JP2014139912A - Active material for nonaqueous secondary battery negative electrode, negative electrode and nonaqueous secondary battery using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an active material for a nonaqueous secondary battery negative electrode which is useful for manufacturing a nonaqueous secondary battery assuring small gas generation amount due to decomposition of a nonaqueous electrolyte, excellent in initial charge/discharge efficiency, and excellent in stability in a charge/discharge cycle.SOLUTION: The active material for a nonaqueous secondary battery negative electrode includes an active material (A) capable of inserting and desorbing lithium ion and an organic compound (B). The organic compound (B) has an ionic group and an aromatic ring.

Description

  The present invention is a non-aqueous secondary battery negative electrode active material useful for the production of a non-aqueous secondary battery that is excellent in initial charge and discharge efficiency and excellent in stability in charge and discharge cycles with little gas generation due to decomposition of the non-aqueous electrolyte About. 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. Note that the document has 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.

JP-A-11-129992 JP 2002-117851 A JP 2007-95494 A JP 2002-134171 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.

  The present invention has been made in view of such background art, and in a non-aqueous secondary battery, the initial charge / discharge efficiency can be further improved while suppressing gas generation due to decomposition of the non-aqueous electrolyte, and the charge / discharge cycle. It is an object of the present invention to provide a non-aqueous secondary battery negative electrode active material in which the capacity loss accompanying the reduction is reduced.

  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 an organic compound. In the active material for a negative electrode of a non-aqueous secondary battery containing (B), by applying a compound different from the conventional one as the organic compound (B), the initial charge / discharge efficiency, the gas generation suppression effect can be improved, and the cycle The inventors have found that a non-aqueous secondary battery having excellent characteristics can be obtained, and have completed the present invention.

  Specifically, the organic compound (B) in the present invention is a compound that satisfies at least two conditions, that is, having an ionic group and having an aromatic ring.

  The details of the non-aqueous secondary battery negative electrode active material according to the present invention containing the organic compound (B) exhibiting the above effect are unclear. However, as a result of the study by the inventors, excellent battery characteristics are as follows. This is considered to be due to such an effect.

  That is, when the organic compound (B) having the above-described characteristics and the active material (A) are contained in the active material layer for a non-aqueous secondary battery negative electrode, the aromatic ring of the organic compound (B) becomes the active material ( It acts specifically on the surface of A) and has an effect of suppressing the activity of the surface of the active material (A). Furthermore, the aromatic ring can impart high adsorptivity between the active material (A) surface and the organic compound (B).

  Further, since the organic compound (B) has an ionic group, the organic compound (B) adsorbed on the active material (A) can be prevented from swelling in the non-aqueous electrolyte solution, and the active material ( A) It is considered that high adsorptivity can be imparted between the surface and the organic compound (B).

That is, the gist of the present invention is as follows.
<1> An active material for a non-aqueous secondary battery negative electrode containing an active material (A) capable of inserting / extracting lithium ions and an organic compound (B),
A nonaqueous secondary battery negative electrode active material, wherein the organic compound (B) has an ionic group and an aromatic ring.

<2> The elution amount of the organic compound (B) into the non-aqueous electrolyte when immersed in a non-aqueous electrolyte at 75 ° C. for 3 days is 30% by mass or less of the whole organic compound (B). The nonaqueous secondary battery negative electrode active material according to <1>.
<3> The nonaqueous secondary battery negative electrode according to <1> or <2>, wherein the organic compound (B) is contained in an amount of 0.1 to 5 parts by mass with respect to 100 parts by mass of the active material (A). Active material.
<4> The nonaqueous secondary battery negative electrode active material according to any one of <1> to <3>, wherein the active material (A) is spheroidized natural graphite.
<5> The ionic group of the organic compound (B) is at least one ionic group selected from the group consisting of a carboxylic acid group, a sulfonic acid group, a phosphoric acid group, a phosphonic acid group, and salts thereof. The active material for a nonaqueous secondary battery negative electrode according to any one of <1> to <4>.

<6> The organic compound (B) includes a structural unit derived from a monomer having a carboxylic acid group or a sulfonic acid group or a salt thereof and a structural unit derived from a monomer having an aromatic ring, and the organic compound (B ) Is a non-aqueous secondary battery negative electrode active material according to any one of <1> to <5>, wherein the weight average molecular weight is 500 to 1,000,000.
<7> The organic compound (B) is polystyrene sulfonic acid, polystyrene sulfonate lithium, sodium polystyrene sulfonate, styrene-styrene sulfonate copolymer, styrene-lithium sulfonate lithium copolymer, styrene-sodium styrene sulfonate. Copolymer, polyvinyl benzoic acid, lithium polyvinyl benzoate, sodium polyvinyl benzoate, styrene-vinyl benzoic acid copolymer, styrene-lithium vinyl benzoate copolymer, styrene-sodium vinyl benzoate copolymer, naphthalene sulfonic acid The active material for a nonaqueous secondary battery negative electrode according to any one of <1> to <6>, wherein the active material is at least one compound selected from the group consisting of lithium and sodium naphthalenesulfonate.
<8> The electrical conductivity of the organic compound (B) is usually greater than 0 S / cm and not greater than 0.1 S / cm at 25 ° C., according to any one of <1> to <7> above. Active material for non-aqueous secondary battery negative electrode.

Another aspect of the present invention is <9> for a non-aqueous secondary battery formed using the active material for a non-aqueous secondary battery negative electrode according to any one of <1> to <8>. It is a negative electrode.
Another gist of the present invention is a nonaqueous secondary battery comprising <10> a positive electrode and a negative electrode capable of inserting and extracting lithium ions, and an electrolyte, wherein the negative electrode is a non-aqueous secondary battery according to <9>. It is a non-aqueous secondary battery that is a negative electrode for an aqueous secondary battery.
Moreover, the other summary of this invention is the non-aqueous secondary battery as described in said <10> in which the <11> above-mentioned electrolyte contains an isocyanate compound.

  According to the present invention, an excellent non-aqueous secondary battery useful for the production of a non-aqueous secondary battery that generates less gas due to decomposition of a non-aqueous electrolyte solution, has excellent initial charge / discharge efficiency, and has excellent stability in a charge / discharge cycle. An active material for a battery negative electrode can be provided. In addition, a non-aqueous secondary battery negative electrode using the non-aqueous secondary battery negative electrode active material and a non-aqueous secondary battery including the 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.
Here, when “ppm” is simply described in the present specification, it means “ppm by mass”.

[Non-aqueous secondary battery negative electrode active material]
<Active material (A)>
The active material for a negative electrode of a non-aqueous secondary battery of the present invention (hereinafter also simply referred to as “the active material of the present invention”) contains an active material (A) capable of inserting / extracting lithium ions. The active material (A) is not particularly limited as long as it is a material capable of inserting and extracting 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 later, among these, at least one selected from the group consisting of artificial graphite, natural graphite, amorphous carbon, silicon, and silicon oxide is a balance of lithium storage capacity, cycle characteristics, and cost. To preferred. Further, a carbonaceous material such as amorphous carbon or graphitized material may be used.

