JP2000195505A - Manufacture of negative electrode material for nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease initial irreversible capacity, and to enhance the cycle characteristics and capacity by bringing a negative electrode raw material into contact with a solution prepared by dissolving alkali metals or an alkaline earth metals in an amine compound solvent to adsorb these metals. SOLUTION: As alkali metals or alkaline earth metals used, Li, Na, K, and Ca are preferable. As a solvent for dissolving these metals, use of an amine compound that does not lose a reducing function of metal by reaction is essential, and use of ethylamine and ethylene diamine is especially preferable. The concentration of metal in a metal solution is usually 2-10 wt.%. As a negative electrode raw material, composite tin oxide and composite silicon oxide are especially preferable. In order to bring the negative electrode raw material into contact with a solution of metal such as an alkali metal, for example, a reaction bath with stirring blades is used to mix a solid with liquid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a novel negative electrode material for a non-aqueous electrolyte secondary battery used as a negative electrode active material. More specifically, the present invention relates to a method for producing a negative electrode material for a non-aqueous electrolyte secondary battery which is suitably used for a non-aqueous electrolyte secondary battery such as a lithium ion battery having a reduced irreversible capacity.

[0002]

2. Description of the Related Art A lithium ion battery, which is a typical non-aqueous electrolyte secondary battery, has a positive electrode made of a positive electrode active material capable of occluding and releasing lithium ions and a current collector. It is composed of a negative electrode composed of a negative electrode active material that can be released and a current collector, an electrolyte solution in which a lithium salt is dissolved in a non-aqueous solvent, a separator, a battery container, and the like. In recent years, the demand has been rapidly increasing.

[0003] In the lithium ion battery, lithium ions released from the positive electrode active material during charging are occluded in the negative electrode active material, and lithium ions occluded in the negative electrode active material are discharged during discharging to form the positive electrode active material. It is occluded inside. For this reason, the charge / discharge capacity, which is one of the important characteristics of the lithium ion battery, is strongly affected by the negative electrode active material used. Lithium ion batteries currently in practical use use carbon as a negative electrode active material, and it has been reported that their charge / discharge capacity also shows a value of 600 mAh / g. The charge / discharge capacity is not sufficient in terms of the capacity per unit, and in order to achieve a higher charge / discharge capacity, a negative electrode active material having a higher lithium ion occlusion ability and release ability has been studied.

[0004] It is known that tin oxide has a property of absorbing and releasing lithium ions, and it has been studied for a long time to use tin oxide as an electrode active material of a lithium ion battery using this property. (DEJAN.P.IL
IC et al. Serb. Chem. Soc. , 51 volumes,
489-495, 1986). And recently, Sn
The charge / discharge capacity of a lithium ion battery using tin oxide such as O or SnO2 as a negative electrode active material is 500 to 600 mAh.
/ G (for example, JP-A-6-275268 and JP-A-7-122274). Since the specific gravity of the tin oxide is about 2 to 4 times higher than that of carbon, the charge / discharge capacity per volume is increased. Has been attracting attention as a negative electrode active material that provides a lithium ion battery having a high density.

However, when SnO or SnO ₂ is used as the negative electrode active material, the difference between the charge capacity and the discharge capacity at the time of the first charge / discharge (irreversible capacity) is large, and the initial charge / discharge capacity is high but the charge / discharge capacity is high. It was found that the charge / discharge capacity was reduced as was repeated. After that, various composite tin oxides obtained by adding a second element to tin oxide have been studied for the purpose of improving the stability (cycle characteristics) and further increasing the charge / discharge capacity. Until now Sn-L
i-O-based materials (JP-A-7-201318), Sn
-Si-O-based materials (JP-A-7-230800),
Alternatively, composite tin oxides such as Sn-MO-based materials (where M is an alkaline earth metal, an element of Group 13, 14, 15 or zinc, as disclosed in JP-A-7-288123) are being studied. .

