JPH11135115A - Negative electrode material for nonaqueous secondary battery and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new negative electrode material for a nonaqueous electrolyte secondary battery with high voltage, high capacity, satisfactory charging/ discharging cycle characteristics, and provide its manufacturing method. SOLUTION: A semiconductor thin film of an element or the compound of at least one kind selected from among groups IIIB, IVB, VB of the periodic table, capable of inserting/releasing lithium ions is used as the negative active material of a negative electrode, a metal oxide containing transition metals as the constituting element is used as the positive active material of a positive electrode, and a lithium ion conductive nonaqueous electrolyte prepared by dissolving a lithium compound in an organic solvent, or holding an organic solvent containing a lithium compound as a solid solution or in which a lithium compound is dissolved in a polymer is used as an electrolyte. By assembling these positive electrode, negative electrode and electrolyte, a nonaqueous electrolyte secondary battery with high capacity, high voltage, and satisfactory charging/discharging cycle characteristics is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a non-aqueous secondary battery, and more particularly, to a negative electrode material for a non-aqueous secondary battery.

[0002]

2. Description of the Related Art In a non-aqueous secondary battery having a voltage of 3V class, a method of using metallic lithium as a negative electrode active material and a transition metal oxide represented by Co, Mn and Ni as a positive electrode active material is typical. It is a target. However, when metallic lithium is used for the negative electrode, the metallic lithium grows in a dendritic form (dendrite) during charge and discharge, causing a short circuit inside, and the dendrite has high activity and there is a risk of ignition. is there. For this reason, fired carbonaceous materials capable of inserting and releasing lithium ions as active materials instead of metallic lithium have been put to practical use as negative electrodes. However, carbon materials have the disadvantage of low capacity per volume.

Therefore, lithium ion can be inserted and released as a negative electrode active material which can be expected to have a high capacity per volume. 1) TiS ₂ , LiTiS ₂ (US Pat. No. 3,984,347)
6) transition metal chalcogen compounds, 2) transition metal oxides having a rutile structure, for example, WO ₂ (US Pat. No. 419)
8476), 3) LixFe (Fe 2) spinels such as O ₄ (JP 58-220362), 4) electrochemically synthesized Fe ₂ O ₃ of a lithium compound (U.S. Patent No. 4464447), Fe Lithium compound of ₂ O ₃ (JP-A-3-112070), Nb ₂ O ₅ (JP-A-62-59)
412, JP-A-2-82447), iron oxide, Fe
O, Fe ₂ O ₃ , Fe ₃ O ₄ , cobalt oxide, CoO, Co
Transition metal oxides such as ₂ O ₃ and Co ₃ O ₄ (Japanese Patent Application Laid-Open No. 3-291962) are known. On the other hand, 5) Sn, Cd (Proc) which is known to form an alloy with lithium
eatings of the Electroche
medical Society, 87-1, 1987) A
1 (Solid StateIonics, 20, 19)
86), Si, Pb, Bi, Sb (Proceedin
gs of the Electrochemical
Society, 87-1, 1987) and their alloys with lithium (for example, JP-A-7-29602) have been proposed.

[0004]

However, since the above-mentioned negative electrode active material is usually obtained as a powder, when preparing an electrode, a powdery negative electrode active material is added to an organic solvent in which a conductive additive is added and a binder is dissolved. A method is used in which a substance is added to form a paste, applied to a current collector, and then dried by heating to remove the solvent. However, depending on the coating method, the formation of aggregates of powder particles cannot be suppressed, and it is difficult to disperse the powder particles of the negative electrode active material into primary particles. As a result, the electrical resistance of the electrode increases, resulting in a low operating voltage.In addition, the current collection is insufficient, and the high utilization rate of the negative electrode active material during high-speed charging and discharging when a large current flows causes a sufficient charge / discharge capacity to be drawn out. It is not at present. Therefore, an object of the present invention is to provide 1) a negative electrode active material capable of reversibly inserting and releasing a large amount of lithium ions and reducing the electric resistance of the negative electrode, and 2) a method for producing the negative electrode active material. An object of the present invention is to provide a non-aqueous secondary battery having high capacity and excellent charge / discharge characteristics.

