JP2015043316A - Active material for nonaqueous secondary battery negative electrode, negative electrode arranged by use thereof, and nonaqueous secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an active material for a nonaqueous secondary battery negative electrode which is useful in manufacturing a nonaqueous secondary battery less in gas generation owing to the decomposition of a nonaqueous electrolytic solution and suppressed in the rise in resistance.SOLUTION: The present invention provides a nonaqueous secondary battery reduced in gas generation owing to the decomposition of a nonaqueous electrolytic solution and suppressed in the rise in resistance by using an active material for a nonaqueous secondary battery negative electrode. The active material for a nonaqueous secondary battery negative electrode comprises: (A) an active material which allows lithium ions to go thereinto and to be desorbed therefrom; and (B) a polymer having a polycyclic structure.

Description

  The present invention relates to a non-aqueous secondary battery negative electrode active material useful for producing an excellent non-aqueous secondary battery in which gas generation due to decomposition of a non-aqueous electrolyte solution is small and an increase in resistance is suppressed. The present invention further relates to a negative electrode for a non-aqueous secondary battery obtained using the active material and a non-aqueous secondary battery including the negative electrode.

In recent years, with the development of electric vehicles and the like, lithium ion secondary batteries, which are non-aqueous secondary batteries, have been actively studied as high energy density type batteries. For lithium ion secondary batteries, it is known to use a carbon material such as graphite as the negative electrode active material.
Among them, graphite having a high degree of graphitization, when used as an active material for a negative electrode for a lithium ion secondary battery, has a capacity close to 372 mAh / g, which is the theoretical capacity for lithium occlusion of graphite. Since it is excellent also in the property, it is known that it is preferable as an active material for negative electrodes.

  When such a carbon material is used as an active material for a negative electrode of a lithium ion secondary battery, the surface of the carbon material is usually reacted with a polymer compound used as a binder or a non-aqueous electrolyte. A protective coating called SEI (Solid Electrolyte Interface) is formed. SEI prevents contact between the carbon material and the electrolyte, and suppresses decomposition of the electrolyte by the active carbon material. As a result, it is also known that the chemical stability of the negative electrode surface is maintained.

  However, in a lithium ion secondary battery using a carbon material as an active material for a negative electrode, the charge / discharge irreversible capacity during the initial cycle increases due to the generation of SEI film and the generation of gas as a side reaction product. There was a problem that the capacity could not be increased. Furthermore, the formation of a stable SEI film increases the interfacial resistance (negative electrode resistance) of the negative electrode, resulting in a decrease in the input / output characteristics of the battery.

  In order to solve the above problem, a technique for coating a carbon material, which is a negative electrode active material, with a polymer or the like is known. For example, Patent Document 1 discloses a non-aqueous secondary battery in which a coating layer made of an ion conductive polymer or a water-soluble polymer is provided on the surface of a carbon material. According to Patent Document 1, a coating layer made of an ion conductive polymer such as polyethylene oxide or a water-soluble polymer such as polyvinyl alcohol (hydrolyzate of styrene-maleic anhydride copolymer) is formed of a non-aqueous electrolyte layer. It functions to suppress decomposition or to prevent the decomposition products of the constituent components of the nonaqueous electrolyte layer from being deposited on the negative electrode surface. It is described that this contributes to improvement of initial charge / discharge efficiency and cycle characteristics.

However, the polymers as described above have insufficient adhesion to carbon materials, and initial discharge efficiency, cycle characteristics, and stability are still insufficient.
Therefore, amino groups are attracting attention as functional groups having good adhesiveness, and Patent Document 2 discloses a carbon material obtained by attaching an organic polymer having an aliphatic amino group in a side chain to a carbon material.
In this document, polyallylamine is most preferable as an organic polymer, and the effect is to reduce the irreversible capacity when used as an active material for a non-aqueous secondary battery negative electrode by attaching an organic polymer and modifying the surface. It is stated that you can.

Patent Document 3 discloses an electrode material composed of a carbon material and an organic polymer having at least a tertiary nitrogen atom covering the carbon material in the main chain. In this document, polyethyleneimine is most preferable as an organic polymer, and it is described that the discharge characteristics can be improved by reducing the specific surface area of the carbon material.
Patent Document 4 includes, as a negative electrode active material, carbon whose surface is coated with at least a part of a water-soluble polymer material (such as polyacrylic acid) that is negatively charged in water when manufacturing a negative electrode. And non-aqueous secondary batteries using non-aqueous electrolytes containing compounds that are reduced at a higher potential than propylene carbonate. In this document, there is a general description that polystyrene sulfonic acid in which polystyrene sulfonic acid or maleic acid is copolymerized can be used as the water-soluble polymer substance.

Patent Document 5 describes that a polymer compound is contained as a dispersant for the active material.

JP-A-11-129992 JP 2002-117851 A JP 2007-95494 A JP 2002-134171 A JP 2010-61931 A

  However, according to the study by the present inventors, the polymer disclosed in Patent Document 1 is an ion conductive polymer or a water-soluble polymer, and the initial charge is achieved by coating such a polymer on a carbon material. Although it is described that the discharge efficiency and cycle characteristics are improved, the polymer is actually swollen by the electrolytic solution, and further, the adhesion of the polymer film to the carbon material is insufficient, so there is room for improvement. It was a certain technology.

  On the other hand, Patent Document 2 discloses a carbon material in which a polymer having an amino group, which is a functional group having good adhesion to the surface of the carbon material, is attached to the carbon material. When used as an active material, the initial charge / discharge efficiency is improved, but the ionic conductivity of the polymer is insufficient, and thus the negative electrode interface resistance (negative electrode resistance) tends to increase. .

  In addition, in the techniques described in Patent Documents 3 and 4, although the initial charge / discharge efficiency is somewhat improved as compared with the carbon material without any coating, the increase in the negative electrode resistance due to the coating and the reductive decomposition of the electrolyte are sufficiently suppressed. Since it was not possible, the gas generation was not suppressed and the cycle characteristics were not sufficiently improved.

Moreover, in the technique described in Patent Document 5, an electrode with reduced variation in thickness and density is created by improving the dispersibility of the active material, but the reaction between the surface of the active material and the electrolytic solution. Regarding the suppression of gas generation due to, this was a technology that could not be suppressed but had room for improvement.
The present invention has been made in view of the background art, and in a non-aqueous secondary battery, a non-aqueous secondary battery negative electrode that suppresses gas generation due to decomposition of the non-aqueous electrolyte and suppresses an increase in resistance. The objective is to provide active materials.

As a result of intensive studies to solve the above problems, the present inventors have found that an active material (A) capable of inserting / extracting lithium ions (hereinafter also referred to as “active material (A)”) and a polymer. In an active material for a negative electrode of a non-aqueous secondary battery containing a polymer, a polymer (B) having a polycyclic structure (hereinafter also referred to as “polymer (B)”) is used to suppress an increase in negative electrode resistance. However, the present inventors have found that a non-aqueous secondary battery that can improve the initial charge / discharge efficiency and gas generation suppression effect and has excellent cycle characteristics can be obtained.

Here, the details of the non-aqueous secondary battery negative electrode active material according to the present invention containing the polymer (B) exhibiting the above effects are unclear, but as a result of the inventors' investigation, the excellent battery characteristics are as follows. This is considered to be due to such an effect.
That is, when the active material layer for a non-aqueous secondary battery negative electrode contains the polymer (B) and the active material (A) having the characteristics described above, the polycyclic structure of the polymer (B) is active. It acts specifically on the surface of the substance (A) and has an effect of suppressing the activity on the surface of the active material (A). Furthermore, the polycyclic structure can impart high adsorptivity between the active material (A) surface and the polymer (B).

In addition, when the polycyclic structure has a π-conjugated structure, the polycyclic structure makes the π-conjugated structure larger than that of the monocyclic structure and further enhances the interaction with the active material (A). preferable.
In this way, the polymer (B) is selectively adsorbed on the surface of the active material (A), particularly, in the case of graphite, so that the polymer (B) is prevented from blocking the edge surface of the graphite. Therefore, the increase in resistance due to the polymer (B) can be reduced.

That is, the gist of the present invention is for a non-aqueous secondary battery negative electrode comprising an active material (A) capable of inserting and removing lithium ions and a polymer (B) having a polycyclic structure. It exists in the active material.
Another aspect of the present invention resides in a negative electrode for a non-aqueous secondary battery, which is formed using the active material for a negative electrode for a non-aqueous secondary battery.

  Another aspect of the present invention is a non-aqueous secondary battery including a positive electrode and a negative electrode capable of inserting and extracting lithium ions, and an electrolyte, wherein the negative electrode is the negative electrode for the non-aqueous secondary battery. It exists in the non-aqueous secondary battery characterized by this.

  According to the present invention, there is provided an excellent non-aqueous secondary battery negative electrode active material that has a low resistance and is useful for producing a non-aqueous secondary battery that is excellent in suppressing gas generation due to decomposition of a non-aqueous electrolyte. can do. Moreover, the non-aqueous secondary battery provided with the said negative electrode for non-aqueous secondary batteries using the said active material for non-aqueous secondary battery negative electrodes, and the said negative electrode can be provided.

Hereinafter, the contents of the present invention will be described in detail. In addition, the following description is an example (representative example) of the embodiment of this invention, and this invention is not specified to these forms, unless the summary is exceeded.
The non-aqueous secondary battery negative electrode active material of the present invention is characterized by containing at least an active material (A) and a polymer (B).

<Active material (A)>
The active material (A) is not particularly limited as long as it is a material that can occlude and release lithium ions in its skeleton.
Examples thereof include graphite, amorphous carbon, various carbon materials typified by carbonaceous materials having a low degree of graphitization, silicon-based materials, and tin-based materials. Although these will be described in detail, lithium storage capacity, cycle characteristics, and cost balance are at least one selected from the group consisting of artificial graphite, natural graphite, amorphous carbon, silicon, and silicon oxide. To preferred. Further, those coated with a carbonaceous material (amorphous carbon or graphitized material) may be used.

In this invention, these can be used individually or in combination of 2 or more types. The material may contain an oxide or other metal.
The shape of the active material (A) is not particularly limited, and can be appropriately selected from spherical, flaky, fibrous, amorphous particles, etc., but is preferably flaky and spherical, more preferably spherical. It is.
Examples of the carbon material include artificial graphite, natural graphite, amorphous carbon, a carbonaceous material having a low degree of graphitization, and a material obtained by coating the carbon material with a carbonaceous material. From the viewpoint of high affinity with the molecule (B), low cost, and ease of electrode preparation, artificial graphite or natural graphite or a material obtained by coating them with a carbonaceous material is preferable, and natural graphite is particularly preferable from the viewpoint of cost. Further, artificial graphite obtained by graphitizing bulk mesophase or a material obtained by coating them with a carbonaceous material is preferable, and natural graphite or a material obtained by coating them with a carbonaceous material is more preferable.

These carbon materials preferably have few impurities, and are used after being subjected to various purification treatments as necessary.
Examples of the natural graphite include scaly graphite, scaly graphite, and soil graphite. The production area of the scaly graphite is mainly Sri Lanka, the production area of the scaly graphite is mainly Madagascar, China, Brazil, Ukraine, Canada, etc. Such as Mexico.

  Among these natural graphites, soil graphite generally has a small particle size and low purity. On the other hand, scaly graphite and scaly graphite have advantages such as a high degree of graphitization and a low amount of impurities, and therefore can be preferably used in the present invention.

