JP2016110953A - Graphite particle composition, manufacturing method thereof, negative electrode and power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology capable of applying cushioning properties to a graphite particle-polymer composite.SOLUTION: A manufacturing method of a graphite particle composition includes an action step of causing a graphite particle, an aromatic monomer vinyl copolymer including a vinyl aromatic monomer unit represented by a formula (1) of (CH-CHX) and a basic monomer unit represented by a formula (2) of (CH-CHX) and a treatment agent represented by a formula (3) of L-R-Lto act (Xin the formula (1) represents a phenyl group, a naphthyl group and an anthracenyl group or a pyrenyl group and these groups may also have substituent groups, Xin the formula n(2) represents organic groups containing N and/or P and these groups may also have substituent groups, R in the formula (3) is an alkyl chain of which the carbon number is equal to or more than 2, Land Lare desorption groups, (n) is 0 or 1, and Land Lmay be the same or may also be different).SELECTED DRAWING: None

Description

  The present invention includes a graphite particle composition containing graphite particles and an aromatic vinyl copolymer adsorbed on the graphite particles, a method for producing the graphite particle composition, a negative electrode containing the graphite particle composition, and the negative electrode The present invention relates to a power storage device.

  Graphite particles have various excellent characteristics such as excellent heat resistance, chemical resistance, mechanical strength, thermal conductivity and conductivity, lubricity and light weight. On the other hand, the graphite particles are likely to aggregate, and in particular, it is difficult to uniformly disperse them in a fluid.

  In recent years, techniques for achieving high dispersion by refining graphite particles have been proposed (see, for example, Patent Documents 1 to 3). However, although the graphite particles refined using such a technique are highly dispersible, they may be inferior to the various characteristics inherent to graphite.

  On the other hand, a technique has been proposed in which graphite is refined by a special method to obtain graphite particles that are highly dispersible, excellent in conductivity, and excellent in dispersion stability (for example, Patent Document 4). reference). More specifically, in the method disclosed in Patent Document 4, the fine particles forming a plate shape are obtained by mixing graphite particles, a specific aromatic vinyl copolymer and a hydrogen peroxide and performing a pulverization treatment. This is a method for obtaining a graphite particle-polymer composite in which a specific aromatic vinyl copolymer is adsorbed on the surface of graphite particles (referred to as plate-like graphite particles).

As described above, the graphite particle-polymer composite obtained by this method exhibits superior characteristics as compared with conventional graphite particles. However, in recent years, graphite particles have been used for various applications, and development of graphite particle-polymer composites with further improved performance is desired.
For example, due to the excellent chemical resistance, mechanical strength, lubricity, etc. of graphite particles, it is considered that the graphite particle-polymer composite is also useful as a filler for resin molded products and a conductive additive for electrodes of power storage devices. However, in some cases, the filler, the conductive auxiliary agent, and the like are required to have cushioning properties (that is, cushioning properties), and the graphite particles-polymer composite alone may not satisfy the required cushioning properties.

JP-A-2-204317 JP 2005-53773 A JP 2009-242209 A International Publication No. 2011/155486

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a new technique capable of imparting cushioning properties to a graphite particle-polymer composite.

The method for producing a graphite particle composition of the present invention that solves the above problems is as follows.
Graphite particles, an aromatic vinyl copolymer having a vinyl aromatic monomer unit represented by the following formula (1) and a basic monomer unit represented by the following formula (2), and represented by the following formula (3) And a treatment agent that acts.
^{_{- (CH 2 -CHX 1) -}} ... (1)
^{_{- (CH 2 -CHX 2) -}} ... (2)
L ¹ -RL ² _n (3)
(X ¹ in formula (1) represents a phenyl group, a naphthyl group, an anthracenyl group or a pyrenyl group, and these groups may have a substituent. X ^{2 in} formula (2) is N And / or P represents an organic group, and these groups may have a substituent, R in formula (3) is an alkyl chain having 1 or more carbon atoms, and L ¹ and L ² are each a desorbed group. And is a group, n is 0 or 1, and L ¹ and L ² may be the same or different.)

The graphite particle composition of the present invention that solves the above problems is
Graphite particles,
An aromatic vinyl copolymer adsorbed on the surface of the graphite particles and having a vinyl aromatic monomer unit represented by the following formula (1) and a basic monomer unit represented by the following formula (2): A graphite particle-polymer composite comprising:
An alkyl chain structure derived from the treatment agent represented by the following formula (3) and at least partially interposed between the adjacent graphite particle-polymer composites.
^{_{- (CH 2 -CHX 1) -}} ... (1)
^{_{- (CH 2 -CHX 2) -}} ... (2)
L ¹ -RL ² _n (3)
(X ¹ in formula (1) represents a phenyl group, a naphthyl group, an anthracenyl group or a pyrenyl group, and these groups may have a substituent. X ^{2 in} formula (2) is N And / or P represents an organic group, and these groups may have a substituent, R in formula (3) is an alkyl chain having 1 or more carbon atoms, and L ¹ and L ² are each a desorbed group. And is a group, n is 0 or 1, and L ¹ and L ² may be the same or different.)

Furthermore, the negative electrode of the present invention that solves the above problems is
It includes a mixed powder of at least one active material powder selected from the group consisting of Si, Si compound, Sn and Sn compound and the above-described graphite particle composition of the present invention.

  Furthermore, the power storage device of the present invention that solves the above problems includes the above-described negative electrode of the present invention.

  According to the present invention, it is possible to impart cushioning properties to the graphite particle-polymer composite by treating the graphite particle-polymer composite with a treating agent to obtain a graphite particle composition. Further, it is possible to impart cushioning properties derived from the plate-like particle composition to the negative electrode. Furthermore, it is possible to impart excellent battery characteristics derived from the cushioning property to the power storage device including the negative electrode.

  The graphite particle composition of the present invention is not limited to a negative electrode active material for a storage battery, but can be used for various applications including a conductive additive and a filler for a resin molded product. When the graphite particle composition of the present invention is used as a negative electrode active material for a storage battery or a conductive additive, it is used in combination with a material having a large volume change between charging and discharging (for example, a silicon-based negative electrode active material). By doing so, cushioning can be effectively exhibited. This is presumed to be due to the following reason.

  In the method for producing a graphite particle composition of the present invention, a graphite particle-polymer composite in which an aromatic vinyl copolymer is adsorbed on graphite particles is obtained in the same manner as the technique disclosed in Patent Document 4 described above. Further, the graphite particle-polymer composite (hereinafter referred to as a cationized composite if necessary) treated with a processing agent by applying a treatment agent to the aromatic vinyl copolymer of the graphite particle-polymer composite. The graphite particle composition which is an aggregate of In addition, the graphite particle used by this invention is not limited to the plate-like graphite particle currently disclosed by patent document 4, The thing which is not plate-shaped may be sufficient.

The treating agent has an alkyl chain and a leaving group bonded to the terminal of the alkyl chain. On the other hand, the basic monomer unit of the aromatic vinyl copolymer has N and / or P. The basic monomer units N and / or P act as nucleophiles. That is, N and / or S of the basic monomer unit acts on the carbon to which the leaving group is bonded in the treating agent, removes the leaving group from the treating agent, and loses the leaving group. It binds to the end, ie the end of the alkyl chain, and is cationized. In other words, the surface of the graphite particle-polymer complex treated with the treating agent, that is, the surface of the cationized complex has a positive (+) charge. Therefore, the cationized complexes contained in the graphite particle composition repel each other. This repulsive force is considered to impart cushioning properties to the graphite particle composition. In other words, the graphite particle composition of the present invention is considered to elastically deform reversibly even if it is compressed.
Moreover, it is thought that the alkyl chain of a processing agent exists between cationization composites, This alkyl chain can also become a cushioning material interposed between cationization composites. In other words, it is considered that an alkyl chain of the treatment agent is interposed between adjacent cationized complexes. This alkyl chain is believed to exhibit a spring-like behavior between adjacent cationized complexes. Also by this, the graphite particle composition is considered to exhibit cushioning properties.
And it is thought that cushioning property can be provided to an electrode, a resin molding, etc. by mix | blending such a graphite particle composition of this invention with an electrode, a resin molding, etc. FIG. Hereinafter, the graphite particle composition of the present invention will be described in detail.

<Graphite particle composition>
As described above, the graphite particle composition is an aggregate of a cationized complex including a graphite particle-polymer complex and an alkyl chain structure derived from the treatment agent.

  The graphite particle-polymer composite is obtained by adsorbing an aromatic vinyl copolymer to graphite particles. The graphite particles are not particularly limited, but plate-like graphite particles as disclosed in Patent Document 4 described above, that is, a plate shape having a thickness of 0.3 nm to 100 nm and a length in the major axis direction of 0.1 μm to 500 μm. Fine particles formed are preferable. By using such plate-like graphite particles as the graphite particles, excellent properties derived from the plate-like graphite particles can be imparted to the graphite particle composition of the present invention. The plate-like graphite particles can be obtained, for example, by pulverizing a well-known graphite having a graphite structure, such as artificial graphite, flake graphite, massive graphite, earthy graphite or the like so as not to destroy the graphite structure. Moreover, if a shape is in said range, a commercially available graphene can also be used as plate-like graphite particle.

  The thickness of the plate-like graphite particles is significantly smaller than the scale-like graphite that is natural graphite. The ratio calculated | required by the length / thickness of the long axis direction of plate-like graphite particle | grains is 10-1000, More preferably, it is 50-100. Hereinafter, in the present specification, the “ratio obtained by the length / thickness in the major axis direction of the plate-like graphite particles” may be referred to as an aspect ratio, if necessary.

  The thickness of the plate-like graphite particles is 0.3 nm to 100 nm, and preferably 1 nm to 100 nm. The length of the plate-like graphite particles in the major axis direction is 0.1 μm to 500 μm, and preferably 1 μm to 500 μm. The length in the minor axis direction is preferably 0.3 μm to 100 μm.

  It is preferable that functional groups such as a hydroxyl group, a carboxyl group, and an epoxy group are bonded to the surface of the plate-like graphite particles. When the functional group is bonded to the surface of the plate-like graphite particles, the affinity between the plate-like graphite particles and other organic substances such as a solvent and a polymer is increased. This is particularly useful for increasing the affinity between the plate-like graphite particles and the aromatic vinyl copolymer. That is, the presence of these functional groups increases the amount of adsorption of the aromatic vinyl copolymer onto the plate-like graphite particles.