[0005]

In order to achieve the first object, the negative electrode active material of the present invention comprises one or more kinds of periodic tables IIIB and I which insert and release lithium ions.
It is a semiconductor thin film made of an element selected from the group consisting of VB and VB or a compound thereof. The second object is to use a vapor deposition method, a sputtering method, an ion plating method, a CV method on a copper or stainless steel substrate used as a current collector.
This is achieved by manufacturing the semiconductor thin film using any one method selected from vacuum thin film manufacturing methods such as Method D. Further, the semiconductor thin film manufactured by the above-described vacuum thin film manufacturing method is heat-treated under vacuum. Third
The purpose of the present invention is to use a semiconductor thin film of the present invention as a negative electrode active material, a metal oxide containing a transition metal as a constituent element as a positive electrode active material, and dissolve a lithium compound in an organic solvent or dissolve a lithium compound in a polymer. Alternatively, this is achieved by forming a nonaqueous secondary battery using a lithium ion conductive nonaqueous electrolyte holding an organic solvent in which a lithium compound is dissolved as an electrolyte.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The elements used in the present invention include B and A in Group IIIB of the periodic table.
1, Ga, In, Tl, IVB group C, Si, Ge, S
n, Pb, and N, P, As, Sb, Bi of the VB group. As a simple substance, Si, C, Ge, and Sn are preferable. As the compound, a semiconductor capable of inserting and releasing lithium ions is desirable.
nBi, Bi ₃ In ₅ , BiIn ₂ , InSb, InA
s, InP, InN, GaSb, GaAs, GaP, G
Compound semiconductors such as aN, Tl ₅ Sb, Sb ₅ Tl ₇ , Bi ₂ Tl, and AlSb are exemplified.

As the conductive metal or alloy used as the current collector, any one commonly used for a negative electrode of a non-aqueous secondary battery can be used, but copper or stainless steel is preferable.

The method for producing the negative electrode active material of the present invention includes:
The following method can be used, but the method is not limited thereto, and a known vacuum film forming method such as an evaporation method, an ion plating method, and a CVD method can be used. A preferable production method of the present invention is to use a disk-shaped target made of a target simple substance or a compound thereof from among the elements of the IIIB, IVB, and VB groups in an argon atmosphere of 1 × 10 ⁻² to 1 × 10 ⁻³ Torr. This is a method of forming a film on a substrate made of copper foil or stainless steel foil by high frequency (RF) sputtering. Further, heat treatment is performed under vacuum if necessary.

As the positive electrode material used as the positive electrode active material of the present invention, any conventionally known materials can be used.
ixCoO ₂ , LixNiO ₂ , MnO ₂ , LiMnO ₂ ,
_{LixMn 2 O 4, LixMn 2-} y O 4, α-V 2 O 5, Ti
S _2, and the like.

The non-aqueous electrolyte used in the present invention is a non-aqueous electrolyte in which a lithium compound is dissolved in an organic solvent, or a polymer in which a lithium compound is dissolved or an organic solvent in which a lithium compound is dissolved is held. A polymer solid electrolyte can be used. The non-aqueous electrolyte is prepared by appropriately combining an organic solvent and an electrolyte, and any of these organic solvents and electrolytes can be used as long as they are used for this type of battery. Examples of the organic solvent include propylene carbonate, ethylene carbonate, pinylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl ethyl carbonate,
1,2-dimethoxyethane, 1,2-diethoxyethanemethylformate, butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1-3 dioxofuran, 4-methyl-1,3-dioxofuran, diethyl ether, sulfolane, methylsulfolane, Acetonitrile, propionitrile, butyronitrile, valeronitrile, benzonitrile, 1,2-dichloroethane,
-Methyl-2-pentanone, 1,4-dioxane, anisole, diglyme, dimethylformamide, dimethylsulfoxide and the like. One of these solvents can be used alone, or two or more can be used in combination. As the electrolyte, for example, LiClO ₄ , LiA
_{sF 6, LiPF 6, LiBF4,} LiB (C 6 H 5) 4,
LiCl, LiBr, LiI, LiCH ₃ SO ₃ , LiC
F ₃ SO ₃ , LiAlCl _{4 and the} like can be mentioned. One of these can be used alone, or two or more can be used in combination.

The solid polymer electrolyte used in the present invention is:
An electrolyte selected from the above-mentioned electrolytes and dissolved in a polymer described below can be used. For example, a polymer having a polyether chain such as polyethylene oxide or polypropylene oxide, a polymer having a polyester chain such as polyethylene succinate, poly-caprolactam, a polymer having a polyamine chain such as polyethyleneimine, a polyalkylene sulfide And a polymer having a polysulfide chain. Further, as the polymer solid electrolyte used in the present invention, polyvinylidene fluoride, vinylidene fluoride-tetrafluoroethylene copolymer, polyethylene oxide, polyacrylonitrile, holding the non-aqueous electrolyte in a polymer such as polypropylene oxide What plasticized the said polymer can also be used.