  The shape of the natural graphite is preferably spherical from the viewpoint of exhibiting the effects of the present invention, and particularly preferably spherical natural graphite as the active material (A).

More specifically, it is spheroidized natural graphite obtained by subjecting highly purified scale-like natural graphite to spheronization treatment. The method for the spheroidizing process will be described later.
As the raw material for the artificial graphite and amorphous carbon, graphitizable carbon and non-graphitizable carbon can be used. For example, coal tar pitch, coal heavy oil, atmospheric residue, petroleum heavy oil, aromatic hydrocarbon, nitrogen-containing cyclic compound, sulfur-containing cyclic compound, polyphenylene, polyvinyl chloride, polyvinyl alcohol, polyacrylonitrile, Examples include those obtained by firing organic substances such as polyvinyl butyral, natural polymer, polyphenylene sulfide, polyphenylene oxide, furfuryl alcohol resin, phenol-formaldehyde resin, and imide resin at a predetermined temperature.

The artificial graphite can be obtained by graphitizing a raw material containing a large amount of graphitizable carbon in a range of 2500 ° C. or higher and 3200 ° C. or lower. During firing, a silicon-containing compound or a boron-containing compound is graphitized as a catalyst. Can also be used.
The amorphous carbon can be obtained by baking non-graphitizable carbon or a carbon precursor that has been infusibilized to inhibit graphitization at 600 ° C. or higher and 3200 ° C. or lower.
Furthermore, the amorphous carbon can also be easily graphitized carbon. Examples of the carbonaceous material having a small degree of graphitization in that case include those obtained by firing an organic material at a temperature usually less than 2500 ° C. Organic substances include coal-based heavy oil such as coal tar pitch and dry distillation liquefied oil; straight-run heavy oil such as atmospheric residual oil and vacuum residual oil; ethylene tar produced as a by-product during thermal decomposition of crude oil, naphtha, etc. Heavy oils such as cracked heavy oils; aromatic hydrocarbons such as acenaphthylene, decacyclene and anthracene; nitrogen-containing cyclic compounds such as phenazine and acridine; sulfur-containing cyclic compounds such as thiophene; and aliphatic cyclics such as adamantane Compounds: Polyphenylene such as biphenyl and terphenyl; Polyvinyl esters such as polyvinyl chloride, polyvinyl acetate, and polyvinyl butyral; Thermoplastic polymers such as polyvinyl alcohol, and the like.

Depending on the degree of graphitization of the carbonaceous material, the firing temperature can usually be 600 ° C. or higher, preferably 900 ° C. or higher, more preferably 950 ° C. or higher, and usually lower than 2500 ° C. , Preferably it is 2000 degrees C or less, More preferably, it is the range of 1400 degrees C or less.
At the time of firing, acids such as phosphoric acid, boric acid and hydrochloric acid, alkalis such as sodium hydroxide and the like can be mixed with the organic matter.

Examples of the silicon-based material include silicon and silicon oxide. Specifically, any of SiO _y , SiC _x O _y (wherein x and y may be any ratio), a silicon-silicon oxide composite, or an alloy of silicon and other metals may be used. Of these, silicon (Si) and silicon oxide are preferable from the viewpoint of lithium storage capacity and cycle characteristics.
As the silicon-based material, a form capable of relieving volume expansion and contraction during lithium insertion / extraction, such as a small particle size, thin film, and porous structure, is preferable, and is used in combination with a carbon material or other active material as necessary. be able to.

  As the tin-based material, any of tin, stannous oxide, stannic oxide, and tin amorphous alloy may be used. The tin-based material is preferably in a form that can relieve volume expansion and contraction during lithium insertion and desorption, such as small particle size, thin film, and porous structure, and can be combined with various carbon materials and other active material materials as necessary. And use.

  Next, various physical properties of the active material (A) will be described. The active material (A) preferably satisfies at least one of the following physical properties.

(Average particle diameter (d50))
The average particle diameter (d50) of the active material (A) is usually 1 μm or more, preferably 4 μm or more, more preferably 10 μm or more, and usually 50 μm or less, preferably 30 μm or less, more preferably 25 μm or less. Within this range, it is possible to prevent inconveniences in the process, such as striation of the negative electrode forming material, when forming a plate at the time of manufacturing the negative electrode.

  In the present specification, the average particle diameter (d50) means a volume-based median diameter. Specifically, 0.01 g of a sample is suspended in 10 mL of a 0.2% by mass aqueous solution of polyoxyethylene sorbitan monolaurate, which is a surfactant, and introduced into a commercially available laser diffraction / scattering particle size distribution analyzer. After irradiating a 28 kHz ultrasonic wave with an output of 60 W for 1 minute, it can be obtained as a value measured as a volume-based median diameter in a measuring apparatus.

(Tap density)
The tap density of the active material (A) is usually 0.7 g / cm ³ or more, 1.0 g / cm ³ or more. Moreover, it is 1.3 g / cm < ³ > or less normally, and 1.1 g / cm < ³ > or less is preferable.
If the tap density is too low, the high-speed charge / discharge characteristics are inferior when used for a negative electrode for a non-aqueous secondary battery. On the other hand, if the tap density is too high, the active material (A) in the particles that are the material constituting the negative electrode In some cases, the negative electrode forming material lacks rollability and it is difficult to form a high-density negative electrode sheet.

In the present invention, the tap density is 1.6 cm in diameter and volume capacity 2 using a powder density measuring device.
After dropping the sample into a 0 cm ³ cylindrical tap cell through a sieve having a mesh opening of 300 μm and filling the cell to the full, a tap with a stroke length of 10 mm was performed 1000 times, and the density determined from the volume after the tapping and the weight of the sample Is defined as the tap density.

(BET specific surface area (SA))
The specific surface area (BET method specific surface area) measured by the BET method of the active material (A) is usually 1 m ² / g or more, preferably 1.2 m ² / g or more, more preferably 1.5 m ² / g or more. In general, it is 11 m ² / g or less, preferably 10 m ² / g or less, more preferably 9 m ² / g or less, and still more preferably 8 m ² / g or less. If it is in this range, the portion where Li ions enter and exit is sufficient, so that even when used for a negative electrode for a non-aqueous secondary battery, good high-speed charge / discharge characteristics and output characteristics can be obtained, and the active material with respect to the electrolyte solution can be obtained. It is possible to control the activity, reduce the initial irreversible capacity, and easily increase the capacity. Moreover, since the elution amount of the polymer (B) can be reduced, gas generation and volume reduction due to side reactions can be suppressed.
In the present specification, the BET method specific surface area is a value measured by a BET 5-point method by a nitrogen gas adsorption flow method using a specific surface area measuring device.

(X-ray parameters)
When the active material (A) is a carbon material, a surface spacing _{d 002} of the carbon material by X-ray wide angle diffraction method (002) plane is generally 0.335nm or more and less than 0.340 nm, preferably 0.339nm or less More preferably, it is 0.337 nm or less. When the d ₀₀₂ value is less than 0.340 nm, appropriate crystallinity is obtained, and an increase in initial irreversible capacity can be suppressed when used for a negative electrode for a non-aqueous secondary battery. Note that 0.335 nm is a theoretical value of graphite.
When the active material (A) is a carbon material, the crystallite size (Lc) of the carbon material is usually 30 nm or more, preferably 50 nm or more, more preferably 100 nm or more. Below this range, the crystallinity decreases and the discharge capacity of the battery tends to decrease.

(Raman R value)
When the active material (A) is a carbon material, the Raman R value of the carbon material is measured and the intensity _{I A} of the peak _{P A} in the vicinity of 1580 cm ^-1, and an intensity _{I B} of a peak _{P B} in the vicinity of 1360 cm ^-1 Then, the intensity ratio R (R = I _B / I _A ) is calculated and defined. The R value is usually 0.01 or more and 1 or less, preferably 0.6 or less. When the Raman R value is less than this range, the crystallinity of the particle surface becomes too high, and when the density is increased, the crystals tend to be oriented in the direction parallel to the electrode plate, and the load characteristics tend to be lowered. On the other hand, if it exceeds this range, the crystallinity of the particle surface will be disturbed, the reactivity with the electrolyte will increase, and when used as a negative electrode for non-aqueous secondary batteries, there is a tendency to cause a decrease in efficiency and an increase in gas generation. is there.

The Raman spectrum can be measured with a Raman spectrometer. Specifically, the sample particles are naturally dropped into the measurement cell to fill the sample, and the measurement cell is irradiated with an argon ion laser beam while rotating in a plane perpendicular to the laser beam irradiated to the measurement cell. Make measurements.
Argon ion laser light wavelength: 532 nm
Laser power on sample: 25 mW
Resolution: 4cm ^-1
Measurement range: 1100 cm ^{−1 to} 1730 cm ⁻¹
Peak intensity measurement, peak half-width measurement: background processing, smoothing processing (convolution 5 points by simple averaging)

(Method for producing active material (A))
The active material (A) described above can be produced by various known methods, and the production method is not particularly limited. Here, the manufacturing method from natural graphite is demonstrated about the spheroidized natural graphite preferably used as an active material (A) in this invention.

Spherical natural graphite is obtained by spheronizing natural graphite. As an apparatus used for the spheronization treatment, for example, an apparatus that repeatedly gives mechanical action such as compression, friction, shearing force, etc. including the interaction of particles mainly with impact force to the particles can be used.
Specifically, it has a rotor with a large number of blades installed inside the casing, and the rotor rotates at high speed, so that the natural graphite raw material introduced into the casing is mechanically compressed such as impact compression, friction, shear force, etc. An apparatus that provides an action and performs surface treatment is preferable.

By applying the spheroidizing treatment, the scaly natural graphite is folded or the peripheral edge portion is spherically pulverized, so that the base particles become spherical. The fine particles of 5 μm or less generated by pulverization adhere to the base particles. In addition, it is preferable to perform the spheronization treatment under the condition that the surface functional group amount O / C value of the natural graphite after the spheronization treatment is usually 1% or more and 4% or less.
In this case, it is preferable to perform the spheronization treatment in an active atmosphere so that the oxidation reaction of the natural graphite surface can be advanced by the energy of the mechanical treatment and acidic functional groups can be introduced into the natural graphite surface. For example, when processing using the above-mentioned apparatus, the peripheral speed of the rotating rotor is usually 30 to 100 m / sec, preferably 40 to 100 m / sec, and more preferably 50 to 100 m / sec. .

(Coating treatment)
As for the active material (A) used for this invention, at least one part of the surface may be coat | covered with the carbonaceous material. The aspect of this coating can be confirmed with a scanning electron microscope (SEM) photograph or the like.
The carbonaceous material used for the coating treatment includes amorphous carbon and graphitized material, and those obtained are different depending on the difference in the firing temperature in the coating treatment described later.

Specifically, the material described in the following (1) or (2) is preferable as the carbon precursor of the carbonaceous material.
(1) Coal heavy oil, DC heavy oil, cracked heavy oil, aromatic hydrocarbon, N ring compound, S ring compound, polyphenylene, organic synthetic polymer, natural polymer, thermoplastic resin and At least one carbonizable organic substance selected from the group consisting of thermosetting resins;

(2) A material obtained by dissolving the carbonizable organic substance shown in (1) above in a low molecular organic solvent.
Among the above (1) and (2), coal-based heavy oil, direct-current heavy oil, cracked petroleum heavy oil, or those obtained by dissolving these in a low-molecular organic solvent is a carbonaceous material after firing. It is more preferable because it is uniformly coated.
In the coating treatment, for example, when spheroidized natural graphite is used as the active material (A) to form nuclear graphite, carbon precursors for obtaining carbonaceous materials are used as coating raw materials, and these are mixed and fired to obtain carbon. An active material (A) coated with a material is obtained.