  In this invention, these can be used individually or in combination of 2 or more types. In addition, the above 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, and amorphous particles, but is preferably spherical.
Examples of the carbon material include artificial graphite, natural graphite, amorphous carbon, and a carbonaceous material having a low degree of graphitization. From the viewpoint of low cost and ease of electrode production, artificial graphite or natural graphite is used. Is preferable, and natural graphite 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., and the main production area of the soil graphite is the Korean Peninsula, China, 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.

Examples of the artificial graphite include coal tar pitch, coal heavy oil, atmospheric residue, petroleum heavy oil, aromatic hydrocarbon, nitrogen-containing cyclic compound, sulfur-containing cyclic compound, polyphenylene, polyvinyl chloride, Examples thereof include those obtained by baking and graphitizing organic substances such as polyvinyl alcohol, polyacrylonitrile, polyvinyl butyral, natural polymer, polyphenylene sulfide, polyphenylene oxide, furfuryl alcohol resin, phenol-formaldehyde resin, and imide resin.
The firing temperature can be in the range of 2500 ° C. to 3200 ° C., and a silicon-containing compound, a boron-containing compound, or the like can be used as a graphitization catalyst during firing.

  Examples of the amorphous carbon include particles obtained by firing a bulk mesophase and particles obtained by infusibilizing and firing a carbon precursor.

  Examples of the carbonaceous material having a small degree of graphitization include those obtained by firing an organic material at a temperature of 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 in 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 material having a small particle size, a thin film, a porous structure, etc. that can relax volume expansion / contraction during lithium insertion / extraction is preferable. If necessary, it can be combined with a carbon material or other active material. Use.

  As the tin-based material, any of tin, stannous oxide, stannic oxide, and tin amorphous alloy may be used. The tin-based material preferably has a small particle size, thin film, porous structure, etc. that can relieve volume expansion / contraction during lithium insertion / extraction, and various carbon materials and other active material materials as necessary. Used in combination with.

  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 and 50 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.
The average particle diameter (d50) is preferably 4 μm or more, more preferably 10 μm or more, and preferably 30 μm or less, more preferably 25 μm or less.

  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 measured by dropping a sample through a sieve having a mesh size of 300 μm into a cylindrical tap cell having a diameter of 1.6 cm and a volume capacity of 20 cm ³ using a powder density measuring instrument, A tap having a stroke length of 10 mm is performed 1000 times, and the density obtained from the volume after the tap 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 and 11 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.
The BET specific surface area is preferably 1.2 m ² / g or more, more preferably 1.5 m ² / g or more, preferably 10 m ² / g or less, more preferably 9 m ² / g or less, and still more preferably. Is 8 m ² / g or less.
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.

(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.

<Organic compound (B)>
Next, the organic compound (B) which is a component of the active material for a nonaqueous secondary battery negative electrode of the present invention will be described.
The organic compound (B) has an ionic group and an aromatic ring from the viewpoint of effectively suppressing gas generation.
Since the ionic group in the organic compound (B) is hardly soluble in the non-aqueous electrolyte and the aromatic ring has a π-conjugated structure, when the organic compound (B) is used for a negative electrode for a non-aqueous secondary battery. Gas generation can be suppressed.

  Since the ionic group of the organic compound (B) is hardly soluble in the non-aqueous electrolyte, the resistance of the non-aqueous secondary battery negative electrode active material of the present invention to the non-aqueous electrolyte is improved, and the active material (A The organic compound (B) adsorbed on the non-aqueous electrolyte is difficult to elute.

  In the present specification, “slightly soluble in non-aqueous electrolyte” means that the organic compound (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.

  Further, since the aromatic ring of the organic compound (B) has a π-conjugated structure, the π-plane structure portion on the surface of the active material (A) is selectively selected by acting on the π-plane structure portion of the active material (A). Therefore, it is considered possible to effectively suppress the generation of gas and suppress the increase in negative electrode resistance.

  In this specification, the aromatic ring of the organic compound (B) is 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 a planar ring.

  Specific examples of the organic compound (B) having such an aromatic ring include furan, pyrrole, imidazole, thiophene, phosphole, pyrazole, oxazole, isoxazole, and thiazole, which are monocyclic 5-membered rings; Benzene, pyridine, pyrazine, pyrimidine, pyridazine, triazine as member rings; benzofuran, isobenzofuran, indole, isoindole, benzothiophene, benzophosphole, benzimidazole, purine, indazole as bicyclic 5-membered ring + 6-membered ring , Benzoxazole, benzisoxazole, benzothiazole; naphthalene, quinoline, isoquinoline, quinoxaline, quinazoline, cinnoline which are bicyclic 6-membered ring + 6-membered ring; polycyclic anthracene, pyrene and the like.

  Among these, benzene or naphthalene is preferable from the viewpoint of suppressing gas generation when used in a negative electrode for a non-aqueous secondary battery.

The ionic group possessed by the organic compound (B) 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, and salts thereof. Can be mentioned. Examples of the salt include lithium salt, sodium salt, potassium salt and the like.
Among these, a sulfonic acid group or a lithium salt or a sodium salt thereof is preferable from the viewpoint of initial irreversible capacity when used for a negative electrode for a non-aqueous secondary battery.

  As for the organic compound (B), one type of compound may have both an ionic group and an aromatic ring, or a mixture of a compound having an ionic group and a compound having an aromatic ring.

  The organic compound (B) may be a low molecular compound or a high molecular compound (polymer), but is preferably a high molecular compound from the viewpoint of effectively suppressing gas generation. .

Examples of the low molecular weight compound include naphthalene sulfonic acid, lithium naphthalene sulfonate, sodium naphthalene sulfonate, benzene sulfonic acid, sodium benzene sulfonate, aniline sulfonic acid, sodium aniline sulfonate, lithium aniline sulfonate, anthracene sulfonic acid, Anthracene sodium sulfonate is mentioned.
Of these, lithium naphthalene sulfonate or sodium naphthalene sulfonate is preferred because of its high adsorption property to the active material (A).

When the organic compound (B) is a polymer compound, the weight average molecular weight is not particularly limited, but is usually 500 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.
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).

When the organic compound (B) is a polymer compound (polymer), the polymer compound preferably has an ionic group and an aromatic ring.
Examples of the monomer that is a structural unit constituting the polymer include a monomer having an ionic group and a monomer having an aromatic ring. Moreover, the monomer which has both an ionic group and an aromatic ring may be sufficient.