  Such a functional group is not more than 50 atomic%, more preferably not more than 20 atomic% when the total number of carbon atoms in the vicinity of the surface of the plate-like graphite particles, preferably in the region from the surface to a depth of 10 nm is 100 atomic%. Particularly preferably, it is preferably bonded to 10 atom% or less of carbon atoms. The proportion of carbon atoms to which the functional group is bonded is preferably 0.01 atomic percent or more, assuming that all the carbon atoms in the region from the surface to a depth of 10 nm are 100 atomic percent. When the ratio of the carbon atom to which the functional group is bonded exceeds 50 atomic%, the hydrophilicity of the plate-like graphite particles tends to increase and the affinity with the organic substance tends to decrease. The functional groups near the surface of the plate-like graphite particles can be quantified by X-ray photoelectron spectroscopy (XPS).

The aromatic vinyl copolymer has the following formula (1):
^{_{- (CH 2 -CHX 1) -}} (1)
The vinyl aromatic monomer unit represented by these is contained. The vinyl aromatic monomer unit is considered to be adsorbed to the six-membered ring structure on the surface of the graphite particles by π electron interaction (also referred to as π-π interaction). And the said vinyl aromatic monomer unit adsorb | sucks to a graphite particle, The aromatic vinyl copolymer which has a vinyl aromatic monomer unit adsorb | sucks to a graphite particle. The vinyl aromatic monomer unit is not particularly limited as long as it has a π-electron interaction with the six-membered ring structure on the surface of the graphite particles. For example, in the formula (1), X ¹ represents a phenyl group, a naphthyl group, an anthracenyl group or a pyrenyl group, and these groups may have a substituent.

  An aromatic vinyl copolymer having a higher content of vinyl aromatic monomer units is more easily adsorbed on graphite particles. Therefore, in order to adsorb many aromatic vinyl copolymers to graphite particles, it is preferable that the content of vinyl aromatic monomer units in the aromatic vinyl copolymer is large. On the other hand, the higher the content of the vinyl aromatic monomer unit in the aromatic vinyl copolymer, the lower the content of the basic monomer unit and the third monomer unit described later. Considering these, the content of the vinyl aromatic monomer unit in the aromatic vinyl copolymer is preferably 10% by mass to 98% by mass, and 30% by mass to 98% by mass with respect to the entire aromatic vinyl copolymer. More preferred is 50% by mass to 95% by mass. When the content of the vinyl aromatic monomer unit is lower than 10% by mass, the adsorptive power of the aromatic vinyl copolymer to the graphite particles may be reduced. Moreover, when the content rate of a vinyl aromatic monomer unit becomes higher than 98 mass%, there exists a possibility that the cushioning property fall by lack of a basic monomer unit and the 3rd monomer unit depending on the case may arise.

  The basic monomer unit also has a function of affinity for a solvent, a resin, and the like, like a third monomer unit described later. That is, the basic monomer unit that does not react with the treating agent described later and remains in the cation complex increases the affinity between the solvent or resin and the graphite particle-polymer complex, and thus the solvent or resin and the graphite particle composition. This is useful for increasing the affinity of the graphite particles and highly dispersing the graphite particle composition in the solvent or resin.

  Examples of the substituent of the formula (1) include an alkyl group, an aryl group, an acetyl group, an amino group, a carboxyl group, a carboxylate group, a hydroxyl group, an amide group, an imino group, a glycidyl group, an alkoxy group, a carbonyl group, and an imide. Group and phosphate group. Considering the adsorptivity of the aromatic vinyl copolymer to the graphite particles, the substituent is preferably an alkoxy group, and the alkoxy group is preferably a methoxy group.

  Examples of the vinyl aromatic monomer unit include a styrene monomer unit, a vinyl naphthalene monomer unit, a vinyl anthracene monomer unit, a vinyl pyrene monomer unit, a vinyl anisole monomer unit, a vinyl benzoate monomer unit, and an acetyl styrene monomer unit. Considering the adsorptivity of the aromatic vinyl copolymer to the graphite particles, the vinyl aromatic monomer unit is preferably a styrene monomer unit, a vinyl naphthalene monomer unit, or a vinyl anisole monomer unit. As the vinyl aromatic monomer unit, only one of these may be selected, or a plurality of these may be used in combination.

  The aromatic vinyl copolymer has a basic monomer unit in addition to the vinyl aromatic monomer unit described above. The aromatic vinyl copolymer may consist of only a vinyl aromatic monomer unit and a basic monomer unit, or may contain other monomer units.

The basic monomer unit is represented by the following formula (2).
^{_{- (CH 2 -CHX 2) -}} ... (2)
In the formula (2), X ² represents an organic group containing N and / or P, and these groups may have a substituent.

In the basic monomer unit represented by the above formula (2), N or P in X ² reacts with carbon bonded to the leaving group of the treating agent to form a quaternary salt, that is, cationize. . In other words, it can be said that N or P in the organic group of the basic monomer unit functions as a nucleophile that reacts with the treating agent. Hereinafter, N and / or P in the organic group of the basic monomer unit is referred to as a nucleophile element as necessary.
Organic groups of basic monomer units include aziridine, azirine, azetidine, azeto, pyrrolidine, pyrrole, piperidine, pyridine, azepan, azepine, imidazoles, pyrazole, oxazole, thiazole, imidazoline, imidazolidinone, pyrazine, morpholine, thiazine , Pyrazoline, pyrazolone, pyrazolidine, pyrazolate, pyrimidine, quinoline, isoquinoline, quinoxaline, amine phosphole and the like, but not limited thereto.
The basic monomer unit consists of vinyl imidazoles, vinyl azoles, vinyl pyridines, vinyl amines, vinyl aziridine, vinyl phosphor, vinyl thiazole, vinyl pyrazine, vinyl pyrazoline, vinyl pyrimidine, vinyl quinoline, vinyl isoquinoline, vinyl quinoxaline. It is preferably derived from at least one monomer selected from the group. The basic monomer unit may contain only one kind of the above-described nucleophile element or may contain various kinds. Moreover, 1 mol may be sufficient as the nucleophile element contained in 1 mol of basic monomer units, and 2 mol or more may be sufficient as it.

Examples of vinyl imidazoles include 1-vinyl imidazole.
Examples of vinyl azoles include 1-vinyl-1H-pyrrole, 2-vinyl-1H-pyrrole, 1-vinylimidazole, 2-vinylimidazole and the like.
Examples of vinyl pyridines include 2-vinyl pyridine and 4-vinyl pyridine.
Examples of vinylamines include methyl vinylamine.
Examples of vinylaziridine include 1-vinylaziridine.
As vinylphosphol, 2- (allyloxy) -3-vinyl-2,5-dihydro-1,2-oxaphosphole, 2-vinyl-1,3,2-benzodioxaphosphole, 2-vinyl- 2H-phosphole.
Examples of vinyl thiazole include 2-vinyl thiazole.
Examples of vinylpyrazine include 2-vinylpyrazine.
Examples of vinylpyrazoline include 5-vinylpyrazoline, 3-vinyl-1-pyrazoline and the like.
Examples of vinylpyrimidine include 5-vinylpyrimidine.
Examples of vinyl quinoline include 2-vinyl quinoline and 4-vinyl quinoline. Examples of vinylamine include methyl vinylamine. Examples of vinyl amide include N-vinyl amide.
Examples of vinylisoquinoline include 4-vinylisoquinoline.
Examples of vinyl quinoxaline include 2-vinyl quinoxaline.

The basic monomer unit reacts with the treating agent to form a quaternary salt, that is, cationizes. For this reason, it is preferable to select a basic monomer unit that is easily cationized. X ^{2 of the} basic monomer unit, that is, the organic group may be linear or cyclic, but in view of cationization, it is preferably a heterocyclic structure. In addition, as a basic monomer unit, 1 type of various basic monomer units mentioned above may be selected, and two or more may be used together.

  The content of the basic monomer unit relative to the vinyl aromatic monomer unit is preferably 0.1 to 10 mol, more preferably 0.3 to 3 mol, per 1 mol of the vinyl aromatic monomer unit. 0.5 to 2 mol is more preferable.

  The vinyl aromatic monomer unit and the basic monomer unit are particularly preferably present in a molar ratio of 1: 1. If the content ratio of the basic monomer unit is too small, it becomes difficult to frequently cationize the surface of the cationized complex including the graphite particle-polymer complex and the alkyl chain structure. As a result, the electrostatic repulsion force between adjacent cationized composites also becomes small, and it may be difficult to give a large cushioning property to the graphite particle composition. Further, if the content ratio of the basic monomer unit is excessive, the content ratio of the vinyl aromatic monomer unit becomes relatively small, and it may be difficult to increase the adsorptivity of the aromatic vinyl copolymer to the graphite particles.

The treating agent is represented by the following formula (3):
L ¹ -RL ² _n (3)
(In formula (3), R is an alkyl chain having 2 or more carbon atoms, L ¹ and L ² are each a leaving group, n is 0 or 1, and L ¹ and L ² are the same, Can be good or different.)
It is represented by

Examples of the leaving group include halogen mesylate such as chlorine, bromine and iodine, and triflate. When the treating agent has two leaving groups, one leaving group L ¹ and the other leaving group L ² may be different from each other. Further, as the treating agent, two or more kinds having different leaving groups (or combinations of leaving groups) may be used in combination. In the present invention, it is basically assumed that one nucleophile element of the basic monomer unit reacts with the treating agent to remove one leaving group. The leaving group is preferably iodine or bromine. In other words, L ¹ and L ² in the above formula (3) are preferably each independently iodine or bromine.
The larger the electrostatic repulsion force, the harder the adjacent cationized complex is fixed. For this reason, it is preferable that most of the basic monomer units react with the treating agent in consideration of cushioning properties. Therefore, it is considered that the amount of the treating agent with respect to the basic monomer unit is preferably a predetermined value or more. In addition, when the treating agent has only one leaving group, that is, when n = 0 without L ^{2 in the} above formula (3), 1 mole of the treating agent and 1 mole of the basic monomer unit react. On the other hand, when the treating agent has two leaving groups, that is, when n = 1 with L ^{2 in the} above formula (3), 1 mol of the treating agent reacts with 2 mol of the basic monomer unit. . Accordingly, it is considered that a preferable ratio of the amount of the processing agent to the basic monomer unit, more specifically, a lower limit value of the ratio varies depending on the number of leaving groups of the processing agent.