When the firing temperature is usually 600 ° C. or higher, preferably 700 ° C. or higher, more preferably 900 ° C. or higher, usually 2000 ° C. or lower, preferably 1500 ° C. or lower, more preferably 1200 ° C. or lower, amorphous carbon is obtained as a carbonaceous material. It is done.
When heat treatment is performed at a firing temperature of usually 2000 ° C. or higher, preferably 2500 ° C. or higher and usually 3200 ° C. or lower, a graphitized product is obtained as a carbonaceous material.
The amorphous carbon is carbon having low crystallinity, and the graphitized material is carbon having high crystallinity.

<Polymer (B)>
Next, the polymer (B), which is a constituent component of the active material for a non-aqueous secondary battery negative electrode of the present invention, will be described.
The polymer (B) is a polymer having a polycyclic structure. The polymer (B) is considered to particularly effectively attach and / or coat the active material (A) in the active material for a non-aqueous secondary battery negative electrode of the present invention.
When the polymer (B) is used in a negative electrode for a non-aqueous secondary battery, it suppresses the reaction between the active material (A) and the non-aqueous electrolyte and effectively suppresses gas generation.
In this specification, the polycyclic structure is a functional group having a skeleton of a polycyclic compound.

The polycyclic structure of the polymer (B) of the present invention preferably has a π-conjugated structure. Since the polycyclic structure has a π-conjugated structure, the wide π-conjugated structure acts on the π-plane structure portion of the active material (A), so that it is selective to the π-plane structure portion of the active material (A) surface. Therefore, it is considered that the generation of gas is effectively suppressed and the negative electrode resistance is hardly increased.
In this specification, a π-conjugated structure is an unsaturated cyclic compound having a structure in which atoms having π electrons are arranged in a ring, satisfying the Hückel rule, and π electrons are delocalized on the ring. Is defined as

Examples of the polycyclic structure in the present invention include a polycyclic hydrocarbon group, a polycyclic heterocyclic group, a polycyclic aromatic ring group, and a polycyclic aromatic heterocyclic group. From the viewpoint of high affinity with the active material (A), a polycyclic aromatic ring group or a polycyclic aromatic heterocyclic group is preferable.
Specific examples of the polycyclic structure include bicyclic 4-membered ring + 6-membered ring benzocyclobutene, bicyclic 5-membered ring + 6-membered ring benzofuran, isobenzofuran, indole, isoindole, benzothiophene , Benzophosphole, benzimidazole, purine, indazole, benzoxazole, benzisoxazole, benzothiazole, indene; bicyclic 6-membered + 6-membered naphthalene, quinoline, isoquinoline, quinoxaline, quinazoline, cinnoline, biphenyl; Ring or higher anthracene, tetracene, pentanesene, hexacene, heptacene, pyrene, picene, phenanthrene, chrysene, triphenylene, tetraphene, pentaphene, perylene, helicene, coronene, obalene, corannulene, triphenylmethane, phenanthrene Rufutarein include rings having a skeleton of benzopyrene.

  Among these, benzocyclobutene, benzofuran, isobenzofuran, indole, isoindole, benzothiophene, benzophosphole, benzimidazole, from the viewpoint of suppressing gas generation when used for a negative electrode for a non-aqueous secondary battery Rings having a skeleton such as purine, indazole, benzoxazole, benzoisoxazole, benzothiazole, naphthalene, anthracene, tetracene, pentanecene, biphenyl are preferable, and naphthalene, anthracene, tetracene, pentanecene, biphenyl are preferable in terms of adsorptivity to active materials. Are more preferable, and naphthalene and anthracene are more preferable.

In addition to the polycyclic structure, the polymer (B) of the present invention preferably further has an ionic group. Since the ionic group has a low affinity with the non-aqueous electrolyte, it is hardly soluble in the non-aqueous electrolyte. For this reason, the resistance of the active material for a non-aqueous secondary battery negative electrode of the present invention to the non-aqueous electrolyte is improved, and the polymer (B) adsorbed on the active material (A) is less likely to be eluted into the non-aqueous electrolyte.
An ionic group is a group capable of generating an anion or cation in water. Examples thereof include a carboxylic acid group, a sulfonic acid group, a phosphoric acid group, a phosphonic acid group, a primary amino group, a secondary amino group, and a tertiary. Examples include amino groups, quaternary ammonium groups, and salts thereof. Examples of the salt of the anionic polymer include lithium salt, sodium salt, potassium salt, calcium salt, magnesium salt, ammonium salt, etc. Among these, lithium salt and sodium salt are preferable and particularly preferable because of high hydrophilicity. Is the sodium salt. Examples of the salt of the cationic polymer include formate, acetate, hydrochloride, sulfate, alkyl sulfate, amide sulfate and the like.

Among these, from the viewpoint of initial irreversible capacity when used for a negative electrode for a non-aqueous secondary battery, a carboxylic acid group, a sulfonic acid group, or a lithium salt or a sodium salt thereof is preferable as the anionic group. As the cationic group, a primary amino group, a secondary amino group or an acetate thereof is preferable.
In the present specification, “slightly soluble in a non-aqueous electrolyte” means that a polymer (B) is mixed with a solvent obtained by mixing ethyl carbonate (EC) and ethyl methyl carbonate (EMC) at a volume ratio of 3: 7. It is defined that the dry weight reduction rate before and after the immersion is 10% by mass or less.

Examples of the monomer serving as the structural unit constituting the polymer (B) include a monomer having a polycyclic structure. Furthermore, a monomer having an ionic group may be used, and a monomer having both an ionic group and a polycyclic structure may be used.
In this case, the polymer (B) may be a polymer of a monomer having a polycyclic structure, a monomer having an ionic group and not having a polycyclic structure, and a polymer having a polycyclic structure. Further, it may be a copolymer with a monomer having no ionic group, or may be a polymer of a monomer having both an ionic group and a polycyclic structure. Moreover, the mixture of the polymer of the monomer which has an ionic group, and the polymer of the monomer which has a polycyclic structure may be sufficient.

Among them, the polymer (B) has both an ionic group and a polycyclic structure from the viewpoint of the stability of the polymer (B) coated with the non-aqueous secondary battery negative electrode active material in the electrolytic solution. A monomer polymer is preferred.
The ionic group possessed by the monomer is the same as the ionic group in the polymer (B) described above. Among them, a carboxylic acid group, a sulfonic acid group, or a salt thereof has stability and resistance in the battery. It is preferable from the viewpoint of suppression of increase.

  Examples of monomers having an ionic group and a polycyclic structure include naphthalene carboxylic acid, vinyl naphthalene carboxylic acid, naphthalene sulfonic acid, vinyl naphthalene sulfonic acid, vinyl aminonaphthalene, anthracene carboxylic acid, vinyl anthracene carboxylic acid, anthracene sulfone. Examples thereof include acid, vinylanthracenesulfonic acid, vinylaminoanthracene or a salt thereof.

Examples of monomers having an ionic group and not having a polycyclic structure include vinyl sulfonic acid, lithium vinyl sulfonate, sodium vinyl sulfonate, acrylic acid, sodium acrylate, lithium acrylate, methacrylic acid, methacrylic acid. Examples thereof include sodium acid and lithium methacrylate.
Examples of the monomer having a polycyclic structure and having no ionic group include vinyl benzocyclobutene, vinyl naphthalene, vinyl anthracene, and vinyl tetracene.

Specific examples of the polymer containing a structural unit derived from such a monomer include polyvinyl benzocyclobutene, vinyl benzocyclobutene-styrene sulfonic acid copolymer, vinyl benzocyclobutene-vinyl sulfonic acid copolymer, vinyl Benzocyclobutene-acrylic acid copolymer, vinyl benzocyclobutene-methacrylic acid copolymer, polyvinyl naphthalene carboxylic acid, polyvinyl naphthalene sulfonic acid, polyvinyl amino naphthalene, polyvinyl naphthalene sulfonic acid, vinyl naphthalene-acrylic acid copolymer, vinyl Naphthalene-methacrylic acid copolymer, vinyl naphthalene-vinyl sulfonic acid copolymer, vinyl naphthalene-styrene sulfonic acid copolymer, vinyl naphthalene sulfonic acid-styrene sulfonic acid copolymer, vinyl naphthalene Rubonic acid-styrenesulfonic acid copolymer, vinylnaphthalenesulfonic acid-styrenesulfonic acid copolymer, naphthalenesulfonic acid formalin condensate, polyvinylanthracene-carboxylic acid, polyvinylanthracenesulfonic acid, polyvinylaminoanthracene, polyvinylanthracenecarboxylic acid, polyvinyl Anthracenesulfonic acid, polyvinylaminoanthracene, vinylanthracene-acrylic acid copolymer, vinylnaphthalene-methacrylic acid copolymer, vinylanthracene-vinylsulfonic acid copolymer, vinylanthracene-styrenesulfonic acid copolymer, vinylanthracenesulfonic acid -Styrenesulfonic acid copolymer, vinylanthracenecarboxylic acid-styrenesulfonic acid copolymer, vinylanthracenesulfonic acid-styrenesulfone Acid copolymers, anthracene sulfonic acid formaldehyde condensate, and their salts.

  Vinyl benzocyclobutene-styrene sulfonic acid copolymer, vinyl benzocyclobutene-vinyl sulfonic acid copolymer, vinyl benzocyclobutene-acrylic acid copolymer, vinyl benzocyclobutene- Methacrylic acid copolymer, polyvinyl naphthalene carboxylic acid, polyvinyl amino naphthalene, polyvinyl naphthalene sulfonic acid, vinyl naphthalene-vinyl sulfonic acid copolymer, vinyl naphthalene-styrene sulfonic acid copolymer, vinyl naphthalene sulfonic acid-styrene sulfonic acid copolymer Polymer, vinyl naphthalenecarboxylic acid-styrenesulfonic acid copolymer, naphthalenesulfonic acid formalin condensate, polyvinylanthracenecarboxylic acid, polyvinylanthracenesulfonic acid, polyvinylaminoanthracene, Nylanthracene-vinyl sulfonic acid copolymer, vinyl anthracene-styrene sulfonic acid copolymer, vinyl anthracene sulfonic acid-styrene sulfonic acid copolymer, vinyl anthracene carboxylic acid-styrene sulfonic acid copolymer, vinyl anthracene sulfonic acid-styrene A sulfonic acid copolymer, an anthracene sulfonic acid formalin condensate, and a salt thereof are preferable.

  Further, vinyl benzocyclobutene-styrene sulfonic acid copolymer, polyvinyl naphthalene sulfonic acid, polyvinyl amino naphthalene, polyvinyl naphthalene sulfonic acid, vinyl naphthalene-styrene sulfonic acid copolymer, vinyl naphthalene sulfonic acid-styrene sulfonic acid copolymer, Vinylnaphthalenecarboxylic acid-styrenesulfonic acid copolymer, naphthalenesulfonic acid formalin condensate, polyvinylanthracenecarboxylic acid, polyvinylanthracenesulfonic acid, polyvinylaminoanthracene, vinylanthracene-styrenesulfonic acid copolymer, vinylanthracenesulfonic acid-styrenesulfone Acid copolymer, vinylanthracenecarboxylic acid-styrenesulfonic acid copolymer, vinylanthracenesulfonic acid-styrenesulfonic acid copolymer Anthracene sulfonic acid formalin condensate and salts thereof are more preferable. Vinyl benzocyclobutene-styrene sulfonic acid copolymer, naphthalene sulfonic acid formalin condensate, and lithium salts and sodium salts thereof are active material surfaces, particularly graphite. This is particularly preferable because of its high adsorptivity to the basal surface and little elution into the electrolyte.

