Battery negative electrode and battery

Abstract

To provide a battery negative electrode in which the orientation of graphite in the negative electrode is maintained even after a pressing process, and a battery including the negative electrode.SOLUTION: A battery negative electrode includes a first negative electrode active material layer including first graphite having an aspect ratio of 2 to 5 and second graphite having an aspect ratio of 1 to 1.4, and having a peak intensity ratio (I110 / I002) determined by XRD measurement of 0.03 or more, and a current collector.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a negative electrode for a battery and a battery.

Background Art

[0002] In recent years, secondary batteries such as lithium-ion batteries have an increasing tendency in the areal amount of the active material in the electrode in order to increase the energy density and reduce the cost.

[0003] In such an electrode, the charge-discharge capacity at a high rate is significantly reduced. On the other hand, in order to increase the charge-discharge capacity of a lithium-ion battery, attempts have been reported to orient graphite, which is a negative electrode active material, in the negative electrode (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the orientation of the graphite is difficult to maintain after the pressing step of forming the negative electrode.

[0006] A problem to be solved by one embodiment of the present disclosure is to provide a negative electrode for a battery having low electrical resistance and a battery including the negative electrode for a battery.

Means for Solving the Problems

[0007] Means for solving the above problems include the following aspects. <1> A first graphite having an aspect ratio of 2 to 5 and a second graphite having an aspect ratio of 1 to 1.4, and the peak intensity ratio (I 110 / I 002A negative electrode for a battery, comprising a first negative electrode active material layer in which [ [ID=]] is 0.03 or more, and a current collector. <2> The negative electrode for a battery according to <1>, wherein in the first negative electrode active material layer, the mass ratio of the second graphite to the first graphite is 30 / 70 to 70 / 30. <3> The negative electrode for a battery according to <1> or <2>, further comprising a second negative electrode active material layer that contains the second graphite and does not contain the first graphite, between the first negative electrode active material layer and the current collector. <4> The negative electrode for a battery according to any one of <1> to <3>, having the first negative electrode active material layer as the outermost layer. <5> A battery including the negative electrode for a battery according to any one of <1> to <4>.

Advantages of the Invention

[0008] According to the present disclosure, there is provided a negative electrode for a battery with low electrical resistance, and a battery including the negative electrode for a battery.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present disclosure will be described. The description is illustrative of the embodiments and does not limit the scope of the present disclosure.

[0011] In this specification, a numerical range indicated using "~" indicates a range that includes the numerical values described before and after "~" as the minimum value and the maximum value, respectively. In the numerical ranges described step by step in this specification, the upper limit value or lower limit value described in one numerical range may be replaced with the upper limit value or lower limit value of the numerical range described in other step-by-step descriptions. Also, in the numerical ranges described in this specification, the upper limit value or lower limit value of the numerical range may be replaced with the value shown in the examples.

[0012] In this specification, the term "step" includes not only an independent step but also cases where it cannot be clearly distinguished from other steps, as long as the intended purpose of the step is achieved.

[0013] In this specification, when describing embodiments with reference to the drawings, the configuration of the embodiment is not limited to the configuration shown in the drawings. Also, the sizes of the members in each drawing are conceptual, and the relative size relationships between the members are not limited thereto.

[0014] In this specification, each component may contain a plurality of corresponding substances. When referring to the amount of each component in the composition in this embodiment, when there are a plurality of substances corresponding to each component in the composition, unless otherwise specified, it means the total amount of the plurality of substances present in the composition.

[0015] In this specification, the term "aspect ratio" refers to the ratio of the major axis to the minor axis (major axis / minor axis) in the graphite particles, and an aspect ratio of 1 means a perfect circle. Specifically, the "aspect ratio" refers to the ratio b / c when the length b of the minor axis and the thickness c of the rectangular parallelepiped circumscribing the graphite particles (including secondary particles) are used for the first graphite. Also, when used for the second graphite, it refers to the ratio a / b when the length a of the major axis and the length b of the minor axis of the cube or rectangular parallelepiped circumscribing the graphite particles (including secondary particles) are used.

[0016] In this specification, the term "collapse" means that the graphite particles oriented along the vertical direction lose their orientation state.

[0017] In this specification, the "particle size" is the volume-averaged median diameter D50 means.

