WO2013164972A1 - Negative electrode active material for lithium secondary batteries and method for producing same - Google Patents

Negative electrode active material for lithium secondary batteries and method for producing same Download PDF

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Publication number
WO2013164972A1
WO2013164972A1 PCT/JP2013/062159 JP2013062159W WO2013164972A1 WO 2013164972 A1 WO2013164972 A1 WO 2013164972A1 JP 2013062159 W JP2013062159 W JP 2013062159W WO 2013164972 A1 WO2013164972 A1 WO 2013164972A1
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Prior art keywords
negative electrode
etching
lithium secondary
active material
electrode active
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PCT/JP2013/062159
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French (fr)
Japanese (ja)
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晃二 久幸
雅司 坂口
忠利 黒住
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昭和電工株式会社
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/02—Making metallic powder or suspensions thereof using physical processes
    • B22F9/04—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling
    • B22F2009/045—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling by other means than ball or jet milling
    • B22F2009/046—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling by other means than ball or jet milling by cutting
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a negative electrode active material for a lithium secondary battery and a method for producing the same, and more specifically, a negative electrode active material for a non-aqueous electrolyte secondary battery capable of reversibly occluding and releasing Li ions in large quantities and the production thereof.
  • the nonaqueous electrolyte secondary battery includes a secondary battery using a nonaqueous electrolyte obtained by dissolving an electrolyte in an organic solvent, and a secondary battery using a nonaqueous electrolyte such as a polymer electrolyte or a gel electrolyte. .
  • Lithium secondary batteries such as lithium ion batteries and lithium polymer batteries have a high energy density and are not only used as main power sources for mobile communication devices and portable electronic devices, but also for large-scale power storage. It is also attracting attention as a power source and an on-vehicle power source.
  • a negative electrode of such a lithium secondary battery conventionally, those formed from various carbon materials such as graphite and carbon having a low crystallinity have been widely used.
  • a negative electrode made of a carbon material has a low usable current density and an insufficient theoretical capacity.
  • graphite which is one of the carbon materials, has a theoretical capacity of only 372 mAh / g, and therefore a higher capacity is desired.
  • a negative electrode active material made of a material other than metal Li which is a substance having a discharge capacity larger than that of a general-purpose carbon material.
  • elements such as Sn, Si and Ag, nitrides, oxides and the like of these can occlude Li ions to form an alloy with Li ions, and the occlusion amount is much larger than various carbon materials. It is known to show a value.
  • a negative electrode active material is an alloy of two or more phases composed of a metal that easily stores and releases Li ions and a metal that does not store and release, and the metal that does not store and release does not store and release Li ions.
  • a negative electrode active material intended to suppress the expansion / contraction of the negative electrode during discharge and the cracking or pulverization of the negative electrode due to expansion / contraction has been proposed.
  • Patent Document 1 discloses a raw material melt consisting of a Li ion storage phase ⁇ and a phase ⁇ made of an intermetallic compound or a solid solution of an element constituting the Li ion storage phase ⁇ and another element and having a selected composition.
  • An anode active material having a structure rapidly quenched and solidified by an atomizing method, a roll quenching method, or the like is described.
  • Patent Document 2 discloses Ag, Al, Au, Ca, Cu, Fe, In, Mg, Pd, Pt, Y Zn, Ti, V, Cr, Mn, Co, Ni, Y, Zr, Nb, Mo, Hf, Ta, W and an A component that is at least one element selected from the group consisting of rare earth elements, and Ga, A negative electrode made of a composite powder formed by mixing a raw material consisting of a B component, which is at least one element selected from the group consisting of Ge, Sb, Si and Sn, and performing mechanical alloying treatment Substances have been described.
  • the object of the present invention is to solve the above-described problems, and to increase the amount of occlusion / release of Li ions, thus increasing the charge / discharge capacity and reducing the capacity decrease due to repeated charge / discharge.
  • An object of the present invention is to provide a negative electrode active material for a lithium secondary battery and a method for producing the same, which can achieve a longer cycle life.
  • the present invention comprises the following aspects in order to achieve the above object.
  • a step of etching an Al-based foil to make an etching foil a step of cutting the etching foil to obtain particles, and a step of further etching the particles obtained by cutting the etching foil
  • Particles obtained by cutting the etching foil are sized to pass through a sieve having a mesh opening of 0.090 mm (based on JIS Z8801-1), and particles obtained by cutting the etching foil
  • each particle after the etching has a size that can pass through a sieve having a mesh size of 0.045 mm (based on JIS Z8801-1).
  • the etching foil is cut to form a powder that is an aggregate of particles, and then the particles constituting the powder are etched,
  • the particles are sized so that they can pass through a sieve having an aperture of 0.1 mm (based on JIS Z8801-1), and the specific surface area of the powder, which is an aggregate of the particles after etching, is 1.0 m 2 /
  • the manufacturing method of the negative electrode active material for lithium secondary batteries characterized by making it g or more.
  • Particles obtained by cutting the etching foil were sized to pass through a sieve having 0.090 mm openings (based on JIS Z8801-1) and obtained by cutting the etching foil.
  • a negative electrode for a lithium secondary battery in which a mixed material containing a negative electrode active material, a conductive additive, and a binder described in any one of 1) to 9) above is attached on a current collector.
  • a lithium secondary battery comprising the negative electrode described in 19) above, a separator, and a positive electrode for a lithium secondary battery.
  • the present invention also includes the following aspects.
  • each particle after the etching has a size capable of passing through a sieve having an aperture of 0.010 mm (based on JIS Z8801-1).
  • each particle after the etching has a size capable of passing through a sieve having a mesh opening of 0.005 mm (based on JIS Z8801-1).
  • the step of etching an Al-based foil to form an etching foil the step of cutting the etching foil to obtain particles, and the etching It consists of powder formed by performing the process of further etching the particles obtained by cutting the foil in this order, and each particle constituting the powder is a sieve having an opening of 0.1 mm (based on JIS Z8801-1) )
  • the specific surface area of the powder, which is an aggregate of etched particles, by the BET method is 1.0 m 2 / g or more, so that it becomes a negative electrode active material for a lithium secondary battery.
  • the specific surface area of the powder becomes sufficiently large.
  • the volume change of the negative electrode active material during charging / discharging is reduced, and the volume change of the negative electrode active material during charging / discharging is increased. Separation of substances from conductive aids and binders can be effectively suppressed, and capacity reduction due to repeated charging and discharging is reduced, and the cycle life of lithium secondary batteries is extended. Will be possible.
  • the reason is estimated as follows. That is, when Li ions are alloyed with Al, a compound containing Li ions is formed on the surface of the particles by reacting preferentially from the surface of the particles, but the specific surface area of the powder by the BET method is 1.
  • the compound containing many Li ions will be formed in the surface of particle
  • the lithium secondary battery including the negative electrode formed from the negative electrode active materials 1) to 9) is more than the lithium secondary battery including the negative electrode formed from the negative electrode active materials made of various carbon materials.
  • a large amount of Li ions can be occluded / released, and the charge / discharge capacity is increased.
  • the volume change at the time of charging / discharging of the lithium secondary battery using the negative electrode formed from the negative electrode active material is further effectively reduced. be able to.
  • the etching foil is cut to form a powder which is an aggregate of particles, and then the particles constituting the powder
  • Each particle is sized so as to be able to pass through a sieve having a mesh size of 0.1 mm (based on JIS Z8801-1), and the ratio of powder as an aggregate of the particles after etching by the BET method. Since only the surface area is 1.0 m 2 / g or more, the negative electrode active material for a lithium secondary battery can be easily produced.
  • the negative electrode active materials 2) to 9) can be easily produced.
  • 1 is a partially cutaway front view showing a lithium secondary battery having a negative electrode formed using a negative electrode active material for a lithium secondary battery according to the present invention.
  • FIG. 1 shows an apparatus for cutting an etching foil to form a powder as an aggregate of particles
  • FIG. 2 shows a lithium secondary battery having a negative electrode formed by using a negative electrode active material for a lithium secondary battery according to the present invention. An example is shown.
  • the negative electrode active material for a lithium secondary battery includes a step of etching an Al-based foil to form an etching foil, a step of cutting the etching foil to obtain particles, and a particle obtained by cutting the etching foil.
  • the specific surface area of the powder, which is an aggregate of etched particles, by the BET method is 1.0 m 2 / g or more.
  • “foil” means that the thickness is 0.006 to 0.2 mm as defined in JIS.
  • “Powder” means an aggregate of particles having a maximum dimension of 1 mm or less, as defined in JIS Z2500.
  • the foil mainly composed of Al is preferably made of Al having a purity of 99% by mass or more, and preferably made of Al having a purity of 99.9% by mass or more. This is for increasing the amount of insertion / extraction of Li ions to / from the negative electrode made of the formed negative electrode active material.
  • the initial charge / discharge capacity of the lithium secondary battery using the negative electrode formed of the negative electrode active material can be increased, and the capacity by repeating charge / discharge can be increased. Reduction can be reduced.
  • the purity of the above-described foil containing Al as a main component represents the balance obtained by subtracting the total amount of Fe, Si, and Cu from 100% by mass, as defined in JIS H4170.
  • the thickness of the foil mainly composed of Al is preferably 0.15 mm or less. If the thickness of the foil exceeds 0.15 mm, cutting becomes difficult and production efficiency may be reduced.
  • An etching foil obtained by etching a foil containing Al as a main component has a porous layer formed on at least one side, but the hole diameter of the etching holes formed in the porous layer of the etching foil is 0.
  • the thickness is preferably 5 to 15 ⁇ m, and more preferably 0.5 to 5 ⁇ m.
  • the term “hole diameter” means an equivalent circle diameter in which the area of the etching hole is represented by the diameter of a circle equal to this area.
  • a plurality of etching holes may be bonded.
  • the area of each bonded etching hole is equivalent to a circle represented by the diameter of a circle equal to this area.
  • the diameter is referred to as the hole diameter.
  • the depth of the etching hole of etching foil is not specifically limited, It is preferable that at least one part etching hole of all the etching holes is a through-hole which penetrated etching foil. Moreover, it is preferable that the sum total of the opening area to the etching foil surface of all the etching holes is 10% or more of the surface area of the etching foil on one side of the etching foil.
  • Etching of a foil containing Al as a main component includes, for example, 2 to 15% by mass of hydrochloric acid and 0.01 to 5% by mass of at least one acid selected from the group consisting of sulfuric acid, oxalic acid and phosphoric acid on both sides of the foil.
  • a first etching treatment step for performing direct current etching in an aqueous solution containing one or more an intermediate treatment step for forming a surface oxide film electrochemically or chemically in an aqueous solution containing NH 4 + or Na + , and sodium chloride , ammonium chloride, Cl of potassium chloride - by a method and a second etching step of at least one neutral salt of the neutral salt performs DC etching in an aqueous solution containing 0.1 to 10% by weight including Done.
  • an appropriate one can be selected from those commercially available as electrode foils for aluminum electrolytic capacitors.
  • an etching foil for an aluminum electrolytic capacitor is formed with an anodized film corresponding to the operating voltage, but the hole diameter is determined so that the hole is not crushed by this anodized film.
  • the etching foil for use does not satisfy the conditions such as the hole diameter of the etching foil and the opening area of the etching hole used to form the negative electrode active materials of the present invention having different purposes.
  • the powder which is an aggregate of particles formed by cutting the etching foil obtained by etching the foil containing Al as a main component, includes particles of various shapes, but the foil is divided. As a result, a new surface is formed and a stretched portion is formed by bending, resulting in an increase in specific surface area.
  • a method of cutting finely with a blade is preferable, and the method of tearing or knocking may cause the opening to the particle surface of the formed powder to be crushed. This is not preferable.