Also, the function can be expressed by introducing the above polycyclic structure by polymer reaction. Examples thereof include those obtained by reacting the polymer or copolymer described below with a compound having a polycyclic structure.
Examples of the polymer or copolymer used in the polymer reaction include polychlorostyrene, polychloromethylstyrene, polyvinylbenzyl chloride, polybenzoic acid, polyacrylic acid, polymethacrylic acid, polyallylamine, polyvinylamine, polyvinyl alcohol, Examples thereof include polymers such as cellulose, starch, carboxymethylcellulose, chitin, chitosan, collagen and gelatin, copolymers containing these in part, and salts thereof. Among these, polychlorostyrene, polychloromethylstyrene, polyvinyl benzyl chloride, polybenzoic acid, polyacrylic acid, polymethacrylic acid, polyallylamine, polyvinylamine, polyvinyl alcohol, cellulose, starch, carboxymethylcellulose, chitin, chitosan or these Are preferably included, and salts thereof. Chlorostyrene-styrene sulfonic acid copolymer, chloromethyl styrene-styrene sulfonic acid copolymer, polyvinyl benzyl chloride, because of its high adsorptivity to the active material surface, especially the graphite basal surface, and little elution into the electrolyte. -Styrene sulfonic acid copolymer and its salt are more preferable, and chloromethylstyrene-styrene sulfonic acid copolymer and its lithium salt and sodium salt are particularly preferable.

  Examples of the compound having a polycyclic structure used in the polymer reaction include naphthalene chloride, aminonaphthalene, aminonaphthalenesulfonic acid, hydroxynaphthalene, hydroxynaphthalenesulfonic acid, anthracene chloride, dichloroanthracene, aminoanthracene, aminoanthracenesulfonic acid, anthracene. Examples thereof include carboxylic acid, hydroxyanthracene, hydroxymethylanthracene and the like. Among these, naphthalene chloride, aminonaphthalene, aminonaphthalenesulfonic acid, hydroxynaphthalene, hydroxynaphthalenesulfonic acid, anthracene chloride, dichloroanthracene, aminoanthracene, aminoanthracenesulfonic acid, anthracenecarboxylic acid, hydroxyanthracene, hydroxymethylanthracene From the viewpoint of easy availability, hydroxynaphthalene, hydroxyanthracene, and hydroxymethylanthracene are particularly preferable.

As a preferable combination of the polymer used in the polymer reaction or the copolymer and a compound having a polycyclic structure, a reaction product of chloromethylstyrene-styrenesulfonic acid copolymer and hydroxymethylanthracene is an active material. It is preferable from the viewpoint that the adsorptivity to the surface, particularly the graphite basal surface, is high and the elution into the electrolyte is small.
Among the compounds exemplified above, 1) naphthalenesulfonic acid formalin condensate and its sodium salt and lithium salt; 2) vinylbenzocyclobutene-styrenesulfonic acid copolymer and its sodium salt and lithium salt; 3) chloro Methylstyrene-sulfonic acid copolymer reacted with hydroxyanthracene, and its sodium and lithium salts are excellent in selective adsorptivity to the graphite basal surface, have low conductivity, and can suppress side reactions of the electrolyte. Further, elution into the electrolytic solution is more preferable because it is particularly small.

Alternatively, it can be prepared by introducing an ionic group into a polymer having a polycyclic structure, or mixing a polymer having an ionic group paired with a polycyclic structure into a polymer having an ionic group. Is possible.
The weight average molecular weight of the polymer (B) is not particularly limited, but is usually 500 or more, preferably 1000 or more, more preferably 1500 or more, still more preferably 2000 or more, and particularly preferably 2500 or more. On the other hand, the weight average molecular weight is usually 1,000,000 or less, preferably 500,000 or less, more preferably 300,000 or less, further preferably 100,000 or less, particularly preferably 50,000 or less, and most preferably 10,000 or less.

The number average molecular weight of the polymer (B) is not particularly limited, but is usually 250 or more, preferably 500 or more, more preferably 750 or more, and further preferably 1250 or more. On the other hand, the weight average molecular weight is usually 500,000 or less, preferably 250,000 or less, more preferably 150,000 or less, still more preferably 100,000 or less, and particularly preferably 25,000 or less.
In the present specification, the weight average molecular weight is the weight average molecular weight in terms of standard polystyrene measured by gel permeation chromatography (GPC) of the solvent tetrahydrofuran (THF), or the solvent is aqueous, dimethylformamide (DMF) or dimethyl sulfoxide. It is a weight average molecular weight in terms of standard polyethylene glycol measured by GPC of (DMSO).

In this specification, the number average molecular weight is the same.
The compound contained in the polymer (B) and capable of eluting into the electrolytic solution is preferably reduced as much as possible because it induces a side reaction. The purity of the polymer (B) is usually 70% or more, preferably Is 80% or more, more preferably 85% or more, and still more preferably 90% or more.
The purity of the polymer (B) can be calculated from the peak area intensity of liquid chromatography and the like.
The compound that can be eluted in the electrolyte solution contained in the polymer (B) is included in the monomer, dimer, trimer, and monomer component of the monomer used when the polymer (B) is synthesized. Impurities and by-products generated during synthesis.
As the polymer (B) described above, a commercially available one may be used, or it can be synthesized by a known method. In the present invention, the polymer (B) can be used alone or in combination of two or more compounds.

<Polymer (C)>
Further, in the active material for a non-aqueous secondary battery negative electrode of the present invention, as other polymer (referred to as polymer (C)) that may be included in addition to the active material (A) and polymer (B), Although not particularly limited as long as the effects of the present invention are not impaired, specific examples include polyethylene glycol, polyallylamine, polyethyleneimine, polyvinylamine, polydiallylamine, polysaccharides, oligosaccharides, polyamino acids, polyvinyl alcohol, and naphthalene sulfone. Acid formalin condensate, sodium polyanisole sulfonate, polyaniline sulfonic acid, polybenzyl methacrylate, polyacrylonitrile, polyvinylidene fluoride, polysulfone, polycarbonate, polyacrylic acid, polymethacrylic acid, polyacrylamide, polyvinyl sulfonic acid, silicone resin, etc. Gerare, these combined two or more, the mixture may be a reaction product.
The weight average molecular weight of the polymer (C) is not particularly limited, but is usually 200 or more, preferably 1000 or more, more preferably 2000 or more, and further preferably 2500 or more. On the other hand, the weight average molecular weight is usually 1,000,000 or less, preferably 500,000 or less, more preferably 300,000 or less, and still more preferably 200,000 or less.

<Method for producing active material for negative electrode of non-aqueous secondary battery>
The active material for a non-aqueous secondary battery negative electrode according to the present invention can be produced, for example, by the following (Method 1) to (Method 4). The method is not limited.

(Method 1)
The polymer (B) is added to a solvent, and the solution (hereinafter sometimes referred to as a polymer (B) solution) is mixed with (or mixed with) the active material (A), and then heated, decompressed, By drying under a nitrogen stream or an atmospheric stream, a non-aqueous secondary battery negative electrode active material containing the active material (A) and the polymer (B) can be obtained.

(Method 2)
In addition, when preparing a slurry in which the active material (A) is dispersed, a solution of the polymer (B) is added to thereby prepare a negative electrode for a non-aqueous secondary battery containing the active material (A) and the polymer (B). An active material can be obtained. In this method, after applying an active material for a non-aqueous secondary battery negative electrode to the negative electrode plate, the initial charge / discharge efficiency can be improved and the gas generation suppression effect can be obtained by drying the solvent of the polymer (B). There is an advantage that can be simplified.
The slurry in which the active material (A) is dispersed is applied to the electrode surface for the negative electrode according to the present invention in order to produce a negative electrode for the non-aqueous secondary battery. It is one of the aspects used in the process.

(Method 3)
Moreover, from the point which can coat | cover the active material (A) surface uniformly, after mixing the solution of a polymer (B) and an active material (A), you may make it dry after filtering the liquid mixture.
A non-adsorbed component can be removed by adding a washing step after filtration.
In addition, when the polymer (C) is mixed, after the polymer (B) solution and the active material (A) are mixed, the polymer (C) is mixed without filtering or drying the mixed solution. Alternatively, after the polymer (B) solution and the active material (A) are mixed, the mixed solution may be filtered or dried, and then the polymer (C) may be mixed.
The solvent used in the above (Method 1) to (Method 3) is not particularly limited as long as the polymer (B) is dissolved, but preferably water, ethyl methyl ketone, toluene, acetone, methyl isobutyl ketone, ethanol. , Methanol and the like. Among these, water, ethyl methyl ketone, acetone, methyl isobutyl ketone, ethanol, and methanol are more preferable because of cost and ease of drying.

  The concentration of the polymer (B) and the polymer (C) in the solvent when mixed with the active material (A) is usually 0.01% by mass or more, preferably 0.03% by mass or more with respect to the solvent. More preferably 0.05% by mass or more, and usually 70% by mass or less, preferably 60% by mass or less, more preferably 40% by mass or less. Within this range, it can be expected that the polymer (B) and the polymer (C) are uniformly present on the surface of the active material (A) in the non-aqueous secondary battery negative electrode active material, which is effective. Is obtained.

  However, the concentration of the polymer (B) and other components in the solvent is the concentration of the solution in contact with the active material (A), and the polymer (B) solution and the polymer (C) When mixing these solutions with the active material (A), or when mixing these solutions with the active material (A), the concentration of the polymer (B) and the polymer (C) is the total concentration. When the active material (A) is mixed with either the polymer (B) solution or the polymer (C) solution and the other solution is added, the polymer (B) solution, polymer (C ) Of each solution.

Moreover, the addition amount of the polymer (B) and other components can be adjusted as appropriate, and the addition amount is adjusted so as to be a preferable content in the above-described active material for a non-aqueous secondary battery negative electrode of the present invention. It is preferable.
When drying the polymer (B) and / or polymer (C) solution by heating, the temperature is usually 50 ° C. or higher, preferably 100 ° C. or higher, usually 300 ° C. or lower, preferably 250 ° C. Within this range, drying efficiency is sufficient, battery performance deterioration due to residual solvent is avoided, polymer (B) and polymer (C) are prevented from being decomposed, and active material (A) and polymer It is possible to easily prevent the effect from being reduced by the weak interaction with (B) and the polymer (C).

When the polymer (B) and / or polymer (C) solution is dried under reduced pressure, the pressure is usually 0 MPa or less and −0.03 MPa or less, usually −0.2 MPa or more, preferably in gauge pressure notation. Is -0.15 MPa or more. If it is this range, it can dry comparatively efficiently.
Prior to drying, the solution containing the active material (A), the polymer (B) and the polymer (C) may be filtered. Thereby, the removal effect of the polymer (B) and the polymer (C) not attached to the active material (A) can be expected.

(Method 4)
Further, with respect to the “material in which the active material (A) and the polymer (B) are combined (hereinafter referred to as polymer composite material)” obtained by (Method 1) and / or (Method 3), You may mix an active material (A) (henceforth a polymer uncoated material). At this time, the polymer uncoated material may be the same material as the active material (A) contained in the polymer composite, or may be another material.

