JP5929187B2 - Method for producing negative electrode material for non-aqueous electrolyte secondary battery, and negative electrode material for non-aqueous electrolyte secondary battery produced by the production method - Google Patents

Description

  The present invention relates to a method for producing a negative electrode material used for a non-aqueous electrolyte secondary battery, and a negative electrode material produced by the production method.

  In recent years, demand for high-capacity secondary batteries has increased with the downsizing of electronic devices. In particular, lithium ion secondary batteries having higher energy density and excellent large current charge / discharge characteristics have attracted attention as compared to nickel / cadmium batteries and nickel / hydrogen batteries.

It is known that graphite is used as a carbon material for a lithium ion secondary battery. In particular, when graphite having a high degree of graphitization is used as a negative electrode active material for a lithium ion secondary battery, a capacity close to 372 mAh / g, which is the theoretical capacity of lithium occlusion of graphite, can be obtained. Since it is excellent, it is known that it is preferable as an active material.

  On the other hand, an attempt to improve battery characteristics by including boron in graphite has been proposed. Patent Document 1 discloses a graphite powder produced by adding a boron compound to pitch and then firing and graphitizing at a high temperature of 2000 ° C. or higher, which improves charge / discharge efficiency and increases capacity. It can be achieved at the same time.

  In Patent Document 2, a graphite powder is used as a raw material, and after adding a boron compound and a fusible organic powder, the boron compound does not cause solid solution, carbonization / nitridation, or graphitization of carbonized organic matter. A carbon material powder obtained by performing a heat treatment at a low temperature is disclosed, and the irreversible capacity is remarkably reduced.

JP 2000-149947 A JP 2008-288153 A

While the market demands improved performance for lithium ion secondary batteries, the negative electrode materials described in the above-mentioned patent documents have not been studied at all regarding negative electrode charge transfer resistance (R _CT ). An object of the present invention is to provide a negative electrode material capable of designing a non-aqueous electrolyte secondary battery having a good balance between low irreversible capacity and low negative electrode charge transfer resistance.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors mixed an organic compound and a Group 13 element-containing compound of the periodic table, and then coated the mixture on a carbon material, and then 600 ° C. As described above, by firing at 2300 ° C. or lower, it was conceived that a negative electrode material capable of designing a non-aqueous electrolyte secondary battery having a good balance of low irreversible capacity and low negative electrode charge transfer resistance was obtained, and the present invention was completed. I let you.

That is, the negative electrode material of the present invention is a method for producing a negative electrode material for a non-aqueous electrolyte secondary battery, which contains a Group 13 element-containing compound of the periodic table and is coated with amorphous carbon.
A mixing step of mixing an organic compound having a softening point of 150 ° C. or less and a Group 13 element-containing compound of the periodic table at or above the softening point of the organic compound;
The coating which coat | covers the mixture obtained by the said mixing process on the carbon material in the ratio of 0.05 mass% or more and 0.6 mass% or less in conversion of the periodic table group 13 element mass with respect to 100 mass% of carbon materials A firing step of firing the coated carbon material obtained in the coating step at 600 ° C. or higher and 2300 ° C. or lower,
Is a method for producing a negative electrode material for a non-aqueous electrolyte secondary battery.

By using the negative electrode material of the present invention as a negative electrode material for a non-aqueous electrolyte secondary battery, it is possible to design a battery with a low irreversible capacity and a good balance of low negative electrode charge transfer resistance (R _CT ).

Hereinafter, the contents of the present invention will be described in detail. The description of the invention constituent elements described below is an example (representative example) of an embodiment of the present invention, and the present invention is not limited to these forms unless it exceeds the gist.
The manufacturing method of the negative electrode material of this invention is a manufacturing method of the negative electrode material for nonaqueous electrolyte secondary batteries which contains a periodic table group 13 element containing compound, and the carbon material is coat | covered with the amorphous carbon. And the mixing process obtained by mixing the organic compound having a softening point of 150 ° C. or less and the Group 13 element-containing compound of the periodic table at or above the softening point of the organic compound, the carbon material in the mixing process, A coating step of coating at a ratio of 0.05% by mass or more and 0.6% by mass or less in terms of the mass of Group 13 elements of the periodic table with respect to 100% by mass of the carbon material, and the coated carbon obtained in the coating step It includes the three steps of firing the material at 600 ° C. or higher and 2300 ° C. or lower.

<Mixing process>
The mixing step is a step of mixing an organic compound having a softening point of 150 ° C. or less and a Group 13 element-containing compound of the periodic table at or above the softening point of the organic compound.
The organic compound is not particularly limited as long as it has a softening point of 150 ° C. or lower and becomes amorphous carbon by firing. Specific examples of organic compounds include coal-based heavy oils such as coal tar pitch and dry-distilled liquefied oil; straight-run heavy oils such as atmospheric residual oil and vacuum residual oil; by-products during pyrolysis of crude oil, naphtha, etc. Petroleum heavy oils such as cracked heavy oils such as ethylene tar; aromatic hydrocarbons such as acenaphthylene, decacyclene and anthracene; nitrogen-containing cyclic compounds such as phenazine and acridine; sulfur-containing cyclic compounds such as thiophene; adamantane, etc. Aliphatic cyclic compounds of the above; polyphenylenes such as biphenyl and terphenyl; polyvinyl esters such as polyvinyl chloride, polyvinyl acetate and polyvinyl butyral; and thermoplastic polymers such as polyvinyl alcohol. The softening point is preferably 150 ° C. or lower, more preferably 80 ° C. or lower, further preferably 50 ° C. or lower, and particularly preferably liquid at 20 ° C.

The group 13 element of the periodic table usually includes boron, aluminum, gallium, indium and thallium, and the group 13 element compound of the periodic table is a compound containing one or more of these. Among these, a compound containing boron and / or aluminum can be preferably used because of its availability. Examples of the compound containing the above-described element include oxides, sulfides, inorganic acids, and inorganic acid salts. Among these, it is preferable that it is a compound containing boron, and it is preferable to include one or more compounds selected from the group consisting of boron oxide, boric acid, boron carbide, and boron nitride. Negative electrode charge transfer resistance (R _CT ) can be reduced by adding a mixture of an organic compound and a Group 13 element-containing compound in the periodic table to the negative electrode material as amorphous carbon.

The mixing in the mixing step is not particularly limited as long as the mixing is performed above the softening point of the organic compound. For example, in the case of a rotary mixer: a cylindrical mixer, a twin cylinder mixer, a double cone mixer Machine, regular cubic mixer, vertical mixer, fixed mixer: spiral mixer, ribbon mixer, Muller mixer, Helical Flight mixer, Pugmill
A mold mixer, a fluidized mixer, or the like can be used. The mixing temperature is not lower than the softening point of the organic compound, preferably 10 ° C. or higher than the softening point, and more preferably 20 ° C. or higher than the softening point. The upper limit is usually 200 ° C. or lower, preferably 150 ° C. or lower, more preferably 100 ° C. or lower, particularly preferably 50 ° C. or lower. If the heating temperature is too low, the viscosity of the organic compound may be high and mixing may be difficult. If the heating temperature is too high, the viscosity of the mixed system may be too high due to volatilization and polycondensation of the organic compound.

The mixing ratio of the organic compound and the group 13 element-containing compound in the periodic table in the mixing step is not particularly limited, but the mixing ratio (mass ratio) of the group 13 element-containing compound in the periodic table to the organic compound is usually 1: 0.001. As described above, it is preferably 1: 0.01 or more, more preferably 1: 0.02 or more, and particularly preferably 1: 0.1 or more. Moreover, it is usually preferably 1:10 or less, preferably 1: 1 or less, more preferably 1: 0.5 or less, further preferably 1: 0.3 or less, and 1: 0.2 or less. It is particularly preferred that However, the above-mentioned mixing ratio is calculated in terms of the amount of residual carbon derived from the organic compound, and in the group 13 element-containing compound of the periodic table in terms of the amount of group 13 element of the periodic table.
By satisfying such a range, the group 13 element-containing compound in the periodic table tends to be more uniformly dispersed in the organic compound, the negative electrode charge transfer resistance (R _CT ) is reduced, and the input / output characteristics are improved. Is possible.

<Coating process>
The covering step is a step of covering the carbon material with the mixture obtained in the mixing step.
As the carbon material, a material selected from natural graphite, artificial graphite, amorphous-coated graphite, and amorphous carbon can be used. These carbon materials can be used alone or in combination of two or more in any composition and combination.

As the amorphous carbon, for example, particles obtained by firing a bulk mesophase or particles obtained by firing a carbon precursor after infusibility treatment can be used.
In addition, graphite is easily available commercially, and can theoretically have a high charge / discharge capacity of 372 mAh / g. Therefore, it can be obtained at a higher current density than when other negative electrode active materials are used. This is preferable because the effect of improving the charge / discharge characteristics is remarkably large.

  As the graphite, either natural graphite or artificial graphite may be used. As graphite, those with few impurities are preferable, and they are used after being subjected to various purification treatments as necessary. Further, those having a high degree of graphitization are preferable. Specifically, the interplanar spacing (d002) of (002) planes by X-ray wide angle diffraction method is usually carbon of 0.335 nm or more and less than 0.340 nm. . Here, the d002 value is preferably 0.339 nm or less, more preferably 0.337 nm or less. If the d002 value is too large, the crystallinity may decrease and the initial irreversible capacity may increase. On the other hand, 0.335 nm is a theoretical value of graphite.

  As natural graphite, for example, highly purified flaky graphite or spheroidized graphite can be used. Among these, natural graphite subjected to spheroidizing treatment is particularly preferable from the viewpoint of particle filling properties and charge / discharge load characteristics.