  • a method of finely cutting using a blade there is a method of using an apparatus including a movable blade and a fixed blade, rotating the movable blade at a high speed, and cutting with the fixed blade. In this case, it is possible to adjust the size of the particles by arranging a screen having a large number of sieves below the movable blade and the fixed blade and appropriately adjusting the size of the sieves.
  • FIG. 1 schematically shows a specific example of an apparatus for cutting an etching foil made by etching a foil containing Al as a main component.
  • the housing (21) of the cutting device (20) is provided with a cutting chamber (22) and a powder recovery chamber (23) located below the cutting chamber (22).
  • the housing (21) is provided with a foil inlet (24) facing the cutting chamber (22) and a powder recovery port (25) facing the powder recovery chamber (23).
  • the lids (26) and (27) can be opened and closed freely.
  • a plurality of rotations attached to the rotating body (28) at intervals in the rotating direction of the rotating body (28) and the rotating body (28) A rotary cutting machine (30) having a blade (29) is installed.
  • a plurality of fixed blades (31) are attached to the housing (21) so that the front end portion is desired in the cutting chamber (22). Then, when the rotating body (28) is rotated, the etching foil is cut by the rotating blade (29) and the fixed blade (31).
  • a screen (32) having a plurality of sieves is arranged between the cutting chamber (22) and the powder recovery chamber (23) in the housing (21) of the cutting device (20).
  • the screen (32) preferably has an opening of 0.090 mm.
  • the foil inlet (24) is closed by the lid (26), and the rotating body (28) is rotated.
  • the fixed blade (31) With the fixed blade (31), the etching foil is cut until it becomes a particle having a size passing through the sieve of the screen (32), and the particles passing through the sieve of the screen (32) are put into the powder recovery chamber (23). enter.
  • the lid (27) is opened and the powder is taken out from the powder collection chamber (23). In this way, a powder composed of particles before etching is obtained.
  • the particles obtained by cutting the etching foil preferably have a size that can pass through a sieve (based on JIS Z8801-1) having an opening of 0.090 mm, and are obtained by cutting the etching foil.
  • the specific surface area of the powder, which is an aggregate of particles, by the BET method is preferably 0.5 m 2 / g or more and less than 1.0 m 2 / g.
  • the particles that are formed by cutting the etching foil and before being etched may be formed by cutting the etching foil and pulverizing it by a method in which a compressive stress is applied.
  • Etching of particles obtained by cutting the etching foil may be performed using only alkali, may be performed using only acid, and may be performed using both alkali and acid.
  • the etching method performed using only alkali is, for example, a treatment in a 1N-NaOH aqueous solution at a liquid temperature of 30 ° C. for 1 hour, and the etching method performed using only an acid is, for example, 5N—at a liquid temperature of 60 ° C.
  • This is a method of treating in an aqueous HCl solution for 1 hour.
  • An etching method using both alkali and acid is, for example, a method of treating in a 1N-NaOH aqueous solution at a liquid temperature of 30 ° C.
  • the size of the particles constituting the powder as the negative electrode active material for a lithium secondary battery is limited to a size that can pass through a sieve having a mesh size of 0.1 mm (based on JIS Z8801-1). This is because when it is large, when it is mixed with a conductive additive and a binder in producing the negative electrode, it does not form an appropriate paste, and coating on the current collector becomes difficult.
  • the size of each particle is preferably such that it can pass through a sieve having an aperture of 0.045 mm (based on JIS Z8801-1), and the projected circumference equivalent circle diameter is 0.010 mm or less. More preferably, it is desirable that the projected circumference circle equivalent diameter is 0.005 mm or less.
  • the size of each particle is preferably a size that can pass through a sieve having an opening of 0.045 mm (based on JIS Z8801-1), and a sieve having an opening of 0.010 mm (based on JIS Z8801-1). ) Is more preferable, and it is desirable that the size be able to pass through a sieve having an aperture of 0.005 mm (based on JIS Z8801-1).
  • the specific surface area of the powder used as the negative electrode active material for the lithium secondary battery by the BET method was limited to 0.3 m 2 / g or more because occlusion / release of Li ions to the negative electrode made of the formed negative electrode active material. This is to increase the amount.
  • the specific surface area is preferably 0.5 m 2 / g or more.
  • the specific surface area by the BET method is determined by a known method as follows. That is, the solid substance and the gas present around it attract each other by van der Waals force when rapidly cooled, so measure the amount of adsorbed gas and calculate the surface area of the solid by substituting it into the BET equation. can do.
  • the specific surface area of the powder is determined by the BET method using nitrogen gas as the adsorption gas, helium as the carrier gas, and liquid nitrogen as the coolant.
  • nitrogen gas which is a carrier gas
  • helium which is a carrier gas
  • the nitrogen gas concentration in the mixed gas is 29.8%.
  • Conditions such as the size of the particles constituting the powder serving as the negative electrode active material for a lithium secondary battery and the specific surface area of the powder by the BET method are such that Li ions on the surface of the powder particles formed by cutting the aluminum foil It is determined from the viewpoint of absorbing the occlusion amount, the expansion of the negative electrode during charging of the lithium secondary battery including the negative electrode made of the negative electrode active material, and the contraction of the negative electrode during discharge.
  • the negative electrode active material is used for, for example, a coin-type lithium secondary battery (10) as shown in FIG.
  • the coin-type lithium secondary battery (10) is sandwiched between a negative electrode (12), a positive electrode (13) facing the negative electrode (12), and a negative electrode (12) and a positive electrode (13) in a case (11).
  • the separator (14) and a non-aqueous electrolyte (not shown) are enclosed.
  • the negative electrode (12) is obtained by adhering a mixture (16) containing a negative electrode active material, a conductive additive and a binder on a current collector (15).
  • a current collector for example, a rolled copper foil or a copper foil such as an electrolytic copper foil is used.
  • a conductive auxiliary agent ketjen black or acetylene black is used, but it is not limited to this.
  • the binder polyvinylidene fluoride is used, but is not limited thereto.
  • the positive electrode (13) for example, a material made of LiCoO 2 is used as an active material, and a mixture of the active material, a conductive additive and a binder is attached on a current collector made of aluminum foil.
  • the present invention is not limited to this.
  • the initial charge / discharge capacity of the lithium secondary battery (10) is increased, and the capacity reduction due to repeated charge / discharge is reduced.
  • the negative electrode active material according to the present invention is used in a coin-type lithium secondary battery.
  • the present invention is not limited to this, and known lithium secondary batteries such as a square type, a cylindrical type, and a laminate type are used. Used for secondary batteries.
  • Example A commercially available medium- and high-voltage (170 V or higher) electrolytic capacitor anode was subjected to double-sided etching, and was shredded by a shredder device, and then a sieve having an opening of 0.090 mm (based on JIS Z8801-1)
  • the mixture was pulverized by a pulverizer shown in FIG. 1 having a screen (32) made of a powder to form an aggregate of particles.
  • the particles in the obtained powder have a size that can pass through a sieve having an aperture of 0.090 mm (based on JIS Z8801-1), and the specific surface area of the powder by the BET method is 0.56 m 2 / g. It was.
  • the particles obtained by cutting the etching foil were treated in a 1N-NaOH aqueous solution at a liquid temperature of 30 ° C. for 20 minutes and then treated in a 5N HCl aqueous solution at a liquid temperature of 60 ° C. for 40 minutes.
  • the negative electrode active material was made.
  • the particles in the obtained negative electrode active material have a size that can pass through a sieve having an aperture of 0.045 mm (based on JIS Z8801-1), and the specific surface area of the powder as the negative electrode active material by the BET method is 10. It was 2 m 2 / g.
  • EC ethylene carbonate
  • DMC dimethyl carbonate
  • Comparative Example 1 (volume ratio)) was dissolved in 1 mol / liter LiPF 6 as an electrolyte, and a coin-type model battery (CR2032 type) was produced in a dry box having an atmosphere with a dew point of ⁇ 50 ° C. or lower.
  • Comparative Example A commercially available aluminum foil made of Al having a purity of 99.9% by mass and having a thickness of 0.12 mm was shredded by a shredder apparatus, and then pulverized by a ball mill, and made of a powder that is an aggregate of flat particles.
  • a negative electrode active material was made.
  • the particles in the obtained negative electrode active material have a size that can pass through a sieve having an aperture of 0.050 mm (based on JIS Z8801-1), and the specific surface area of the powder by the BET method is 0.07 m 2 / g. It was.
  • EC ethylene carbonate
  • DMC dimethyl carbonate
  • the model battery was charged at a constant current of 0.2 mA / cm 2 until reaching 1 V, rested for 10 minutes, and then discharged at a constant current of 0.2 mA / cm 2 until it reached 0 V. This was defined as one cycle, and charging / discharging was repeated to examine the discharge capacity.
  • Table 1 shows the number of cycles and the discharge capacity of the model batteries produced in the examples and comparative examples.
  • the model battery produced in the example has a higher initial discharge capacity than the model battery produced in the comparative example, and the discharge capacity after 100 cycles has decreased sufficiently. It can be seen that this value is maintained. Therefore, in the model battery manufactured in the example, the cycle life is extended as compared with the model battery manufactured in the comparative example.
  • the negative electrode active material for a lithium secondary battery according to the present invention is suitably used for a negative electrode of a lithium secondary battery, and it is possible to achieve a long cycle life of the lithium secondary battery.

Abstract

This negative electrode material for lithium secondary batteries is composed of a powder which is formed by sequentially carrying out, in the following order, a step wherein an etched foil is obtained by etching a foil that is mainly composed of Al, a step wherein particles are obtained by cutting the etched foil, and a step wherein the particles obtained by cutting the etched foil are further etched. Each particle constituting the powder has a size that is capable of passing through a 0.1-mm-opening sieve (based on JIS Z8801-1). The powder, which is an assembly of etched particles, has a specific surface area as determined by a BET method of 1.0 m2/g or more. This negative electrode material for lithium secondary batteries enables a lithium secondary battery to have a longer cycle life.

Description

リチウム二次電池用負極活物質およびその製造方法Negative electrode active material for lithium secondary battery and method for producing the same
　この発明はリチウム二次電池用負極活物質およびその製造方法に関し、さらに詳しくは、Ｌｉイオンを多量にかつ可逆的に吸蔵・放出することのできる非水電解質二次電池用負極活物質およびその製造方法に関する。ここで、非水電解質二次電池は、電解質を有機溶媒に溶解した非水電解質を用いた二次電池と、高分子電解質やゲル電解質などの非水電解質を用いた二次電池とを包含する。 The present invention relates to a negative electrode active material for a lithium secondary battery and a method for producing the same, and more specifically, a negative electrode active material for a non-aqueous electrolyte secondary battery capable of reversibly occluding and releasing Li ions in large quantities and the production thereof. Regarding the method. Here, the nonaqueous electrolyte secondary battery includes a secondary battery using a nonaqueous electrolyte obtained by dissolving an electrolyte in an organic solvent, and a secondary battery using a nonaqueous electrolyte such as a polymer electrolyte or a gel electrolyte. .
　リチウムイオン電池、リチウムポリマー電池などのリチウム二次電池は、高いエネルギー密度を有するものであり、移動体通信機器や携帯用電子機器などの主電源として利用されるにとどまらず、大型の電力貯蔵用電源や車載用電源としても注目されている。 Lithium secondary batteries such as lithium ion batteries and lithium polymer batteries have a high energy density and are not only used as main power sources for mobile communication devices and portable electronic devices, but also for large-scale power storage. It is also attracting attention as a power source and an on-vehicle power source.
　このようなリチウム二次電池の負極としては、従来、黒鉛、結晶化度の低い炭素等の各種炭素材料から形成されたものが広く用いられていた。しかしながら、炭素材料からなる負極は、使用可能な電流密度が低く、理論容量も不十分である。たとえば炭素材料のひとつである黒鉛は、理論容量が３７２ｍＡｈ／ｇに過ぎないため、より一層の高容量化が望まれている。 As a negative electrode of such a lithium secondary battery, conventionally, those formed from various carbon materials such as graphite and carbon having a low crystallinity have been widely used. However, a negative electrode made of a carbon material has a low usable current density and an insufficient theoretical capacity. For example, graphite, which is one of the carbon materials, has a theoretical capacity of only 372 mAh / g, and therefore a higher capacity is desired.
