away from the electric body, one negative electrode active material layer and the other negative electrode active material In the case where the binder fixing the layer is collapsed, there may be a case where the other negative electrode active material layer is cracked by being pushed up. When such a problem occurs, the negative electrode active material particles contained in the other negative electrode active material layer can no longer function, and the capacity decreases or the negative electrode active material layer can The negative electrode active material layer is peeled off, resulting in deterioration of cycle characteristics.

  Therefore, in the present invention, as described in the second feature, the negative electrode active material laminate 2 includes the first negative electrode active material layer 3 and the second negative electrode active material layer 5, and the first negative electrode More than JIS-K-7161 between the active material layer 3 and the second negative electrode active material layer 5 than the binder contained in the first negative electrode active material layer 3 and the second negative electrode active material layer 5. The conductive layer 4 containing another binder having a large tensile fracture strain in accordance with (1994) and a small tensile modulus in accordance with JIS-K-7161 (1994) is provided.

  Volume change due to expansion of the first negative electrode active material layer 3 when alkali metal ions are electrochemically inserted into the negative electrode active material particles contained in the first negative electrode active material layer 3 and the second negative electrode active material layer 5 Following this, the second negative electrode active material layer 5 is pushed up in the direction away from the negative electrode current collector 1, but on the first negative electrode active material layer 3, the conductive layer 4 having the above characteristics. Therefore, the conductive layer 4 absorbs the volume change due to the expansion of the first negative electrode active material layer 3. Thereby, it is possible to prevent the second negative electrode active material layer 5 from being pushed up along with the volume change due to the expansion of the first negative electrode active material layer 3, and to solve the problem of cracks that may occur in the second negative electrode active material layer 5. Can be prevented. Specifically, the collapse of the conductive path in the second negative electrode active material layer 5 that may be caused by the occurrence of cracks, the collapse of the binder that fixes the negative electrode active material particles to each other, and the like are suppressed. Similarly to the first negative electrode active material layer 3, the second negative electrode active material layer 5 also undergoes a volume change due to the expansion of the negative electrode active material particles, but the second negative electrode active material layer 5 has a negative electrode current collector side. Since the conductive layer 4 exists on this surface, the conductive layer 4 can absorb the volume change due to the expansion of the second negative electrode active material layer 5.

  In addition, when the conductive layer 4 contains a binder having a smaller tensile fracture strain than a binder contained in the first negative electrode active material layer 3 and the second negative electrode active material layer 5, or a binder having a large tensile elastic modulus, That is, the requirement that the binder contained in the conductive layer 4 has a larger tensile fracture strain than the binder contained in the first negative electrode active material layer 3 and the second negative electrode active material layer 5, and the tensile elastic modulus. If either one of the requirements for small size is not satisfied, even if the conductive layer 4 is provided between the first negative electrode active material layer 3 and the second negative electrode active material layer 5, the first negative electrode active material The volume change due to the expansion of the material layer 3 cannot be absorbed, and the above effect cannot be achieved.

  That is, in the present invention, the negative electrode active material laminate 2 is peeled off from the negative electrode current collector 1, and the conductive path is formed in the first negative electrode active material layer 3 and the second negative electrode active material layer 5. The first negative electrode active material layer prevents the collapse and the binder that fixes the negative electrode active material particles from collapsing by dispersing the stress applied to the negative electrode active material layer. The conductive layer 4 that is the second feature of the present invention is the collapse of the conductive path between the third negative electrode active material layer 5 and the second negative electrode active material layer 5, the collapse of the conductive path in the second negative electrode active material layer 5, and the collapse of the binder. It is prevented by making it exist. Thereby, in the negative electrode plate 10 of the present invention, high cycle characteristics are exhibited.

  Hereinafter, the first negative electrode active material layer 3, the second negative electrode active material layer 5, and the conductive layer 4 included in the negative electrode active material laminate 2 will be described. As shown in FIG. 1, in the negative electrode active material laminate 2, a first negative electrode active material layer 3, a conductive layer 4, and a second negative electrode active material layer 5 are laminated in this order from the negative electrode current collector 1 side. Laminated body.

<First negative electrode active material layer and second negative electrode active material layer>
The first negative electrode active material layer 3 and the second negative electrode active material layer 5 include negative electrode active material particles and a binder as essential components.

(Negative electrode active material particles)
The negative electrode active material particles contained in the first negative electrode active material layer 3 and the second negative electrode active material layer 5 are not particularly limited, and those conventionally known in the field of secondary batteries can be appropriately selected and used. . For example, natural graphite, artificial graphite, amorphous carbon, carbon black, carbon materials obtained by adding different elements to these components, metallic lithium and its alloys, tin, silicon and their alloys, tin, silicon, titanium cobalt Examples thereof include materials capable of occluding and releasing alkali metal ions, such as oxides, manganese, iron, and cobalt nitrides.