As an apparatus used for the spheroidization 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 mechanical action such as impact compression, friction, shearing force, etc. on the carbon material introduced inside the rotor by rotating at high speed. An apparatus that provides a surface treatment is preferable. Moreover, it is preferable to have a mechanism that repeatedly gives mechanical action by circulating the carbon material. Preferable apparatuses include, for example, a hybridization system (manufactured by Nara Machinery Co., Ltd.), kryptron (manufactured by Earth Technica Co., Ltd.), CF mill (manufactured by Ube Industries, Ltd.), mechanofusion system (manufactured by Hosokawa Micron Corporation), Etc.). Among these, a hybridization system manufactured by Nara Machinery Co., Ltd. is preferable.

  For example, when processing using the above-mentioned apparatus, the peripheral speed of the rotating rotor is preferably 30 to 100 m / sec, more preferably 40 to 100 m / sec, and 50 to 100 m / sec. Is more preferable. The treatment can be performed by simply passing a carbonaceous material, but it is preferable to circulate or stay in the apparatus for 30 seconds or longer, and it is preferable to circulate or stay in the apparatus for 1 minute or longer. More preferred.

  Specific examples of 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, Organic compounds such as polyvinyl alcohol, polyacrylonitrile, polyvinyl butyral, natural polymer, polyphenylene sulfide, polyphenylene oxide, furfuryl alcohol resin, phenol-formaldehyde resin, imide resin are usually in the range of 2500 ° C. or higher and usually 3200 ° C. or lower. Examples thereof include those calcined at a temperature and graphitized. At this time, a silicon-containing compound or a boron-containing compound can also be used as a graphitization catalyst.

  Furthermore, when obtaining a carbon material with a low degree of graphitization, the firing temperature of the organic substance is usually 600 ° C. or higher, preferably 900 ° C. or higher, more preferably 950 ° C. or higher. The upper limit varies depending on the desired degree of graphitization to be imparted to the carbon material, but is usually 2500 ° C. or lower, preferably 2000 ° C. or lower, more preferably 1400 ° C. or lower. At the time of baking, acids such as phosphoric acid, boric acid and hydrochloric acid, and alkalis such as sodium hydroxide may be mixed with the organic matter.

As the carbon material, particles such as metal particles and metal oxide particles may be appropriately mixed and used in an arbitrary combination with the carbon material. Further, a plurality of materials may be mixed in each particle. For example, carbonaceous particles having a structure in which the surface of graphite is covered with a carbon material having a low graphitization degree, or particles obtained by aggregating graphite particles with an appropriate organic substance and regraphitizing may be used.
As amorphous-coated graphite, for example, natural graphite or artificial graphite coated with an amorphous precursor and fired, or natural graphite or artificial graphite coated with amorphous by CVD can be used.
Furthermore, the composite particles may contain a metal that can be alloyed with Li, such as Sn, Si, Al, Bi.

<Physical properties of carbon materials>
The carbon material in the present invention preferably has the following physical properties. In addition, although the measuring method of the physical property of the carbon material in this invention does not have a restriction | limiting in particular, unless there is a special situation, it will follow the measuring method as described in an Example.

(1) Average particle diameter of carbon material (d50)
Although there is no restriction | limiting in particular about the average particle diameter (d50) of a carbon material, As a range to be used, d50 is 50 micrometers or less normally, Preferably it is 30 micrometers or less, More preferably, it is 25 micrometers or less. Moreover, it is 1 micrometer or more, Preferably it is 4 micrometers or more, More preferably, it is 10 micrometers or more. If this particle size is too large, there is a tendency for inconveniences such as striping when it is made into a plate, and if the particle size is too small, the surface area becomes too large and the activity with the electrolyte is suppressed. There is a tendency to become difficult.
The average particle size is measured by suspending 0.01 g of carbon material in 10 mL of a 0.2% by weight aqueous solution of polyoxyethylene sorbitan monolaurate, which is a surfactant, and commercially available laser diffraction / scattering particle size distribution. After being introduced into the measuring apparatus and irradiating 28 kHz ultrasonic waves at an output of 60 W for 1 minute, measured as a volume-based median diameter in the measuring apparatus is defined as d50 in the present invention.

(2) BET specific surface area (SA) of carbon material
The specific surface area of the carbon material measured by the BET method is usually 1 m ² / g or more, preferably 1.5 m ² / g or more. Moreover, it is 11 m < ² > / g or less normally, Preferably it is 9 m < ² > / g or less, More preferably, it is 8 m < ² > / g or less. If the specific surface area is too small, there are few sites where Li enters and exits, and there is a tendency to be inferior in the output characteristics of the high-speed charge / discharge characteristics. On the other hand, if the specific surface area is too large, the active material becomes excessively active with respect to the electrolyte. Since the capacity increases, there is a possibility that a high-capacity battery cannot be manufactured.
In addition, the measuring method of a BET specific surface area is measured by a BET 1 point method by a nitrogen gas adsorption circulation method using a specific surface area measuring device.

(3) X-ray structural analysis (XRD) of carbon materials
Rhombedral obtained from X-ray structural analysis (XRD) of carbon material
The abundance ratio (3R / 2H) of Hexagonal crystals with respect to
01 or more and 0.50 or less. If the 3R / 2H value is below this range, the high-speed charge / discharge characteristics may be deteriorated. If the 3R / 2H value is above this range, it is difficult to adjust the 3R / 2H value, and it is necessary to perform the manufacturing process strongly for a long time. There is a tendency that the number of processes needs to be increased, which may cause a decrease in productivity and an increase in cost.
In the X-ray structural analysis (XRD) measurement method, a 0.2 mm sample plate is filled so that the carbon material is not oriented, and is measured with an X-ray diffractometer at an output of 30 kV and 200 mA with CuKα rays. After subtracting the background from the obtained 3R (101) near 43.4 ° and 2H (101) near 44.5 °, the intensity ratio 3R (101) / 2H (101) can be calculated. .

(4) Tap density of carbon material The tap density of the carbon material is usually preferably 0.7 g / cm ³ or more and 1 g / cm ³ or more. Moreover, 1.3 g / cm < ³ > or less and 1.2 g / cm < ³ > or less are preferable normally, and 1.1 g / cm < ³ > or less is more preferable. If the tap density is too low, the high-speed charge / discharge characteristics are inferior. If the tap density is too high, the carbon density in the particles increases, the rolling property is insufficient, and it is difficult to form a high-density negative electrode sheet.
The tap density was measured by using a powder density measuring device to drop a carbon material into a cylindrical tap cell having a diameter of 1.6 cm and a volume capacity of 20 cm ³ through a sieve having an opening of 300 μm, and filling the cell fully. A tap having a stroke length of 10 mm is performed 1000 times, and the density obtained from the volume and the weight of the sample is defined as the tap density.

(5) Raman R value of Raman spectrum (Raman) spectrum carbon material a 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 The intensity ratio R (R = I _B / I _A ) is calculated and defined. The value is usually 0.01 or more, preferably 0.1 or more. Moreover, it is 1 or less normally, Preferably it is 0.5 or less. If the Raman R value is too small, the crystallinity of the particle surface becomes too high, and when the density is increased, the crystals tend to be oriented in a direction parallel to the electrode plate, and the load characteristics tend to be lowered. On the other hand, if the Raman R value is too large, the crystal on the particle surface is disturbed, the reactivity with the electrolytic solution increases, and the efficiency tends to decrease and the gas generation increases.

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 rotated in a plane perpendicular to the laser beam while irradiating the measurement cell with an argon ion laser beam. Measure.
Argon ion laser light wavelength: 514.5 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)

(6) Surface functional group amount of carbon material (surface oxygen element amount O / C)
The surface functional group amount O / C value represented by the following (formula 1) of the carbon material is usually 0.01% or more, preferably 0.2% or more, more preferably 2% or more. Moreover, it is 10% or less normally, Preferably it is 3% or less. When the amount of the surface functional group is too small, the reactivity with the electrolytic solution is poor and stable SEI formation tends to be impossible. On the other hand, when the amount of surface functional groups is too large, the crystal on the particle surface is disturbed, the reactivity with the electrolyte increases, and the efficiency tends to decrease and gas generation increases. In addition, it is difficult to adjust the O / C value, and there is a tendency that the manufacturing process needs to be performed for a long time or the number of steps needs to be increased, which tends to cause a decrease in productivity and an increase in cost. is there.
(Formula 1)
O / C value (%) = O atom concentration determined based on the peak area of the O1s spectrum in X-ray photoelectron spectroscopy (XPS) analysis / C atom concentration determined based on the peak area of the C1s spectrum in XPS analysis × 100

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

The coating in the coating step is a step of coating the carbon material with the mixture obtained in the mixing step, and the coating ratio is not particularly limited, but the mixture obtained in the mixing step with respect to 100% by mass of the carbon material, In terms of the amount of residual carbon derived from the organic compound, it is usually 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 0.3% or more, further preferably 0.5% by mass or more, and usually 20% by mass. %, Preferably 15% by mass or less, more preferably 10% by mass or less, further preferably 8% by mass or less, and particularly preferably 6% by mass or less. Moreover, it is 0.05 mass% or more normally in conversion of the periodic table group 13 element amount with respect to 100 mass% of carbon materials, Preferably it is 0.08 mass% or more, More preferably, it is 0.10 mass% or more. 0.6 mass% or less, preferably 0.5 mass% or less, more preferably 0.3 mass% or less. By coating the carbon material with the Group 13 element of the periodic table at such a ratio and manufacturing the negative electrode material, the negative electrode charge transfer resistance (R _CT ) can be reduced and the input / output characteristics can be improved.
The amount of addition (mass%) in the present invention can be calculated from the firing yield before and after firing the material. At this time, the calculation is performed on the assumption that there is no change in the weight of the graphite particles before and after firing. When w1 is the graphite carbon particle mass (kg) before firing, w2 is the raw material mass (kg) of amorphous carbon, and a is the firing yield (%),
Graphite particles / amorphous carbon = 100 × {(w1 + w2) × a / 100−w1} / w1
Can be calculated.

