JP6678446B2 - Battery active material, battery electrode, non-aqueous electrolyte battery, battery pack, and vehicle using the same - Google Patents

Description

An embodiment of the present invention relates to a battery active material, a battery electrode, a nonaqueous electrolyte battery, a battery pack, and a vehicle using the same .

  2. Description of the Related Art In recent years, various portable electronic devices have been spreading due to rapid development of technology for miniaturizing electronic devices. In addition, there is a demand for miniaturization of a battery as a power source of these portable electronic devices, and a non-aqueous electrolyte secondary battery having a high energy density has attracted attention.

  Non-aqueous electrolyte secondary batteries that use metallic lithium as the negative electrode active material have a very high energy density, but have a short battery life because dendrites called dendrites precipitate on the negative electrode during charging. There was also a problem in safety, such as growth and reaching the positive electrode, causing an internal short circuit. Therefore, as a negative electrode active material instead of lithium metal, a carbon material capable of inserting and extracting lithium, particularly graphitic carbon, has come to be used.

    Attempts have been made to use materials having a large lithium storage capacity and a high density, such as elements that alloy with lithium, such as silicon and tin, as well as amorphous chalcogen compounds, as negative electrode active materials pursuing higher energy density. Have been. Above all, silicon can store lithium up to a ratio of 4.4 lithium atoms to one silicon atom, and the negative electrode capacity per mass is about ten times that of graphite carbon. However, silicon has a large change in volume due to insertion and desorption of lithium in a charge and discharge cycle, and has a problem in cycle life such as pulverization of active material particles.

  In order to solve the above-mentioned problems, it has been studied to increase the capacity and improve the cycle characteristics by using an active material in which silicon-containing particles and a carbonaceous material are combined. However, even with such an active material, compatibility between high capacity and cycle characteristics is insufficient, and further improvement in capacity and compatibility with cycle characteristics are required.

JP 2004-119176 A

  An object of the embodiment is to provide an active material for a battery that can obtain a nonaqueous electrolyte battery having excellent cycle life when used in a nonaqueous electrolyte battery.

  The present inventors have thought that the properties of the carbonaceous material in the active material in which the silicon-containing particles and the carbonaceous material have been conventionally studied are greatly affected by the life characteristics, and the characteristics of the carbonaceous material and the cycle characteristics Considered the relationship.

The active material for a battery according to the embodiment is an active material including a carbonaceous material and a metal or an oxide of the metal, which is Si dispersed in the carbonaceous material, and pores observed from a cross section of the active material. Has an area ratio of not less than 2% and not more than 16%, and has a dispersity of 0.7 or less , which is a value obtained by dividing a standard deviation of a distance between centers of gravity of the holes by an average of distances between centers of gravity of the holes . The average pore diameter of the pores is 200 nm or less .

It is a key map of the electrode for nonaqueous electrolyte batteries of a 2nd embodiment. It is a key map of a nonaqueous electrolyte battery concerning a 3rd embodiment. It is an expansion conceptual diagram of the nonaqueous electrolyte battery concerning a 4th embodiment. It is a key map of a battery pack concerning a 4th embodiment. It is a block diagram showing the electric circuit of the battery pack concerning a 4th embodiment. 9 is a cross-sectional electron microscope image of the active material according to Example 2. 9 is a cross-sectional electron microscope image of the active material according to Comparative Example 2.

  Hereinafter, embodiments will be described. Note that the same reference numerals are given to the same components throughout the embodiments, and redundant description will be omitted. In addition, each drawing is a schematic diagram for promoting the explanation and understanding of the embodiment, and the shape, dimensions, ratio, and the like are different from those of an actual device. In consideration of the above, the design can be appropriately changed.

(1st Embodiment)
The battery active material according to the first embodiment (hereinafter also referred to as “active material”) is a carbonaceous material and an active material composed of a metal or an oxide of the metal dispersed in the carbonaceous material. The area ratio of pores observed from the cross section of the active material is 2% or more and 16% or less, and is a value obtained by dividing the standard deviation of the distance between the centers of gravity of the holes by the average of the distance between the centers of gravity of the holes. The degree of dispersion is 0.7 or less.

  Hereinafter, as an explanation of the embodiment, an active material used for an active material mixture layer of a negative electrode of a nonaqueous electrolyte battery will be described. However, the active material of the embodiment is also used for an active material used for an active material mixture layer of a positive electrode. Can be. The metal used in the embodiment performs insertion and desorption of lithium, and is at least one selected from Si, Sn, Al, In, Ga, Pb, Ti, Ni, Mg, W, Mo, and Fe. Can be used. These may be one kind or an alloy of two or more kinds of metals. Further, even an oxide of this metal or metal alloy can be used in the same manner as a metal or metal alloy. The reason why these metals, alloys, metal oxides, and metal alloy oxides are selected is that the amount of occluded Li is large and the capacity can be increased. Among these elements, Si (silicon) is particularly preferable.

  Hereinafter, silicon will be described as an example of the metal element.

  Silicon includes crystalline silicon. Specific examples of the active material for a battery include composite particles having a silicon oxide phase in a carbonaceous substance and a silicon phase having crystalline silicon in the silicon oxide phase. The silicon oxide phase of the active material for a battery is dispersed in a carbonaceous material, and is composited with the carbonaceous material. Further, the silicon phase is dispersed in the silicon oxide phase and is composited with the silicon oxide phase.

The average primary particle size of the active material is, for example, 0.5 μm or more and 100 μm or less, and the BET specific surface area is 0.5 m ² / g or more and 40 m ² / g or less. The particle size and specific surface area of the active material affect the speed of the lithium insertion / desorption reaction and have a large effect on the negative electrode characteristics. However, if the value is within this range, the characteristics can be exhibited stably. . The average primary particle size of the active material is preferably 0.5 μm or more and 50 μm or less, more preferably 1 μm or more and 30 μm or less. Further, the BET specific surface area is preferably from 0.5 m ² / g to 30 m ² / g, more preferably from 1 m ² / g to 15 m ² / g. The BET specific surface area is measured by a BET (Brunauer-Emmett-Teller) method.

  The silicon phase of the negative electrode active material has a large expansion and contraction when occluding and releasing lithium, and it is preferable that the silicon phase is dispersed as finely as possible in order to reduce the stress. As a specific example, it is preferable that the particles are dispersed with a particle size of 200 nm or less at most from a cluster having an average diameter of several nm.

During the carbonaceous material, and a silicon oxide phase, when the composite particles having a silicon phase, the having crystalline silicon in the silicon oxide phase, silicon oxide phase amorphous, but have a structure such as crystalline, It is preferable that the silicon phase is uniformly dispersed in the active material particles in a form of binding to and containing or retaining the silicon phase. However, the microcrystalline silicon held in silicon oxide, the charge and discharge during the growth of crystallite size advances combined with each other lithium after repeated volume change with storage and release, the capacity decrease and cause the initial charge and discharge efficiency Becomes Therefore, in the present invention, the growth of the crystallite size of microcrystalline silicon can be inhibited by making the size of the silicon oxide phase small and uniform, so that capacity deterioration due to charge / discharge cycles is suppressed, and the life characteristics are improved. The preferred average diameter size of the silicon oxide phase is in the range of 50 nm or more and 1000 nm or less. If it is larger than this range, the effect of suppressing the size growth of microcrystalline silicon cannot be obtained. In addition, when it is smaller than this range, it becomes difficult to disperse the silicon oxide phase during the preparation of the active material, and problems such as a decrease in rate characteristics and a decrease in initial charge / discharge capacity efficiency due to a decrease in conductivity as the active material are caused. Occurs. More preferably, it is 50 nm or more and less than 500 nm, and further preferably 50 nm or more and 200 nm or less. Within this range, particularly good life characteristics can be obtained.