  Especially, in this invention, compared with a carbon material, silicon, tin, these alloys, or these oxides with a high theoretical capacity | capacitance can be used suitably as negative electrode active material particle. In addition, in a negative electrode plate using silicon, tin, and alloys thereof, or oxides thereof as negative electrode active material particles, the volume expands to about 3 to 4 times when alkali metal ions are electrically inserted. However, in the present invention, according to the first feature and the second feature described above, even when silicon, tin, and an alloy thereof, or an oxide thereof is used as the negative electrode active material particle, High cycle characteristics can be exhibited.

  Examples of the silicon alloy include an alloy of silicon and an element other than silicon. Examples of elements other than silicon include Fe, Co, Sb, Bi, Pb, Ni, Cu, Zn, Ge, In, Sn, and Ti. Examples of tin alloys include alloys of tin and elements other than tin. Examples of elements other than tin include Ni, Mg, Fe, Cu, and Ti. These elements forming an alloy with silicon and tin may be used alone or in combination of two or more.

  The shape of the negative electrode active material particles is not particularly limited, and for example, a scale shape, a flat shape, a spindle shape, or a spherical shape can be used. Further, the particles of the negative electrode active material particles are not particularly limited, and those having an arbitrary size can be appropriately selected and used in consideration of the thickness of the designed negative electrode active material laminate 2. However, as the particle diameter of the negative electrode active material particles is smaller, the surface area per unit weight can be increased and the rate characteristics can be improved. Therefore, when higher rate characteristics are required, the negative electrode active material particles have a small particle diameter, specifically less than 10 μm, preferably 5 μm or less, and particularly preferably 1 μm or less.

  The particle size of the negative electrode active material particles shown in the present invention and the present specification is an average particle size (volume median particle size: D50) measured by laser diffraction / scattering particle size distribution measurement. In addition, the particle size of the negative electrode active material is determined by using a particle recognition tool to identify the measured electron microscope observation data, and a particle size distribution graph based on the shape data obtained from the recognized particle image. It can be created and calculated from this particle size distribution graph. The particle size distribution graph can be created, for example, by using an image analysis type particle size distribution measurement software (manufactured by Mount Tech Co., Ltd., MAC VIEW) based on an electron microscope observation result.

  Moreover, the battery characteristics in the negative electrode plate 10 of the present invention are as follows: the first negative electrode active material layer 3, the material of the negative electrode active material particles contained in the second negative electrode active material layer 5, and the first negative electrode active material layer 3, It is determined according to the total amount of the negative electrode active material particles contained in the second negative electrode active material layer 5 or the like. Therefore, considering this point, the material and content of the negative electrode active material particles may be determined, and the material and content of the negative electrode active material particles are not particularly limited. Moreover, the negative electrode active material particles contained in the first negative electrode active material layer 3 and the second negative electrode active material layer 5 may be the same or different. Further, the content of the negative electrode active material particles in the first negative electrode active material layer 3 may be larger or smaller than the content of the negative electrode active material particles in the second negative electrode active material layer 5. The first negative electrode active material layer 3 and the second negative electrode active material layer 5 may be the same layer.

  There is no particular limitation on the layer thicknesses of the first negative electrode active material layer 3 and the second negative electrode active material layer 5, but the first negative electrode active material layer 3, the second negative electrode active material layer 5, and the conductive layer 4 are formed. It is preferable that the thickness of the negative electrode active material laminate 2 to be included is appropriately set within a range of 50 μm or less. By setting the layer thickness of the negative electrode active material laminate 2 to 50 μm or less, the distance between the negative electrode active material laminate 2 and the negative electrode current collector 1 can be shortened, and the impedance of the negative electrode plate 10 of the present invention can be lowered. it can. The thickness of the first negative electrode active material layer 3 may be thicker than the second negative electrode active material layer 5, may be thinner, or may be the same thickness.

(binder)
The first negative electrode active material layer 3 and the second negative electrode active material layer 5 contain a binder as an essential component. The binder contained in the 1st negative electrode active material layer 3 and the 2nd negative electrode active material layer 5 needs to satisfy | fill the conditions A shown below, and the 1st negative electrode active material layer 3 and the 1st The binder contained in the negative electrode active material layer 2 is determined in consideration of this point.

  Condition A: Another binder contained in the conductive layer 4 conforms to JIS-K-7161 (1994) rather than the binder contained in the first negative electrode active material layer 3 and the second negative electrode active material layer 5. The tensile fracture strain is large and the tensile modulus of elasticity according to JIS-K-7161 (1994) is small. In other words, the binder contained in the first negative electrode active material layer 3 and the second negative electrode active material layer 5 is more tensile compliant with JIS-K-7161 (1994) than the binder contained in the conductive layer 4. The fracture strain is small and the tensile elastic modulus conforming to JIS-K-7161 (1994) is large.

  The tensile fracture strain (%) based on JIS-K-7161 (1994) and tensile elastic modulus (GPa) based on JIS-K-7161 (1994) of the binder shown in Condition A are manufactured by Instron. It can be measured using a 5565 type testing machine. A test piece used for measurement of tensile fracture strain and tensile elastic modulus is a film made of a binder, which is cut into a width of 20 mm and a length of 150 mm, and the tensile speed is 10 mm / min. The measurement temperature is 25 ° C.