In this case, the polymer may be a copolymer of a monomer having an ionic group and not having an aromatic ring, and a monomer having an aromatic ring and not having an ionic group. And a monomer polymer having both aromatic rings. Further, it may be a mixture of a monomer polymer having an ionic group and a monomer polymer having an aromatic ring.
Among these, from the viewpoint of the stability of the organic compound (B) covering the active material (A) in the non-aqueous secondary battery negative electrode active material in the electrolyte, the organic compound (B) is composed of an ionic group and an aromatic ring. It is preferable that it is a polymer of the monomer which has both.

  The ionic group possessed by the monomer is the same as the ionic group described above, and among them, a carboxylic acid group, a sulfonic acid group or a salt thereof is preferable from the viewpoint of stability in the battery and suppression of resistance increase. . The organic compound (B) obtained by copolymerizing a monomer having an aromatic ring is preferable from the viewpoint of improving the adsorptivity to the surface of the active material (A) (especially the basal surface in graphite).

Examples of monomers having an ionic group and an aromatic ring include styrene sulfonic acid, lithium styrene sulfonate, sodium styrene sulfonate, aniline, aniline sulfonic acid, aniline sulfonic acid salt, vinyl benzoate and vinyl benzoate salt. Etc.
Examples of monomers having an ionic group and no aromatic ring include vinyl sulfonic acid, lithium vinyl sulfonate, sodium vinyl sulfonate, acrylic acid, sodium acrylate, lithium acrylate, methacrylic acid, sodium methacrylate And lithium methacrylate.
Examples of the monomer having an aromatic ring and not having an ionic group include styrene, benzyl acrylate, benzyl methacrylate and the like.

  Specific examples of the polymer containing a structural unit derived from such a monomer include a styrene-vinyl sulfonic acid copolymer, a styrene-vinyl sulfonic acid sodium copolymer, a styrene-vinyl sulfonic acid lithium copolymer, and polystyrene. Sulfonic acid, lithium polystyrene sulfonate, sodium polystyrene sulfonate, polyaniline sulfonic acid, lithium polyaniline sulfonate, sodium polyaniline sulfonate, styrene-styrene sulfonate copolymer, styrene-lithium sulfonate lithium copolymer, styrene-styrene sulfone Acid sodium copolymer, polyvinyl benzoic acid, polyvinyl lithium benzoate, sodium polyvinyl benzoate, styrene-vinyl benzoic acid copolymer, styrene-vinyl lithium benzoate copolymer, Len - Sodium copolymer vinyl benzoate, and the like.

From the viewpoint of effectively suppressing the generation of gas, polystyrene sulfonic acid, polystyrene lithium sulfonate, sodium polystyrene sulfonate, styrene-styrene sulfonic acid copolymer, styrene-lithium sulfonic acid copolymer, styrene-styrene sulfonic acid Sodium copolymers, polyvinyl benzoic acid, lithium polyvinyl benzoate, sodium polyvinyl benzoate, styrene-vinyl benzoic acid copolymers, styrene-vinyl lithium benzoate copolymers and styrene-sodium vinyl vinyl copolymers are preferred.
Furthermore, polystyrene sulfonate, lithium polystyrene sulfonate, sodium polystyrene sulfonate, styrene-styrene sulfonate lithium copolymer and styrene-sodium styrene sulfonate copolymer are more preferable.
Among them, lithium polystyrene sulfonate, sodium polystyrene sulfonate, styrene-lithium sulfonate lithium copolymer, and styrene-sodium styrene sulfonate copolymer are particularly preferable because of their high adsorptivity to the active material surface, particularly the graphite basal surface. .

  The electrical conductivity of the organic compound (B) is not particularly limited, but is usually greater than 0 S / cm at 25 ° C., preferably 0.1 S / cm or less, more preferably 0.01 S / cm or less, and 0.001 S / cm or less. Is more preferable, and is particularly preferably less than 0.0001 S / cm. A low conductivity material having an organic compound (B) electrical conductivity of 0.1 S / cm or less is preferable from the viewpoint of suppressing reductive decomposition of the electrolyte solution on the surface of the organic compound (B). .

The electrical conductivity was measured by, for example, producing a film from the organic compound (B) by a film formation method such as spin coater film formation or drop cast film formation on a glass substrate, and measuring the film thickness and the four-terminal method. It can be calculated from the reciprocal of the value obtained by multiplying the surface resistance value.
The film thickness can be measured with a KLA step, surface roughness and fine shape measuring device, Tencor α step type, and the surface resistance measured by the four-terminal method should be measured with a Loresta GP MCP-T610 type manufactured by Mitsubishi Chemical Analytech. Can do.

  As the organic compound (B) described above, a commercially available one may be used, or it can be synthesized by a known method. In the present invention, the organic compound (B) can be used alone or in combination of two or more compounds, regardless of whether the compound is a low molecular compound or a high molecular compound.

<Other ingredients>
The non-aqueous secondary battery negative electrode active material according to the present invention may contain a conductive agent in order to improve the conductivity of the negative electrode.
The conductive agent is not particularly limited, and carbon black such as acetylene black, ketjen black and furnace black, fine powder made of Cu, Ni or an alloy thereof having an average particle diameter of 1 μm or less can be used.
It is preferable that the addition amount of the said electrically conductive agent is 10 mass% or less with respect to the active material for non-aqueous secondary battery negative electrodes of this invention.

<Method for producing active material for negative electrode of non-aqueous secondary battery>
The active material for a nonaqueous secondary battery negative electrode of the present invention can be obtained by mixing the active material (A) and the organic compound (B) described above. As will be described later, the organic compound (B) may be mixed with the active material (A) when preparing a slurry which is a negative electrode forming material at the time of preparing the negative electrode.

  In order to facilitate mixing of the active material (A) and the organic compound (B), the organic compound (B) is dissolved or dispersed in a solvent to form a solution state, and the active material (A) is added thereto. Thereafter, the organic compound (B) is uniformly mixed with the active material (A), and stirred well so that the organic compound (B) adheres to the surface of the active material (A). And after mixing sufficiently, the active material of this invention can be obtained by removing a solvent by filtration or heating.

Examples of the solvent include water and organic solvents such as ethyl methyl ketone, acetone, methyl isobutyl ketone, ethanol, and methanol. Water is preferable because it is easily available and has little environmental impact.
Moreover, the said heating is about 60-120 degreeC normally. When the active material is dried under reduced pressure after removing the solvent, the temperature is usually 300 ° C. or lower and 50 ° C. or higher. Within this range, the drying efficiency is sufficient, battery performance deterioration due to residual solvent is avoided, the organic compound (B) is prevented from being decomposed, and the active material (A) and the organic compound (B) can be prevented from interacting with each other. It is possible to easily prevent the effect from being reduced due to weak action.
The drying temperature is preferably 250 ° C. or lower, and preferably 100 ° C. or higher.

<Non-aqueous secondary battery negative electrode active material>
In the thus obtained non-aqueous secondary battery negative electrode active material of the present invention, it is considered that the organic compound (B) is effectively adsorbed on the active material (A) and is firmly coated.