The coating in the coating step can be performed by the same method as the mixing in the mixing step, and can also be performed by vapor deposition typified by the CVD method. In the case of coating by mixing, the method is not limited. For example, in the case of a rotary mixer: a cylindrical mixer, a twin cylindrical mixer, a double cone mixer, a regular cubic mixer, a saddle type For mixers and stationary mixers: spiral mixers, ribbon mixers, Muller mixers, Helical Fly
An ht type mixer, Pugmill type mixer, fluidized type mixer, or the like can be used. Also, the mixing temperature is not particularly limited and is usually mixed at room temperature. In the case of vapor deposition, for example, a filling method described in JP-A 2011-210462 is employed and heated, whereby uniform coating can be achieved.

<Baking process>
The firing step is a step of firing the coated carbon material obtained in the coating step at 600 ° C. or higher and 2300 ° C. or lower. Through this step, the organic compound becomes amorphous carbon, and the carbon material becomes amorphous carbon. Is a negative electrode material to be coated. When firing is performed at a low temperature of less than 600 ° C., the organic compound is not sufficiently amorphous carbon, and when it is performed at a temperature higher than 2300 ° C., the organic compound is graphitized. Further, if necessary, the VM material is subjected to de-VM firing to obtain an intermediate material from which volatile components (VM) generated from the organic compound are removed. The de-VM firing is usually performed at a temperature of 600 ° C. or higher, preferably 650 ° C. or higher, usually 1300 ° C. or lower, preferably 1100 ° C. or lower, usually for 0.1 hour to 10 hours. In order to prevent oxidation, heating is usually performed in a non-oxidizing atmosphere in which an inert gas such as nitrogen or argon is circulated or a granular carbon material such as breeze or packing coke is filled in the gap.

Firing of the mixture is 600 ° C. or higher, preferably 700 ° C. or higher, more preferably 800 ° C. or higher, more preferably 900 ° C. or higher, particularly preferably 1000 ° C. or higher, and 2300 ° C. or lower, preferably 2000 ° C. or lower, more preferably 1800. ° C or lower, more preferably 1600 ° C or lower, particularly preferably 1500 ° C or lower. By firing at a firing temperature in this range, it is possible to reduce the initial irreversible capacity, increase the charge / discharge capacity, reduce the negative electrode charge transfer resistance (R _CT ), and improve the input / output characteristics.
The firing time is not particularly limited, but is usually 0.1 hours or more, preferably 0.5 hours or more, more preferably 1 hour or more, particularly preferably 3 hours or more, usually 1000 hours or less, preferably 100 hours or less, more preferably Is 50 hours or less, particularly preferably 24 hours or less.

<Crushing process>
The pulverization step is a step of pulverizing and classifying the fired product obtained in the firing step as necessary. In the pulverization step, the average particle size (d50) of the pulverized product is usually 5 μm or more, preferably 8 μm or more, more preferably 10 μm or more, and the upper limit is 35 μm or less, preferably 30 μm or less, more preferably 27 μm or less. The ratio of the raw carbon material to d50 (d50_r = d50 of pulverized particles / d50 of the carbon material) is usually 0.8 or higher, preferably 0.85 or higher, more preferably 0.9 or higher, still more preferably 0.8. 93 or more, particularly preferably 0.95 or more, usually 1.2 or less, preferably 1.15 or less, more preferably 1.1 or less, particularly preferably 1.05 or less, and most preferably 1.02 or less. By performing pulverization and classification, the negative electrode material of the present invention can be obtained. When d50_r is less than 0.8, the irreversible capacity is increased, and when d50_r is more than 1.2, the negative charge transfer resistance (R _CT ) is increased and the input / output characteristics are decreased.
By appropriately performing the pulverization treatment of the negative electrode material of the present invention, the surface of the negative electrode material is covered by chemical vapor deposition (CVD) of volatile components (VM) generated from carbonaceous particles and organic compounds. Since the carbon layer containing only the carbon component is appropriately roughened and the carbon layer containing the group 13 element component of the periodic table can be appropriately exposed on the surface of the negative electrode material, the negative electrode charge transfer resistance (R _CT ) is reduced, and the input / output There is a tendency to improve characteristics.

The apparatus used for crushing is not particularly limited, and examples thereof include a rolling ball mill, a planetary ball mill, a hammer mill, a CF mill, an atomizer mill, a pulverizer, a mechanofusion, a hybridization, a theta composer, an ang mill, and a turbo mill.
Classification is not particularly limited, and can be performed by a known method such as using a sieve.

<Physical properties of negative electrode material>
The fired product or the pulverized product obtained through the above steps becomes a multi-layer structure carbon material in which a carbon material is coated with a carbonaceous material derived from a residual carbon content of a periodic table group 13 element-containing compound and an organic compound. That is, particles having a structure in which the outside of a carbon material with high crystallinity is coated with amorphous carbon with low crystallinity is used as a negative electrode material for a nonaqueous electrolyte secondary battery (hereinafter referred to as negative electrode material). be able to. The negative electrode material in the present invention preferably has the following physical properties. In addition, although the measuring method of the physical property of the carbon material in this invention does not have a restriction | limiting in particular, unless there is a special situation, it will follow the measuring method as described in an Example.

(1) Surface Periodic Table Group 13 Element Amount of Negative Electrode Material (Surface Oxygen Element Amount X ₁₃ / C)
In the negative electrode material, the surface element amount X ₁₃ / C value represented by the following (formula 2) of Group 13 element of the periodic table is usually preferably 0.7% or more and 0.8% or more, more preferably 1% or more. Preferably, usually 4.5% or less, 4% or less is preferable, 3.5% or less is more preferable, and 3% or less is more preferable.
(Formula 2)
Surface element amount X ₁₃ / C value (%) of group 13 element of periodic table = determined based on peak area of spectrum of outermost electron orbit of group 13 element of periodic table in X-ray photoelectron spectroscopy (XPS) analysis Periodic table group 13 element concentration / C atom concentration obtained based on peak area of C1s spectrum in XPS analysis × 100

If the surface element amount (X ₁₃ / C value) of the group 13 element of the periodic table of the negative electrode material is too small, the negative electrode resistance reduction effect and the input / output characteristic improvement effect tend to decrease, while the surface element amount is large. If it is too high, the battery capacity tends to decrease and the electrode plate strength tends to decrease.

The amount of surface elements can be measured using X-ray photoelectron spectroscopy (XPS).
The amount of surface element (X ₁₃ / C value) was measured using an X-ray photoelectron spectrometer as an X-ray photoelectron spectroscopy measurement, the measurement object was placed on a sample stage so that the surface was flat, and aluminum Kα rays were used as an X-ray source. And the spectrum of C1s (280 to 300 eV) and a periodic table group 13 element-containing compound (180 to 210 eV for boron (B1s) and 70 eV to 80 eV for aluminum (2p)) by multiplex measurement. To do. The obtained C1s peak top is 284.3 eV to correct the charge, the peak areas of the C1s and X ₁₃ spectra are obtained, and the device sensitivity coefficient is multiplied to calculate the surface atomic concentrations of C and X, respectively. The obtained X ₁₃ and C atomic concentration ratio X ₁₃ / C (X atomic concentration / C atomic concentration) is defined as the surface element amount X ₁₃ / C value of the group 13 element-containing compound on the surface.

(2) Periodic table group 13 element abundance ratio in the surface of the negative electrode material and in the bulk The negative electrode material usually has an abundance ratio of the group 13 element in the periodic table in the surface represented by the following (formula 3) 2 or more, preferably 2.5 or more, more preferably 3 or more, still more preferably 5 or more, and particularly preferably 8 or more. Moreover, it is 15 or less normally, Preferably it is 12 or less, More preferably, it is 10 or less. If the surface abundance ratio is too small, the negative electrode resistance reduction effect and the input / output characteristic improvement effect tend to be reduced.
(Formula 3)
Surface abundance ratio = surface element amount X ₁₃ / C value (%) of group 13 element of periodic table represented by (formula 2) / periodic table 13 obtained from inductively coupled plasma mass spectrometry (ICP-MS) analysis Group element content in bulk (% by mass)

The bulk content of the Group 13 element in the periodic table can be measured using inductively coupled plasma mass spectrometry (ICP-MS).
Specifically, as an inductively coupled plasma mass spectrometry method, an inductively coupled plasma mass spectrometer is used, a sample to be measured is collected in a decomposition container, a decomposition reagent is added, and wet decomposition is performed using a microwave heating closed decomposition apparatus, Diluted with ion-exchanged water, inductively coupled plasma mass spectrometer (ICP-M
In S), the periodic table group 13 element amount X ₁₃ , carbon amount C, and oxygen amount O are quantified. The boron content ratio (X ₁₃ / X ₁₃ + C + O × 100) obtained here is defined as the bulk content (mass%) of Group 13 elements in the periodic table.
The value calculated by using the above (formula 3) from the bulk content (mass%) of the Group 13 element in the periodic table and the surface element amount X ₁₃ / C value described above is defined as the surface abundance ratio.

(3) Surface functional group amount of negative electrode material (surface oxygen element amount O / C)
The negative electrode material has a functional group amount (surface oxygen element amount O / C value) represented by the above (formula 1) of usually 1% or more, preferably 2% or more, more preferably 2.6% or more, even more preferably. Is 3.2% or more, particularly preferably 3.6% or more, and most preferably 3.9% or more. Moreover, it is 30% or less normally, Preferably it is 20% or less, More preferably, it is 15% or less. If this surface functional group amount O / C value is too small, the desolvation reactivity of Li ions and the electrolyte solvent on the negative electrode active material surface may be lowered, and the charge / discharge inability characteristic may be lowered. There is a possibility that the reactivity with the electrolytic solution increases, leading to a decrease in charge / discharge efficiency and an increase in gas generation.

