JP2010092649A - Anode active material for lithium-ion secondary battery and anode - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an anode active material for a lithium-ion secondary battery with high electrode density, excellent permeability of electrolyte solution, with little loss of capacity, and with high cycle performance. <P>SOLUTION: This invention relates to a mixture of two kinds of graphite powder A, B of equivalent crushability and different shapes with a weight mixture ratio of: A=20 to 80%, B=20 to 80%, and A+B=100%, thereby obtaining cycle characteristics in the figure, wherein: A is a scale-like natural graphite and binder pitch calcinated and graphitized, with a relation of a pressing pressure P (MPa) and an electrode density D (g/cm<SP>3</SP>) of D=0.003 to 0.007P within a range of the pressing pressure of 30 to 150 MPa, a tap density of 0.4 to 0.9 g/cm<SP>3</SP>, an oil absorption of 50 to 90 ml/100g, and a roundness of less than 0.91; and B is a spherical natural graphite coated and dipped with pitch and calcinated to be graphitized, with a relation of a pressing pressure P (MPa) and an electrode density D (g/cm<SP>3</SP>) of D=0.003 to 0.007P, a tap density of 0.9 to 1.4 g/cm<SP>3</SP>, an oil absorption of 30 to 45 ml/100g, and a roundness of 0.91 or more. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a carbon-based negative electrode active material for a lithium ion secondary battery used for a notebook computer, a mobile phone, etc., and relates to a negative electrode and a negative electrode active material that have a high capacity, have a small capacity loss, and can be rapidly charged and discharged.

Lithium ion secondary batteries are often used in portable devices such as notebook computers, mobile phones, and video cameras as high-capacity, high-voltage, small and lightweight secondary batteries.
High performance of each part and material of the lithium ion secondary battery has been attempted, but in particular, the density of the negative electrode material has been demanded as one that affects the performance of the battery.

Japanese Patent No. 2983003 Japanese Patent No. 3588354 Japanese Patent No. 3716830

Carbon or graphite is used as a negative electrode material for lithium ion secondary batteries, but carbonaceous materials are generally hard and difficult to increase in density, which is essential for improving the performance of batteries. Is soft and easily densified. Moreover, in order to accelerate the penetration of the battery electrolyte into the electrode material, it is necessary to ensure voids. However, increasing the density and ensuring the voids are contradictory requirements, satisfying both. It was very difficult to obtain a high performance negative electrode material.
INDUSTRIAL APPLICABILITY The present invention provides a negative electrode active material for a lithium ion secondary battery that can have a high electrode density, is excellent in electrolyte permeability, has little capacity loss due to charge / discharge, and has good cycle performance, and uses the same It is an object of the present invention to provide a high performance negative electrode.

  A mixture of two types of A and B graphite powders having equal ease of crushing (compressibility), different oil absorption and circularity of the powder, graphite powder A being 20 to 80% by weight, graphite powder B being 20 to 80% The negative electrode for a lithium ion battery and the negative electrode active material have solved the problem by setting the weight% to be graphite A + graphite B = 100%.

Details of the graphite powder A and the graphite powder B are as follows.
Graphite powder A:
The graphite powder A is a graphite powder obtained by pulverizing a block obtained by mixing a flaky natural graphite powder and a binder pitch, obtaining a molded body by a known molding method, and firing and graphitizing the block. Alternatively, the graphite powder A is a graphite powder obtained by pulverizing a graphite block made of a known filler / binder material made of coke and binder pitch. For example, Patent Document 1 (Patent No. 2983003), Patent Document 2 (Patent No. 2) No. 3588354 gazette).
Specifically, for example, an isotropic artificial graphite block manufactured by Shin Nippon Techno Carbon Co., Ltd., a molded artificial graphite block, or an artificial graphite block by extrusion molding can be pulverized.
The relationship between the press pressure P (MPa) and the electrode density D (g / cm ³ ) when a pressure is applied to an electrode coated with graphite powder A and coated on a metal current collector and dried is as follows. D = 0.003 to 0.007P, graphite powder A has a tap density of 0.4 to 0.9 (g / cm ³ ), an oil absorption of 50 to 90 ml / 100 g, and a circularity of 0. Less than .91, and the D90 / D10 ratio of the particle size distribution is 3.5 to 7.0.

  The graphite powder A is subjected to a treatment such as sizing with an air separator, a vibrating sieve, an ultrasonic sieve, or the like, surface modification by mechanochemical treatment, shape control or refiring, re-graphitization, or the like as necessary.