When the active material for a non-aqueous secondary battery negative electrode of the present invention is immersed in a non-aqueous electrolyte solution at 75 ° C. for 3 days, the elution amount of the organic compound (B) in the non-aqueous electrolyte solution is the entire organic compound (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 when measuring the elution amount of the organic compound (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 elution amount can also be measured by measuring the NMR spectrum of the non-aqueous secondary battery negative electrode active material before and after the immersion treatment.

  If the elution amount is less than 0.01% by mass, the surface of the active material cannot be sufficiently covered, so that the effect of improving the initial charge / discharge efficiency and the effect of suppressing gas generation tend to be difficult to obtain. If it exceeds, the negative electrode resistance increases and the active material ratio decreases, so the capacity per unit weight may decrease.

  Moreover, the content rate of an organic compound (B) in the non-aqueous secondary battery negative electrode active material of this invention is 0.01 mass part or more normally with respect to 100 mass parts of active materials (A), Preferably it is 0.1 mass. Part or more, usually 10 parts by weight or less, preferably 5 parts by weight or less, more preferably 2 parts by weight or less, still more preferably 1 part by weight or less, particularly preferably 0.75 parts by weight or less, particularly preferably 0.8. It is contained at a ratio of 5 parts by mass or less.

  If the content of the organic compound (B) is too small, it may be difficult to effectively coat the active material (A), while if the content of the organic compound (B) is too large, the active material (A ) And the coating layer of the organic compound (B) may increase.

The content of the organic compound (B) in the non-aqueous secondary battery negative electrode active material is obtained by using a manufacturing method in which a solution containing the organic compound (B) is dried at the time of manufacturing the non-aqueous secondary battery negative electrode active material. In principle, the amount of the organic compound (B) added during production can be used.
On the other hand, for example, in the case of using a production method in which filtration is performed when removing the solvent, the weight loss in the TG-DTA analysis of the obtained active material of the present invention, or the amount of the organic compound (B) contained in the filtrate It can be calculated from

Moreover, the average particle diameter (d50) of the active material for a nonaqueous secondary battery negative electrode of the present invention can be usually 50 μm or less, and can be 1 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.
The average particle diameter (d50) is preferably 30 μm or less, more preferably 25 μm or less, and preferably 4 μm or more, more preferably 10 μm or more. 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. .

[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 preparing the slurry, the organic compound (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. May be performed simultaneously.

  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]
Hereinafter, although the detail of the member regarding the non-aqueous secondary battery which concerns on this invention is illustrated, the material which can be used, the manufacturing method, etc. are not limited to the following specific examples.
The basic configuration of the non-aqueous secondary battery of the present invention can be the same as that of a conventionally known non-aqueous secondary battery. Usually, 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.
Hereinafter, each component of the nonaqueous secondary battery will be described.

<Positive electrode>
The positive electrode is obtained by forming a positive electrode active material layer containing a positive electrode active material and a binder on a current collector.
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; selenium compounds of transition metals such as _{VSe 2, NbSe 3; Fe 0.25} V 0.75 S 2, Na 0.1 Examples include composite oxides of transition metals such as CrS 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 the like are particularly preferable. A lithium transition metal composite oxide in which a part of these transition metals is substituted with another metal.
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 (PVdF). 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 agent in order to improve the conductivity of the positive electrode. The conductive agent 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 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. It can be formed by drying. The current collector of the positive electrode is not particularly limited, and examples thereof include aluminum, nickel, stainless steel (SUS) and the like.

<Electrolyte>
There is no restriction | limiting in the electrolyte used for the non-aqueous electrolyte in the non-aqueous secondary battery of this invention, The well-known thing used as an electrolyte can be employ | adopted arbitrarily and can be contained. In addition, the non-aqueous electrolyte may be made into a gel, rubber, or solid sheet with an organic polymer compound or the like.

The electrolyte is preferably a lithium salt. Specific examples of the electrolyte include LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , lithium bis (oxalato) borate, lithium difluorooxalatoborate. Lithium tetrafluorooxalato phosphate, lithium difluorobis (oxalato) phosphate, lithium fluorosulfonate, and the like.
These electrolytes may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

The concentration of the lithium salt in the non-aqueous electrolyte is arbitrary, but is usually 0.5 mol / L or more, preferably 0.6 mol / L or more, more preferably 0.8 mol / L or more, and usually 3 mol / L or less. , Preferably 2 mol / L or less, more preferably 1.5 mol / L or less.
When the total molar concentration of the lithium salt is within the above range, the electrical conductivity of the non-aqueous electrolyte is sufficient, while preventing the decrease in electrical conductivity and battery performance due to the increase in viscosity due to excess salt. Can do.

<Non-aqueous solvent>
The non-aqueous solvent contained in the non-aqueous electrolyte solution is not particularly limited as long as it does not adversely affect the battery characteristics when used as a battery.
Examples of commonly used non-aqueous solvents include chain compounds such as dimethyl carbonate, ethyl methyl carbonate and diethyl carbonate, and carbonate compounds such as cyclic carbonates such as ethylene carbonate, propylene carbonate and butylene carbonate; methyl acetate, ethyl acetate, Chain carboxylic acid esters such as methyl propionate and ethyl propionate; Cyclic carboxylic acid esters such as γ-butyrolactone; Chain ethers such as dimethoxyethane and diethoxyethane; Cyclic ethers such as tetrahydrofuran, 2-methyltetrahydrofuran and tetrahydropyran Nitriles such as acetonitrile, propionitrile, benzonitrile, butyronitrile and valeronitrile; phosphate esters such as trimethyl phosphate and triethyl phosphate; Emissions sulfite, 1,3-propane sultone, methyl methanesulfonate, sulfolane, sulfur-containing compounds such as dimethyl sulfone and the like.
In these compounds, some of the hydrogen atoms may be substituted with halogen atoms.

  The non-aqueous solvent may be used alone or in combination of two or more, but it is preferable to use in combination of two or more compounds. For example, it is preferable to use a high dielectric constant solvent such as cyclic carbonate or cyclic carboxylic acid ester in combination with a low viscosity solvent such as chain carbonate or chain carboxylic acid ester.

<Auxiliary>
In addition to the above-described electrolyte and non-aqueous solvent, an auxiliary may be appropriately added to the non-aqueous electrolyte depending on the purpose. The auxiliary agent that has the effect of forming a film on the negative electrode surface and improving the life of the battery includes unsaturated cyclic carbonates such as vinylene carbonate, vinyl ethylene carbonate, and ethynyl ethylene carbonate; cyclic carbonates having fluorine atoms such as fluoroethylene carbonate Fluorinated unsaturated cyclic carbonates such as 4-fluorovinylene carbonate; and isocyanate compounds such as a compound represented by the following general formula (1).
Among these, vinylene carbonate or an isocyanate compound represented by the following general formula (1) is preferable from the viewpoint of gas suppression.