[0018] <Negative electrode for battery> The negative electrode for a battery of the present disclosure (hereinafter, also simply referred to as "negative electrode") includes a first graphite having an aspect ratio of 2 to 5 and a second graphite having an aspect ratio of 1 to 1.4, and the peak intensity ratio (I 110 / I 002 ) is 0.03 or more, and includes a first negative electrode active material layer and a current collector.

[0019] With the above configuration, even after performing the pressing process performed in the process of manufacturing the electrode, the orientation of the graphite having a high aspect ratio in the negative electrode (graphite having a shape such as a flake shape, a flat plate shape, or an elliptical shape) can be maintained. As a result, a negative electrode for a battery with low electrical resistance is provided. As a result, a battery having a high energy density can be obtained. The reason for obtaining the above effect is presumed as follows. Graphite with a high aspect ratio oriented in the vertical direction in the electrode (especially the surface layer of the electrode) is likely to expand or contract in the in-plane direction during charge and discharge, so it is considered that an ion invasion path into the electrode is easily secured and the resistance becomes low.

[0020] Hereinafter, the configuration of the negative electrode will be described.

[0021] FIG. 1 is a schematic cross-sectional view showing an example of the structure of a negative electrode for a battery according to an embodiment of the negative electrode for a battery of the present disclosure. As shown in FIG. 1, the negative electrode for a battery 100 includes a first negative electrode active material layer 10 and a current collector 20. The first negative electrode active material layer 10 includes a first graphite having a high aspect ratio and a second graphite having a low aspect ratio.

[0022] - First negative electrode active material layer - The first negative electrode active material layer contains first graphite and second graphite. The aspect ratio of the first graphite is 2 to 5. The aspect ratio of the second graphite is 1 to 1.4. When a magnetic field is applied to the first negative electrode active material layer because the aspect ratio of the first graphite is 2 to 5, the first graphite is likely to be oriented in the vertical direction of the negative electrode. Further, since the aspect ratio of the second graphite is 1 to 1.4 and the second graphite is included together with the first graphite in the first negative electrode active material layer, it is easy to suppress the collapse of the first graphite oriented by the magnetic field during pressing. For this reason, the orientation of the first graphite is maintained even after the pressing process. For example, when the aspect ratio of the second graphite is 1, the second graphite is spherical, and the second graphite suppresses the collapse of the first graphite without collapsing.

[0023] The first graphite and the second graphite may be natural graphite or artificial graphite. The natural graphite may be flake graphite or amorphous graphite.

[0024] The shapes of the first graphite and the second graphite are not particularly limited as long as the above aspect ratios are satisfied. Examples of the shape of the first graphite include plate shapes (e.g., flake shape, elliptical shape). Examples of the shape of the second graphite include spherical shapes (e.g., true spherical shape, elliptical spherical shape).

[0025] The particle sizes of the first graphite and the second graphite may be from 0.1 μm to 100 μm.

[0026] The specific surface areas of the first graphite and the second graphite may be from 0.1 m 2 / g to 1,500 m 2 / g.

[0027] In the first negative electrode active material layer, the mass ratio of the second graphite to the first graphite (mass % of the second graphite / mass % of the first graphite) is preferably 30 / 70 to 70 / 30. When the mass ratio of the second graphite to the first graphite (mass % of the second graphite / mass % of the first graphite) is 30 / 70 to 70 / 30, the collapse of the first graphite in the first negative electrode active material layer is more easily suppressed and the orientation is more easily maintained. Therefore, when a battery (cell) is constructed, the capturability and releasability of ions (for example, lithium ions) increase, so the cell resistance decreases and the battery is easily made to have a high capacity.

[0028] In addition to the first graphite and the second graphite, the first negative electrode active material layer may contain a binder and a conductive material (not shown in FIG. 1).

[0029] Examples of the binder include polyvinylidene fluoride (PVDF) / NMP-based, styrene-butadiene rubber (SBR) / aqueous-based, polytetrafluoroethylene (PTFE) / aqueous-based binders, etc. The binder may contain carboxymethyl cellulose (CMC) as a thickener.

[0030] The content of the binder may be 0.1 mass % to 5 mass % with respect to the total amount of the first graphite and the second graphite.