  Examples of binders that can be used for the first negative electrode active material layer 3, the second negative electrode active material layer 5, and the conductive layer 4 include polyimide resin, polyamideimide resin, polyvinylidene fluoride resin, polyethylene oxide resin, and polyacrylic acid. Examples thereof include resins and styrene butadiene rubber. Among these resins, the polyimide resin and the polyamideimide resin are high in adhesion and tensile strength and high in durability, and are used as the first negative electrode active material layer 3 and the second negative electrode active material layer 5. Suitable as a binder to be included.

  The first negative electrode active material layer 3 and the second negative electrode active material layer 5 may each contain the same binder, or may contain different binders. In addition, the same binder said here means the binder with the same tensile fracture strain shown in the said conditions A, and a tensile elasticity modulus. That is, even if the binder has the same composition, if the tensile fracture strain and the tensile elastic modulus are different, it becomes another binder. This also applies to the relationship between the binder contained in the first negative electrode active material layer 3 and the second negative electrode active material layer 5 and the binder contained in the conductive layer 4. In addition, one or both of the first negative electrode active material layer 3 and the second negative electrode active material layer 5 or both negative electrode active material layers may contain two or more binders.

  There is no particular limitation on the content of the binder satisfying the above condition A in the first negative electrode active material layer 3 and the second negative electrode active material layer 5, the components of the negative electrode active material particles contained in each negative electrode active material layer, What is necessary is just to set suitably according to the content. A preferable content of the binder satisfying the above condition A is about 50% by mass or more and 95% by mass or less with respect to all components of the first negative electrode active material layer 3. The same applies to the second negative electrode active material layer 5.

  Moreover, the 1st negative electrode active material layer 3 and the 2nd negative electrode active material layer 5 may contain the binder which does not satisfy | fill the said conditions A in the range which does not prevent the meaning of this invention. In this case, the content of the binder that does not satisfy the above condition A needs to be less than 50% by mass with respect to all the binder components contained in the first negative electrode active material layer 3. This is because the effect of the present invention cannot be achieved when the range is exceeded. The same applies to the second negative electrode active material layer 5. The content of the binder that does not satisfy the above condition A is preferably less than 20% by mass.

(Optional ingredients)
Further, the first negative electrode active material layer 3 and the second negative electrode active material layer 5 contain optional components together with negative electrode active material particles as the essential component and a binder satisfying the condition A. May be. For example, when better conductivity is desired, a conductive material or the like may be included.

<Conductive layer>
Between the first negative electrode active material layer 3 and the second negative electrode active material layer 5, the conductive material, the first negative electrode active material layer 3, and the second negative electrode active material layer 5 are essential components. A binder satisfying the above condition A in relation to the binder contained in the first negative electrode active material layer 3 and the second negative electrode active material layer 5. A conductive layer 4 is provided.

(Another binder)
Another binder contained in the conductive layer 4 is determined in relation to the binder contained in the first negative electrode active material layer 3 and the second negative electrode active material layer 5. Specifically, a binder having a higher tensile fracture strain and a lower tensile elastic modulus than the binder contained in the first negative electrode active material layer 3 and the second negative electrode active material layer 5, that is, satisfying the above condition A. Any binder may be used. Hereinafter, another binder may be referred to as a binder satisfying the above condition A.

  The other binder contained in the conductive layer 4 only needs to satisfy the above condition A, but the binder contained in the first negative electrode active material layer 3 and the second negative electrode active material layer 5 and the conductive layer 4 When the difference in tensile fracture strain (%) of another binder contained in the material and the difference in tensile elastic modulus (GPa) are small, the volume change due to expansion of the first negative electrode active material layer 3 is sufficiently absorbed. There are cases where it cannot be done. Therefore, considering this point, the tensile fracture strain of another binder contained in the conductive layer 4 is the tensile fracture strain of the binder contained in the first negative electrode active material layer 3 and the second negative electrode active material layer 5 ( %) Is preferably 200 or more. Further, the tensile elastic modulus of another binder contained in the conductive layer 4 was set so that the tensile elastic modulus (GPa) of the binder contained in the first negative electrode active material layer 3 and the second negative electrode active material layer 5 was 100. Sometimes it is preferred to be 70 or less. In particular, it is preferable that both the tensile fracture strain and the tensile elastic modulus are in this preferable range.

  For example, when a polyimide resin or a polyamide-imide resin is used as the binder contained in the first negative electrode active material layer 3 and the second negative electrode active material layer 5, the binder contained in the conductive layer 4 is tensile. It is preferable to use a polyvinylidene fluoride resin or the like in which the fracture strain and tensile elastic modulus are in the above preferred ranges.

  Moreover, when the binder contained in the 1st negative electrode active material layer 3 and the binder contained in the 2nd negative electrode active material layer 5 differ, another binder contained in the conductive layer 4 is 1st negative electrode active material. Of the binder contained in the material layer 3 and the binder contained in the second negative electrode active material layer 5, the tensile fracture strain of the binder having the larger tensile fracture strain and the tensile strength of the binder having the smaller tensile modulus Based on the elastic modulus, a binder having a larger tensile fracture strain and a smaller tensile elastic modulus than the tensile fracture strain (%) and the tensile elastic modulus (GPa) may be used.