When a polymer uncoated material is mixed with a polymer composite material, the mixing ratio of the polymer uncoated material to the total amount of the polymer composite material and the polymer uncoated material is not particularly limited, but is usually 10% by mass. Or more, preferably 20% by mass or more, more preferably 30% by mass or more, and usually 90% by mass or less, preferably 80% by mass or less, more preferably 70% by mass or less, still more preferably 60% by mass or less, particularly preferably. Is in the range of 50% by weight or less. When the mixing ratio of the polymer uncoated material is less than the above range, the mixed effect tends to hardly appear. On the other hand, when it exceeds the above range, the characteristics of the polymer composite material tend to hardly appear.

<Non-aqueous secondary battery negative electrode active material>
The active material for a non-aqueous secondary battery negative electrode of the present invention thus obtained is not particularly limited as long as it contains the active material (A) and the polymer (B), but the polymer (B) It is preferable that the active material (A) is effectively adsorbed and firmly coated.

(Elution amount of polymer (B) into slurry)
As one of the indicators of the state in which the active material (A) is coated with the polymer (B), the elution of the polymer (B) into the slurry in which the active material for the negative electrode of the non-aqueous secondary battery of the present invention is dispersed. A measure of the quantity is mentioned.
The following method is mentioned as a method of estimating the elution amount of the polymer (B) into the slurry in which the negative electrode active material for a secondary battery is dispersed.

The elution amount is measured by dispersing 50 g of a non-aqueous secondary battery negative electrode active material in which the polymer (B) is coated and / or attached to the active material (A) in 50 g of water, and stirring for 30 minutes. Filtration and washing with 25 g of water are performed, and the high molecular weight contained in the filtrate is measured and calculated from the following formula.
Elution amount of polymer (B) into slurry (% by mass) = mass of polymer in filtrate / mass of polymer (B) in negative electrode active material × 100

  The amount of elution into the slurry of the polymer (B) in the non-aqueous secondary battery negative electrode active material calculated by the above method is usually 90% by mass or less, preferably 83% by mass or less, more preferably. Is 70% by mass or less, more preferably 50% by mass or less, and particularly preferably 40% by mass or less. Moreover, it is 0.01 mass% or more normally, Preferably it is 0.1 mass% or more, More preferably, it is 1 mass% or more.

If the amount of elution is too small, the surface of the active material cannot be sufficiently coated, so that it is difficult to obtain the effect of improving the initial charge / discharge efficiency and the effect of suppressing gas generation. Since the ratio decreases, the capacity per unit weight may decrease.
In addition, when the non-aqueous secondary battery negative electrode active material of the present invention is produced in the above (Method 2), if too much polymer (B) is added, the amount of polymer (B) eluted into the slurry Since there exists a possibility of exceeding the said range, it is preferable to adjust addition amount.

(Elution amount of polymer (B) into non-aqueous electrolyte)
Moreover, the measurement of the elution amount of the polymer (B) into the non-aqueous electrolyte can be cited as one of the indicators of the state in which the active material (A) is coated with the polymer (B).
When the non-aqueous secondary battery negative electrode active material of the present invention is immersed in a non-aqueous electrolyte solution at 75 ° C. for 3 days, the amount of the polymer (B) dissolved in the non-aqueous electrolyte solution is the entire polymer (B). Usually, it is 30 mass% or less, Preferably it is 20 mass% or less, More preferably, it is 10 mass% or less, More preferably, it is 5 mass% or less. Moreover, it is 0.01 mass% or more normally, Preferably it is 0.1 mass% or more.

The non-aqueous electrolyte used for measuring the elution amount of the polymer (B) in the non-aqueous secondary battery negative electrode active material into the non-aqueous electrolyte is ethylene carbonate / dimethyl carbonate / ethyl methyl carbonate = 3/3. A solvent mixed at a volume ratio of / 4. The method for measuring the elution amount is not particularly limited. For example, after immersing the non-aqueous secondary battery negative electrode active material in a non-aqueous electrolyte at 75 ° C. for 3 days, the non-aqueous secondary battery negative electrode active material is taken out and dried. And measuring the mass of the non-aqueous secondary battery negative electrode active material before and after the immersion treatment. Moreover, the said amount of output can also be measured by measuring the NMR spectrum of the active material for non-aqueous secondary battery negative electrodes before and after the leaching treatment.

If the amount of elution is too small, side reactions may occur in the battery, resulting in an increase in the amount of gas generated, an increase in irreversible capacity, and a decrease in cycle capacity maintenance rate.
The content of the polymer (B) in the nonaqueous secondary battery negative electrode active material of the present invention is usually 0.01% by mass or more, preferably 0.1% by mass or more with respect to the active material (A). In addition, it is usually 10% by mass or less, preferably 5% by mass or less, more preferably 2% by mass or less, still more preferably 1% by mass or less, particularly preferably 0.75% by mass or less, and particularly preferably 0.5% by mass. It is contained in the following proportions.

If the content of the polymer (B) is too small, the active material (A) cannot be effectively coated, and the gas generation suppressing effect may not be sufficiently obtained. If the content is too large, the interface resistance between the active material (A) and the coating layer of the polymer (B) may increase.
The content of the polymer (B) in the non-aqueous secondary battery negative electrode active material is determined by using a production method in which the solution containing the polymer (B) is dried during the production of the non-aqueous secondary battery negative electrode active material. In principle, the amount of polymer (B) added during production can be used.
On the other hand, for example, when a production method in which filtration is performed when removing the solvent is used, the weight loss in the TG-DTA analysis of the obtained active material of the present invention, or the amount of the polymer (B) contained in the filtrate It can be calculated from

(Average particle diameter (d50))
The average particle diameter (d50) of the nonaqueous secondary battery negative electrode active material of the present invention is usually 50 μm or less, preferably 30 μm or less, more preferably 25 μm or less, and 1 μm or more, preferably 4 μm or more. More preferably, it is 10 μm or more. Within this range, it is possible to prevent inconveniences in the process such as striping of the negative electrode forming material when the negative electrode is produced in the production of the negative electrode.
In addition, the measuring method of an average particle diameter (d50) is as having mentioned above. Moreover, the average particle diameter (d50) of the active material for a non-aqueous secondary battery negative electrode of the present invention can be adjusted by changing the average particle diameter (d50) of the active material (A) as the raw material. .

(Surface spacing (d ₀₀₂ ))
The inter-surface spacing (d ₀₀₂ ) of the 002 plane according to the X-ray wide angle diffraction method of the active material for a non-aqueous secondary battery negative electrode is usually 0.337 nm or less, preferably 0.336 nm or less. If the d value is too large, the crystallinity decreases and the discharge capacity tends to decrease. On the other hand, the lower limit of 0.3356 nm is a theoretical value of graphite.
The crystallite size (Lc) of the non-aqueous secondary battery negative electrode active material is usually in the range of 30 nm or more, preferably 50 nm or more, more preferably 100 nm or more. Below this range, the crystallinity decreases and the discharge capacity of the battery tends to decrease.

(Surface functional group amount)
The active material for a non-aqueous secondary battery negative electrode has a surface functional group amount O / C value represented by the following formula (1) of usually 2% or more, preferably 3%, more preferably 4%, while usually 30. % Or less, preferably 20% or less, more preferably 15% or less.

If this surface functional group amount O / C value is too small, it indicates that the polymer is unevenly distributed and the coating is insufficient, and the effect of preventing contact with the electrolyte is poor, and the initial efficiency and cycle characteristics tend to decrease and the gas amount tends to increase. is there. On the other hand, if the surface functional group amount O / C value is too large, it indicates an excessive coating state of the polymer, which causes an increase in resistance and tends to deteriorate the input / output characteristics.
Formula (1)
O / C value (%) = {O atom concentration obtained based on the peak area of the O1s spectrum in the X-ray photoelectron spectroscopy (XPS) analysis / C atom obtained based on the peak area of the C1s spectrum in the XPS analysis Density} × 100
The surface functional group amount O / C value in the present invention can be measured using X-ray photoelectron spectroscopy (XPS) as follows.

  An X-ray photoelectron spectrometer is used as an X-ray photoelectron spectroscopy measurement, the measurement object is placed on a sample stage so that the surface is flat, an aluminum Kα ray is used as an X-ray source, and C1s (280 to 300 eV) is obtained by multiplex measurement. ) And O1s (525-545 eV). The obtained C1s peak top is corrected to be 284.3 eV, the peak areas of the C1s and O1s spectra are obtained, and the device sensitivity coefficient is multiplied to calculate the surface atomic concentrations of C and O, respectively. The obtained O / C atomic concentration ratio O / C (O atom concentration / C atom concentration) is defined as the surface functional group amount O / C value of the sample.

(BET specific surface area (SA))
About the specific surface area measured by the BET method of the active material for nonaqueous secondary battery negative electrodes, it is 0.1 m < ² > / g or more normally, Preferably it is 0.7 m < ² > / g or more, More preferably, it is 1 m < ² > / g or more. Moreover, it is 20 m < ² > / g or less normally, Preferably it is 15 m < ² > / g or less, More preferably, it is 12 m < ² > / g or less, More preferably, it is 11 m < ² > / g or less, Most preferably, it is 8 m < ² > / g or less.
If the specific surface area is too small, the number of sites where lithium ions enter and exit is small, and the high-speed charge / discharge characteristics and output characteristics are inferior. On the other hand, if the specific surface area is too large, the activity of the active material with respect to the electrolyte becomes excessive and the initial irreversible capacity Therefore, there is a tendency that a high capacity battery cannot be manufactured.

(Tap density)
The tap density of the nonaqueous secondary battery negative electrode active material is usually preferably 0.5 g / cm ³ or more, preferably 0.6 g / cm ³ or more, and more preferably 0.7 g / cm ³ or more. Further, usually 1.5 g / cm ³ or less and 1.2 g / cm ³ or less are preferable, and 1.1 g / cm ³ or less is more preferable. If the tap density is too low, the high-speed charge / discharge characteristics are inferior. If the tap density is too high, the cycle characteristics may be deteriorated due to a reduction in the effect of suppressing the conduction path break.
Moreover, the tap density of the nonaqueous secondary battery negative electrode active material usually tends to be the same as or smaller than the tap density of the active material (A).

<Mixing with conductive aid>
The active material for a nonaqueous secondary battery negative electrode of the present invention may contain a conductive additive in order to improve the conductivity of the negative electrode. The conductive auxiliary agent is not particularly limited, and is a fine powder made of carbon black such as acetylene black, ketjen black, furnace black, conductive fibers such as carbon nanofiber, Cu, Ni having an average particle size of 1 μm or less, or an alloy thereof. Etc.
It is preferable that the addition amount of a conductive support agent is 10 mass% or less with respect to the active material for non-aqueous secondary battery negative electrodes of this invention.

[Negative electrode for non-aqueous secondary battery]
The negative electrode for a non-aqueous secondary battery of the present invention comprises a current collector and an active material layer formed on the current collector, and the active material layer is at least the active material for a non-aqueous secondary battery negative electrode of the present invention. It contains. The active material layer preferably further contains a binder.
The binder is not particularly limited, but preferably has an olefinically unsaturated bond in the molecule. Specific examples thereof include styrene-butadiene rubber, styrene / isoprene / styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, and ethylene / propylene / diene copolymer.
By using such a binder having an olefinically unsaturated bond, the swellability of the active material layer with respect to the electrolytic solution can be reduced. Of these, styrene-butadiene rubber is preferred because of its availability.