Further, as a method for producing a composite tin oxide powder containing a second element such as silicon, a mixture of silicon oxide powder and tin oxide powder is used as a raw material powder, and the raw material powder is melted at a high temperature to vitrify it. A method (melting method) of crushing a vitrified lump after cooling and pulverizing the mass has been studied (JP-A-7-288123), and the composite tin oxide powder obtained by the melting method is It is said that when used as a negative electrode active material of a lithium secondary battery, the charge / discharge capacity is high and the cycle characteristics are also improved. However, the cycle characteristics of the composite tin oxide were not yet sufficiently satisfactory. The present inventors have found and proposed that the composite tin oxide synthesized by a specific sol-gel method has improved cycle characteristics (Japanese Patent Application No. 10-108608).

However, any of the above oxides / composite oxides still has a large irreversible capacity at the time of initial charge and discharge.
When designing the battery, it is necessary to add an extra amount of the positive electrode active material corresponding to the irreversible capacity, which causes a problem that the capacity of the battery decreases and the cost increases.

As a method for reducing the irreversible capacity, a negative electrode active material is immersed in a solution in which lithium is dissolved in liquid ammonia or a solution in which n-butyllithium is dissolved in an organic solvent such as hexane. A method for sorbing lithium has been studied (JP-A-10-29).
4104).

However, when a liquid ammonia solution of lithium is used, the handling is difficult because the boiling point of ammonia is low and it is necessary to keep the temperature at a low temperature of −33.4 ° C. or lower, which is the boiling point of ammonia. Further, even when the negative electrode active material is immersed in a liquid ammonia solution of lithium, not all of the dissolved lithium is sorbed to the negative electrode active material, and unreacted lithium remains in the ammonia. For this reason,
When the temperature is equal to or higher than the boiling point of ammonia and ammonia evaporates, the ammonia and lithium react to generate lithium amide, and when contained as impurities, the capacity of the active material is reduced and the lithium amide generation reaction is rapid. There was also a problem in terms of safety due to the generation of hydrogen. In addition, when a solution in which n-butyllithium is dissolved in an organic solvent is used, since the reducing power is weak, lithium is not sufficiently absorbed, and the effect of reducing the initial irreversible capacity is small.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a high capacity nonaqueous electrolyte secondary battery negative electrode material having a small initial irreversible capacity and excellent cycle characteristics.

[0011]

Means for Solving the Problems In order to solve the above problems, the present inventors have studied an easy-to-handle and safe sorption method of alkali metal or alkaline earth metal by chemical treatment. . As a result, by bringing the negative electrode raw material into contact with a metal solution in which an alkali metal or an alkaline earth metal is dissolved in an amine compound solvent, the alkali metal or alkaline earth metal dissolved in the metal solution is contained in the negative electrode raw material. And found that the irreversible capacity of the obtained non-aqueous electrolyte secondary battery negative electrode material is reduced,
The present invention has been completed.

That is, the present invention provides a method for producing a non-aqueous electrolyte secondary battery by contacting a negative electrode raw material for a non-aqueous electrolyte secondary battery with a metal solution in which an alkali metal or an alkaline earth metal is dissolved in an amine compound solvent. The present invention relates to a method for producing a negative electrode material for a non-aqueous electrolyte secondary battery, which comprises sorbing an alkali metal or an alkaline earth metal to a negative electrode raw material for a battery. The present invention relates to a non-aqueous electrolyte secondary battery using a negative electrode material for an aqueous electrolyte secondary battery as an active material of a negative electrode.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The type of alkali metal or alkaline earth metal used in the present invention is not particularly limited, but lithium, sodium, potassium, calcium and the like are preferable. It is particularly preferable to select and use the same metal as the metal used for the electrolyte or the like of the nonaqueous electrolyte secondary battery depending on the type of the nonaqueous electrolyte secondary battery.

In the present invention, it is essential to use, as a solvent for dissolving the alkali metal or the alkaline earth metal, an amine compound solvent capable of dissolving the metal without losing the reducing ability of the metal by the reaction with the solvent.

Preferred amine compound solvents include methylamine, ethylamine, ethylenediamine, hexamethylphosphamide, 1,3-dimethyl-2-oxohexahydropyrimidine, etc. Ethylamine and ethylenediamine have a high boiling point and are easy to handle. It is particularly preferable because the irreversible capacity after the treatment also becomes small. Also,
These amine compound solvents may be used as a mixed solvent by adding an organic solvent (hereinafter, the amine compound single solvent and the mixed solvent are collectively referred to simply as a solvent). The amount of the organic solvent to be mixed is such that the larger the amount, the lower the solubility of the metal. Therefore, the volume ratio at the time of mixing, that is, [organic solvent] /
[Amine compound solvent] The volume ratio is preferably 2/3 or less. As the organic solvent to be mixed, a compound which does not contain a functional group having high reactivity with the metal such as a hydroxyl group or a carbonyl group, specifically, diethyl ether, tetrahydrofuran, or the like is preferably used.