  There is no particular limitation on the content of the binder that satisfies the above condition A for all the constituent components of the conductive layer 4, but it is preferably 10% by mass or more and 90% by mass or less with respect to all the constituent components of the conductive layer 4.

  In addition, the conductive layer 4 may contain a binder that does not satisfy the condition A as long as the gist of the present invention is not hindered. However, when the content of the binder that does not satisfy the above condition A with respect to all the binders of the conductive layer 4 is 50% by mass or more, it plays the role of the conductive layer 4 that absorbs the volume change due to the expansion of the first negative electrode active material layer 3. Therefore, the content of the binder that does not satisfy the above condition A with respect to all the binders of the conductive layer 4 needs to be less than 50% by mass. Preferably, the content of the binder that does not satisfy the condition A is less than 20% by mass.

(Conductive material)
The conductive layer 4 contains a conductive material together with the other binder. The conductive material contained in the conductive layer 4 is a conductive path between the negative electrode active material particles present in the first negative electrode active material layer 3 and the negative electrode active material particles present in the second negative electrode active material layer 5. Play a role in forming.

  The conductive material only needs to have conductivity, and the conductive material is not particularly limited as long as it satisfies this requirement, and a conventionally known material can be appropriately selected and used. Examples of known conductive materials include acetylene black, carbon nanofibers, carbon nanotubes, graphene, and metal particles.

  The content of the conductive material with respect to all the constituent components of the conductive layer 4 is not particularly limited, and the negative electrode active material component, the particle diameter, or the first negative electrode active material layer 3 and the second negative electrode active material layer 5 are not limited. It can set suitably according to content etc. In general, a sufficient conductive path between the first negative electrode active material layer 3 and the second negative electrode active material layer 5 by setting the content of the conductive material with respect to all components of the conductive layer 4 to 30% by mass or more. Therefore, it is preferable that the conductive material is contained in an amount of 30% by mass or more with respect to all the constituent components of the conductive layer 4. The upper limit of the content of the conductive material is determined according to the content of the binder that satisfies the above condition A.

  In addition, the conductive layer 4 may contain negative electrode active material particles as an optional component. However, when the amount of the negative electrode active material particles relative to all the constituent components of the conductive layer 4 is large, the conductive layer 4 itself In some cases, the first negative electrode active material layer 3 and the second negative electrode active material layer 5 may not sufficiently absorb volume changes due to expansion. In particular, when silicon, tin, and alloys thereof, or oxides thereof are used as the negative electrode active material particles, the influence is great. Therefore, when these negative electrode active material particles are included in the conductive layer 4, the content of the negative electrode active material particles with respect to all the constituent components of the conductive layer 4 is preferably less than 50 mass%.

  In addition, as shown in FIG. 2, the conductive layer 4 is preferably provided between the negative electrode current collector 1 and the first negative electrode active material layer 3. When the conductive layer 4 is also provided between the negative electrode current collector 1 and the first negative electrode active material layer 3, the first negative electrode active material layer 3 is only in a direction away from the negative electrode current collector. In addition, since it expands toward the negative electrode current collector, expansion in a direction away from the negative electrode current collector 1 is reduced. In this embodiment, the conductive layer is provided between the negative electrode current collector 1 and the first negative electrode active material layer 3 and between the first negative electrode active material layer 3 and the second negative electrode active material layer 5. 4 is provided, the volume change of the first negative electrode active material layer 3 that expands toward the negative electrode current collector 1 side and in the direction away from the negative electrode current collector 1 is caused by changing the volume of both the conductive layers 4. The cycle characteristics can be further improved.

  In addition, the negative electrode plate 10 of the present invention can be variously modified within the range not limited to the form shown in FIGS. For example, as shown in FIG. 3, one or more other negative electrode active material layers X may be provided on the second negative electrode active material layer 5. By setting it as such a structure, the stress by the expansion concerning each layer can be reduced. In this configuration, it is preferable to provide the conductive layer 4 between the second negative electrode active material layer 5 and another negative electrode active material layer X, and the negative electrode current collector 1 and the first negative electrode active material. A conductive layer 4 is preferably provided between the layer 3 and the layer 3.

  1 to 3, the first negative electrode active material layer 3 and the conductive layer 4 and the conductive layer 4 and the second negative electrode active material layer 5 are in direct contact with each other. A separate layer may be provided between the first negative electrode active material layer 3 and the conductive layer 4 and / or between the conductive layer 4 and the second negative electrode active material layer 5. Examples of the separate layer include a layer that does not hinder absorption of volume change by the conductive layer 4 such as a layer containing only a conductive material.