In the above formula, A is a hydrogen atom, a halogen atom, a vinyl group, an isocyanate group, a C _{1 to} C ₂₀ monovalent aliphatic hydrocarbon group (which may have a hetero atom) or C _{6 to} C _20. Represents a monovalent aromatic hydrocarbon group (which may have a hetero atom). B represents an oxygen atom, SO ₂ , a C _{1 to} C ₂₀ divalent aliphatic hydrocarbon group (which may have a hetero atom), or a C _{6 to} C ₂₀ divalent aromatic hydrocarbon group ( Which may have a heteroatom).

Examples of the isocyanate compound represented by the general formula (1) include the following compounds.
Diisocyanato sulfone, diisocyanato ether, trifluoromethane isocyanate, pentafluoroethane isocyanate, trifluoromethanesulfonyl isocyanate, pentafluoroethanesulfonyl isocyanate, benzenesulfonyl isocyanate, p-toluenesulfonyl isocyanate, 4-fluorobenzenesulfonyl isocyanate, 1,3 -Diisocyanatopropane, 1,3-diisocyanato-2-fluoropropane, 1,4-diisocyanatobutane, 1,4-diisocyanato-2-butene, 1,4-diisocyanato-2-fluorobutane, 1,4 -Diisocyanato-2,3-difluorobutane, 1,5-diisocyanatopentane, 1,5-diisocyanato-2-pentene, 1,5-diisocyanato-2-meth Pentane, 1,6-diisocyanatohexane, 1,6-diisocyanato-2-hexene, 1,6-diisocyanato-3-hexene, 1,6-diisocyanato-3-fluorohexane, 1,6-diisocyanato-3, 4-difluorohexane, 1,7-diisocyanatoheptane, 1,8-diisocyanatooctane, 1,12-diisocyanatodecane, 1-isocyanatoethylene, isocyanatomethane, 1-isocyanatoethane, 1- Isocyanato-2-methoxyethane, 3-isocyanato-1-propene, isocyanatocyclopropane, 2-isocyanatopropane, 1-isocyanatopropane, 1-isocyanato-3-methoxypropane, 1-isocyanato-3-ethoxypropane, 2-isocyanato-2-methylpropane, 1-isocyana Butane, 2-isocyanatobutane, 1-isocyanato-4-methoxybutane, 1-isocyanato-4-ethoxybutane, methyl isosinatoformate, isanatocyclopentane, 1-isocyanatopentane, 1-isocyanato-5-methoxy Pentane, 1-isocyanato-5-ethoxypentane, 2- (isocyanatomethyl) furan, isocyanatocyclohexane, 1-isocyanatohexane, 1-isocyanato-6-methoxyhexane, 1-isocyanato-6-ethoxyhexane, ethyl isocyanate Natoacetate, isocyanatocyclopentane, isocyanatomethyl (cyclohexane), 1-isocyanatoheptane, ethyl 3-isocyanatopropanoate, isocyanatocyclooctane, 2-isocyanatoethyl-2-methyl acrylate 1-isocyanatooctane, 2-isocyanato-2,4,4-trimethylpentane, butylisocyanatoacetate, ethyl 4-isocyanatobutanoate, 1-isocyanatotonane, 1-isocyanatoadamantane, 1- Isocyanatodecane, ethyl 6-isocyanatohexanoate, 1,3-bis (isocyanatomethyl) cyclohexane, dicyclohexylmethane diisocyanate, 1-isocyanatoundecane, diisocyanatobenzene, toluene diisocyanate, xylene diisocyanate, ethyl diisocyanato Benzene, trimethyldiisocyanatobenzene, diisocyanatonaphthalene, diisocyanatobiphenyl, diphenylmethane diisocyanate, 2,2-bis (isocyanatophenyl) hexafluoropropane Allyl isocyanate, vinyl isocyanate.

  Especially, the diisocyanate compound which has a structure shown by following formula (2) is preferable.

If it is a compound represented by Formula (2), the tolerance with respect to the physical deformation | transformation of the expansion / contraction of an electrode accompanying charging / discharging can be improved effectively. This is because chain-like methylene groups are incorporated into the film and / or electrode structure, thereby imparting appropriate elasticity to the electrode structure.
Therefore, for this purpose, the length of the methylene group is important, and in the formula, x is preferably an integer of 4 to 12, more preferably an integer of 4 to 8.
Specifically, as the compound of the formula (2), 1,4-diisocyanatobutane, 1,5-diisocyanatopentane, 1,6-diisocyanatohexane, 1,7-diisocyanatoheptane, 1, 8-diisocyanatooctane and the like are preferable.

In the present invention, the concentration of the auxiliary agent in the composition of the nonaqueous electrolytic solution is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.01% by mass or more, preferably 0.05% by mass or more, More preferably, it is 0.1 mass% or more, and is 5 mass% or less normally, Preferably it is 3 mass% or less, More preferably, it is the range of 1.5 mass% or less.
If it is the said range, while being able to fully improve the chemical and physical stability in a battery, the excessive increase in resistance by film formation can be suppressed.

In addition to the above-mentioned auxiliary agent, biphenyl, cyclohexylbenzene, diphenyl ether, t-butylbenzene, t- as an overcharge preventing agent that effectively suppresses battery explosion / ignition when the battery is overcharged. Aromatic compounds such as pentylbenzene, diphenyl carbonate, and methylphenyl carbonate are listed.
In addition, auxiliary agents for improving battery cycle characteristics and low temperature discharge characteristics include lithium monofluorophosphate, lithium difluorophosphate, lithium fluorosulfonate, lithium bis (oxalato) borate, lithium difluorooxalatoborate, lithium tetrafluoro. Examples thereof include lithium salts such as oxalate phosphate and lithium difluorobis (oxalato) phosphate.

  Auxiliaries that can improve capacity retention characteristics and cycle characteristics after high-temperature storage include sulfur-containing compounds such as ethylene sulfite, propane sultone, and propene sultone; carboxylic acids such as succinic anhydride, maleic anhydride, and citraconic anhydride Examples of acid anhydrides include nitrile compounds such as succinonitrile, glutaronitrile, adiponitrile, and pimelonitrile.

<Separator>
In a non-aqueous secondary battery, a separator is usually interposed between the positive electrode and the negative electrode in order to prevent a short circuit. In this case, the above non-aqueous electrolyte is usually used by impregnating the separator.
The material and shape of the separator are not particularly limited, and known ones can be arbitrarily adopted as long as the effects of the present invention are not significantly impaired. Among these, it is preferable to use a porous sheet or a nonwoven fabric in which a resin, glass fiber, an inorganic material, or the like formed of a material that is stable with respect to the non-aqueous electrolyte is used, and has excellent liquid retention.