(4) BET specific surface area (SA) of negative electrode material
The negative electrode material has a specific surface area measured by the BET method of usually 0.5 m ² / g or more, preferably 1 m ² / g or more. Moreover, it is 8 m < ² > / g or less normally, Preferably it is 7 m < ² > / g or less, More preferably, it is 6 m < ² > / g or less.
If the specific surface area is too small, there are few sites where Li enters and exits, and the high-speed charge / discharge characteristic output characteristics are inferior. On the other hand, if the specific surface area is too large, the activity of the active material with respect to the electrolyte becomes excessive and the initial irreversible capacity is large. Therefore, there is a possibility that a high capacity battery cannot be manufactured.
In addition, the measuring method of a BET specific surface area is measured by a BET 1 point method by a nitrogen gas adsorption circulation method using a specific surface area measuring device.

(5) Tap density of negative electrode material The tap density of the negative electrode material is usually usually 0.4 g / cm ³ or more, preferably 0.6 g / cm ³ or more, more preferably 0.85 g / cm ³ or more, and 1 g / cm ³ or more. Is more preferably 1.1 g / cm ³ or more, and usually 1.6 g / cm ³ or less, preferably 1.3 g / cm ³ or less. If the tap density is too low, the high-speed charge / discharge characteristics are inferior. If the tap density is too high, the carbon density in the particles increases, the rolling property is insufficient, and it is difficult to form a high-density negative electrode sheet.
The tap density was measured by using a powder density measuring device to drop the negative electrode material through a sieve having a diameter of 1.6 cm and a volume capacity of 20 cm ³ through a sieve having an opening of 300 μm to fill the cell. A tap having a stroke length of 10 mm is performed 1000 times, and the density obtained from the volume and the weight of the sample is defined as the tap density.

(6) Raman R value of Raman spectrum (Raman) spectrum negative electrode material of the negative electrode material was 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 The intensity ratio R (R = I _B / I _A ) is calculated and defined. The value is not particularly limited, but is usually 0.01 or more, preferably 0.05 or more, more preferably 0.2 or more. Moreover, it is 1 or less normally, Preferably it is 0.5 or less. If the Raman R value is too small, the crystallinity of the particle surface becomes too high, and when the density is increased, the crystals tend to be oriented in a direction parallel to the electrode plate, and the load characteristics tend to be lowered. On the other hand, if the Raman R value is too large, the crystal on the particle surface is disturbed, the reactivity with the electrolytic solution increases, and the charge / discharge efficiency tends to decrease and the gas generation tends to increase.
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 rotated in a plane perpendicular to the laser beam while irradiating the measurement cell with an argon ion laser beam. Measure.
Argon ion laser light wavelength: 514.5 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)

<Negative electrode for non-aqueous electrolyte secondary battery>
The negative electrode for a non-aqueous electrolyte secondary battery is formed by dispersing the produced negative electrode material (negative electrode active material) and a binder in a dispersion medium to form a slurry, which is applied to a current collector. As the dispersion medium, an organic solvent such as alcohol or water can be used. If necessary, a conductive agent may be added to the slurry. Examples of the conductive agent include carbon black such as acetylene black, ketjen black, and furnace black, and fine powder made of Cu, Ni having an average particle diameter of 1 μm or less, or an alloy thereof. The addition amount of the conductive agent is usually about 10% by mass or less with respect to the negative electrode material of the present invention.

The binder for binding the negative electrode active material is not particularly limited as long as it is a material that is stable with respect to the non-aqueous electrolyte solution and the solvent used in manufacturing the electrode.
Specific examples include resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, polyimide, cellulose, and nitrocellulose; SBR (styrene-butadiene rubber), isoprene rubber, butadiene rubber, fluorine rubber, Rubber polymers such as NBR (acrylonitrile / butadiene rubber) and ethylene / propylene rubber; styrene / butadiene / styrene block copolymer or hydrogenated product thereof; EPDM (ethylene / propylene / diene terpolymer), styrene / Thermoplastic elastomeric polymers such as ethylene / butadiene / styrene copolymers, styrene / isoprene / styrene block copolymers or hydrogenated products thereof; syndiotactic-1,2-polybutadiene, polyvinyl acetate , Soft resinous polymers such as ethylene / vinyl acetate copolymer, propylene / α-olefin copolymer; polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene / ethylene copolymer, etc. And a polymer composition having ion conductivity of alkali metal ions (particularly lithium ions). These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and ratios.

  The ratio of the binder to the negative electrode active material is usually preferably 0.05% by mass or more, preferably 0.1% by mass or more, more preferably 0.5% by mass or more, particularly preferably 0.6% by mass or more, and usually 20%. It is preferably at most 15 mass%, more preferably at most 12 mass%, further preferably at most 10 mass%, particularly preferably at most 8 mass%. When the ratio of the binder to the negative electrode active material is too large, the binder ratio in which the binder amount does not contribute to the battery capacity increases, and the battery capacity tends to decrease. Moreover, when there are too few ratios of a binder, there exists a tendency for the strength fall of a negative electrode to be caused.

  In particular, when a rubbery polymer typified by SBR is contained as a main component, the ratio of the binder to the negative electrode active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, and 0 .6% by mass or more is more preferable, and is usually 5% by mass or less, preferably 3% by mass or less, and more preferably 2% by mass or less. When the main component contains a fluorine-based polymer typified by polyvinylidene fluoride, the ratio to the negative electrode active material is usually 1% by mass or more, preferably 2% by mass or more, and more preferably 3% by mass or more. It is preferably 15% by mass or less, preferably 10% by mass or less, and more preferably 8% by mass or less.

The solvent for forming the slurry is not particularly limited as long as it is a solvent capable of dissolving or dispersing the negative electrode active material, the binder, and the thickener and conductive material used as necessary. Alternatively, either an aqueous solvent or an organic solvent may be used.
Examples of the aqueous solvent include water and alcohol. Examples of the organic solvent include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N, N- Examples include dimethylaminopropylamine, tetrahydrofuran (THF), toluene, acetone, diethyl ether, dimethylacetamide, hexamethylphosphalamide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane, and the like.
In particular, when an aqueous solvent is used, it is preferable to add a dispersant or the like in addition to the thickener and slurry it using a latex such as SBR. In addition, these solvents may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and a ratio.

  A thickener is usually used to adjust the viscosity of the slurry. The thickener is not particularly limited, and specific examples include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and ratios.

  Further, when using a thickener, the ratio of the thickener to the negative electrode active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, Moreover, it is 5 mass% or less normally, 3 mass% or less is preferable, and 2 mass% or less is more preferable. When the proportion of the thickener is too large, the proportion of the negative electrode active material in the negative electrode active material layer decreases, and there is a tendency for the battery capacity to decrease and the resistance between the negative electrode active materials to increase.

The electrode structure when the negative electrode active material is made into an electrode is not particularly limited, but the density of the negative electrode active material present on the current collector is usually 1 g · cm ⁻³ or more and 1.2 g · cm ⁻³ or more. preferably, 1.3 g · cm ^-3 or more, and also, usually 2.2 g · cm ^-3 or less, preferably 2.1 g · cm ^-3 or less, more preferably 2.0 g · cm ^-3 or less, 1 More preferably, it is not more than .9 g · cm ⁻³ . If the density of the negative electrode active material present on the current collector is too large, the negative electrode active material particles will be destroyed, increasing the initial irreversible capacity, and the non-aqueous electrolyte solution near the current collector / negative electrode active material interface. There is a tendency for high current density charge / discharge characteristics to deteriorate due to a decrease in permeability. On the other hand, if the density is too small, the conductivity between the negative electrode active materials decreases, the battery resistance increases, and the capacity per unit volume tends to decrease.

  The thickness of the negative electrode plate is designed according to the positive electrode plate to be used, and is not particularly limited. However, the thickness of the composite layer obtained by subtracting the thickness of the metal foil of the core is usually 15 μm or more, preferably 20 μm or more. More preferably, it is 30 μm or more, and usually 300 μm or less, preferably 280 μm or less, more preferably 250 μm or less.

  Moreover, you may use what adhered the substance of the composition different from this to the surface of the said negative electrode plate. Surface adhering substances include aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate And sulfates such as aluminum sulfate and carbonates such as lithium carbonate, calcium carbonate and magnesium carbonate.

<Nonaqueous electrolyte secondary battery>
The basic configuration of the non-aqueous electrolyte secondary battery of the present invention, particularly the lithium ion secondary battery, is the same as that of a conventionally known lithium ion secondary battery, and usually a positive electrode and a negative electrode capable of inserting and extracting lithium ions, As well as an electrolyte. The negative electrode of the present invention described above is used as the negative electrode.

<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.
-Positive electrode active material The positive electrode active material (lithium transition metal type compound) used for the positive electrode is described below.