By using such a binder having an olefinically unsaturated bond in the molecule and the non-aqueous secondary battery negative electrode active material of the present invention in combination, the mechanical strength of the negative electrode plate can be increased. When the mechanical strength of the negative electrode plate is high, deterioration of the negative electrode due to charge / discharge is suppressed, and the cycle life can be extended.
The binder having an olefinically unsaturated bond in the molecule preferably has a large molecular weight and / or a large proportion of unsaturated bonds.

As the molecular weight of the binder, the weight average molecular weight is usually 10,000 or more and 1,000,000 or less. If it is this range, both mechanical strength and flexibility can be controlled to a favorable range. The weight average molecular weight is preferably 50,000 or more, and preferably 300,000 or less.
As the ratio of olefinically unsaturated bonds in the binder molecule, the number of moles of olefinically unsaturated bonds per 1 g of the total binder is usually 2.5 × 10 ⁻⁷ mol or more and 5 × 10 ⁻⁶ mol or less. If it is this range, the intensity | strength improvement effect will be acquired sufficiently and flexibility will also be favorable. The number of moles is preferably 8 × 10 ⁻⁷ or more, and preferably 1 × 10 ⁻⁶ or less.

Moreover, about the binder which has an olefinic unsaturated bond, the unsaturation degree is 15 to 90% normally. The degree of unsaturation is preferably 20% or more, more preferably 40% or more, and preferably 80% or less. In the present specification, the degree of unsaturation represents the ratio (%) of the double bond to the number of repeating units of the polymer.
As the binder, a binder having no olefinically unsaturated bond can also be used. By using a binder having no olefinically unsaturated bond in combination with a binder having an olefinically unsaturated bond in the molecule, an improvement in the coating properties of the active material of the present invention or the negative electrode forming material containing the binder can be expected. .

The mixing ratio of the binder having no olefinic unsaturated bond to the binder having an olefinically unsaturated bond is usually 150% by mass or less, preferably 120% by mass, in order to suppress a decrease in the strength of the active material layer. It is as follows.
Examples of the binder having no olefinically unsaturated bond include thickening polysaccharides such as methylcellulose, carboxymethylcellulose, starch, carrageenan, pullulan, guar gum, xanthan gum, and polyethers such as polyethylene oxide and polypropylene oxide. Vinyl alcohols such as polyvinyl alcohol and polyvinyl butyral; polyacids such as polyacrylic acid and polymethacrylic acid or metal salts of these polymers; fluorine-containing polymers such as polyvinylidene fluoride; alkane polymers such as polyethylene and polypropylene; A copolymer etc. are mentioned.

The negative electrode for a non-aqueous secondary battery according to the present invention is a slurry (negative electrode forming material) in which a non-aqueous secondary battery negative electrode active material of the present invention and a binder or a conductive agent are dispersed in a dispersion medium in some cases. It can be formed by applying to a current collector and drying. As the dispersion medium, an organic solvent such as alcohol or water can be used.
In the preparation of the slurry, the polymer (B) is added to and mixed with the active material (A) together with the binder, etc. to produce the non-aqueous secondary battery negative electrode active material of the present invention and to prepare the negative electrode slurry. However, care should be taken that the polymer (B) not coated and / or impregnated with the active material (A) is not present in the slurry.

The binder is usually used in an amount of 0.1% by mass or more, preferably 0.2% by mass or more, based on the active material for a negative electrode for a nonaqueous secondary battery of the present invention. By setting the ratio of the binder to 0.1% by mass or more with respect to the active material of the present invention, the binding force between the active materials or between the active material and the current collector becomes sufficient, and the active material of the present invention can be obtained from the negative electrode. It is possible to prevent a decrease in battery capacity and deterioration in cycle characteristics due to peeling.

  Moreover, it is preferable that a binder shall be normally 10 mass% or less and 7 mass% or less with respect to the active material for non-aqueous secondary battery negative electrodes of this invention. By reducing the binder ratio to 10% by mass or less with respect to the active material of the present invention, the capacity of the negative electrode is prevented from decreasing, and the lithium ion active material when the non-aqueous secondary battery is a lithium ion battery. Can prevent problems such as hindering the entry and exit.

After mixing these components, defoaming is performed as necessary to obtain a slurry that is a negative electrode forming material.
As said negative electrode collector, the well-known thing conventionally used for this use can be used. For example, copper, copper alloy, stainless steel, nickel, titanium, and carbon can be used.

The shape of the current collector is usually a sheet shape, and it is also preferable to use a surface with irregularities, a net or punching metal.
The density of the active material layer of the present invention when used as a negative electrode for a secondary battery varies depending on the application, but is usually 1.1 g / cm ³ in applications where input / output characteristics such as in-vehicle applications and power tool applications are important. As described above, it is 1.65 g / cm ³ or less. Within this range, it is possible to avoid an increase in contact resistance between particles due to the density being too low, and it is also possible to suppress a decrease in rate characteristics due to the density being too high.

The density is preferably 1.2 g / cm ³ or more, more preferably 1.25 g / cm ³ or more.
On the other hand, the density of the active material layer is usually 1.45 g / cm ³ or more and 1.9 g / cm ³ or less in applications where capacity is important, such as portable devices such as mobile phones and personal computers. If it is this range, the capacity | capacitance fall of the battery per unit volume by a density being too low can be avoided, On the other hand, the fall of the rate characteristic by a density being too high can also be suppressed.
The density is preferably 1.55 g / cm ³ or more, more preferably 1.65 g / cm ³ or more, particularly preferably 1.7 g / cm ³ or more.

<Non-aqueous secondary battery>
The basic configuration of the nonaqueous secondary battery according to the present invention can be the same as, for example, a known lithium ion secondary battery, and usually includes a positive electrode and a negative electrode capable of inserting and extracting lithium ions, and an electrolyte. The negative electrode is a negative electrode for a non-aqueous secondary battery according to the present invention described above.

<Positive electrode>
The positive electrode can include a current collector and an active material layer formed on the current collector. The active material layer preferably contains a binder in addition to the positive electrode active material.
Examples of the positive electrode active material include metal chalcogen compounds that can occlude and release alkali metal cations such as lithium ions during charge and discharge. Of these, metal chalcogen compounds capable of inserting and extracting lithium ions are preferred.

Examples of metal chalcogen compounds include transition metal oxides such as vanadium oxide, molybdenum oxide, manganese oxide, chromium oxide, titanium oxide, and tungsten oxide; vanadium sulfide, molybdenum sulfide, titanium sulfide, CuS, and the like transition metal _sulfides; NIPS 3, phosphorus transition metals such as FEPS ₃ - sulfur _compounds; VSe 2, selenium compounds of transition metals such as _{NbSe 3; Fe 0.25 V 0.75 S} 2, Na 0.1 CrS Composite oxides of transition metals such as ₂ ; composite sulfides of transition metals such as LiCoS ₂ and LiNiS ₂ .

Among them, from the viewpoint of occlusion / release of lithium ions, V ₂ O ₅ , V ₅ O ₁₃ , VO ₂ , Cr ₂ O ₅ , MnO ₂ , TiO ₂ , MoV ₂ O ₈ , LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , TiS ₂ , V ₂ S ₅ , Cr _0.25 V _0.75 S ₂ , Cr _0.5 V _0.5 S _{2 and the} like are preferable, and LiCoO ₂ , LiNiO ₂ , LiMn ₂ O _4, and their transitions A lithium transition metal composite oxide in which a part of the metal is substituted with another metal is particularly preferable.

These positive electrode active materials may be used alone or in combination.
The binder for positive electrodes is not specifically limited, A well-known thing can be selected arbitrarily and can be used. Examples include inorganic compounds such as silicate and water glass, and resins having no unsaturated bond such as Teflon (registered trademark) and polyvinylidene fluoride. Among them, a resin having no unsaturated bond is preferable because it is difficult to decompose during the oxidation reaction.

The weight average molecular weight of the binder can usually be 10,000 or more, and can usually be 3 million or less. The weight average molecular weight is preferably 100,000 or more, and preferably 1,000,000 or less.
The positive electrode active material layer may contain a conductive additive in order to improve the conductivity of the positive electrode. The conductive aid is not particularly limited, and examples thereof include carbon powders such as acetylene black, carbon black, and graphite, various metal fibers, powders, and foils.

  The positive electrode of the present invention is a slurry obtained by dispersing an active material and, optionally, a binder and / or a conductive auxiliary agent in a dispersion medium in the same manner as the above-described negative electrode manufacturing method, and applying this to the surface of the current collector. Can be formed. The current collector for the positive electrode is not particularly limited, and examples thereof include aluminum, nickel, and stainless steel (SUS).

<Electrolyte>
The electrolyte (sometimes referred to as “electrolyte”) is not particularly limited, and a non-aqueous electrolyte obtained by dissolving a lithium salt as an electrolyte in a non-aqueous solvent, or an organic polymer compound or the like is added to the non-aqueous electrolyte. By doing so, a gel-like, rubber-like, or solid sheet-like shape can be mentioned.
The non-aqueous solvent used for the non-aqueous electrolyte is not particularly limited, and a known non-aqueous solvent can be used.
For example, chain carbonates such as diethyl carbonate, dimethyl carbonate and ethyl methyl carbonate; cyclic carbonates such as ethylene carbonate, propylene carbonate and butylene carbonate; chain ethers such as 1,2-dimethoxyethane; tetrahydrofuran, 2-methyl Examples include cyclic ethers such as tetrahydrofuran, sulfolane, and 1,3-dioxolane; chain esters such as methyl formate, methyl acetate, and methyl propionate; and cyclic esters such as γ-butyrolactone and γ-valerolactone.

A non-aqueous solvent may be individual or may use 2 or more types together. In the case of a mixed solvent, a combination of a mixed solvent containing a cyclic carbonate and a chain carbonate is preferable from the balance of conductivity and viscosity, and the cyclic carbonate is preferably ethylene carbonate.
The lithium salt used in the non-aqueous electrolyte is not particularly limited, and a known lithium salt can be used. For example, halides such as LiCl and LiBr; perhalogenates such as LiClO ₄ , LiBrO ₄ and LiClO ₄ ; inorganic lithium salts such as inorganic fluoride salts such as LiPF ₆ , LiBF ₄ and LiAsF ₆ ; LiCF ₃ SO ₃ , Examples include perfluoroalkane sulfonates such as LiC ₄ F ₉ SO ₃ ; fluorine-containing organic lithium salts such as perfluoroalkane sulfonic acid imide salts such as Li trifluoromethanesulfonyl imide ((CF ₃ SO ₂ ) ₂ NLi), and the like. . Of these, LiClO ₄ , LiPF ₆ , and LiBF ₄ are preferable.

A lithium salt may be used independently or may use 2 or more types together. The concentration of the lithium salt in the non-aqueous electrolyte can be in the range of 0.5 mol / L or more and 2.0 mol / L or less.
When the organic polymer compound is included in the non-aqueous electrolyte solution described above and used in the form of a gel, rubber, or solid sheet, specific examples of the organic polymer compound include polyethylene oxide, polypropylene oxide, and the like. Polyether polymer compounds; Cross-linked polymers of polyether polymer compounds; Vinyl alcohol polymer compounds such as polyvinyl alcohol and polyvinyl butyral; Insolubilized vinyl alcohol polymer compounds; Polyepichlorohydrin; Polyphosphazene; Siloxane; vinyl polymer compounds such as polyvinylpyrrolidone, polyvinylidene carbonate, polyacrylonitrile; poly (ω-methoxyoligooxyethylene methacrylate), poly (ω-methoxyoligooxyethylene methacrylate-co-methyl methacrylate) And polymer copolymers such as poly (hexafluoropropylene-vinylidene fluoride).