As materials for the resin and glass fiber separator, for example, polyolefins such as polyethylene and polypropylene, aromatic polyamides, polytetrafluoroethylene, polyethersulfone, glass filters and the like can be used.
A glass filter or a polyolefin is preferable, and a polyolefin is more preferable.
These materials may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

The thickness of the separator is arbitrary, but is usually 1 μm or more, preferably 5 μm or more, more preferably 10 μm or more, and usually 50 μm or less, preferably 40 μm or less, more preferably 30 μm or less.
If the separator is too thin than the above range, the insulating properties and mechanical strength may decrease. On the other hand, if it is thicker than the above range, not only battery performance such as rate characteristics may be lowered, but also the energy density of the entire non-aqueous secondary battery may be lowered.

  On the other hand, as the inorganic separator, for example, oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates such as barium sulfate and calcium sulfate are used. Used.

EXAMPLES 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.
Methods such as various evaluations performed in Examples and Comparative Examples are shown below.

<Average particle diameter (d50)>
The average particle diameter (d50) of the active material (A) is such that 0.01 g of the active material (A) as a sample is suspended in 10 mL of a 0.2% by mass aqueous solution of polyoxyethylene sorbitan monolaurate as a surfactant. The sample was introduced into a laser diffraction / scattering particle size distribution measuring device (trade name: LA-920 manufactured by HORIBA), irradiated with 28 kHz ultrasonic waves at an output of 60 W for 1 minute, and then measured as a volume-based median diameter in the measuring device. .

<Tap density>
For the tap density of the active material (A), a sample active material (A) is dropped through a sieve having a mesh size of 300 μm through a cylindrical tap cell having a diameter of 1.6 cm and a volume capacity of 20 cm ³ using a powder density measuring instrument. After the cell was fully filled, a tap with a stroke length of 10 mm was performed 1000 times, and the volume at that time and the weight of the sample were obtained.

<BET specific surface area (SA)>
The BET specific surface area of the active material (A) was measured by a BET 5-point method by a nitrogen gas adsorption flow method using a specific surface area measuring device.

<Slurry preparation>
20 g of active material and 20 g of carboxymethylcellulose aqueous solution (1% by mass) were mixed and kneaded at 2000 rpm for 5 minutes with a kneader (Awatori Kentaro, manufactured by Shinky Co., Ltd.), then at 2200 rpm for 1 minute. Then, 0.5 g of styrene-butadiene rubber aqueous dispersion (40% by mass) was added, and kneading was again performed under the same conditions as above to prepare an active material slurry.
In addition, an active material is produced in the Example or comparative example mentioned later.

<Plate production>
A copper foil (thickness: 18 μm) was placed on an Auto Film Applicator manufactured by Tester Sangyo Co., Ltd. and adsorbed by negative pressure. The prepared active material slurry was placed on a copper foil, and the slurry was applied by sweeping a film applicator manufactured by Tester Sangyo at a speed of 10 mm / sec.

The copper foil coated with the active material slurry was dried in an inert oven (EPEC-75, manufactured by Isuzu Seisakusho Co., Ltd.) to obtain an electrode plate having an active material layer formed on the copper foil (90 ° C., 50 minutes, Nitrogen stream 10 L / min).
Thereafter, the electrode plate is passed through a press machine (3-ton mechanical precision roll press) to compress the active material layer, and the density of the active material layer is adjusted to 1.60 ± 0.03 g / cm ³ , Obtained.
The portion of the electrode sheet on which the copper foil active material slurry was applied was punched with a punching punch (φ = 12.5 mm, SNG, manufactured by Nogami Giken Co., Ltd.), and weighed and a film thickness meter (IDS-112, Inc.). The film thickness was measured by Mitutoyo Corporation, and the basis weight and the density of the active material layer were calculated.

<Coin cell production>
The produced electrode sheet was punched into a disk shape with a diameter of 12.5 mm to form an electrode, and a lithium metal foil was punched into a disk shape with a diameter of 14 mm to form a counter electrode. Between both electrodes, an electrolyte solution in which LiPF ₆ was dissolved to 1.2 mol / L was impregnated in a mixed solution of ethylene carbonate / dimethyl carbonate / ethyl methyl carbonate = 15/80/5 (volume ratio). A separator (made of a porous polyethylene film) was placed, and a 2016 coin type battery using the electrolytic solution was produced.

  All the operations were performed in a glove box (OMNI-LAB, manufactured by Vacuum atoms, filled with Ar, oxygen concentration 0.2 ppm or less, moisture concentration 0.5 ppm). Further, the coin cell members and the like were dried for 12 hours or more using a vacuum dryer (Vos-451SD, manufactured by Tokyo Rika Kikai Co., Ltd.) and then carried into the glove box.

<Charge / discharge evaluation of coin cell>
The charge / discharge evaluation of the produced coin cell (2016 coin type multi-battery) was performed using the charge / discharge program shown in Table 1 below.

  In the table, “CC-CV charging” means charging after a certain amount of charge at a constant current until charging reaches a termination condition at a constant voltage. “CC discharge” means discharging at a constant current to the end condition.

  Initial charge / discharge efficiency (%) and capacity loss (mAh / g) were calculated from the following formulas.

Initial charge / discharge efficiency (%) = discharge capacity in the fourth cycle / (discharge capacity in the fourth cycle + capacity loss in the second, third, and fourth cycles) × 100 (%)
Capacity loss (mAh / g) = second cycle (charge capacity-discharge capacity) + third cycle (charge capacity-discharge capacity) + fourth cycle (charge capacity-discharge capacity)

<Production of laminate cell>
Lithium nickel manganese cobaltate (LiNi _1/3 Mn _1/3 Co _1/3 O ₂ ) is used as the positive electrode active material, and this is mixed with a conductive agent and polyvinylidene fluoride (PVdF) as a binder to form a slurry. did. 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 .

The negative electrode is obtained by cutting the electrode sheet prepared by the method described in <Preparation of electrode plate> 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. Using. The density of the negative electrode active material layer at this time was 1.6 g / cm ³ .

One positive electrode and one 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. 200 μL of lithium phosphate (LiPF ₆ ) dissolved therein was injected, sufficiently infiltrated into the electrode, and then sealed to prepare a laminate cell.
The rated capacity of this battery is 34 mAh.

<Calculation method of organic compound (mass% vs. active material for negative electrode)>
The ratio of the organic compound to the active material (A) was the amount of the organic compound added at the time of preparation of the non-aqueous secondary battery negative electrode active material (excluding Example 11).

<Conditioning of laminate cell and measurement of initial gas amount>
In an environment of 25 ° C., initial conditioning is performed in a voltage range of 4.2 to 3.0 V and a current value of 0.2 C (the rated capacity due to the discharge capacity at 1 hour rate is 1 C). went. Volume measurement was performed before and after conditioning the laminate cell, and the amount of change was regarded as the initial gas amount. For measuring the volume of the laminate cell, the Archimedes method was used with ethanol as the immersion liquid.