  Specifically, the basic monomer unit and the treating agent are preferably blended so that the number of leaving groups for one atom of the nucleophile element is a predetermined number or more. The number of leaving groups for one atom of the nucleophile element is preferably 0.05 or more, more preferably 0.06 or more, and even more preferably 0.08 or more.

  By the way, when the amount of the basic monomer unit reacted with the treating agent is excessive, and the amount of the treating agent remaining in the graphite particle composition and the unreacted basic monomer unit is too small, the graphite particle composition with respect to the solvent or the resin. It may be difficult to ensure the affinity of the basic monomer unit. In this case, it may be difficult to increase the dispersibility of the graphite particle composition with respect to the resin or the like. Accordingly, it is considered that there is a preferable ratio of the treating agent to the basic monomer unit, more specifically, an upper limit value of the ratio in the absence of at least a third monomer unit described later.

  Specifically, the number of leaving groups for one atom of the nucleophile element is preferably less than 1.2, more preferably 1.0 or less, and even more preferably 0.8 or less.

  And when there is no 3rd monomer unit, the following numerical ranges can be made in consideration of the above-mentioned preferable upper limit and preferable lower limit. That is, the number of leaving groups per atom of the nucleophile element is preferably 0.05 or more and less than 1.2, more preferably 0.06 or more and 1.0 or less, and 0.08 or more and 0.0. It is particularly preferred that it is 8 or less. It is still more preferably 0.1 or more and 0.8 or less, and further preferably 0.2 or more and 0.7 or less.

  In the graphite particle composition of the present invention, the cushioning property of the graphite particle composition is considered to be exhibited by electrostatic repulsion. Therefore, it is considered that the cushioning properties of the graphite particle composition are not lost only once, but are repeatedly exhibited multiple times. For this reason, the graphite particle composition of the present invention is preferably used as a conductive auxiliary agent or a second negative electrode active material added to a negative electrode for a secondary battery, for example, in applications where cushioning properties are required repeatedly.

When the graphite particle composition of the present invention is used for a negative electrode for a power storage device such as a negative electrode for a secondary battery, it is considered that the capacity reduction of the power storage device can be suppressed. For example, silicon-based negative electrode active materials represented by SiO and SiO _x are known as negative electrode active materials for secondary batteries. These silicon-based negative electrode active materials are negative electrode active materials having a large volume change accompanying charge / discharge. Therefore, when a silicon-based negative electrode active material is used, cracks may occur in the negative electrode active material layer due to a volume change of the negative electrode active material, or a part of the negative electrode active material layer may fall off from the negative electrode. In such a case, the capacity of the secondary battery is reduced. Similarly, during the first charge / discharge, the capacity of the secondary battery may be reduced due to the detachment of the negative electrode active material layer or the like. When the graphite particle composition of the present invention is used for a negative electrode for a power storage device, the volume change of the negative electrode active material can be buffered by the cushion function of the graphite particle composition itself, and the negative electrode active material layer can be cracked or detached. Can be suppressed, and as a result, the capacity of the power storage device including the initial capacity can be improved.

  In order to efficiently exhibit the cushion function of the graphite particle composition, it is preferable that an alkyl chain of the treatment agent is bridged between adjacent cationized complexes. For this purpose, the treating agent preferably has two leaving groups.

  What is necessary is just to set the length of the alkyl chain in a processing agent suitably according to the use of a graphite particle composition. For example, when a graphite particle composition is used for a negative electrode for a power storage device, adjacent cationized complexes are preferably separated from each other in order to increase the cushioning properties of the graphite particle composition. A longer alkyl chain is preferred. On the other hand, if the length of the alkyl chain is excessive, the graphite particle composition becomes bulky, and it may be difficult to mix a sufficient amount of an active material such as a negative electrode active material or a positive electrode active material. As a result, it may be difficult to improve the battery capacity of the power storage device.

  Therefore, when the graphite particle composition of the present invention is used in combination with a silicon-based negative electrode active material having a large volume change for a negative electrode for a power storage device, the alkyl chain in the treatment agent has a linear structure having 4 to 6 carbon atoms, That is, it preferably has a straight chain structure with a chain length of 4-6. A branched chain may further extend from the linear structure. The number of branched chains is not limited to one and may be plural. Further, the length of the branched chain is not particularly limited. That is, if one end of the alkyl chain is bonded to one of the two adjacent cationized complexes and the other end of the alkyl chain is bonded to the other of the two adjacent cationized complexes, The distance is determined by the chain length of the linear structure of the alkyl chain in the treating agent. For this reason, it is presumed that the number and length of the branched chains do not greatly affect the bulkiness of the graphite particle composition.

  Note that the plate-like graphite particles, that is, the plate-like graphite particles described above, are easily oriented in a certain direction in the fluid. Therefore, when plate-like graphite particles are used as the graphite particles, when the graphite particle composition of the present invention is used as a negative electrode active material or a conductive additive, the plate surface of the plate-like graphite particles is substantially on the surface of the current collector. It is easy to orient the plate-like graphite particles so as to be parallel. In this case, since alkyl chains are bridged between regularly oriented plate-like graphite particles, the graphite particle composition can be made into a regular structure, and a graphite particle composition that can exhibit cushioning properties more effectively is obtained. It is possible. In this case, the bulk density of the negative electrode active material layer in the negative electrode or the positive electrode active material layer in the positive electrode can be increased, and there is an advantage that the battery capacity can be increased.

  When the aromatic vinyl copolymer includes a monomer unit other than a vinyl aromatic monomer unit and a basic monomer unit (that is, a third monomer unit), the third monomer unit has excellent affinity for a solvent or a resin. It is preferable. Since the aromatic vinyl copolymer containing such a third monomer unit is adsorbed on the surface of the graphite particles, the affinity between the graphite particles and the solvent or resin is improved, and the graphite in the solvent or resin is improved. The dispersibility of the particles can be increased. That is, in this case, even if many of the basic monomer units react with the treatment agent, the graphite particle composition can be highly dispersed in the solvent or resin.

  That is, the vinyl aromatic monomer unit in the aromatic vinyl copolymer has a function of adsorbing the aromatic vinyl copolymer to the graphite particles. Moreover, a basic monomer unit bears the function which reacts with a processing agent and improves the cushioning property of a graphite particle composition. Furthermore, the third monomer unit mainly has a function of improving the affinity between the graphite particle composition and a resin such as a solvent or a binder.

The third monomer unit is (meth) acrylic acid, (meth) acrylates, (meth) acrylamides, vinyl imidazoles, vinyl pyridines, maleic anhydride and maleimides in consideration of the affinity with the solvent and the resin. Preferably, it is derived from at least one monomer selected from the group consisting of: The third monomer unit does not need to react with the treating agent, but may be the same as or different from the basic monomer unit described above.
In this specification, for example, “(meth) acrylic acid” means both “acrylic acid” and “methacrylic acid”.

  From the viewpoint of improving the dispersibility of the graphite particles, the third monomer unit is alkyl (meth) acrylate, hydroxyalkyl (meth) acrylate, aminoalkyl (meth) acrylate, N, N-dialkyl (meth) acrylamide, 2 -Vinyl pyridine, 4-vinyl pyridine and arylmaleimide are preferable, and hydroxyalkyl (meth) acrylate, N, N-dialkyl (meth) acrylamide, 2-vinylpyridine and arylmaleimide are more preferable, and phenylmaleimide. It is particularly preferred that In addition, as a 3rd monomer unit, these may be used independently and these multiple may be used together. The amount of the third monomer unit may be appropriately set in consideration of the amount of the basic monomer unit assumed not to react with the treating agent.

  Examples of the aromatic vinyl copolymer include, for example, a random copolymer of styrene (ST) and 1-vinylimidazole (VI), a random copolymer of ST and 4-vinylpyridine (4VP), ST And a random copolymer of N, N-dimethylaminoethyl methacrylate (DMAEMA), a random copolymer of ST and 2-vinylpyridine (2VP), and a block copolymer of ST and 2VP.

  The number average molecular weight of the aromatic vinyl copolymer is preferably 1,000 to 1,000,000, and more preferably 5,000 to 100,000. If the number average molecular weight of the aromatic vinyl copolymer is less than 1,000, the adsorptive capacity to the graphite particles tends to be reduced. On the other hand, if the number average molecular weight is larger than 1,000,000, the graphite particle composition It tends to be difficult to handle due to a decrease in dispersibility in a solvent or resin, or a marked increase in viscosity. The number average molecular weight of the aromatic vinyl copolymer was measured by gel permeation chromatography (column: Shodex GPC K-805L and Shodex GPC K-800RL (both manufactured by Showa Denko KK), eluent: chloroform). The value converted with standard polystyrene is used.

  As described above, a random copolymer or a block copolymer may be used as the aromatic vinyl copolymer, but the dispersibility of the graphite particle composition in a solvent or resin is improved. From the viewpoint, it is preferable to use a block copolymer.

  Graphite particles having the aromatic vinyl copolymer adsorbed on the surface thereof, that is, the content of the aromatic vinyl copolymer in the graphite particle-polymer composite is 0.01 to 10 parts by mass with respect to 100 parts by mass of the graphite particles. It is preferable that it is 0.1 to 5 parts by mass. If the content of the aromatic vinyl copolymer with respect to 100 parts by mass of the graphite particles is less than 0.01 parts by mass, the amount of the basic monomer units with respect to the graphite particles is relatively small, and the reaction between the basic monomer units and the treatment agent The amount of cations generated in is also relatively small, and thus the electrostatic repulsive force derived from the cations may be relatively small. Also, the alkyl chain produced by the reaction between the basic monomer unit and the treating agent may not be sufficient. That is, in this case, there is a possibility that the cushioning property of the graphite particle composition cannot be greatly improved. On the other hand, when the amount of the aromatic vinyl copolymer with respect to 100 parts by mass of the graphite particles exceeds 10 parts by mass, the ratio of the graphite particles in the graphite particle composition is relatively reduced.

The graphite particle composition is manufactured through an action process. In the action step, graphite particles, an aromatic vinyl copolymer, and a treating agent may be allowed to act, and these may be caused to act in any order.
For example, first, a step of obtaining a graphite particle-polymer composite by allowing graphite particles and an aromatic vinyl copolymer to act, that is, a graphite particle-polymer composite forming step is performed, and then the graphite particle-polymer composite is performed. You may perform the process which makes a processing agent act on, ie, a processing agent action | operation process. Or you may make a graphite particle, an aromatic vinyl copolymer, and a processing agent act simultaneously.

