JPH11135120A - Negative electrode material for nonaqueous secondary battery - 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, and superior charging/ discharging characteristics, and to provide its manufacturing method. SOLUTION: Composite particles formed by covering at least one single element or its compound selected from among groups IIIB, IVB, and VB in the periodic table, inserting/releasing lithium ions with conductive carbon are used as the negative active material of a negative electrode, a metal oxide containing a transition metal 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 combining at the same time the positive electrode with negative electrode and electrolyte, a nonaqueous electrolyte secondary battery having high voltage, high capacity, and superior charging/discharging 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 that the charge / discharge capacity per volume is low.

As negative electrode active materials which can be expected to have a high charge / discharge capacity per volume, 1) transition metal chalcogen compounds such as TiS ₂ and LiTiS ₂ (US Pat. No. 3,983,476);
2) a transition metal oxide having a rutile structure, for example, WO ₂ (U.S. Pat. No. 4,198,476); 3) LixFe (F
e ₂₎ spinels such as O ₄ (JP 58-2203
No. 62), 4) Lithium compound of Fe ₂ O ₃ electrochemically synthesized (US Pat. No. 4,446,447), Fe ₂ O ₃
Lithium compound (JP-A-3-112070), Nb
₂ O ₅ (JP-A-62-59412, JP-A-2-8244)
No. 7), iron _{oxide, FeO, Fe 2 O 3,} Fe 3 O 4, cobalt _{oxide, CoO, Co 2 O 3,} Co 3 O 4 ( JP-A-3-29
No. 1862). On the other hand, 5) Sn, Cd (Proceedings of the) which are known to form an alloy with lithium.
Electrochemical Society, 8
7-1, 1987) Al (Solid State I)
onics, 20, 1986), Si, Pb, Bi, S
b (Proceedings of the Elec
Trochemical Society, 87-1,
1987) and alloys thereof with lithium (for example, JP-A-7-29602).

[0004]

However, the above-mentioned Sn, Cd, Al, Si, Pb, Bi, Sb and their alloys with lithium have particularly high current densities (for example, 1 m
(A / cm ² or more), there is a problem that the capacity is low and the cycle life during charge / discharge is short. In addition, 1) to above
The electrode potential of the negative electrode active material of 5) is noble with respect to the electrode potential of metallic lithium. Therefore, when a negative electrode active material is used as a negative electrode in combination with a positive electrode to form a battery, the operating voltage of the negative electrode active material is lithium metal. There is a problem that it is lower than in the case of using. Therefore, the object of the present invention is to
1) a negative electrode active material capable of reversibly inserting and releasing lithium ions and providing a high capacity; 2) a method for producing the negative electrode active material; and 3) a charge / discharge at a high current density of 3 to 10%. An object of the present invention is to provide a non-aqueous secondary battery having a high voltage of 4 V, a high capacity, good charge / discharge characteristics and cycle life.

[0005]

In order to achieve the first object, the negative electrode active material of the present invention comprises at least one or more periodic table I which inserts / releases lithium ions.
It is a composite particle composed of a simple substance of an element (except for Si) selected from the IIB, IVB, and VB groups or a compound thereof and a carbonaceous material. Here, the composite particles are particles obtained by coating a simple substance of the above element or a compound thereof with a carbonaceous material. The composite particles further include a conductive metal. A second object is to prepare a composite material, which is a dispersion mixture of a simple substance of the above element or a compound thereof and a resin material capable of being carbonized by heat treatment, in a non-oxidizing atmosphere.
This is achieved by a method of producing composite particles coated with a carbonaceous material by heat-treating at 00 to 1200 ° C and pulverizing mechanically. Further, a third object is to use the composite particles 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, a lithium compound dissolved in an organic solvent, or a lithium compound in a polymer. This is achieved by forming a battery using a lithium ion conductive non-aqueous electrolyte holding an organic solvent in which a solid solution or a lithium compound is dissolved as an electrolyte. The composite with conductive carbon improves the conductivity of the negative electrode active material, further facilitates the insertion and release of lithium ions, and has the effect of improving the active material utilization rate and decreasing the internal resistance of the battery. As a result, a non-aqueous electrolyte secondary battery having high voltage, high capacity and excellent cycle characteristics can be obtained.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
In the present invention, B, Al, Ga, I of Group IIIB of the periodic table are used.
a group consisting of n and Ti, Ge, Sn and Pb of the IVB group
Or one or more simple substances or compounds thereof selected from the group consisting of As, Sb and Bi of the VB group. A simple substance is preferably Bi, Al, or Sn. The compound may be any compound as long as it can insert and release lithium ions. InBi, Bi ₃ In ₅ , BiIn ₂ ,
InSb, InAs, InP, InN, GaSb, Ga
_{As, GaP, GaN, Tl 5} Sb, Sb 5 Tl 7, Bi 2
Compound semiconductors such as Tl and AlSb are exemplified.

The conductive metal used in the present invention is C
Noble metals such as u, Au and Ag, and transition metals such as Fe, Co and Ni.