<Measurement of amount of gas stored in laminate cell>
The laminate cell was stored at a high temperature at 85 ° C. for 1 day, and the amount of gas generated after storage was evaluated. Regarding the gas, the volume change amount of the laminate cell before and after storage was regarded as the gas generation amount, and the Archimedes method was used for volume measurement using ethanol as an immersion liquid.

[Example 1]
<Preparation of non-aqueous secondary battery negative electrode active material>
50 g of spheroidized natural graphite (average particle diameter (d50) = 17 μm, BET specific surface area (SA) = 6.7 m ² / g, tap density = 1.02 g / cm ³ ) as an active material (A), an organic compound 50 g of an aqueous solution 1 (a 30% by weight aqueous lithium polystyrene sulfonate solution manufactured by Aldrich (0.15% by weight of polystyrene polystyrene sulfonate obtained by adding 49.833 g of distilled water to 0.167 g of a weight average molecular weight: 75000)) in a flask. The mixture was mixed, heated to 95 ° C. and stirred, and then the solvent was distilled off to obtain a powdered non-aqueous secondary battery negative electrode active material A.

After 240 mg of this active material A and 400 μL of an electrolyte (ethylene carbonate (EC) / dimethyl carbonate (DMC) / ethyl methyl carbonate (EMC) = 3/3/4 (volume ratio)) were put in a Lami pack, a heat sealer was used. And sealed. This cell was placed in a constant temperature layer at 75 ° C. and stored for 3 days.
After taking out the Lamipack after the storage test, the contents were dried, the remaining solid content was dissolved in a heavy solvent for NMR (d-DMSO), and ¹ H-NMR measurement was performed. From the result, the amount of lithium polystyrene sulfonate, which was an eluted organic compound, was quantified and found to be 2% by mass or less.

[Example 2]
A powdery active material B for a nonaqueous secondary battery negative electrode is obtained in the same manner as in Example 1 except that 50 g of the aqueous solution 1 of the organic compound is replaced with 50 g of the aqueous solution 2 (0.2% by mass of polystyrene sulfonate lithium aqueous solution). It was.
Example 3
A powdery active material C for a negative electrode of a non-aqueous secondary battery is obtained in the same manner as in Example 1 except that the aqueous solution 1 of the organic compound is replaced with 50 g of the aqueous solution 3 (0.5% by mass of lithium polystyrene sulfonate). It was.

Example 4
A powdery non-aqueous secondary battery negative electrode active material D is obtained in the same manner as in Example 1 except that the aqueous solution 1 of the organic compound is replaced with 50 g of the aqueous solution 4 (0.75% by weight of polystyrene sulfonate lithium aqueous solution). It was.
Example 5
A powdered active material E for a negative electrode of a non-aqueous secondary battery is obtained in the same manner as in Example 1 except that the aqueous solution 1 of the organic compound is replaced with 50 g of the aqueous solution 5 (1.0 mass% lithium polystyrene sulfonate aqueous solution). It was.

Example 6
A powdered active material F for a negative electrode of a non-aqueous secondary battery is obtained in the same manner as in Example 1 except that the aqueous solution 1 of the organic compound is replaced with 50 g of the aqueous solution 6 (3.0 mass% lithium polystyrene sulfonate aqueous solution). It was.
Example 7
The powdered non-aqueous system was the same as in Example 1 except that the aqueous solution 1 of the organic compound was replaced with 50 g of an aqueous solution 7 (0.5% by weight aqueous sodium polystyrenesulfonate (PS-5) manufactured by Tosoh Organic Chemical Co., Ltd.). An active material G for secondary battery negative electrode was obtained.

Example 8
Aqueous solution 1 of an organic compound was mixed with aqueous solution 8 (Tosoh Organic Chemical Co., Ltd., styrene-sodium styrenesulfonate copolymer, styrene: sodium styrenesulfonate = 35: 65 (molar ratio), weight average molecular weight: 74,000, 0.5 mass) % Aqueous solution) A powdery non-aqueous secondary battery negative electrode active material H was obtained in the same manner as in Example 1 except that 50 g was used.

Example 9
An aqueous solution 1 of an organic compound was mixed with an aqueous solution 9 (Tosoh Organic Chemical Co., Ltd., styrene-sodium styrenesulfonate copolymer, styrene: sodium styrenesulfonate = 50: 50 (molar ratio), weight average molecular weight: 24,000, 0.5 mass) % Aqueous solution) A powdery non-aqueous secondary battery negative electrode active material I was obtained in the same manner as in Example 1 except that 50 g was used.

Example 10
When active material A is not coated with an organic compound and dried, and an active material slurry is prepared, 20 g of spheroidized natural graphite, 20 g of a carboxymethyl cellulose aqueous solution (1% by mass), and an aqueous solution 10 of an organic compound (lithium sulfonate polystyrene from Aldrich) After mixing 0.333 g of 30% by weight aqueous solution (weight average molecular weight: 75000) and kneading at 2000 rpm for 5 minutes with a kneader (Awatori Kentaro, manufactured by Shinky Co., Ltd.), 2200 rpm for 1 minute. Defoaming was performed under the conditions, 0.5 g of styrene-butadiene rubber aqueous dispersion (40% by mass) was added, and kneading was again performed under the same conditions as above to obtain the non-aqueous secondary battery negative electrode active material J. Obtained.

Example 11
After mixing 50 g of spheroidized natural graphite and 50 g of an organic compound solution 11 (Tosoh Organic Chemical Co., Ltd. (PS-5), 0.5 mass% sodium polystyrenesulfonate aqueous solution) in a flask for 1 hour, The solvent was removed by suction filtration using a Kiriyama funnel. Thereafter, 25 g of distilled water was poured over the filtrate to wash the filtrate. The filtered material after washing was dried at 150 ° C. for 7 hours to obtain a non-aqueous secondary battery negative electrode active material K.
In addition, the ratio of the organic compound with respect to the active material (A) was calculated from the amount of the organic compound contained in the filtrate.

Example 12
For powdered non-aqueous secondary battery negative electrode in the same manner as in Example 1 except that the organic compound aqueous solution 1 was replaced with 50 g of an organic compound aqueous solution 12 (0.5% by mass aqueous solution of low-conductivity polyaniline sulfonic acid). An active material L was obtained.

[Comparative Example 1]
Spherical natural graphite as an active material (A) containing no organic compound (average particle diameter (d50) = 17 μm, BET specific surface area (SA) = 6.7 m ² / g, tap density = 1.02 g / Graphite consisting of only cm ³ ) was used as the non-aqueous secondary battery negative electrode active material Z. The spheroidized natural graphite used here is the same as that used in Example 1. The non-aqueous secondary battery negative electrode active material Z is simply described as “spheroidized natural graphite” in Table 1.