-Lithium transition metal compound A lithium transition metal compound is a compound having a structure capable of desorbing and inserting Li ions, such as sulfides, phosphate compounds, lithium transition metal composite oxides, etc. Is mentioned. Examples of sulfides include compounds having a two-dimensional layered structure such as TiS ₂ and MoS ₂ , and solid compounds represented by the general formula Me _x Mo ₆ S ₈ (Me is various transition metals including Pb, Ag, and Cu). Examples thereof include a sugar compound having a three-dimensional skeleton structure. Examples of the phosphate compound include those belonging to the olivine structure, and are generally represented by LiMePO ₄ (Me is at least one or more transition metals), specifically LiFePO ₄ , LiCoPO ₄ , LiNiPO ₄ , Examples thereof include LiMnPO ₄ . Examples of the lithium transition metal composite oxide include spinel structures capable of three-dimensional diffusion and those belonging to a layered structure capable of two-dimensional diffusion of lithium ions. Those having a spinel structure are generally expressed as LiMe ₂ O ₄ (Me is at least one or more transition metals), specifically, LiMn ₂ O ₄ , LiCoMnO ₄ , LiNi _0.5 Mn _1.5 O ₄ , LiCoVO _4. Etc. Those having a layered structure are generally expressed as LiMeO ₂ (Me is at least one transition metal). LiCoO _{2 Specifically, LiNiO 2, LiNi 1-x} Co x O 2, LiNi 1-xy Co x Mn y O 2,
LiNi _0.5 Mn _0.5 O ₂ , Li _1.2 Cr _0.4 Mn _0.4 O ₂ , Li _1.2 Cr _0.4 Ti _0.4 O ₂ , Li
Examples thereof include MnO ₂ .

Composition The lithium-containing transition metal compound is, for example, a lithium transition metal compound represented by the following composition formula (A) or (B).
1) In the case of a lithium transition metal compound represented by the following composition formula (A)
Li _{1 + x} MO ₂ (A)
However, x is usually 0 or more and 0.5 or less. M is an element composed of Ni and Mn or Ni, Mn and Co, and the Mn / Ni molar ratio is usually 0.1 or more and 5 or less. The Ni / M molar ratio is usually 0 or more and 0.5 or less. The Co / M molar ratio is usually 0 or more and 0.5 or less. In addition, the rich portion of Li represented by x may be replaced with the transition metal site M.

In the composition formula (A), the atomic ratio of the oxygen amount is described as 2 for convenience, but there may be some non-stoichiometry. Moreover, x in the said compositional formula is the preparation composition in the manufacture stage of a lithium transition metal type compound. Usually, batteries on the market are aged after the batteries are assembled. For this reason, the Li amount of the positive electrode may be deficient with charge / discharge. In this case, x may be measured to be −0.65 or more and 1 or less when discharged to 3 V in composition analysis.
A lithium transition metal-based compound is excellent in battery characteristics when fired at a high temperature in an oxygen-containing gas atmosphere in order to enhance the crystallinity of the positive electrode active material.
Further, the lithium transition metal-based compound represented by the composition formula (A) may be a solid solution with Li ₂ MO ₃ called a 213 layer, as shown in the general formula (A ′) below.
αLi ₂ MO ₃ · (1-α) LiM′O ₂ (A ′)
In the general formula, α is a number satisfying 0 <α <1.
M is at least one metal element having an average oxidation number of 4 ⁺ , specifically, Mn,
It is at least one metal element selected from the group consisting of Zr, Ti, Ru, Re and Pt.
M ′ is at least one metal element having an average oxidation number of 3 ⁺ , preferably at least one metal element selected from the group consisting of V, Mn, Fe, Co and Ni, more preferably , At least one metal element selected from the group consisting of Mn, Co and Ni.

2) A lithium transition metal compound represented by the following general formula (B).
Li [Li _a M _b Mn _2-ba ] O _{4 + δ} (B)
However, M is an element comprised from at least 1 sort (s) of the transition metals chosen from Ni, Cr, Fe, Co, Cu, Zr, Al, and Mg.
The value of b is usually 0.4 or more and 0.6 or less.
When the value of b is within this range, the energy density per unit weight in the lithium transition metal compound is high.
The value of a is usually 0 or more and 0.3 or less. Moreover, a in the above composition formula is a charged composition in the production stage of the lithium transition metal compound. Usually, batteries on the market are aged after the batteries are assembled. For this reason, the Li amount of the positive electrode may be deficient with charge / discharge. In this case, a may be measured to be −0.65 or more and 1 or less when discharged to 3 V in composition analysis.
When the value of a is within this range, the energy density per unit weight in the lithium transition metal compound is not significantly impaired, and good load characteristics can be obtained.
Furthermore, the value of δ is usually in the range of ± 0.5.
If the value of δ is within this range, the stability as a crystal structure is high, and the cycle characteristics and high-temperature storage of a battery having an electrode produced using this lithium transition metal compound are good.

Here, the chemical meaning of the lithium composition in the lithium nickel manganese composite oxide, which is the composition of the lithium transition metal compound, will be described in more detail below.
In order to obtain a and b in the composition formula of the lithium transition metal compound, each transition metal and lithium are analyzed with an inductively coupled plasma emission spectrometer (ICP-AES) to obtain a ratio of Li / Ni / Mn. It is calculated by the thing.
From a structural point of view, it is considered that lithium related to a is substituted for the same transition metal site. Here, due to the lithium according to a, the average valence of M and manganese becomes larger than 3.5 due to the principle of charge neutrality.
The lithium transition metal-based compound may be substituted with fluorine and is expressed as LiMn ₂ O _{4 -x} F _2x .

Blend As specific examples of the lithium transition metal-based compound having the above composition, for example, Li _{1 + x} Ni _0.5 Mn _0.5 O ₂ , Li _{1 + x} Ni _0.85 Co _0.10 Al _0.05 O ₂ , Li _{1 + x} Ni _0.33 Mn _0.33 Co _0.33 O ₂ , Li _{1 + x} Ni _0.45 Mn _0.45 Co _0.1 O ₂ , Li _{1 + x} Mn _1.8 Al _0.2 O ₄ , Li _{1 + x} Mn _1.5 N
i _0.5 O _{4 and the} like. These lithium transition metal compounds may be used alone or in a blend of two or more.

-Introduction of foreign elements In addition, foreign elements may be introduced into the lithium transition metal compound. As a foreign element, B
, Na, Mg, Al, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Ru, Rh, Pd, Ag, In, Sb, Te, Ba, Ta, Mo , W, Re, Os, Ir, Pt, Au, Pb, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Bi, N, F, S , Cl, Br, I, As, Ge, P, Pb, Sb, Si, and Sn. These foreign elements may be incorporated into the crystal structure of the lithium transition metal compound, or may not be incorporated into the crystal structure of the lithium transition metal compound, and may be a single element or compound on the particle surface or grain boundary. May be unevenly distributed.

<Positive electrode for lithium secondary battery>
The positive electrode for a lithium secondary battery is formed by forming a positive electrode active material layer containing the above-described lithium transition metal compound powder for a lithium secondary battery positive electrode material and a binder on a current collector.
The positive electrode active material layer is usually formed by mixing a positive electrode material, a binder, and a conductive material and a thickener, which are used if necessary, in a dry form into a sheet shape, and then pressing the positive electrode current collector on the positive electrode current collector. Alternatively, these materials are dissolved or dispersed in a liquid medium to form a slurry, which is applied to the positive electrode current collector and dried.

  As the material for the positive electrode current collector, metal materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum, and carbon materials such as carbon cloth and carbon paper are usually used. As for the shape, in the case of a metal material, a metal foil, a metal cylinder, a metal coil, a metal plate, a metal thin film, an expanded metal, a punch metal, a foam metal, etc., and in the case of a carbon material, a carbon plate, a carbon thin film, a carbon cylinder Etc. In addition, you may form a thin film suitably in mesh shape.

  When a thin film is used as the positive electrode current collector, its thickness is arbitrary, but a range of usually 1 μm or more and 100 mm or less is suitable. If it is thinner than the above range, the strength required for the current collector may be insufficient. On the other hand, if it is thicker than the above range, the handleability may be impaired.

  The binder used in the production of the positive electrode active material layer is not particularly limited, and in the case of a coating method, any material that is stable with respect to the liquid medium used during electrode production may be used. Specific examples include polyethylene, Resin polymers such as polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, cellulose, nitrocellulose, SBR (styrene butadiene rubber), NBR (acrylonitrile butadiene rubber), fluorine rubber, isoprene rubber, butadiene rubber, ethylene・ Rubber polymers such as propylene rubber, styrene / butadiene / styrene block copolymers and hydrogenated products thereof, EPDM (ethylene / propylene / diene terpolymers), styrene / ethylene / butadiene / ethylene copolymers, Styrene / isoprene styrene bromide Copolymer and its hydrogenated thermoplastic elastomeric polymer, syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene / vinyl acetate copolymer, propylene / α-olefin copolymer, etc. Fluorine polymers such as soft resinous polymers, polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene / ethylene copolymers, ion conductivity of alkali metal ions (especially lithium ions) And a polymer composition having the same. In addition, these substances may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.

  The ratio of the binder in the positive electrode active material layer is usually 0.1% by mass or more and 80% by mass or less. If the proportion of the binder is too low, the positive electrode active material cannot be sufficiently retained and the positive electrode has insufficient mechanical strength, which may deteriorate battery performance such as cycle characteristics. Battery capacity and conductivity may be reduced.

  The positive electrode active material layer usually contains a conductive material in order to increase conductivity. There are no particular restrictions on the type, but specific examples include metal materials such as copper and nickel, graphite such as natural graphite and artificial graphite, carbon black such as acetylene black, and amorphous carbon such as needle coke. And carbon materials. In addition, these substances may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios. The proportion of the conductive material in the positive electrode active material layer is usually 0.01% by mass or more and 50% by mass or less. If the proportion of the conductive material is too low, the conductivity may be insufficient, and conversely if it is too high, the battery capacity may be reduced.