When the graphite particles are plate-like graphite particles, a crushing step of crushing the graphite particles to obtain plate-like graphite particles is performed. In the crushing step, for example, the graphite particles may be crushed so as to be plate-like graphite particles having a thickness of 0.3 nm to 100 nm and a length in the major axis direction of 0.1 μm to 500 μm in the presence of hydrogen peroxide.
The crushing process may be performed before the action process, may be performed simultaneously with the action process, or may be performed after the action process. That is, the aromatic vinyl copolymer may be bonded to the plate-like graphite particles prepared in advance and the aromatic vinyl copolymer and the treatment agent may be allowed to act. Alternatively, an aromatic vinyl copolymer may be bonded to the obtained plate-like graphite particles at the same time when the graphite particles are crushed to form plate-like graphite particles. Alternatively, the aromatic vinyl copolymer bonded to the plate-like graphite particles and the treatment agent may be allowed to act at the same time. In the crushing step, at least graphite particles may be crushed so as to be within the range of the dimensions.

  Examples of the graphite particles that serve as the raw material of the plate-like graphite particles, that is, the raw material graphite particles include known graphite having a graphite structure, such as artificial graphite, flake graphite, massive graphite, and earth graphite. The particle diameter of the raw material graphite particles is preferably 0.01 mm to 5 mm, more preferably 0.1 mm to 1 mm.

  Examples of the hydrogen peroxide include a complex of a compound having a carbonyl group and hydrogen peroxide, or a compound in which hydrogen peroxide is coordinated to a compound such as a quaternary ammonium salt, potassium fluoride, rubidium carbonate, phosphoric acid, or uric acid. Can be mentioned. Examples of the compound having a carbonyl group include urea, carboxylic acid (benzoic acid, salicylic acid, etc.), ketone (acetone, methyl ethyl ketone, etc.), and carboxylic acid ester (methyl benzoate, ethyl salicylate, etc.). As the hydrogen peroxide, a complex of a compound having a carbonyl group and hydrogen peroxide is preferable.

  Such a hydrogen peroxide acts as an oxidizing agent and facilitates peeling between carbon layers without destroying the graphite structure of the raw graphite particles. For example, the mechanism when an aromatic vinyl copolymer is present in the crushing process is described. Hydrogen peroxide enters between the carbon layers to promote cleavage while oxidizing the layer surface, and at the same time aromatic vinyl copolymer The coalescence penetrates into the cleaved carbon layer to stabilize the cleaved surface and promote delamination. As a result, the aromatic vinyl copolymer is adsorbed on the surface of the graphite particles.

  In the crushing step, the graphite particles as a raw material are crushed in the presence of hydrogen peroxide. The crushing step is preferably performed in a solvent, and more preferably, the components are mixed in the solvent and then crushed. As described above, in some cases, in addition to the raw graphite particles and the hydrogen peroxide compound, the aromatic vinyl copolymer and / or the treatment agent may be subjected to a crushing step.

  Solvents are dimethylformamide (DMF), chloroform, dichloromethane, chlorobenzene, dichlorobenzene, N-methylpyrrolidone (NMP), hexane, toluene, dioxane, propanol, γ-picoline, acetonitrile, dimethyl sulfoxide (DMSO), dimethylacetamide (DMA). ), And dimethylformamide (DMF), chloroform, dichloromethane, chlorobenzene, dichlorobenzene, N-methylpyrrolidone (NMP), hexane, and toluene are more preferable.

  The mixing amount of the graphite particles in the crushing step is preferably 0.1 g / L to 500 g / L per liter of solvent, and more preferably 10 g / L to 200 g / L. If the amount of graphite particles used as a raw material is less than 0.1 g / L per liter of solvent, the consumption of the solvent increases, which is economically disadvantageous. On the other hand, if it exceeds 500 g / L per solvent, the viscosity of the liquid Rises and handling becomes difficult.

  The mixing amount of the aromatic vinyl copolymer is preferably 0.1 part by mass to 1000 parts by mass, and more preferably 0.1 part by mass to 200 parts by mass with respect to 100 parts by mass of the raw graphite particles. When the mixing amount of the aromatic vinyl copolymer is less than 0.1 parts by mass with respect to 100 parts by mass of the raw material graphite particles, the dispersibility of the obtained plate-like graphite particles tends to be lowered. When the mixing amount of the copolymer exceeds 1000 parts by mass with respect to 100 parts by mass of the raw graphite particles, the aromatic vinyl copolymer does not dissolve in the solvent, and the viscosity of the liquid rises and handling becomes difficult. .

  The mixing amount of the hydrogen peroxide is preferably 0.1 to 500 parts by mass, more preferably 1 to 100 parts by mass with respect to 100 parts by mass of the raw graphite particles. When the mixing amount of the hydrogen peroxide is less than 0.1 parts by mass with respect to 100 parts by mass of the raw graphite particles, the dispersibility of the obtained plate-like graphite particles tends to be lowered. On the other hand, 100 parts by mass of the raw graphite particles When the amount exceeds 500 parts by mass, the raw graphite particles are excessively oxidized, and the conductivity of the obtained plate-like graphite particles tends to be lowered.

  In the crushing step, the graphite particles are crushed in the presence of hydrogen peroxide. For example, the mixture containing the solvent, graphite particles and hydrogen peroxide is subjected to crushing treatment. Through the crushing process, the graphite particles as the raw material are miniaturized to obtain plate-like graphite particles. Examples of the crushing treatment include ultrasonic treatment, ball mill treatment, wet crushing, and mechanical crushing. In the ultrasonic treatment, the oscillation frequency is preferably 15 to 400 kHz, and the output is preferably 500 W or less. As the crushing treatment, ultrasonic treatment or wet crushing treatment is preferable. In the crushing step, plate-like graphite particles can be obtained by crushing so as not to destroy the graphite structure of the graphite particles as the raw material. Moreover, as temperature at the time of a crushing process, it can be set as -20 degreeC-100 degreeC, for example. Moreover, as crushing processing time, it can be set as 0.01 hour-50 hours, for example.

  As described above, the graphite particle composition of the present invention can be used for an electrode for a power storage device. Specifically, the graphite particle composition of the present invention can be used as a conductive aid for electrodes and / or a negative electrode active material. Particularly preferably, a graphite particle composition is used as a part of the negative electrode active material for a power storage device. The power storage device is a concept including a lithium ion secondary battery, an electric double layer capacitor, a lithium ion capacitor, and the like.

  Negative electrode active materials that are inferior in conductivity but large in capacity, such as silicon compounds and tin compounds, are known. Specifically, this corresponds to at least one negative electrode active material selected from the group consisting of Si, Si compounds, Sn, and Sn compounds. When such a negative electrode active material is used, a binder having high ionic conductivity such as polyacrylic acid is used. However, since polyacrylic acid has a lower binding force than other binders such as polyamideimide, when this type of binder is used, the negative electrode active material and the binder peel off during use, resulting in charge / discharge cycles. In some cases, the capacity retention rate after repetition was relatively low.

The graphite particle composition of the present invention is derived from graphite particles, can adsorb and release charge carriers, and is excellent in conductivity. That is, the graphite particle composition of the present invention can be preferably used as a negative electrode active material for a power storage device.
Moreover, the graphite particle composition of the present invention is derived from a cationized composite and has excellent cushioning properties. Therefore, when the graphite particle composition of the present invention is used in combination with the above-described negative electrode active material having a large volume change, stress acting on the negative electrode active material layer during charge / discharge is relieved, and the cycle characteristics of the power storage device are improved. In this case, since it is possible to impart excellent conductivity derived from the conductivity of the graphite particles to the negative electrode, a binder that does not contribute to improvement in conductivity can be used.
Furthermore, the plate-like graphite particles have a layer structure in which a plurality of graphene single layers are laminated, and are excellent in strength. Therefore, when plate-like graphite particles are employed as the graphite particles in the graphite particle composition of the present invention, the mechanical strength of the negative electrode active material layer can be increased. The cycle characteristics of the power storage device can be further improved by the cooperation of the excellent mechanical strength and the excellent cushioning property derived from the cationized composite.

  Hereinafter, “a negative electrode active material that is inferior in conductivity but large in capacity, such as a silicon-based compound and a tin-based compound” that can be used in combination with the plate-like graphite particle composition of the present invention will be described. Hereinafter, this type of negative electrode active material is referred to as a first active material as necessary. The first active material powder is referred to as a first active material powder.

<First active material powder>
The first active material powder Si, Si compounds, those selected from the group consisting of Sn and Sn compounds, the average particle size _{D 50} is preferably at 300nm than 20μm or less. The average particle diameter D ₅₀ of the first active material powder is 300nm smaller, the specific surface area of the first active material powder is increased, the contact area between the first active material powder and the electrolyte is increased, the decomposition of the electrolyte solution Advances and the cycle characteristics deteriorate. Also not preferred because the average particle diameter D ₅₀ is larger secondary particle diameter due to aggregation and 300nm smaller. Si, because Si compound is less conductive one, the average particle diameter D ₅₀ of greater than 20 [mu] m, the conductivity of the whole electrode becomes uneven, charging and discharging characteristics are degraded.

  In addition, since Si, Si compound, Sn, and Sn compound expand and contract during charging and discharging, the crystallite size of Si, Si compound, Sn, and Sn compound is more preferably 1 nm to 300 nm in order to reduce the expansion and contraction. preferable.

The average particle diameter D ₅₀ can be measured by particle size distribution measurement method. The average particle diameter D ₅₀ refers to the particle size cumulative value of the volume distribution in the particle size distribution measurement by laser diffraction method is equivalent to 50%. That is, the average particle diameter D ₅₀ refers to the median diameter measured by volume. The crystallite size is calculated by the Scherrer equation from the half width of the diffraction peak obtained by X-ray diffraction (XRD) measurement.

As the Si compound, for example, a silicon oxide represented by SiO _x (0.3 ≦ x ≦ 1.6) is preferable. Each particle of the silicon oxide powder is composed of SiO _x decomposed into fine Si and SiO ₂ covering Si by a disproportionation reaction. If x is less than the lower limit, the Si ratio increases, so that the volume change during charging and discharging becomes too large, and the cycle characteristics of the power storage device deteriorate. When x exceeds the upper limit value, the Si ratio decreases and the energy density of the negative electrode decreases. A range of 0.5 ≦ x ≦ 1.5 is preferable, and a range of 0.7 ≦ x ≦ 1.2 is more desirable.