[Comparative Example 2]
The aqueous solution 1 of the organic compound was stirred after adding 50 g of water to 5.1 g of the aqueous solution 13 (polyacrylic acid (weight average molecular weight 5000) manufactured by Wako), and 80 g of an aqueous 5 mass% lithium hydroxide monohydrate solution was added. Non-aqueous secondary as in Example 1 except that 6.6667 g was weighed from an aqueous solution (around pH = 10) and then replaced with 50 g of an aqueous solution diluted by adding 43.3333 g of distilled water thereto. An active material M for battery negative electrode was obtained.

[Comparative Example 3]
An aqueous solution 1 of an organic compound was added to an aqueous solution 14 (added 0.64 g of a 1 mol / L hydrochloric acid aqueous solution to 10.0 g of a 25 mass% sodium polyvinylsulfonate aqueous solution manufactured by Aldrich, and then 2.3 g of a 1 mass% lithium hydroxide aqueous solution was added. A nonaqueous system was obtained in the same manner as in Example 1 except that 1.2953 g was weighed from the stirred solution (pH = 9), and was then replaced with 50 g of an aqueous solution diluted by adding 48.7047 g of distilled water. An active material N for secondary battery negative electrode was obtained.

[Comparative Example 4]
Example 1 except that the aqueous solution 1 of the organic compound was replaced with 50 g of an aqueous solution 15 (an aqueous solution obtained by adding 49.000 g of distilled water to 1.000 g of an aqueous 25 mass% sodium polyvinylsulfonate solution manufactured by Aldrich). Thus, an active material O for a nonaqueous secondary battery negative electrode was obtained.
[Comparative Example 5]
An aqueous solution 1 of an organic compound was added to an aqueous solution 16 (1.000 g of an ethylene-vinyl alcohol (EVOH) copolymer Soarnol (product number: D2908) manufactured by Nippon Synthetic Chemical Co., Ltd.) in an ethanol / water mixed solvent (50% by mass / 50% by mass). A non-aqueous secondary battery negative electrode active material P was obtained in the same manner as in Example 1 except that 12.5 g was replaced with 12.5 g of a 4% EVOH aqueous solution dissolved in 000 g.

  Using the prepared non-aqueous secondary battery negative electrode active materials A to P and Z, slurries were prepared in the same manner as in Example 1 to evaluate the charge / discharge of the coin cell, the initial gas amount measurement of the laminate cell, and the storage gas amount. Measurements were made. The results and the electrical conductivity of the organic compound are summarized in Table 2 below.

Example 13
For the active material C, the total amount of the initial gas amount and the storage gas amount was determined in the same manner as in Example 3 except that the conditions for measuring the storage gas amount of the laminate cell were changed to 70 ° C. for 3 days.

Example 14
The total amount of the initial gas amount and the storage gas amount was determined in the same manner as in Example 13 except that 1% (mass ratio) of 1,6-diisocyanatohexane was added to the electrolyte solution.

[Comparative Example 6]
For the active material Z, the total amount of the initial gas amount and the storage gas amount was determined in the same manner as in Comparative Example 1 except that the conditions for measuring the storage gas amount of the laminate cell were changed to 70 ° C. for 3 days.

[Comparative Example 7]
The total amount of the initial gas amount and the storage gas amount was determined in the same manner as in Comparative Example 6, except that 1% (mass ratio) of 1,6-diisocyanatohexane was added to the electrolyte solution.

  The results of calculating the total of the initial gas amount and the storage gas amount from the above measurements are shown in Table 3 below.

  The non-aqueous secondary battery negative electrode active materials (Examples 1 to 12) containing the active material (A) and the organic compound (B) were compared with the non-aqueous secondary battery negative electrode active materials of Comparative Examples 1 to 5. Thus, it is understood that the initial charge / discharge efficiency (%) is improved and the capacity loss is reduced. Moreover, compared with the active material for non-aqueous secondary battery negative electrodes of the comparative examples 6 and 7, it turned out that long-term gas generation is also reduced in Examples 13 and 14. From this, it can be seen that, due to the effect of the organic compound (B), the active material surface is coated to suppress the reductive decomposition of the electrolytic solution, thereby reducing the capacity loss and suppressing the gas generation.

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 initial charge and discharge efficiency is further improved while suppressing the generation of gas. It is a well-balanced negative electrode material for non-aqueous secondary batteries that can be improved and capacity loss associated with charge / discharge cycles can be suppressed.
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 an organic compound (B),
A nonaqueous secondary battery negative electrode active material, wherein the organic compound (B) has an ionic group and an aromatic ring.   The amount of elution of the organic compound (B) into the non-aqueous electrolyte solution when immersed in a non-aqueous electrolyte solution at 75 ° C for 3 days is 30% by mass or less of the whole organic compound (B). The active material for nonaqueous secondary battery negative electrodes as described in 2.   The active material for a nonaqueous secondary battery negative electrode according to claim 1 or 2, wherein the organic compound (B) is contained in an amount of 0.1 to 5 parts by mass with respect to 100 parts by mass of the active material (A).   The active material for a nonaqueous secondary battery negative electrode according to any one of claims 1 to 3, wherein the active material (A) is spheroidized natural graphite.   The ionic group of the organic compound (B) is at least one ionic group selected from the group consisting of a carboxylic acid group, a sulfonic acid group, a phosphoric acid group, a phosphonic acid group, and salts thereof. The active material for nonaqueous secondary battery negative electrodes as described in any one of 1-4.   The organic compound (B) includes a structural unit derived from a monomer having a carboxylic acid group or a sulfonic acid group or a salt thereof and a structural unit derived from a monomer having an aromatic ring, and the weight of the organic compound (B) The active material for a non-aqueous secondary battery negative electrode according to any one of claims 1 to 5, having an average molecular weight of 500 or more and 1,000,000 or less.   The organic compound (B) is polystyrene sulfonate, lithium polystyrene sulfonate, sodium polystyrene sulfonate, styrene-styrene sulfonate copolymer, styrene-lithium sulfonate copolymer, styrene-sodium styrene sulfonate copolymer. , Polyvinyl benzoic acid, polyvinyl lithium benzoate, sodium polyvinyl benzoate, styrene-vinyl benzoic acid copolymer, styrene-vinyl lithium benzoate copolymer, styrene-vinyl sodium benzoate copolymer, lithium naphthalene sulfonate and naphthalene The active material for a nonaqueous secondary battery negative electrode according to any one of claims 1 to 6, which is at least one compound selected from the group consisting of sodium sulfonate. The electric conductivity of the organic compound (B) is greater than 0 S / cm at 25 ° C. and 0.1 S / cm or less, for a non-aqueous secondary battery negative electrode according to claim 1. Active material.   The negative electrode for nonaqueous secondary batteries formed using the active material for nonaqueous secondary battery negative electrodes as described in any one of Claims 1-8.   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 9. .   The non-aqueous secondary battery according to claim 10, wherein the electrolyte contains an isocyanate compound.