The non-aqueous electrolyte solution described above may further contain a film forming agent.
Specific examples of the film forming agent include carbonate compounds such as vinylene carbonate, vinylethyl carbonate, and methylphenyl carbonate; alkene sulfides such as ethylene sulfide and propylene sulfide; sultone compounds such as 1,3-propane sultone and 1,4-butane sultone And acid anhydrides such as maleic acid anhydride and succinic acid anhydride; isocyanate compounds such as hexamethylene diisocyanate and 1,3-bis (isocyanatomethyl) cyclohexane;

Further, an overcharge inhibitor such as diphenyl ether or cyclohexylbenzene may be added to the non-aqueous electrolyte.
When using the above-mentioned various additives, the total content of the additives is the total amount of the non-aqueous electrolyte so as not to adversely affect other battery characteristics such as an increase in initial irreversible capacity, low temperature characteristics, and deterioration in rate characteristics. In general, it can be 10% by mass or less, in particular, 8% by mass or less, more preferably 5% by mass or less, and particularly preferably 2% by mass or less.

Further, as the electrolyte, a polymer solid electrolyte which is a conductor of an alkali metal cation such as lithium ion can be used.
Examples of the polymer solid electrolyte include those obtained by dissolving a Li salt in the aforementioned polyether polymer compound, and polymers in which the terminal hydroxyl group of the polyether is substituted with an alkoxide.

<Others>
In order to prevent a short circuit between the electrodes, a porous separator such as a porous membrane or a nonwoven fabric can usually be interposed between the positive electrode and the negative electrode, and the non-aqueous electrolyte is impregnated into the porous separator. It is convenient to use it. As a material for the separator, polyolefin such as polyethylene and polypropylene, polyethersulfone, and the like are used, and polyolefin is preferable.

  The form of the non-aqueous secondary battery is not particularly limited. For example, a cylinder type in which a sheet electrode and a separator are spiraled; a cylinder type having an inside-out structure in which a pellet electrode and a separator are combined; a coin type in which a pellet electrode and a separator are stacked Etc. Further, by storing batteries of these forms in an optional outer case, the battery can be used in an arbitrary shape and size such as a coin shape, a cylindrical shape, and a square shape.

  The procedure for assembling the non-aqueous secondary battery is not particularly limited, and can be assembled by an appropriate procedure according to the structure of the battery. For example, a negative electrode can be placed on an outer case, an electrolyte and a separator can be provided thereon, and a positive electrode can be placed so as to face the negative electrode, and can be caulked together with a gasket and a sealing plate to form a battery.

Next, specific embodiments of the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
(Measurement of average particle diameter (d50))
The average particle size (d50) was determined by suspending 0.01 g of a sample in 10 mL of a 0.2% by weight aqueous solution of polyoxyethylene sorbitan monolaurate, a surfactant, and measuring a laser diffraction / scattering particle size distribution analyzer (product) Name: It is a value measured as a volume-based median diameter in a measuring device after being introduced into LA-920) manufactured by HORIBA and irradiated with an ultrasonic wave of 28 kHz for 1 minute at an output of 60 W.

(Measurement of specific surface area (SA))
The specific surface area (SA) is a value of the relative pressure of nitrogen with respect to atmospheric pressure after pre-drying the sample for 15 minutes at 350 ° C. under nitrogen flow using a surface area meter (Okura Riken's fully automatic surface area measuring device). Was measured by a nitrogen adsorption BET one-point method using a gas flow method, using a nitrogen-helium mixed gas accurately adjusted to be 0.3.

(Measurement of interplanar spacing (d ₀₀₂ ) and crystallite size (Lc))
The interplanar spacing (d ₀₀₂ ) and crystallite size (Lc) were prepared by adding a X-ray standard high-purity silicon powder of about 15% by mass of the total amount to the sample and mixing it. A wide-angle X-ray diffraction curve was measured using a reflection diffractometer method as a radiation source, and the interplanar spacing (d002) and crystallite size (Lc) were determined using the Gakushin method.

(Measurement of weight average molecular weight (Mw))
The weight average molecular weight (Mw) of the polymer was measured under the following conditions using gel permeation chromatography (GPC).
Solvent: water / acetonitrile (70/30 (v / v), 0.1 M Tris-HCl buffer, 0.05 M KCl included)
・ Flow rate: 0.5mL / min
・ Temperature: 40 ℃
Calibration was performed using polyethylene glycol.

In addition, this time, it measured using the following apparatuses, detectors, and columns.
・ Equipment: TOSOH GEL PERMATION CHROMATOGRAPH HLC-8020 manufactured by Tosoh Corporation
・ Column: Tosoh TSK gel Super AWM-H x 3

(Measurement of elution amount of polymer into slurry)
50 g of the negative electrode active material coated and / or attached to the active material (A) is dispersed in 50 g of water, stirred for 30 minutes, filtered, washed with 25 g of water, and contained in the filtrate. The high molecular weight was measured and calculated from the following formula.
Elution amount of polymer into slurry (% by mass) = mass of polymer in filtrate / mass of polymer in active material for negative electrode × 100

(Type of active material (A))
Active material (1): Spherical natural graphite particles (average particle diameter (d50) 17 μm, specific surface area (SA) 5.3 m ² / g, face spacing (d ₀₀₂ ) 0.336 nm, crystallite size (Lc) 100 n
m or more)
Active material (2): Spherical natural graphite (average particle size (d50) 16.4 μm, specific surface area (SA) 6.9 m ² / g, interplanar spacing (d ₀₀₂ ) 0.336 nm, crystallite size (Lc) 100n
m or more)
Active material (3): Amorphous carbon-coated graphite (average particle diameter (d50) 16.7 μm, specific surface area (SA) 4.0 m ² / g) Amorphous carbon-coated graphite is spheroidized natural graphite (Average particle diameter (d
50) 16.3 μm) and petroleum heavy oil were mixed, heat treated in an inert gas at 1100 ° C., and then the fired product was pulverized and classified. From the firing yield, it was confirmed that the obtained amorphous carbon-coated graphite was coated with 2% by mass of amorphous carbon based on spheroidized natural graphite.
Active material (4): Graphite-coated graphite (average particle size (d50) 12.8 μm, specific surface area (SA) 4.3 m ² / g)

The graphite-coated graphite was spheroidized natural graphite (average particle size (d50) 13 μm and petroleum heavy oil mixed at a mass ratio of 100: 20 and then mixed. Isotropic to this compound) And then subjected to de-VM firing by heat treatment in an inert gas at 1000 ° C. Thereafter, the fired body was heated to 3000 ° C. to graphitize. By crushing and pulverizing, graphite-coated graphite in which a part of the surface of the spherical natural graphite particles was coated with a graphite material was obtained.
Active material (5): Artificial graphite graphitized after pulverizing bulk mesophase carbon (average particle size (d50) 18.6 μm, specific surface area (SA) 1.3 m ² / g)

(Type of polymer)
Polymer (1): Naphthalenesulfonic acid formalin condensate sodium salt (Kao-made Demol N: weight average molecular weight 2800)
Polymer (2): Anthracene-introduced styrene-polystyrene sulfonate copolymer Copolymerization of chloromethyl styrene and lithium styrene sulfonate at a molar ratio of 20:80 to produce a chloromethyl styrene-lithium styrene sulfonate copolymer Got. Thereafter, 9-hydroxymethylanthracene was synthesized by introducing a polymer reaction into the chloro part of the chloromethylstyrene unit.
Polymer (3): Vinyl benzocyclobutene-lithium styrene sulfonate copolymer Synthesized by polymerizing vinyl benzocyclobutene and lithium styrene sulfonate in a molar ratio of 20:80.
Polymer (4): lithium polystyrene sulfonate (manufactured by Aldrich: weight average molecular weight 70000)
-Polymer (5): Sodium polyanisole sulfonate (manufactured by Aldrich)
-Polymer (6): Naphthalenesulfonic acid formalin condensate sodium salt (Labelin FC-45 manufactured by Daiichi Kogyo Seiyaku: weight average molecular weight 3200)
・ Polymer (7): Naphthalenesulfonic acid formalin condensate sodium salt obtained by purifying polymer (6) and removing low-molecular compound components to a purity of 90% or more

<Example 1>
(1) Preparation of Active Material A for Negative Electrode 50 g of active material (1) as active material (A) and 0.25 g of polymer (1) as polymer (B) are placed in a flask, and 49.75 g of water is added. And stirred. Water was distilled off by heating to obtain a powdered negative electrode active material A. In addition, the elution amount of the polymer (B) in the slurry was 33% by mass.
Next, a cell was produced according to the following procedure and evaluated.

(1) Slurry preparation After mixing 20 g of the negative electrode active material A prepared above and 20.2 g of a carboxymethyl cellulose aqueous solution (1% by mass), the mixture was kneaded by a kneader (Awatori Netaro, manufactured by Shinky Corporation) (kneading: 2000 rpm, 5 min; defoaming: 2200 rpm, 1 min), 0.5 g of styrene-butadiene rubber (SBR) -aqueous dispersion (40% by mass) are added, and kneading is again performed under the same conditions as above to obtain an active material slurry for negative electrode Was prepared.

(2) Electrode plate preparation A copper foil (thickness: 18 μm) was placed on an auto film applicator manufactured by Tester Sangyo Co., Ltd. and adsorbed by negative pressure. By placing an appropriate amount of the negative electrode active material slurry and sweeping the tester industry film applicator (gap 255 μm) at a speed of 10 mm / sec,
A negative electrode active material slurry was applied.

The copper foil coated with the negative electrode active material slurry was dried in an inert oven (EPEC-75, manufactured by Isuzu Seisakusho Co., Ltd.) (90 ° C., 50 min, nitrogen flow 10 L / min).
After that, the active material layer was compressed by passing the electrode plate through a press machine (3-ton mechanical precision roll press). A portion of the copper foil coated with the negative electrode active material slurry is punched into a punch (φ = 12.5 mm, S
NG, manufactured by Nogami Giken Co., Ltd.), weight measurement, and film thickness measurement by a film thickness meter (IDS-112, manufactured by Mitutoyo Corporation) were performed to calculate the basis weight and electrode plate density.

(3) Laminate cell preparation Using nickel manganese cobalt lithium (LiNi _1/3 Mn _1/3 Co _1/3 O ₂ ) as a positive electrode active material, a conductive agent, and polyvinylidene fluoride (PVdF) as a binder Were mixed to form a slurry. The obtained slurry was applied to an aluminum foil having a thickness of 15 μm, dried, and rolled with a press, and the positive electrode active material layer had a width of 30 mm, a length of 40 mm, and an uncoated portion for current collection. A positive electrode was cut out into a shape. The density of the positive electrode active material layer was 2.6 g / cm ³ .

For the negative electrode, the electrode sheet produced by the method described above was cut out into a shape having a width of 32 mm as a size of the negative electrode active material layer, a length of 42 mm, and an uncoated portion as a current collector tab welded portion. The density of the negative electrode active material layer at this time was 1.6 g / cm ³ .
The positive electrode and the negative electrode were arranged so that the active material surfaces face each other, and a porous polyethylene sheet separator was sandwiched between the electrodes. At this time, the positive electrode active material surface was faced so as not to deviate from the negative electrode active material surface.