Although the concentration of the alkali metal or alkaline earth metal in the metal solution is not particularly limited, it is preferable to use a higher concentration solution in order to make the reaction proceed efficiently, usually about 2 to 10% by weight. Use solution.

The method for dissolving an alkali metal or an alkaline earth metal into a metal solution is not particularly limited. The metal can be added to the solvent, or the solvent can be added to a container containing the metal. However, since heat is generated during dissolution, it is preferable to gradually dissolve the metal in the solvent. In addition, in order to safely prepare a metal solution, an electrode is placed in a solution obtained by dissolving a salt of the above metal which can be dissolved in the above solvent in the solvent, and current is passed using the electrode as a cathode to reduce dissolved metal ions. However, a metal solution can also be used.

The method for bringing the negative electrode raw material for the nonaqueous electrolyte secondary battery into contact with an alkali metal or alkaline earth metal solution is not particularly limited. In order to promote the reaction efficiently, a solid-liquid mixture can be used using a reaction layer equipped with a stirring blade, or a metal solution can be circulated using a flow-type reactor and brought into contact with the negative electrode raw material. it can. Also,
The solvent may be suspended in advance with the solvent and the negative electrode raw material, and the metal may be dissolved in the suspension, or the raw material and the solvent may be brought into contact with the metal at the same time as the metal is dissolved in the solvent. The temperature at which the negative electrode raw material is brought into contact with the metal solution is not particularly limited, but is preferably set to be equal to or lower than the boiling point of the solvent.

In the production method of the present invention, since all of the metals in the solution are not sorbed to the negative electrode raw material and unreacted metals may remain in the solution, filtration and washing are performed after the treatment. Is preferred. The solvent to be washed is preferably a solvent that does not contain water and does not contain a functional group having high reactivity with the above-mentioned metals such as a hydroxyl group and a carbonyl group, and ethers such as diethyl ether and tetrahydrofuran are particularly preferable.

Since the metal solution used in the present invention has a very large reducing power and reacts with nitrogen in the atmosphere to form a nitride, the steps of dissolving the metal, contacting with the raw material, filtering and washing are carried out. It is preferable to carry out the reaction under an inert gas atmosphere, particularly preferably under an argon gas atmosphere.

As the negative electrode raw material for the non-aqueous electrolyte secondary battery used in the production method of the present invention, SnO, SnO ₂ ,
SiO, GeO, ZnO, CdO, PbO, PbO ₂ ,
Sb ₂ O ₃ , composite tin oxide, composite silicon oxide, SnS, Si
C, chalcogenides, silicon alloys such as SiFe alloys, SiNi alloys, tin alloys such as SnNi alloys, Mg ₂
A CaF ₂ -type alloy such as Ge may be mentioned, but composite tin oxide / silicon oxide is particularly preferable because deterioration in performance when charge / discharge cycles are repeated is small. The form of the raw material is not particularly limited.
It is preferably in the form of a powder in order to allow the liquid reaction to proceed efficiently.

The case where the negative electrode raw material of the nonaqueous electrolyte secondary battery is a composite tin oxide will be described in detail below.

The composite tin oxide is composed of tin and a composite oxide of a second element capable of forming a composite oxide with tin. The ratio of tin to the total amount of tin and the second element in the composite oxide is not particularly limited, but is preferably 30 atomic% or more. When the ratio is less than 30 atomic%, the discharge capacity becomes small.
When the above ratio is 30 to 70 atomic%, the amount of lithium ions absorbed and released is large and the change with time is small, and it is particularly suitable for use as a negative electrode active material for a non-aqueous electrolyte secondary battery.