  The method for producing the negative electrode plate 10 of the present invention is not particularly limited, and a first negative electrode active material in which a binder satisfying the above condition A is selected and the selected binder and negative electrode active material particles are dispersed or dissolved in an appropriate solvent. A coating liquid for the layer, a coating liquid for the second negative electrode active material layer, and a coating liquid for the conductive layer in which the selected binder and conductive material are dispersed or dissolved in an appropriate solvent, On the body, the first negative electrode active material layer coating liquid is applied and dried by a printing method, spin coating, dip coating, bar coating, spray coating, etc. to form a first negative electrode active material layer, Next, a conductive layer coating solution is applied and dried on the first negative electrode active material layer to form a conductive layer, and a second negative electrode active material layer coating solution is applied onto the conductive layer. Manufacture can be performed by drying and forming a conductive layer. In addition, when the surface of the negative electrode current collector 1 is porous, provided with a large number of irregularities, or has a three-dimensional structure, it can be manually applied in addition to the above method. is there. The negative electrode plate 10 of the present invention is not limited to the one manufactured by this manufacturing method, and can be manufactured using various vacuum processes.

<< Secondary battery >>
Next, the secondary battery of the present invention using the negative electrode plate of the present invention described above will be described with reference to FIG. FIG. 4 is a schematic view showing an example of the secondary battery of the present invention.

  As shown in FIG. 4, the secondary battery 100 of the present invention includes a negative electrode plate 10 in which a negative electrode active material laminate 2 is provided on one side of a negative electrode current collector 1, and a positive electrode current collector combined therewith. It is composed of a positive electrode plate 50 in which a positive electrode active material layer 54 is provided on one surface side of an electric body 55, and a separator 70 provided as needed between the negative electrode plate 10 and the positive electrode plate 50. It is housed in a container constituted by the exteriors 81 and 82, and is sealed in a state in which the container is filled with an electrolyte 90. Here, the secondary battery 100 of the present invention is characterized in that the negative electrode plate 10 is the negative electrode plate of the present invention described above.

  Hereinafter, configurations other than the negative electrode plate described above will be described. The negative electrode plate is as described in the negative electrode plate 10 of the present invention, and a detailed description thereof is omitted here. In the following description, the secondary battery of the present invention will be described mainly with respect to a lithium ion secondary battery. However, the secondary battery 100 of the present invention is a secondary battery other than a lithium ion secondary battery, for example, , A magnesium ion secondary battery, a calcium ion secondary battery, and an aluminum ion secondary battery.

(Positive electrode plate)
The positive electrode plate 50 constituting the secondary battery 100 of the present invention is not particularly limited, and a conventionally known positive electrode plate can be appropriately selected and used according to the type of the secondary battery. For example, as a positive electrode plate of a lithium ion secondary battery, a positive electrode such as a lithium transition metal composite oxide is formed on a part of the surface of a positive electrode current collector 55 similar to the negative electrode current collector used in the negative electrode plate 10 of the present invention. Examples include a positive electrode plate in which a positive electrode active material layer 54 is formed by applying and drying a solution in which active material particles, a conductive material, a resin binder, and the like are dispersed, and pressing as necessary. it can.

(Separator)
There is no limitation in particular about the separator 70, A conventionally well-known separator can be suitably selected and used in the field of a secondary battery. For example, a three-layer structure in which a lithium ion permeable polyethylene film having micropores is sandwiched between porous lithium ion permeable polypropylene films can be suitably used. Note that, when a solid electrolyte or a semi-solid electrolyte is used as the electrolyte, the secondary battery can be configured without a separator.

(Electrolytes)
As the electrolyte 90 used in the present invention, generally, when the secondary battery 100 of the present invention is a lithium ion secondary battery, a non-aqueous electrolyte solution in which a lithium salt is dissolved in an organic solvent is used. it can.

Examples of the lithium salt include inorganic lithium salts such as LiClO ₄ , LiBF ₄ , LiPF ₆ , LiAsF ₆ , LiCl, and LiBr; LiB (C ₆ H ₅ ) ₄ , LiN (SO ₂ CF ₃ ) ₂ , LiC ( Organic compounds such as SO ₂ CF ₃ ) ₃ , LiOSO ₂ CF ₃ , LiOSO ₂ C ₂ F ₅ , LiOSO ₂ C ₄ F ₉ , LiOSO ₂ C ₅ F ₁₁ , LiOSO ₂ C ₆ F ₁₃ , and LiOSO ₂ C ₇ F ₁₅ Typical examples include lithium salts.

  Examples of the organic solvent used for dissolving the lithium salt include cyclic esters, chain esters, cyclic ethers, and chain ethers.

  As the structure of the secondary battery 100 manufactured using the negative electrode plate 10, the positive electrode plate 50, the electrolyte 90, and the separator 70 provided as necessary, a conventionally known structure can be appropriately selected and used. For example, the structure which winds said negative electrode plate 10 and the positive electrode plate 50 in the shape of a spiral via the separator 70, and accommodates in a battery container is mentioned. As another aspect, a structure in which the positive electrode plate 50 and the negative electrode plate 10 cut into a predetermined shape are stacked and fixed via a separator 70, and this is housed in a battery container may be employed. In any structure, after the positive electrode plate 50 and the negative electrode plate 10 were accommodated in the battery container, the lead wire attached to the positive electrode plate was connected to the positive electrode terminal provided in the outer container, while being attached to the negative electrode plate. A secondary battery is manufactured by connecting the lead wire to a negative electrode terminal provided in the outer container, filling the battery container with an electrolyte 90, and sealing the battery.

