JP2013201125A - Nonaqueous secondary battery bilayer structure carbon material and nonaqueous secondary battery anode and nonaqueous secondary battery using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous secondary battery carbon material which can achieve high capacity even when rolled with such a degree of pressure that does not cause material breakdown and can restrain charge/discharge irreversible capacity.SOLUTION: A nonaqueous secondary battery bilayer structure carbon material is provided, in which at least part of the surfaces of graphite particles are covered with carbonaceous matter, characterized in that the following conditions (1) to (3) are satisfied: (1) The average grain size d50 of the bilayer structure carbon material 19.1 μm to 50 μm, both ends incl.; (2) The circularity of the bilayer structure carbon material is 0.88 or more; (3) a ratio (P/d50) of a rolling load (P) defined below to d50 of the bilayer structure carbon material is 30 or less. P=linear pressure (kg/5 cm) necessary to roll an anode active material layer under a specific condition using the bilayer structure carbon material.

Description

  The present invention relates to a multilayer carbon material used for a non-aqueous secondary battery, a negative electrode for a non-aqueous secondary battery formed using the material, and a non-aqueous secondary battery having the negative electrode.

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

  As a negative electrode material for a non-aqueous secondary battery, a graphite material or amorphous carbon is often used in terms of cost and durability. And when charging / discharging in a metal electrode is repeated, the metal in an electrode solvent precipitates in a dendrite shape, and finally solves the problem of short-circuiting the positive electrode and the negative electrode, and has excellent discharge capacity, charge / discharge efficiency and Various studies have been made to achieve rapid charge / discharge characteristics and the like.

  For example, in Patent Document 1, as a method for producing a carbon material for an electrode of a lithium battery having a large discharge capacity and charge / discharge efficiency, mesophase spherules are fired while being heated at a temperature rising rate of 40 ° C./hour or less, quinoline. Carbonization of mesophase spherules having an insoluble content of 89.5% by weight or more and / or toluene insolubles of 93.6% by weight or more, and pulverizing the mesophase spherules to obtain a powder having a particle size d50 of 1.3 to 15 μm After forming into granules, carbonize at a temperature of 600-1500 ° C. or carbonize mesophase spherules at a temperature of 600-1500 ° C. and then pulverize to obtain powder having an average particle size d50 of 1.8-15 μm The manufacturing method of the carbon material for electrodes including making it a granule is disclosed.

  Further, Patent Document 2 discloses spheroidized graphite and carbonaceous particles obtained by processing a graphite material which has a high capacity but is difficult to obtain a filling property in order to obtain rapid charge / discharge characteristics and a high capacity. And a multilayer carbon material obtained by carbonizing the organic compound after mixing the obtained spheroidized graphite and the organic compound.

  Further, Patent Document 3 discloses that an amount of carbon remaining on the surface of the graphitic carbonaceous material is 12 parts by weight or less and 0.1 parts by weight or more with respect to 100 parts by weight of the graphitic carbonaceous material. An electrode material formed by adhering a small amount (thin) organic carbide is disclosed, and by using it, the electric capacity is higher and the retention is higher than that of graphite alone or a conventional clear multi-layer structure carbon material. It is described that a non-aqueous solvent secondary battery can be obtained that has a very good electrical performance that is suppressed to a low level and that is also highly safe against electrolytes.

Patent Document 4 _discloses that the discharge volume, the initial charge / discharge efficiency, the rate are improved by setting the pore volume of the graphite core material, the d _{002 of} the negative electrode material, the R value, and the peak intensity ratio of the Raman spectrum within a certain range. A negative electrode material for a lithium ion secondary battery that achieves characteristics and cycle characteristics is described. In the examples of this document, the average particle size of the graphitized material used as the graphite core material is 10 μm.

  In Patent Document 5, in a lithium ion battery having an electrolyte containing at least an ionic liquid composed of bis (fluorosulfonyl) imide anion and a lithium salt, a positive electrode, and a negative electrode, the negative electrode active material is amorphous on the surface of the graphite particles. It is described that the irreversible capacity is reduced and the capacity is improved by a lithium ion battery characterized by being coated or adhered with carbon. In this document, no consideration is given to the particle size of the graphite particles.

  In Patent Document 6, graphite particles coated with amorphous carbon are used as a negative electrode active material, and a non-aqueous secondary battery using an organic electrolyte of a specific composition provides excellent potential flatness and low temperature characteristics, It is stated that the capacity has been achieved. In the examples of this document, graphite particles having a particle size of about 13 to 18 μm are used as a raw material for the negative electrode active material.

  Patent Document 7 discloses a lithium ion secondary battery characterized in that a coating layer made of carbide is formed on the surface of pressurized graphite particles obtained by pressurizing natural graphite spheroidized particles and / or natural graphite agglomerated particles. It is described that an excellent electrode density, initial efficiency, and load characteristics have been achieved by a graphite material for a secondary battery. In the present invention, although the average particle diameter of the graphite material is defined as 5 to 50 μm, the actual material used in the examples is up to 13 μm.

  Patent Document 8 describes excellent rapid charge / discharge by using a negative electrode material containing two types of carbon materials in which the spacing between 002 planes, tap density, peak intensity ratio in Raman spectrum, etc. are in a certain range by X-ray wide angle diffraction method. It describes that the characteristics and cycle characteristics have been achieved. Although the average particle diameter of the two types of carbon materials constituting the negative electrode material is defined as 2 to 30 μm, the average particle diameter of the carbon material actually produced in the examples is 11.6 to 13.4 μm. It is.

  Patent Document 9 discloses that an electrolytic solution is decomposed by low crystalline carbon-coated graphite having an average particle size of 10 to 30 μm and a specific surface area before and after the formation of the low crystalline carbon coating layer is reduced in a specific ratio range. It is described that charging / discharging efficiency and cycle life are improved. In addition, in the examples of the document, carbon materials of various conditions in which the average particle diameter is 10 to 30 μm and the graphite powder is coated using a pitch of 2.0 to 4.5% by mass are studied. When a product with a large particle size (average particle size> 19 μm) whose specific surface area before the formation of the low crystalline carbon coating layer is originally used is used, the specific surface area before and after the formation of the low crystalline carbon coating layer is within a specific range. Therefore, the pitch amount is set to a relatively high value of 4.5% by mass.

  In Patent Document 10, the ratio of the average thickness to the average diameter, the ratio between d10 and d90, and the nonaqueous electrolyte secondary battery using the graphite powder having a volume content of particles of 4 μm or less of 4% or less are excellent. It is described that discharge characteristics and cycle life characteristics have been achieved. In the claims of this document, the average particle size of the graphite powder is defined as 10 to 35 μm, and in the examples, the carbon powder is coated with 5 wt% petroleum-based tar pitch.

  Patent Document 11 describes that excellent capacity density and input / output characteristics are achieved by a negative electrode carbon material for a lithium secondary battery composed of graphite coated with a low crystalline carbon material and a specific carbon material. Has been. In the examples of this document, the graphite having a D50 of 21.5 μm and the carbon material having a D50 of 10.5 μm are manufactured.

In Patent Document 12, (b) a volume average particle diameter of 2 to 70 μm, (c) a tap density of 0.80 g / cm ³ or more, (d) an average circularity of 0.94 or more, (e) a wavelength of 514. in an argon ion laser Raman spectrum using argon ion laser light of 5 nm, the multilayer structure carbonaceous material is R value is the ratio of the scattering intensity of 1360 cm ^-1 relative scattering intensity 1580 cm ^-1 is 0.15 or more, a press It is described that the load can be kept low, and as a result, the high discharge capacity and the irreversible capacity during initial charge / discharge can be lowered. The volume average particle diameter of the multilayer structure carbonaceous material produced in the examples of the document is 16.4 to 16.8 μm.

  In Patent Document 13, a graphite-based material as a core material is immersed in an organic compound at 10 to 300 ° C., the immersed graphite-based material is separated, and an organic solvent is added to the separated graphite-based material at 10 to 300 ° C. After the cleaning process, the carbon material obtained by carbonization or carbon particles aggregated from the carbon particles is crushed and classified to adjust the particle size. It is described that a highly safe lithium secondary battery having excellent charge / discharge characteristics is provided by the carbon material manufacturing method. The thickness of the low crystalline carbon is about 0.01 to 0.1 μm, and in the examples, a carbon material having a number average particle diameter of 10 μm is manufactured.

  Patent Document 14 is a negative electrode material having an average particle diameter of 100 μm or less in which a coating layer of crystalline carbon is formed on the surface of graphite particles, and the graphite particles have a laminated structure in which the graphite particles are bent. It is described that the production of a lithium secondary battery having a high energy density is enabled by the negative electrode material for a lithium secondary battery. In the examples of the document, spheroidized graphite particles having an average particle diameter of 25.4 μm are used, and 3 to 14% carbon coating is applied thereto.

  Patent Document 15 includes a composite carbon material in which the surface of carbonaceous particles is coated with amorphous carbon, and a non-aqueous electrolyte secondary battery containing a specific amount of a specific compound as a non-aqueous electrolyte solvent has excellent charge / discharge characteristics. And that the cycle characteristics have been achieved. In the examples of this document, scaly natural graphite having an average particle diameter of 20 μm is used as the carbonaceous particles.

Japanese Patent No. 3634408 Japanese Patent No. 3916012 Japanese Patent No. 3712288 JP 2011-243567 A JP 2010-97696 A JP-A-9-237638 JP 2011-60465 A JP 2010-251315 A WO2008 / 093724 Pamphlet JP 2000-90930 A JP 2009-117240 A JP 2009-209035 A Japanese Patent Laid-Open No. 10-36108 JP 2002-367611 A JP 2004-265754 A

  By the way, when composing a negative electrode for a non-aqueous secondary battery with a powder of a carbon material for a graphite-based non-aqueous secondary battery, the powder and a binder are mixed, and a dispersion medium is added thereto to create a slurry. A method of applying to a metal foil as a current collector and then drying the dispersion medium is generally used.

  At this time, it is common to provide a step of further rolling for the purpose of pressing the powder to the current collector, making the electrode plate thickness uniform, and improving the electrode plate capacity. By this rolling step, the electrode plate density of the negative electrode is improved, and the energy density per volume of the battery is further improved.

  Considering that the thickness of the electrode plate is uniform, it is considered advantageous to reduce the particle size of the graphite-based nonaqueous secondary battery carbon material to some extent. In fact, in the invention disclosed in Patent Document 1, The particle size of the carbon material for electrodes is 15 μm or less.

  Also in Patent Documents 4, 6, 7, 8, 12, and 13, the particle size of those actually manufactured at the example level is up to about 18 μm.

  Moreover, in order to increase an electrode plate density, the pressure of rolling becomes high. However, with conventional carbon materials for non-aqueous secondary batteries, if rolling is performed at a pressure sufficient to achieve a high capacity, the carbon material is damaged and material destruction occurs. There is a problem that the irreversible capacity of discharge increases, and as a result, high capacity cannot be achieved.

  Therefore, the present invention solves such problems, and for non-aqueous secondary batteries that can achieve a high capacity even by rolling at a pressure that does not cause material destruction and the charge-discharge irreversible capacity can be kept small. The object is to provide a carbon material.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors surprisingly applied at least a part of the surface of spherical graphite particles having a large average particle diameter to a carbonaceous material thinner than before. By using the produced multi-layer structure carbon material as a negative electrode material, it has been found that a sufficiently high capacity non-aqueous secondary battery electrode can be obtained even by rolling at a pressure that does not cause material destruction. It came to.

  In the conventional spheroidizing technique of graphite particles, when the particles are processed so as to have a spherical shape, the graphite particles become small, and it is difficult to produce spherical graphite particles having a large average particle diameter. However, recent advances in spheroidization technology have made it possible to simultaneously achieve a large average particle size and high circularity.

  When an electrode is manufactured using a carbon material obtained by coating a conventional graphite having a small particle size with a carbonaceous material, an appropriate pressure is required for the electrode press. Side reaction with liquid increases. In addition, since the carbon material is hard and not easily deformed because it has a small and divided structure in the particles, the particle indirect points of the carbon material at the electrode are small (point contact), and therefore between the particles. The adhesive strength is weak and the electrode strength is low.

  On the other hand, according to the present invention, since the graphite particles having a large particle size are coated with a smaller amount of carbonaceous material than before, the obtained carbon material particles are soft and do not require a strong press to form an electrode. It is. For this reason, the material of the carbon material is not easily broken during the production of the electrode, and the carbon material is soft and easily deformed. Therefore, the particle indirect point is large (surface contact) in the electrode, and thus the adhesive force between the particles is high.

That is, the gist of the present invention is that a multilayer for a non-aqueous secondary battery is characterized in that at least a part of the surface of the graphite particles is coated with a carbonaceous material and satisfies the following conditions (1) to (3): Structural carbon material:
(1) The average particle diameter d50 of the multi-layer structure carbon material is 19.1 μm or more and 50 μm or less (2) The circularity of the multi-layer structure carbon material is 0.88 or more (3) The ratio (P / d50) between the rolling load (P) and d50 of the multilayer carbon material is 30 or less:
P = (collecting negative electrode active material using the multi-layer structure carbon material and containing 1% by mass of carboxymethyl cellulose sodium salt and 1% by mass of styrene-butadiene rubber as a binder with respect to the multi-layer structure carbon material. A negative electrode active material layer deposited on the negative electrode active material layer in an amount of 12.0 mg / cm ² was prepared, and the linear pressure (kg / kg) required to roll the negative electrode active material layer to a density of 1.6 g / cm ^3. 5cm))
Exist.

  In the non-aqueous secondary battery using the negative electrode for non-aqueous secondary battery obtained in the present invention, material destruction of the negative electrode material hardly occurs in the negative electrode, and the side reaction with the electrolytic solution is reduced. Since the initial efficiency is improved and the initial irreversible capacity is small, a high capacity can be achieved. Furthermore, since the multi-layer structure carbon material for non-aqueous secondary batteries of the present invention to be a negative electrode is soft, the adhesion between the carbon material particles in the negative electrode is strong, and an excellent negative electrode strength is achieved.

  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.