In general, it is said that almost all SiO is disproportionated and separated into two phases at 1000 ° C. or higher when oxygen is turned off. Specifically, the raw material silicon oxide powder containing amorphous SiO powder is subjected to heat treatment at 1000 to 1200 ° C. for 1 to 5 hours in an inert atmosphere such as in a vacuum or an inert gas. A silicon oxide powder containing two phases of an amorphous SiO ₂ phase and a crystalline Si phase is obtained.

Moreover, what compounded the carbon material with 1-50 mass% with respect to the silicon oxide can also be used. By combining a carbon material with silicon oxide, the conductivity of the negative electrode active material is improved, and the capacity of the power storage device is also improved. In addition, by combining a carbon material with silicon oxide, the strength of the negative electrode active material is improved, and thus the cycle characteristics of the power storage device are improved. If the composite amount of the carbon material is less than 1% by mass, the effect of improving the electrical conductivity cannot be obtained, and if it exceeds 50% by mass, the proportion of SiO _x is relatively decreased and the negative electrode capacity is decreased. The composite amount of the carbon material is preferably in the range of 5 to 30% by mass, more preferably in the range of 5 to 20% by mass with respect to SiO _x . In order to combine a carbon material with SiO _x , a CVD method or the like can be used.

  The silicon oxide powder desirably has an average particle size in the range of 1 μm to 10 μm. If the average particle size is larger than 10 μm, the charge / discharge characteristics of the non-aqueous secondary battery may be deteriorated. If the average particle size is smaller than 1 μm, the particles aggregate and become coarse particles. Discharge characteristics may deteriorate.

  As the Si becomes finer, the cycle characteristics of the power storage device using it as a negative electrode active material improve. Therefore, it is also preferable to use nano-silicon powder having a nano-size particle size or crystallite size as the first active material powder. The nano size means that the average particle size or crystallite size is 1 μm or less. Hereinafter, the nanosilicon powder will be described.

The inventors of the present application relate to a layered polysilane described in Physical Review B (1993), vol 148, 8172-8189 (hereinafter referred to as Non-Patent Document 1) and Japanese Patent Application Laid-Open No. 2011-090806 (hereinafter referred to as Patent Document 5). We conducted intensive research and focused on the Raman spectrum. In general, it is estimated that the coupling becomes stronger when the Raman shift is shifted to the high frequency side, and the coupling is easily broken when the Raman shift is shifted to the low frequency side. When the Raman spectrum of this layered polysilane was compared with the Raman spectrum of single crystal silicon, the Si—Si bond observed at 520 cm ⁻¹ in single crystal silicon was found to be 320 cm on the lower frequency side in layered polysilane compared to single crystal silicon. It turned out that it shifted to ^-1 .

That is, by using a layered polysilane structure, it was predicted that Si—Si bonds would be weakened and nanosiliconization would be possible under mild conditions. And it discovered that an above-mentioned nano silicon powder was obtained by heat-processing layered polysilane at the temperature exceeding 100 degreeC in non-oxidizing atmosphere. The layered polysilanes described in Non-Patent Document 1 and Patent Document 5 have a structure in which a plurality of six-membered rings composed of silicon atoms are connected, and have a layered polysilane represented by a composition formula (SiH) _n as a basic skeleton. By subjecting this layered polysilane to the heat treatment described above, nanosilicon powder having a crystallite size of about 5 nm was obtained. In the heat treatment at less than 100 ° C., the structure of the layered polysilane is maintained as it is, and nanosilicon powder cannot be obtained. The heat treatment time varies depending on the heat treatment temperature, but one hour is sufficient for heat treatment at 500 ° C. or higher.

Further, it is known that when the SiO ₂ component is contained in the negative electrode active material, the initial characteristics are deteriorated. Since the amount of oxygen contained in the layered polysilane described in Non-Patent Document 1 and Patent Document 5 is large and the layered polysilane is considered to contain a large amount of SiO ₂ component, it is not suitable as a negative electrode active material as described above.

As a result of intensive research, the inventors of the present invention have found that the amount of oxygen in the obtained layered polysilane changes depending on the production conditions of the layered polysilane, and the amount of oxygen in the nanosilicon powder obtained by heat-treating it also changes. Revealed. In Non-Patent Document 1 and Patent Document 5, HCl and CaSi ₂ are reacted to obtain a layered polysilane. CaSi ₂ forms a layered crystal in which a Ca atomic layer is inserted between (111) faces of diamond-type Si, and a layered polysilane is obtained by extracting Ca from the CaSi ₂ by reaction with an acid.

In the Raman spectrum of this layered polysilane, there are peaks at Raman shifts of 341 ± 10 cm ⁻¹ , 360 ± 10 cm ⁻¹ , 498 ± 10 cm ⁻¹ , 638 ± 10 cm ⁻¹ , and 734 ± 10 cm ⁻¹ .

It was revealed that the amount of oxygen in the layered polysilane and nanosilicon material obtained was reduced by using a mixture of HF and HCl as the acid for extracting Ca from CaSi ₂ .

In this production method, a mixture of HF and HCl is used as the acid. By using HF, the SiO ₂ component generated during synthesis or purification is etched, thereby reducing the amount of oxygen. Even when only HF is used, a layered polysilane can be obtained. However, the layered polysilane thus obtained is not preferable because it is easily oxidized by a small amount of air and the amount of oxygen increases. When only HCl is used, it is the same as in Non-Patent Document 1, and only a layered polysilane having a large amount of oxygen can be obtained.

The composition ratio of HF and HCl is desirably in the range of HF / HCl = 1/1 to 1/100 in terms of molar ratio. If the amount of HF exceeds this range, impurities such as CaF ₂ and CaSiO-based compounds are generated, and it is difficult to separate the impurities from the layered polysilane, which is not preferable. If the amount of HF is less than this range, the etching action by HF is weak and oxygen may remain in the layered polysilane.

As for the compounding ratio of the mixture of HF and HCl and CaSi ₂ , it is desirable to make the acid excess from the equivalent. The reaction atmosphere is preferably a vacuum or an inert gas atmosphere. In addition, according to this manufacturing method, it became clear that reaction time became short compared with the manufacturing method of a nonpatent literature 1. If the reaction time is too long, Si and HF further react to produce SiF ₄ , and therefore a reaction time of about 0.25 to 24 hours is sufficient. For reference, the reaction proceeds easily even at room temperature.

CaCl _{2 and the} like are also produced by the above reaction, but can be easily removed by washing with water. Therefore, purification of the layered polysilane is easy.

  The layered polysilane produced as described above is heat-treated at a temperature of 100 ° C. or higher in a non-oxidizing atmosphere, whereby an agglomerated particulate nanosilicon powder with a small amount of oxygen can be obtained. Examples of the non-oxidizing atmosphere include an inert gas atmosphere and a vacuum atmosphere. The inert gas is not particularly defined unless it contains oxygen such as nitrogen, argon or helium.

  The heat treatment temperature is preferably in the range of 100 ° C to 1000 ° C, particularly preferably in the range of 400 ° C to 600 ° C. Below 100 ° C., no nanosilicon powder is produced. In particular, the nanoparticle powder in the form of aggregated particles formed by heat treatment at 400 ° C. or higher is preferably used as the negative electrode active material, and can improve the initial efficiency of the lithium ion secondary battery. That is, this type of nanosilicon powder is preferably used in the power storage device of the present invention as the first active material.

  The Si crystallite size of the nanosilicon powder is preferably from 0.5 nm to 300 nm, particularly preferably from 1 nm to 100 nm, from 1 nm to 50 nm, and more preferably from 1 nm to 10 nm, for use as an electrode active material for a power storage device. This crystallite size can be calculated by the Scherrer equation from the half width of the diffraction peak on the (111) plane obtained by X-ray diffraction.

  Although the amount of oxygen of the nanosilicon powder obtained by heat-treating the layered polysilane produced by the production method described in Non-Patent Document 1 is as large as about 33%, the layered polysilane produced by the above production method is heat-treated. The amount of oxygen in the nanosilicon powder thus obtained is as small as 30% or less.

Nano silicon powder is not restricted to what was obtained by the above-mentioned method. Further, for example, the nanosilicon powder is not limited to a crystal but may be amorphous. Of course, Si compounds other than the above-mentioned nano silicon powder can also be used as the first active material powder. Examples of Si compounds other than nano silicon powder include SiB ₄ , SiB ₆ , Mg ₂ Si, Mg ₂ Si, Ni ₂ Si, TiSi ₂ , MoSi ₂ , CoSi ₂ , NiSi ₂ , CaSi ₂ , CrSi ₂ , Cu _{5. Si, FeSi 2, MnSi 2,} NbSi 2, TaSi 2, VSi 2, WSi 2, ZnSi 2, SiC, Si 3 N 4, Si 2 N 2 O, and the like can be exemplified SnSiO 3, LiSiO.

As Sn, commercially available Sn powder can be used. As the Sn compound, for example, SnO _w (0 <w ≦ 2), SnSiO ₃ , LiSnO, tin alloy (Cu—Sn alloy, Co—Sn alloy, etc.) can be used.

  In addition to the above-mentioned first active material powder and the graphite particle composition of the present invention, graphite can also be added to the negative electrode active material. Examples of graphite include natural graphite, granulated graphite, hard carbon, and soft carbon. The amount of graphite added is preferably in the range of 90% by mass or less when the total amount of the first active material powder, the graphite particle composition and the graphite is 100% by mass. When the graphite content is more than 90% by mass, the capacity may decrease or the cushion function derived from the graphite particle composition may decrease.

  When the total of the first active material powder and the graphite particle composition is 100% by mass, the graphite particle composition is preferably blended in an amount of 5 to 30% by mass, and is blended in an amount of 10 to 20% by mass. Is more preferable. When the blending amount of the graphite particle composition is less than 5% by mass, the cushion function by the graphite particle composition is small. Moreover, since the theoretical capacity | capacitance of a graphite particle composition is small compared with a 1st active material powder, when the compounding quantity of a graphite particle composition exceeds 30 mass%, the charging / discharging capacity | capacitance of an electrical storage apparatus will fall.