　一方、金属Ｌｉから形成された負極をリチウム二次電池に用いた場合には、高い理論容量が得られることが知られているが、充電時に、金属Ｌｉが負極にデンドライト状に析出し、充放電を繰り返すことによって成長を続け、正極側に達して内部短絡が起こるというという大きな欠点がある。その上、析出したデンドライト状金属Ｌｉは、比表面積が大きいために反応活性度が高く、その表面で電子伝導性のない溶媒の分解生成物からなる界面被膜が形成され、これによって電池の内部抵抗が高くなって充放電効率が低下する。このような理由により、金属Ｌｉから形成された負極を用いるリチウム二次電池は信頼性が低く、サイクル寿命が短いという欠点があり、広く実用化される段階には達していない。 On the other hand, when a negative electrode formed from metallic Li is used for a lithium secondary battery, it is known that a high theoretical capacity can be obtained. However, during charging, metallic Li precipitates on the negative electrode in a dendrite-like manner, and is charged. There is a major drawback in that the growth continues by repeating the discharge and reaches the positive electrode side to cause an internal short circuit. In addition, the deposited dendritic metal Li has a high specific activity, and thus has a high reaction activity, and an interfacial film made of a decomposition product of a solvent having no electron conductivity is formed on the surface, thereby forming an internal resistance of the battery. As a result, the charge / discharge efficiency decreases. For these reasons, lithium secondary batteries using a negative electrode formed from metal Li have the disadvantages of low reliability and short cycle life, and have not yet reached the stage of wide practical use.
　このような背景から、汎用の炭素材料よりも放電容量の大きい物質であって、金属Ｌｉ以外の材料からなる負極活物質が望まれている。例えば、Ｓｎ、Ｓｉ、Ａｇなどの元素や、これらの窒化物、酸化物等は、Ｌｉイオンを吸蔵してＬｉイオンと合金を形成することができ、その吸蔵量は各種炭素材料よりはるかに大きい値を示すことが知られている。 From such a background, a negative electrode active material made of a material other than metal Li, which is a substance having a discharge capacity larger than that of a general-purpose carbon material, is desired. For example, elements such as Sn, Si and Ag, nitrides, oxides and the like of these can occlude Li ions to form an alloy with Li ions, and the occlusion amount is much larger than various carbon materials. It is known to show a value.
　しかしながら、Ｓｎ、Ｓｉ、Ａｇなどの元素や、これらの窒化物、酸化物等から形成された負極をリチウム二次電池に用いる場合には、充放電のサイクルを繰り返すうちに、Ｌｉイオンの吸蔵・放出に伴って負極に大きな膨張・収縮が発生し、この膨張・収縮に起因して負極の割れや微粉化が発生する。したがって、Ｓｎ、Ｓｉ、Ａｇなどの元素や、これらの窒化物、酸化物等上記物質から形成された負極を用いるリチウム二次電池はサイクル寿命が低下することになって実用電池として用いることはできない。 However, when a negative electrode formed from an element such as Sn, Si, or Ag, or a nitride or oxide thereof is used for a lithium secondary battery, the Li-ion occlusion / Along with the release, the negative electrode is greatly expanded / contracted, and the negative electrode is cracked or pulverized due to the expansion / contraction. Therefore, a lithium secondary battery using a negative electrode formed from the above-described substances such as Sn, Si, Ag, etc., and their nitrides and oxides cannot be used as a practical battery because its cycle life is reduced. .
　その対策として、Ｌｉイオンを吸蔵・放出しやすい金属と、吸蔵・放出を行なわない金属とからなる２相以上の合金を負極活物質とし、吸蔵・放出を行なわない金属によって、Ｌｉイオンを吸蔵・放出する際の負極の膨張・収縮、および膨張・収縮に起因する負極の割れや微粉化を抑制することを意図した負極活物質が提案されている。 As a countermeasure, a negative electrode active material is an alloy of two or more phases composed of a metal that easily stores and releases Li ions and a metal that does not store and release, and the metal that does not store and release does not store and release Li ions. A negative electrode active material intended to suppress the expansion / contraction of the negative electrode during discharge and the cracking or pulverization of the negative electrode due to expansion / contraction has been proposed.
　たとえば特許文献１には、Ｌｉイオン吸蔵相α 、およびＬｉイオン吸蔵相αを構成する元素と他の元素との金属間化合物または固溶体からなる相βよりなり、かつ組成を選択した原料の溶湯を、アトマイズ法、ロール急冷法等により急冷凝固させた組織を有する負極活物質が記載され、特許文献２には、Ａｇ、Ａｌ、Ａｕ、Ｃａ、Ｃｕ、Ｆｅ、Ｉｎ、Ｍｇ、Ｐｄ、Ｐｔ、Ｙ、Ｚｎ、Ｔｉ、Ｖ、Ｃｒ、Ｍｎ、Ｃｏ、Ｎｉ、Ｙ、Ｚｒ、Ｎｂ、Ｍｏ、Ｈｆ、Ｔａ、Ｗおよび希土類元素からなる群から選ばれた少なくとも一種の元素であるＡ成分、ならびにＧａ、Ｇｅ、Ｓｂ、Ｓｉ及びＳｎからなる群から選ばれた少なくとも一種の元素であるＢ成分からなる原料物質を混合し、メカニカルアロイング処理を行って形成された複合粉末からなる負極活物質が記載されている。 For example, Patent Document 1 discloses a raw material melt consisting of a Li ion storage phase α and a phase β made of an intermetallic compound or a solid solution of an element constituting the Li ion storage phase α and another element and having a selected composition. , An anode active material having a structure rapidly quenched and solidified by an atomizing method, a roll quenching method, or the like is described. Patent Document 2 discloses Ag, Al, Au, Ca, Cu, Fe, In, Mg, Pd, Pt, Y Zn, Ti, V, Cr, Mn, Co, Ni, Y, Zr, Nb, Mo, Hf, Ta, W and an A component that is at least one element selected from the group consisting of rare earth elements, and Ga, A negative electrode made of a composite powder formed by mixing a raw material consisting of a B component, which is at least one element selected from the group consisting of Ge, Sb, Si and Sn, and performing mechanical alloying treatment Substances have been described.
　しかしながら、特許文献１および２記載の負極活物質から形成された負極においては、大きな初期放電容量が得られるものの、充放電を繰り返すうちに生じる負極の膨張・収縮、および膨張・収縮に起因する負極の割れや微粉化を効果的に抑制することはできず、サイクル寿命の長寿命化を達成するには至っていない。 However, in the negative electrode formed from the negative electrode active material described in Patent Documents 1 and 2, a large initial discharge capacity is obtained, but the negative electrode is caused by expansion / contraction of the negative electrode and the expansion / contraction caused by repeated charge / discharge. Cracking and pulverization cannot be effectively suppressed, and the cycle life has not been extended.
特開２００１－２９７７５７号公報JP 2001-297757 A 特開２００５－７８９９９号公報JP 2005-78999 A
　この発明の目的は、上記問題を解決し、Ｌｉイオンを吸蔵・放出する量が多く、したがって充電・放電容量が大きくなるとともに、充電・放電を繰り返すことによる容量低下が少なく、リチウム二次電池のサイクル寿命の長寿命化を達成することができるリチウム二次電池用負極活物質およびその製造方法を提供することにある。 The object of the present invention is to solve the above-described problems, and to increase the amount of occlusion / release of Li ions, thus increasing the charge / discharge capacity and reducing the capacity decrease due to repeated charge / discharge. An object of the present invention is to provide a negative electrode active material for a lithium secondary battery and a method for producing the same, which can achieve a longer cycle life.
　本発明は、上記目的を達成するために以下の態様からなる。 The present invention comprises the following aspects in order to achieve the above object.
　1)Ａｌを主成分とする箔をエッチングしてエッチング箔をつくる工程、当該エッチング箔を切断して粒子を得る工程、およびエッチング箔を切断して得られた粒子をさらにエッチングする工程をこの順序で行うことにより形成された粉末からなり、粉末を構成する各粒子が、目開き０．１ｍｍのふるい（JIS Ｚ８８０１－１に基づく）を通過しうる大きさであり、エッチングされた粒子の集合体である粉末のＢＥＴ法による比表面積が１．０ｍ2／ｇ以上となっているリチウム二次電池用負極活物質。 1) In this order, a step of etching an Al-based foil to make an etching foil, a step of cutting the etching foil to obtain particles, and a step of further etching the particles obtained by cutting the etching foil A particle aggregate formed by performing the above process in which each of the particles constituting the powder can pass through a sieve having a mesh size of 0.1 mm (based on JIS Z8801-1), and is an aggregate of etched particles A negative electrode active material for a lithium secondary battery, wherein the specific surface area of the powder is 1.0 m 2 / g or more by the BET method.
　2)前記エッチング箔を切断して得られた粒子が、目開き０．０９０ｍｍのふるい（JIS Ｚ８８０１－１に基づく）を通過しうる大きさであり、前記エッチング箔を切断して得られた粒子の集合体である粉末のＢＥＴ法による比表面積が０．５ｍ2／ｇ以上でかつ１．０ｍ2／ｇ未満となっている上記1)記載のリチウム二次電池用負極活物質。 2) Particles obtained by cutting the etching foil are sized to pass through a sieve having a mesh opening of 0.090 mm (based on JIS Z8801-1), and particles obtained by cutting the etching foil The negative electrode active material for a lithium secondary battery as described in 1) above, wherein the specific surface area of the powder as an aggregate of BET method is 0.5 m 2 / g or more and less than 1.0 m 2 / g.
　3)前記エッチング後の各粒子が、目開き０．０４５ｍｍのふるい（JIS Ｚ８８０１－１に基づく）を通過しうる大きさである上記1)または2)記載のリチウム二次電池用負極活物質。 3) The negative electrode active material for a lithium secondary battery according to the above 1) or 2), wherein each particle after the etching has a size that can pass through a sieve having a mesh size of 0.045 mm (based on JIS Z8801-1).
　4)前記エッチング後の前記各粒子の投影周長円相当径が、０．０１０ｍｍ以下である上記1)または2)記載のリチウム二次電池用負極活物質。 4) The negative electrode active material for lithium secondary batteries according to 1) or 2) above, wherein the projected circumference equivalent circle diameter of each particle after the etching is 0.010 mm or less.
　5)前記エッチング後の前記各粒子の投影周長円相当径が、０．００５ｍｍ以下である上記1)または2)記載のリチウム二次電池用負極活物質。 5) The negative electrode active material for lithium secondary batteries according to 1) or 2) above, wherein the projected circumference equivalent circle diameter of each particle after the etching is 0.005 mm or less.
　6)前記エッチング後の粒子の集合体である粉末のＢＥＴ法による比表面積が１０．０ｍ2／ｇ以上となっている上記1)～5)のうちのいずれかに記載のリチウム二次電池用負極活物質。 6) The lithium secondary battery according to any one of 1) to 5) above, wherein the powder, which is an aggregate of particles after etching, has a specific surface area of 10.0 m 2 / g or more according to the BET method. Negative electrode active material.
　7)前記Ａｌを主成分とする箔が、純度が９９質量％以上のＡｌからなる上記1)～6)のうちのいずれかに記載のリチウム二次電池用負極活物質。 7) The negative electrode active material for a lithium secondary battery according to any one of 1) to 6), wherein the foil containing Al as a main component is made of Al having a purity of 99% by mass or more.