[Multi-layer carbon material for non-aqueous secondary batteries]
The multi-layer structure carbon material for non-aqueous secondary batteries of the present invention (hereinafter also simply referred to as “multi-layer structure carbon material of the present invention”) is obtained by coating at least part of the surface of the graphite particles with a carbonaceous material. The following conditions (1) to (3) are all satisfied. The term “multilayer” as used herein refers to an embodiment in which at least a part or the entire surface of the graphite particles (nuclear graphite) is coated or attached with a carbonaceous material. This aspect can be confirmed by the following physical properties and SEM photographs.

(1) The average particle diameter d50 of the multi-layer structure carbon material is 19.1 μm or more and 50 μm or less (2) The circularity of the multi-layer structure carbon material is 0.88 or more (3) The ratio (P / d50) between the rolling load (P) and the d50 of the multilayer carbon material is 30 or less:
P = (collecting negative electrode active material using the multi-layer structure carbon material and containing 1% by mass of carboxymethyl cellulose sodium salt and 1% by mass of styrene-butadiene rubber as a binder with respect to the multi-layer structure carbon material. A negative electrode active material layer deposited on the negative electrode active material layer in an amount of 12.0 mg / cm ² was prepared, and the linear pressure (kg / kg) required to roll the negative electrode active material layer to a density of 1.6 g / cm ^3. 5cm))

  Hereinafter, these conditions and conditions preferably satisfied by the multilayer structure carbon material of the present invention will be described in order. In the present invention, a multilayer structure carbon material satisfying the above conditions (1) to (3) may be used alone or in combination with other carbon materials.

(1) Volume-based average particle diameter (average particle diameter d50)
The volume-based average particle diameter (also referred to as “average particle diameter d50”) of the multi-layer structure carbon material of the present invention is 19.1 μm or more, preferably 20.1 μm or more, more preferably 22 μm or more, and particularly preferably 24 μm or more. The average particle diameter d50 is 50 μm or less, more preferably 40 μm or less, still more preferably 35 μm or less, and particularly preferably 31 μm or less. When the average particle diameter d50 is too small, the filling property at the time of compression molding of the particles tends to decrease and the rolling load (P) tends to increase. In addition, the non-aqueous secondary battery obtained by using the carbon material tends to increase the irreversible capacity and cause loss of the initial battery capacity. On the other hand, if the average particle size d50 is too large, the process disadvantages such as striation in slurry application. Generation, high current density charge / discharge characteristics, and low temperature input / output characteristics may be deteriorated.

  Further, in this specification, the average particle diameter d50 is obtained by multiplying 10 mL of a 0.2% by mass aqueous solution of polyoxyethylene sorbitan monolaurate (for example, Tween 20 (registered trademark)), which is a surfactant, into multiple layers. Suspend 0.01 g of the structural carbon material, and introduce it as a measurement sample into a commercially available laser diffraction / scattering particle size distribution measuring apparatus (for example, LA-920 manufactured by HORIBA), and output 28 kHz ultrasonic waves to the measurement sample at an output of 60 W. After irradiation for 1 minute, the volume is defined as a volume-based median diameter measured by the measurement apparatus.

(2) Circularity The circularity of the multi-layer structure carbon material of the present invention is 0.88 or more, preferably 0.90 or more, more preferably 0.91 or more. Further, the circularity is usually 1 or less, preferably 0.98 or less, more preferably 0.97 or less. If the circularity is too small, the high current density charge / discharge characteristics of the non-aqueous secondary battery tend to deteriorate. The circularity is defined by the following formula, and when the circularity is 1, a theoretical sphere is obtained.

Circularity = (perimeter of equivalent circle having the same area as the particle projection shape) / (actual circumference of particle projection shape)

  As the circularity value, for example, a flow type particle image analyzer (for example, FPIA manufactured by Sysmex Industrial Co., Ltd.) is used, and about 0.2 g of a sample (multi-layer structure carbon material) is added to polyoxyethylene (surfactant). 20) Disperse in a 0.2% by weight aqueous solution of sorbitan monolaurate (about 50 mL), irradiate the dispersion with 28 kHz ultrasonic waves at an output of 60 W for 1 minute, specify a detection range of 0.6 to 400 μm, The value measured for particles having a particle size in the range of 1.5 to 40 μm is used.

  A method for improving the degree of circularity is not particularly limited, but a spheroidized sphere is preferable because the shape of the interparticle voids when the negative electrode is formed is preferable. Examples of spheroidizing treatment include a method of mechanically approaching a sphere by applying a shearing force and a compressive force, and a mechanical / granularization of a plurality of multi-layered carbon material particles by the adhesive force of the binder or the particles themselves. Examples include physical processing methods.

  In the conventional spheronization processing technology, when trying to achieve the high circularity as described above, the average particle diameter of the carbon material has been reduced. It has become possible to balance the diameter.

(3) Ratio of rolling load (P) to d50 of the multilayer carbon material In the multilayer carbon material of the present invention, 1% by mass of carboxymethylcellulose sodium salt and 1% by mass of styrene-butadiene rubber are obtained. A negative electrode active material layer is prepared by adhering a negative electrode active material containing a binder as a binder to the current collector in an amount of 12.0 mg / cm ² , and the density of the negative electrode active material layer is 1.6 g / cm ^3. The ratio (P / d50) between the rolling load (P), which is the linear pressure (kg / 5 cm) required for rolling, and the average particle diameter d50 of the multilayer carbon material is 30 or less, preferably 3 to 25, more preferably 4-22.

  The particles of the multi-layer structure carbon material of the present invention are softer than the conventional carbon material particles by making the amount of carbonaceous material adhering to a specific range or less, so even if the d50 is the same, the rolling load (P) is higher. It becomes possible to make it small, and the ratio of P / d50 becomes smaller than the conventional carbon material. Further, this ratio is about 3 as a practical lower limit at the time of manufacturing the negative electrode.

  The multilayer structure carbon material for a non-aqueous secondary battery of the present invention can exhibit the above-described effects of the present invention as long as the above requirements are satisfied. It is preferable that any one or more of 4) to (16) is satisfied at the same time. It is particularly preferable that the following condition (4) is satisfied.

(4) Amount of carbonaceous material attached The amount of carbonaceous material attached to the multi-layer structure carbon material of the present invention indicates the amount of carbonaceous material coated on the graphite particles. In the present invention, this is 0.01-2. 0.7% by mass, preferably 0.1% by mass or more, more preferably 0.3% or more, particularly preferably 0.7% by mass or more, and the amount of attachment is preferably 2.5% by mass. Hereinafter, it is more preferably 2.3% by mass or less, further preferably 2.1% by mass or less, particularly preferably 1.8% by mass or less, and most preferably 1.3% by mass or less.

  When the amount of adhesion exceeds 2.7% by mass, when rolling is performed at a pressure sufficient to achieve a high capacity in a non-aqueous secondary battery, the carbon material is damaged and material destruction occurs. There is a tendency to increase the irreversible capacity during charge and discharge during cycles and to reduce the initial efficiency.

  On the other hand, if the amount of attachment is less than 0.01% by mass, the effect of forming a multilayer tends to be difficult to obtain. That is, the side reaction with the electrolytic solution in the battery cannot be sufficiently suppressed, and the charge / discharge irreversible capacity during the initial cycle tends to increase and the initial efficiency tends to decrease. Even if the carbonaceous material layer is thin, if it exists uniformly over most of the surface of the graphite particles, the effect of the present invention can be obtained, but the amount of the carbonaceous material becomes too small, and the graphite particles themselves However, if many appear on the outermost surface of the multi-layer structure carbon material of the present invention, the effect of the present invention is hardly obtained.

  Further, the amount of carbonaceous material attached in the present invention can be calculated from the mass of the sample before and after firing the material (as will be described later, the multilayered carbon material of the present invention is obtained by mixing graphite particles and a carbon precursor, Obtained by heat treatment). At this time, the calculation is performed on the assumption that there is no mass change before and after firing the graphite particles.

If w1 is the mass of graphite particles before firing (kg), and w2 is the mass of multilayered carbon material particles after firing (kg),
Amount of carbonaceous material attached (mass%) = [(w2-w1) / w2] × 100
Is calculated as

(5) The tap density of the multilayer structure carbonaceous material for tap density present invention is 0.8 g / cm ³ or more 1.30 g / cm ³ or less, preferably 0.90 g / cm ³ or more 1.20 g / cm ³ or less by weight, more preferably 0.95 g / cm ³ or more 1.10 g / cm ³ or less.

When the tap density is less than 0.8 g / cm ³ , the negative electrode forming material slurry tends to streak when forming an electrode plate, which tends to cause a problem in the process. On the other hand, when the tap density exceeds 1.30 g / cm ³ , the carbon density in the particle of the multilayer structure carbon material is increased, the rolling property is insufficient, and it is difficult to form a high-density negative electrode sheet.

The tap density is measured by dropping the multi-layer structure carbon material of the present invention through a sieve having a mesh size of 300 μm into a cylindrical tap cell having a diameter of 1.6 cm and a volume capacity of 20 cm ³ using a powder density measuring device. Then, a tap having a stroke length of 10 mm is performed 1000 times and defined as the density obtained from the volume at that time and the mass of the sample.

(6) X-ray parameter The d-value (interlayer distance) of the lattice plane (002 plane) obtained by X-ray diffraction by the Gakushin method of the multilayer carbon material of the present invention is usually 0.337 nm or less. If the d002 value is too large, it indicates that the crystallinity is low, and the initial irreversible capacity may increase when a non-aqueous secondary battery is used. On the other hand, since the theoretical value of the interplanar spacing of the 002 plane of graphite is 0.335 nm, the d value is usually 0.335 nm or more.

  The crystallite size (Lc) of the multilayer carbon material obtained by X-ray diffraction by the Gakushin method is usually 1.5 nm or more, preferably 3.0 nm or more. Above this range, particles with low crystallinity are produced, and the reversible capacity may be reduced when a non-aqueous secondary battery is used. The lower limit of Lc is the theoretical value of graphite.

(7) Ash content The ash content contained in the multilayer structure carbon material of the present invention is usually preferably 1% by mass or less and 0.5% by mass or less based on the total mass of the multilayer structure carbon material. More preferably, it is 1 mass% or less. Moreover, it is preferable that the minimum of ash content is 1 ppm or more.

  When the ash content exceeds the above range, in the case of a non-aqueous secondary battery, deterioration of battery performance due to the reaction between the multi-layer structure carbon material and the electrolyte during charge / discharge may not be negligible. On the other hand, if it falls below the above range, the production of the carbon material requires a lot of time, energy, and equipment for preventing contamination, which may increase the cost.

(8) BET specific surface area The specific surface area (SA) measured by the BET method of the multilayer structure carbon material of the present invention is usually 0.2 m ² / g or more, preferably 0.3 m ² / g or more, more preferably 0. .7m ² / g or more, more preferably 1 m ² / g or more, particularly preferably 2m ² / g or more. The specific surface area is usually 100 m ² / g or less, preferably 10 m ² / g or less, more preferably 7 m ² / g or less, still more preferably 4.5 m ² / g or less, particularly preferably 4.0 m ² / g or less. Most preferably, it is 3.6 m ² / g or less.

  If the value of the specific surface area is too low, the reaction area when the negative electrode is formed using the multi-layer structure carbon material is particularly reduced, requiring a lot of time until full charge, and a preferred non-aqueous secondary battery is It tends to be difficult to obtain.

  On the other hand, if the value of the specific surface area is too high, the reactivity with the electrolyte increases when a negative electrode is formed using a multi-layer structure carbon material, gas generation tends to increase, and the preferred non-aqueous secondary Batteries tend to be difficult to obtain.

  The BET specific surface area was measured by preliminarily drying the multi-layered carbon material sample at 350 ° C. for 15 minutes under a nitrogen flow using a surface area meter (for example, a fully automated surface area measuring device manufactured by Okura Riken), and then nitrogen against atmospheric pressure. This is defined as a value measured by a nitrogen adsorption BET one-point method using a gas flow method, using a nitrogen-helium mixed gas accurately adjusted so that the relative pressure value becomes 0.3.

(9) Pore distribution In the multi-layer structure carbon material of the present invention, voids in the particle corresponding to a diameter of 0.01 μm or more and 1 μm or less, and unevenness due to a step on the particle surface, which are obtained by mercury porosimetry (mercury intrusion method). The amount is usually 0.01 mL / g or more, preferably 0.05 mL / g or more, more preferably 0.1 mL / g or more. The amount is usually 0.6 mL / g or less, preferably 0.4 mL / g or less, more preferably 0.3 mL / g or less.

  If the amount of irregularities is too large, a large amount of binder may be required when forming a negative electrode when forming a negative electrode. On the other hand, if the amount of irregularities is too small, the high current density charge / discharge characteristics of the nonaqueous secondary battery tend to be lowered, and the effect of mitigating the expansion and contraction of the electrode during charge / discharge tends to be not obtained.

  Moreover, the total pore volume of the multi-layer structure carbon material of the present invention is usually 0.1 mL / g or more, preferably 0.2 mL / g or more, more preferably 0.25 mL / g or more. The total pore volume is usually 10 mL / g or less, preferably 5 mL / g or less, more preferably 2 mL / g or less.

  If the total pore volume is too large, a large amount of binder tends to be required when forming an electrode plate. On the other hand, if the total pore volume is too small, there is a tendency that the effect of dispersing the thickener or the binder cannot be obtained when forming an electrode plate.

  Moreover, the average pore diameter of the multilayer structure carbon material of the present invention is usually 0.03 μm or more, preferably 0.05 μm or more, more preferably 0.1 μm or more, and further preferably 0.5 μm or more. The average pore diameter is usually 80 μm or less, preferably 50 μm or less, more preferably 20 μm or less.

  If the average pore diameter is too large, a large amount of binder tends to be required at the time of electrode plate formation, and if the average pore diameter is too small, the high current density charge / discharge characteristics of the battery tend to deteriorate.

  As the mercury porosimetry apparatus, a mercury porosimeter (Autopore 9520: manufactured by Micromeritex Corporation) can be used. A sample (multi-layer structure carbon material) is weighed so as to have a value of about 0.2 g, sealed in a powder cell, and pretreated by degassing at room temperature under vacuum (50 μmHg or less) for 10 minutes. .