  A laminate sheet (total thickness) obtained by laminating a polypropylene film, an aluminum foil having a thickness of 0.04 mm, and a nylon film in this order by welding current collecting tabs to uncoated portions of each of the positive electrode and the negative electrode. 0.1 mm) was used to sandwich the polypropylene film on the inner surface side, and the region without electrodes was heat sealed except for one side for injecting the electrolyte solution.

Thereafter, the non-aqueous electrolyte solution (ethylene carbonate (EC) / dimethyl carbonate (DMC) / ethyl methyl carbonate (EMC) = 3/3/4 (volume ratio)) was added to the active material layer at a concentration of 1.0 mol / L. ₆ μL of lithium phosphate (LiPF ₆ ) dissolved per 1 mAh with respect to the rated capacity was injected, sufficiently infiltrated into the electrode, and sealed to prepare a laminate cell.

(4) Conditioning of laminate cell and measurement of gas amount In a 25 ° C. environment, initial conditioning was performed under the following conditions.
1 cycle: Charged for 1 hour at 0.2C, then discharged to 3V at 0.2C. 2cycles: Charged to 4.1V at 0.2C, then discharged to 3V at 0.2C. 3 cycles: 4.2Vcccc at 0.5C. After charging (current amount 0.05C cut condition), 0.
Discharge to 3V at 2C 4 cycles: 4.2V cccv charge at 0.5C (current amount 0.05C cut condition)
(The value of the current that discharges the rated capacity at an hourly discharge capacity in one hour is 1 C. “cc
“cv charge” means that a certain amount of charge is charged at a constant current and then charged until a termination condition is reached at a constant voltage.)
Volume measurement was performed before and after charging the laminate cell, and the amount of change was defined as the amount of gas generated. For measuring the volume of the laminate cell, the Archimedes method was used with ethanol as the immersion liquid.

(5) Resistance measurement The negative electrode resistance was measured as follows.
Impedance measurement was performed using a laminate cell subjected to a charge / discharge test using the following charge / discharge program. A Cole-Cole plot was prepared from the measurement results, and the diameter of the arc including the positive electrode and negative electrode appearing in the plot was read to obtain the interface resistance value.

<Example 2>
50 g of active material (1) as active material (A) and 0.5 g of polymer (1) as polymer (B) were placed in a flask, and 49.5 g of water was added and stirred. Water was distilled off by heating to obtain a powdered negative electrode active material B. The obtained negative electrode active material B was evaluated in the same manner as in Example 1. In addition, the elution amount of the polymer (B) in the slurry was 64% by mass.

<Example 3>
50 g of active material (1) as active material (A) and 0.5 g of polymer (2) as polymer (B) were placed in a flask, and 49.5 g of water was added and stirred. Water was distilled off by heating to obtain a powdery negative electrode active material C. The obtained negative electrode active material C was evaluated in the same manner as in Example 1.

<Example 4>
50 g of active material (1) as active material (A) and 0.25 g of polymer (3) as polymer (B) were placed in a flask, and 49.75 g of water was added and stirred. Water was distilled off by heating to obtain a powdered negative electrode active material D. The obtained negative electrode active material D was evaluated in the same manner as in Example 1.

<Example 5>
50 g of active material (1) as active material (A) and 1.0 g of polymer (1) as polymer (B) were placed in a flask, and 49.0 g of water was added and stirred. Water was distilled off by heating to obtain a powdered negative electrode active material E. The obtained negative electrode active material E was evaluated in the same manner as in Example 1. In addition, the elution amount of the polymer (B) in the slurry was 80% by mass.

<Example 6>
When the active material (A) is not coated with the polymer (B) and the negative electrode active material slurry is prepared, 20 g of the active material (1), 20 g of carboxymethylcellulose aqueous solution (1% by mass), and the polymer (B) 0.1 g of polymer (1) was mixed and kneaded with a kneader (Awatori Kentaro, manufactured by Shinky Co., Ltd.) at 2000 rpm for 5 minutes, and then degassed at 2200 rpm for 1 minute. Then, 0.5 g of SBR aqueous dispersion (40% by mass) was added, and kneading was again performed under the same conditions as above to obtain a slurry of the negative electrode active material F. Preparation and evaluation of the electrode plate as in Example 1 Went.

<Example 7>
50 g of active material (2) as active material (A) and 0.25 g of polymer (6) as polymer (B) were placed in a flask, and 49.75 g of water was added and stirred. Water was distilled off by heating to obtain a powdered negative electrode active material G. The obtained negative electrode active material G was evaluated in the same manner as in Example 1.

<Example 8>
50 g of active material (3) as active material (A) and 0.25 g of polymer (6) as polymer (B) were placed in a flask, and 49.75 g of water was added and stirred. Water was distilled off by heating to obtain a powdered negative electrode active material H. The obtained negative electrode active material H was evaluated in the same manner as in Example 1.

<Example 9>
50 g of active material (4) as active material (A) and 0.25 g of polymer (6) as polymer (B) were placed in a flask, and 49.75 g of water was added and stirred. Water was distilled off by heating to obtain a powdery negative electrode active material I. The obtained negative electrode active material I was evaluated in the same manner as in Example 1.

<Example 10>
50 g of active material (1) as active material (A) and 0.25 g of polymer (7) as polymer (B) were placed in a flask, and 49.75 g of water was added and stirred. Water was distilled off by heating to obtain a powdery negative electrode active material J. The obtained negative electrode active material J was evaluated in the same manner as in Example 1.

<Example 11>
50 g of active material (5) as active material (A) and 0.25 g of polymer (1) as polymer (B) were placed in a flask, and 49.75 g of water was added and stirred. Water was distilled off by heating to obtain a powdered negative electrode active material K. In addition, the elution amount of the polymer (B) into the slurry was 85% by mass.

<Comparative Example 1>
Evaluation was performed in the same manner as in Example 1 except that the active material (1) containing no polymer (B) was used as the negative electrode active material L.

<Comparative example 2>
As an active material (A), 50 g of active material (1) and 1.25 g of a 20% aqueous solution of polymer (4) were placed in a flask, and 48.75 g of water was added and stirred. Water was distilled off by heating, and a powdered negative electrode active material M was obtained. The obtained negative electrode active material M was evaluated in the same manner as in Example 1. The amount of polymer eluted into the slurry was 62% by mass.

<Comparative Example 3>
As an active material (A), 50 g of active material (1) and 2.50 g of a 20% aqueous solution of polymer (4) were placed in a flask, and 47.50 g of water was added and stirred. Water was distilled off by heating to obtain a powdered negative electrode active material N. The obtained negative electrode active material N was evaluated in the same manner as in Example 1.

<Comparative Example 4>
As an active material (A), 50 g of active material (1) and 0.25 g of polymer (5) were placed in a flask, and 49.75 g of water was added and stirred. Water was distilled off by heating to obtain a powdery negative electrode active material O. The obtained negative electrode active material O was evaluated in the same manner as in Example 1.

<Comparative Example 5>
Evaluation was carried out in the same manner as in Example 1 except that the active material (2) containing no polymer (B) was used as the negative electrode active material P.

<Comparative Example 6>
Evaluation was carried out in the same manner as in Example 1 except that the active material (3) not containing the polymer (B) was used as the negative electrode active material Q.

<Comparative Example 7>
Evaluation was carried out in the same manner as in Example 1 except that the active material (4) containing no polymer (B) was used as the negative electrode active material R.

  The above evaluation results are shown in Table 1 below.

The non-aqueous secondary battery negative electrode active materials (Examples 1 to 10) containing the active material (A) and the polymer (B) are the same as the non-aqueous secondary battery negative electrode active materials of Comparative Examples 1 and 5-7. In comparison, it was found that the amount of gas generated was greatly reduced. In addition, the active material containing a polymer having a polycyclic structure is equal to the active material containing a polymer not having a polycyclic structure (Comparative Examples 2, 3, 4), It became clear that resistance did not rise easily. This is because the polycyclic structure is selectively and more strongly adsorbed and / or bonded to the basal surface of the graphite surface. This is thought to be due to restraining the rise.

When the non-aqueous secondary battery negative electrode active material according to the present invention is used as a non-aqueous secondary battery negative electrode active material in a non-aqueous secondary battery, the increase in resistance can be suppressed while suppressing the generation of gas. It has been found that a negative electrode material for a non-aqueous secondary battery with a good balance can be obtained.
Therefore, the non-aqueous secondary battery negative electrode active material according to the present invention is useful for non-aqueous secondary batteries such as in-vehicle applications and power tool applications that emphasize input / output characteristics, and at the same time, It is also useful for non-aqueous secondary batteries for portable devices such as personal computers.

Claims (11)

  A non-aqueous secondary battery negative electrode active material comprising an active material (A) capable of inserting / extracting lithium ions and a polymer (B) having a polycyclic structure.   The non-aqueous secondary battery negative electrode active material according to claim 1, wherein the polymer (B) has an ionic group.   The non-aqueous secondary battery negative electrode active material according to claim 1, wherein the polycyclic structure has a π-conjugated structure.   The polycyclic structure is at least one selected from the group consisting of a polycyclic hydrocarbon group, a polycyclic heterocyclic group, a polycyclic aromatic ring group, and a polycyclic aromatic heterocyclic group. The active material for a nonaqueous secondary battery negative electrode according to any one of claims 1 to 3.   Content of the said polymer (B) is 0.01 mass% or more and 10 mass% or less with respect to the said active material (A), It is any one of Claims 1-4 characterized by the above-mentioned. Active material for negative electrode of non-aqueous secondary battery.   The active material (A) is at least one selected from the group consisting of artificial graphite, natural graphite, amorphous carbon, silicon, silicon oxide, and a material obtained by coating them with a carbonaceous material. Item 6. The non-aqueous secondary battery negative electrode active material according to any one of Items 1 to 5.   The active material (A) is at least one selected from the group consisting of natural graphite, artificial graphite obtained by graphitizing bulk mesophase, and a material obtained by coating them with a carbonaceous material. The active material for nonaqueous secondary battery negative electrodes as described in any one of Claims.   The active material for a nonaqueous secondary battery negative electrode according to any one of claims 1 to 7, wherein the active material (A) is a carbon material, and a crystallite size (Lc) is 100 nm or more. . The non-aqueous secondary battery negative electrode according to any one of claims 1 to 8, wherein an elution amount of the polymer (B) into the slurry calculated by the following measurement method is 90% by mass or less. Active material.
(Measurement method of elution amount of polymer (B) into slurry)
50 g of the non-aqueous secondary battery negative electrode active material in which the polymer (B) is coated and / or attached to the active material (A) is dispersed in 50 g of water, stirred for 30 minutes, filtered, and washed with 25 g of water. The high molecular weight contained in the filtrate is measured and calculated from the following formula.
Elution amount (mass%) of polymer (B) into slurry = mass of polymer (B) in filtrate / mass of polymer (B) in negative electrode active material × 100   It forms using the active material for non-aqueous secondary battery negative electrodes as described in any one of Claims 1-9, The negative electrode for non-aqueous secondary batteries characterized by the above-mentioned.   A nonaqueous secondary battery comprising a positive electrode and a negative electrode capable of inserting and extracting lithium ions, and an electrolyte, wherein the negative electrode is a negative electrode for a nonaqueous secondary battery according to claim 10. Water-based secondary battery.