Since graphite powder A is highly graphitized, it has very high crystallinity, and 2 parts by weight of organic binder SBR (Styrene Butadiene Rubber) and CMC (Carboxy Methyl Cellulose) are used for 100 parts by weight of this powder. Then, an electrode having an electrode density of 1.6 g / cm ³ and a thickness of 60 μm is formed on the copper foil, Li metal is used as a counter electrode, and the electrodes are opposed to each other through a separator, and 1M LiPF6 / EC: MEC (1: 2) is electrolyzed. When a liquid is added to form a coin cell and a charge / discharge test is performed, a discharge capacity of about 350 to 360 mAh / g and an efficiency of 93 to 95% are shown.

Graphite powder A is very soft because it is highly graphitized, and when it is molded by increasing the press pressure, the electrode density shows a high value. However, if the electrode density exceeds 1.7 g / cm ³ , the gap into which the electrolytic solution should enter is crushed, so that the penetration rate of the electrolytic solution is slowed down, and a portion that does not partially contribute to charging / discharging occurs in the electrode. Yes, it does not substantially function as an electrode and cannot be used as an electrode. Therefore, with this graphite powder A alone, it is practically impossible to use an electrode density exceeding 1.7 g / cm ³ .

Graphite powder B:
The graphite powder B is a graphite powder obtained by coating spherical natural graphite with a pitch, firing, and further graphitizing, and can be manufactured by, for example, a method described in Patent Document 3 (Japanese Patent No. 3716830). Alternatively, scale-like natural graphite can be mechanically shaped into a roughly spherical shape, coated with a coal-based or petroleum-based pitch, fired at 700 to 1300 ° C., and further graphitized.
An electrode obtained by adding a binder to graphite powder B and applying and drying it on a metal current collector has a relationship between the press pressure P (MPa) and the electrode density D (g / cm ³ ) when pressed, and the press pressure is 30. In the range of ~ 150 MPa, D = 0.003 to 0.007 P, the graphite powder B has a tap density of 0.9 to 1.4 g / cm ³ , an oil absorption of 30 to 45 ml / 100 g, and a circularity of 0.91 or more, and the D90 / D10 ratio of the particle size distribution is 2.0 to 3.5. Using 5 parts by weight of an organic binder PVdF (Poly Vinylidene di-Fluoride) with respect to 100 parts by weight of this graphite powder B, an electrode having an electrode density of 1.6 g / cm ³ and a thickness of 60 μm is formed on a copper foil to form Li metal. When a charge / discharge test is performed by adding a 1M LiPF6 / EC: MEC (1: 2) electrolyte solution to face each other through a separator and performing a charge / discharge test, a discharge capacity of about 345 to 355 mAh / g, an efficiency of 90 to 95% is indicated.

Since graphite powder B has a narrow particle size distribution, that is, a D90 / D10 ratio of about 2.0 to 3.5, at low electrode density (up to about 1.6 g / cm ³ ), a sufficient space for the electrolyte to flow in is ensured. ing. However, since the whole is graphite, the particles are soft, and when the press pressure is increased to increase the electrode density, the particles are deformed and the electrode density is likely to increase. At a low electrode density, the particles are mainly in point contact with each other. However, as the particles are consolidated, it is considered that a conductive network is formed in a form including line contact and surface contact in addition to point contact due to deformation of the particles.
When the press molding pressure is further increased and the electrode density exceeds 1.7 g / cm ³ , the deformation of the graphite particles increases, and the voids into which the electrolyte solution should enter are crushed. Therefore, there is a portion that does not partially contribute to charging / discharging, and it does not substantially function as an electrode and cannot be put to practical use. That is, the graphite powder B alone cannot produce a practical electrode having a high density exceeding an electrode density of 1.7 g / cm ³ .

Graphite powder A can be subjected to surface modification and shape control by mechanochemical treatment as necessary, but this can disturb the crystal structure of the particle surface to suppress reaction with the electrolyte, It is possible to increase the tap density and increase the porosity, that is, the oil absorption amount.
On the other hand, graphite powder B first mechanically shapes scaly natural graphite into a substantially spherical shape, which is also a form of mechanochemical treatment.
The equipment used for these treatments must be capable of applying a strong mechanical external force. For example, a mechano-fusion system (manufactured by Hosokawa Micron Corporation), a hybridization system (manufactured by Nara Machinery Co., Ltd.), Newgra Machine (Manufactured by Seishin Co., Ltd.), kryptron (Earth Technica Co., Ltd.), Henschel mixer (Mitsui Mine Co., Ltd.), etc. can be used.