  Subsequently, the pressure is reduced to 4 psia (about 28 kPa), mercury is introduced into the cell, the pressure is increased stepwise from 4 psia (about 28 kPa) to 40000 psia (about 280 MPa), and then the pressure is reduced to 25 psia (about 170 kPa).

  The number of steps at the time of pressure increase is 80 points or more, and the mercury intrusion amount is measured after an equilibration time of 10 seconds in each step. The pore distribution is calculated from the mercury intrusion curve thus obtained using the Washburn equation.

  Note that the surface tension (γ) of mercury is calculated as 485 dyne / cm and the contact angle (ψ) is 140 °. The average pore diameter is defined as the pore diameter when the cumulative pore volume is 50%.

(10) True density The true density of the multilayer carbon material of the present invention is usually 1.9 g / cm ³ or more, preferably 2 g / cm ³ or more, more preferably 2.1 g / cm ³ or more, and even more preferably 2 0.2 g / cm ³ or more, and the upper limit is 2.26 g / cm ³ . The upper limit is the theoretical value of graphite. Below this range, the crystallinity of the carbon is too low, and the initial irreversible capacity of a non-aqueous secondary battery may increase.

(11) Aspect ratio The aspect ratio in the powder state of the multilayer structure carbon material of the present invention is theoretically 1 or more, preferably 1.1 or more, more preferably 1.2 or more. The aspect ratio is usually 10 or less, preferably 8 or less, more preferably 5 or less.

  If the aspect ratio is too large, streaking of the slurry containing the multilayered carbon material (negative electrode forming material) may occur during electrode plate formation, or a uniform coated surface may not be obtained, and the high current density of the non-aqueous secondary battery The charge / discharge characteristics tend to be reduced.

  The aspect ratio is expressed as A / B when the longest diameter A of the multi-layer structure carbon material particles when observed three-dimensionally and the shortest diameter B among the diameters orthogonal to the diameter A. The carbon material particles are observed with a scanning electron microscope capable of magnifying observation. Arbitrary 50 carbon material particles fixed to the end face of a metal having a thickness of 50 microns or less are selected, and the stage on which the sample is fixed is rotated and tilted to measure A and B, and A / B Find the average value of.

(12) Maximum particle size dmax
The maximum particle size dmax of the multilayer structure carbon material of the present invention is usually 200 μm or less, preferably 150 μm or less, more preferably 120 μm or less, still more preferably 100 μm or less, and particularly preferably 80 μm or less. If dmax is too large, there is a tendency to cause inconveniences such as line drawing.

  The maximum particle size is defined as the value of the largest particle size at which particles are measured in the particle size distribution obtained when measuring the average particle size d50.

(13) Raman R value The Raman R value of the multilayer carbon material of the present invention is usually 0.1 or more, preferably 0.2 or more. The Raman R value is usually 0.6 or less, preferably 0.55 or less, more preferably 0.5 or less.

Incidentally, the Raman R value is measured and the intensity _{I A} of the peak _{P A} in the vicinity of 1580 cm ^-1 in the Raman spectrum obtained by Raman spectroscopy, the intensity _{I B} of a peak _{P B} in the vicinity of 1360 cm ^-1, the intensity Defined as the ratio (I _B / I _A ).

Incidentally, the scope of 1580～1620Cm ^-1 A "1580cm around ^-1" in the present specification, "1360cm around ^-1" refers to the range of 1350 ^-1.

  If the Raman R value is too small, the crystallinity on the surface of the carbon material particles becomes too high, and when the density is increased, the crystals tend to be oriented in a direction parallel to the negative electrode plate, and the load characteristics tend to decrease. On the other hand, if the Raman R value is too large, the crystal on the particle surface is disturbed, the reactivity of the negative electrode with the electrolytic solution increases, and the charge / discharge efficiency of the non-aqueous secondary battery 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. The measurement conditions are as follows.

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 by simple averaging
5 points)

(14) DBP oil absorption The DBP (dibutyl phthalate) oil absorption of the multi-layer structure carbon material of the present invention is usually 65 ml / 100 g or less, preferably 62 ml / 100 g or less, more preferably 60 ml / 100 g or less, still more preferably 57 ml. / 100g or less. The DBP oil absorption is usually 30 ml / 100 g or more, preferably 40 ml / 100 g or more.

  If the DBP oil absorption is too large, the progress of the spheroidization of the multi-layer structure carbon material is not sufficient, and there is a tendency to cause streaking during the application of the slurry containing the carbon material. There may be almost no pore structure, and the reaction surface tends to decrease.

  The DBP oil absorption amount is defined as a measured value when 40 g of a measurement material (multi-layer structure carbon material) is added, a dropping speed is 4 ml / min, a rotation speed is 125 rpm, and a set torque is 500 N · m, according to JIS K6217. Is done. For the measurement, for example, Absorbometer E type manufactured by Brabender can be used.

(15) Average particle diameter d10
The particle size (d10) corresponding to the cumulative 10% from the small particle side of the particle size measured on a volume basis of the multi-layer structure carbon material of the present invention is usually 30 μm or less, preferably 20 μm or less, more preferably 17 μm or less, usually It is 1 μm or more, preferably 5 μm or more, more preferably 10 μm or more, still more preferably 11 μm or more, and particularly preferably 13 μm or more.

  If d10 is too small, the tendency of the particles to agglomerate becomes strong, which may cause inconveniences such as an increase in slurry viscosity, a decrease in electrode strength and a decrease in initial charge / discharge efficiency in a non-aqueous secondary battery. If d10 is too large, the high current density charge / discharge characteristics may be deteriorated and the low temperature input / output characteristics may be deteriorated.

  d10 is defined as a value obtained by integrating 10% from a particle size having a small particle frequency% in the particle size distribution obtained when measuring the average particle size d50.

(16) Average particle diameter d90
The particle diameter (d90) corresponding to the cumulative 90% from the small particle side of the particle diameter measured on a volume basis of the multi-layer structure carbon material of the present invention is usually 100 μm or less, preferably 70 μm or less, more preferably 60 μm or less, Preferably it is 50 μm or less, particularly preferably 45 μm or less, most preferably 42 μm or less, usually 20 μm or more, preferably 26 μm or more, more preferably 30 μm or more, and even more preferably 34 μm or more.

  If d90 is too small, the electrode strength and initial charge / discharge efficiency of the non-aqueous secondary battery may be reduced. If it is too large, process inconveniences such as striping during the application of slurry will occur, and high current density charge may occur. In some cases, the discharge characteristics and the low-temperature input / output characteristics may deteriorate.

  d90 is defined as a value in which the frequency% of particles is 90% integrated from a small particle size in the particle size distribution obtained when measuring the average particle size d50.

  The conditions (1), (2), and (3) described above are satisfied, and any one or more of the above conditions (4) to (16) (particularly, the condition (4)) are simultaneously satisfied. preferable. The multi-layer structure carbon material of the present invention that satisfies such various conditions includes graphite particles and carbonaceous materials as constituent elements. Hereinafter, these two components will be described.

<Graphite particles>
It is preferable that the graphite particles that are the core graphite of the multilayer carbon material of the present invention satisfy any one or more of the following physical properties. In the present invention, one type of graphite particles exhibiting such physical properties may be used alone, or two or more types may be used in combination in any combination.

(1) X-ray parameters The graphite particles have a d002 value (interlayer distance) of the lattice plane (002 plane) determined by X-ray diffraction by the Gakushin method, which is usually 0.335 nm or more. Moreover, although it is usually less than 0.340 nm, Preferably it is 0.337 nm or less. When the d002 value is too large, the crystallinity is lowered and the initial irreversible capacity of the non-aqueous secondary battery tends to increase.

  The crystallite size (Lc) of the graphite particles determined by X-ray diffraction by the Gakushin method is usually in the range of 30 nm or more, preferably 50 nm or more, more preferably 100 nm or more. Below this range, the crystallinity decreases and the initial irreversible capacity of the battery tends to increase.

(2) Ash content The ash content in the graphite particles is usually 1% by mass or less, preferably 0.5% by mass or less, more preferably 0.1% by mass or less, based on the total mass of the graphite particles. . Moreover, it is 1 ppm or more normally.

  When there is too much ash content, there exists a tendency for battery performance to deteriorate by reaction with the electrolyte solution at the time of charging / discharging of a non-aqueous secondary battery. If the amount of ash is too small, battery production requires a great amount of time, energy, and equipment for preventing contamination, and the cost tends to rise to an unfavorable range as an industrial product.

(3) Volume-based average particle diameter (d50)
The volume-based average particle diameter (d50) obtained by the laser diffraction / scattering method of the graphite particles is usually 15 μm or more, preferably 18 μm or more, more preferably 19 μm or more, still more preferably 20 μm or more, and particularly preferably 23 μm or more. is there. D50 is usually 100 μm or less, preferably 50 μm or less, more preferably 40 μm or less, still more preferably 35 μm or less, and particularly preferably 31 μm or less.

  When the average particle diameter d50 is too small, there is a tendency to increase the irreversible capacity of the non-aqueous secondary battery and to lose the initial battery capacity. On the other hand, if the average particle diameter d50 is too large, process inconvenience such as striation in slurry application may occur, the high current density charge / discharge characteristics of the battery may decrease, and the low temperature input / output characteristics may decrease. In particular, in the present invention, it is preferable to use graphite particles having a volume-based average particle diameter (d50) in the above-described range as a raw material for the multilayer structure carbon material.

(4) Raman R value and Raman half-value width The Raman R value of the graphite particles is usually 0.01 or more, preferably 0.03 or more, more preferably 0.10 or more, and usually 0.60 or less, preferably 0. .50 or less, more preferably 0.40 or less.

  If the Raman R value is too small, the crystallinity of the particle surface becomes too high, and there is a tendency that the number of sites where Li enters between layers decreases with charge / discharge of the nonaqueous secondary battery. That is, there is a tendency that charge acceptance is lowered. On the other hand, if the Raman R value is too large, the crystallinity of the particle surface is lowered, the reactivity with the electrolytic solution is increased, and there is a tendency that efficiency is lowered and gas generation is increased.

Further, the Raman half-width in the vicinity of 1360 cm ^{−1 of the} graphite particles is not particularly limited, but is usually 10 cm ⁻¹ or more, preferably 15 cm ⁻¹ or more. Further, the Raman half-value width is usually 90 cm ⁻¹ or less, preferably 70 cm ⁻¹ or less, more preferably 60 cm ⁻¹ or less.

  If the Raman half-value width is too small, the crystallinity of the particle surface becomes too high, and there is a tendency that the number of sites where Li enters between the layers increases with charge / discharge. That is, there is a tendency that charge acceptance is lowered. On the other hand, if the Raman half-value width is too large, the crystallinity of the particle surface decreases, the reactivity with the electrolytic solution increases, and the efficiency tends to decrease and the gas generation increases.

  In addition, the measuring method of a Raman R value and a Raman half value width is as above-mentioned.

(5) BET specific surface area The specific surface area of the graphite particles measured by the BET method is usually 0.1 m ² / g or more, preferably 0.7 m ² / g or more, more preferably 1 m ² / g or more, and more Preferably it is 2 m ² / g or more. The specific surface area is usually 100 m ² / g or less, preferably 25 m ² / g or less, more preferably 20 m ² / g or less, still more preferably 15 m ² / g or less, particularly preferably 10 m ² / g or less, most preferably. 7 m ² / g or less.

  If the value of the specific surface area is too small, the acceptability of lithium ions tends to deteriorate when the non-aqueous secondary battery is charged when a multilayered carbon material is used as the negative electrode material. On the other hand, if the value of the specific surface area is too large, in the non-aqueous secondary battery, the reactivity between the portion exposed to the electrolytic solution and the electrolytic solution increases, gas generation tends to increase, and a preferable battery tends to be difficult to obtain. is there.

  Further, when the ratio of the carbonaceous material is increased in order to reduce the BET specific surface area of the multi-layer structure carbon material, excessive amorphous material is used, and it tends to be difficult to obtain high output characteristics in the battery.

(6) Pore distribution The amount of voids in the particle corresponding to a diameter of 0.01 μm or more and 1 μm or less, and the amount of irregularities due to the step on the particle surface, which is obtained by mercury porosimetry (mercury intrusion method) of the graphite particles, is usually 0. 0.01 mL / g or more, preferably 0.05 mL / g or more, more preferably 0.1 mL / g or more. The amount is usually 0.6 mL / g or less, preferably 0.4 mL / g or less, more preferably 0.3 mL / g or less.

  If it exceeds this range, a large amount of binder may be required when forming a plate. On the other hand, if the amount of irregularities is too small, the high current density charge / discharge characteristics of the nonaqueous secondary battery tend to be lowered, and the effect of mitigating the expansion and contraction of the electrode during charge / discharge tends to be not obtained.

  Further, the total pore volume of the graphite particles is usually 0.1 mL / g or more, preferably 0.2 mL / g or more, more preferably 0.25 mL / g or more. The total pore volume is usually 10 mL / g or less, preferably 5 mL / g or less, more preferably 2 mL / g or less.

  If the total pore volume is too large, a large amount of binder tends to be required when forming an electrode plate. On the other hand, if the total pore volume is too small, there is a tendency that the effect of dispersing the thickener or the binder cannot be obtained when forming an electrode plate.

  The average pore diameter of the graphite particles is usually 0.05 μm or more, preferably 0.1 μm or more, more preferably 0.5 μm or more, and further preferably 0.75 μm or more. The average pore diameter is usually 50 μm or less, preferably 20 μm or less, more preferably 10 μm or less.

  If the average pore diameter is too large, a large amount of binder tends to be required. On the other hand, if the average pore diameter is too small, the high current density charge / discharge characteristics of the battery tend to deteriorate.

(7) Circularity The circularity of the graphite particles is usually 0.6 or more, preferably 0.7 or more, particularly preferably 0.8 or more, more preferably 0.85 or more, still more preferably 0.88 or more, Particularly preferred is 0.90 or more, and most preferred is 0.91 or more. The circularity is usually 1 or less, preferably 0.99 or less, more preferably 0.98 or less.

If the circularity is too small, the high current density charge / discharge characteristics of the non-aqueous secondary battery tend to deteriorate.
Although the method for improving the circularity is not particularly limited, as described above, a method of performing spheroidization is preferable, and examples thereof include a method of mechanically approaching a sphere by applying a shearing force and a compressive force, and a plurality of fine particles. Examples thereof include a mechanical / physical treatment method in which granulation is performed by the adhesive force of the binder or the particles themselves.