  Since the secondary battery 100 of the present invention described above includes the negative electrode plate 10 of the present invention described above, the cycle characteristics of the secondary battery of the present invention can be improved.

<< Battery pack >>
Next, a battery pack 200 configured using the secondary battery 100 of the present invention will be described with reference to FIG. FIG. 5 is a schematic exploded view showing an example of the battery pack 200 of the present invention.

  As shown in FIG. 5, the battery pack 200 is configured such that the secondary battery 100 is housed in a resin container 36 a, a resin container 36 b, and an end case 37. Further, a protection circuit for preventing overcharge and overdischarge between one end face of the nonaqueous electrolyte secondary battery, which is a face including the positive electrode terminal 32 and the negative electrode terminal 33, and the end case 37. A substrate 34 is provided.

  The protection circuit board 34 includes an external connection connector 35. The external connection connector 35 is connected to an external connection window 38a provided in the resin container 36a and an external connection window 38b provided in the end case 37. Inserted and connected to external terminals. The protection circuit board 34 includes a charge / discharge safety circuit (not shown) for controlling charge / discharge, a wiring circuit for connecting the external connection terminal and the secondary battery 100, and the like.

  As the battery pack 200, a configuration of a conventionally known battery pack can be appropriately selected except that the secondary battery 100 of the present invention using the negative electrode plate 10 of the present invention is used. Although not shown, the battery pack 200 appropriately includes a positive electrode lead plate connected to the positive electrode terminal 32, a negative electrode lead plate connected to the negative electrode terminal 33, an insulator, and the like between the secondary electrical ground 100 and the end case 37. It may be.

  In addition, the secondary battery 100 of the present invention using the negative electrode plate 10 of the present invention has functions such as blocking of excessive current, battery temperature monitoring, etc., in addition to the use mode for the battery pack, The protection circuit may be used in an embodiment in which the protection circuit is integrated with the secondary battery. In such an embodiment, the battery pack can be used as a secondary battery having a protection function and a protection circuit without constituting a battery pack, and is highly versatile. In addition, some aspects demonstrated above are only illustrations, and do not limit the use of the negative electrode plate 10 of this invention, or the secondary battery 100 of this invention at all.

  Since the secondary battery constituting the battery pack 200 of the present invention described above includes the negative electrode plate 10 of the present invention described above, the cycle characteristics of the battery pack 200 of the present invention can also be improved. it can.

  Next, the present invention will be described more specifically with reference to examples and comparative examples. Hereinafter, unless otherwise specified, parts or% is based on mass.

Example 1
To 20.0 g of Si metal having an average particle size of 2.7 μm (manufactured by Kanto Metal Industry Co., Ltd.), 4.0 g of polyimide resin (PIX-L110 Hitachi Chemical Co., Ltd.) and NMP (N-methyl-2-pyrrolidone) ( 12.0 g (Mitsubishi Chemical Co., Ltd.) was dispersed and stirred with an Excel auto homogenizer (Nihon Seiki Seisakusho Co., Ltd.) at a rotational speed of 4000 rpm for 10 minutes. Next, 1.0 g of acetylene black powder (Denka Black, manufactured by Denki Kagaku Kogyo Co., Ltd.) and 7.0 g of NMP (N-methyl-2-pyrrolidone) (manufactured by Mitsubishi Chemical Corporation) are dispersed in the dispersion. The negative electrode active material layer coating liquid A was prepared by kneading with an Excel auto homogenizer (manufactured by Nippon Seiki Seisakusho Co., Ltd.) at a rotational speed of 4000 rpm for 15 minutes.

  Next, 8.0 g of acetylene black powder (Denka Black, manufactured by Denki Kagaku Kogyo Co., Ltd.), 2.0 g of polyvinylidene fluoride (PVdF), NMP (N-methyl-2-pyrrolidone) (manufactured by Mitsubishi Chemical Corporation) 7.0 g was dispersed and stirred in the same manner as the negative electrode active material layer coating liquid A to prepare a conductive layer coating liquid A.

  A copper foil having a thickness of 10 μm (manufactured by Nippon Foil Co., Ltd.) was prepared as a current collector, and the amount of the first negative electrode active material layer finally obtained was 10 μm. The negative electrode active material layer coating liquid A prepared above was applied to one side with an applicator, placed in a 120 ° C. drying furnace, and dried for 10 minutes to form a first negative electrode active material layer. Next, the conductive layer coating solution prepared above was applied with an applicator so that the thickness of the conductive layer finally obtained on the dried first negative electrode active material layer was 3 μm. The conductive layer was formed by installing in a drying furnace and drying for 10 minutes. Next, the negative electrode active material layer coating solution A prepared above is applied onto the dried conductive layer with an applicator so that the thickness of the second negative electrode active material layer finally obtained is 10 μm. The second negative electrode active material layer was formed by installing in a drying furnace at 120 ° C. and drying for 10 minutes.