  Oil absorption is one of the characteristic factors representing the performance of carbon black, pigments and other powders. Linseed oil is added to the powder little by little, and the state of the powder is confirmed while kneading, finding a point that forms a lump from the dispersed state, and the oil volume (ml) at that time is the oil absorption. . The amount of oil absorption varies greatly depending on the properties of the powder, but the influence of the size and shape of the particles is particularly great. The smaller the particle size, the more irregular the shape, and the greater the porosity, the greater the amount of oil absorption.

In particular, in carbon black, the porosity between individual aggregates (aggregates) has a positive correlation with the structure (a form in which particles are connected like a bunch of grapes), so DBP (Di-butyl is a kind of plasticizer). substantially) absorption of phthalate (cm ³ / 100g) defined in JIS K 6217 indirectly have quantified the structure as. For example, in general carbon black, the oil absorption (DBP absorption) increases as the particle size decreases and the specific surface area increases. In the case of acetylene black, it is far from other carbon blacks having the same specific surface area. Has a large oil absorption. This is said to suggest that the development of the structure of acetylene black is so large that oil is absorbed not only in the particle surface but also in the voids in the network structure. In other words, it can be said that the oil absorption changes depending on the porosity of the particles.

  The oil absorption amount measuring method in the present invention was performed using linseed oil by an absorption amount measuring device S-410 type manufactured by Asahi Research Institute in accordance with JIS K 6217.

  The circularity is measured by using a flow type particle image analyzer FPA-3000S manufactured by Sysmex Corporation. Each of the particles dispersed in the liquid is photographed (number of analysis: 1800 to 8000 points), and the circularity is equal to the particle area. The value obtained by dividing the perimeter by the perimeter of the particle was taken as the circularity.

  The tap density (bulk density) was calculated from the volume of the sample after tapping 700 times at a stroke of 17 mm by putting 60 g of the sample into a 100 ml graduated cylinder, setting it in a self-made tap density measuring instrument equipped with a cam inside. .

The specific surface area was measured by adsorption / desorption of nitrogen gas, and a measuring device, an automatic specific surface area / pore distribution measuring device ASAP2405 manufactured by Micromeritics was used.
The specific surface area was determined by the BET multipoint method in which the amount of adsorbed gas obtained from the adsorption isotherm was evaluated as a monolayer and the surface area was calculated.

  The average particle size and particle size distribution were measured using an LMS-30 system manufactured by Seishin Enterprise Co., Ltd., in a state where ultrasonic dispersion was performed using water as a dispersion medium and a small amount of surfactant as a dispersant. .

In the electrochemical charge / discharge test, 100 parts by weight of the negative electrode active material was prepared by adjusting 2 parts by weight of each of SBR and CMC as binders to prepare an aqueous slurry, and using a doctor blade on the copper foil to obtain a thickness. After applying to 160 μm, drying at 120 ° C. and applying a roll press, a punched electrode was formed at φ12. The negative electrode after pressing had a thickness of 60 μm.
Lithium metal was used as a counter electrode, and the electrodes were made to face each other through a separator, and then an electrolyte solution of 1M LiPF ₆ / EC: MEC (1: 2) was added to form a coin cell, which was subjected to a charge / discharge test.
Charging / discharging conditions are as follows. First, constant current charging is performed at a current value of 0.5 mA / cm ² , then switching to constant voltage charging after the voltage value reaches 0.01 V, and charging is performed until the current value decreases to 0.01 mA / cm ^2. Went. After completion of charging, constant current discharging was performed at a current value of 0.5 mA / cm ² , and discharging was terminated when the voltage value reached 1.5V.

  The pore distribution of the coating film was measured by mercury porosimetry using Shimadzu Autopore Model 9520. After the electrode coated with the negative electrode material on both sides of the copper foil was cut into strips of about 125 x 25 mm, 6-7 sheets were taken in a standard cell and measured under conditions of an initial pressure of about 20 kPa (about 25 psia, pore diameter of about 70 μm) .

By mixing graphite powders A and B having the same shape and different shapes, a negative electrode active material having excellent electrolyte permeability can be obtained even at a high electrode density of 1.7 g / cm ³ or more. Therefore, a negative electrode for a lithium ion secondary battery with low capacity loss due to charging and discharging and good cycle performance can be produced at low cost.