  As a liquid medium for forming a slurry, it is possible to dissolve or disperse a lithium transition metal compound powder as a positive electrode material, a binder, and a conductive material and a thickener used as necessary. If it is a solvent, there is no restriction | limiting in particular in the kind, You may use either an aqueous solvent or an organic solvent. Examples of the aqueous solvent include water and alcohol. Examples of the organic solvent include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N , N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran (THF), toluene, acetone, dimethyl ether, dimethylacetamide, hexamethylphosphalamide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane, etc. be able to. In particular, when an aqueous solvent is used, a dispersant is added together with the thickener, and a slurry such as SBR is slurried. In addition, these solvents may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

The content ratio of the lithium transition metal-based compound powder as the positive electrode material in the positive electrode active material layer is usually 10% by mass or more and 99.9% by mass or less. If the proportion of the lithium transition metal compound powder in the positive electrode active material layer is too large, the strength of the positive electrode tends to be insufficient, and if it is too small, the capacity may be insufficient.
The thickness of the positive electrode active material layer is usually about 10 to 200 μm.
The electrode density after pressing the positive electrode is usually 2.2 g / cm ³ or more and 4.2 g / cm ³ or less.
The positive electrode active material layer obtained by coating and drying is preferably consolidated by a roller press or the like in order to increase the packing density of the positive electrode active material.
Thus, a positive electrode for a lithium secondary battery can be prepared.

<Nonaqueous electrolyte>
As the non-aqueous electrolyte, for example, known non-aqueous electrolytes, polymer solid electrolytes, gel electrolytes, inorganic solid electrolytes, and the like can be used. Of these, non-aqueous electrolytes are preferable. The non-aqueous electrolyte solution is configured by dissolving a solute (electrolyte) in a non-aqueous solvent.

<Electrolyte>
There is no restriction | limiting in the electrolyte used for a non-aqueous electrolyte solution, The well-known thing used as an electrolyte can be employ | adopted arbitrarily and can be contained. When the non-aqueous electrolyte solution of the present invention is used in a non-aqueous electrolyte secondary battery, 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 ,
Examples thereof include lithium bis (oxalato) borate, lithium difluorooxalatoborate, lithium tetrafluorooxalatophosphate, lithium difluorobis (oxalato) phosphate, and lithium fluorosulfonate. 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 electrolytic solution is arbitrary, but 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 Is in the range of 2 mol / L or less, more preferably 1.5 mol / L or less. When the total molar concentration of lithium is within the above range, the electric conductivity of the electrolytic solution is sufficient, and on the other hand, it is possible to prevent a decrease in electric conductivity and a decrease in battery performance due to an increase in viscosity.

<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 dimethyl Carbonates, chain carbonates such as ethyl methyl carbonate and diethyl carbonate, cyclic carbonates such as ethylene carbonate, propylene carbonate and butylene carbonate, chain carboxylates such as methyl acetate, ethyl acetate, methyl propionate and ethyl propionate, γ- Cyclic carboxylic acid esters such as butyrolactone, chain ethers such as dimethoxyethane and diethoxyethane, cyclic ethers such as tetrahydrofuran, 2-methyltetrahydrofuran and tetrahydropyran, acetonitrile, propionitrile, benzonitrile, Examples include nitriles such as tyronitrile and valeronitrile, phosphate esters such as trimethyl phosphate and triethyl phosphate, sulfur-containing compounds such as ethylene sulfite, 1,3-propane sultone, methyl methanesulfonate, sulfolane, and dimethyl sulfone. In these compounds, hydrogen atoms may be partially substituted with halogen atoms. These may be used alone or in combination of two or more, but it is preferable to use two or more compounds in combination. 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.

  Here, the high dielectric constant solvent means a compound having a relative dielectric constant of 20 or more at 25 ° C. Among the high dielectric constant solvents, it is preferable that ethylene carbonate, propylene carbonate, and compounds in which hydrogen atoms thereof are substituted with other elements such as halogen or alkyl groups are contained in the electrolytic solution. The proportion of the high dielectric constant solvent in the electrolytic solution is preferably 15% by mass or more, more preferably 20% by mass or more, and most preferably 25% by mass or more. If the content of the high dielectric constant solvent is less than the above range, desired battery characteristics may not be obtained.

<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. As an auxiliary agent that has the effect of improving the battery life in order to form a film on the negative electrode surface, unsaturated cyclic carbonates such as vinylene carbonate, vinyl ethylene carbonate, and ethynyl ethylene carbonate, and cyclic compounds having fluorine atoms such as fluoroethylene carbonate Examples thereof include fluorinated unsaturated cyclic carbonates such as carbonate and 4-fluorovinylene carbonate. Biphenyl, cyclohexylbenzene, diphenyl ether, t-butylbenzene, t-pentylbenzene, diphenyl carbonate, methyl as an overcharge inhibitor that effectively suppresses battery explosion and ignition when the battery is overcharged. Examples include aromatic compounds such as phenyl carbonate. As auxiliary agents to improve cycle characteristics and low-temperature discharge characteristics, lithium monofluorophosphate, lithium difluorophosphate, lithium fluorosulfonate, lithium bis (oxalato) borate, lithium difluorooxalatoborate, lithium tetrafluorooxalatophosphate, lithium Examples thereof include lithium salts such as difluorobis (oxalato) phosphate. As auxiliary agents that can improve capacity maintenance characteristics and cycle characteristics after high-temperature storage, sulfur-containing compounds such as ethylene sulfite, propane sultone, propene sultone, carboxylic acids such as succinic anhydride, maleic anhydride, and citraconic anhydride Examples include nitrile compounds such as anhydride, succinonitrile, glutaronitrile, adiponitrile, and pimelonitrile. The amount of these auxiliaries is not particularly limited, and is arbitrary as long as the effects of the present invention are not significantly impaired.

<Separator>
Usually, a separator is interposed between the positive electrode and the negative electrode in order to prevent a short circuit. In this case, the nonaqueous electrolytic solution of the present invention 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 them, a resin, glass fiber, inorganic material, etc. formed of a material that is stable with respect to the non-aqueous electrolyte solution of the present invention is used, and a porous sheet or a nonwoven fabric-like material having excellent liquid retention properties is used. Is preferred.

  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. Of these, glass filters and polyolefins are preferred, and polyolefins are more preferred. 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 the battery performance such as the rate characteristic may be lowered, but also the energy density of the whole non-aqueous electrolyte secondary battery may be lowered.

Furthermore, when using a porous material such as a porous sheet or nonwoven fabric as the separator, the porosity of the separator is arbitrary, but is usually 20% or more, preferably 35% or more, more preferably 45% or more, Further, it is usually 90% or less, preferably 85% or less, and more preferably 75% or less. If the porosity is too smaller than the above range, the membrane resistance tends to increase and the rate characteristics tend to deteriorate. Moreover, when larger than the said range, it exists in the tendency for the mechanical strength of a separator to fall and for insulation to fall.
Moreover, although the average pore diameter of a separator is also arbitrary, it is 0.5 micrometer or less normally, 0.2 micrometer or less is preferable, and it is 0.05 micrometer or more normally. If the average pore diameter exceeds the above range, a short circuit tends to occur. On the other hand, below the above range, the film resistance may increase and the rate characteristics may deteriorate.

On the other hand, as inorganic materials, 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.
As the form, a thin film shape such as a non-woven fabric, a woven fabric, or a microporous film is used. In the thin film shape, those having a pore diameter of 0.01 to 1 μm and a thickness of 5 to 50 μm are preferably used. In addition to the above-described independent thin film shape, a separator formed by forming a composite porous layer containing the inorganic particles on the surface layer of the positive electrode and / or the negative electrode using a resin binder can be used. For example, a porous layer may be formed by using alumina particles having a 90% particle size of less than 1 μm on both surfaces of the positive electrode and using a fluororesin as a binder.

  The characteristics of the separator in the non-electrolyte secondary battery can be grasped by the Gurley value. The Gurley value indicates the difficulty of air passage in the film thickness direction, and is expressed as the number of seconds required for 100 ml of air to pass through the film. It means that it is harder to go through. That is, a smaller value means better communication in the thickness direction of the film, and a larger value means lower communication in the thickness direction of the film. Communication is the degree of connection of holes in the film thickness direction. If the Gurley value of the separator of the present invention is low, it can be used for various purposes. For example, when used as a separator for a non-aqueous lithium secondary battery, a low Gurley value means that lithium ions can be easily transferred and is preferable because of excellent battery performance. Although the Gurley value of a separator is arbitrary, Preferably it is 10-1000 second / 100ml, More preferably, it is 15-800 second / 100ml, More preferably, it is 20-500 second / 100ml. If the Gurley value is 1000 seconds / 100 ml or less, the electrical resistance is substantially low, which is preferable as a separator.

<Battery design>
-Electrode group The electrode group has a laminated structure in which the positive electrode plate and the negative electrode plate are interposed via the separator, and the positive electrode plate and the negative electrode plate are spirally wound via the separator. Any of the structures may be used. The ratio of the volume of the electrode group to the internal volume of the battery (hereinafter referred to as the electrode group occupation ratio) is usually 40% or more, preferably 50% or more, and usually 90% or less, preferably 80% or less. .

  When the electrode group occupancy is below the above range, the battery capacity decreases. Also, if the above range is exceeded, the void space is small, the battery expands, and the member expands or the vapor pressure of the electrolyte liquid component increases and the internal pressure rises. In some cases, the gas release valve that lowers various characteristics such as storage at high temperature and the like, or releases the internal pressure to the outside is activated.

<Exterior case>
The material of the outer case is not particularly limited as long as it is a substance that is stable with respect to the non-aqueous electrolyte used. Specifically, a nickel-plated steel plate, stainless steel, aluminum, an aluminum alloy, a metal such as a magnesium alloy, or a laminated film (laminate film) of a resin and an aluminum foil is used. From the viewpoint of weight reduction, an aluminum or aluminum alloy metal or a laminate film is preferably used.

  In an exterior case using metals, the metal is welded to each other by laser welding, resistance welding, or ultrasonic welding to form a sealed sealed structure, or a caulking structure using the above metals via a resin gasket. Things. Examples of the outer case using the laminate film include a case where a resin-sealed structure is formed by heat-sealing resin layers. In order to improve sealing performance, a resin different from the resin used for the laminate film may be interposed between the resin layers. In particular, when a resin layer is heat-sealed through a current collecting terminal to form a sealed structure, a metal and a resin are joined, so that a resin having a polar group or a modified group having a polar group introduced as an intervening resin is used. Resins are preferably used.