  In order to obtain good characteristics as the whole active material, the size of the silicon oxide phase is preferably uniform. When the 16% cumulative diameter in the volume is d16% and the 84% cumulative diameter is d84%. The value of (standard deviation / average size) is preferably 1.0 or less with respect to the standard deviation represented by (d84% -d16%) / 2, and more preferably 0.5 or less. Lifetime characteristics can be obtained.

  The ratio of the silicon phase, the silicon oxide phase, and the carbonaceous material phase is preferably such that the total molar ratio of silicon and carbon in the silicon phase and the silicon oxide phase is in the range of 0.2 ≦ Si atoms / carbon atoms ≦ 2. . The quantitative relationship between the number of silicon atoms in the silicon phase and the number of silicon atoms in the silicon oxide phase is such that the molar ratio is 0.6 ≦ the number of silicon atoms in the silicon phase / the number of silicon atoms in the silicon oxide phase ≦ 1.5. This is desirable because capacity and good cycle characteristics can be obtained.

  Being silicon oxide means that a negative electrode including the active material of the embodiment is manufactured, and the prepared negative electrode is sliced by an ion milling method, and then a TEM-EDX method (TEM: Transmission Electron Microscope (transmission electron microscope)). EDX can be confirmed by using Energy Dispersive X-ray Spectrometry (energy dispersive X-ray spectroscopy).

  Specifically, silicon oxide particles and portions other than the silicon oxide particles are grasped by observing the inside of the active material with a TEM, and the element composition analysis of the silicon oxide particles is performed by point analysis using EDX. By such a method, it is possible to confirm even if the silicon oxide is amorphous. Suitable analysis conditions are, for example, an acceleration voltage of 200 kV and a beam diameter of about 1 nm. If Si and O are detected in ten or more point analyzes on one silicon oxide particle and the average of the molar ratio of O to Si is greater than 0 and 2 or less, the particle has the composition formula SiOx (0 It is determined that the particles are silicon oxide particles represented by <x ≦ 2). Ten points for performing the point analysis are randomly selected including the peripheral portion. For example, in a case where the surface of the silicon particles is oxidized to form a coating layer of silicon oxide, only the silicon portion is selected. To The particle size of such silicon oxide particles is determined by observing the active material by TEM as described above, and selecting at least 10 randomly selected silicon oxide particles from the obtained images. The average value of the sizes in the directions of is calculated. However, it is permissible to include silicon-containing particles outside of this particle size range to the extent that battery performance is not affected.

  When silicon is contained in the silicon oxide particles, the particles are preferably crystalline, and the particle diameter of the silicon particles is preferably 1 nm or more and 80 nm or less. Crystallinity is desirable because lithium insertion and desorption easily proceed. If it is smaller than 1 nm, it is likely to combine with other crystalline silicon in a charge / discharge cycle to grow grains, so that the cycle characteristics are likely to be deteriorated. If it is larger than 80 nm, lithium storage and release hardly occur in the entire crystalline silicon. The particle size of such crystalline silicon is determined by observing the active material by TEM as described above, and defining a portion of the silicon-containing particles where the crystal lattice of silicon is seen as crystalline silicon, and randomly selecting the obtained image. The average value of the sizes in 10 directions randomly selected for each of the 10 or more crystalline silicons is calculated. However, it is permissible to include crystalline silicon outside this particle size range to the extent that it does not affect battery performance.

  The half width of the diffraction peak of the Si (220) plane in the powder X-ray diffraction measurement of the active material is preferably 1.5 ° or more and 8.0 ° or less. The half value width of the diffraction peak of the Si (220) plane becomes smaller as the crystal grains of the silicon phase grow, and when the crystal grains of the silicon phase grow larger, the active material particles may crack due to expansion and contraction accompanying insertion and desorption of lithium. However, if the half width is in the range of 1.5 ° or more and 8.0 ° or less, such a problem can be avoided from being surfaced.

  The silicon phase expands and contracts as lithium is inserted and desorbed. With the expansion and contraction, when the phases are combined and the size of the phase becomes coarse, the cycle characteristics tend to deteriorate. In addition to the above, measures such as addition of cubic zirconia may be taken in order to prevent a decrease in cycle characteristics.

The silicon oxide phase of the first embodiment of the present invention reduces expansion and contraction of the silicon phase. Examples of the silicon oxide phase include a compound represented by a chemical formula of SiO _x (1 <x ≦ 2) having a structure such as amorphous, low crystalline, and crystalline.

Further, lithium silicate such as Li ₄ SiO ₄ may be dispersed on the surface or inside of the silicon oxide phase.

The SiO ₂ precursor and the lithium compound may be added to the structural carbonaceous material covering the silicon phase and the silicon oxide phase. By adding these substances to the carbonaceous material, the bond between SiO ₂ generated from silicon monoxide and the carbonaceous material is strengthened, and Li ₄ SiO ₄ having excellent lithium ion conductivity is generated in the silicon oxide phase. Examples of the SiO ₂ precursor include alkoxides such as silicon ethoxide. Examples of the lithium compound include lithium carbonate, lithium oxide, lithium hydroxide, lithium oxalate, lithium chloride, and the like. For example, by mixing the active material and a lithium salt and performing a heat treatment, a reaction between silicon oxide and the lithium salt can be caused to form lithium silicate. As the lithium salt, lithium hydroxide, lithium acetate, lithium oxide, lithium carbonate, and the like are preferable because the melting point is low or the reaction speed is high, so that the lithium salt easily forms uniformly with lithium silicate. The coating may contain other additives, for example, silicon carbide, phosphorus atoms, and boron atoms, from the viewpoint of maintaining the structure.

  The carbonaceous material phase in the active material is a resin-based organic material forming a furan resin, xylene resin, ketone resin, amino resin, melamine resin, urea resin, aniline resin, urethane resin, polyimide resin, polyester resin, epoxy resin, phenol resin, and the like. It is obtained by firing the material. Further, a naphthalene-based material may be added to these resin-based organic materials. This is because the addition of the naphthalene-based material has the advantage of improving the capacity and efficiency of the carbonaceous material component. Specifically, 1-naphthol, 2-naphthol, 3-methyl-1-naphthol, 3-methylnaphthalen-2-ol, 3-methoxy-2-naphthol, 1-amino-4-naphthol, 2-amino- 1-naphthol, 5-amino-1-naphthol, 6-amino-1-naphthol, 1- (dimethylaminomethyl) -2-naphthol, 5-amino-2-naphthol, 7-aminonaphthalen-2-ol, 8 -Methylnaphthalen-1-ol, 4-bromo-1-naphthol, 3-bromo-2-naphthol, 2,4-dibromo-1-naphthol, 1,6-dibromo-2-naphthol, 4-chloro-1- Naphthol, 2,4-dichloro-1-naphthol, 1-chloronaphthalen-2-ol, 6-amino-1-naphthol, 2-methylnaphthalen-1-ol, 4-methyl-1-naphthol, 5,6, 7,8-tetrahydro-1-naphthol, 1,2,3,4-tetrahydro-1-naphthol, 5,8-dihydro-1-naphthol, 4-methoxy-1-naphthol, 6-methoxy-1- 1-Naphthyl acetate, 1'-hydroxy-2'-acetonaphthone, 1-naphthaldehyde, 4- (dimethylamino) -1-naphthaldehyde, 2-naphthaldehyde, 1-naphthaleneacetonitrile, 1,3-naphthalene diol , 1,5-naphthalenediol, 2,7-naphthalenediol, 1,4-naphthalenediethanol, 2,3-naphthalenedimethanol, 1-naphthalenemethanol, 2-naphthalenemethanol, 1-naphthoic acid, 2-naphthoic acid , 1,4-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and derivatives and metal salts thereof. When these are mixed with the resin-based organic material, they can be mixed as a compound which has been reacted with formaldehyde or hexamine in advance.