<Negative electrode>
The graphite particle composition of the present invention is used for a negative electrode of a power storage device. The negative electrode includes a current collector and a negative electrode active material layer disposed on the current collector surface. The current collector refers to a chemically inert electronic high conductor that keeps a current flowing through an electrode during discharging or charging of a power storage device. As a material that can be used for the current collector, for example, at least one selected from silver, copper, gold, aluminum, tungsten, cobalt, zinc, nickel, iron, platinum, tin, indium, titanium, ruthenium, tantalum, chromium, and molybdenum In addition, a metal material such as stainless steel, and further a conductive resin can be used. The current collector may be covered with a known protective layer. Moreover, you may process the surface of an electrical power collector by a well-known method. The current collector can take a form such as a foil, a sheet, a film, a line, a bar, or a mesh. Therefore, metal foils, such as copper foil, nickel foil, aluminum foil, stainless steel foil, can be used suitably as a collector. When the current collector has a thin shape such as a foil, sheet, or film, the thickness of the current collector is preferably in the range of 1 μm to 100 μm.

  For example, in order to form a negative electrode active material layer of a negative electrode of a non-aqueous secondary battery using the negative electrode active material of the present invention, a negative electrode mixture containing a negative electrode active material is applied on a current collector, What is necessary is just to dry or harden the binder contained. As the negative electrode mixture, an appropriate amount of an organic solvent is added to and mixed with the first active material powder, the graphite particle composition, the binder, and other additives such as carbon powder if necessary. A slurry may be used. As a method for applying the slurry-like negative electrode mixture to the current collector, a roll coating method, a dip coating method, a doctor blade method, a spray coating method, a curtain coating method, or the like can be employed.

  The binder serves to bind the first active material powder, the graphite particle composition, the conductive additive and other additives directly or indirectly to the surface of the current collector. The binder is required to bind the above-mentioned active material or the like to the current collector in as small an amount as possible, but the addition amount thereof includes the first active material powder, the plate-like particle composition, the conductive auxiliary agent, and the binder. 0.5 mass%-50 mass% of what was totaled are desirable. If the added amount of the binder is less than 0.5% by mass, the moldability of the electrode may be lowered, and if it exceeds 50% by mass, the energy density of the electrode may be lowered.

  Examples of the binder include polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), fluorine-containing resins such as fluororubber, imide resins such as polyimide (PI) and polyamideimide (PAI), and alkoxysilyl groups. -Containing resin, acrylic resin such as methacrylic resin (PMA), polyacrylonitrile (PAN), poly (meth) acrylic acid (PAA), modified polyphenylene oxide (PPO), polyethylene oxide (PEO), polyethylene (PE), polypropylene ( PP), polyvinyl chloride (PVC), styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC) and the like are exemplified.

  The binder preferably contains a polymer having a carboxyl group. This is because the graphite particle composition tends to be highly dispersed in a polymer having a carboxyl group. Examples of such polymers include PAA, CMC, polymethacrylic acid and the like.

  A polymer containing a carboxyl group in the molecule can be produced by polymerizing an acid monomer. Acid monomers include acrylic acid, methacrylic acid, vinyl benzoic acid, crotonic acid, pentenoic acid, angelic acid, tiglic acid, etc., acid monomers having one carboxyl group in the molecule, itaconic acid, mesaconic acid, citraconic acid, fumaric acid , Maleic acid, 2-pentenedioic acid, methylene succinic acid, allyl malonic acid, isopropylidene succinic acid, 2,4-hexadiene diacid, acetylenedicarboxylic acid, etc., acid monomers having two or more carboxyl groups in the molecule Is done. A copolymer obtained by polymerizing two or more kinds of monomers selected from these may be used.

  For example, a polymer composed of a copolymer of acrylic acid and itaconic acid as described in JP2013-065493A, and containing an acid anhydride group formed by condensation of carboxyl groups in the molecule It is also preferable to use as a binder. By using a binder made of this type of polymer, the initial efficiency and load characteristics of the secondary battery can be improved.

Since it is considered preferable that the number of carboxyl groups in the polymer molecule is large, it is also preferable to use a polymer having a plurality of the polymer chains described above in one molecule, for example, a so-called star polymer.
Other binders may be used in combination with the binder containing a polymer having a carboxyl group in the molecule. For example, within a range that does not impair the performance, fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene, and fluororubber, thermoplastic resins such as polypropylene and polyethylene, imide resins such as polyimide and polyamideimide, and alkoxysilyl group-containing You may mix polymers, such as resin.

  When polyvinylidene fluoride is used as the binder, the potential of the negative electrode can be lowered and the voltage of the power storage device can be improved. Further, the use of PAI or PAA as the binder improves the initial efficiency and the discharge capacity.

  The conductive assistant is added to increase the conductivity of the electrode. Carbon black, graphite, acetylene black (AB), ketjen black (KB: registered trademark), vapor grown carbon fiber (Vapor Carbon Carbon Fiber: VGCF), various metal particles, etc. as conductive aids Is exemplified. These may be added alone or in combination of two or more in the negative electrode active material layer. The amount of the conductive aid used is not particularly limited. However, since the negative electrode of the present invention includes a graphite particle composition having excellent conductivity, the amount of the conductive aid used may be smaller than that of a general negative electrode. . For example, the amount of the conductive auxiliary other than the graphite particle composition is preferably about 0.5 to 50 parts by mass with respect to 100 parts by mass of the first active material. If the amount of the conductive aid is too small, an efficient conductive path cannot be formed, and if it is too large, the electrode moldability may deteriorate and the energy density may be lowered. In addition, when using the silicon oxide with which the carbon material was compounded as an active material, the addition amount of a conductive support agent can be reduced or a conductive support agent can be eliminated.

  There is no restriction | limiting in particular in an organic solvent, The mixture of a some solvent may be sufficient. A mixed solvent of N-methyl-2-pyrrolidone and N-methyl-2-pyrrolidone and an ester solvent or a glyme solvent is particularly preferable. Examples of the ester solvent include ethyl acetate, n-butyl acetate, butyl cellosolve acetate, butyl carbitol acetate and the like. Examples of the glyme solvent include diglyme, triglyme, and tetraglyme.

  The negative electrode active material layer preferably contains at least one metal atom selected from Cu, Ni and Co. Since the conductivity of the negative electrode active material layer is improved by including this metal atom, the resistance of the occlusion reaction of charge carriers such as lithium is reduced, and the initial capacity of the power storage device is improved. Furthermore, since the valence of this metal can be changed, electrons are transferred following the potential change during charging / discharging, and the power storage device using the negative electrode of the present invention further improves the initial efficiency and improves the efficiency after the cycle. improves.

  The metal atom content in the negative electrode active material layer is preferably in the range of 0.01 to 10 parts by mass when the binder is 100 parts by mass. If the metal atom content is less than 0.01% by mass, the added effect is not exhibited, and if it exceeds 10% by mass, it may cause material segregation of the active material layer.

  In the negative electrode active material layer, at least a part of the plate-like graphite particles may be oriented so that the plate surface is substantially parallel to the surface of the current collector, or the orientation may be caused by the presence of other negative electrode compounds. It may have collapsed. When the orientation collapses, the surface in the direction intersecting the plate surface of the plate-like graphite particles appears in the traveling direction of the lithium ions, so that the lithium ions come into and out of the plate-like graphite particles. Discharge capacity increases.

  In addition, when the above-mentioned aromatic vinyl copolymer is adsorbed on the surface of the graphite particles, the graphite particles disperse without agglomeration in the solvent even when the graphite particles are put in the solvent. A negative electrode active material layer can be formed.

<Power storage device>
When the power storage device of the present invention is a nonaqueous electrolyte secondary battery, known positive electrodes, electrolytes, and separators that are not particularly limited can be used. The positive electrode may be anything that can be used in a non-aqueous electrolyte secondary battery. The positive electrode has a current collector and a positive electrode active material layer bound on the current collector. The positive electrode active material layer includes a positive electrode active material and a binder, and may further include a conductive additive and other additives. The positive electrode active material, the conductive additive and the binder are not particularly limited as long as they can be used in the nonaqueous electrolyte secondary battery.

As the positive electrode active material, a material capable of occluding and releasing charge carriers such as Li may be used. As the positive electrode active material, the layered compound Li _a Ni _b Co _c Mn _{d De} O _f (0.2 ≦ a ≦ 2, b + c + d + e = 1, 0 ≦ e <1, D is Li, Fe, Cr, Cu, At least one element selected from Zn, Ca, Mg, S, Si, Na, K, Al, Zr, Ti, P, Ga, Ge, V, Mo, Nb, W, La, 1.7 ≦ f ≦ 3 ), Li ₂ MnO ₃ . Further, as a positive electrode active material, a solid solution composed of a spinel such as LiMn ₂ O ₄ and a mixture of a spinel and a layered compound, LiMPO ₄ , LiMVO ₄ or Li ₂ MSiO ₄ (wherein M is Co, Ni, Mn, And a polyanionic compound represented by (selected from at least one of Fe). Furthermore, as the positive electrode active material, tavorite compound (the M a transition metal) LiMPO ₄ F, such as LiFePO ₄ F represented by, Limbo ₃ such LiFeBO ₃ (M is a transition metal) include borate-based compound represented by be able to. Any metal oxide used as the positive electrode active material may have the above composition formula as a basic composition, and a metal element contained in the basic composition may be substituted with another metal element. Further, as the positive electrode active material, a positive electrode active material that does not contain lithium ions contributing to charge / discharge, for example, sulfur alone (S), a compound in which sulfur and carbon are combined, a metal sulfide such as TiS ₂ , V ₂ O, etc. ₅ , oxides such as MnO ₂ , polyaniline and anthraquinone, compounds containing these aromatics in the chemical structure, conjugated materials such as conjugated diacetate organic materials, and other known materials can also be used. Further, a compound having a stable radical such as nitroxide, nitronyl nitroxide, galvinoxyl, phenoxyl, etc. may be adopted as the positive electrode active material. When using a positive electrode active material that does not contain lithium, it is necessary to add ions to the positive electrode and / or the negative electrode in advance by a known method. Here, in order to add the ion, a metal or a compound containing the ion may be used.
The current collector for the positive electrode may be any material generally used for the positive electrode of a lithium ion secondary battery, such as aluminum, nickel, and stainless steel, and is otherwise the same as the current collector for the negative electrode. The same conductive aids as those described for the negative electrode can also be used.