<Protective element>
Protection elements such as PTC (Positive Temperature Coefficient), thermal fuse, thermistor, which increases resistance when abnormal heat is generated or excessive current flows, shuts off current flowing through the circuit due to sudden increase in battery internal pressure or internal temperature during abnormal heat generation A valve (current cutoff valve) or the like can be used. It is preferable to select a protective element that does not operate under normal use at a high current, and it is more preferable that the protective element is designed so as not to cause abnormal heat generation or thermal runaway even without the protective element.

<Exterior body>
The non-aqueous electrolyte secondary battery of the present invention is usually configured by housing the non-aqueous electrolyte, the negative electrode, the positive electrode, the separator, and the like in an exterior body. This exterior body is not particularly limited, and any known one can be arbitrarily adopted as long as the effects of the present invention are not significantly impaired. Specifically, the material of the exterior body is arbitrary, but usually, for example, nickel-plated iron, stainless steel, aluminum or an alloy thereof, nickel, titanium, or the like is used.
The shape of the exterior body is also arbitrary, and may be any of a cylindrical shape, a square shape, a laminate shape, a coin shape, a large size, and the like.

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.
(Measuring method)
(1) Analysis method of group 13 element of periodic table contained in negative electrode material of present invention <surface element amount of group 13 element of periodic table>
The amount of surface elements of Group 13 elements of the periodic table is measured using X-ray photoelectron spectroscopy (XPS).
The amount of surface elements of the Group 13 element of the periodic table was measured using an X-ray photoelectron spectrometer (ESCA manufactured by ULVAC-PHI) as an X-ray photoelectron spectroscopy measurement, and the measurement target (a negative electrode sheet produced using a negative electrode material). The sample was placed on a sample stage, and the Kα ray of aluminum was used as an X-ray source. By multiplex measurement, C1s (280 to 300 eV) and a group 13 element-containing compound of the periodic table (180 to 210 eV in the case of boron (B1s)), aluminum (2p ), A spectrum of 70 eV to 80 eV) is measured. The obtained C1s peak top is corrected to be 284.3 eV, the peak areas of the C1s and X ₁₃ spectra are obtained, and the device sensitivity coefficient is multiplied to calculate the surface atomic concentrations of C and X ₁₃ , respectively. As shown in Equation 2, the surface elements of the obtained that X ₁₃ and C atomic concentration ratio X ₁₃ / C (X atom concentration / C atom concentration) a Group 13 element-containing compounds periodic table in the surface X ₁₃ / Defined as C value.
(Formula 2)
Surface element amount X ₁₃ / C value (%) of group 13 element of periodic table = determined based on peak area of spectrum of outermost electron orbit of group 13 element of periodic table in X-ray photoelectron spectroscopy (XPS) analysis Periodic table group 13 element concentration / C atom concentration obtained based on peak area of C1s spectrum in XPS analysis × 100

<Bulk content of group 13 element of periodic table>
The bulk content of the Group 13 element of the periodic table can be measured using inductively coupled plasma mass spectrometry (ICP-MS).
Specifically, as an inductively coupled plasma mass spectrometer, an inductively coupled plasma mass spectrometer is used, and a sample to be measured prepared by peeling an active material layer from a negative electrode plate produced using the negative electrode material of the present invention is decomposed into a decomposition container. taken, the decomposition reagent was added, and wet digestion using microwave heating a sealed decomposition apparatus, and diluted with ion-exchanged water, inductively coupled plasma mass spectrometer group 13 of the periodic table in (ICP-MS) element amount X ₁₃ Then, the carbon content C and the oxygen content O are quantified. The periodic table group 13 element content (X ₁₃ / X ₁₃ + C + O × 100) obtained here is defined as the bulk content (mass%) of the periodic table group 13 element.

<Surface abundance ratio of Group 13 element of periodic table>
The abundance ratio of the group 13 element in the periodic table in the bulk of the negative electrode active material layer for a non-aqueous electrolyte secondary battery in the present invention (also referred to as a surface abundance ratio in the present invention) is the above-mentioned surface element amount X _It is defined as a value calculated from ₁₃ / C value and bulk content using the following (formula 3).
(Formula 3)
Surface abundance ratio = surface element amount X ₁₃ / C value (%) of group 13 element of periodic table represented by (formula 2) / periodic table 13 obtained from inductively coupled plasma mass spectrometry (ICP-MS) analysis Group element bulk content (% by mass)

(2) Surface Functional Group Amount The surface functional group amount is measured using X-ray photoelectron spectroscopy (XPS).
The surface functional group amount O / C value is measured using an X-ray photoelectron spectrometer (ESCA manufactured by ULVAC-PHI) as an X-ray photoelectron spectroscopy measurement so that the surface of the object to be measured (negative electrode material, carbon material) becomes flat. The sample is placed on a sample stage, and the spectrum of C1s (280 to 300 eV) and O1s (525 to 545 eV) is measured by multiplex measurement using an aluminum Kα ray as an X-ray source. The obtained C1s peak top is corrected to be 284.3 eV, the peak areas of the C1s and O1s spectra are obtained, and the device sensitivity coefficient is multiplied to calculate the surface atomic concentrations of C and O, respectively. The obtained atomic concentration ratio O / C (O atomic concentration / C atomic concentration) of O and C is defined as the surface functional group amount O / C value.

(3) Average particle size The average particle size was measured by adding 0 mL of a 0.2% by weight aqueous solution of polyoxyethylene sorbitan monolaurate (for example, Tween 20 (registered trademark)), which is a surfactant. .01 g was suspended, introduced into a commercially available laser diffraction / scattering particle size distribution measuring apparatus “LA-920 manufactured by HORIBA”, irradiated with 28 kHz ultrasonic waves at an output of 60 W for 1 minute, and then volume-based median in the measuring apparatus What was measured as the diameter is defined as the average particle diameter (d50) in the present invention.

(4) BET specific surface area (SA)
The BET specific surface area is measured by, for example, using a specific surface area measuring device “AMS8000” manufactured by Okura Riken Co., Ltd., by the nitrogen gas adsorption flow method, using the BET single point method. Specifically, 0.4 g of a measurement object is filled in a cell, heated to 350 ° C., pretreated, cooled to liquid nitrogen temperature, and saturated adsorption of 30% nitrogen and 70% He gas is performed. Thereafter, the amount of gas desorbed by heating to room temperature is measured, and the specific surface area is calculated from the obtained results by a normal BET method.

(5) Tap density The tap density is a powder density measuring device using a “tap denser KYT-4000” manufactured by Seishin Enterprise Co., Ltd., and is open to a cylindrical tap cell having a diameter of 1.6 cm and a volume capacity of 20 cm ^3. After dropping the object to be measured through a 300 μm sieve and filling the cell fully, tap with a stroke length of 10 mm is performed 1000 times, and the density obtained from the volume and the weight of the sample is defined as the tap density.

<Example 1>
Liquid petroleum heavy oil mixed with boron oxide (Wako Pure Chemical's first grade reagent) powder is oxidized with an organic compound (residual carbon amount conversion) at 25 ° C, which is a temperature above the softening point of petroleum heavy oil. It mixed so that the mixing ratio (mass ratio) of boron (period table group 13 element mass conversion) might be set to 100: 4.65. The mixture is further spheroidized to 100% by mass of natural graphite particles (d50 = 19.3 μm), 3% by mass in terms of the amount of residual carbon derived from the organic compound, and boron oxide is 100% by mass of the carbon material. In contrast, it was mixed (coated) so as to be 0.14% by mass in terms of the mass of Group 13 elements of the periodic table. The mixture was coated with natural graphite particles, and then fired at 1000 ° C. in an inert gas. The fired product thus obtained was pulverized with a hammer mill (MF10) manufactured by IKA at a rotational speed of 4000 rpm, and then subjected to a classification treatment, which was coated with amorphous carbon having an average particle diameter (d50) of 19.6 μm. A negative electrode material 1 having a structure was obtained. The average particle diameter (d50) of the negative electrode material 1 was 1.02 times the average particle diameter (d50) of the natural graphite particles as the raw material. ICP-MS analysis confirmed that 0.13% by mass of boron was contained in the multilayer carbon material. Table 1 shows the physical properties of the negative electrode material 1 including physical properties other than those described above.

<Production of negative electrode>
Using the negative electrode material 1 obtained in Example 1, an electrode plate having an active material layer with an active material layer density of 1.70 ± 0.03 g / cm ³ was produced. Specifically, the negative electrode material 1 was 20.00 ± 0.02 g, the 1 mass% carboxymethylcellulose sodium salt aqueous solution was 20.00 ± 0.02 g (0.200 g in terms of solid content), and the weight average molecular weight was 270,000. Of styrene / butadiene rubber aqueous dispersion 0.50 ± 0.05 g (0.2 g in terms of solid content) was added, stirred for 5 minutes with a Keyence hybrid mixer, and defoamed for 30 seconds to obtain a negative electrode slurry.
This slurry was applied to a width of 5 cm using a doctor blade so that the negative electrode material was 14.5 ± 0.3 mg / cm ² on a 18 μm-thick copper foil as a current collector, and air-dried at room temperature. Went. Further, after drying at 110 ° C. for 30 minutes, roll pressing was performed using a roller having a diameter of 20 cm to adjust the density of the active material layer to 1.70 ± 0.03 g / cm ³ to obtain an electrode sheet.