The second element is an alkaline earth metal element such as Ca, Sr or Ba; La, Ce, Pr, Nd, Sm,
Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, L
rare earth elements such as u; Sc, Ti, V, Cr, Mn, F
e, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo,
Ru, Cd, Hf, Ta, W, Re, Os, Ir, P
transition elements such as t, Au, Hg; B, Al, Ga, In,
Group 13 elements of the periodic table such as Tl; elements of Group 14 of the periodic table excluding carbon and tin such as Ge, Si and Pb; P, As, Sb,
Bi and other chalcogen elements such as S, Se, and Te. Here, the reason why carbon is excluded from the Group 14 elements of the periodic table is that carbon is difficult to form a complex oxide via tin and oxygen.

The second element contained in the composite tin oxide may be one of the above-mentioned elements or a combination of any two or more of them. Sn-Si is preferably used as a tin-second element combination. , Sn-Si-Al, Sn-Si-
Zr, Sn-Si-B, Sn-Si-P, Sn-Si-
Ti, Sn-Si-Al-B, Sn-Si-Zr-B,
Sn-Si-BP, Sn-Al, Sn-Al-B, S
n-Al-P, Sn-Al-Zr, Sn-Al-B-
P, Sn-Zr, Sn-Zr-B, Sn-Zr-P, S
n-Zr-BP, Sn-BP, Sn-Ti, Sn-
Ti-Al, Sn-Ti-B, Sn-Ti-P, Sn-
Ti-BP, Sn-Ti-Zr, and the like. Among these, when the second element is silicon or a combination of silicon and another second element, when used as a negative electrode active material for a non-aqueous electrolyte secondary battery such as a lithium ion battery, lithium ion Is preferred because it has a large amount of occlusion and release, and also has particularly excellent cycle characteristics.

Since the composite tin oxide is a composite oxide of tin and the second element as described above, it naturally contains an oxygen atom. Since the oxygen atom is present in combination with tin and the second element, its content is almost uniquely determined by the tin atom content and its valence and the type, content and valence of the second element. Is done. However, tin and some of the second elements are unbonded (so-called dangling bonds)
And about 10 atomic% of oxygen atoms may be replaced by halogen atoms such as fluorine, chlorine, bromine and iodine. The valences of tin and the second element in the composite tin oxide particles are not particularly limited.

The crystalline state of the composite tin oxide is not particularly limited as long as it has the above composition.
Since the element that bonds to tin via an oxygen atom is a second element more than a tin atom, the cycle characteristics are more improved.
It is preferable that tin oxide crystals such as O and SnO ₂ do not exist, and in that sense, amorphous is more preferable than crystalline. In addition, even in the case of an amorphous material, in order to further increase the occlusion / release amount of lithium ions and to achieve particularly excellent cycle characteristics, a dense glass material produced by melting (here, glass material) Is a composite tin oxide obtained by a specific sol-gel reaction.

The composite tin oxide obtained by a specific sol-gel method has a low Sn—O—Sn bond ratio, and has many fine pores and the like in the particles. It is possible to absorb (relax) a stress based on a volume change that occurs when releasing or releasing. As a result, even if lithium ions are repeatedly inserted and extracted, the particles are not cracked, and a better cycle characteristic is exhibited.

A typical method for producing a preferred composite tin oxide is described below. Methanol, SnCl ₂ alcohol 20% mole of tetraethoxysilane and tetraethoxysilane such as ethanol is added to obtain a clear homogeneous solution by dissolving Stirring under. Oxygen is supplied to this solution to oxidize tin in the solution to tetravalent, and then nitrogen is supplied to sufficiently dissolve the dissolved oxygen. Then, under a nitrogen atmosphere, 80% mol of SnCl in tetraethoxysilane is added. ₂ is dissolved to prepare a transparent homogeneous solution (hereinafter, also referred to as solution A). On the other hand, 29% ammonia water is added to alcohols such as methanol and ethanol so that the molar ratio of SnCl ₂ to NH _{3 in} solution A is 1.0 to 1.4, and a uniform solution (hereinafter also referred to as solution B). Get. A reaction tank is charged with alcohol such as methanol and ethanol, and stirred under a nitrogen atmosphere.
The solution and the solution B are gradually and simultaneously dropped at a constant speed so that the time required for dropping is equal. After completion of the dropwise addition, the white precipitate formed is separated by filtration, washed with water, dried by heating at 100 ° C. under vacuum, and further calcined at 400 ° C. for 1 hour in an argon atmosphere to obtain a pale yellow composite tin oxide powder. .