(8) True density The true density of the graphite particles is usually 2 g / cm ³ or more, preferably 2.1 g / cm ³ or more, more preferably 2.2 g / cm ³ or more, and further preferably 2.22 g / cm ^3. The upper limit is 2.26 g / cm ³ . This upper limit is the theoretical value of graphite.

  If the true density is too small, the crystallinity of carbon in the graphite particles is too low, and the initial irreversible capacity of the nonaqueous secondary battery tends to increase.

  The true density in the present invention is defined as a value measured by a liquid phase substitution method (pycnometer method) using butanol.

(9) Tap Density Tap density graphite particles is usually 0.67 g / cm ³ or higher, preferably 0.7 g / cm ³ or more, more preferably 0.8 g / cm ³ or more, particularly preferably 0.88 g / It is desired to be cm ³ or more. Moreover, the tap density is usually 1.5 g / cm ³ or less, preferably 1.4 g / cm ³ or less, more preferably 1.2 g / cm ³ or less, particularly preferably 1.1 g / cm ³ or less.

  If the tap density is too small, when the multilayered carbon material of the present invention is used as a negative electrode forming material, the packing density is difficult to increase, and it is difficult to obtain a high-capacity non-aqueous secondary battery, while the tap density is large. When the amount is too large, voids between particles in the negative electrode are too small, and it is difficult to ensure conductivity between the particles, and it is difficult to obtain preferable battery characteristics.

  In particular, in the present invention, it is preferable to use graphite particles having a tap density in the above-described range as a raw material for the multilayer structure carbon material.

(10) Orientation ratio The orientation ratio of the graphite particles in the powder state is usually 0.01 or more, preferably 0.02 or more, more preferably 0.04 or more, and the upper limit is 0.67. If the orientation ratio is too small, the high-density charge / discharge characteristics of the non-aqueous secondary battery tend to deteriorate.

(11) Aspect ratio The aspect ratio of the graphite particles in a powder state is usually 1 or more, usually 10 or less, preferably 8 or less, and more preferably 5 or less. If the aspect ratio is too large, streaking may occur when forming an electrode plate, a uniform coated surface may not be obtained, and the high current density charge / discharge characteristics of the non-aqueous secondary battery tend to deteriorate.

(12) Average particle diameter d10
The particle size (d10) corresponding to a cumulative 10% from the small particle side on the volume basis of the graphite particles is usually 30 μm or less, preferably 20 μm or less, more preferably 17 μm or less, usually 1 μm or more, preferably 5 μm or more, more preferably It is 10 μm or more, more preferably 11 μm or more, and particularly preferably 13 μm or more. The method for measuring d10 is as described above.

  If d10 is too small, the tendency of the particles to agglomerate becomes strong, which may cause inconveniences such as an increase in slurry viscosity, a decrease in electrode strength and a decrease in initial charge / discharge efficiency in a non-aqueous secondary battery. If d10 is too large, the high current density charge / discharge characteristics may be deteriorated and the low temperature input / output characteristics may be deteriorated.

(13) Average particle diameter d90
The particle size d90 of the graphite particles determined by the laser diffraction / scattering method (particle size that is 90% cumulative from the small particle side on a volume basis) is usually 100 μm or less, preferably 70 μm or less, more preferably 50 μm or less, and even more preferably. Is 45 μm or less, usually 20 μm or more, preferably 26 μm or more, more preferably 30 μm or more, and even more preferably 34 μm or more. The method for measuring d90 is as described above.

  In general, graphite having a large particle size has a large d90, and tends to cause striation at the time of application of a slurry containing the multilayered carbon material of the present invention. It is also important to prevent the d90 of the graphite particles from becoming as large as possible in order to exhibit the effects of the present invention.

  If d90 is too small, the electrode strength in the non-aqueous secondary battery and the initial charge / discharge efficiency may be reduced. If it is too large, process inconveniences such as striation at the time of slurry application will occur, and the high current of the battery In some cases, density charge / discharge characteristics and low-temperature input / output characteristics may deteriorate.

(14) Maximum particle size dmax
The maximum particle diameter dmax of the graphite particles is usually 300 μm or less, preferably 250 μm or less, more preferably 100 μm or less. If dmax is too large, it tends to cause streaking. The method for measuring dmax is as described above.

(Method for producing graphite particles)
The graphite particles described above are graphite particles containing natural graphite and / or artificial graphite as a raw material, or coal-based coke, petroleum-based coke, furnace black, acetylene black, and pitch having slightly lower crystallinity than these. It is preferable to contain a fired product and / or graphitized material selected from the group consisting of carbonaceous fibers, and graphite particles containing natural graphite and / or artificial graphite as raw materials are more preferable. Among these, spheroidized natural graphite obtained by spheronizing natural graphite is particularly preferable as the graphite particles.

  As an apparatus used for the spheronization treatment, for example, an apparatus that repeatedly gives mechanical action such as compression, friction, shearing force, etc. including the interaction of particles mainly with impact force to the particles can be used. Recent advances in spheroidizing technology have made it possible to spheroidize without reducing the particle size of graphite.

  Specifically, it has a rotor with a large number of blades installed inside the casing, and the rotor rotates at a high speed, so that a machine such as impact compression, friction, shearing force, etc. is applied to the graphite particle material introduced inside. An apparatus that imparts a functional effect and performs surface treatment is preferable.

  Moreover, the apparatus which has a mechanism which gives a mechanical action repeatedly by circulating a raw material is preferable. Preferred devices include, for example, a hybridization system (manufactured by Nara Machinery Co., Ltd.), a kryptron (manufactured by Earth Technica), a CF mill (manufactured by Ube Industries), a mechano-fusion system (manufactured by Hosokawa Micron), and a theta composer (Tokuju Kosakusho). Etc.). Among these, a hybridization system manufactured by Nara Machinery Co., Ltd. is preferable.

  Graphite particles are produced by spheroidizing, whereby scale-like natural graphite is folded, or the peripheral edges are spherically pulverized into spherical particles, which are mainly produced by pulverization and have a particle size of 5 μm or less. It is preferable to manufacture by performing spheronization treatment under the condition that the fine powder adheres and the surface functional group amount O / C value of the graphite particles after spheronization treatment is 1% or more and 4% or less.

In this case, it is preferable to perform the spheronization treatment in an active atmosphere so that the oxidation reaction of the graphite surface is advanced by the energy of the mechanical treatment and acidic functional groups can be introduced to the graphite surface. 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.
If the peripheral speed is too fast, d50 tends to be too small due to overgrinding, and if the peripheral speed is too slow, the spheroidizing process is not sufficiently performed and the circularity tends to be low.

  The mechanical treatment can be performed simply by passing the graphite particles through the spheroidizing treatment apparatus, but it is preferable to circulate or stay in the apparatus for 30 seconds or more, and to circulate in the apparatus for 1 minute or more. More preferably, the treatment is carried out by staying. If the residence time is too long, d50 tends to be too small due to overgrinding, and if the residence time is too short, the spheroidization treatment is not sufficiently performed and the circularity tends to be low. By applying such a strong spheroidizing treatment, the fine powder is largely removed, and as a result, a graphite particle having a high degree of circularity and a high tap density, and thus a multi-layer structure carbon material having a high degree of circularity and a high tap density is obtained. It becomes possible.

  Furthermore, if necessary, fine powder and coarse powder can be removed by classification treatment to obtain graphite particles with high circularity and high tap density, and in turn, multi-layered carbon materials with high circularity and high tap density. This is preferable.

  There are no particular restrictions on the apparatus used for classification, but for example, in the case of dry sieving, a rotary sieving, a swaying sieving, a rotating sieving, a vibrating sieving, an air blow feed sieving, etc. can be used. In the case of dry airflow classification, a gravity classifier, an inertial force classifier, or a centrifugal force classifier (classifier, cyclone, etc.) can be used. In the case of wet sieving, a mechanical wet classifier, a hydraulic classifier, a sedimentation classifier, a centrifugal wet classifier, or the like can be used. It is more preferable to use an air blow feed type sieve in terms of both classification accuracy and productivity. Since the classification accuracy is high, only coarse particles can be removed without reducing d50.

  In producing the multilayer structure carbon material of the present invention, it is more preferable to use graphite particles subjected to such treatment as nuclear graphite.

  Specific examples of the artificial graphite include coal tar pitch, coal heavy oil, atmospheric residue, petroleum heavy oil, aromatic hydrocarbon, nitrogen-containing cyclic compound, sulfur-containing cyclic compound, polyphenylene, polychlorinated Organic substances such as vinyl, polyvinyl alcohol, polyacrylonitrile, polyvinyl butyral, natural polymer, polyphenylene sulfide, polyphenylene oxide, furfuryl alcohol resin, phenol formaldehyde resin, and imide resin are usually used at temperatures in the range of 2500 ° C. to 3200 ° C. Examples thereof include those fired and graphitized.

  Further, as the graphite particles having a low graphitization degree, those obtained by firing an organic substance at a temperature of usually 600 ° C. or higher and 2500 ° C. or lower are used. Specific examples of the organic substances include coal-based heavy oils such as coal tar pitch and dry distillation liquefied oil; straight-run heavy oils such as atmospheric residual oil and vacuum residual oil; by-products during thermal decomposition of crude oil, naphtha and the like. 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.

  Further, when obtaining graphitic particles having 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 is usually 2500 ° C., preferably 2000 ° C., more preferably 1400 ° C., although it varies depending on the desired degree of graphitization imparted to the multilayer carbon material. 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.

  For the graphite particles, particles such as metal particles and metal oxide particles may be appropriately mixed in any combination and used. A plurality of materials may be mixed in each particle. For example, the graphite particles used in the present invention are carbonaceous particles having a structure in which the surface of graphite is coated with a carbon material having a low degree of graphitization, or particles re-graphitized by aggregating graphite particles with an appropriate organic substance. Also good. Further, such composite particles may contain a metal that can be alloyed with Li, such as Sn, Si, Al, Bi.

<Carbonaceous material>
In the multilayer structure carbon material for a non-aqueous secondary battery of the present invention, the carbonaceous material covers at least a part of the surface of the graphite particles described above. Examples of the carbonaceous material include amorphous carbon and graphitized material depending on the difference in heating temperature in the production method described later.

  Specifically, the carbonaceous material can be obtained by heat-treating the carbon precursor as described later. The carbon material described in the following (a) or (b) is preferable as the carbon precursor.

  (A) Coal heavy oil, DC heavy oil, cracked heavy oil, aromatic hydrocarbon, N ring compound, S ring compound, polyphenylene, organic synthetic polymer, natural polymer, thermoplastic resin and Carbonizable organic substance selected from the group consisting of thermosetting resins

  (B) Carbonized organic substance dissolved in a low molecular organic solvent

As the coal-based heavy oil, coal tar pitch from soft pitch to hard pitch, dry distillation liquefied oil and the like are preferable,
As the DC heavy oil, atmospheric residual oil, vacuum residual oil, etc. are preferable,
The cracked petroleum heavy oil is preferably ethylene tar produced as a by-product during thermal decomposition of crude oil, naphtha, etc.
As the aromatic hydrocarbon, acenaphthylene, decacyclene, anthracene, phenanthrene and the like are preferable,
As the N-ring compound, phenazine, acridine and the like are preferable,
As the S ring compound, thiophene, bithiophene and the like are preferable,
As the polyphenylene, biphenyl, terphenyl and the like are preferable,
As the organic synthetic polymer, polyvinyl chloride, polyvinyl alcohol, polyvinyl butyral, insolubilized products of these, polyacrylonitrile, polypyrrole, polythiophene, polystyrene and the like are preferable,
As the natural polymer, polysaccharides such as cellulose, lignin, mannan, polygalacturonic acid, chitosan, saccharose and the like are preferable,
As the thermoplastic resin, polyphenylene sulfide, polyphenylene oxide and the like are preferable,
As the thermosetting resin, a furfuryl alcohol resin, a phenol-formaldehyde resin, an imide resin or the like is preferable.

  The carbon precursor is also preferably a carbide such as a solution dissolved in a low molecular organic solvent such as benzene, toluene, xylene, quinoline, n-hexane and the like.

(Physical properties of amorphous carbon)
As described above, the carbonaceous material used in the present invention is amorphous carbon or graphitized material depending on the difference in heating temperature in the production thereof, and the amorphous carbon is subjected to the following conditions (1) to (4). It is desirable that one or more of In the present invention, one type of amorphous carbon exhibiting such physical properties may be used alone, or two or more types may be used in any combination.

(1) X-ray parameters For amorphous carbon, the d002 value (interlayer distance) of the lattice plane (002 plane) determined by X-ray diffraction by the Gakushin method is preferably 0.340 nm or more. It is especially preferable that it is 341 nm or more. Moreover, d002 value is 0.380 nm or less normally, Preferably it is 0.355 nm or less, More preferably, it is 0.350 nm or less.

  If the d002 value is too large, the surface will be remarkably low in crystallinity and the irreversible capacity tends to increase in non-aqueous secondary batteries, while if it is too small, the charge obtained by placing low crystalline carbonaceous material on the surface The effect of improving acceptability is small, and the effect of the present invention tends to be small.

  In addition, the crystallite size (Lc) obtained by X-ray diffraction by the Gakushin method of amorphous carbon is usually in the range of 1 nm or more, preferably 1.5 nm or more. Below this range, the crystallinity may decrease and the increase in the initial irreversible capacity of the battery may increase.

(2) Ash content The ash content contained in the amorphous carbon portion is usually 0.1% by mass or less, preferably 0.01% by mass or less, more preferably, based on the total mass of the multilayer carbon material of the present invention. It is 0.001 mass% or less. The ash content is usually 0.1 ppm or more.

  If the ash content is too small, a large amount of time, energy and equipment for preventing contamination are required for the production of the multi-layered carbon material, and the cost tends to rise to an unpreferable range as an industrial product.

(3) Raman R value and Raman half-value width The Raman R value of amorphous carbon is usually 0.5 or more, preferably 0.7 or more, more preferably 0.9 or more. The Raman R value is usually 1.5 or less, preferably 1.4 or less.