  The carbonaceous material is mixed with a conductive carbonaceous material in order to impart conductivity. As the conductive carbonaceous material, one or more types selected from the group consisting of graphite, hard carbon, soft carbon, amorphous carbon and acetylene black can be used. The conductive carbonaceous material can be composed of one or several types. The shape of the conductive carbonaceous material is not particularly limited, such as granular, scaly, or fibrous.

    The active material has a porous structure, the area ratio of pores observed from the cross section of the active material is 2% or more and 16% or less, and the standard deviation of the distance between the centers of gravity of the pores is Is 0.7 or less, which is a value obtained by dividing the distance between the centers of gravity by the average. By having such a porous structure, stress due to expansion and contraction caused by charging and discharging of the silicon phase is reduced as active material particles. When the area ratio of vacancies is lower than 2%, a stress relaxation effect cannot be expected. On the other hand, when the area ratio is higher than 16%, the strength of the particles decreases, and there is a possibility that the electrodes may collapse during charge / discharge cycles. On the other hand, if the degree of dispersion exceeds 0.7, non-uniform stress is likely to be generated in the particles, which may undesirably lead to electrode collapse. The area ratio of pores is preferably 3% or more and 15% or less, and more preferably 4% or more and 10% or less. Further, the degree of dispersion is preferably 0.6 or less, more preferably 0.5 or less.

The area ratio and the degree of dispersion of the pores can be determined by, for example, taking an electron micrograph of a cross section of the negative electrode active material and analyzing the image. Specifically, the pores of these silicon / carbonaceous material composite particles can be evaluated by performing cross sectioning of the test electrode by ion milling and using image analysis software from the electron microscope image. As the image analysis software, “A statue-kun” (registered trademark of Asahi Kasei Engineering Co., Ltd.) manufactured by Asahi Kasei Engineering Co., Ltd. and the like can be mentioned. Regarding the scope of the present invention, five points of 30000-times microscope images were randomly acquired, and each area was analyzed using image analysis software, and the area ratio of holes and the degree of dispersion of holes in an arbitrary visual field region in the microscope images were obtained. (The value obtained by dividing the standard deviation of the distance between the centers of gravity of the holes by the average of the distance between the centers of gravity of the holes) is the average of the obtained values.

  When the active material to be measured is included as the active material of the nonaqueous electrolyte battery, the pretreatment is performed as follows.

  First, the non-aqueous electrolyte battery is discharged to a state close to a state where lithium ions are completely separated from crystals of the positive electrode active material. Next, the nonaqueous electrolyte battery is disassembled in a glove box filled with argon, and an electrode is taken out. The removed electrode is washed with an appropriate solvent and dried under reduced pressure. As the solvent, for example, ethyl methyl carbonate or the like can be used.

  The average diameter of the pores is preferably 200 nm or less. When the average pore diameter exceeds 200 nm, the strength of the particles becomes small, and the same problem as described above occurs. The average pore diameter is preferably from 10 nm to 100 nm. Next, a method for manufacturing the battery active material according to the first embodiment will be described.

  The active material for a battery is prepared by mixing the raw material silicon or silicon-silicon oxide raw material with the organic material consisting of graphite and carbon precursor by mechanical processing in solid phase or liquid phase, stirring, etc., followed by baking. A complex can be formed.

When a silicon-silicon oxide raw material is used, it is preferable to use SiO _X (0.8 ≦ X ≦ 1.5). In particular, it is desirable to use SiO (X） 1) in order to make the quantitative relationship between the silicon phase and the silicon oxide phase a preferable ratio. Further, SiO _X may be pulverized at the time of mixing, but it is preferable to use SiO _X in advance as a fine powder in order to shorten the processing time and to form a silicon oxide phase having a uniform size. Such fine powder can be obtained using a planetary ball mill or the like. In this case, the primary particle size of SiO _X is preferably 50 nm or more and 1000 nm or less on average. More preferably, SiO _X having an average primary particle size of 100 nm or more and less than 500 nm and having a small variation in particle size is preferably used. If the particle size is less than 50 nm, the cohesive force is too strong, and the dispersibility in the active material is deteriorated, which causes a decrease in cycleability. On the other hand, if it exceeds 1000 nm, it is not possible to withstand the stress caused by the volume change during charging and discharging, and the particles are pulverized, whereby the conductive path is cut, and the cycle performance also deteriorates.

Note that SiO _X is separated into two phases, a silicon phase and a silicon oxide phase, by generating silicon crystals by a disproportionation reaction. When X = 1, the reaction is represented by the following formula (1).

2SiO → Si + SiO ₂ (1)
The disproportionation reaction proceeds at a temperature higher than 800 ° C. and separates into a fine silicon phase and a silicon oxide phase. As the reaction temperature increases, the crystal of the silicon phase increases, and the half width of the peak of Si (220) decreases. The firing temperature at which the half value width in the preferred range is obtained is in the range of 850 ° C to 1600 ° C. The firing time is preferably between about 1 hour and 12 hours.

  On the other hand, when silicon is used, the primary particle size is preferably 10 nm or more and 1000 nm or less on average. More preferably, Si having an average primary particle size of 20 nm or more and less than 200 nm and small variations in particle size is preferably used.

  As the conductive carbonaceous material, at least one of a carbon material such as graphite, coke, low-temperature calcined coal, pitch, and CNF and a carbon material precursor can be used. In particular, a material that is melted by heating such as pitch melts during mechanical milling and does not proceed well with compounding. Therefore, a material that does not melt, such as coke and graphite, is preferably used as a mixture.

  Examples of the mechanical compounding process include a turbo mill, a ball mill, a mechanofusion, and a disk mill.

  Although the operating conditions of the mechanical compounding process vary depending on the equipment, it is preferable to perform the mechanical compounding process until the pulverization and compounding sufficiently proceed. However, if the output is excessively increased or the time is excessively increased during the compounding, silicon and carbon react to generate silicon carbide which is inert to the lithium insertion reaction. For this reason, it is necessary to determine appropriate processing conditions under which pulverization / combination sufficiently proceeds and silicon carbide is not generated.

  The mixing and stirring treatment can be performed by, for example, various stirring devices, a ball mill, a bead mill device, and a combination thereof. The compounding of the silicon-based particles with the organic resin and the carbon material, which are precursors of the carbonaceous material, is performed by liquid-phase mixing in a liquid using a dispersion medium. As the dispersion medium, an organic solvent, water, or the like can be used, but it is preferable to use a liquid having good affinity for both the silicon-based particles, the carbon material, and the organic resin. Specific examples include ethanol, acetone, isopropyl alcohol, butanol, methyl ethyl ketone, ethyl acetate, and toluene. The organic resin is preferably soluble in a liquid or a dispersion medium in the mixing step in order to uniformly mix the fine particles with silicon-based particles, and particularly preferably a monomer or oligomer which is liquid and can be easily polymerized. For example, the resin-based organic materials forming the above-mentioned furan resin, xylene resin, ketone resin, amino resin, melamine resin, urea resin, aniline resin, urethane resin, polyimide resin, polyester resin, epoxy resin, phenol resin, etc. No. Further, a naphthalene-based material may be added to these resin-based organic materials. When these are mixed with the resin-based organic material, they can be mixed as a compound which has been reacted with formaldehyde or hexamine in advance.