The composite silicon oxide has a composition formula of Si1-xMxOy.
(Where 0 <x <1, 1 ≦ y <2), and M is a metal excluding an alkali metal or a similar metal excluding Si. The value of x may be within the above range, but if the value is too small, the cycle characteristics when used as a negative electrode active material is poor, and if it is too large, the capacity may decrease depending on the type of M. From the viewpoint of high capacity, y is preferably a value closer to 1.

The construction and production of a non-aqueous electrolyte secondary battery using the negative electrode material of the non-aqueous electrolyte secondary battery produced according to the present invention can be carried out by a known method. It can be manufactured by such a method.

First, using a kneader, a mixer or the like, the composite tin oxide obtained by the production method of the present invention is kneaded with a solvent such as N-methylpyrrolidone to produce a paste. At this time, a conductivity-imparting agent such as graphite or acetylene black,
Alternatively, a binder such as polytetrafluoroethylene and polyvinylidene fluoride may be appropriately added.

After the paste is manufactured, the current collector is coated, filled or impregnated with the paste, and the solvent is dried and removed.
Pressing, cutting, and the like are performed to form a desired shape to obtain a negative electrode. The negative electrode and the positive electrode manufactured in the same manner are stacked in a strip shape with a separator interposed therebetween, and if the battery is a cylindrical nonaqueous electrolyte secondary battery, it is wound in a columnar shape, and if it is a square nonaqueous electrolyte secondary battery, It is folded to produce an electrode part. Thereafter, the electrode portion is inserted into a desired battery container, a non-aqueous electrolyte is injected, a safety device or the like is inserted, and the can is sealed.

For the positive electrode, the current collector, the non-aqueous electrolyte, the separator, and the like, materials used in conventional non-aqueous electrolyte secondary batteries are used without any problem.

As the positive electrode active material, TiS ₂ , MoS ₂ ,
Chalcogen compounds such as sulfides such as FeS ₂ , selenides such as NbSe ₃ , or Cr ₂ O ₅ , Cr ₃ O ₈ , V
Oxides of transition metals such as ₃ O ₈ , V ₂ O ₅ , V ₆ O ₁₃ , Li
Mn ₂ O ₄ , LiMnO ₂ , LiV ₃ O ₅ , LiNiO ₂ , L
a composite oxide of lithium and a transition metal, such as iCoO ₂ ;
Alternatively, a material capable of inserting and extracting lithium, such as a conjugated polymer such as polyaniline, polyacetylene, polyparaphenylene, polyphenylenevinylene, polypyrrole, or polythiophene, or a crosslinked polymer having a disulfide bond, can be used.

As the current collector, a band-shaped thin plate or mesh made of copper, aluminum, or the like can be used.

Examples of the non-aqueous electrolyte include propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone,
LiClO ₄ , LiPF ₆ may be used alone or in a mixture of two or more kinds of non-aqueous solvents such as tetrahydrofuran, 1,3-dioxolan, 4-methyl-1,3-dioxolan, diethyl ether, sulfolane, methylsulfolane, acetonitrile, propionitrile and the like. , LiAsF ₆ , LiB
F ₄ , LiB (C ₆ H ₅ ) ₄ , LiCl, LiBr, CH _{3
SO 3 Li, CF 3 SO 3} Li nonaqueous electrolyte lithium salt is dissolved, such as can be also be used in any combination.

As the separator, a separator having low resistance to the movement of ions and having excellent solution retention may be used. For example, a polymer pore filter made of polypropylene, polyethylene, polyester, polyflon, or the like, a glass fiber filter, a nonwoven fabric, or a nonwoven fabric made of glass fibers and these polymers can be used. Further, when the temperature inside the battery becomes high, a material that melts to close the pores and prevent short circuit between the positive electrode and the negative electrode is preferable.

[0039]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples.

Example 1 Tetraethoxysilane 41.9 in 920 ml of methanol
3 g (0.2 mol) and 27.59 g of SnCl (0.0
4 mol) and dissolved with stirring to obtain a clear homogeneous solution. Under stirring, 500 ml of oxygen per minute was supplied into this solution for 30 minutes to oxidize tin in the solution to tetravalent, and then 500 ml of nitrogen per minute was supplied for 50 minutes, and then SnCl ₂ 3 was added.
0.34 g (0.16 mol) was dissolved to prepare a transparent homogeneous solution (hereinafter also referred to as solution A).