  If the Raman R value is too small, the crystallinity of the particle surface of the multi-layer structure carbon material of the present invention becomes too high, and the number of sites where Li ions enter between layers tends to decrease with charge / discharge of the nonaqueous secondary battery. There is. That is, there is a tendency that charge acceptance is lowered. In addition, when the negative electrode is densified by applying the slurry containing the multilayer structure carbon material of the present invention to the current collector and then pressing it, the crystals are easily oriented in the direction parallel to the electrode plate, and the load characteristics Tends to decrease.

  On the other hand, if the Raman R value is too large, the crystallinity of the particle surface of the carbon material is lowered, the reactivity with the electrolytic solution is increased, and there is a tendency that efficiency is lowered and gas generation is increased.

Further, the Raman half-width in the vicinity of 1580 cm ^{−1 of the} amorphous carbon portion is not particularly limited, but is usually 60 cm ⁻¹ or more, preferably 80 cm ⁻¹ or more, and usually 150 cm ⁻¹ or less, preferably 140 cm ⁻¹ or less. .

  If the Raman half-value width is too small, the crystallinity of the carbon material particle surface becomes too high, and there is a tendency that the number of sites where Li ions enter between the layers increases as the battery is charged and discharged. That is, there is a tendency that charge acceptance is lowered.

  Further, when the density of the negative electrode is increased by applying the slurry to the current collector and then pressing it, the crystals tend to be oriented in the direction parallel to the electrode plate, and the load characteristics tend to decrease. On the other hand, if the Raman half-value width is too large, the crystallinity of the carbon material particle surface is lowered, the reactivity with the electrolytic solution is increased, and there is a tendency that efficiency is lowered and gas generation is increased.

  In addition, the measuring method of a Raman R value and a Raman half value width is as above-mentioned.

(4) True density The true density of the amorphous carbon portion is usually 1.4 g / cm ³ or more, preferably 1.5 g / cm ³ or more, more preferably 1.6 g / cm ³ or more, and still more preferably 1. It is 7 g / cm ³ or more, usually 2.1 g / cm ³ or less, preferably 2 g / cm ³ or less.

  If the true density is too large, the charge acceptability of the nonaqueous secondary battery tends to be impaired. On the other hand, if the true density is too low, the crystallinity of the carbon constituting the amorphous carbon is too low and the initial irreversible capacity of the battery tends to increase.

(Physical properties of graphitized material)
As described above, the carbonaceous material used in the present invention is amorphous carbon or graphitized material depending on the difference in heating temperature in the production thereof. The graphitized material is subjected to the following conditions (1) to (4). It is desirable to satisfy any one or more of them. In the present invention, one type of graphitized product exhibiting such physical properties may be used alone, or two or more types may be used in any combination.

(1) X-ray parameters For graphitized materials, the d002 value (interlayer distance) of the lattice plane (002 plane) determined by X-ray diffraction by the Gakushin method is preferably 0.340 nm or less, and 0.337 nm or less. It is more preferable that On the other hand, since the theoretical value of the interplanar spacing of the 002 plane of graphite is 0.335 nm, the d value is usually 0.335 nm or more.

  If the d002 value is too large, the surface will be remarkably low in crystallinity, and the irreversible capacity tends to increase in non-aqueous secondary batteries. On the other hand, if it is too small, the charge acceptability obtained by placing graphitized material on the surface will be improved. There is a tendency that the effect of the present invention is reduced.

  The crystallite size (Lc) obtained by X-ray diffraction of the graphitized product by the Gakushin method is usually 1 nm or more, preferably 1.5 nm or more. Below this range, the crystallinity may decrease and the increase in the initial irreversible capacity of the battery may increase.

(2) Ash content The ash content in the graphitized part is usually 0.1% by mass or less, preferably 0.01% by mass or less, more preferably 0.8% by mass with respect to the total mass of the multilayer structure carbon material of the present invention. It is 001 mass% or less. The ash content is usually 0.1 ppm or more.

  If the ash content is too small, a large amount of time, energy and equipment for preventing contamination are required for the production of the multi-layered carbon material, and the cost tends to rise to an unpreferable range as an industrial product.

(3) Raman R value and Raman half width The Raman R value of the graphitized product is usually 0.5 or more, preferably 0.7 or more, more preferably 0.9 or more. The Raman R value is usually 1.5 or less, preferably 1.4 or less.

  If the Raman R value is too small, the crystallinity of the particle surface of the multi-layer structure carbon material of the present invention becomes too high, and the number of sites where Li ions enter between layers tends to decrease with charge / discharge of the nonaqueous secondary battery. There is. That is, there is a tendency that charge acceptance is lowered. In addition, when the negative electrode is densified by applying the slurry containing the multilayer structure carbon material of the present invention to the current collector and then pressing it, the crystals are easily oriented in the direction parallel to the electrode plate, and the load characteristics Tends to decrease.

  On the other hand, if the Raman R value is too large, the crystallinity of the particle surface of the carbon material is lowered, the reactivity with the electrolytic solution is increased, and there is a tendency that efficiency is lowered and gas generation is increased.

Further, the Raman half width in the vicinity of 1580 cm ^{−1 of the} graphitized portion is not particularly limited, but is usually 60 cm ⁻¹ or more, preferably 80 cm ⁻¹ or more, and usually 150 cm ⁻¹ or less, preferably 140 cm ⁻¹ or less.

  If the Raman half-value width is too small, the crystallinity of the carbon material particle surface becomes too high, and there is a tendency that the number of sites where Li ions enter between the layers increases as the battery is charged and discharged. That is, there is a tendency that charge acceptance is lowered.

  Further, when the density of the negative electrode is increased by applying the slurry to the current collector and then pressing it, the crystals tend to be oriented in the direction parallel to the electrode plate, and the load characteristics tend to decrease. On the other hand, if the Raman half-value width is too large, the crystallinity of the carbon material particle surface is lowered, the reactivity with the electrolytic solution is increased, and there is a tendency that efficiency is lowered and gas generation is increased.

  In addition, the measuring method of a Raman R value and a Raman half value width is as above-mentioned.

(4) True density The true density of the graphitized portion is usually 1.4 g / cm ³ or more, preferably 1.5 g / cm ³ or more, more preferably 1.6 g / cm ³ or more, and still more preferably 1.7 g / cm ^3. cm ³ or more, usually 2.1 g / cm ³ or less, preferably 2 g / cm ³ or less.

  If the true density is too large, the charge acceptability of the nonaqueous secondary battery tends to be impaired. On the other hand, when the true density is too small, the crystallinity of carbon constituting the graphitized product is too low, and the initial irreversible capacity of the battery tends to increase.

<Production method of multi-layer carbon material>
The method for producing a multilayer structure carbon material of the present invention is such that at least a part of the surface of the graphite particles is covered with a carbonaceous material, and the resulting multilayer structure carbon material has an average particle diameter d50 of 19.1 μm or more and 50 μm or less. The circularity is 0.88 or more, the ratio of the rolling load (P) to the d50 of the carbon material is 30 or less, preferably the carbonaceous material is attached in an amount of 0.01 to 2.7% by mass. If it is the method which becomes, it will not restrict | limit in particular.

  A more specific method for producing a multi-layer carbon material is to use the above-mentioned graphite particles as nuclear graphite, a carbon precursor for obtaining a carbonaceous material as a coating raw material, and mix and fire these. The multilayer structure carbon material of the present invention can be produced by combining the raw materials and controlling various conditions so as to obtain a specific amount of adhesion.

The method of coating the graphite particles with the carbonaceous material is a method of using the carbon precursor for obtaining the carbonaceous material as it is, and heating the mixture of the carbon precursor and the graphite particle powder to obtain a composite powder,
A method in which a carbonaceous material powder obtained by partially carbonizing the carbon precursor is prepared in advance, mixed with a graphite particle powder, and heat-treated to form a composite.
It is possible to employ a method in which the above-mentioned carbonaceous material powder is prepared in advance, and the graphite particle powder, the carbonaceous material powder, and the carbon precursor are mixed and heat-treated to form a composite.

  In the latter two methods of preparing the carbonaceous material powder in advance, it is preferable to use a carbonaceous material having an average particle diameter d50 of 1/10 or less of the average particle diameter d50 of the graphite particles. In addition, by applying mechanical energy such as pulverization to pre-made carbonaceous material and graphite particles, it is possible to adopt a method in which the other is entrained or a method in which the other is electrostatically attached. It is.

  Obtain a mixture of graphite particles and a carbon precursor, or heat a mixture of graphite particles and a carbonaceous material and a carbon precursor to obtain an intermediate material, and then carbonize and fire and grind Thus, it is preferable to finally obtain a multi-layer structure carbon material in which a carbonaceous material is combined (coated) with graphite particles.

  The process of an example of the manufacturing method for obtaining the multi-layered structure carbon material in the present invention is divided into the following four processes.

  First step: Graphite particles, a carbon precursor of carbonaceous material, and, if necessary, a solvent are mixed using various commercially available mixers and kneaders to obtain a mixture.

  2nd process: The said mixture is heated and the intermediate material which removed the volatile matter which generate | occur | produces from a solvent and a carbon precursor is obtained. This heating may be performed while stirring the mixture as necessary. Moreover, even if the volatile matter remains, it is not a problem because it is removed in a later third step.

  Third step: The mixture or intermediate substance is heated to 400 ° C. or higher and 3200 ° C. or lower in a gas atmosphere such as nitrogen gas, carbon dioxide gas, argon gas, or a gas atmosphere generated from the mixture or intermediate substance, to form a multilayer structure Obtain carbon material.

  Fourth step: The multi-layered carbon material is subjected to powder processing such as pulverization, pulverization, and classification as required.

  Among these steps, the second step and the fourth step may be omitted depending on circumstances, and the fourth step may be performed before the third step. However, when the fourth step is performed before the third step, if necessary, powder processing such as pulverization, pulverization, classification, etc. is performed again after the completion of the third step to obtain a multi-layer structure carbon material. .

  Although there is no restriction | limiting in particular as an apparatus used for the heat processing of the raw material of a 3rd process, For example, reaction furnaces, such as a shuttle furnace, a tunnel furnace, a lead hammer furnace, a rotary kiln, an autoclave, a coker (heat processing tank of coke manufacture), a Tamman furnace, An Atchison furnace can be used.

  The heating method of the heat treatment apparatus is not particularly limited, and a high frequency induction heating furnace, direct resistance heating, indirect resistance heating, direct combustion heating, radiant heat heating, or the like can be used.

  In addition, you may stir as needed at the time of heat processing. In addition, the heat history temperature condition is important as the heat treatment condition. The lower temperature limit is usually 600 ° C., preferably 700 ° C., and more preferably 900 ° C., although it varies slightly depending on the type of carbon precursor and its thermal history.

  On the other hand, the maximum temperature can be raised to a temperature at which the carbon precursor basically does not have a structural order exceeding the crystal structure of the graphite particle nucleus. Therefore, the upper limit temperature of the heat treatment is 3200 ° C., preferably 2000 ° C., more preferably 1500 ° C., and further preferably 1200 ° C.

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

  In such a heat treatment condition, the heat history temperature condition, the heating rate, the cooling rate, the heat treatment time, and the like are appropriately set so that the amount of carbonaceous material attached falls within the above range. The adjustment method of the said adhesion amount is well-known, As an example, adjusting the quantity of the graphite particle and carbon precursor mixed in the said 1st process is mentioned.

  Further, after heat treatment in a relatively low temperature region, the temperature can be raised to a predetermined temperature. In addition, the reactor used for this process may be a batch type or a continuous type, and may be one or more.

  The furnace that can be used in the third step is not particularly limited as long as the above requirements are satisfied.

  The apparatus used for the pulverization in the fourth step is not particularly limited. For example, examples of the coarse pulverizer include a shearing mill, a jaw crusher, an impact crusher, and a cone crusher. Examples of the intermediate pulverizer include a roll crusher and a hammer mill. Examples of the pulverizer include a ball mill, a vibration mill, a pin mill, a stirring mill, and a jet mill.

  The apparatus used for the classification process in the fourth step is not particularly limited. For example, in the case of dry sieving, a rotary sieving, a shaking sieving, a rotating sieving, a vibrating sieving, etc. can be used. For airflow classifiers, gravity classifiers, inertial force classifiers, centrifugal classifiers (classifiers, cyclones, etc.) can be used, and wet sieving, mechanical wet classifiers, hydraulic classifiers A sedimentation classifier, a centrifugal wet classifier, or the like can be used.

  There are no particular restrictions on the equipment used for crushing in the fourth step, but roll crushers, hammer mills, ball mills, vibration mills, pin mills, agitation mills, jet mills, and particle interaction mainly including impact force are also included. Apparatus for repeatedly applying mechanical action such as compression, friction, shearing force, etc. to particles, for example, hybridization system (manufactured by Nara Machinery Co., Ltd.), kryptron (manufactured by Earth Technica), CF mill (manufactured by Ube Industries), mechano Fusion system (made by Hosokawa Micron Co., Ltd.), theta composer (made by Tokuju Kogakusho Co., Ltd.), etc. can be used, and the strength is moderately adjusted so that the primary particle size does not become too small before and after the aggregate crushing treatment. By doing, crushing in the said process can be performed.

<Sub-material>
In addition to the multilayer carbon material described above, the multilayer carbon material of the present invention contains one or more carbonaceous materials (carbonaceous materials) having different carbonaceous physical properties, thereby further improving battery performance. It is possible to improve.

  The “carbonaceous physical properties” include X-ray diffraction parameters, median diameter, aspect ratio, BET specific surface area, orientation ratio, Raman R value, tap density, true density, pore distribution, circularity, and ash content. Exhibit one or more characteristics.

  As a preferred embodiment, the carbonaceous material is not symmetrical when the volume-based particle size distribution is centered on the median diameter, or two or more carbonaceous materials having different Raman R values are used. And the use of two or more carbonaceous materials having different X-ray parameters.

  As an example of the effect of using a carbonaceous material, a carbonaceous material such as natural graphite, graphite such as artificial graphite, carbon black such as acetylene black, and amorphous carbon such as needle coke is used as a secondary material. For example, reducing the electric resistance of a non-aqueous secondary battery obtained by using a multi-layer structure carbon material containing the same.