[0012]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

Embodiment 1 FIG. 99.9 purity from Furuuchi Chemical
A thin film of silicon was formed on a copper substrate having a thickness of 0.1 mm and a purity of 99.9% by using an RF sputtering apparatus with a target of 9% silicon. During sputtering, the inside of the bell jar was set to an argon atmosphere of 1.7 × 10 ⁻³ Torr, and the film formation time was set to 45 minutes. Furthermore, 9.0 × 10 ^-6
The film was held at 650 ° C. for 1 hour under a Torr vacuum to perform an annealing treatment. Thus, a crystalline silicon thin film having a thickness of 2 μm was obtained and used as a negative electrode. The positive electrode was produced as follows. Lithium carbonate Li ₂ O ₃ and cobalt carbonate CoCO ₃ were weighed at an equimolar ratio and wet-mixed in a ball mill using isopropyl alcohol, then the solvent was evaporated and calcined at 800 ° C. for 1 hour. After re-crushing the calcined powder with a vibration mill, the molding pressure is 1.3 ton / cm ² and the diameter is 16 m.
m, after being pressed into a 0.5 mm thick pellet,
What was fired at 0 ° C. for 10 hours was used as a positive electrode. The electrolytic solution was prepared by mixing lithium hexafluorophosphate LiPF _{6 in} a mixed solvent of ethylene carbonate and dimethyl carbonate at a volume ratio of 1: 1.
Was dissolved at 1 mol / l. Negative electrode described above,
A coin battery was prepared using the positive electrode and the electrolyte, left standing at room temperature for 24 hours, aged, and then subjected to a charge / discharge test at a constant current of 1.5 mA in a potential range of 4.2 V to 2.5 V. Table 1 shows the results.

Comparative Example 1 A coin battery was manufactured in the same manner as in Example 1 except that a negative electrode was used in which graphite was used as a conductive aid and Teflon was used as a binder, and the resultant was coated on a copper substrate using silicon powder manufactured by Kojundo Chemical Laboratory Co., Ltd. Then, a charge / discharge test was performed. Table 1 shows the results.

[0015]

[Table 1]

[0016]

As described above, the present invention provides one or more members selected from Groups IIIB, IVB and VB of the periodic table for inserting and releasing lithium ions as a negative electrode active material of a non-aqueous secondary battery. A semiconductor thin film made of a simple substance of the element or a compound thereof, a metal oxide containing a transition metal as a constituent element as a positive electrode active material, an organic solvent lithium compound dissolved, or a lithium compound dissolved in a polymer or a lithium compound When a lithium ion conductive non-aqueous electrolyte holding an organic solvent in which is dissolved is used as an electrolyte, the charge / discharge characteristics at a higher capacity, a higher voltage and a higher current density than when a particulate negative electrode active material is used are improved. An excellent non-aqueous secondary battery can be obtained.

Claims (5)

[Claims] 1. A non-aqueous secondary battery having a positive electrode and a negative electrode, in which one or more elements selected from Group IIIB, IVB, and VB of the periodic table that inserts / releases lithium ions or a single element thereof. A negative electrode material for a non-aqueous secondary battery, wherein a semiconductor thin film made of a compound is used as a negative electrode active material. 2. The semiconductor thin film according to claim 1, wherein said semiconductor thin film is a group consisting of B, Al, Ga, In and Tl as Group IIIB elements of the periodic table;
A simple substance or a compound of one or more elements selected from the group consisting of C, Si, Ge, Sn and Pb as group VB elements and the group consisting of N, P, As, Sb and Bi as group VB elements The negative electrode material for a non-aqueous secondary battery according to claim 1, comprising: 3. A method for depositing a semiconductor thin film comprising a simple substance of one or more elements selected from the groups IIIB, IVB and VB of the periodic table or a compound thereof on a current collector substrate by an evaporation method, a sputtering method, A method for producing a negative electrode material for a non-aqueous secondary battery, wherein the method is produced by one of a plating method and a CVD method. 4. The method according to claim 1, wherein the semiconductor thin film formed on the current collector substrate by any one method selected from a vapor deposition method, a sputtering method, an ion plating method, and a CVD method is heat-treated under vacuum. The method for producing a negative electrode material for a non-aqueous secondary battery according to claim 3. 5. A metal oxide comprising, as a negative electrode active material, a semiconductor thin film made of one or more of one or more elements selected from Groups IIIB, IVB, and VB of the periodic table as a negative electrode active material, and a transition metal as a constituent element. The lithium ion conductive non-aqueous electrolyte in which a lithium compound is dissolved in an organic solvent, or a lithium compound is dissolved in a polymer or an organic solvent in which a lithium compound is dissolved is held as an electrolyte. A non-aqueous secondary battery characterized by being used.