　8)前記Ａｌを主成分とする箔が、純度が９９．９質量％以上のＡｌからなる上記1)～6)のうちのいずれかに記載のリチウム二次電池用負極活物質。 8) The negative electrode active material for a lithium secondary battery according to any one of 1) to 6) above, wherein the foil containing Al as a main component comprises Al having a purity of 99.9% by mass or more.
　9)前記エッチング前の粒子が、前記エッチング箔を切断するとともに、圧縮応力が加わる方法で粉砕することにより形成されている上記1)～8)のうちのいずれかに記載のリチウム二次電池用負極活物質。 9) The lithium secondary battery according to any one of 1) to 8) above, wherein the particles before etching are formed by cutting the etching foil and pulverizing by a method in which compressive stress is applied. Negative electrode active material.
　10)Ａｌを主成分とする箔をエッチングしてエッチング箔をつくった後、エッチング箔を切断して粒子の集合体である粉末を形成し、ついで粉末を構成する粒子をエッチングすることによって、各粒子を、目開き０．１ｍｍのふるい（JIS Ｚ８８０１－１に基づく）を通過しうる大きさにするとともに、エッチング後の粒子の集合体である粉末のＢＥＴ法による比表面積を１．０ｍ2／ｇ以上にすることを特徴とするリチウム二次電池用負極活物質の製造方法。 10) After etching the foil containing Al as a main component to make an etching foil, the etching foil is cut to form a powder that is an aggregate of particles, and then the particles constituting the powder are etched, The particles are sized so that they can pass through a sieve having an aperture of 0.1 mm (based on JIS Z8801-1), and the specific surface area of the powder, which is an aggregate of the particles after etching, is 1.0 m 2 / The manufacturing method of the negative electrode active material for lithium secondary batteries characterized by making it g or more.
　11)前記エッチング箔を切断して得られた粒子を、目開き０．０９０ｍｍのふるい（JIS Ｚ８８０１－１に基づく）を通過しうる大きさにするとともに、前記エッチング箔を切断して得られた粒子の集合体である粉末のＢＥＴ法による比表面積を０．５ｍ2／ｇ以上でかつ１．０ｍ2／ｇ未満にする上記10)記載のリチウム二次電池用負極活物質。 11) Particles obtained by cutting the etching foil were sized to pass through a sieve having 0.090 mm openings (based on JIS Z8801-1) and obtained by cutting the etching foil. The negative electrode active material for a lithium secondary battery as described in 10) above, wherein the powder, which is an aggregate of particles, has a specific surface area by BET method of 0.5 m 2 / g or more and less than 1.0 m 2 / g.
　12)前記エッチング後の各粒子を、目開き０．０４５ｍｍのふるい（JIS Ｚ８８０１－１に基づく）を通過しうる大きさにする上記10)または11)記載のリチウム二次電池用負極活物質の製造方法。 12) The negative electrode active material for a lithium secondary battery according to 10) or 11) above, wherein each particle after the etching is sized so as to pass through a sieve having a mesh opening of 0.045 mm (based on JIS Z8801-1). Production method.
　13)前記エッチング後の各粒子の投影周長円相当径を０．０１０ｍｍ以下にする上記10)または11)記載のリチウム二次電池用負極活物質の製造方法。 13) The method for producing a negative electrode active material for a lithium secondary battery according to 10) or 11) above, wherein a projected equivalent circle equivalent diameter of each particle after etching is 0.010 mm or less.
　14)前記エッチング後の各粒子の投影周長円相当径を０．００５ｍｍ以下にする上記10)または11)記載のリチウム二次電池用負極活物質の製造方法。 14) The method for producing a negative electrode active material for a lithium secondary battery according to 10) or 11) above, wherein the projected equivalent circular equivalent diameter of each particle after etching is 0.005 mm or less.
　15)前記エッチング後の粒子の集合体である粉末のＢＥＴ法による比表面積を１０．０ｍ2／ｇ以上にする上記10)～14)のうちのいずれかに記載のリチウム二次電池用負極活物質の製造方法。 15) The negative electrode active for lithium secondary batteries according to any one of the above 10) to 14), wherein the powder, which is an aggregate of particles after etching, has a specific surface area by BET method of 10.0 m 2 / g or more. A method for producing a substance.
　16)前記Ａｌを主成分とする箔が、純度が９９質量％以上のＡｌからなる上記10)～15)のうちのいずれかに記載のリチウム二次電池用負極活物質の製造方法。 16) The method for producing a negative electrode active material for a lithium secondary battery according to any one of 10) to 15), wherein the foil containing Al as a main component is made of Al having a purity of 99% by mass or more.
　17)前記Ａｌを主成分とする箔が、純度が９９．９質量％以上のＡｌからなる上記10)～15)のうちのいずれかに記載のリチウム二次電池用負極活物質の製造方法。 17) The method for producing a negative electrode active material for a lithium secondary battery according to any one of 10) to 15), wherein the foil containing Al as a main component is made of Al having a purity of 99.9% by mass or more.
　18)前記エッチング箔を切断するとともに、圧縮応力が加わる方法により粉砕して粒子の集合体である粉末を形成する上記10)～17)のうちのいずれかに記載のリチウム二次電池用負極活物質の製造方法。 18) The negative electrode active for lithium secondary batteries according to any one of 10) to 17) above, wherein the etching foil is cut and pulverized by a method of applying a compressive stress to form a powder that is an aggregate of particles. A method for producing a substance.
　19)集電体上に、上記1)～9)のうちのいずれかに記載された負極活物質、導電助剤および結着剤を含む混合物質が付着されているリチウム二次電池用負極。 19) A negative electrode for a lithium secondary battery in which a mixed material containing a negative electrode active material, a conductive additive, and a binder described in any one of 1) to 9) above is attached on a current collector.
　20)上記19)記載の負極と、セパレータと、リチウム二次電池用正極とを備えているリチウム二次電池。 20) A lithium secondary battery comprising the negative electrode described in 19) above, a separator, and a positive electrode for a lithium secondary battery.
　本発明は、また以下の態様を含む。 The present invention also includes the following aspects.
　a)前記エッチング後の各粒子が、目開き０．０１０ｍｍのふるい（JIS Ｚ８８０１－１に基づく）を通過しうる大きさである上記1)または2)記載のリチウム二次電池用負極活物質。 A) The negative electrode active material for a lithium secondary battery according to the above 1) or 2), wherein each particle after the etching has a size capable of passing through a sieve having an aperture of 0.010 mm (based on JIS Z8801-1).
　b)前記エッチング後の各粒子が、目開き０．００５ｍｍのふるい（JIS Ｚ８８０１－１に基づく）を通過しうる大きさである上記1)または2)記載のリチウム二次電池用負極活物質。 B) The negative electrode active material for a lithium secondary battery according to 1) or 2) above, wherein each particle after the etching has a size capable of passing through a sieve having a mesh opening of 0.005 mm (based on JIS Z8801-1).
　c)前記エッチング後の前記各粒子を、目開き０．０１０ｍｍのふるい（JIS Ｚ８８０１－１に基づく）を通過しうる大きさにする上記10)または11)記載のリチウム二次電池用負極活物質の製造方法。 c) The negative electrode active material for a lithium secondary battery according to 10) or 11) above, wherein each of the particles after the etching is sized so as to pass through a sieve having a mesh size of 0.010 mm (based on JIS Z8801-1). Manufacturing method.
　d)前記エッチング後の前記各粒子を、目開き０．００５ｍｍのふるい（JIS Ｚ８８０１－１に基づく）を通過しうる大きさにする上記10)または11)記載のリチウム二次電池用負極活物質の製造方法。 d) The negative electrode active material for a lithium secondary battery as described in 10) or 11) above, wherein each particle after the etching is sized so as to pass through a sieve having a mesh opening of 0.005 mm (based on JIS Z8801-1). Manufacturing method.
　上記1)～9)のリチウム二次電池用負極活物質によれば、Ａｌを主成分とする箔をエッチングしてエッチング箔をつくる工程、当該エッチング箔を切断して粒子を得る工程、およびエッチング箔を切断して得られた粒子をさらにエッチングする工程をこの順序で行うことにより形成された粉末からなり、粉末を構成する各粒子が、目開き０．１ｍｍのふるい（JIS Ｚ８８０１－１に基づく）を通過しうる大きさであり、エッチングされた粒子の集合体である粉末のＢＥＴ法による比表面積が１．０ｍ2／ｇ以上となっているので、リチウム二次電池用負極活物質となる粉末の比表面積が十分な大きさになる。したがって、充電・放電の際の負極活物質の体積変化が小さくなって、充電・放電の際の負極活物質の体積変化が大きくなることに起因する負極活物質の割れや微粉化、ならびに負極活物質の導電助剤および結着剤からの剥離を効果的に抑制することができるとともに、充電・放電を繰り返すことによる容量低下が少なくなってリチウム二次電池のサイクル寿命の長寿命化を図ることが可能になると考えられる。その理由は、次に述べるとおりであると推定される。すなわち、ＬｉイオンがＡｌと合金化する場合、粒子の表面から優先的に反応して粒子の表面にＬｉイオンを含む化合物が形成されることになるが、粉末のＢＥＴ法による比表面積が１．０ｍ2／ｇ以上となっていれば、粒子の表面において多くのＬｉイオンを含む化合物が形成され、充電時の負極活物質の膨張を抑制することができる。また、放電時にＬｉイオンが負極活物質から出る際の負極活物質の収縮も小さくなる。その結果、充電・放電の際の負極活物質の体積変化が小さくなると推定される。 According to the negative electrode active material for lithium secondary batteries of 1) to 9) above, the step of etching an Al-based foil to form an etching foil, the step of cutting the etching foil to obtain particles, and the etching It consists of powder formed by performing the process of further etching the particles obtained by cutting the foil in this order, and each particle constituting the powder is a sieve having an opening of 0.1 mm (based on JIS Z8801-1) ) And the specific surface area of the powder, which is an aggregate of etched particles, by the BET method is 1.0 m 2 / g or more, so that it becomes a negative electrode active material for a lithium secondary battery. The specific surface area of the powder becomes sufficiently large. Accordingly, the volume change of the negative electrode active material during charging / discharging is reduced, and the volume change of the negative electrode active material during charging / discharging is increased. Separation of substances from conductive aids and binders can be effectively suppressed, and capacity reduction due to repeated charging and discharging is reduced, and the cycle life of lithium secondary batteries is extended. Will be possible. The reason is estimated as follows. That is, when Li ions are alloyed with Al, a compound containing Li ions is formed on the surface of the particles by reacting preferentially from the surface of the particles, but the specific surface area of the powder by the BET method is 1. If it is 0 m < 2 > / g or more, the compound containing many Li ions will be formed in the surface of particle | grains, and it can suppress the expansion | swelling of the negative electrode active material at the time of charge. Further, the shrinkage of the negative electrode active material when Li ions exit from the negative electrode active material during discharge is reduced. As a result, it is estimated that the volume change of the negative electrode active material during charging / discharging is reduced.
　しかも、上記1)～9)の負極活物質から形成された負極を備えたリチウム二次電池においては、各種炭素材料からなる負極活物質から形成された負極を備えたリチウム二次電池に比べて、Ｌｉイオンを多量に吸蔵・放出することが可能になって充電・放電容量が大きくなる。 In addition, the lithium secondary battery including the negative electrode formed from the negative electrode active materials 1) to 9) is more than the lithium secondary battery including the negative electrode formed from the negative electrode active materials made of various carbon materials. In addition, a large amount of Li ions can be occluded / released, and the charge / discharge capacity is increased.
　上記2)～9)のリチウム二次電池用負極活物質によれば、当該負極活物質から形成された負極を用いたリチウム二次電池の充電・放電時の体積変化を一層効果的に小さくすることができる。 According to the negative electrode active material for lithium secondary batteries of the above 2) to 9), the volume change at the time of charging / discharging of the lithium secondary battery using the negative electrode formed from the negative electrode active material is further effectively reduced. be able to.