[0008] The resin material of the present invention is not particularly limited as long as it is carbonized by heat treatment and the carbonized material has conductivity. Specific examples include phenol resin and epoxy resin. Resin, unsaturated polyester resin, furan resin, urea resin, melamine resin, alkyd resin, thermosetting resin such as alkyne resin or xylene resin And condensed polycyclic hydrocarbon compounds such as naphthacene, picene, perylene, pentaphene and pentaene, derivatives thereof, and pitches mainly containing a mixture thereof.

When the carbonaceous material is the main component, the capacity is reduced. On the other hand, when the content is too small, sufficient conductivity cannot be obtained. Therefore, the content of the above-mentioned element alone or in the composite particles of the compound is 20% by weight or more. And more preferably 40% by weight or more and 95% by weight or less.

The method for producing the negative electrode active material of the present invention includes:
The following method is exemplified, but not limited thereto. IIIB, IVB, VB group elements (excluding Si)
One or more of powders of a simple substance or a compound selected from the above are dispersed in a carbonizable resin material by heat treatment,
The mixture is mixed to prepare a composite material of a powder of the element alone or a compound thereof and the resin material. It is desirable to use a powder having an average particle diameter of 1 to 30 μm as a powder of the above element alone or a compound thereof. The composite material is fired in a non-oxidizing atmosphere, preferably in a nitrogen or argon gas.
If the temperature is lower than 400 ° C., the carbonization is insufficient. If the temperature exceeds 1200 ° C., carbides of the added simple substance or the compound thereof which do not participate in charge / discharge are generated, so that the capacity decreases in any case. Therefore, the firing temperature is desirably 400 ° C to 1200 ° C. Further, the heat treatment time is desirably 0.1 hours or more. After firing, the material is finely pulverized mechanically using a vibration mill or the like. A binder is added to the composite particles thus produced, kneaded and applied to a stainless steel mesh to form a negative electrode.

Further, composite particles containing a noble metal such as Cu, Au and Ag and a transition metal such as Fe, Co and Ni as a conductive metal for imparting conductivity can be produced by any of the following methods. That is, 1) at least one kind selected from the conductive metal powders is added to the carbonizable resin material and then calcined, or 2) a composite particle composed of a simple substance of the element or a compound thereof and a carbonaceous material. A binder is added and kneaded, applied on the conductive metal foil, and heat-treated at a predetermined temperature in a non-oxidizing atmosphere. In the method 2), the conductive metal on the surface of the conductive metal foil is diffused into the composite particles by the heat treatment, so that composite particles containing the conductive metal can be newly produced. The amount of the conductive metal in the composite particles is desirably 5% by weight or more and 60% by weight or less in total with the carbonaceous material.

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 solid solution of a lithium compound in a polymer 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,
4-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 , Li
AsF ₆ , LiPF ₆ , LiBF ₄ , 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 comprises:
A solution obtained by dissolving an electrolyte selected from the above electrolytes in the following polymer 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. Also,
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 Plasticized molecules can also be used.

[0015]

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. Bismuth powder and a phenol resin were mixed under equal weight and stirred, and cured at 80 ° C. for 3 days. The phenolic resin used here was prepared by mixing 150 parts of cresol (m-cresol content 38%) with 135 parts of a 30% aqueous formaldehyde solution and 7.5 parts of 25% aqueous ammonia to obtain a mixture of 8 parts.
After heating at 5 ° C. for 105 minutes, water was removed by distillation under reduced pressure. The obtained bismuth-containing phenolic resin cured product was 11
After baking at 00 ° C. for 3 hours and dry pulverization, bismuth-carbon composite particles applied to a 20 mm × 15 mm SUS mesh were used as a negative electrode with Teflon as a binder.
The positive electrode was produced as follows. Lithium carbonate Li ₂ CO ₃
And cobalt carbonate CoCO _{3 and the} like are weighed in a molar ratio and wet-mixed in a ball mill using isopropyl alcohol, and then the solvent is evaporated and calcined at 800 ° C. for 1 hour. After re-crushing the calcined powder with a vibration mill, the molding pressure is 1.3t.
After being pressed into a pellet having a diameter of 16 mm and a thickness of 0.5 mm at on / cm ² , the pellet was fired at 800 ° C. for 10 hours to obtain a positive electrode. The electrolyte used was a solution in which lithium hexafluorophosphate LiPF ₆ was dissolved at 1 mol / l in a mixed solvent of ethylene carbonate and dimethyl carbonate at a volume ratio of 1: 1. After aging the coin battery thus manufactured at room temperature for a day and a night, a constant current of 1.5 mA
A constant current charge / discharge test was performed in the range of 4.2 V to 2.5 V. Table 1 shows the results. The discharge potential was 3.1 V and a constant potential was obtained, and it was found that the bismuth-carbon composite particles had characteristics suitable as a negative electrode active material.

Embodiment 2 FIG. As in Example 1, aluminum powder and phenol resin were mixed by equal weight and stirred.
Cured for days. The cured aluminum-containing phenolic resin was baked at 1100 ° C. for 3 hours, and after dry pulverization, Teflon was used as a binder, and aluminum-carbon composite particles applied to a SUS mesh were used as electrodes. Using the positive electrode shown in Example 1, a coin battery was assembled, and charge / discharge evaluation was performed at a constant current of 1.5 mA. The discharge potential was constant at 3.4 V, and it was found that the aluminum-carbon composite particles had characteristics suitable as a negative electrode active material.