By subjecting these mixed materials to a baking treatment at a desired temperature through a solidification or hardening step, a SiO _X -carbonaceous material composite or a Si-carbonaceous material complex as a negative electrode active material is formed.

  As a method of forming desired pores in the active material of the present embodiment, a method of adding a low-molecular compound that decomposes and evaporates during firing or a template-like method of dispersing and mixing finally removable nanoparticles is used. It is possible to carry out in various processes such as a method, although it does not matter in particular, but the simplest method is to perform the firing step in a state where a dispersion solvent for uniformly mixing the negative electrode active material precursor composition is left in the system. However, it can be formed. A desired porous structure can be obtained when the residual amount of the solvent is in the range of 0.1% to 5% of the precursor.

  The active material according to the present embodiment is obtained by the manufacturing method as described above.

(2nd Embodiment)
The battery electrode according to the second embodiment includes the battery active material according to the first embodiment. Hereinafter, in the description of the embodiment, the battery electrode will be described as a negative electrode, but the battery electrode of the embodiment can also be used as a positive electrode. Although the electrode is described as being used for a non-aqueous electrolyte secondary battery, the electrode of the embodiment can be used for various batteries.

  FIG. 1 is a conceptual diagram using the battery electrode according to the first embodiment as a negative electrode. As shown in FIG. 1, the negative electrode 100 of the first embodiment includes a current collector 101 and a negative electrode mixture layer 102. The negative electrode mixture layer 102 is a layer of a mixture containing active material particles arranged and formed on the surface of the current collector 101. The negative electrode mixture layer 102 includes a negative electrode active material, a conductive material, and a binder. The binder bonds the negative electrode mixture layer 102 and the current collector.

  The conductive agent has an effect of increasing the conductivity of the negative electrode 100 and is preferably present in the negative electrode mixture layer 102 in a dispersed state. Examples of the conductive agent include acetylene black, carbon black, graphite and the like. As the conductive agent, one having a shape such as a scale, a crushed shape, or a fibrous shape is used. These conductive agents may be used alone or in combination of two or more. In many cases, the conductive agent can also insert and desorb Li, but its charge / discharge capacity is smaller than that of the active material of the present invention. In the present invention, an active material mainly responsible for insertion and desorption of Li is used as a conductive material containing titanium oxide or a titanium composite oxide and silicon oxide particles dispersed in the oxide, and the above-mentioned material is used as a conductive agent.

  The binder fills the gap between the dispersed negative electrode active materials to bind the negative electrode active material and the conductive agent, and also binds the negative electrode active material and the negative electrode current collector 101. Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), polyacrylic acid, polysaccharides such as alginic acid and cellulose and derivatives thereof, ethylene-propylene-diene copolymer (EPDM), Styrene-butadiene rubber (SBR), polyimide, polyamide, polyamide imide, and the like. Among these, a polymer such as polyimide having an imide skeleton is more preferable because it has a high binding force with the negative electrode current collector 101 and can enhance the binding force between the negative electrode active materials. The binder may be used alone or in combination of two or more. When two or more kinds are used in combination, a combination of a binder excellent in binding between the negative electrode active materials and a binder excellent in binding between the negative electrode active material and the negative electrode current collector 101, and a hardness of By employing a combination of a high binder and a binder having excellent flexibility, the life characteristics of the negative electrode 100 can be improved.

  It is desirable that the thickness of the negative electrode mixture layer 102 be in the range of 1.0 μm or more and 150 μm or less. Therefore, when it is carried on both surfaces of the negative electrode current collector 101, the total thickness of the negative electrode mixture layer 102 is in the range of 2.0 μm to 300 μm. The more preferable range of the thickness on one side is 30 μm or more and 100 μm or less. Within this range, large current discharge characteristics and cycle life are significantly improved.

  The compounding ratio of the negative electrode active material, the conductive agent, and the binder in the negative electrode mixture 102 is such that the negative electrode active material particles are 57% by mass to 95% by mass, the conductive agent is 3% by mass to 20% by mass, and the binder is The range of 2% by mass or more and 40% by mass or less is preferable for obtaining good large-current discharge characteristics and cycle life.

  The current collector 101 of the embodiment is a conductive member that binds to the negative electrode mixture layer 102. As the current collector 101, a conductive substrate having a porous structure or a non-porous conductive substrate can be used. These conductive substrates can be formed from, for example, copper, stainless steel, or nickel. The thickness of the current collector is desirably 5 μm or more and 20 μm or less. This is because if the content is within this range, balance between electrode strength and weight reduction can be achieved.

  In the binder of the embodiment, the negative electrode mixture layer 102 and the current collector 101 are joined, but the negative electrode mixture layer 102 and the current collector 101 are joined by an azole compound having an amino group as a substituent. May be.

  Next, a method for manufacturing the negative electrode 100 of the embodiment will be described.

  First, a slurry is prepared by suspending a negative electrode active material, a conductive agent and a binder in a commonly used solvent. The slurry is applied to the current collector 101, dried, and then pressed to form the negative electrode 100. Note that the degree of embedding of the negative electrode active material in the current collector 101 can be adjusted by the pressure of the press. If the pressure of the press is lower than 0.2 kN / cm, the negative electrode active material is hardly embedded in the negative electrode current collector 101, which is not preferable. On the other hand, if the pressing pressure is higher than 10 kN / cm, the negative electrode active material and the current collector 101 may be damaged, such as cracking, which is not preferable. Therefore, the pressing pressure of the negative electrode active material layer 102 after drying the slurry is preferably 0.5 kN / cm or more and 5 kN / cm or less. Here, the pressing pressure is a numerical value when a roller press is used, and is a value obtained by dividing the pressure [kN] measured at the time of pressing by the width [cm] of the negative electrode mixture layer. The width of the negative electrode mixture layer is the length in the direction parallel to the roll axis of the roller press, for example, when the negative electrode mixture layer having a rectangular shape as viewed from above is obliquely passed through the roller press. , A representative length shall be adopted.

  According to the non-aqueous electrolyte battery negative electrode according to the present embodiment, since the non-aqueous electrolyte battery is formed using the non-aqueous electrolyte battery active material according to the first embodiment, the non-aqueous electrolyte battery to which the negative electrode is applied is used. The cycle characteristics are improved while having a high capacity.

(Third embodiment)
A non-aqueous electrolyte battery according to the third embodiment will be described.

  The nonaqueous electrolyte battery according to the third embodiment includes a positive electrode, a negative electrode including the nonaqueous electrolyte battery electrode of the second embodiment, and a nonaqueous electrolyte.

  Hereinafter, the nonaqueous electrolyte secondary battery (nonaqueous electrolyte secondary battery) 200 shown in FIGS. 2 and 3 will be described. FIG. 2 is a conceptual cross-sectional view of the nonaqueous electrolyte battery according to the third embodiment, and FIG.