　上記10)の方法によれば、Ａｌを主成分とする箔をエッチングしてエッチング箔をつくった後、エッチング箔を切断して粒子の集合体である粉末を形成し、ついで粉末を構成する粒子をエッチングすることによって、各粒子を、目開き０．１ｍｍのふるい（JIS Ｚ８８０１－１に基づく）を通過しうる大きさにするとともに、エッチング後の粒子の集合体である粉末のＢＥＴ法による比表面積を１．０ｍ2／ｇ以上にするだけであるので、リチウム二次電池用負極活物質を容易に製造することができる。 According to the method of 10) above, after etching a foil containing Al as a main component to form an etching foil, the etching foil is cut to form a powder which is an aggregate of particles, and then the particles constituting the powder Each particle is sized so as to be able to pass through a sieve having a mesh size of 0.1 mm (based on JIS Z8801-1), and the ratio of powder as an aggregate of the particles after etching by the BET method. Since only the surface area is 1.0 m 2 / g or more, the negative electrode active material for a lithium secondary battery can be easily produced.
　上記11)～18)の方法によれば、上記2)～9)の負極活物質を容易に製造することができる。 According to the methods 11) to 18), the negative electrode active materials 2) to 9) can be easily produced.
　上記19)の負極および上記20)のリチウム二次電池によれば、上記1)～9)の負極活物質で述べたような顕著な効果を奏する。 According to the negative electrode of the above 19) and the lithium secondary battery of the above 20), there are remarkable effects as described in the negative electrode active materials of the above 1) to 9).
Ａｌを主成分とする箔をエッチングしてつくったエッチング箔を切断して粒子の集合体である粉末を形成する装置を示す概略垂直断面図である。It is a schematic vertical sectional view showing an apparatus for forming a powder as an aggregate of particles by cutting an etching foil made by etching a foil containing Al as a main component. この発明によるリチウム二次電池用負極活物質を用いて形成された負極を有するリチウム二次電池を示す一部切り欠き正面図である。1 is a partially cutaway front view showing a lithium secondary battery having a negative electrode formed using a negative electrode active material for a lithium secondary battery according to the present invention.
(10)：リチウム二次電池
(12)：負極
(13)：正極
(14)：セパレータ (10): Lithium secondary battery
(12): Negative electrode
(13): Positive electrode
(14): Separator
　以下、この発明の実施形態を、図面を参照して説明する。 Hereinafter, embodiments of the present invention will be described with reference to the drawings.
　図１はエッチング箔を切断して粒子の集合体である粉末を形成する装置を示し、図２はこの発明によるリチウム二次電池用負極活物質を用いて形成された負極を有するリチウム二次電池の一例を示す。 FIG. 1 shows an apparatus for cutting an etching foil to form a powder as an aggregate of particles, and FIG. 2 shows a lithium secondary battery having a negative electrode formed by using a negative electrode active material for a lithium secondary battery according to the present invention. An example is shown.
　リチウム二次電池用負極活物質は、Ａｌを主成分とする箔をエッチングしてエッチング箔をつくる工程、当該エッチング箔を切断して粒子を得る工程、およびエッチング箔を切断して得られた粒子をさらにエッチングする工程をこの順序で行うことにより形成された粉末からなり、粉末を構成する各粒子が、目開き０．１ｍｍのふるい（JIS Ｚ８８０１－１に基づく）を通過しうる大きさであり、エッチングされた粒子の集合体である粉末のＢＥＴ法による比表面積が１．０ｍ2／ｇ以上となっているものである。 The negative electrode active material for a lithium secondary battery includes a step of etching an Al-based foil to form an etching foil, a step of cutting the etching foil to obtain particles, and a particle obtained by cutting the etching foil. Is a size that allows each particle constituting the powder to pass through a sieve having a mesh size of 0.1 mm (based on JIS Z8801-1). The specific surface area of the powder, which is an aggregate of etched particles, by the BET method is 1.0 m 2 / g or more.
　ここで、「箔」とは、ＪＩＳで規定されているように、厚さが０．００６～０．２ｍｍのものを意味するものとする。また、「粉末」とは、JIS Ｚ２５００で規定されているように、最大寸法１ｍｍ以下の粒子の集合体を意味するものとする。 Here, “foil” means that the thickness is 0.006 to 0.2 mm as defined in JIS. “Powder” means an aggregate of particles having a maximum dimension of 1 mm or less, as defined in JIS Z2500.
　Ａｌを主成分とする箔としては、純度が９９質量％以上のＡｌからなることが好ましく、純度が９９．９質量％以上のＡｌからなることが望ましい。これは、形成された負極活物質からなる負極へのＬｉイオンの吸蔵・放出量を多くするためである。特に、純度９９．９質量％以上のＡｌからなる場合、負極活物質で形成された負極を用いたリチウム二次電池の初期充放電容量を大きくすることができるとともに、充放電を繰り返すことによる容量低下を少なくすることができる。なお、上述したＡｌを主成分とする箔の純度は、JIS Ｈ４１７０に規定されているように、１００質量％からＦｅ、ＳｉおよびＣｕの合計量を減じた残部を表すものである。 The foil mainly composed of Al is preferably made of Al having a purity of 99% by mass or more, and preferably made of Al having a purity of 99.9% by mass or more. This is for increasing the amount of insertion / extraction of Li ions to / from the negative electrode made of the formed negative electrode active material. In particular, when composed of Al having a purity of 99.9% by mass or more, the initial charge / discharge capacity of the lithium secondary battery using the negative electrode formed of the negative electrode active material can be increased, and the capacity by repeating charge / discharge can be increased. Reduction can be reduced. Note that the purity of the above-described foil containing Al as a main component represents the balance obtained by subtracting the total amount of Fe, Si, and Cu from 100% by mass, as defined in JIS H4170.
　また、前記Ａｌを主成分とする箔の厚さは０．１５ｍｍ以下であることが好ましい。箔の厚さが０．１５ｍｍを超えると、切断が困難になり、生産効率が低下するおそれがある。 The thickness of the foil mainly composed of Al is preferably 0.15 mm or less. If the thickness of the foil exceeds 0.15 mm, cutting becomes difficult and production efficiency may be reduced.
　Ａｌを主成分とする箔をエッチングして得られたエッチング箔は、すくなくとも片面に多孔質層が形成されることになるが、エッチング箔の多孔質層に形成されているエッチング孔の孔径は０．５～１５μｍであることが好ましく、０．５～５μｍであることが望ましい。ここで、エッチング箔表面へのエッチング孔の開口は円形でないことが多いので、「孔径」という語は、エッチング孔の面積を、この面積と等しい円の直径で表した円相当径を意味するものとする。また、エッチング箔の多孔質層においては、複数のエッチング孔が結合している場合もあるが、この場合は、結合した各エッチング孔の面積を、この面積と等しい円の直径で表した円相当径を孔径というものとする。また、エッチング箔のエッチング孔の深さは、特に限定されるものではなく、すべてのエッチング孔のうちの少なくとも一部のエッチング孔はエッチング箔を貫通した貫通孔であることが好ましい。また、エッチング箔の片面において、すべてのエッチング孔のエッチング箔表面への開口面積の合計が、エッチング箔の片面の表面積の１０％以上であることが好ましい。 An etching foil obtained by etching a foil containing Al as a main component has a porous layer formed on at least one side, but the hole diameter of the etching holes formed in the porous layer of the etching foil is 0. The thickness is preferably 5 to 15 μm, and more preferably 0.5 to 5 μm. Here, since the opening of the etching hole on the surface of the etching foil is often not circular, the term “hole diameter” means an equivalent circle diameter in which the area of the etching hole is represented by the diameter of a circle equal to this area. And In the porous layer of the etching foil, a plurality of etching holes may be bonded. In this case, the area of each bonded etching hole is equivalent to a circle represented by the diameter of a circle equal to this area. The diameter is referred to as the hole diameter. Moreover, the depth of the etching hole of etching foil is not specifically limited, It is preferable that at least one part etching hole of all the etching holes is a through-hole which penetrated etching foil. Moreover, it is preferable that the sum total of the opening area to the etching foil surface of all the etching holes is 10% or more of the surface area of the etching foil on one side of the etching foil.
　Ａｌを主成分とする箔のエッチングは、たとえば箔の両面に、塩酸２～１５質量％と、硫酸、蓚酸およびリン酸からなる群のうちの少なくとも１種の酸を０．０１～５質量％含む水溶液中で直流エッチングを行う第１エッチング処理工程と、ＮＨ4 +またはＮａ+を含む水溶液中で表面酸化皮膜を電気化学的または化学的に形成する１回以上の中間処理工程と、塩化ナトリウム、塩化アンモニウム、塩化カリウム等のＣｌ-を含む中性塩のうち少なくとも１種の中性塩を０．１～１０質量％含む水溶液中で直流エッチングを行う第２エッチング処理工程とを含む方法によって行われる。 Etching of a foil containing Al as a main component includes, for example, 2 to 15% by mass of hydrochloric acid and 0.01 to 5% by mass of at least one acid selected from the group consisting of sulfuric acid, oxalic acid and phosphoric acid on both sides of the foil. A first etching treatment step for performing direct current etching in an aqueous solution containing one or more, an intermediate treatment step for forming a surface oxide film electrochemically or chemically in an aqueous solution containing NH 4 + or Na + , and sodium chloride , ammonium chloride, Cl of potassium chloride - by a method and a second etching step of at least one neutral salt of the neutral salt performs DC etching in an aqueous solution containing 0.1 to 10% by weight including Done.
　Ａｌを主成分とする箔をエッチングしてつくられたエッチング箔としては、たとえばアルミニウム電解コンデンサ用電極箔として市販されているもののうちから、適当なものを選んで用いることができる。すなわち、アルミニウム電解コンデンサ用のエッチング箔には、使用電圧に応じた陽極酸化皮膜が形成されるが、この陽極酸化皮膜によって孔が潰れないように孔径が定められているので、すべてのアルミニウム電解コンデンサ用エッチング箔が、使用目的が異なっている本発明の負極活物質を形成するのに用いられるエッチング箔の孔の孔径や、エッチング孔の開口面積などの条件を満たしているわけではない。しかしながら、アルミニウム電解コンデンサ用のエッチング箔の中には、本発明の負極活物質である粉末を形成するのに用いられるエッチング箔と同様の条件、すなわち厚み、エッチング孔の孔径、すべてのエッチング孔のエッチング箔表面への開口面積の合計のエッチング箔の表面積に対する比率を有するものが存在する。 As an etching foil made by etching a foil containing Al as a main component, an appropriate one can be selected from those commercially available as electrode foils for aluminum electrolytic capacitors. In other words, an etching foil for an aluminum electrolytic capacitor is formed with an anodized film corresponding to the operating voltage, but the hole diameter is determined so that the hole is not crushed by this anodized film. The etching foil for use does not satisfy the conditions such as the hole diameter of the etching foil and the opening area of the etching hole used to form the negative electrode active materials of the present invention having different purposes. However, in the etching foil for aluminum electrolytic capacitors, the same conditions as the etching foil used for forming the powder which is the negative electrode active material of the present invention, that is, the thickness, the hole diameter of the etching hole, all the etching holes Some have a ratio of the total area of the openings to the etching foil surface to the surface area of the etching foil.
　前記Ａｌを主成分とする箔をエッチングして得られたエッチング箔を切断することにより形成された粒子の集合体である粉末には、様々な形状の粒子が含まれるが、箔が分断されることによって新生面が生じるとともに屈曲による延伸部分が生じ、その結果比表面積が増大すると考えられる。 The powder, which is an aggregate of particles formed by cutting the etching foil obtained by etching the foil containing Al as a main component, includes particles of various shapes, but the foil is divided. As a result, a new surface is formed and a stretched portion is formed by bending, resulting in an increase in specific surface area.