[0031] Examples of the conductive agent include carbon materials such as acetylene black, ketjen black, vapor-grown carbon fiber (VGCF (registered trademark)), and carbon nanotube (CNT).

[0032] The content of the conductive agent may be 0.1 mass % to 5 mass % with respect to the total amount of the first graphite and the second graphite.

[0033] - Current collector - A known current collector may be used. For example, it may be appropriately selected from those made of metal members such as Cu, Al, Fe, Co, Ni, Cr, nickel-plated steel, and stainless steel. As the negative electrode current collector, those made of Cu are preferred.

[0034] The thickness of the current collector is not particularly limited. For example, it may be 0.1 μm to 1,000 μm.

[0035] The negative electrode for a battery of the present disclosure is obtained by providing a first negative electrode active material layer on a current collector. In one embodiment of the negative electrode for a battery of the present disclosure, the first negative electrode active material layer is provided on the current collector. More specifically, the negative electrode for a battery of the present disclosure can be manufactured, for example, by applying a slurry for forming a first negative electrode active material layer containing a first graphite and a second graphite on the current collector, applying a magnetic field, drying, and pressing.

[0036] The slurry can be prepared by kneading a first graphite, a second graphite, a binder, and, if necessary, a conductive agent, a thickener, and the like. The kneading may be performed by a known method. For example, it may be performed using a planetary mixer, a sand mill, a ball mill, a planetary mill, a roll mill, an extruder, or the like.

[0037] The coating may be performed by a known method. For example, it may be performed by a slit die method or a doctor roll method.

[0038] The application of the magnetic field may be performed by a known method. For example, it may be performed using a magnetizing device. By applying a magnetic field to the slurry, the first graphite in the first negative electrode active material layer can be oriented.

[0039] When applying the magnetic field, the strength of the magnetic field is not particularly limited as long as the first graphite in the first negative electrode active material layer is oriented. For example, it may be 0.5 T or more.

[0040] When applying the magnetic field, the direction of the magnetic field is not particularly limited as long as the first graphite in the first negative electrode active material layer is oriented. However, since the orientation of the first graphite becomes a mode suitable for increasing the lithium ion capture property and release property, it is preferable to apply the magnetic field in the plane normal direction of the negative electrode. Thereby, the cell resistance is also likely to decrease, and the lithium ion battery is also likely to have a high capacity.

[0041] Also, drying may be performed by a known method. For example, it may be performed by natural drying, vacuum drying, or heat drying. The drying temperature may be, for example, 80°C to 135°C.

[0042] Also, pressing may be performed by a known method. For example, it may be performed by roll pressing, cold isostatic pressing (CIP), etc. The pressing may be performed, for example, so that the electrode density becomes 1.2 g / cm 3 or the like.

[0043] The peak intensity ratio (I 110 / I 002 ) determined by XRD measurement of the first negative electrode active material layer of the negative electrode for a battery according to the present disclosure is 0.03 or more. Referring to the Inorganic Crystal Structure Database (ICSD), the peak intensity ratio (I 110 / I 002 ) of graphite powder with random orientation is 0.014. Therefore, when the peak intensity ratio (I 110 / I 002 ) is greater than 0.014, the first graphite is oriented in the in-plane direction of the graphene layer structure. For this reason, when the peak intensity ratio (I 110 / I 002 ) is 0.03 or more, in the battery, the capturability and release property of ions (for example, lithium ions) increase, the cell resistance decreases, and the battery is also likely to have a high capacity. XRD measurement is performed using an XRD measuring device (CuK α = 1.5405 Å). The peak intensity ratio (I 110 / I 002 ) is obtained from the diffraction peak intensity I 002 assigned to the plane index (002) (perpendicular to the plane of the graphene structure) near 2θ = 26.3° obtained by XRD measurement, and the diffraction peak intensity I 110 assigned to the plane index (110) (in the plane of the graphene structure) near 2θ = 77.7°.

[0044] An embodiment in which the negative electrode for a battery according to the present disclosure further includes a second negative electrode active material layer that contains the second graphite and does not contain the first graphite between the first negative electrode active material layer and the current collector is also preferable.