  The carbonaceous material demonstrated above may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and a ratio. When a carbonaceous material is added as a secondary material, it is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 100% by mass with respect to the entire multilayer structure carbon material including the secondary material. It is added in an amount of 0.6% by mass or more, usually 80% by mass or less, preferably 50% by mass or less, more preferably 40% by mass or less, and still more preferably 30% by mass or less.

  If it is less than this range, there is a tendency that the effect of improving conductivity in the battery is difficult to obtain. On the other hand, if this range is exceeded, the initial irreversible capacity of the battery may be increased.

[Electrode production]
The negative electrode may be manufactured by a conventional method. For example, a binder, a solvent, and, if necessary, a thickener, a conductive material, a filler and the like are added to the multilayer carbon material of the present invention to form a slurry, which is applied to a current collector, dried and then pressed. Thus, a negative electrode can be manufactured by forming a multilayer structure carbon material layer on the current collector.

  Here, as explained in [Problems to be Solved by the Invention], in order to achieve a high capacity in a non-aqueous secondary battery and to make the electrode plate thickness of the negative electrode uniform, rolling is performed at a pressure above a certain level. In the conventional negative electrode forming material, the material is damaged due to this pressure, and the material breaks down and the side reaction with the electrolytic solution increases. As a result, the irreversible charge / discharge capacity has increased, and as a result, there has been a problem that it cannot be achieved due to the operation performed to achieve high capacity.

  The multi-layer structure carbon material of the present invention has a relatively large average particle diameter d50 of 19.1 to 50 μm, and the amount of carbonaceous material covering the graphite particles that are the core of the carbon material is small. When a negative electrode is produced using such a carbon material as the slurry, the electrode plate can be made uniform even by rolling at a pressure that does not cause material destruction, and the initial irreversible capacity of the battery is small and sufficiently high capacity is achieved. Is done.

Specifically, in the case where a negative electrode is produced using the multilayer structure carbon material of the present invention as a negative electrode active material, a line necessary for rolling so that the density of the negative electrode active material layer is 1.6 g / cm ^3. The pressure is usually 550 kg / 5 cm or less, preferably 500 kg / 5 cm or less, more preferably 450 kg / 5 cm or less, still more preferably 400 kg / 5 cm or less, usually 100 kg / 5 cm or more. In addition, linear pressure means the force per unit length (it shall be 5 cm in this specification) of the axial direction of the roll used for rolling.

When the linear pressure necessary for rolling so that the density of the negative electrode active material layer is 1.6 g / cm ³ is in the above range, damage to the carbon material is suppressed, so that the initial efficiency is increased in the battery. In addition, the initial gas generated by the side reaction between the negative electrode and the electrolytic solution is reduced. Further, the carbon material particles are appropriately deformed by rolling with an appropriate pressure, the contact area between the particles is increased, and the adhesion strength of the electrode is improved. Since the particle size of the multi-layer structure carbon material of the present invention is large and the amount of carbonaceous material covering the graphite particles that are the core of the carbon material is small, the carbon material is softer than conventional carbon materials, This contributes to the improvement of the electrode strength by increasing the contact area.

  Specifically, the electrode plate strength of the negative electrode obtained using the multilayer structure carbon material of the present invention is usually 3 mN / mm or more, preferably 5 mN / mm, more preferably 7 mN / mm or more, and even more preferably 10 mN. / Mm or more, usually 100 mN / mm or less, preferably 50 mN / mm or less, more preferably 30 mN / mm or less. If this value is too small, peeling of the negative electrode active material layer from the current collector tends to occur and the processability tends to be remarkably impaired. If this value is too large, the flexibility of the negative electrode is lost and the negative electrode is bent or rolled. In this case, the negative electrode active material layer is peeled off and the processability tends to be remarkably impaired.

  The thickness of the multi-layer structure carbon material layer per side at the stage immediately before the electrolyte injection process of the non-aqueous secondary battery is usually 15 μm or more, preferably 20 μm or more, more preferably 30 μm or more, and the upper limit is usually 150 μm. , Preferably 120 μm, more preferably 100 μm.

  If it exceeds this range, the electrolyte solution hardly penetrates to the vicinity of the current collector interface, so that the high current density charge / discharge characteristics of the battery may be deteriorated. On the other hand, below this range, the volume ratio of the current collector to the multilayer structure carbon material increases, and the battery capacity tends to decrease.

  The multi-layer structure carbon material may be roll-formed to form a sheet electrode, or may be compressed to a pellet electrode.

[Negative electrode]
As the current collector for holding the multi-layer structure carbon material of the present invention, a known one can be arbitrarily used. Examples of the current collector for the negative electrode include metal materials such as copper, nickel, stainless steel, and nickel-plated steel. Of these, copper is particularly preferable from the viewpoint of ease of processing and cost.

  When the current collector is a metal material, examples of the current collector include metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punch metal, and foam metal. Among them, a metal thin film is preferable, a copper foil is more preferable, and a rolled copper foil obtained by a rolling method and an electrolytic copper foil obtained by an electrolytic method are more preferable.

  When the thickness of the copper foil is less than 25 μm, a copper alloy (phosphor bronze, titanium copper, Corson alloy, Cu—Cr—Zr alloy, etc.) having higher strength than pure copper can be used.

  A current collector made of a copper foil produced by a rolling method is suitable for use in a small cylindrical battery because the copper crystals are arranged in the rolling direction so that the negative electrode is hard to crack even if it is rounded sharply or rounded at an acute angle. be able to.

  For example, an electrolytic copper foil is prepared by immersing a metal drum in an electrolytic solution in which copper ions are dissolved, and flowing current while rotating the copper drum, thereby depositing copper on the surface of the drum and peeling it off. It is obtained. It can also be obtained by depositing copper on the surface of the rolled copper foil by an electrolytic method.

  One side or both sides of the copper foil may be subjected to a roughening treatment or a surface treatment (for example, a chromate treatment having a thickness of about several nm to 1 μm, a base treatment such as Ti).

  Further, the following physical properties are desired for the current collector substrate (in which a multilayer carbon material layer is formed on the current collector).

(1) Average surface roughness (Ra)
The average surface roughness (Ra) of the active material layer (ie, multi-layer structure carbon material layer) forming surface of the current collector substrate defined by the method described in JIS B0601-1994 is not particularly limited, but is usually 0.01 μm or more. The thickness is preferably 0.03 μm or more, usually 1.5 μm or less, preferably 1.3 μm or less, particularly preferably 1.0 μm or less.

  In the non-aqueous secondary battery obtained by using the current collector substrate by setting the average surface roughness (Ra) of the active material layer forming surface of the current collector substrate within the range between the lower limit and the upper limit. Good charge / discharge cycle characteristics can be expected.

  By setting it to the above lower limit or more, the area of the interface between the current collector and the active material layer is increased, and the adhesion between them is improved. The upper limit of the average surface roughness (Ra) is not particularly limited, but those having an average surface roughness (Ra) exceeding 1.5 μm are generally difficult to obtain as a thin film having a practical thickness as a battery. 1.5 μm or less is preferable.

(2) Tensile strength The tensile strength of the current collector substrate is not particularly limited, but is usually 50 N / mm ² or more, preferably 100 N / mm ² or more, and more preferably 150 N / mm ² or more. The tensile strength is obtained by dividing the maximum tensile force required until the test piece breaks by the cross-sectional area of the test piece. The tensile strength in the present invention is measured by the same method and apparatus as the elongation measurement.

  If the current collector substrate has a high tensile strength, cracking of the current collector substrate due to expansion / contraction of the active material layer accompanying charging / discharging can be suppressed, and good cycle characteristics can be obtained.

(3) 0.2% proof stress of 0.2% proof stress current collector substrate is not particularly limited, normally 30 N / mm ² or more, preferably 100 N / mm ² or more, particularly preferably 150 N / mm ² or more . The 0.2% proof stress is the magnitude of the load required to give 0.2% plastic (permanent) strain. It means that you are doing.

  The 0.2% proof stress in the present invention is measured by the same method and apparatus as the elongation rate measurement. If the current collector substrate has a high 0.2% proof stress, plastic deformation of the current collector substrate due to expansion / contraction of the active material layer accompanying charging / discharging can be suppressed, and good cycle characteristics can be obtained. it can.

(4) Thickness of current collector The thickness of the current collector is arbitrary, but is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more. Moreover, an upper limit is 1 mm normally, Preferably it is 100 micrometers, More preferably, it is 30 micrometers.

  If the thickness of the current collector is less than 1 μm, the strength is lowered, so that it is difficult to apply the multilayer structure carbon material-containing slurry, which may be undesirable in the process. On the other hand, if it is thicker than 1 mm, it may be difficult to change the shape of the electrode, such as winding, in the process. The current collector may be mesh.

(5) Thickness ratio between current collector and active material layer The ratio between the current collector and the thickness of the active material layer formed on the current collector (the layer containing the multilayered carbon material of the present invention) is particularly limited. However, the value of (thickness of active material layer on one side immediately before electrolyte injection) / (thickness of current collector) is 150 or less, preferably 20 or less, more preferably 10 or less, and the lower limit is 0. .1 or more, preferably 0.4 or more, more preferably 1 or more. Above this range, the current collector may generate heat due to Joule heat during high current density charge / discharge. On the other hand, below this range, the volume ratio of the current collector to the multilayer structure carbon material may increase, and the battery capacity may decrease.

(6) Electrode density The electrode structure of the multi-layer structure carbon material of the present invention is not particularly limited, but the density of the active material present on the current collector is preferably 1 g / cm ³ or more. More preferably 1.1 g / cm ³ , still more preferably 1.2 g / cm ³ or more, and the upper limit is usually 2 g / cm ³ , preferably 1.9 g / cm ³ , more preferably 1.8 g / cm ³ . ³ and more preferably 1.7 g / cm ³ .

  If this range is exceeded, the active material particles are destroyed during rolling to achieve electrode density, the initial irreversible capacity of the non-aqueous secondary battery is increased, and the electrolyte solution near the current collector / active material interface The permeability may decrease and may lead to high current density charge / discharge characteristics of the battery. On the other hand, if the amount is less than the above range, the conductivity between the active materials decreases, the battery resistance increases, and the capacity per unit volume may decrease.

(7) Electrode orientation ratio The electrode orientation ratio of the negative electrode is usually 0.01 or more, preferably 0.05 or more, more preferably 0.10 or more, and the upper limit is 0.67 which is a theoretical value. Below this range, the high-density charge / discharge characteristics of the non-aqueous secondary battery may deteriorate.

  The measuring method of the electrode plate orientation ratio is as follows. About the negative electrode after pressing to the target density, the active material orientation ratio of the electrode is measured by X-ray diffraction. The specific method is not particularly limited, but as a standard method, peak separation is performed by fitting the peaks of (110) and (004) diffraction of carbon by X-ray diffraction using asymmetric Pearson VII as a profile function. The integrated intensities of the peaks of (110) diffraction and (004) diffraction are calculated. From the obtained integrated intensity, a ratio represented by (110) diffraction integrated intensity / (004) diffraction integrated intensity is calculated and defined as the active material orientation ratio of the electrode.

The X-ray diffraction measurement conditions here are as follows. “2θ” indicates a diffraction angle.
-Target: Cu (Kα ray) graphite monochromator-Slit: Divergence slit = 1 degree, Receiving slit = 0.1 mm, Scattering slit = 1 degree-Measurement range and step angle / measurement time:
(110) plane: 76.5 degrees ≦ 2θ ≦ 78.5 degrees 0.01 degrees / 3 seconds (004) plane: 53.5 degrees ≦ 2θ ≦ 56.0 degrees 0.01 degrees / 3 seconds Sample preparation: glass Fix the electrode to the plate with double-sided tape with a thickness of 0.1 mm

(8) Impedance The resistance of the negative electrode when charged from the discharged state to 60% of the nominal capacity is preferably 100Ω or less, particularly preferably 50Ω or less, more preferably 20Ω or less, and / or the double layer capacity is 1 ×. It is preferably 10 ⁻⁶ F or more, particularly preferably 1 × 10 ⁻⁵ F or more, more preferably 1 × 10 ⁻⁴ F or more. Within this range, the output characteristics of the nonaqueous secondary battery are good and preferable.

  The resistance and double layer capacity of the negative electrode are measured by the following procedure. As a non-aqueous secondary battery to be measured, the nominal capacity is charged at a current value that can be charged in 5 hours, and then maintained for 20 minutes without charging / discharging, and then the nominal capacity can be discharged in 1 hour. The capacity when discharged at 80% or more of the nominal capacity is used.

  The non-aqueous secondary battery in the above-described discharge state is charged to 60% of the nominal capacity at a current value that can be charged in 5 hours, and immediately the non-aqueous secondary battery is transferred into a glove box under an argon gas atmosphere. Here, the non-aqueous secondary battery is quickly disassembled and taken out in a state where the negative electrode does not discharge or short-circuit, and if it is a double-sided coated electrode, the electrode active material on one side is peeled off without damaging the electrode active material on the other side. Two electrodes are punched to 12.5 mmφ, and are opposed to each other so that the active material surface does not shift through a separator.

60 μL of the electrolytic solution used in the battery is dropped and adhered between the separator and both negative electrodes, and kept in a state where it is not in contact with the outside air, the current collectors of both negative electrodes are made conductive, and the AC impedance method is performed. The measurement was performed at a temperature of 25 ° C., and the complex impedance measurement was performed in a frequency band of 10 ⁻² to 10 ⁵ Hz. And double layer capacity | capacitance (Cdl) is calculated | required.

<Binder>
The binder for binding the active material (multi-layer structure carbon material) is not particularly limited as long as it is a material that is stable with respect to the electrolyte and the solvent used when manufacturing the electrode. Specifically, resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, cellulose, nitrocellulose; SBR (styrene / butadiene rubber), isoprene rubber, butadiene rubber, fluorine rubber, NBR ( Acrylonitrile-butadiene rubber), rubbery polymers such as ethylene / propylene rubber; styrene / butadiene / styrene block copolymers and hydrogenated products thereof; EPDM (ethylene-propylene-diene terpolymer), styrene / ethylene / Thermoplastic elastomeric polymers such as butadiene / styrene copolymer, styrene / isoprene / styrene block copolymer and hydrogenated products thereof; syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene / vinegar Soft resinous polymers such as vinyl copolymers and propylene / α-olefin copolymers; fluorinated polymers such as polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene / ethylene copolymers Molecule: a polymer composition having ion conductivity of alkali metal ions (particularly lithium ions), and the like. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and ratios.