  The nonaqueous electrolyte battery 200 shown in FIG. 2 includes a flat wound electrode group 201 housed in an exterior material 202. The exterior material 202 may be a laminate film formed in a bag shape or a metal container. In addition, the flat wound electrode group 201 is formed by spirally winding a laminate in which the negative electrode 203, the separator 204, the positive electrode 205, and the separator 204 are sequentially stacked from the outside, that is, from the exterior material 202 side, and press-molded. It is formed by this. The electrode located in the outermost layer is the negative electrode 203, and the negative electrode 203 has a configuration in which the negative electrode mixture layer 203b is formed only on one surface of the negative electrode current collector 203a on the inner side of the battery. The negative electrode 203 other than the outermost layer has a configuration in which a negative electrode mixture layer 203b is formed on both surfaces of a negative electrode current collector 203a. The positive electrode 205 has a configuration in which a positive electrode mixture layer 205b is formed on both surfaces of a positive electrode current collector 205a. Note that, instead of the separator 204, the above-mentioned gelled non-aqueous electrolyte may be used.

  In the wound electrode group 201 shown in FIG. 4, the negative electrode terminal 206 is electrically connected to the negative electrode current collector 203a of the outermost negative electrode 203 near the outer peripheral end. The positive electrode terminal 207 is electrically connected to the positive electrode current collector 205a of the inner positive electrode 205. The negative electrode terminal 206 and the positive electrode terminal 207 extend to the outside of the exterior material 202 or are connected to an extraction electrode provided on the exterior material 202.

  Hereinafter, the negative electrode, the positive electrode, the nonaqueous electrolyte, the separator, the exterior material, the negative electrode terminal, and the positive electrode terminal, which are the components of the nonaqueous electrolyte battery 200, will be described in detail.

(1) Negative electrode As the negative electrode, the negative electrode composed of the battery electrode according to the above-described second embodiment is used.

(2) Positive Electrode The positive electrode includes a positive electrode current collector and a positive electrode mixture layer formed on one or both surfaces of the positive electrode current collector and containing a positive electrode active material, a conductive agent, and a binder. The conductive agent and the binder are optional components.

  The thickness of one side of the positive electrode mixture layer is preferably in the range of 1 μm to 150 μm from the viewpoint of maintaining a large current discharge characteristic and a cycle life of the battery. Preferably, it is 30 μm or more and 120 μm or less. Therefore, when it is carried on both surfaces of the positive electrode current collector, the total thickness of the positive electrode mixture is desirably in the range of 2 μm to 300 μm. A more preferred range on one side is 30 μm to 120 μm. Within this range, large current discharge characteristics and cycle life are improved.

  The positive electrode mixture may include a conductive agent in addition to the positive electrode active material and the binder for bonding the positive electrode active materials to each other.

As the positive electrode active material, various oxides such as manganese dioxide, lithium manganese composite oxide, lithium-containing cobalt oxide (for example, LiCoO ₂ ), and lithium-containing nickel cobalt oxide (for example, LiNi _0.8 Co _0.2 O ₂₎ ) And a lithium manganese composite oxide (eg, LiMn ₂ O ₄ , LiMnO ₂ ) are preferable because a nonaqueous electrolyte secondary battery can obtain a high voltage.

  The conductive agent enhances the current collecting performance of the positive electrode active material and suppresses the contact resistance between the positive electrode active material and the positive electrode current collector. Examples of the conductive agent include acetylene black, carbon black, artificial graphite, natural graphite, carbon fiber, and a conductive polymer. The kind of the conductive agent can be one kind or two or more kinds.

  Specific examples of the binder include, for example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), ethylene-propylene-diene copolymer (EPDM), styrene-butadiene rubber (SBR), and the like. .

  The mixing ratio of the positive electrode active material, the conductive agent and the binder is 80% by mass to 95% by mass of the positive electrode active material, 3% by mass to 20% by mass of the conductive agent, and 2% by mass to 7% by mass of the binder. It is preferable to set it in the range in order to obtain good large-current discharge characteristics and cycle life.

  The positive electrode current collector is a conductive member that binds to the positive electrode mixture layer. As the positive electrode current collector, a conductive substrate having a porous structure or a non-porous conductive substrate can be used. The thickness of the current collector is desirably 5 μm or more and 20 μm or less. This is because in this range, the balance between electrode strength and weight reduction can be achieved.

  Next, a method for manufacturing the positive electrode will be described.

  First, the positive electrode is prepared by, for example, suspending an active material, a conductive agent and a binder in a commonly used solvent to prepare a slurry, applying the slurry to a current collector, drying the slurry, and then pressing the slurry. Is done. The positive electrode 205 may also be manufactured by forming an active material, a conductive agent, and a binder into a pellet to form a positive electrode layer, and forming this on a current collector.

(3) Non-aqueous electrolyte As the non-aqueous electrolyte, a non-aqueous electrolyte, an electrolyte-impregnated polymer electrolyte, a polymer electrolyte, or an inorganic solid electrolyte can be used.

  The non-aqueous electrolyte is a liquid electrolyte prepared by dissolving an electrolyte in a non-aqueous solvent (organic solvent), and is held in a gap in the electrode group.

  As the non-aqueous solvent, a non-aqueous solvent mainly composed of a mixed solvent of propylene carbonate (PC) or ethylene carbonate (EC) and a non-aqueous solvent having a lower viscosity than PC or EC (hereinafter, referred to as a second solvent) is used. Is preferred.

  As the second solvent, for example, chain carbon is preferable. Among them, dimethyl carbonate (DMC), methyl ethyl carbonate (MEC), diethyl carbonate (DEC), ethyl propionate, ethyl propionate, γ-butyrolactone (BL), acetonitrile ( AN), ethyl acetate (EA), toluene, xylene or methyl acetate (MA). These second solvents can be used alone or in the form of a mixture of two or more. In particular, if the number of donors in the second solvent is too large, bonding with Li ions becomes too strong, and the Li ion conductivity is lowered. Therefore, the number of donors is more preferably 16.5 or less.

  The viscosity of the second solvent at 25 ° C. is preferably 2.8 cp or less. The blending amount of ethylene carbonate or propylene carbonate in the mixed solvent of the first solvent and the second solvent is preferably from 1.0% to 80% by volume. A more preferable blending amount of ethylene carbonate or propylene carbonate is 20% or more and 75% or less by volume ratio. If the volume ratio of the second solvent is too small, the viscosity of the non-aqueous electrolyte increases, and the Li ion conductivity decreases. On the other hand, if the volume ratio of the second solvent is too large, the action of PC and EC is hindered and Li The above range is preferable because the ionic conductivity is reduced.

Examples of the electrolyte contained in the nonaqueous electrolyte include lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium borofluoride (LiBF ₄ ), and lithium arsenide hexafluoride (LiAsF ₆ ). And lithium salts (electrolytes) such as lithium trifluoromethasulfonate (LiCF ₃ SO ₃ ) and lithium bistrifluoromethylsulfonylimide [LiN (CF ₃ SO ₂ ) ₂ ]. Among these, LiPF ₆ and LiBF ₄ are preferably used.

  The amount of the electrolyte dissolved in the nonaqueous solvent is desirably 0.5 mol / L or more and 2.0 mol / L or less. If the dissolved amount of the electrolyte is too small, the migration of ions becomes difficult to occur, so that the Li ion conductivity decreases. On the other hand, if the dissolved amount of the electrolyte exceeds 2.0 mol / L, the viscosity of the non-aqueous electrolyte increases, so that Li This is because the ionic conductivity decreases.