Next, a negative electrode current collector having a first negative electrode active material layer, a conductive layer, and a second negative electrode active material layer provided on the surface in this order is placed in an atmospheric electric furnace (N ₂ substitution, oxygen concentration of 200 ppm or less). And heated to 300 ° C. over 60 minutes from room temperature, held at 300 ° C. for 60 minutes, and then cooled to room temperature to obtain a negative electrode plate. The negative electrode plate cut into a predetermined size (a disk having a diameter of 15 mm) was used as the negative electrode plate of Example 1.

(Example 2)
Polyvinylidene fluoride (PVdF) 2.0 g was changed to 2.0 g of polyethylene oxide (PEO-1 manufactured by Sumitomo Seika Co., Ltd.), and NMP (N-methyl-2-pyrrolidone) (manufactured by Mitsubishi Chemical Corporation) A conductive layer coating solution B was prepared using the same preparation method as that for the conductive layer coating solution A except that 7.0 g was changed to 7.0 g of water. A negative electrode plate of Example 2 was obtained in the same manner as Example 1 except that the conductive layer coating liquid B prepared above was used instead of the conductive layer coating liquid A.

Example 3
Except for changing 4.0 g of polyimide resin (PIX-L110 Hitachi Chemical Co., Ltd.) to 4.0 g of polyamideimide resin (manufactured by Torlon Solvay Specialty Polymers Japan), it is the same as coating liquid A for negative electrode active material layer. A negative electrode active material layer coating solution B was prepared using the preparation method. A negative electrode plate of Example 3 was obtained in the same manner as in Example 1 except that the negative electrode active material layer coating liquid B prepared above was used instead of the negative electrode active material layer coating liquid A.

(Comparative Example 1)
The negative electrode plate of Comparative Example 1 in which only the first negative electrode active material layer was provided on the current collector was the same as Example 1 except that the conductive layer and the second negative electrode active material layer were not formed. Obtained.

(Comparative Example 2)
A negative electrode active material layer coating solution C was prepared by changing 4.0 g of polyimide resin (PIX-L110 Hitachi Chemical Co., Ltd.) to 4.0 g of polyvinylidene fluoride (PVdF). A comparative example was made in the same manner as in Example 1 except that the first negative electrode active material layer and the second negative electrode active material layer were formed using the negative electrode active material layer coating liquid C prepared above. 2 negative electrode plates were obtained.

(Comparative Example 3)
Except for changing 2.0 g of polyvinylidene fluoride (PVdF) to 2.0 g of polyimide resin (PIX-L110 Hitachi Chemical Co., Ltd.), all for the conductive layer using the same preparation method as the coating liquid A for conductive layer A coating liquid C was prepared. A negative electrode plate of Comparative Example 3 was obtained in the same manner as Example 1 except that the conductive layer coating solution C prepared above was used instead of the conductive layer coating solution A.

  The tensile fracture strain and tensile strength of the binder contained in the first negative electrode active material layer, the second negative electrode active material layer, and the conductive layer of each of the above Examples and Comparative Examples are JIS-K-7161 (1994). The tensile fracture strain and tensile modulus when measured in an environment of 25 ° C. using an Instron 5565 type testing machine. The test piece used for the measurement of the tensile modulus is a film composed of a binder, which is cut into a width of 20 mm and a length of 150 mm, and the tensile speed is 10 mm / min. Table 1 shows the tensile fracture strain (%) and tensile elastic modulus (GPa) of the binder contained in the first negative electrode active material layer, the second negative electrode active material layer, and the conductive layer.

(Battery characteristics evaluation)
Lithium hexafluorophosphate (LiPF ₆ ) was added as a solute to an ethylene carbonate (EC) / diethyl carbonate (DEC) / ethyl methyl carbonate (EMC) mixed solvent (weight ratio = 30 wt%: 30 wt%: 30 wt%). After adjusting the concentration of LiPF _{6 as} the solute to be 1 mol / L, 10 wt% FEC was added to the electrolytic solution to prepare a non-aqueous electrolytic solution. Using the negative electrode plate of each example and comparative example as a working electrode, using a metal lithium plate as a counter electrode plate and a reference electrode plate, and using the non-aqueous electrolyte prepared above as an electrolyte, a tripolar coin cell was assembled, and It used for the discharge test and the cycle test.

(Initial charging test)
The test cell was charged at a constant current (0.85 mA) at 25 ° C. until the voltage reached 0.001 V. After the voltage reached 0.001 V, the voltage was reduced to 0.001 V. In order not to fall below, the current (charge rate: 0.1 C) was decreased until it became 5% or less, charged at a constant voltage, fully charged, and then rested for 10 minutes. Here, the “0.1C” means a current value (current value reaching the end-of-charge voltage) that is charged with constant current using the tripolar coin cell and ends charging in 10 hours. To do. The constant current was set so that a theoretical discharge amount of 4200 mAh / g of Si metal as an active material was charged in 10 hours at the working electrode in the test cell.

(Initial discharge test)
Thereafter, the fully charged test cell was measured at a constant current (0.85 mA) (discharge rate) until the voltage changed from 0.001 V (full charge voltage) to 1.5 V (discharge end voltage) in an environment of 25 ° C. : 0.1C), the cell voltage (V) is plotted on the vertical axis, the discharge time (h) is plotted on the horizontal axis, a discharge curve was prepared, and the initial discharge capacity (mAh) of the negative electrode plate was determined. The initial discharge capacity is also shown in Table 1.