On the other hand, 34.28 g of 28% aqueous ammonia was added to 50.5 ml of methanol to obtain a uniform solution (hereinafter also referred to as solution B).

In a 1-liter three-necked flask in which a pair of nozzles for dropping A droplets and for dropping B droplets were respectively installed on two side tubes,
Charge 80 ml of methanol and stir at 750 rpm using a magnetic stirrer and 500
10 ml of nitrogen into methanol from the inner tube of a three-necked flask.
Minutes. Then, while continuously stirring and supplying nitrogen, the solution A and the solution B were each supplied to the two pipes using a pair of nozzles at a rate of 2.0 m / nozzle using a tube pump.
It was dropped into methanol in a three-necked flask at a dropping rate of 1 / min and 0.18 ml / min. At this time, the temperature of the solution in the three-necked flask was set to 20 ° C. using a water bath. A precipitate was formed with the addition of the solution A and the solution B, and the solution in the three-necked flask became cloudy. After the dropping of the solution A and the solution B was completed, the stirring and the supply of nitrogen were continued for another 30 minutes, and the formed white precipitate was separated by filtration and washed with water. The washed precipitate is removed under vacuum for 10 minutes.
It is dried by heating to 0 ° C.
Calcination at 0 ° C. for 1 hour gave a pale yellow powder. The powder was not melted during the firing.

As a result of composition analysis and crystal state analysis of the obtained powder, the atomic ratio Sn / Si of tin to silicon in the composite tin oxide constituting the powder was 1.03, The state was amorphous.

The above analysis was performed as follows.

Composition analysis: Conducted by X-ray fluorescence analysis.

Crystal state analysis: Diffraction from the sample in the range of 2θ of 10 to 40 ° was measured by powder X-ray diffraction (copper is copper), and the crystal phase in the sample was identified from the measured crystallinity peak. did. When no crystalline peak was observed, the crystallinity of the sample was determined to be amorphous.

Under an argon atmosphere, ethylenediamine 5 m
In a flask containing 1 l, 0.15 g of metallic lithium was dissolved, and 1 g of the composite oxide was added thereto. After stirring for 8 hours with a magnetic stirrer, the mixture was filtered under an argon atmosphere, washed with diethyl ether, and dried in vacuum to obtain a black powder.

Example 2 In Example 1, lithium was sorbed in the same manner as in Example 1 except that SnO was used instead of the composite tin oxide as the negative electrode raw material, and the weight of lithium was changed to 0.2 g, to obtain a powder. Was.

Example 3 In Example 1, lithium was sorbed in the same manner as in Example 1 except that SiO was used instead of the composite tin oxide as the negative electrode raw material, and the weight of lithium was changed to 0.6 g. Was.

Example 4 The bath composition was 200 g / l potassium pyrophosphate, 20 g / l glycine, 30 g / l nickel chloride, 7 g stannous chloride.
The nickel electrode was put into a plating bath whose pH was adjusted to 8.8 with ammonia at / l, and a cathode current was passed through the nickel electrode to perform electrodeposition. At this time, the current density was 4 A / dm ² ,
The bath temperature was 50 ° C. The metal deposited on the cathode was peeled off, washed with water, and dried. The obtained metal powder was dissolved in aqua regia, and the composition was analyzed by inductively coupled high frequency plasma atomic emission spectrometry. As a result, the molar ratio was Sn: Ni = 1: 1.
Met. Lithium was sorbed in the same manner as in Example 1 except that the obtained metal powder was used instead of the composite tin oxide as a negative electrode active material in Example 1, to obtain a powder.

Examples 5 to 8 Using the powders obtained in Examples 1 to 4 as negative electrode active materials, lithium batteries were prepared, and the charge / discharge capacities and cycle characteristics of the obtained lithium batteries were evaluated. .

The production of the lithium battery and the evaluation of the initial charge / discharge capacity and the cycle characteristics were performed as follows.