Embodiment 3 FIG. In the same manner as in Example 1, tin powder and phenol resin were mixed and stirred at an equal weight, and cured at 80 ° C. for 3 days. The cured tin-containing phenolic resin was baked at 1100 ° C. for 3 hours, and after dry pulverization, tin-carbon composite particles coated on a SUS mesh were used as electrodes, using Teflon as a binder. Using the positive electrode shown in Example 1, a coin battery was assembled, and charge / discharge evaluation was performed at a constant current of 1.5 mA. The average potential at the time of discharge was 3.2 V, which was constant, indicating that the tin-carbon composite particles had characteristics suitable as a negative electrode active material.

Comparative Example 1 The phenol resin itself used in Example 1 was cured at 80 ° C. for 3 days. The carbon obtained by calcining the cured phenolic resin at 1100 ° C. for 3 hours is subjected to dry pulverization, and then Teflon is used as a binder.
A negative electrode was formed by applying the coating to a mesh. Similarly to the bismuth-carbon composite particles, a coin battery was assembled using the positive electrode shown in Example 1, and charge / discharge evaluation was performed at a constant current of 1.5 mA.
At this time, the obtained discharge capacity was as low as 3 to 4 mAh, and unlike the case where bismuth-carbon composite particles were used, the charge / discharge characteristics at a constant potential were not exhibited.

Comparative Example 2 Graphite powder was applied to a SUS mesh using Teflon as a binder in the same manner as in Comparative Example 1 to obtain a negative electrode. Using the positive electrode shown in Example 1, a coin battery was assembled, and charge / discharge evaluation was performed at a constant current of 1.5 mA.

[0021]

Table 1 Discharge capacity (mAh) Example 1 72 Example 2 21 Example 3 33 Comparative example 1 4 Comparative example 2 12

[0022]

As described above, the present invention relates to a nonaqueous secondary battery using a lithium-conductive nonaqueous electrolyte, and a periodic table IIIB, IVB, VB, VB which inserts / releases lithium ions at least as a negative electrode active material. One or two or more selected from the group consisting of a single particle or a compound thereof and conductive carbon, a metal oxide containing a transition metal as a constituent element as a positive electrode active material, and a lithium compound dissolved in an organic solvent as an electrolyte. High voltage, high capacity and good charge / discharge cycle characteristics by using a lithium ion conductive non-aqueous electrolyte in which a lithium compound is dissolved in a polymer or an organic solvent in which a lithium compound is dissolved is retained. Is obtained.

Claims (7)

[Claims] 1. A non-aqueous secondary battery having a positive electrode and a negative electrode, wherein at least one or more of the periodic tables IIIB and IV in which at least the negative electrode active material inserts and releases lithium ions
A negative electrode material for a non-aqueous secondary battery, wherein the negative electrode material is a composite particle composed of a simple substance or a compound of an element (excluding Si) selected from a group B or VB and a carbonaceous material. 2. A compound represented by the formula B:
One or two selected from the group consisting of Al, Ga, In and Tl, the group consisting of Ge, Sn and Pb as Group IVB elements, and the group consisting of As, Sb and Bi as Group VB elements
The negative electrode material for a non-aqueous secondary battery according to claim 1, wherein a simple substance or a compound of at least one element is used. 3. A composite particle comprising a simple substance of said element or a compound thereof in an amount of 20 to 95% by weight.
Negative electrode material for non-aqueous secondary battery described 4. The negative electrode material for a non-aqueous secondary battery according to claim 1, wherein the composite particles further include a conductive metal imparting conductivity. 5. A dispersion mixture of a simple substance of one or more elements (excluding Si) selected from the groups IIIB, IVB and VB of the periodic table (excluding Si) or a compound powder thereof and a resin material carbonizable by heat treatment. A composite material comprising a simple substance of the above element or a compound thereof and a carbonaceous material by heat-treating the composite material at 400 to 1200 ° C. in a non-oxidizing atmosphere and mechanically pulverizing the composite material. A method for producing a negative electrode material for a secondary battery. 6. The composite material according to claim 4, wherein a powder having an average particle diameter of 1 to 30 μm is used as a simple substance or a compound powder of an element dispersed and mixed with the resin material capable of being carbonized by heat treatment. Method for producing a negative electrode material for a non-aqueous secondary battery. 7. At least periodic table IIIB, IVB,
A metal oxide containing, as a negative electrode active material, a single particle of one or more elements (excluding Si) selected from the VB group or a compound thereof and a carbonaceous material, and a transition metal as a constituent element Using a lithium ion conductive non-aqueous electrolyte in which a lithium compound is dissolved in an organic solvent, or in which a lithium compound is dissolved in a polymer or an organic solvent in which a lithium compound is dissolved is held as a positive electrode active material, as an electrolyte Non-aqueous secondary battery characterized by the following.