  Next, embodiments of the present invention will be described in the following examples, but the present invention is not limited to these examples.

Example
<Graphite powder (A)>
A1: Coke powder obtained by pulverizing coke having a thermal expansion coefficient of 5.3 × 10 ⁻⁶ (1 / ° C.) to an average particle size (D50) = 10 μm and a binder pitch were heated and mixed and molded, and the molded body was fired and graphitized. . This was pulverized and further mechanically processed at a Henschel mixer peripheral speed of 20 m / s to obtain graphite powder (A1).
The obtained powder had D50 = 17.1 μm, Dtop = 91.1 μm, BET specific surface area = 3.89 m ² / g, tap density = 0.81 g / cm ^3, and oil absorption = 78.8 ml / 100 g.
Further, the relationship between the press pressure P (MPa) and the electrode density D (g / cm ³ ) was D = 0.0001P + 1.41.

A2: Coke powder obtained by crushing coke with a coefficient of thermal expansion of 1.08 × 10 ^-6 (1 / ° C) to an average particle size (D50) = 13 μm and binder pitch were heated and mixed and molded. . This was pulverized and further mechanically processed at a Henschel mixer peripheral speed of 40 m / s to obtain graphite powder (A2).
The obtained graphite powder had D50 = 15.3 μm, Dtop = 76.8 μm, BET specific surface area = 3.63 m ² / g, tap density = 0.82 g / cm ^3, and oil absorption = 61.8 ml / 100 g.
The relationship between the press pressure P (MPa) and the electrode density D (g / cm ³ ) was D = 0.655P + 1.33.

A3: Coke powder obtained by pulverizing coke having a thermal expansion coefficient of 5.3 × 10 ⁻⁶ (1 / ° C.) to an average particle size (D50) = 10 μm and a flake-like natural graphite powder having an average particle size (D50) = 16 μm The mixed powder and binder pitch were heated and mixed and molded, and the molded body was fired and graphitized. This was pulverized and further mechanically processed at a Henschel mixer peripheral speed of 40 m / s to obtain graphite powder (A3).
The obtained graphite powder had D50 = 21.7 μm, Dtop = 91.1 μm, BET specific surface area = 3.57 m ² / g, tap density = 0.81 g / cm ^3, and oil absorption = 59.7 ml / 100 g.
The relationship between the press pressure P (MPa) and the electrode density D (g / cm ³ ) was D = 0.588P + 1.38.

A4: Average particle diameter (D50) = scale-like natural graphite powder pulverized to 16 μm and binder pitch were heated and mixed and molded, and the molded body was fired and graphitized. This was pulverized and further mechanically processed at a Henschel mixer peripheral speed of 40 m / s to obtain graphite powder (A4).
The obtained graphite powder had D50 = 19.4 μm, Dtop = 64.8 μm, BET specific surface area = 0.80 m ² / g, tap density = 0.80 g / cm ^3, and oil absorption = 58.2 ml / 100 g.
The relationship between the press pressure P (MPa) and the electrode density D (g / cm ³ ) was D = 0.068P + 1.45.

<Graphite powder (B)>
B1: Spherical natural graphite having an average particle size (D50) = 11 μm and binder pitch were mixed by heating, and this was fired and graphitized to obtain graphite powder (B1).
The obtained graphite powder had D50 = 12.7 μm, Dtop = 38.9 μm, BET specific surface area = 1.36 m ² / g, tap density = 1.18 g / cm ^3, and oil absorption = 35.6 ml / 100 g.
Further, the relationship between the press pressure P (MPa) and the electrode density D (g / cm ³ ) was D = 0.636P + 1.40.

B2: Spherical natural graphite having an average particle diameter (D50) = 15 μm and a binder pitch were mixed by heating, and this was fired and graphitized to obtain graphite powder (B2).
The obtained graphite powder had D50 = 17.5 μm, Dtop = 54.6 μm, BET specific surface area = 1.20 m ² / g, tap density = 1.20 g / cm ^3, and oil absorption = 38.3 ml / 100 g.
The relationship between the press pressure P (kN) and the electrode density D (g / cm ³ ) was D = 0.007P + 1.36.