(4) Separator The separator is disposed between the positive electrode and the negative electrode.

  A separator can be used when a non-aqueous electrolyte is used or when an electrolyte-impregnated polymer electrolyte is used. As the separator, a porous separator is used. As the material of the separator, for example, a porous film containing polyethylene (PE), polypropylene (PP), cellulose, or poly (vinylidene fluoride) (PVdF), a synthetic resin nonwoven fabric, or the like can be used. Above all, a porous film made of polyethylene, polypropylene, or both is preferable because it can be melted at a certain temperature and cut off the current, so that the safety of the secondary battery can be improved.

  It is preferable that the thickness of the separator be 30 μm or less. If the thickness exceeds 30 μm, the distance between the positive electrode and the negative electrode may increase, and the internal resistance may increase. The lower limit of the thickness is preferably set to 5 μm. If the thickness is less than 5 μm, the strength of the separator may be significantly reduced and an internal short circuit may easily occur. The upper limit of the thickness is more preferably 25 μm, and the lower limit is more preferably 1.0 μm.

  The separator preferably has a heat shrinkage of 20% or less when left at 120 ° C. for one hour. If the heat shrinkage exceeds 20%, the possibility of short-circuiting due to heating increases. More preferably, the heat shrinkage is 15% or less.

  The porosity of the separator is preferably in the range of 30% to 70%. This is due to the following reasons. If the porosity is less than 30%, it may be difficult to obtain high electrolyte retention in the separator 204. On the other hand, if the porosity exceeds 60%, sufficient strength of the separator 204 may not be obtained. A more preferable range of the porosity is 35% or more and 70% or less.

The separator preferably has an air permeability of 500 seconds / 100 cm ³ or less. If the air permeability exceeds 500 seconds / 100 cm ³ , it may be difficult to obtain high lithium ion mobility in the separator. The lower limit of the air permeability is 30 seconds / 100 cm ³ . If the air permeability is less than 30 seconds / 100 cm ³ , sufficient separator strength may not be obtained.

The upper limit of the air permeability is more preferably set to 300 seconds / 100 cm ³ , and the lower limit is more preferably set to 50 seconds / 100 cm ³ . (
(5) Outer material As the outer material in which the positive electrode, the negative electrode, and the nonaqueous electrolyte are accommodated, a metal container or a laminated film outer container is used.

  The metal container is, for example, a metal can made of aluminum, aluminum alloy, or the like, iron, stainless steel, or the like, and has a square or cylindrical shape. The aluminum alloy is preferably an alloy containing elements such as magnesium, zinc, and silicon. When the alloy contains a transition metal such as iron, copper, nickel, or chromium, the amount is preferably 100 ppm by mass or less. Since the strength of the metal container made of an aluminum alloy is dramatically increased as compared with the metal container made of aluminum, the thickness of the metal container can be reduced. As a result, it is possible to realize a nonaqueous electrolyte secondary battery that is thin, lightweight, has high output, and is excellent in heat dissipation.

  Examples of the laminated film include a multilayer film in which an aluminum foil is covered with a resin film. As a resin constituting the resin film, a polymer compound such as polypropylene (PP), polyethylene (PE), nylon, and polyethylene terephthalate (PET) is used. The thickness of the laminate film is preferably 0.5 mm or less, more preferably 0.2 mm or less. The purity of the aluminum foil is preferably 99.5% or more.

  The shape of the exterior material can be selected from flat (thin), square, cylindrical, coin, and button types. Examples of the exterior material include, for example, an exterior material for a small battery mounted on a portable electronic device or the like, an exterior material for a large battery mounted on a two-wheel or four-wheel automobile, etc., according to the battery size.

  As the laminate film, a multilayer film having a metal layer interposed between resin layers is used. The metal layer is preferably an aluminum foil or an aluminum alloy foil for weight reduction. For the resin layer, for example, a polymer material such as polypropylene (PP), polyethylene (PE), nylon, and polyethylene terephthalate (PET) can be used.

  When manufacturing a non-aqueous electrolyte secondary battery including a packaging material made of a laminate film, the wound electrode group to which the negative electrode terminal and the positive electrode terminal are connected is charged into a bag-shaped packaging material having an opening, The liquid non-aqueous electrolyte is injected from the opening of the exterior material, and the wound electrode group and the liquid non-aqueous electrolyte are completely sealed by heat sealing with the opening of the exterior material sandwiching the negative electrode terminal and the positive electrode terminal.

  Further, when manufacturing a non-aqueous electrolyte secondary battery provided with a packaging material made of a metal container, the wound electrode group connected to the negative electrode terminal and the positive electrode terminal is charged into a metal container having an opening, and The non-aqueous electrolyte is injected from the opening of the exterior material, and a lid is attached to the metal container to close the opening.

(6) Negative electrode terminal As the negative electrode terminal, for example, a material having electrical stability and conductivity can be used when the potential with respect to lithium is 1 V or more and 3 V or less. Specifically, aluminum or an aluminum alloy containing elements such as Mg, Ti, Zn, Mn, Fe, Cu, and Si can be used. The negative electrode terminal 206 is preferably made of the same material as the negative electrode current collector 203a in order to reduce the contact resistance with the negative electrode current collector 203a.

(7) Positive electrode terminal As the positive electrode terminal, a material having electrical stability and conductivity can be used when the potential with respect to lithium is in the range of 3 V to 4.25 V. Specifically, aluminum or an aluminum alloy containing elements such as Mg, Ti, Zn, Mn, Fe, Cu, and Si can be used. The positive electrode terminal is preferably made of the same material as the positive electrode current collector in order to reduce the contact resistance with the positive electrode current collector. Further, the nonaqueous electrolyte secondary battery according to this embodiment can further include a lead electrically connected to the electrode group including the positive electrode and the negative electrode. The non-aqueous electrolyte secondary battery according to the embodiment may include, for example, two leads. In that case, one lead is electrically connected to the positive electrode current collection tab, and the other lead is electrically connected to the negative electrode current collection tab.

  Although the material of the lead is not particularly limited, for example, the same material as the positive electrode current collector and the negative electrode current collector is used.

  The nonaqueous electrolyte secondary battery according to the present embodiment may further include a terminal that is electrically connected to the lead and that is drawn out from the exterior material. The nonaqueous electrolyte secondary battery according to the present embodiment may include, for example, two terminals. In that case, one terminal is connected to a lead electrically connected to the positive electrode current collecting tab, and the other terminal is connected to a lead electrically connected to the negative electrode current collecting tab.

  The nonaqueous electrolyte battery according to the third embodiment is not limited to the configuration shown in FIG. 2 and FIG. 3 described above. For example, a configuration in which a stacked electrode group is housed in an exterior material may be used. The stacked electrode group has a structure in which a positive electrode and a negative electrode are alternately stacked with a separator interposed therebetween.

  There are a plurality of positive electrodes, each including a positive electrode current collector and a positive electrode active material-containing layer supported on both surfaces of the positive electrode current collector.

  There are a plurality of negative electrodes, each including a negative electrode current collector and negative electrode active material-containing layers supported on both surfaces of the negative electrode current collector.