  When the power storage device of the present invention is a lithium ion secondary battery, the negative electrode can be pre-doped with Li as a charge carrier. In order to pre-dope Li for the negative electrode, for example, an electrode formation method in which a half cell is assembled using metallic lithium for the counter electrode and metallic lithium is used for the counter electrode, and electrochemically doped with lithium can be used. Alternatively, a metal lithium foil may be attached to the surface of the negative electrode. The doping amount of Li is not particularly limited.

The electrolytic solution includes a nonaqueous solvent and an electrolyte (also referred to as a supporting electrolyte or a supporting salt) dissolved in the nonaqueous solvent. For example, in the case of a lithium ion secondary battery, the electrolytic solution is obtained by dissolving a lithium metal salt that is an electrolyte in an organic solvent. In the power storage device of the present invention, the electrolytic solution is not particularly limited. For example, cyclic esters, chain esters, ethers and the like can be used as the non-aqueous solvent. Examples of cyclic esters include ethylene carbonate, propylene carbonate, butylene carbonate, gamma butyrolactone, vinylene carbonate, 2-methyl-gamma butyrolactone, acetyl-gamma butyrolactone, and gamma valerolactone. Examples of chain esters include dimethyl carbonate, diethyl carbonate, dibutyl carbonate, dipropyl carbonate, ethyl methyl carbonate, propionic acid alkyl ester, malonic acid dialkyl ester, and acetic acid alkyl ester. Examples of ethers include tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-diethoxyethane, and 1,2-dibutoxyethane. As the non-aqueous solvent, a compound in which part or all of hydrogen in the chemical structure of the specific solvent is substituted with fluorine may be employed.
More preferably, the non-aqueous solvent is an aprotic organic solvent, such as propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC). It is preferable to use one or more selected from the above.
Examples of the electrolyte dissolved in these non-aqueous solvents include lithium salts such as LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiI, LiClO ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ .

As the electrolytic solution, for example, a lithium metal salt such as LiClO ₄ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ or the like in a non-aqueous solvent such as ethylene carbonate, dimethyl carbonate, propylene carbonate, dimethyl carbonate or the like is used in an amount of 0.5 mol / L to 1. A solution dissolved at a concentration of about 7 mol / L can be used.

A separator is used in the power storage device as necessary. The separator separates the positive electrode and the negative electrode, and allows passage of charge carriers while preventing a short circuit of current due to contact between both electrodes. If necessary, a separator capable of holding an electrolytic solution can also be selected.
The type of the separator is not particularly limited. For example, polyethylene, polypropylene, polytetrafluoroethylene, polyimide, polyamide, polyaramid (aromatic polymer), polyester, polyacrylonitrile or other synthetic resin, cellulose, amylose or other polysaccharide, fibron, keratin, etc. Examples thereof include microporous materials, porous materials, non-woven fabrics, woven fabrics, and the like using one or more kinds of electrically insulating materials such as natural polymers such as lignin and suberin and ceramics. These preferably have a thin shape such as a sheet shape, a film shape, or a foil shape, and may have a single layer structure or a multilayer structure.

  In the power storage device of the present invention, a separator may be interposed between the positive electrode and the negative electrode as necessary. There is no particular limitation on the shape of the electrode body having the positive electrode, the negative electrode and, if necessary, the separator, and it can be any of a stacked type in which the positive electrode, the separator and the negative electrode are stacked, or a wound type in which the positive electrode, the separator and the negative electrode are sandwiched. May be. For example, if the power storage device of the present invention is a battery, after connecting between the positive electrode current collector and the negative electrode current collector to the positive electrode terminal and the negative electrode terminal connected to the outside using a current collecting lead or the like, What is necessary is just to seal an electrode body in a battery case with electrolyte solution. In addition, the power storage device of the present invention may be charged and discharged within a voltage range suitable for the type of active material included in the electrode.

  The shape of the power storage device of the present invention is not particularly limited. For example, when the power storage device of the present invention is a lithium ion secondary battery, various shapes such as a cylindrical shape, a square shape, a coin shape, and a laminate shape can be employed.

  The power storage device of the present invention may be mounted on a vehicle, for example. The vehicle may be a vehicle that uses electric energy from a power storage device such as a lithium ion secondary battery for all or a part of its power source, for example, an electric vehicle, a hybrid vehicle, or the like. When a lithium ion secondary battery is mounted on a vehicle, a plurality of lithium ion secondary batteries may be connected in series to form an assembled battery.

  Hereinafter, embodiments of the present invention will be specifically described.

Example 1
<Preparation of graphite particle-polymer composite>
1 g of styrene (ST), 1 g of 2-vinylpyridine (VP), 10 mg of azobisisobutyronitrile (AIBN) and 5 ml of toluene were mixed, and a polymerization reaction was performed at 60 ° C. for 6 hours in a nitrogen atmosphere. After standing to cool, it refine | purified by reprecipitation using chloroform-ether, and 1.0-g ST-VP (50:50) random copolymer was obtained. The number average molecular weight (Mn) of this ST-VP (50:50) random copolymer was 40,000. The molar ratio of ST to VP was 1: 1. This random copolymer corresponds to an aromatic vinyl copolymer. In this aromatic vinyl copolymer, styrene corresponds to an aromatic monomer unit, and vinylpyridine corresponds to a basic monomer unit. Vinylpyridine, the organic group of the basic monomer unit, is pyridine.

Here, the number average molecular weight (Mn) was measured under the following conditions using gel permeation chromatography (“Shodex GPC101” manufactured by Showa Denko KK).
Column: Shodex GPC K-805L and Shodex GPC K-800RL (both manufactured by Showa Denko KK)
・ Eluent: Chloroform ・ Measurement temperature: 25 ° C.
Sample concentration: 0.1 mg / ml
・ Detection means: RI
In addition, the number average molecular weight (Mn) showed the value converted with standard polystyrene.

20 mg of graphite particles (“EXP-P” manufactured by Nippon Graphite Industries Co., Ltd., particle size 100 to 600 μm), urea-hydrogen peroxide inclusion complex 80 mg, 20 mg of the above ST-VP (50:50) random copolymer and N , N-dimethylformamide (DMF) 2 ml was mixed and subjected to ultrasonic treatment (output: 250 W) at room temperature for 5 hours to obtain a dispersion of plate-like graphite particles and ST-VP random copolymer. The dispersion is filtered, and the filtrate is washed with dimethylformamide (DMF) and then vacuum-dried to obtain an aggregate of graphite particles-polymer composite containing plate-like graphite and aromatic vinyl copolymer, that is, graphite particles. A composition was obtained.
When the graphite particle-polymer composite constituting the graphite particle composition was observed with a scanning electron microscope (SEM), the major axis of the plate-like graphite particles was 10 μm to 20 μm, the minor axis was 3 μm to 10 μm, and the thickness was 30 nm to 80 nm. Met. Further, when the amount of the polymer was measured by thermogravimetry / differential thermal analysis (TG-DTA), it was confirmed that 3% by mass of the polymer was adsorbed with respect to 100% by mass of the graphite particle composition.

<Preparation of cationized complex>
1,4-Diiodobutane was dissolved in NMP to prepare an NMP solution containing 10% by mass of 1,4-diiodobutane.
1 g of the aggregate of the above graphite particle-polymer complex was taken and added to 10 ml of acetonitrile at room temperature. A mixture of acetonitrile and an aggregate of graphite particles-polymer composite was stirred at room temperature to form a suspension. 0.07 ml of the NMP solution containing 1,4-diiodobutane described above was added to this suspension, and the mixture was stirred at 80 ° C. for 24 hours in the dark. 1,4-diiodobutane corresponds to a treating agent, and the leaving group in this treating agent is I. The amount of 1,4-diiodobutane added was 0.3 mol with respect to 1 mol of VP. The amount of 1,4-diiodobutane added to the graphite particles was 1.5% by mass when the sum of the mass of the graphite particles and the mass of 1,4-diiodobutane was 100% by mass. By this step, the treating agent and the basic monomer unit react. Specifically, it is considered that N contained in the organic group of the basic monomer unit reacts with carbon bonded to the leaving group I of the treating agent. After the elapse of 24 hours, the obtained reaction solution was vacuum-dried at 100 ° C., and acetonitrile and the like were removed to obtain the graphite particle composition of Example 1.
The treating agent used in Example 1 is 1,4-diiodobutane and has 2 moles of I or leaving group per mole of treating agent. The basic monomer unit is VP, and 1 mol of N per 1 mol of the basic monomer unit. In Example 1, 0.3 mol of 1,4-diiodobutane was reacted per mol of VP. Therefore, in Example 1, the ratio of leaving group-nucleophile element obtained by (number of leaving groups) / (number of atoms of nucleophile element) is (0.3 × 2) / 1 = 0. .6.

<Production of negative electrode>
SiO powder (manufactured by Sigma-Aldrich Japan, average particle size 5 μm) was heat-treated at 900 ° C. for 2 hours to prepare SiO _x powder having an average particle size of 5 μm. With this heat treatment, if the silicon monoxide SiO is a homogeneous solid having a ratio of Si to O of approximately 1: 1, it is separated into two phases of Si phase and SiO ₂ phase by solid internal reaction. The Si phase obtained by separation is very fine. The SiO _x powder (that is, the aggregate of SiO _x particles) obtained in this step corresponds to the first active material powder described above.

  45 parts by mass of the first active material, 22 parts by mass of natural graphite powder, 13 parts by mass of the graphite particle composition, 5 parts by mass of AB powder, and 10 parts by mass of polyacrylic acid are dispersed in NMP, and the slurry-like negative electrode composite is dispersed. An agent was prepared. This slurry-like negative electrode mixture was applied to the surface of an electrolytic copper foil (current collector) having a thickness of 20 μm by using a doctor blade to form a negative electrode mixture layer on the current collector.

  Then, the composite material which consists of a collector and a negative mix layer was dried at 80 degreeC for 20 minute (s), and NMP was volatilized and removed from the negative mix layer. After drying, the current collector and the negative electrode mixture layer were firmly bonded to each other by a roll press. This was heated in vacuum at 100 ° C. for 2 hours to obtain a negative electrode having a negative electrode active material layer thickness of about 16 μm.

<Production of lithium ion secondary battery>
A lithium ion secondary battery (half cell) for evaluation was produced using the negative electrode produced by the above procedure as an evaluation electrode. The counter electrode was a metal lithium foil (thickness 500 μm).