B3: Spherical natural graphite having an average particle size (D50) = 22 μm and a binder pitch were mixed by heating, and this was fired and graphitized to obtain graphite powder (B3).
The obtained graphite powder had D50 = 24.3 μm, Dtop = 64.8 μm, BET specific surface area = 0.81 m ² / g, tap density = 1.13 g / cm ^3, and oil absorption = 38.6 ml / 100 g.
Further, the relationship between the press pressure P (MPa) and the electrode density D (g / cm ³ ) was D = 0.0005P + 1.40.

Example 1
Graphite powder (A1) and graphite powder (B2) were mixed at a weight ratio of A1: B2 = 3: 7.
The obtained powder had D50 = 17.1 μm, Dtop = 64.8 μm, BET specific surface area = 1.85 m ² / g, tap density = 1.07 g / cm ^3, and oil absorption = 46.6 ml / 100 g.

Example 2
Graphite powder (A1), graphite powder (A2) and graphite powder (B2) were mixed at a weight ratio of A1: A2: B2 = 3: 2: 5.
The obtained powder had D50 = 17.1 μm, Dtop = 64.8 μm, BET specific surface area = 2.55 m ² / g, tap density = 0.96 g / cm ^3, and oil absorption = 55.2 ml / 100 g.

Example 3
Graphite powder (A1), graphite powder (A2), and graphite powder (B2) were mixed at a ratio of A1: A2: B2 = 3: 4: 3.
The obtained powder had D50 = 17.7 μm, Dtop = 76.8 μm, BET specific surface area = 2.76 m ² / g, tap density = 0.93 g / cm ³ and oil absorption = 58.3 ml / 100 g.

Example 4
Graphite powder (A1), graphite powder (A2), graphite powder (B2) and graphite powder (B3) are mixed at a weight ratio of A1: A2: B1: B2: B3 = 3: 4: 1: 1: 1. did.
The obtained powder had D50 = 17.4 μm, Dtop = 76.8 μm, BET specific surface area = 2.79 m ² / g, tap density = 0.94 g / cm ^3, and oil absorption = 57.2 ml / 100 g.

Example 5
Graphite powder (A1), graphite powder (A2), and graphite powder (B1) were mixed at a weight ratio of A1: A2: B1 = 3: 4: 3.
The obtained powder had D50 = 15.8 μm, Dtop = 76.8 μm, BET specific surface area = 2.93 m ² / g, tap density = 0.94 g / cm ³ and oil absorption = 55.9 ml / 100 g.

Example 6
Graphite powder (A1), graphite powder (B1), and graphite powder (B2) were mixed at a weight ratio of A1: B1: B2 = 3: 3.5: 3.5.
The obtained powder had D50 = 15.6 μm, Dtop = 64.8 μm, BET specific surface area = 2.03 m ² / g, tap density = 1.05 g / cm ^3, and oil absorption = 49.5 ml / 100 g.

Example 7
Graphite powder (A2) and graphite powder (B1) were mixed at a weight ratio of A2: B1 = 6: 4 to obtain the desired product.
The obtained powder had D50 = 14.2 μm, Dtop = 54.6 μm, BET specific surface area = 2.80 m ² / g, tap density = 1.01 g / cm ^3, and oil absorption = 52.4 ml / 100 g.

Example 8
Graphite powder (A2), graphite powder (B1), and graphite powder (B2) were mixed at a weight ratio of A2: B1: B2 = 5: 3: 2.
The obtained powder had D50 = 14.9 μm, Dtop = 54.6 μm, BET specific surface area = 2.67 m ² / g, tap density = 1.03 g / cm ^3, and oil absorption = 50.1 ml / 100 g.

Example 9
Graphite powder (A2), graphite powder (B1), and graphite powder (B2) were mixed at a weight ratio of A2: B1: B2 = 4: 3: 3.
The obtained powder had D50 = 15.1 μm, Dtop = 54.6 μm, BET specific surface area = 2.33 m ² / g, tap density = 1.06 g / cm ^3, and oil absorption = 47.8 ml / 100 g.

Example 10
Graphite powder (A3) and graphite powder (B2) were mixed at a weight ratio of A3: B2 = 3: 7.
The obtained powder had D50 = 17.3 μm, Dtop = 76.8 μm, BET specific surface area = 1.94 m ² / g, tap density = 1.02 g / cm ³ and oil absorption = 44.7 ml / 100 g.