  One side of the negative electrode current collector of each negative electrode protrudes from the negative electrode. The protruding negative electrode current collector is electrically connected to a strip-shaped negative electrode terminal. The tip of the strip-shaped negative electrode terminal is drawn out of the exterior material. The positive electrode current collector of the positive electrode has a side located on the side opposite to the protruding side of the negative electrode current collector protruding from the positive electrode. The positive electrode current collector protruding from the positive electrode is electrically connected to a belt-shaped positive electrode terminal. The tip of the strip-shaped positive electrode terminal is located on the opposite side to the negative electrode terminal, and is drawn out from the side of the exterior material.

  The materials, compounding ratios, dimensions, and the like of the members constituting the nonaqueous electrolyte secondary battery using these stacked electrode groups are the same as those of the nonaqueous electrolyte secondary battery 200 described with reference to FIGS. 2 and 3. It has a similar configuration.

  According to the embodiment described above, a nonaqueous electrolyte battery can be provided.

(Fourth embodiment)
Next, a battery pack according to a fourth embodiment will be described.

  The battery pack according to the fourth embodiment has one or more nonaqueous electrolyte secondary batteries (that is, unit cells) according to the third embodiment. When a plurality of cells are included in the battery pack, the cells are electrically connected in series, in parallel, or connected in series and in parallel.

  The battery pack 300 will be specifically described with reference to the conceptual diagram of FIG. 4 and the block diagram of FIG. In the battery pack 300 shown in FIG. 4, the flat nonaqueous electrolyte battery 200 shown in FIG.

  The plurality of unit cells 301 are stacked so that the negative electrode terminal 302 and the positive electrode terminal 303 extending to the outside are aligned in the same direction, and are fastened with an adhesive tape 304 to constitute the assembled battery 305. These cells 301 are electrically connected to each other in series.

  The printed wiring board 306 is arranged to face the side surface of the unit cell 301 from which the negative electrode terminal 302 and the positive electrode terminal 303 extend. As shown in FIG. 5, a thermistor 307, a protection circuit 308, and a terminal 309 for energizing an external device are mounted on the printed wiring board 306. Note that an insulating plate (not shown) is attached to the surface of the protection circuit board 306 facing the assembled battery 305 in order to avoid unnecessary wiring and wiring of the assembled battery 305.

  The positive electrode lead 310 is connected to the positive electrode terminal 303 located at the lowermost layer of the battery pack 305, and the tip is inserted into the positive electrode connector 311 of the printed wiring board 306 and is electrically connected. The negative electrode lead 312 is connected to the negative electrode terminal 302 located on the uppermost layer of the battery pack 305, and the leading end is inserted into the negative electrode connector 313 of the printed wiring board 306 and is electrically connected. These connectors 311 and 313 are connected to the protection circuit 308 through wirings 314 and 315 formed on the printed wiring board 306.

  The thermistor 307 is used to detect the temperature of the cell 305, and the detection signal is transmitted to the protection circuit 308. The protection circuit 308 can cut off the plus side wiring 316a and the minus side wiring 316b between the protection circuit 308 and the terminal 309 for supplying electricity to an external device under predetermined conditions. The predetermined condition is, for example, when the temperature detected by the thermistor 307 becomes equal to or higher than the predetermined temperature. The predetermined condition is when overcharge, overdischarge, overcurrent, or the like of the cell 301 is detected. The detection of the overcharge or the like is performed for each of the single cells 301 or the entire single cell 301. When detecting the individual cells 301, the battery voltage may be detected, or the positive electrode potential or the negative electrode potential may be detected. In the latter case, a lithium electrode used as a reference electrode is inserted into each unit cell 301. In the case of FIGS. 4 and 5, a wiring 317 for voltage detection is connected to each of the cells 301, and a detection signal is transmitted to the protection circuit 308 through these wirings 317.

  A protection sheet 318 made of rubber or resin is disposed on each of three sides of the battery pack 305 except for the side from which the positive electrode terminal 303 and the negative electrode terminal 302 protrude.

  The assembled battery 305 is stored in the storage container 319 together with the protection sheets 318 and the printed wiring board 306. That is, the protective sheets 318 are arranged on both inner surfaces in the long side direction and the inner surface in the short side direction of the storage container 319, and the printed wiring board 306 is arranged on the inner surface on the opposite side in the short side direction. The assembled battery 305 is located in a space surrounded by the protection sheet 318 and the printed wiring board 306. The lid 320 is attached to the upper surface of the storage container 319.

  Note that a heat-shrinkable tape may be used instead of the adhesive tape 304 for fixing the battery pack 305. In this case, the protective sheets are arranged on both side surfaces of the battery pack, and after the heat shrink tape is circulated, the heat shrink tape is heat shrunk to bind the battery pack.

  FIGS. 4 and 5 show a configuration in which the cells 301 are connected in series. However, in order to increase the battery capacity, the cells may be connected in parallel or a combination of series connection and parallel connection may be used. The assembled battery packs can be further connected in series and in parallel.

  According to the present embodiment described above, a battery pack having excellent charge / discharge cycle performance can be provided by including the nonaqueous electrolyte secondary battery having excellent charge / discharge cycle performance in the third embodiment. it can.

  The mode of the battery pack is appropriately changed depending on the use. As a use of the battery pack, a battery pack exhibiting excellent cycle characteristics when a large current is taken out is preferable. Specific examples include a power source for a digital camera, a two- or four-wheeled hybrid electric vehicle, a two- or four-wheeled electric vehicle, and an on-board vehicle such as an assist bicycle. In particular, a battery pack using a nonaqueous electrolyte secondary battery having excellent high-temperature characteristics is suitably used for vehicles.

  The effects will be described below with reference to specific examples.

(Example 1)
Under the following conditions, pulverization, kneading and formation of a composite of SiO, and sintering in Ar gas were performed to obtain a negative electrode active material.

  The pulverization of SiO was performed as follows. The raw material SiO powder was pulverized by a continuous bead mill using beads having a bead diameter of 0.5 μm and ethanol as a dispersion medium for a predetermined time. Further, this SiO powder was pulverized with a planetary ball mill using 0.1 μm balls using ethanol as a dispersion medium, and pulverized to prepare fine SiO powder.

  Subsequently, the silicon monoxide powder and the 3 μm graphite powder obtained by the pulverization treatment were compounded with the carbonaceous material by the following method. 2.8 g of SiO powder, 0.1 g of graphite powder, and 0.01 g of carbon fiber having an average diameter of 180 nm were added to a mixed solution of 3.0 g of resole resin and 5 g of ethanol, and the mixture was kneaded with a kneader to form a slurry. After kneading, ethanol was evaporated at 80 ° C. for 1 hour, and then put into an oven at 150 ° C. and cured for 2 hours to obtain a carbon composite. In addition, when the weight loss was measured by a thermogravimeter at the stage after the evaporation of ethanol, it was 0.9% at 80 ° C.

  Subsequently, the silicon / carbon composite was baked at 1100 ° C. for 3 hours in an Ar gas, cooled to room temperature, pulverized and sieved with a 20 μm diameter sieve to obtain a negative electrode active material under the sieve.

  The obtained negative electrode active material was kneaded with 15% by mass of graphite having an average diameter of 3 μm, 3.5% by mass of SBR resin, and 5% by mass of carboxymethylcellulose using water as a dispersion medium, and was formed on a copper foil having a thickness of 12 μm with a gap of 80 μm. After coating and drying at 100 ° C. for 2 hours, rolling at 2.0 kN, a sample cut into a predetermined size was vacuum-dried at 100 ° C. for 12 hours to form a test electrode, and a charge / discharge test described below was performed. The measurement was performed to evaluate the charge / discharge characteristics and physical properties. Further, as described above, the pores of the silicon / carbonaceous material composite particles were subjected to sectioning of the test electrode by ion milling, and evaluated from the electron microscope image using image analysis software.