　前記エッチング箔を切断して粉末にする切断方法としては、刃を使って細かく切断する方法が好ましく、引きちぎったり、たたきつけたりする方法は、形成された粉末の粒子表面への開口が潰れる可能性があるので好ましくない。刃を使って細かく切断する方法としては、可動刃と固定刃とを備えた装置を使用し、可動刃を高速回転させて固定刃とともに切断する方法がある。この場合、可動刃および固定刃の下方に多数のふるい目を有するスクリーンを配置し、ふるい目の大きさを適切に調節することにより粒子の大きさを調整することができる。 As the cutting method of cutting the etching foil into powder, a method of cutting finely with a blade is preferable, and the method of tearing or knocking may cause the opening to the particle surface of the formed powder to be crushed. This is not preferable. As a method of finely cutting using a blade, there is a method of using an apparatus including a movable blade and a fixed blade, rotating the movable blade at a high speed, and cutting with the fixed blade. In this case, it is possible to adjust the size of the particles by arranging a screen having a large number of sieves below the movable blade and the fixed blade and appropriately adjusting the size of the sieves.
　図１は、Ａｌを主成分とする箔をエッチングしてつくったエッチング箔を切断する装置の一具体例を概略的に示す。 FIG. 1 schematically shows a specific example of an apparatus for cutting an etching foil made by etching a foil containing Al as a main component.
　切断装置(20)のハウジング(21)には、切断室(22)と、切断室(22)の下方に位置する粉末回収室(23)とが設けられている。ハウジング(21)には、切断室(22)内に臨む箔投入口(24)と、粉末回収室(23)に臨む粉末回収口(25)とが設けられており、それぞれハウジング(21)に着脱自在に取り付けられた蓋(26)(27)により開閉自在となっている。 The housing (21) of the cutting device (20) is provided with a cutting chamber (22) and a powder recovery chamber (23) located below the cutting chamber (22). The housing (21) is provided with a foil inlet (24) facing the cutting chamber (22) and a powder recovery port (25) facing the powder recovery chamber (23). The lids (26) and (27) can be opened and closed freely.
　切断装置(20)のハウジング(21)の切断室(22)内に、回転体(28)および回転体(28)の回転方向に間隔をおいて回転体(28)に取り付けられた複数の回転刃(29)を有する回転切断機(30)が設置されている。また、ハウジング(21)には、先端部が切断室(22)内に望むように、複数の固定刃(31)が取り付けられている。そして、回転体(28)が回転させられることによって、回転刃(29)と固定刃(31)とによりエッチング箔が切断される。 In the cutting chamber (22) of the housing (21) of the cutting device (20), a plurality of rotations attached to the rotating body (28) at intervals in the rotating direction of the rotating body (28) and the rotating body (28) A rotary cutting machine (30) having a blade (29) is installed. In addition, a plurality of fixed blades (31) are attached to the housing (21) so that the front end portion is desired in the cutting chamber (22). Then, when the rotating body (28) is rotated, the etching foil is cut by the rotating blade (29) and the fixed blade (31).
　切断装置(20)のハウジング(21)内における切断室(22)と粉末回収室(23)との間には複数のふるい目を有するスクリーン(32)が配置されている。スクリーン(32)は、目開き０．０９０ｍｍからなることが好ましい。 A screen (32) having a plurality of sieves is arranged between the cutting chamber (22) and the powder recovery chamber (23) in the housing (21) of the cutting device (20). The screen (32) preferably has an opening of 0.090 mm.
　このような切断装置において、エッチング箔を箔投入口(24)から投入した後に箔投入口(24)を蓋(26)により塞いで回転体(28)を回転させると、回転刃(29)と固定刃(31)とによって、エッチング箔がスクリーン(32)のふるい目を通る大きさの粒子になるまで切断され、スクリーン(32)のふるい目を通過した粒子が粉末回収室(23)内に入る。その後、蓋(27)を開けて粉末回収室(23)内から粉末を取り出す。こうして、エッチングを施す前の粒子からなる粉末が得られる。 In such a cutting apparatus, after the etching foil is introduced from the foil inlet (24), the foil inlet (24) is closed by the lid (26), and the rotating body (28) is rotated. With the fixed blade (31), the etching foil is cut until it becomes a particle having a size passing through the sieve of the screen (32), and the particles passing through the sieve of the screen (32) are put into the powder recovery chamber (23). enter. Thereafter, the lid (27) is opened and the powder is taken out from the powder collection chamber (23). In this way, a powder composed of particles before etching is obtained.
　前記エッチング箔を切断して得られた粒子は、目開き０．０９０ｍｍのふるい（JIS Ｚ８８０１－１に基づく）を通過しうる大きさであることが好ましく、前記エッチング箔を切断して得られた粒子の集合体である粉末のＢＥＴ法による比表面積は０．５ｍ2／ｇ以上でかつ１．０ｍ2／ｇ未満となっていることが好ましい。 The particles obtained by cutting the etching foil preferably have a size that can pass through a sieve (based on JIS Z8801-1) having an opening of 0.090 mm, and are obtained by cutting the etching foil. The specific surface area of the powder, which is an aggregate of particles, by the BET method is preferably 0.5 m 2 / g or more and less than 1.0 m 2 / g.
　前記エッチング箔を切断することにより形成され、かつエッチングされる前の前記粒子は、前記エッチング箔を切断するとともに、圧縮応力が加わる方法で粉砕することにより形成されていてもよい。 The particles that are formed by cutting the etching foil and before being etched may be formed by cutting the etching foil and pulverizing it by a method in which a compressive stress is applied.
　前記エッチング箔を切断することにより得られた粒子のエッチングは、アルカリのみを用いて行われる場合と、酸のみを用いて行われる場合と、アルカリおよび酸の両者を用いて行われる場合とがある。アルカリのみを用いて行われるエッチング法は、たとえば液温３０℃の１Ｎ－ＮａＯＨ水溶液中において１時間処理する方法であり、酸のみを用いて行われるエッチング法は、たとえば液温６０℃の５Ｎ－ＨＣｌ水溶液中において１時間処理する方法である。また、アルカリおよび酸の両者を用いて行われるエッチング法は、たとえば液温３０℃の１Ｎ－ＮａＯＨ水溶液中において２０分間処理した後に、液温６０℃の５Ｎ－ＨＣｌ水溶液中において４０分間処理する方法である。前記エッチング箔を切断することにより得られた粒子にエッチングを施すと、粒子の大きさは小さくなり、粒子の集合体である粉末のＢＥＴ法による比表面積は大きくなる。 Etching of particles obtained by cutting the etching foil may be performed using only alkali, may be performed using only acid, and may be performed using both alkali and acid. . The etching method performed using only alkali is, for example, a treatment in a 1N-NaOH aqueous solution at a liquid temperature of 30 ° C. for 1 hour, and the etching method performed using only an acid is, for example, 5N—at a liquid temperature of 60 ° C. This is a method of treating in an aqueous HCl solution for 1 hour. An etching method using both alkali and acid is, for example, a method of treating in a 1N-NaOH aqueous solution at a liquid temperature of 30 ° C. for 20 minutes and then treating in a 5N-HCl aqueous solution at a liquid temperature of 60 ° C. for 40 minutes. It is. When the particles obtained by cutting the etching foil are etched, the size of the particles decreases, and the specific surface area of the powder, which is an aggregate of particles, by the BET method increases.
　リチウム二次電池用負極活物質となる粉末を構成する粒子の大きさを、目開き０．１ｍｍのふるい（JIS Ｚ８８０１－１に基づく）を通過しうる大きさに限定したのは、これよりも大きくなると、負極をつくるにあたって導電助剤および結着剤と混合した際に、適度なペースト状にならず、集電体上へのコーティングが困難になるからである。各粒子の大きさは、目開き０．０４５ｍｍのふるい（JIS Ｚ８８０１－１に基づく）を通過しうる大きさであることが好ましく、投影周長円相当径が、０．０１０ｍｍ以下であることがより好ましく、投影周長円相当径が、０．００５ｍｍ以下であることが望ましい。また、各粒子の大きさは、目開き０．０４５ｍｍのふるい（JIS Ｚ８８０１－１に基づく）を通過しうる大きさであることが好ましく、目開き０．０１０ｍｍのふるい（JIS Ｚ８８０１－１に基づく）を通過しうる大きさであることがより好ましく、目開き０．００５ｍｍのふるい（JIS Ｚ８８０１－１に基づく）を通過しうる大きさであることが望ましい。 The size of the particles constituting the powder as the negative electrode active material for a lithium secondary battery is limited to a size that can pass through a sieve having a mesh size of 0.1 mm (based on JIS Z8801-1). This is because when it is large, when it is mixed with a conductive additive and a binder in producing the negative electrode, it does not form an appropriate paste, and coating on the current collector becomes difficult. The size of each particle is preferably such that it can pass through a sieve having an aperture of 0.045 mm (based on JIS Z8801-1), and the projected circumference equivalent circle diameter is 0.010 mm or less. More preferably, it is desirable that the projected circumference circle equivalent diameter is 0.005 mm or less. Further, the size of each particle is preferably a size that can pass through a sieve having an opening of 0.045 mm (based on JIS Z8801-1), and a sieve having an opening of 0.010 mm (based on JIS Z8801-1). ) Is more preferable, and it is desirable that the size be able to pass through a sieve having an aperture of 0.005 mm (based on JIS Z8801-1).
　さらに、リチウム二次電池用負極活物質となる粉末のＢＥＴ法による比表面積を０．３ｍ2／ｇ以上に限定したのは、形成された負極活物質からなる負極へのＬｉイオンの吸蔵・放出量を多くするためである。当該比表面積は０．５ｍ2／ｇ以上であることが好ましい。 Furthermore, the specific surface area of the powder used as the negative electrode active material for the lithium secondary battery by the BET method was limited to 0.3 m 2 / g or more because occlusion / release of Li ions to the negative electrode made of the formed negative electrode active material. This is to increase the amount. The specific surface area is preferably 0.5 m 2 / g or more.
　ここで、ＢＥＴ法による比表面積は、公知の方法で次のようにして求められる。すなわち、固体物質およびその周囲に存在するガスは、急速に冷却されるとファンデルワールス力によって互いに引き付け合うので、吸着したガスの量を測定し、ＢＥＴ式に代入する事によって固体の表面積を計算することができる。上記においては、粉末の比表面積は、吸着ガスとして窒素ガス、キャリアガスとしてヘリウム、冷却剤として液体窒素を使用してＢＥＴ法により求められたものである。なお、キャリアガスであるヘリウムは希釈気体であり、窒素ガスと混合された混合気体として用いられる。当該混合気体における窒素ガス濃度は、ここでは２９．８％である。 Here, the specific surface area by the BET method is determined by a known method as follows. That is, the solid substance and the gas present around it attract each other by van der Waals force when rapidly cooled, so measure the amount of adsorbed gas and calculate the surface area of the solid by substituting it into the BET equation. can do. In the above, the specific surface area of the powder is determined by the BET method using nitrogen gas as the adsorption gas, helium as the carrier gas, and liquid nitrogen as the coolant. Note that helium, which is a carrier gas, is a diluted gas and is used as a mixed gas mixed with nitrogen gas. Here, the nitrogen gas concentration in the mixed gas is 29.8%.
　リチウム二次電池用負極活物質となる粉末を構成する粒子の大きさや、粉末のＢＥＴ法による比表面積などの条件は、アルミニウム箔を切断して形成された粉末の粒子の表面へのＬｉイオンの吸蔵量や、当該負極活物質からなる負極を備えたリチウム二次電池の充電時の負極の膨張や、放電時の負極の収縮を吸収するという観点から定められたものである。 Conditions such as the size of the particles constituting the powder serving as the negative electrode active material for a lithium secondary battery and the specific surface area of the powder by the BET method are such that Li ions on the surface of the powder particles formed by cutting the aluminum foil It is determined from the viewpoint of absorbing the occlusion amount, the expansion of the negative electrode during charging of the lithium secondary battery including the negative electrode made of the negative electrode active material, and the contraction of the negative electrode during discharge.