Example 11
Graphite powder (A4) and graphite powder (B2) were mixed at a weight ratio of A4: B2 = 3: 7.
The obtained powder had D50 = 18.1 μm, Dtop = 64.8 μm, BET specific surface area = 1.88 m ² / g, tap density = 1.03 g / cm ^3, and oil absorption = 44.3 ml / 100 g.

Table 1 shows a list of powder characteristics of graphite particles A, and Table 2 shows the characteristics of graphite particles B.
According to Table 1, it can be seen that the graphite particles A have a larger particle size distribution spread (D90 / D10), a larger oil absorption, and a lower circularity than the graphite particles B.

Table 3 shows a list of the powder physical properties and the pore volume and porosity when the electrode density is 1.8 g / cm ³ . In all the examples, a porosity of 15% or more was maintained even in a high-density electrode of 1.8 g / cm ³ .

In Table 4, when a single graphite powder (A1 to B3) is used as an example and a comparative example,
The initial charge / discharge characteristics and cycle characteristics at an electrode density of 1.7 g / cm ³ or more are shown. The cycle characteristics are indicated by the capacity retention rate after 30 cycles with respect to the initial cycle.
In each of the examples, a high capacity retention rate of 97 to 99% was exhibited without cycle deterioration even in a high-density electrode of 1.7 g / cm ³ or more. On the other hand, the single graphite powder of A1 to B3 was able to obtain only a low cycle capacity maintenance rate of less than 80%.

FIG. 1 shows the measurement results of cycle characteristics at an electrode density of 1.8 g / cm ³ .
Example 1 shows good cycle characteristics with no reduction in capacity even when the charge / discharge cycle is repeated at an electrode density of 1.8 g / cm ³ .
On the other hand, the graphite powder A and the graphite powder B which were not mixed had a large capacity drop after repeated charge and discharge, and it was confirmed that the cycle characteristics of the mixture of the graphite powder A and the graphite powder B of the present invention were improved.

An electrode lithium ion secondary battery having a high electrode density of 1.7 g / cm ³ or more by mixing graphite powders having different characteristics is excellent in capacity, efficiency, and cycle characteristics.

The graph of the cycle characteristic measurement result of the lithium ion secondary battery using the electrode of this invention in an electrode density of 1.8 g / cm < ³ >.

Claims (4)

A mixture of graphite powders having the same ease of crushing and different shapes, wherein the weight mixing ratio of graphite powder A and graphite powder B having the following characteristics is A = 20-80%, B = 20-80%, and A + B = 100% negative electrode active material for a lithium ion secondary battery.
Graphite powder A: flaky natural graphite and binder pitch or coke and binder pitch, calcined, and graphitized graphite block is pulverized. A binder is added to this graphite powder and applied to a metal current collector. The relationship between the press pressure P (MPa) and the electrode density D (g / cm ³ ) in the prepared electrode is such that D = 0.003 to 0.007P and the tap density is 0.4 to 0.4 when the press pressure is in the range of 30 to 150 MPa. Graphite powder having 0.9 g / cm ³ , oil absorption of 50 to 90 ml / 100 g, and circularity of less than 0.91.
Graphite powder B: spherical natural graphite coated with pitch, fired and graphitized,
The relationship between the press pressure P (MPa) and the electrode density D (g / cm ³ ) of the electrode obtained by adding a binder to the graphite powder and applying and drying to a metal current collector is as follows. = 0.003 to 0.007 P, graphite powder having a tap density of 0.9 to 1.4 g / cm ³ , an oil absorption of 30 to 45 ml / 100 g, and a circularity of 0.91 or more.
The circularity is a value obtained by dividing the circumference of a circle having the same area as the particle area by the particle circumference. 2. The negative electrode active material for a lithium ion secondary battery according to claim 1, wherein the graphite powder has an average particle diameter D50 of 10 to 20 μm and D90 / D10 of each graphite powder satisfies the following conditions.
Graphite powder A: Graphite powder having a D90 / D10 ratio of 3.5 to 7.0.
Graphite powder B: Graphite powder having a D90 / D10 ratio of 2.0 to 3.5. A negative electrode active material for a lithium ion secondary battery according to any one of the graphite powder mixtures according to claim 1, a binder is added to a metal current collector, dried, pressed, and the electrode density is 1.7 g / cm. ³ or more negative electrode for lithium ion secondary battery. 4. A negative electrode for a lithium ion secondary battery having a pore volume of 0.045 ml / g or more and a porosity of 12% or more in an electrode coated, dried and pressed on the metal current collector of claim 3.

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