<Preparation of positive electrode>
The positive electrode comprises 85% by mass of lithium manganate (LiMnO ₂ ) as a positive electrode active material, 10% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride (PVdF) as a binder. Mixing in methylpyrrolidone solvent gave a slurry.
After this slurry imposed, as positive electrode material on an aluminum foil having a thickness of 15μm as a current collector adheres 18.3 ± 0.5mg / cm ^2, was applied using a blade coater, dried at 130 ° C. did. Further, roll pressing was performed to adjust the density of the active material layer to 2.40 ± 0.05 g / cm ³ and roll pressing was performed to obtain an electrode sheet.

<Battery design>
The negative electrode sheet produced by the above method was punched into a disk shape having a diameter of 12.5 mm, and a lithium metal foil was punched into a disk shape having a diameter of 14 mm as a counter electrode. Between both electrodes, an electrolytic solution in which LiPF ₆ was dissolved to 1 mol / L was impregnated in a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) (volume ratio = 3: 7). A separator (made of a porous polyethylene film) was placed, and a 2016 coin-type battery using the above electrolyte was produced.

<Evaluation>
(1) Initial irreversible capacity measuring method Initial irreversible capacity was measured by the following measuring method using the manufactured 2016 coin type battery.
The lithium counter electrode is charged to 5 mV at a current density of 0.16 mA / cm ² , and 5
The battery was charged at a constant voltage of mV until the charge capacity value became 350 mAh / g, and after doping lithium into the negative electrode, the battery was discharged to 1.5 V with respect to the lithium counter electrode at a current density of 0.33 mA / cm ² . . The difference between the charge capacity (350 mAh / g) and the discharge capacity at this time was calculated as the initial irreversible capacity.

(2) Initial efficiency measurement method About the charge capacity and discharge capacity measured by the said method, the ratio of the discharge capacity with respect to charge capacity was calculated | required, and this was made into initial efficiency (%).

(3) Negative charge transfer resistance (R _ct )
The lithium counter electrode is charged to 5 mV at a current density of 0.16 mA / cm ² , and 5
The battery was charged at a constant voltage of mV until the charge capacity value became 350 mAh / g, and after doping lithium into the negative electrode, the battery was discharged to 1.5 V with respect to the lithium counter electrode at a current density of 0.33 mA / cm ² . . 2 cycles, charging to 5 mV with respect to the lithium counter electrode at a current density of 0.16 mA / cm ² , further charging to a current density of 0.016 mA / cm ² at a constant voltage of 5 mV, lithium in the negative electrode Then, the lithium counter electrode was discharged to 1.5 V at a current density of 0.33 mA / cm ² . Thereafter, the battery was further charged for 2 cycles at a current density of 0.16 mA / cm ² to 5 mV with respect to the lithium counter electrode, and further charged at a constant voltage of 5 mV until a current density of 0.016 mA / cm ² was obtained. The two batteries were disassembled in an Ar atmosphere and two negative electrodes were taken out, and between the two negative electrodes and between the negative electrodes, ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were doped. A separator (made of a porous polyethylene film) impregnated with 30 μl of an electrolytic solution in which LiPF ₆ was dissolved at 1 mol / L was placed in a mixed solvent (volume ratio = 3: 7) to prepare a negative electrode facing cell. Complex impedance measurement was performed in a frequency band of 10 ⁻² to 10 ⁵ Hz, and negative electrode charge transfer resistance (R _ct ) was measured. At this time, in order to avoid the influence of the factor of the low frequency portion, a part of the arc of the negative electrode resistance component that appears when the Argand plot was performed was extrapolated with a semicircle, and the numerical values of the two parameters were obtained. The numerical value was an average value of the results of two coin-type cells. The results are shown in Table 2.

<Comparative Example 1>
Comparison with a multilayer structure coated with amorphous carbon containing no boron in the same manner as in Example 1 except that the boron oxide (primary reagent manufactured by Wako Pure Chemical Industries) powder was not added to the petroleum heavy oil. A negative electrode material 1 was obtained. Table 1 shows the physical properties of the comparative negative electrode material.
About this, the initial irreversible capacity | capacitance and the negative electrode charge transfer resistance were measured with the said measuring method, and the initial stage efficiency was computed. The results are shown in Table 2.

<Comparative Example 2>
The graphite particles used in Example 1 were used as they were as the comparative negative electrode material 2, and the initial irreversible capacity and the negative electrode charge transfer resistance were measured by the measurement methods, and the initial efficiency was calculated. The physical properties of the comparative negative electrode material 2 are shown in Table 1, and the evaluation results are shown in Table 2.

<Comparative Example 3>
Example 1 except that boron oxide was mixed so that the mixing ratio (mass ratio) of the organic compound (converted to the amount of remaining carbon) and boron oxide (converted to the mass of the Group 13 element of the periodic table) was 100: 21.7. The comparative negative electrode material 3 having a multilayer structure coated with amorphous carbon having an average particle diameter (d50) of 19.8 μm was obtained. The average particle diameter (d50) of the comparative negative electrode material 3 was 1.03 times the average particle diameter (d50) of the natural graphite particles as a raw material. ICP-MS analysis confirmed that 0.62 mass% boron was contained with respect to the comparative negative electrode material 3. Table 1 shows the physical properties of the comparative negative electrode material 3 including other physical properties. About this, the initial irreversible capacity | capacitance and the negative electrode charge transfer resistance were measured with the said measuring method, and the initial stage efficiency was computed. The evaluation results are shown in Table 2.

<Comparative example 4>
Example 1 except that boron oxide was mixed so that the mixing ratio (mass ratio) of the organic compound (converted to the amount of remaining carbon) and boron oxide (converted to the mass of Group 13 elements of the periodic table) was 100: 1.45. The comparative negative electrode material 4 having a multilayer structure coated with amorphous carbon having an average particle diameter (d50) of 19.6 μm was obtained. The average particle diameter (d50) of the comparative negative electrode material 4 was 1.02 times the average particle diameter (d50) of the natural graphite particles as the raw material. ICP-MS analysis confirmed that 0.04 mass% boron was contained with respect to the comparative negative electrode material 4. Table 1 shows the physical properties of the comparative negative electrode material 4 including other physical properties. About this, the initial irreversible capacity | capacitance and the negative electrode charge transfer resistance were measured with the said measuring method, and the initial stage efficiency was computed. The evaluation results are shown in Table 2.

  The negative electrode material of the present invention can be used as a negative electrode material for a non-aqueous electrolyte secondary battery, thereby producing a non-aqueous electrolyte secondary battery having a high capacity, a small amount of gas generation, and good input / output characteristics even at low temperatures. Can be provided. Moreover, according to the manufacturing method of the negative electrode material for nonaqueous electrolyte secondary batteries of this invention, it becomes possible to manufacture the negative electrode material which has the above-mentioned advantage in a simple process.

Claims (7)

A method for producing a negative electrode material for a non-aqueous electrolyte secondary battery comprising a compound containing boron and having a carbon material coated with amorphous carbon,
A mixing step in which an organic compound having a softening point of 150 ° C. or less and a compound containing boron are mixed at or above the softening point of the organic compound;
A coating step of coating the carbon material on the mixture obtained in the mixing step with respect to 100% by mass of the carbon material at a ratio of 0.05% by mass or more and 0.6% by mass or less in terms of boron element mass,
A firing step in which the coated carbon material obtained in the coating step is fired at 600 ° C. or more and 2300 ° C. or less; and a fired product obtained in the firing step has an average particle diameter (d50) of 5 μm or more and 35 μm or less. Crushing process,
At least look at including the,
The crushing step is a crushing step of crushing so that the surface element amount X ₁₃ / C value of the boron element represented by the following (formula 2) of the pulverized product is 0.7% or more and 4.5% or less. The manufacturing method of the negative electrode material for nonaqueous electrolyte secondary batteries characterized by these.
(Formula 2)
Surface element amount X ₁₃ / C value (%) of boron element = Boron element concentration / XPS analysis obtained based on peak area of spectrum of outermost electron trajectory of boron element in X-ray photoelectron spectroscopy (XPS) analysis C atom concentration determined based on the peak area of the C1s spectrum × 100 In the coating step, the carbon material obtained in the mixing step is mixed in an amount of 0.01% by mass or more and 20% by mass or less in terms of the amount of residual carbon derived from the organic compound with respect to 100% by mass of the carbon material. The manufacturing method of the negative electrode material for non-aqueous electrolyte secondary batteries of Claim 1 which coat | covers. 3. The non-aqueous electrolyte secondary solution according to claim 1, wherein a mixing ratio (mass ratio) of the organic compound and the compound containing boron is 1: 0.001 to 10 in the mixing step. A method for producing a negative electrode material for a battery.
However, the mixing ratio is calculated in terms of the amount of residual carbon derived from the organic compound and the amount of boron-containing compound in terms of boron element mass. The average particle size (d50) of the pulverized product obtained in the pulverization step is 0.8 times or more and 1.2 times or less than the average particle size (d50) of the carbon material. The manufacturing method of the negative electrode material for non-aqueous electrolyte secondary batteries of any one of -3 . The non-aqueous electrolyte solution 2 according to any one of claims 1 to 4 , wherein the boron-containing compound includes one or more selected from the group consisting of boron oxide, boric acid, boron carbide, and boron nitride. The manufacturing method of the negative electrode material for secondary batteries. The carbon material is characterized in that the surface oxygen element content O / C value represented by the following equation (1) is 3% or less than 0.2% in any one of claims 1 to 5 The manufacturing method of the negative electrode material for non-aqueous electrolyte secondary batteries of description.
(Formula 1)
Surface oxygen element amount O / C value (%) = oxygen concentration obtained based on the peak area of the spectrum of outermost electron trajectory of oxygen in X-ray photoelectron spectroscopy (XPS) analysis / peak of C1s spectrum in XPS analysis C atom concentration determined based on area × 100 The method for producing a negative electrode material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 6 , wherein the carbon material has a Raman R value of 0.1 or more and 1 or less.