　負極活物質は、図２に示すように、たとえばコイン型のリチウム二次電池(10)に用いられる。コイン型のリチウム二次電池(10)は、ケース(11)内に、負極(12)、負極(12)と対向した正極(13)、負極(12)と正極(13)との間に挟まれたセパレータ(14)、および非水電解質（図示略）が封入されたものである。 The negative electrode active material is used for, for example, a coin-type lithium secondary battery (10) as shown in FIG. The coin-type lithium secondary battery (10) is sandwiched between a negative electrode (12), a positive electrode (13) facing the negative electrode (12), and a negative electrode (12) and a positive electrode (13) in a case (11). The separator (14) and a non-aqueous electrolyte (not shown) are enclosed.
　負極(12)は、集電体(15)上に、負極活物質、導電助剤および結着剤を含む混合物(16)が付着させられたものである。集電体(15)としては、たとえば圧延銅箔や、電解銅箔などの銅箔が用いられる。導電助剤としては、ケッチェンブラックやアセチレンブラックなどが用いられるが、これに限定されるものではない。結着剤としては、ポリフッ化ビニリデンが用いられるが、これに限定されるものではない。 The negative electrode (12) is obtained by adhering a mixture (16) containing a negative electrode active material, a conductive additive and a binder on a current collector (15). As the current collector (15), for example, a rolled copper foil or a copper foil such as an electrolytic copper foil is used. As the conductive auxiliary agent, ketjen black or acetylene black is used, but it is not limited to this. As the binder, polyvinylidene fluoride is used, but is not limited thereto.
　正極(13)としては、たとえばＬｉＣｏＯ2からなるものが活物質として用いられ、当該活物質と導電助剤および結着剤との混合物がアルミニウム箔からなる集電体上に付着されたものが用いられるが、これに限定されるものではない。 As the positive electrode (13), for example, a material made of LiCoO 2 is used as an active material, and a mixture of the active material, a conductive additive and a binder is attached on a current collector made of aluminum foil. However, the present invention is not limited to this.
　上述したリチウム二次電池(10)において、充電時には、Ｌｉイオンが負極(12)に含まれる負極活物質の粒子の表面でＬｉイオンを含む化合物が形成されることになり、充電時の負極活物質の粒子の膨張を抑制することができる。また、充電時の膨張が抑制されているので、放電時にＬｉイオンが負極活物質の粒子から出る際の粒子の収縮も小さくなる。その結果、充電・放電の際の負極活物質の粒子の体積変化が小さくなり、充電・放電時の負極活物質の粒子の体積変化が大きくなることに起因する粒子の割れや微粉化、ならびに負極活物質の粒子の導電助剤および結着剤からの剥離を効果的に抑制することができるとともに、充電・放電を繰り返すことによる容量低下が少なくなって、リチウム二次電池(10)のサイクル寿命の長寿命化を図ることが可能になる。 In the lithium secondary battery (10) described above, during charging, a compound containing Li ions is formed on the surface of the particles of the negative electrode active material in which Li ions are contained in the negative electrode (12). Expansion of the particles of the substance can be suppressed. Further, since the expansion during charging is suppressed, the shrinkage of particles when Li ions come out from the particles of the negative electrode active material during discharging is reduced. As a result, the volume change of the negative electrode active material particles during charging / discharging is reduced, and the volume change of the negative electrode active material particles during charging / discharging is increased. Cycles of lithium secondary battery (10) can be effectively prevented from being separated from the conductive auxiliary agent and binder of active material particles, and the capacity decrease due to repeated charging and discharging is reduced. This makes it possible to extend the service life.
　また、リチウム二次電池(10)の初期充放電容量が大きくなるとともに、充放電を繰り返すことによる容量低下が少なくなる。 Also, the initial charge / discharge capacity of the lithium secondary battery (10) is increased, and the capacity reduction due to repeated charge / discharge is reduced.
　上記実施形態においては、この発明による負極活物質がコイン型のリチウム二次電池に用いられているが、これに限定されるものではなく、角型、円筒型、ラミネート型などの公知のリチウム二次電池に用いられる。 In the above embodiment, the negative electrode active material according to the present invention is used in a coin-type lithium secondary battery. However, the present invention is not limited to this, and known lithium secondary batteries such as a square type, a cylindrical type, and a laminate type are used. Used for secondary batteries.
　以下、この発明の具体的実施例を、比較例とともに説明する。
実施例
　市販の中高圧（１７０Ｖ以上）の電解コンデンサ用陽極用に両面エッチングが施されたＡｌ箔を、シュレッダー装置により小片化した後、目開き０．０９０ｍｍのふるい（JIS Ｚ８８０１－１に基づく）からなるスクリーン(32)を有する図１に示す粉砕装置により粉砕して粒子の集合体である粉末を形成した。得られた粉末中の粒子は、目開き０．０９０ｍｍのふるい（JIS Ｚ８８０１－１に基づく）を通過しうる大きさであり、粉末のＢＥＴ法による比表面積は０．５６ｍ2／ｇとなっていた。 Hereinafter, specific examples of the present invention will be described together with comparative examples.
Example A commercially available medium- and high-voltage (170 V or higher) electrolytic capacitor anode was subjected to double-sided etching, and was shredded by a shredder device, and then a sieve having an opening of 0.090 mm (based on JIS Z8801-1) The mixture was pulverized by a pulverizer shown in FIG. 1 having a screen (32) made of a powder to form an aggregate of particles. The particles in the obtained powder have a size that can pass through a sieve having an aperture of 0.090 mm (based on JIS Z8801-1), and the specific surface area of the powder by the BET method is 0.56 m 2 / g. It was.
　ついで、エッチング箔を切断して得られた粒子に、液温３０℃の１Ｎ－ＮａＯＨ水溶液中において２０分間処理した後に、液温６０℃の５Ｎ－ＨＣｌ水溶液中において４０分間処理を施すことによりエッチングを行い、負極活物質をつくった。得られた負極活物質中の粒子は、目開き０．０４５ｍｍのふるい（JIS Ｚ８８０１－１に基づく）を通過しうる大きさであり、負極活物質となる粉末のＢＥＴ法による比表面積は１０．２ｍ2／ｇとなっていた。 Next, the particles obtained by cutting the etching foil were treated in a 1N-NaOH aqueous solution at a liquid temperature of 30 ° C. for 20 minutes and then treated in a 5N HCl aqueous solution at a liquid temperature of 60 ° C. for 40 minutes. The negative electrode active material was made. The particles in the obtained negative electrode active material have a size that can pass through a sieve having an aperture of 0.045 mm (based on JIS Z8801-1), and the specific surface area of the powder as the negative electrode active material by the BET method is 10. It was 2 m 2 / g.
　ついで、負極活物質：９０重量部と、ポリフッ化ビニリデンからなる結着剤：５重量部と、アセチレンブラックからなる導電助剤：５重量部とを混合し、当該混合物を厚み１０μｍの銅箔からなる集電体上に塗布した。その後、上記混合物が塗布された集電体を１ｃｍ2の円形ポンチで打ち抜き、これを負極とした。そして、金属Ｌｉを正極とし、正極と負極との間に気孔率４０vol％のミクロポア構造をしたポリエチレンからなるセパレータを挟み、エチレンカーボネート（ＥＣ）とジメチルカーボネート（ＤＭＣ）との混合溶媒（ＥＣ＋ＤＭＣ＝１：１（体積比））に１mol／リットルのＬｉＰＦ6を溶解させた溶液を電解質とし、露点が－５０℃以下の雰囲気であるドライボックス中でコイン型モデル電池（ＣＲ２０３２タイプ）を作製した。
比較例
　純度が９９．９質量％のＡｌからなる厚さが０．１２ｍｍの市販のアルミニウム箔をシュレッダー装置により小片化した後、ボールミルにより粉砕し、扁平状の粒子の集合体である粉末からなる負極活物質をつくった。得られた負極活物質中の粒子は、目開き０．０５０ｍｍのふるい（JIS Ｚ８８０１－１に基づく）を通過しうる大きさであり、粉末のＢＥＴ法による比表面積は０．０７ｍ2／ｇとなっていた。 Then, 90 parts by weight of the negative electrode active material, 5 parts by weight of a binder made of polyvinylidene fluoride, and 5 parts by weight of a conductive auxiliary agent made of acetylene black were mixed, and the mixture was made from a copper foil having a thickness of 10 μm. It was applied on a current collector. Thereafter, the current collector coated with the above mixture was punched with a 1 cm 2 circular punch, and this was used as a negative electrode. Then, a separator made of polyethylene having a micropore structure with a porosity of 40 vol% is sandwiched between the positive electrode and the negative electrode, and a mixed solvent of ethylene carbonate (EC) and dimethyl carbonate (DMC) (EC + DMC = 1). 1 (volume ratio)) was dissolved in 1 mol / liter LiPF 6 as an electrolyte, and a coin-type model battery (CR2032 type) was produced in a dry box having an atmosphere with a dew point of −50 ° C. or lower.
Comparative Example A commercially available aluminum foil made of Al having a purity of 99.9% by mass and having a thickness of 0.12 mm was shredded by a shredder apparatus, and then pulverized by a ball mill, and made of a powder that is an aggregate of flat particles. A negative electrode active material was made. The particles in the obtained negative electrode active material have a size that can pass through a sieve having an aperture of 0.050 mm (based on JIS Z8801-1), and the specific surface area of the powder by the BET method is 0.07 m 2 / g. It was.
　ついで、負極活物質：９０重量部と、ポリフッ化ビニリデンからなる結着剤：５重量部と、アセチレンブラックからなる導電助剤：５重量部とを混合し、当該混合物を厚み１０μｍの銅箔からなる集電体上に塗布した。その後、上記混合物が塗布された集電体を１ｃｍ2の円形ポンチで打ち抜き、これを負極とした。そして、金属Ｌｉを正極とし、正極と負極との間に気孔率４０vol％のミクロポア構造をしたポリエチレンからなるセパレータを挟み、エチレンカーボネート（ＥＣ）とジメチルカーボネート（ＤＭＣ）との混合溶媒（ＥＣ＋ＤＭＣ＝１：１（体積比））に１mol／リットルのＬｉＰＦ6を溶解させた溶液を電解質とし、露点が－５０℃以下の雰囲気であるドライボックス中でコイン型モデル電池（ＣＲ２０３２タイプ）を作製した。
評価試験
　実施例および比較例において作製したモデル電池について、負極の評価を次の方法で行った。 Then, 90 parts by weight of the negative electrode active material, 5 parts by weight of a binder made of polyvinylidene fluoride, and 5 parts by weight of a conductive auxiliary agent made of acetylene black were mixed, and the mixture was made from a copper foil having a thickness of 10 μm. It was applied on a current collector. Thereafter, the current collector coated with the mixture was punched with a 1 cm 2 circular punch, and this was used as a negative electrode. Then, a separator made of polyethylene having a micropore structure with a porosity of 40 vol% is sandwiched between the positive electrode and the negative electrode, and a mixed solvent of ethylene carbonate (EC) and dimethyl carbonate (DMC) (EC + DMC = 1). 1 (volume ratio)) was dissolved in 1 mol / liter LiPF 6 as an electrolyte, and a coin-type model battery (CR2032 type) was produced in a dry box having an atmosphere with a dew point of −50 ° C. or lower.
Evaluation test About the model battery produced in the Example and the comparative example, the negative electrode was evaluated by the following method.