[0045] FIG. 2 is a schematic cross-sectional view showing an example of the structure of a negative electrode for a battery according to another embodiment of the negative electrode for a battery of the present disclosure. As shown in FIG. 2, the negative electrode 100 for a battery includes a second negative electrode active material layer 30 between a first negative electrode active material layer 10 and a current collector 20. By further providing the second negative electrode active material layer 30, the diffusibility of ions (for example, lithium ions) is likely to be improved as compared with the case where the negative electrode is composed of only the second negative electrode active material layer. The negative electrode for a battery in FIG. 2 can be manufactured by providing a second negative electrode active material layer on a current collector and further providing a first negative electrode active material layer thereon. In particular, a mode in which the outermost layer, the first negative electrode active material layer, the second negative electrode active material layer, and the current collector are arranged in this order is preferable for the same reason as described above.

[0046] - Second negative electrode active material layer - The second negative electrode active material layer preferably contains second graphite as a negative electrode active material and does not contain first graphite, and more preferably contains only second graphite.

[0047] The second negative electrode active material layer may contain a binder and a conductive agent in addition to the second graphite (not shown in FIG. 2).

[0048] As the binder, the same ones as those exemplified in the first negative electrode active material layer can be used. The content of the binder may be the same as that exemplified in the first negative electrode active material layer.

[0049] As the conductive agent, the same ones as those exemplified in the first negative electrode active material layer can be used. The content of the conductive agent may be the same as that exemplified in the first negative electrode active material layer.

[0050] <Battery> The battery of the present disclosure includes the negative electrode for a battery. The battery of the present disclosure preferably has a laminated structure in which the negative electrode and the positive electrode are laminated via an electrolyte layer. The battery of the present disclosure is preferably a secondary battery, and more preferably a lithium ion secondary battery.

[0051] - Positive electrode - The positive electrode includes a positive electrode active material layer and a current collector.

[0052] The positive electrode active material layer preferably contains a positive electrode active material, a conductive agent, and a binder.

[0053] Examples of the positive electrode active material include layered, olivine-type, and spinel-type compounds, such as lithium composite oxides. Examples of the lithium composite oxide include lithium cobalt oxide, lithium nickel oxide, lithium manganate, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 and the like. Examples of the layered lithium composite oxide include compounds represented by the composition formula LiNi x Me 1 y Me 2 z O 2 (wherein, Me 1 includes Co, Fe, Mn, Mo, etc., Me 2 includes Al, Ga, Si, Mg, Ti, Ba, Zr, Y, etc., x, y, and z are integers of 0 or more, and x + y + z = 1). Examples of the olivine-type lithium composite oxide include LiFePO 4 、LiFe 1-x Mn x PO 4 (x is an integer of 0 or more), etc. Examples of the spinel-type lithium composite oxide include LiMn 2 O 4 and the like. The lithium composite oxide may contain at least one selected from the group consisting of F, Cl, N, S, Br, and I.

[0054] The shape of the positive electrode active material is not particularly limited. For example, it may be spherical (e.g., true spherical, ellipsoidal, etc.), fibrous, or the like.

[0055] The particle size of the positive electrode active material may be 0.1 μm to 30 μm.

[0056] The specific surface area of the positive electrode active material may be from 0.1 m 2 / g to 100 m 2 / g.

[0057] As the conductive agent, the same ones as those exemplified for the negative electrode can be used. The content of the conductive agent may be 3% by mass to 5% by mass with respect to the positive electrode active material.

[0058] As the binder, the same ones as those exemplified for the negative electrode can be used. The content of the binder may be 0.1% by mass to 5% by mass with respect to the positive electrode active material.

[0059] - Current collector - As the current collector, the same ones as those exemplified for the negative electrode can be used. As the positive electrode current collector, those made of Al are preferred.

[0060] The thickness of the current collector is not particularly limited either. For example, it may be from 0.1 μm to 1,000 μm.

[0061] - Electrolyte layer - The electrolyte layer may include a solid electrolyte layer or a separator and an electrolytic solution.

[0062] When the electrolyte layer is a solid electrolyte layer, examples of the solid electrolyte include lithium lanthanum zirconate, LiPON, Li 1+X Al X Ge 2-X (PO4) 3 , oxide solid electrolytes such as Li - SiO - based glass, Li - Al - S - O - based glass; Li 2 S - P 2 S 5 , Li 2 S - SiS 2 , LiI - Li 2 S - SiS 2 , LiI - Si 2 S - P 2 S 5 , Li 2 S - P 2 S 5 - LiI - LiBr, LiI - Li 2 S - P 2S 5 , LiI - Li 2 S - P 2 O 5 , LiI - Li 3 PO 4 -P 2 S 5 , Li 2 S - P 2 S 5 -GeS 2 Examples of the sulfide solid electrolyte include those such as the above. The solid electrolyte layer can be obtained by pressing the solid electrolyte.