  The solvent for forming the slurry is not particularly limited as long as it is a solvent capable of dissolving or dispersing the active material, binder, thickener and conductive agent used as necessary. 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-dimethylaminopropylamine, tetrahydrofuran (THF), toluene, acetone, diethyl ether, dimethylacetamide, hexamethylphosphamide, dimethylsulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane, etc. Can be mentioned.

  In particular, when an aqueous solvent is used, a dispersant or the like is added in addition to the above-described thickener, and a slurry is formed using a latex such as SBR. In addition, these may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and a ratio.

  The ratio of the binder to the 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, and the upper limit is usually 20% by mass, preferably 15% by mass, More preferably, it is 10 mass%, More preferably, it is 8 mass%.

  If this range is exceeded, the proportion of the binder that does not contribute to the battery capacity may increase and the battery capacity may decrease. On the other hand, if it is lower, the strength of the negative electrode is lowered, which may be undesirable in the battery production process.

  In particular, when a rubbery polymer typified by SBR is contained as a main component of the binder, the ratio of the binder to the active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably Is 0.6 mass% or more, and the upper limit is usually 5 mass%, preferably 3 mass%, more preferably 2 mass%.

  When a fluorine-based polymer typified by polyvinylidene fluoride is contained as the main component of the binder, the ratio of the binder to the active material is usually 1% by mass or more, preferably 2% by mass or more, more preferably 3%. The upper limit is usually 15% by mass, preferably 10% by mass, and more preferably 8% by mass.

  The 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.

  When a thickener is further added, the ratio of the thickener to the active material is usually 0.1% by mass or more, preferably 0.5% or more, more preferably 0.6% or more, and the upper limit is Usually 5 mass%, preferably 3 mass%, more preferably 2 mass%. Below this range, the applicability of the slurry may be significantly reduced. On the other hand, the ratio of the active material in the multi-layer structure carbon material layer may decrease, which may cause a problem that the capacity of the battery decreases and a problem that the resistance between the multi-layer structure carbon materials increases.

[Non-aqueous secondary battery]
Hereinafter, the non-aqueous secondary battery of the present invention will be described in detail.

<Battery shape>
The battery shape is not particularly limited, but examples thereof include a bottomed cylindrical shape, a bottomed square shape, a thin shape, a sheet shape, and a paper shape. When incorporating into a system or device, in order to increase the volumetric efficiency and improve the storage capacity, it may be of a different shape such as a horseshoe shape or a comb shape considering the fit in the peripheral system arranged around the battery. . From the viewpoint of efficiently releasing the heat inside the battery to the outside, a rectangular shape having at least one surface that is relatively flat and has a large area is preferable.

  In a battery having a bottomed cylindrical shape, since the outer surface area with respect to the power generating element to be filled becomes small, it is preferable to design so that Joule heat generated by the internal resistance at the time of charging and discharging efficiently escapes to the outside. Moreover, it is preferable to design so that the filling ratio of the substance having high thermal conductivity is increased and the temperature distribution inside is reduced.

In the bottomed square shape, the ratio of the area S of the largest surface (the product of the width and height of the outer dimensions excluding the terminal part, unit m ² ) to the thickness T (unit m) of the battery outer shape The 2S / T value is preferably 100 or more, and more preferably 200 or more. By increasing the maximum surface, it is possible to improve characteristics such as cycle performance and high-temperature storage even for high-power and large-capacity batteries, and increase the heat dissipation efficiency during abnormal heat generation. Can be prevented from becoming a dangerous state.

<Battery configuration>
The non-aqueous secondary battery of the present invention includes a positive electrode and a negative electrode capable of occluding and releasing lithium ions, and a non-aqueous electrolyte, and a separator disposed between the positive electrode and the negative electrode, a current collecting terminal, and Consists of an outer case and the like. A protective element may be attached inside the battery and / or outside the battery.

<Positive electrode>
The positive electrode in the non-aqueous secondary battery of the present invention is formed by forming an active material layer containing a positive electrode active material and an organic substance (binder) having a binding and thickening effect on a current collector, Usually, a positive electrode active material and a slurry in which the organic substance is dispersed in water or an organic solvent are thinly applied to the current collector and dried, followed by a pressing step of compacting to a predetermined thickness and density. It is formed.

The material of the positive electrode active material is not particularly limited as long as it has a function capable of occluding and releasing lithium ions. For example, lithium transition metal composites such as lithium cobalt oxide, lithium nickel oxide, and lithium manganese oxide can be used. Oxide materials; transition metal oxide materials such as manganese dioxide; carbonaceous materials such as fluorinated graphite can be used. Specifically, LiFeO ₂ , LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ and their non-stoichiometric compounds, MnO ₂ , TiS ₂ , FeS ₂ , Nb ₃ S ₄ , Mo ₃ S ₄ , CoS ₂ , V ₂ O ₅ , P ₂ O ₅ , CrO ₃ , V ₃ O ₃ , TeO ₂ , GeO _2, LiNi _0.33 Mn _0.33 Co _0.33 O _{2 and the} like can be used.

  A positive electrode conductive agent can be used for the positive electrode active material layer. The positive electrode conductive agent may be any electron conductive material that does not cause a chemical change at the charge / discharge potential of the positive electrode active material used.

  For example, natural graphite (such as flake graphite), graphite such as artificial graphite, carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, metal fiber, etc. Conductive fibers, metal powders such as carbon fluoride and aluminum, conductive whiskers such as zinc oxide and potassium titanate, conductive metal oxides such as titanium oxide, and organic conductive materials such as polyphenylene derivatives A single material or a mixture thereof can be used as the conductive agent for the positive electrode.

  Among these conductive agents, artificial graphite and acetylene black are particularly preferable. Although the addition amount of a electrically conductive agent is not specifically limited, 1-50 mass% is preferable with respect to positive electrode active material material, and 1-30 mass% is especially preferable. In the case of carbon or graphite, 2 to 15% by mass is particularly preferable.

There is no restriction | limiting in particular as an organic substance which has a binding and thickening effect used for formation of a positive electrode active material layer, Any of a thermoplastic resin and a thermosetting resin may be sufficient. Examples include polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene butadiene rubber, tetrafluoroethylene-hexafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer (FEP). ), Tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer (ETFE) Resin), polychlorotrifluoroethylene (PCTFE), vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylene copolymer, ethylene-chloro Trifluoroethylene copolymer (ECTFE), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene copolymer, ethylene-acrylic acid copolymer or the above-mentioned (Na ⁺ ) ion cross-linked product of material, ethylene-methacrylic acid copolymer or (Na ⁺ ) ion cross-linked product of material, ethylene-methyl acrylate copolymer, or (Na ⁺ ) ion cross-linked product of material, ethylene -A methyl methacrylate copolymer or the (Na ^<+> ) ion bridge | crosslinking body of the said material can be mentioned, These materials can be used individually or as a mixture.

  Among these materials, more preferable materials are polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE).

  In addition to the conductive agent described above, the positive electrode active material layer may further contain a filler, a dispersant, an ionic conductor, a pressure enhancer, and other various additives. As the filler, any fibrous material that does not cause a chemical change in the constructed battery can be used. Usually, olefin polymers such as polypropylene and polyethylene, fibers such as glass and carbon are used. Although the addition amount of a filler is not specifically limited, 0-30 mass% is preferable as content in an active material layer.

  In preparing the positive electrode active material slurry, an aqueous solvent or an organic solvent is used as a dispersion medium. As the aqueous solvent, water is usually used, and additives such as alcohols such as ethanol and cyclic amides such as N-methylpyrrolidone may be added to water up to about 30% by mass or less. it can.

  The organic solvent is usually a cyclic amide such as N-methylpyrrolidone, a linear amide such as N, N-dimethylformamide or N, N-dimethylacetamide, or an aromatic such as anisole, toluene or xylene. Examples include hydrocarbons, alcohols such as butanol and cyclohexanol, among which cyclic amides such as N-methylpyrrolidone, linear amides such as N, N-dimethylformamide and N, N-dimethylacetamide, and the like. preferable.

  A positive electrode active material, a binder as a binder, an organic substance having a thickening effect, a positive electrode conductive agent blended as necessary, and other fillers are mixed in these solvents to prepare a positive electrode active material slurry, The positive electrode active material layer is formed by applying this to the positive electrode current collector so as to have a predetermined thickness.

  The upper limit of the concentration of the positive electrode active material in the positive electrode active material slurry is usually 70% by mass, preferably 55% by mass, and the lower limit is usually 30% by mass, preferably 40% by mass. If the concentration of the positive electrode active material exceeds this upper limit, the positive electrode active material in the positive electrode active material slurry tends to aggregate, and if it falls below the lower limit, the positive electrode active material tends to settle during storage of the positive electrode active material slurry.

  Further, the upper limit of the concentration of the binder in the positive electrode active material slurry is usually 30% by mass, preferably 10% by mass, and the lower limit is usually 0.1% by mass, preferably 0.5% by mass. If the concentration of the binder exceeds this upper limit, the internal resistance of the resulting positive electrode may increase, and if it falls below the lower limit, the binding property of the positive electrode active material layer may be inferior.

  For the positive electrode current collector, for example, it is preferable to use a valve metal or an alloy thereof that forms a passive film on the surface by anodic oxidation in an electrolytic solution. Examples of the valve metal include metals belonging to Groups 4, 5, and 13 of the periodic table and alloys thereof. Specifically, Al, Ti, Zr, Hf, Nb, Ta and alloys containing these metals can be exemplified, and Al, Ti, Ta and alloys containing these metals can be preferably used. . In particular, Al and its alloys are desirable because of their light weight and high energy density. The thickness of the positive electrode current collector is not particularly limited, but is usually about 1 to 50 μm.

<Non-aqueous electrolyte>
As the electrolytic solution used in the present invention, for example, a solution obtained by dissolving a solute in a non-aqueous solvent can be used. As the solute, an alkali metal salt, a quaternary ammonium salt, or the like can be used. Specifically, LiClO ₄ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (CF ₃ CF ₂ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ), LiC (CF ₃ SO ₂ ) _{3 and the} like are preferably used. One kind of these solutes may be selected and used, or two or more kinds may be mixed and used.

  The content of these solutes in the electrolytic solution is usually 0.2 mol / L or more, preferably 0.5 mol / L or more, and usually 2 mol / L or less, preferably 1.5 mol / L or less.

  Examples of the non-aqueous solvent include cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate and vinylene carbonate, cyclic ester compounds such as γ-butyrolactone; chain ethers such as 1,2-dimethoxyethane; crown ethers, 2 -Cyclic ethers such as methyltetrahydrofuran, 1,2-dimethyltetrahydrofuran, 1,3-dioxolane, tetrahydrofuran; chain carbonates such as diethyl carbonate, ethyl methyl carbonate, dimethyl carbonate, and the like can be used. Among these, a nonaqueous solvent containing a cyclic carbonate and a chain carbonate is preferable.

  One type of these non-aqueous solvents may be selected and used, or two or more types may be mixed and used.

  The non-aqueous electrolyte used in the present invention may contain various auxiliary agents such as cyclic carbonates having unsaturated bonds in the molecule and conventionally known overcharge inhibitors, deoxidizers, and dehydrants. Good.

  Examples of the cyclic carbonate having an unsaturated bond in the molecule include vinylene carbonate compounds, vinyl ethylene carbonate compounds, methylene ethylene carbonate compounds, and the like.

  Examples of the vinylene carbonate-based compound include vinylene carbonate, methyl vinylene carbonate, ethyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, 4,5-diethyl vinylene carbonate, fluorovinylene carbonate, trifluoromethyl vinylene carbonate, and the like. .

  Examples of the vinyl ethylene carbonate compound include vinyl ethylene carbonate, 4-methyl-4-vinyl ethylene carbonate, 4-ethyl-4-vinyl ethylene carbonate, 4-n-propyl-4-vinyl ethylene carbonate, 5-methyl. Examples include -4-vinylethylene carbonate, 4,4-divinylethylene carbonate, 4,5-divinylethylene carbonate, and the like.

  Examples of the methylene ethylene carbonate compound include methylene ethylene carbonate, 4,4-dimethyl-5-methylene ethylene carbonate, 4,4-diethyl-5-methylene ethylene carbonate, and the like.

  Of these, vinylene carbonate and vinyl ethylene carbonate are preferable, and vinylene carbonate is particularly preferable.

  A suitable example is a difluorophosphate such as lithium difluorophosphate.

  These may be used individually by 1 type, or may use 2 or more types together.

  When the non-aqueous electrolyte contains a cyclic carbonate compound having an unsaturated bond in the molecule, the proportion in the non-aqueous electrolyte is usually 0.01% by mass or more, preferably 0.1% by mass or more, particularly Preferably it is 0.3 mass% or more, Most preferably, it is 0.5 mass% or more, Usually 8 mass% or less, Preferably it is 4 mass% or less, Most preferably, it is 3 mass% or less.

  By including in the electrolyte a cyclic carbonate having an unsaturated bond in the molecule, the cycle characteristics of the battery can be improved. The reason is not clear, but it is presumed that a stable protective film can be formed on the surface of the negative electrode. However, when the content is small, this property is not sufficiently improved. However, if the content is too high, the amount of gas generated tends to increase during high-temperature storage, so the content in the non-aqueous electrolyte is preferably in the above range.

  Examples of the overcharge inhibitor include aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, and dibenzofuran; Partially fluorinated products of the above aromatic compounds such as fluorobiphenyl, o-cyclohexylfluorobenzene, p-cyclohexylfluorobenzene, and the like, including 2,4-difluoroanisole, 2,5-difluoroanisole and 2,6-difluoroanisole Examples thereof include a fluorine anisole compound.

  These may be used alone or in combination of two or more.

  The ratio of the overcharge inhibitor in the non-aqueous electrolyte is usually 0.1 to 5% by mass. By containing an overcharge inhibitor, rupture / ignition of the nonaqueous secondary battery can be suppressed during overcharge or the like.