　まず、モデル電池を、０．２ｍＡ／ｃｍ2の定電流で１Ｖに達するまで充電し、１０分間休止後、０．２ｍＡ／ｃｍ2の定電流で０Ｖに達するまで放電した。これを、１サイクルとし、繰り返し充放電を行って放電容量を調べた。 First, the model battery was charged at a constant current of 0.2 mA / cm 2 until reaching 1 V, rested for 10 minutes, and then discharged at a constant current of 0.2 mA / cm 2 until it reached 0 V. This was defined as one cycle, and charging / discharging was repeated to examine the discharge capacity.
　実施例および比較例において作製したモデル電池におけるサイクル数と放電容量とを表１に示す。 Table 1 shows the number of cycles and the discharge capacity of the model batteries produced in the examples and comparative examples.
Figure JPOXMLDOC01-appb-T000001
 　表１から明かなように、実施例において作製したモデル電池では、比較例において作製したモデル電池と比較して初期放電容量が高くなっているとともに、１００サイクル経過後の放電容量の低下も少なく十分な値を維持していることが分かる。したがって、実施例において作製したモデル電池では、比較例において作製したモデル電池と比較してサイクル寿命の長寿命化が達成されている。
Figure JPOXMLDOC01-appb-T000001
 As is clear from Table 1, the model battery produced in the example has a higher initial discharge capacity than the model battery produced in the comparative example, and the discharge capacity after 100 cycles has decreased sufficiently. It can be seen that this value is maintained. Therefore, in the model battery manufactured in the example, the cycle life is extended as compared with the model battery manufactured in the comparative example.
　この発明によるリチウム二次電池用負極活物質は、リチウム二次電池の負極に好適に用いられ、リチウム二次電池のサイクル寿命の長寿命化を達成することが可能になる。 The negative electrode active material for a lithium secondary battery according to the present invention is suitably used for a negative electrode of a lithium secondary battery, and it is possible to achieve a long cycle life of the lithium secondary battery.

Claims (20)

  1. Ａｌを主成分とする箔をエッチングしてエッチング箔をつくる工程、当該エッチング箔を切断して粒子を得る工程、およびエッチング箔を切断して得られた粒子をさらにエッチングする工程をこの順序で行うことにより形成された粉末からなり、粉末を構成する各粒子が、目開き０．１ｍｍのふるい（JIS Ｚ８８０１－１に基づく）を通過しうる大きさであり、エッチングされた粒子の集合体である粉末のＢＥＴ法による比表面積が１．０ｍ2／ｇ以上となっているリチウム二次電池用負極活物質。 Etching a foil containing Al as a main component to form an etching foil, cutting the etching foil to obtain particles, and further etching the particles obtained by cutting the etching foil are performed in this order. Each particle constituting the powder is a size that can pass through a sieve having a mesh size of 0.1 mm (based on JIS Z8801-1), and is an aggregate of etched particles. A negative electrode active material for a lithium secondary battery, wherein the powder has a specific surface area of 1.0 m 2 / g or more by the BET method.
  2. 前記エッチング箔を切断して得られた粒子が、目開き０．０９０ｍｍのふるい（JIS Ｚ８８０１－１に基づく）を通過しうる大きさであり、前記エッチング箔を切断して得られた粒子の集合体である粉末のＢＥＴ法による比表面積が０．５ｍ2／ｇ以上でかつ１．０ｍ2／ｇ未満となっている請求項１記載のリチウム二次電池用負極活物質。 Particles obtained by cutting the etching foil are sized so as to pass through a sieve having a mesh opening of 0.090 mm (based on JIS Z8801-1), and a set of particles obtained by cutting the etching foil 2. The negative electrode active material for a lithium secondary battery according to claim 1, wherein a specific surface area of the powder as a body by a BET method is 0.5 m 2 / g or more and less than 1.0 m 2 / g.
  3. 前記エッチング後の各粒子が、目開き０．０４５ｍｍのふるい（JIS Ｚ８８０１－１に基づく）を通過しうる大きさである請求項１または２記載のリチウム二次電池用負極活物質。 3. The negative electrode active material for a lithium secondary battery according to claim 1, wherein each of the particles after the etching has a size capable of passing through a sieve having an aperture of 0.045 mm (based on JIS Z8801-1).
  4. 前記エッチング後の前記各粒子の投影周長円相当径が、０．０１０ｍｍ以下である請求項１または２記載のリチウム二次電池用負極活物質。 The negative electrode active material for a lithium secondary battery according to claim 1 or 2, wherein a projected circumference equivalent circle diameter of each of the particles after the etching is 0.010 mm or less.
  5. 前記エッチング後の前記各粒子の投影周長円相当径が、０．００５ｍｍ以下である請求項１または２記載のリチウム二次電池用負極活物質。 3. The negative electrode active material for a lithium secondary battery according to claim 1, wherein a projected circumference equivalent circle diameter of each of the particles after the etching is 0.005 mm or less.
  6. 前記エッチング後の粒子の集合体である粉末のＢＥＴ法による比表面積が１０．０ｍ2／ｇ以上となっている請求項１記載のリチウム二次電池用負極活物質。 2. The negative electrode active material for a lithium secondary battery according to claim 1, wherein the powder, which is an aggregate of particles after etching, has a specific surface area of 10.0 m 2 / g or more by BET method.
  7. 前記Ａｌを主成分とする箔が、純度が９９質量％以上のＡｌからなる請求項１記載のリチウム二次電池用負極活物質。 The negative electrode active material for a lithium secondary battery according to claim 1, wherein the foil containing Al as a main component is made of Al having a purity of 99% by mass or more.
  8. 前記Ａｌを主成分とする箔が、純度が９９．９質量％以上のＡｌからなる請求項１記載のリチウム二次電池用負極活物質。 The negative electrode active material for a lithium secondary battery according to claim 1, wherein the foil containing Al as a main component is made of Al having a purity of 99.9% by mass or more.
  9. 前記エッチング前の粒子が、前記エッチング箔を切断するとともに、圧縮応力が加わる方法で粉砕することにより形成されている請求項１記載のリチウム二次電池用負極活物質。 2. The negative electrode active material for a lithium secondary battery according to claim 1, wherein the particles before etching are formed by cutting the etching foil and pulverizing by a method in which compressive stress is applied.
  10. Ａｌを主成分とする箔をエッチングしてエッチング箔をつくった後、エッチング箔を切断して粒子の集合体である粉末を形成し、ついで粉末を構成する粒子をエッチングすることによって、各粒子を、目開き０．１ｍｍのふるい（JIS Ｚ８８０１－１に基づく）を通過しうる大きさにするとともに、エッチング後の粒子の集合体である粉末のＢＥＴ法による比表面積を１．０ｍ2／ｇ以上にすることを特徴とするリチウム二次電池用負極活物質の製造方法。 After etching the foil containing Al as a main component to form an etching foil, the etching foil is cut to form a powder that is an aggregate of particles, and then the particles constituting the powder are etched to form each particle. In addition, the size should be such that it can pass through a sieve having an aperture of 0.1 mm (based on JIS Z8801-1), and the specific surface area of the powder as an aggregate of particles after etching is 1.0 m 2 / g or more by the BET method. A method for producing a negative electrode active material for a lithium secondary battery.
  11. 前記エッチング箔を切断して得られた粒子を、目開き０．０９０ｍｍのふるい（JIS Ｚ８８０１－１に基づく）を通過しうる大きさにするとともに、前記エッチング箔を切断して得られた粒子の集合体である粉末のＢＥＴ法による比表面積を０．５ｍ2／ｇ以上でかつ１．０ｍ2／ｇ未満にする請求項１０記載のリチウム二次電池用負極活物質。 Particles obtained by cutting the etching foil are sized so as to pass through a sieve having a mesh size of 0.090 mm (based on JIS Z8801-1), and particles obtained by cutting the etching foil The negative electrode active material for a lithium secondary battery according to claim 10, wherein the specific surface area of the powder as an aggregate by the BET method is 0.5 m 2 / g or more and less than 1.0 m 2 / g.
  12. 前記エッチング後の各粒子を、目開き０．０４５ｍｍのふるい（JIS Ｚ８８０１－１に基づく）を通過しうる大きさにする請求項１０または１１記載のリチウム二次電池用負極活物質の製造方法。 The method for producing a negative electrode active material for a lithium secondary battery according to claim 10 or 11, wherein each of the particles after the etching is sized so as to pass through a sieve having an aperture of 0.045 mm (based on JIS Z8801-1).
  13. 前記エッチング後の各粒子の投影周長円相当径を０．０１０ｍｍ以下にする請求項１０または１１記載のリチウム二次電池用負極活物質の製造方法。 The method for producing a negative electrode active material for a lithium secondary battery according to claim 10 or 11, wherein a projected circumference equivalent circle diameter of each particle after the etching is set to 0.010 mm or less.
  14. 前記エッチング後の各粒子の投影周長円相当径を０．００５ｍｍ以下にする請求項１０または１１記載のリチウム二次電池用負極活物質の製造方法。 The method for producing a negative electrode active material for a lithium secondary battery according to claim 10 or 11, wherein a projected circumference equivalent circle diameter of each particle after the etching is 0.005 mm or less.
  15. 前記エッチング後の粒子の集合体である粉末のＢＥＴ法による比表面積を１０．０ｍ2／ｇ以上にする請求項１０記載のリチウム二次電池用負極活物質の製造方法。 The manufacturing method of the negative electrode active material for lithium secondary batteries of Claim 10 which makes the specific surface area by BET method of the powder which is the aggregate | assembly of the particle | grains after the said etching into 10.0 m < 2 > / g or more.
  16. 前記Ａｌを主成分とする箔が、純度が９９質量％以上のＡｌからなる請求項１０記載のリチウム二次電池用負極活物質の製造方法。 The method for producing a negative electrode active material for a lithium secondary battery according to claim 10, wherein the foil containing Al as a main component is made of Al having a purity of 99 mass% or more.
  17. 前記Ａｌを主成分とする箔が、純度が９９．９質量％以上のＡｌからなる請求項１０記載のリチウム二次電池用負極活物質の製造方法。 The method for producing a negative electrode active material for a lithium secondary battery according to claim 10, wherein the foil containing Al as a main component is made of Al having a purity of 99.9% by mass or more.
  18. 前記エッチング箔を切断するとともに、圧縮応力が加わる方法により粉砕して粒子の集合体である粉末を形成する請求項１０記載のリチウム二次電池用負極活物質の製造方法。 The method for producing a negative electrode active material for a lithium secondary battery according to claim 10, wherein the etching foil is cut and pulverized by a method in which a compressive stress is applied to form a powder that is an aggregate of particles.
  19. 集電体上に、請求項１に記載された負極活物質、導電助剤および結着剤を含む混合物質が付着されているリチウム二次電池用負極。 A negative electrode for a lithium secondary battery, wherein a mixed material containing the negative electrode active material, the conductive additive, and the binder according to claim 1 is attached on a current collector.
  20. 請求項１９記載の負極と、セパレータと、リチウム二次電池用正極とを備えているリチウム二次電池。 A lithium secondary battery comprising the negative electrode according to claim 19, a separator, and a positive electrode for a lithium secondary battery.
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JPH08213053A (en) * 1994-12-02 1996-08-20 Canon Inc Lithium secondary battery
WO2012050079A1 (en) * 2010-10-12 2012-04-19 昭和電工株式会社 Negative electrode material for lithium secondary cell
WO2012073815A1 (en) * 2010-11-30 2012-06-07 昭和電工株式会社 Negative pole active substance for lithium secondary battery and method for producing same

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Publication number Priority date Publication date Assignee Title
JPH08213053A (en) * 1994-12-02 1996-08-20 Canon Inc Lithium secondary battery
WO2012050079A1 (en) * 2010-10-12 2012-04-19 昭和電工株式会社 Negative electrode material for lithium secondary cell
WO2012073815A1 (en) * 2010-11-30 2012-06-07 昭和電工株式会社 Negative pole active substance for lithium secondary battery and method for producing same

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