[0063] When the electrolyte layer includes a separator and an electrolytic solution, examples of the separator include resin sheets such as polyethylene (PE) and polypropylene (PP). Further, the electrolytic solution contains a predetermined electrolyte and a solvent. Examples of the predetermined electrolyte include LiPF 6 , LiBF 4 , LiAsF 6 , Li(CF 3 SO 2 ) 2 N, Li(C 2 F 5 SO 2 ) 2 N, LiTaF 6 , LiClO 4 , LiCF 3 SO 3 and the like.

[0064] Examples of the solvent include cyclic carbonate solvents such as ethylene carbonate (EC) and propylene carbonate (PC); chain carbonate solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC). The concentration of the electrolytic solution may be 0.1 - 1 mol / L.

Example

[0065] Hereinafter, the present disclosure will be specifically described by way of examples, but the present disclosure is not limited only to the following examples.

[0066] <Example 1> -Manufacture of negative electrode - Using a first graphite with an aspect ratio of 2 to 5 and a second graphite with an aspect ratio of 1 to 1.4, carboxymethyl cellulose (CMC) as a thickener and styrene butadiene rubber (SBR) as a binder were added to a graphite mixture with a mixing ratio of first graphite:second graphite = 70:30 (mass ratio) so that the ratio of first graphite and second graphite:CMC:SBR = 98:1:1 (mass ratio). Further, water was added and kneaded to prepare a slurry for forming a first negative electrode active material layer. Next, the above slurry was coated on a current collector (Cu foil) so that the basis weight was 20 mg / cm 2 When performing an orientation treatment on this, a magnetic field of 0.5 T or more was applied in the plane normal direction of the first negative electrode active material layer. Next, the first negative electrode active material layer was dried and pressed to a density of 1.2 g / cm 3 to fabricate a negative electrode.

[0067] -Evaluation of Negative Electrode- (XRD Measurement) Regarding the fabricated negative electrode, the orientation of the first graphite in the first negative electrode active material layer was evaluated by the peak intensity ratio obtained by XRD measurement. XRD measurement was performed using an XRD measurement apparatus (CuK α = 1.5405 Å). The orientation of the first graphite was evaluated by the ratio (I 002 ) of the diffraction peak intensity I 110 attributed to the plane index (002) (plane normal direction of the graphene structure) near 2θ = 26.3° and the diffraction peak intensity I 110 attributed to the plane index (110) (in-plane direction of the graphene structure) near 2θ = 77.7°. The results are shown in Table 1. 002 )

[0068] (Cell Resistance) The performance of the negative electrode was evaluated using a half cell with a Li metal as the counter electrode. Specifically, the negative electrode was cut out into a 5 cm square (excluding the current collector tab), opposed to the Li metal through a 20-μm-thick three-layer separator of PP / PE / PP, and 1 M LiPF 6A half cell was fabricated by laminating and sealing with EC / EMC = 30 / 70 (volume %). This half cell was charged and discharged in the range of 0.05 V to 1.2 V (vs. Li / Li + ), and SOC100% was defined based on the capacity at that time. After adjusting the cell to SOC50%, it was charged at 1C for 10 minutes, and the cell resistance was calculated by dividing the absolute value of the voltage change (before evaluation, open circuit voltage - after 10 minutes, closed circuit voltage) by the 1C current value. The results are shown in Table 1. In addition, each resistance value is shown as a standard value based on the resistance of Comparative Example 2.

[0069] <Example 2> In Example 1, a negative electrode was fabricated and evaluated in the same manner as in Example 1, except that a first negative electrode active material layer having the composition ratio shown in Table 1 was provided on the current collector. The results are shown in Table 1.

[0070] <Example 3> In Example 1, a negative electrode was fabricated and evaluated in the same manner as in Example 1, except that a first negative electrode active material layer having the composition ratio shown in Table 1 was provided on the current collector. The results are shown in Table 1.