Preparation of lithium battery: The composite tin oxide powder of each example, polyvinylidene fluoride (binder) and acetylene black (conductivity imparting agent) were mixed at a ratio of 70/5/25 (weight ratio). For 500 mg of this mixture,
1 ml of N-methylpyrrolidone was added and kneaded to prepare a paste, which was applied to a copper foil, dried in a vacuum drier at 100 ° C. for 24 hours, and then rolled to obtain a negative electrode. As the non-aqueous electrolyte, a solution in which LiPF ₆ (concentration of 1 mol / liter) was dissolved in an equal volume mixed solvent of ethylene carbonate and diethyl carbonate was used, and a coin-type battery was produced using lithium metal as a counter electrode.

Measurement of charge / discharge capacity: Using a charge / discharge device (manufactured by Hokuto Denko), a charge / discharge cycle test of the simple lithium battery was performed, and a discharge time t (unit: time) was measured to obtain a negative electrode active material. Of the first cycle was measured. The charge / discharge cycle test was performed at a current value (constant) corresponding to 48 mA / g, and the charge / discharge was performed within a range of 0 to 2.0 V. The charge / discharge capacity was calculated as an amount per unit weight of the active material added to the paste. That is, the charge / discharge capacity of acetylene black as the conductivity imparting agent is 0.
The calculation was performed as follows. The irreversible capacity was calculated from the charge capacity and the discharge capacity in the first cycle of charge and discharge. Example 1
Table 1 shows the evaluation results of the negative electrode active material of No. 4. The negative electrode active material treated according to the present manufacturing method has a slightly smaller discharge capacity than the untreated one by the weight of lithium because the irreversible capacity of lithium is absorbed in the active material. The irreversible capacity has been significantly reduced by the sorption. Therefore, LiCoO _{2 is} used as the positive electrode active material.
In an actual battery using such a method, the substantial capacity of the battery is greatly improved.

Comparative Examples 1 to 4 The same procedures as in Example 5 were carried out except that the powder used as the negative electrode active material was changed to the composite tin oxide, SnO, SiO obtained in Example 1 and SnNi obtained in Example 4. A lithium battery was prepared in the same manner, and the lithium battery obtained in the same manner as in Example 5 was evaluated. The results are shown in Table 1.

[0056]

[Table 1]

[0057]

By using the negative electrode material of the nonaqueous electrolyte secondary battery obtained by the present invention as a negative electrode active material,
Since the irreversible capacity can be reduced, the amount of the cathode active material that has been added extra can be reduced, so that a high-capacity lithium secondary battery can be manufactured. In addition, the method using a liquid ammonia solution of lithium, which is a conventional technique, is difficult to handle due to the low boiling point of ammonia, and has a problem in safety. Further, when a solution in which n-butyllithium was dissolved in an organic solvent was used, lithium was not sufficiently absorbed, and the effect of reducing the initial irreversible capacity was small because the reducing power was weak. However, by using the production method of the present invention, the initial irreversible capacity can be reduced more safely and easily, and the effect is large.

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Claims (4)

[Claims] 1. A negative electrode raw material for a non-aqueous electrolyte secondary battery,
Contacting a metal solution in which an alkali metal or an alkaline earth metal is dissolved in an amine compound solvent to cause the alkali metal or the alkaline earth metal to sorb to the negative electrode raw material for the nonaqueous electrolyte secondary battery. A method for producing a negative electrode material for a non-aqueous electrolyte secondary battery. 2. The non-aqueous electrolyte secondary battery negative electrode raw material is S
nO, SnO ₂ , SiO, GeO, ZnO, CdO, P
_{bO, PbO 2, Sb 2 O} 3, composite tin oxide, composite oxide of silicon, SnS, SiC or method of manufacturing a non-aqueous electrolyte secondary battery negative electrode material according to claim 1, characterized in that the chalcogenide. 3. The negative electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein the negative electrode raw material of the non-aqueous electrolyte secondary battery is a silicon-based alloy, a tin-based alloy, or a CaF2-type alloy. Material manufacturing method. 4. A non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, a non-aqueous electrolyte, and a separator as basic components and housed in a container, wherein the active material of the negative electrode is obtained by the method according to claim 1. A nonaqueous electrolyte secondary battery, which is the obtained nonaqueous electrolyte secondary battery negative electrode material.