  Examples of other auxiliaries include carbonate compounds such as fluoroethylene carbonate, trifluoropropylene carbonate, phenylethylene carbonate, erythritan carbonate, spiro-bis-dimethylene carbonate, methoxyethyl-methyl carbonate; succinic anhydride, glutar anhydride Carboxylic acid anhydrides such as acid, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, diglycolic anhydride, cyclohexanedicarboxylic anhydride, cyclopentanetetracarboxylic dianhydride and phenylsuccinic anhydride; Ethylene sulfite, 1,3-propane sultone, 1,4-butane sultone, methyl methanesulfonate, busulfan, sulfolane, sulfolene, dimethyl sulfone and tetramethylthiurammo Sulfur-containing compounds such as sulfide, N, N-dimethylmethanesulfonamide, N, N-diethylmethanesulfonamide; 1-methyl-2-pyrrolidinone, 1-methyl-2-piperidone, 3-methyl-2-oxazolidinone, 1 , 3-dimethyl-2-imidazolidinone and nitrogen-containing compounds such as N-methylsuccinimide; hydrocarbon compounds such as heptane, octane and cycloheptane; fluorobenzene, difluorobenzene, hexafluorobenzene, benzotrifluoride, etc. And fluorine-containing aromatic compounds.

  These may be used alone or in combination of two or more.

  The ratio of these auxiliaries in the nonaqueous electrolytic solution is usually 0.1 to 5% by mass. By containing these auxiliaries, capacity maintenance characteristics and cycle characteristics after high-temperature storage of the battery can be improved.

  Further, the non-aqueous electrolyte solution may contain an organic polymer compound in the electrolyte solution, and may be a gel, rubber, or solid sheet solid electrolyte. In this case, specific examples of the organic polymer compound include polyether polymer compounds such as polyethylene oxide and polypropylene oxide; crosslinked polymers of polyether polymer compounds; vinyl alcohol polymers such as polyvinyl alcohol and polyvinyl butyral. Molecular compounds; Vinyl alcohol-based polymer compounds insolubilized; Polyepichlorohydrin; Polyphosphazenes; Polysiloxanes; Vinyl-based polymer compounds such as polyvinylpyrrolidone, polyvinylidene carbonate, polyacrylonitrile; Poly (ω-methoxyoligooxyethylene methacrylate) And polymer copolymers such as poly (ω-methoxyoligooxyethylene methacrylate-co-methyl methacrylate).

<Separator>
The separator used in the non-aqueous secondary battery of the present invention has a predetermined mechanical strength that electrically insulates both electrodes, has a high ion permeability, and has an oxidization property on the side in contact with the positive electrode and a negative electrode side. There is no particular limitation as long as it has resistance to reducibility.

  As a material for the separator having such required characteristics, a resin, an inorganic material, glass fiber, or the like is used.

  As the resin, olefin polymer, fluorine polymer, cellulose polymer, polyimide, nylon and the like are used. Specifically, it is preferable to select from materials that are stable with respect to the electrolytic solution and have excellent liquid retention properties, and it is preferable to use a porous sheet or a nonwoven fabric made of a polyolefin such as polyethylene or polypropylene.

  As the inorganic substance, 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, and those having a particle shape or fiber shape are 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 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 a fluororesin as a binder on alumina particles having a 90% particle size of less than 1 μm on both surfaces of the positive electrode.

  The non-aqueous electrolyte used in the present invention is effective in reducing the reaction resistance related to the desorption / insertion of lithium ions into the electrode active material, which is considered to be a factor that can realize good low-temperature discharge characteristics. . However, it has been found that a battery having a large direct current resistance is inhibited by the direct current resistance and the effect of reducing the reaction resistance cannot be reflected 100% on the low temperature discharge characteristics. By using a battery having a small DC resistance component, this can be improved, and the effect of the non-aqueous electrolyte can be sufficiently exhibited.

<Exterior case>
The outer case is not particularly limited as long as it is a stable substance with respect to the non-aqueous electrolyte used. Specifically, for example, a nickel-plated steel plate, stainless steel, aluminum, an aluminum alloy, a magnesium alloy or other metal, 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.

  As the exterior case using the metals, laser welding, resistance welding, ultrasonic welding, metals are welded together to form a sealed sealed structure, or a caulking structure using the metals via a resin gasket Are listed.

  Examples of the exterior case using the laminate film include those having a sealed and sealed structure by heat-sealing resin layers. In order to improve the sealing performance, a resin different from the resin used for the laminate film may be interposed between the resin layers. In particular, when the resin layer is heat-sealed through a current collecting terminal to form a sealed structure, since the metal and the resin are joined, a modification having a polar group or a polar group introduced as the intervening resin Resins are preferably used.

<Protective element>
As a protective element that is a component of the non-aqueous secondary battery of the present invention, a PTC (Positive Temperature Coefficient) thermistor whose resistance increases when abnormal heat generation or excessive current flows, a temperature fuse, a battery internal pressure during abnormal heat generation And a valve (current cutoff valve) that cuts off the current flowing in the circuit due to a sudden rise in internal temperature.

  It is preferable to select a protection element that does not operate under normal use at a high current. From the viewpoint of high output, the battery should be designed so that it does not cause abnormal heat generation or thermal runaway even without a protection element. More preferred.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further more concretely, this invention is not limited to these Examples, unless the summary is exceeded.

  The various properties of graphite used in the following examples and comparative examples are shown in Table 1 below. These graphites were produced based on the method described in this specification and a known method.

[Example 1]
Spherical natural graphite (A) was used as graphite particles, cracked petroleum heavy oil obtained during naphtha pyrolysis was mixed as a low crystalline carbon precursor, and heat treatment was performed at 1300 ° C. in an inert gas. The obtained fired product was pulverized and classified to obtain a negative electrode material 1. The amount of amorphous carbon added to the obtained multilayer structure carbon material powder was 2.6% by mass.

[Example 2]
A negative electrode material 2 was obtained in the same manner as in Example 1 except that the amount of amorphous carbon added was 1.4% by mass.

[Example 3]
A negative electrode material 3 was obtained in the same manner as in Example 1 except that the amount of amorphous carbon added was 0.6% by mass.

[Example 4]
A negative electrode material 4 was obtained in the same manner as in Example 1 except that spheroidized natural graphite (B) was used as the graphite particles and the amount of amorphous carbon added was 2.7% by mass.

[Example 5]
A negative electrode material 5 was obtained in the same manner as in Example 4 except that the amount of amorphous carbon added was 1.9% by mass.

[Example 6]
A negative electrode material 6 was obtained in the same manner as in Example 1 except that spheroidized natural graphite (C) was used as the graphite particles and the amount of amorphous carbon added was 2.4% by mass.

[Example 7]
A negative electrode material 7 was obtained in the same manner as in Example 6 except that the amount of amorphous carbon added was 1.2% by mass.

[Comparative Example 1]
A negative electrode material 8 was obtained in the same manner as in Example 4 except that the amount of amorphous carbon added was 4.4% by mass.

[Comparative Example 2]
A negative electrode material 9 was obtained in the same manner as in Example 1 except that spheroidized natural graphite (D) was used as the graphite particles and the amount of amorphous carbon added was 12% by mass.

[Comparative Example 3]
A negative electrode material 10 was obtained in the same manner as in Example 1 except that spheroidized natural graphite (E) was used as the graphite particles and the amount of amorphous carbon added was 3.9% by mass.

[Comparative Example 4]
A negative electrode material 11 was obtained in the same manner as in Example 1 except that spheroidized natural graphite (F) was used as the graphite particles and the amount of amorphous carbon added was 1.8% by mass.

[Comparative Example 5]
A negative electrode material 12 was obtained in the same manner as in Example 1 except that scale natural graphite (G) was used as the graphite particles and the amount of amorphous carbon added was 2.7 mass%.

[Comparative Example 6]
Negative electrode material 13 was obtained in the same manner as in Example 1, except that scale natural graphite (H) was used as the graphite particles and the amount of amorphous carbon added was 1.9% by mass.

[Comparative Example 7]
Spherical natural graphite (B) was used as the negative electrode material 14 as it was.

[Production of non-aqueous secondary battery]
<Preparation of negative electrode sheet>
Using the negative electrode materials produced in the above Examples and Comparative Examples as a negative electrode material, an electrode plate having a negative electrode active material layer with a negative electrode active material layer density of 1.60 ± 0.03 g / cm ³ was produced. Specifically, 20.00 ± 0.02 g of a negative electrode material, 20.00 ± 0.02 g of a 1% by mass aqueous solution of carboxymethylcellulose sodium salt (0.200 g in terms of solid content), and styrene having a weight average molecular weight of 270,000 -Aqueous dispersion of butadiene rubber 0.50 ± 0.05 g (0.2 g in terms of solid content) was added, stirred with a hybrid mixer manufactured by Keyence for 5 minutes, and defoamed for 30 seconds to obtain a slurry.

The slurry was applied to a width of 5 cm using a doctor blade so that the negative electrode material was attached in an amount of 12.0 ± 0.3 mg / cm ² on a 18 μm thick copper foil as a current collector, Air drying was performed at room temperature. 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 negative electrode active material layer to be 1.60 ± 0.03 g / cm ³ to obtain an electrode sheet.

<Preparation of non-aqueous secondary battery (2016 coin type battery)>
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 the two electrodes, a separator (porous polyethylene film) impregnated with an electrolytic solution in which LiPF ₆ was dissolved at 1 mol / L in a mixed solvent of ethylene carbonate and ethyl methyl carbonate (volume ratio = 3: 7). Made), and 2016 coin type batteries were respectively produced.

[Evaluation]
<Plate strength>
The negative electrode sheet produced by the above method is cut to a width of 20 mm, and is attached to a test SUS plate with a double-sided tape (the active material layer side is attached with a double-sided tape surface) and fixed in the horizontal direction, and the end of the negative electrode sheet is Clamped in the universal testing machine. In this state, the negative electrode sheet fixing portion of the universal testing machine was lowered in the vertical direction, and the negative electrode sheet was peeled off by pulling it from the double-sided tape at an angle of 90 degrees. At this time, the average value of the load applied between the negative electrode sheet and the double-sided tape was measured, and the value divided by the negative electrode sheet sample width (20 mm) was defined as the electrode plate strength value (mN / mm).

<Initial irreversible capacity, initial efficiency>
Using the non-aqueous secondary battery (2016 coin-type battery), the initial irreversible capacity and initial efficiency during battery charging / discharging were measured by the following measurement method.

After charging to 5 mV with respect to the lithium counter electrode at a current density of 0.16 mA / cm ² , and further charging until the charge capacity value becomes 350 mAh / g at a constant voltage of 5 mV, after doping lithium in the negative electrode, 0 The battery was discharged to 1.5 V with respect to the lithium counter electrode at a current density of .33 mA / cm ² .

  Subsequently, the second and third times were charged at 10 mV and 0.005 Ccut by cc-cv charging at the same current density, and the discharge was discharged to 1.5 V at 0.04 C at all times. The sum of the difference between the charge capacity and the discharge capacity of the total three cycles was calculated as the initial irreversible capacity. Further, the discharge capacity at the third cycle was defined as the discharge capacity of the material, the discharge capacity at the third cycle / (discharge capacity at the third cycle + initial irreversible capacity), and the initial efficiency.

As a result of the above measurement, the linear pressure (kg / 5 cm) required for rolling so that the density of the negative electrode active material layer was 1.6 g / cm ³ , and Examples 1 to 7 and Comparative Examples 1 to 7 The particle diameters (d50, d90, d10), the circularity, the rolling load (P), the specific surface area, and the tap density of the negative electrode materials 1 to 14 are shown in Table 2 below.

Claims (7)

A multilayer carbon material for a non-aqueous secondary battery, characterized in that at least a part of the surface of the graphite particles is coated with a carbonaceous material and satisfies the following conditions (1) to (3):
(1) The average particle diameter d50 of the multi-layer structure carbon material is 19.1 μm or more and 50 μm or less (2) The circularity of the multi-layer structure carbon material is 0.88 or more (3) The ratio (P / d50) between the rolling load (P) and d50 of the multilayer carbon material is 30 or less:
P = (collecting negative electrode active material using the multi-layer structure carbon material and containing 1% by mass of carboxymethyl cellulose sodium salt and 1% by mass of styrene-butadiene rubber as a binder with respect to the multi-layer structure carbon material. A negative electrode active material layer deposited on the negative electrode active material layer in an amount of 12.0 mg / cm ² was prepared, and the linear pressure (kg / kg) required to roll the negative electrode active material layer to a density of 1.6 g / cm ^3. 5 cm)). The multi-layer structure carbon material for a non-aqueous secondary battery has a tap density of 0.8 g / cm ³ or more and 1.30 g / cm ³ or less. Layered carbon material. The specific surface area measured by the BET method of the multilayer structure carbon material for non-aqueous secondary batteries is 0.2 m ² / g or more and 4.5 m ² / g or less. Multi-layer carbon material for non-aqueous secondary batteries.   The multilayered carbon material for a non-aqueous secondary battery according to any one of claims 1 to 3, wherein the graphite particles have a Raman R value of 0.1 or more and 0.6 or less. A multilayer carbon material for a non-aqueous secondary battery, characterized in that at least a part of the surface of the graphite particles is coated with a carbonaceous material and satisfies the following conditions (1) to (3):
(1) The average particle diameter d50 of the multilayer carbon material is 19.1 μm or more and 50 μm or less. (2) The circularity of the multilayer carbon material is 0.88 or more. (3) The carbon in the multilayer carbon material The amount of the adhering material is 0.01 or more and 2.7% by mass or less.   A negative electrode for a non-aqueous secondary battery comprising a current collector and a multilayer structure carbon material layer formed on the current collector, wherein the multilayer structure carbon material layer is any one of claims 1 to 5. A negative electrode for a non-aqueous secondary battery, comprising the multilayered carbon material for a non-aqueous secondary battery according to claim 1.   It is a non-aqueous secondary battery provided with the positive electrode and negative electrode which can occlude / release lithium ion, and non-aqueous electrolyte, Comprising: The said negative electrode is a negative electrode for non-aqueous secondary batteries of Claim 6. Non-aqueous secondary battery.