[0071] <Example 4> Graphite (second graphite) with an aspect ratio of 1 to 1.4, carboxymethyl cellulose (CMC) as a thickener, and styrene-butadiene rubber (SBR) as a binder were added so that the ratio of graphite:CMC:SBR = 98:1:1 (mass ratio), and water was added and kneaded to prepare a slurry for forming a second negative electrode active material layer. In Example 1, a slurry for forming a second negative electrode active material layer was coated on a current collector (Cu foil), and further, a negative electrode was fabricated and evaluated in the same manner as in Example 1, except that a first negative electrode active material layer having the composition ratio shown in Table 1 was provided thereon. The results are shown in Table 1.

[0072] <Comparative Example 1> In Example 1, a negative electrode was fabricated and evaluated in the same manner as in Example 1, except that a first negative electrode active material layer having the composition ratio shown in Table 1 was provided on the current collector and no magnetic field was applied. The results are shown in Table 1.

[0073] <Comparative Example 2> In Example 1, a negative electrode was produced and evaluated in the same manner as in Example 1, except that the first negative electrode active material layer having the composition ratio shown in Table 1 was provided on the current collector. The results are shown in Table 1.

[0074] <Comparative Example 3> In Example 1, a negative electrode was produced and evaluated in the same manner as in Example 1, except that the first negative electrode active material layer having the composition ratio shown in Table 1 was provided on the current collector. The results are shown in Table 1.

[0075] <Comparative Example 4> In Example 1, a negative electrode was produced and evaluated in the same manner as in Example 1, except that the first negative electrode active material layer having the composition ratio shown in Table 1 was provided on the current collector. The results are shown in Table 1.

[0076]

Table 1

[0077] As shown in Table 1, in the first negative electrode active material layer, when the mass ratio of the second graphite to the first graphite (mass % of the second graphite / mass % of the first graphite) is 30 / 70 to 70 (Examples 1 to 4), when the second graphite is not included, or when the mass ratio of the first graphite and the second graphite is outside the above range (Comparative Examples 2 to 4), I 110 / I 002 has increased significantly, and it was confirmed that the collapse of the first graphite due to pressing was suppressed. I 110 / I 002 The increase in is correlated with the decrease in cell resistance. In Examples 1 to 4, a 20% to 30% decrease in cell resistance was observed compared to the case where the second graphite was not included (Examples 1 to 4, Comparative Example 2). On the other hand, in Comparative Example 3 where the mass ratio of the second graphite to the first graphite (mass % of the second graphite / mass % of the first graphite) is 10 / 90, I 110 / I 002 showed no significant increase. Also, in Comparative Example 4 where the mass ratio of the second graphite to the first graphite (mass % of the second graphite / mass % of the first graphite) is 90 / 10, I 110 / I002 There was no significant increase. In the case of Comparative Example 4, it is considered that the proportion of the first graphite oriented by the magnetic field itself is small. Also, although the first graphite once aligns when a magnetic field is applied (Comparative Examples 1 and 2), I 110 / I 002 is the I of graphite powder with random orientation 110 / I 002 Since it is smaller than 0.014, it was also found that the first graphite is oriented in a collapsed state in the in-plane direction of the negative electrode by pressing.

Explanation of symbols

[0078] 100 Negative electrode for battery 1 First graphite 2 Second graphite 10 First negative electrode active material layer 20 Current collector 30 Second negative electrode active material layer

Claims

1. The first graphite having an aspect ratio of 2 to 5 and the second graphite having an aspect ratio of 1 to 1.4, and the peak intensity ratio (I １１０ / I ００２ ) determined by XRD measurement is 0.03 or more, the first negative electrode active material layer, A current collector, A negative electrode for a battery comprising the same.

2. The negative electrode for a battery according to Claim 1, wherein in the first negative electrode active material layer, the mass ratio of the second graphite to the first graphite is 30 / 70 to 70 / 30.

3. The negative electrode for a battery according to Claim 1, further comprising a second negative electrode active material layer containing the second graphite and not containing the first graphite between the first negative electrode active material layer and the current collector.

4. The negative electrode for a battery according to Claim 3, having the first negative electrode active material layer as the outermost layer.

5. A battery comprising the negative electrode for a battery according to any one of Claims 1 to 4.

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