The counter electrode was cut to φ13 mm, the evaluation electrode was cut to φ11 mm, and a separator (Hoechst Celanese glass filter and celgard 2400) was sandwiched between them to form an electrode body battery. This electrode body battery was accommodated in a battery case (CR2032 coin cell manufactured by Hosen Co., Ltd.). Also, in the battery case, a nonaqueous electrolyte solution in which LiPF ₆ was dissolved at a concentration of 1M was injected into a mixed solvent in which ethylene carbonate and diethyl carbonate were mixed at a ratio of 1: 1 (volume ratio), and the battery case was sealed. The lithium ion secondary battery of Example 1 was obtained.

(Example 2)
The lithium ion secondary battery of Example 2 is the same as the lithium ion secondary battery of Example 1 except for the graphite particle composition. The graphite particle composition of Example 2 was produced in the same manner as Example 1 except that the concentration of the treating agent was different. In Example 2, as in Example 1, 1,4-diiodobutane was dissolved in NMP to prepare an NMP solution containing 10% by mass of 1,4-diiodobutane. Then, 1 g of an aggregate of graphite particles-polymer complex obtained in the same manner as in Example 1 was added to 10 ml of acetonitrile at room temperature, this was stirred and suspended at room temperature, and then an NMP solution containing 1,4-diiodobutane was added to 0 ml. .01 ml was added, and the mixture was stirred for 24 hours at 80 ° C. in the dark. Then, the graphite particle composition of Example 2 was obtained through the same steps as in Example 1.
In Example 2, 0.3 / (1 × 7) mole, that is, about 0.043 mole of 1,4-diiodobutane was reacted per mole of VP. Therefore, the leaving group-nucleophile element ratio in Example 2 was (0.3 × 2) / (1 × 7), that is, about 0.086.
A lithium ion secondary battery of Example 2 was obtained in the same manner as Example 1 except that the graphite particle composition of Example 2 obtained in the above steps was used.

(Example 3)
The lithium ion secondary battery of Example 3 is the same as the lithium ion secondary battery of Example 1 except for the graphite particle composition. The graphite particle composition of Example 3 was produced in the same manner as Example 1 except that the concentration of the treatment agent was different. In Example 3, as in Example 1, 1,4-diiodobutane was dissolved in N-methyl-2-pyrrolidone (NMP) to prepare an NMP solution containing 10% by mass of 1,4-diiodobutane. Then, 1 g of an aggregate of graphite particles-polymer complex obtained in the same manner as in Example 1 was added to 10 ml of acetonitrile at room temperature, this was stirred and suspended at room temperature, and then an NMP solution containing 1,4-diiodobutane was added to 0 ml. .14 ml was added, and the mixture was stirred at 80 ° C. for 24 hours in the dark. Then, the graphite particle composition of Example 3 was obtained through the same steps as in Example 1.
In Example 3, (0.3 × 2) / 1 mole = 0.6 mole 1,4-diiodobutane was reacted per mole VP. Therefore, the leaving group-nucleophile element ratio in Example 3 was (0.3 × 2 × 2) / 1, that is, about 1.2.
A lithium ion secondary battery of Example 3 was obtained in the same manner as in Example 1 except that the graphite particle composition of Example 3 obtained in the above steps was used.

Example 4
The lithium ion secondary battery of Example 4 is the same as the lithium ion secondary battery of Example 1 except for the graphite particle composition. The graphite particle composition of Example 4 was produced in the same manner as Example 1 except that the type and concentration of the treatment agent were different. In Example 4, 1-iodobutane was used as a treating agent. Then, 1-iodobutane was dissolved in N-methyl-2-pyrrolidone (NMP) to prepare an NMP solution containing 10% by mass of 1-iodobutane. And 1 g of aggregates of graphite particles-polymer complex obtained in the same manner as in Example 1 was added to 10 ml of acetonitrile at room temperature, and this was stirred and suspended at room temperature. Then, 0.04 ml of NMP solution containing 1-iodobutane was added. In addition, the mixture was stirred for 24 hours at 80 ° C. in the dark. Then, the graphite particle composition of Example 4 was obtained through the same steps as in Example 1.
Since 1-iodobutane used in Example 4 has one leaving group, the number of moles of the leaving group is the same as the number of moles of 1-iodobutane itself.
In Example 4, 0.3 mol of 1-iodobutane was reacted per 1 mol of VP. Therefore, the leaving group-nucleophile element ratio in Example 4 was (0.3 × 1) / 1, that is, about 0.3.
A lithium ion secondary battery of Example 4 was obtained in the same manner as in Example 1 except that the graphite particle composition of Example 4 obtained in the above steps was used.

(Comparative example)
The lithium ion secondary battery of the comparative example did not use a treatment agent, that is, the lithium ion secondary battery of Example 1 except that a graphite particle-polymer composite aggregate was used instead of the graphite particle composition. Same as battery.

<Evaluation test>
The initial capacity and cycle durability of the lithium ion secondary batteries of Example 1, Example 2, and Comparative Example were evaluated.
Each lithium ion secondary battery was held in a constant temperature bath at 25 ° C. for 1 hour, and then charged and discharged at a constant current of 0.1 mA and a voltage of 1.0 V to 0.01 V. The charge capacity at this time was defined as the initial capacity (mAh / g).

After the initial charge / discharge, the same charge / discharge was repeated 30 cycles. The charge capacity at the 30th cycle was defined as the charge capacity after cycle endurance (mAh / g). Based on the charge capacity after cycle endurance and the initial capacity described above, the capacity retention rate was calculated using the following formula (I).
Capacity maintenance ratio (%) = (charge capacity after cycle endurance / initial capacity) × 100 (I)
The results are shown in Table 1.

As shown in Table 1, in the lithium ion secondary batteries of Example 1 and Example 2 in which the graphite particle-polymer composite and the treatment agent were used in combination, only the graphite particle-polymer composite was used and no treatment agent was used. Compared to the lithium ion secondary battery of the comparative example, the initial capacity and capacity retention rate were excellent.
Comparing Example 1 and Example 2, the lithium ion secondary battery of Example 1 having a relatively large leaving group-nucleophile element ratio is an example having a relatively small leaving group-nucleophile element ratio. The initial capacity was larger than that of the lithium ion secondary battery of No. 2. That is, when the leaving group-nucleophile element ratio is in the range of 0.09 to 0.6, the larger the leaving group-nucleophile element ratio, that is, the ratio of the leaving group to the nucleophile element. It can be said that the larger the amount, the better the initial capacity and the better the capacity maintenance rate. Further, from this result, when the treating agent has two leaving groups, that is, when L ² _n in the above-described formula (3) is n = 1, the leaving group-nucleophile element ratio is It is particularly preferably 0.05 or more and 1.0 or less, more preferably 0.07 or more and 0.8 or less, and particularly preferably 0.09 or more and 0.6 or less.

Claims (10)

Graphite particles, an aromatic vinyl copolymer having a vinyl aromatic monomer unit represented by the following formula (1) and a basic monomer unit represented by the following formula (2), and represented by the following formula (3) And a method for producing a graphite particle composition having an action step of causing the treatment agent to act.
^{_{- (CH 2 -CHX 1) -}} ... (1)
^{_{- (CH 2 -CHX 2) -}} ... (2)
L ¹ -RL ² _n (3)
(X ¹ in formula (1) represents a phenyl group, a naphthyl group, an anthracenyl group or a pyrenyl group, and these groups may have a substituent. X ^{2 in} formula (2) is N And / or P represents an organic group, and these groups may have a substituent, R in formula (3) is an alkyl chain having 1 or more carbon atoms, and L ¹ and L ² are each a desorbed group. And is a group, n is 0 or 1, and L ¹ and L ² may be the same or different.)   Before the action step, during the action step or after the action step, plate graphite particles having a thickness of 0.3 nm to 100 nm and a major axis length of 0.1 μm to 500 μm are obtained in the presence of hydrogen peroxide. The method for producing a graphite particle composition according to claim 1, further comprising a crushing step of crushing the graphite particles. The action step is
A graphite particle-polymer composite forming step of forming a graphite particle-polymer composite having the graphite particles and the aromatic vinyl copolymer adsorbed on the surface of the graphite particles;
A treatment agent action step of causing the treatment agent to act on the graphite particle-polymer composite,
The method for producing a graphite particle composition according to claim 2, wherein the crushing step is performed simultaneously with the graphite particle-polymer complex forming step. 4. The method for producing a graphite particle composition according to claim 1, wherein L ¹ and L ² are each independently selected from chlorine, bromine, iodine mesylate, and triflate. The R includes a linear alkyl chain structure having 4 to 6 carbon atoms, and a terminal of the linear alkyl structure is bonded to the L ¹ or the L ^2. A method for producing the graphite particle composition according to Item. The X ² is selected from thiazole, thiazine, phosphole, azole, pyridine, imidazole, pyrazole, pyrazine, thiazine, pyrimidine, and quinoline. Production of the graphite particle composition according to any one of claims 1 to 5. Method. Graphite particles,
An aromatic vinyl copolymer adsorbed on the surface of the graphite particles and having a vinyl aromatic monomer unit represented by the following formula (1) and a basic monomer unit represented by the following formula (2): A graphite particle-polymer composite comprising:
A graphite particle composition comprising an alkyl chain structure derived from the treatment agent represented by the following formula (3) and interposed between the graphite particle-polymer composites at least partially adjacent to each other.
^{_{- (CH 2 -CHX 1) -}} ... (1)
^{_{- (CH 2 -CHX 2) -}} ... (2)
L ¹ -RL ² _n (3)
(X ¹ in formula (1) represents a phenyl group, a naphthyl group, an anthracenyl group or a pyrenyl group, and these groups may have a substituent. X ^{2 in} formula (2) is N And / or P represents an organic group, and these groups may have a substituent, R in formula (3) is an alkyl chain having 1 or more carbon atoms, and L ¹ and L ² are each a desorbed group. And is a group, n is 0 or 1, and L ¹ and L ² may be the same or different.)   The graphite particle composition according to claim 7, wherein the graphite particles are plate-like graphite particles having a thickness of 0.3 nm to 100 nm and a length in a major axis direction of 0.1 μm to 500 μm. An active material powder made of at least one selected from the group consisting of Si, Si compounds, Sn and Sn compounds;
A negative electrode comprising a mixed powder of the graphite particle composition according to claim 7 or 8.   A power storage device comprising the negative electrode according to claim 9.