(Cycle test)
Similarly to the initial charge / discharge test, the test cell after the initial charge / discharge test is performed twice, and the average value of the discharge capacity at this time is used as the initial value during the cycle test, and the same charge / discharge test as in the initial charge / discharge test is performed. The discharge test was repeated, and the number of cycles when the discharge capacity was 90% or less with respect to the initial value was determined. The number of cycles is also shown in Table 1.

  As apparent from Table 1, the negative electrode active material laminate includes two or more negative electrode active material layers, and the tensile fracture strain is larger between the negative electrode active material layers than the binder contained in the negative electrode active material layer, and According to the negative electrode plate of the example in which the conductive layer containing another binder having a small tensile elastic modulus was provided, cycle characteristics even when silicon-based negative electrode active material particles having a large volume change during expansion during charging were used. Improvements were made. On the other hand, Comparative Example 2 in which a negative electrode plate of Comparative Example 1 in which the negative electrode active material was configured as a single layer, a binder contained in the negative electrode active material layer, and a conductive layer containing a binder having the same tensile fracture strain and tensile modulus were provided. In the negative electrode plate 3, the cycle characteristics were significantly reduced as compared with the negative electrode plate of the example.

DESCRIPTION OF SYMBOLS 1 ... Negative electrode collector 2 ... Negative electrode active material laminated body 3 ... 1st negative electrode active material layer 4 ... Conductive layer 5 ... 2nd negative electrode active material layer 10 ... Negative electrode Plate 50 ... Positive electrode plate 54 ... Positive electrode active material layer 55 ... Positive electrode current collector 32 ... Positive electrode terminal 33 ... Negative electrode terminal 34 ... Protection circuit board 35 ... External connection connector 36a 36b ... Resin container 37 ... End case 38a, 38b ... External connection window 70 ... Separator 81, 82 ... Exterior 90 ... Electrolyte 100 ... Secondary battery 200 ...・ Battery pack

Claims (3)

A negative electrode plate for an alkali metal ion secondary battery comprising a negative electrode current collector and a negative electrode active material laminate provided on the negative electrode current collector,
In the negative electrode active material laminate, a first negative electrode active material layer, a conductive layer, and a second negative electrode active material layer are laminated in this order,
The first negative electrode active material layer and the second negative electrode active material layer include a negative electrode active material capable of occluding and releasing alkali metal ions, and a binder,
The conductive layer includes a conductive material and another binder different from the binder contained in the first negative electrode active material layer and the second negative electrode active material layer,
Another binder contained in the conductive layer is a tensile fracture strain based on JIS-K-7161 (1994) rather than the binder contained in the first negative electrode active material layer and the second negative electrode active material layer. A negative electrode plate for an alkali metal ion secondary battery characterized by having a large tensile elastic modulus in accordance with JIS-K-7161 (1994). An alkali metal ion secondary battery including a positive electrode plate, a negative electrode plate, and an electrolyte,
The negative electrode plate includes a negative electrode current collector and a negative electrode active material laminate provided on the negative electrode current collector,
In the negative electrode active material laminate, a first negative electrode active material layer, a conductive layer, and a second negative electrode active material layer are laminated in this order,
The first negative electrode active material layer and the second negative electrode active material layer include a negative electrode active material capable of occluding and releasing alkali metal ions, and a binder,
The conductive layer includes a conductive material and another binder different from the binder contained in the first negative electrode active material layer and the second negative electrode active material layer,
Another binder contained in the conductive layer is a tensile fracture strain based on JIS-K-7161 (1994) rather than the binder contained in the first negative electrode active material layer and the second negative electrode active material layer. An alkali metal ion secondary battery having a large tensile elastic modulus in accordance with JIS-K-7161 (1994). A storage case, an alkali metal ion secondary battery including a positive electrode terminal and a negative electrode terminal, and a protection circuit having an overcharge and overdischarge protection function are provided, and the alkali metal ion secondary battery and the protection circuit are provided in the storage case. A battery pack configured to be housed,
The alkali metal ion secondary battery includes a positive electrode plate, a negative electrode plate, and an electrolyte,
The negative electrode plate includes a negative electrode current collector and a negative electrode active material laminate provided on the negative electrode current collector,
In the negative electrode active material laminate, a first negative electrode active material layer, a conductive layer, and a second negative electrode active material layer are laminated in this order,
The first negative electrode active material layer and the second negative electrode active material layer include a negative electrode active material capable of occluding and releasing alkali metal ions, and a binder,
The conductive layer includes a conductive material and another binder different from the binder contained in the first negative electrode active material layer and the second negative electrode active material layer,
Another binder contained in the conductive layer is a tensile fracture strain based on JIS-K-7161 (1994) rather than the binder contained in the first negative electrode active material layer and the second negative electrode active material layer. A battery pack characterized by having a large tensile elastic modulus according to JIS-K-7161 (1994).

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