(Charge / discharge test)
A battery in which the counter electrode and the reference electrode were made of metal Li and the electrolytic solution was a solution of EC-DEC (volume ratio EC: DEC = 1: 2) of LiPF ₆ (1M) was prepared in an argon atmosphere, and a charge / discharge test was performed. Conditions of the charge and discharge test, between the reference electrode test electrode potential charging at a current density of 1 mA / cm ² to 0.01 V, further subjected to constant-voltage charge of 16 h at 0.01 V, discharge of 1 mA / cm ² The current density was increased to 1.5 V. Further, 50 cycles of charging at a current density of 1 mA / cm ² to a potential difference of 0.01 V between the reference electrode and the test electrode and discharging to 1.5 V at a current density of 1 mA / cm ² were performed 50 times, and 100 cycles with respect to the first cycle were performed. The maintenance rate of the discharge capacity of the eyes was measured.

(Example 2)
3.3 g of silicon fine particles having an average particle size of about 40 nm, 0.1 g of 3 μm graphite powder as a conductive carbonaceous material, and 3.0 g of an organic resin component resole resin are added to 5 g of ethanol, and the mixture is kneaded with a kneader to obtain a mixture. Ethanol was evaporated from the mixed slurry at 80 ° C. for 1 hour, and then put into an oven at 150 ° C. and a curing reaction was performed for 2 hours to obtain a carbon composite. In addition, when the weight loss was measured by a thermogravimeter at the stage after the evaporation of ethanol, it was 1.0% at 80 ° C.

  Subsequently, the silicon / carbon composite was baked at 1100 ° C. for 3 hours in an Ar gas, cooled to room temperature, pulverized and sieved with a 20 μm diameter sieve to obtain a negative electrode active material under the sieve.

  To the obtained negative electrode active material sample, 15% by mass of graphite having an average diameter of 3 μm and 8% by mass of polyimide were kneaded using N-methylpyrrolidone as a dispersion medium, and coated on a 12 μm thick copper foil with a gap of 80 μm. After rolling at 0.0 kN, heat treatment was performed at 250 ° C. for 2 hours in Ar gas, cut into a predetermined size, and then vacuum dried at 100 ° C. for 12 hours to obtain a test electrode. The same evaluation was performed.

(Example 3)
This example is a battery made by the same material and manufacturing method as in Example 1, but the solvent was changed to acetone in the manufacturing process, so that the pore area was 3% and the degree of dispersion was 0.44. A battery similar to that of Example 1 was produced except for the above.

(Example 4)
This example is a battery made by the same material and manufacturing method as in Example 1, but in the manufacturing process, the solvent was changed to butanol, so that the pore area was 15% and the degree of dispersion was 0.57. A battery similar to that of Example 1 was produced except for the above.

(Comparative Example 1)
A mixed slurry having the same composition as in Example 1 was prepared, and ethanol was evaporated at 80 ° C. for 3 hours, and then placed in an oven at 150 ° C. and cured for 2 hours to obtain a carbon composite. In addition, when the weight loss was measured by a thermogravimeter at the stage after the evaporation of ethanol, it was 0.1% or less at 80 ° C.

  Using the obtained silicon / carbon composite as a negative electrode active material precursor, an electrode was prepared and a charge / discharge test was performed in the same manner as in Example 1.

(Comparative Example 2)
A mixed slurry having the same composition as in Example 2 was prepared, ethanol was evaporated at 80 ° C. for 3 hours, and the mixture was placed in an oven at 150 ° C. and cured for 2 hours to obtain a carbon composite. In addition, when the weight loss was measured by a thermogravimeter at the stage after the evaporation of ethanol, it was 0.1% or less at 80 ° C.

  Using the obtained silicon / carbon composite as a negative electrode active material precursor, an electrode was prepared and a charge / discharge test was performed in the same manner as in Example 1.

  The following Examples and Comparative Examples are summarized in Table 1. Further, FIG. 6 shows an active material cross-sectional image obtained by observation with a SEM (Scanning Electron Microscope) of Example 2, and FIG. 7 shows an active material cross-sectional image of Comparative Example 2.

(Comparative Example 3)
This comparative example is a battery produced by the same material and production method as in Comparative Example 1, but by reducing the time of opening the oven at 150 ° C. to 1 hour during the production process, the pore area was reduced by 19%, A battery similar to Comparative Example 1 except that the degree was 0.85.

From the results shown in Table 1, it is understood that the negative electrode of the present invention has good cycle characteristics. That is, as a comparison of FIGS. 6 and 7, in the comparative example in which the active material is dense, the conductive path is interrupted due to a failure such as destruction of the negative electrode active material as the charge / discharge progresses as compared with the example, so that the cycle characteristics deteriorate. did.

Although the embodiments have been described above, the embodiments are not limited to these, and various changes can be made within the scope of the invention described in the claims. Further, the embodiment can be variously modified in the implementation stage without departing from the scope of the invention. Furthermore, various inventions can be formed by appropriately combining a plurality of components disclosed in the above embodiments.

DESCRIPTION OF SYMBOLS 100 ... Negative electrode 101 ... Current collector 102 ... Negative electrode mixture 200 ... Non-aqueous electrolyte secondary battery 201 ... Wound electrode group 202 ... Bag-shaped exterior material 203 ... Negative electrode 203a ... Negative electrode current collector 203b ... Negative electrode active material mixture layer 204 separator 205 positive electrode 205 a positive electrode current collector 205 b positive electrode active material mixture layer 206 negative electrode terminal 207 positive electrode terminal 300 battery pack 301 single cell 302 negative electrode terminal 303 positive electrode terminal 304 adhesive tape 305 Assembled battery 306 ... Printed wiring board 307 ... Thermistor 308 ... Protection circuit 309 ... Electrical terminal 310 ... Pole side lead 311 ... Positive side connector 312 ... Negative side lead 313 ... Negative side connector 314 ... Wiring 315 ... Wiring 316a ... Plus side Wiring 316b ... Minus side wiring 317 ... Wiring 318 ... Protective sheet 319 ... Storage container 320 ... Lid

Claims (8)

An active material comprising a carbonaceous material and a metal or an oxide of the metal, which is Si dispersed in the carbonaceous material, wherein an area ratio of pores observed from a cross section of the active material is 2% or more and 16% or less. And the degree of dispersion, which is a value obtained by dividing the standard deviation of the distance between the centers of gravity of the pores by the average of the distance between the centers of gravity of the pores, is 0.7 or less , and the average pore diameter of the pores is 200 nm or less. Is an active material for batteries. The active material for a battery according to claim 1, wherein the metal is an alloy of Si. The active material for a battery according to claim 1, wherein an average pore diameter of the pores is 10 nm or more and 100 nm or less . 4. The active material for a battery according to claim 1, wherein an area ratio of the pores is 3% or more and 15% or less. 5. An electrode for a battery, comprising an active material mixture layer comprising the active material for a battery according to any one of claims 1 to 4 , a conductive agent, and a binder. A non-aqueous electrolyte battery comprising a positive electrode, a negative electrode using the battery electrode according to claim 5 , and a non-aqueous electrolyte. A battery pack comprising the nonaqueous electrolyte battery according to claim 6 . A vehicle comprising the battery pack according to claim 7.