JPS62176055A - Lithium battery - Google Patents

Abstract

PURPOSE:To make a battery compact, and to increase charge-discharge capacity and battery performance by using a binary system oxide to which TiO2 is added in an amorphous form as a positive active material. CONSTITUTION:A double oxide crystal or an amorphous material of a binary system oxide compising amorphous V2O5 and TiO2 and having (V2O5)x(TiO2)y (where, x+y=1, 0.1<=y<=0.5) is used as a positive active material 6. Lithium or lithium alloy is used as an active material of a negative electrode 4. A substance which is chemically stable to positive and negative active materials and allows a lithium ion to move to electrochemically react with the both active materials is used as an electrolyte material. Thereby, a battery is made compact, and charge-discharge capacity is increased, and battery performance is also made good.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention provides a lithium secondary battery that is small in size and has a large charge/discharge capacity, specifically, a lithium secondary battery that uses lithium as a negative electrode active material,
The present invention relates to a chargeable and dischargeable lithium battery using )x (Ti02)y as a positive electrode active material.

[Summary of the Disclosure] The present invention provides a binary oxide consisting of V2O5 and TiO2, the composition of which is (V20s) x (Ti02) y (where x+y
-1,0,1≦y≦0.5) is used as a positive electrode active material, lithium or a lithium alloy is used as a negative electrode active material, and chemically applied to the positive electrode active material and the negative electrode active material. By using a vine material as an electrolyte material, which is stable and allows lithium ions to move for an electrochemical reaction with the positive electrode active material or the negative electrode active material, it is a compact, high energy density material with little loss of charge/discharge capacity. The present invention discloses a technology that can be used in various fields such as coin-type batteries and can be used to construct lithium batteries.

Note that this summary is provided solely for the purpose of quickly accessing the technical content of the present invention, and does not have any influence on the technical scope of the present invention or the interpretation of rights.

[Prior Art] Many proposals have been made regarding high energy density batteries that use lithium as a negative electrode active material. For example, batteries are known that use graphite and a fluorine intercalation compound as a positive electrode active material, and a lithium alloy as a negative electrode active material (for example, see US Pat. No. 3,514,337). Furthermore, lithium batteries using fluorinated graphite as a positive electrode active material and lithium batteries using manganese dioxide as a positive electrode active material are already commercially available.

However, these batteries are primary batteries and have the disadvantage that they cannot be recharged.

Regarding secondary batteries using lithium as a negative electrode active material, batteries using titanium, hafnium, niobium, tantalum, vanadium sulfides, selenides, and tellurides as positive electrode active materials (for example, U.S. Pat. No. 4,009,
052 specification), or batteries using chromium oxide, niobium selenide, etc. (J, Electroche
m, Soc,, 124(7), 968 and 325,
(1977)), but these batteries could not necessarily be said to have sufficient battery characteristics and economical efficiency.

In addition, for lithium batteries using amorphous materials as positive electrode active materials, in the case of MoS2, Mo53, and v2s5 (
J,Electroanal,chem,, 118,
229 (1981)) and LiV30B (J, N
on-Crystalline 5olids, 44°297 (1981)), etc. have been proposed.

However, both proposals had problems in terms of discharge at high current density and charge/discharge characteristics.

Using crystalline P2O5 as a positive electrode active material
J, Electrochem, Soc, Meet
ing, Toronto, Mayll-16, 1975
, No., 27). Also, P2O5 and P2
An amorphous material obtained by adding O5 and rapidly cooling after melting is proposed in Japanese Patent Application No. 59-237778.

However, in either case, the capacity was small and the charge/discharge characteristics were not sufficient.

[Problems to be Solved by the Invention] Therefore, an object of the present invention is to improve the above-mentioned current problems and provide a lithium battery that is small, has a large charge/discharge capacity, and has excellent battery characteristics. .

[Means for Solving the Problems] In order to achieve the above object, the lithium battery of the present invention uses (V2O5)X(TiO2)y as a positive electrode active material.
Use.

In the present invention, it was confirmed that by using a binary oxide in which TiO2 is added to P2O5 as a positive electrode active material, a lithium battery with higher charge/discharge capacity and excellent cycleability than conventional lithium batteries can be constructed. The present invention was completed based on this understanding.

That is, the present invention provides a binary oxide consisting of P2O5 and TiO2, whose composition has the general formula (P2O5
)X (Tt02 )y (where x*y -1,0,1≦y≦0.5) is used as the positive electrode active material, and lithium or lithium alloy is used as the negative electrode active material. chemically stable with respect to the positive electrode active material and negative electrode active material,
The present invention is characterized in that the electrolyte material is a substance that allows lithium ions to move for electrochemical reaction with the positive electrode active material or the negative electrode active material.

In order to form a positive electrode using this positive electrode active material, this mixed material powder or a mixture of this mixed material powder and a binder powder such as polytetrafluoroethylene is pressure-molded onto a support such as nickel or stainless steel.

Alternatively, a conductive powder such as acetylene black is mixed in order to impart conductivity to the mixed material powder, and a binder powder such as polytetrafluoroethylene is further added as required, and this mixture is mixed with a conductive powder such as acetylene black to impart conductivity. Put it in a container,
Alternatively, the positive electrode can be formed by pressure-molding the above-mentioned mixture onto a support such as nickel or stainless steel.

Lithium or a lithium alloy is used as the negative electrode active material. Such lithium or lithium alloy can be formed into a negative electrode by being spread into a sheet or by pressing the sheet onto a conductive net made of nickel, stainless steel, etc., as in the case of general lithium.

Further, as the electrolyte, a substance is used that is chemically stable with respect to the positive electrode active material and the negative electrode active material, and is capable of moving lithium ions for electrochemical reaction with the positive electrode active material. For example, propylene carbonate, 2-
Methyltetrahydrofuran, dioxolene, tetrahydrofuran, 1,2-dimethoxyethane, ethylene carbonate, γ-butyrolactone, dimethyl sulfoxide,
LiCIL04, Li/1CA4 and one or more aprotic organic solvents such as acetonitrile, formamide, dimethylformamide, nitromethane, etc.

LiBF4, LICi! ,, LiPF6, LiA
Known electrolytes generally used in batteries using lithium as a negative electrode active material, such as a combination with a lithium salt such as sF6, or a solid electrolyte or molten salt using lithium ions as a conductor, can be used as the electrolyte in the present invention. I can do it.

Further, when a microporous separator is used as required in the battery configuration, a thin film made of porous polypropylene or the like may be used.

The above-mentioned amorphous material as a positive electrode active material has a composition formula of (V205) Those that have been treated are preferred. The firing temperature is in the range of 600°C to 680°C, and TiO2
The price will be higher for systems with a large amount of additives. Furthermore, as will be described later in the Examples section, an amorphous material obtained by subjecting this mixed oxide to melt diameter quenching also exhibits good battery characteristics. However, it is difficult for a positive electrode active material having a composition outside this range to exhibit excellent characteristics.

[Function] According to the present invention, it is possible to construct a small, high energy density lithium battery with little loss of charge/discharge capacity, and the battery of the present invention can be used in various fields such as coin-type batteries.

[Examples] The present invention will be explained in detail by examples below with reference to the drawings.

Note that the present invention is not limited only to the following examples. In the following examples, all cell preparations and measurements were performed under an argon cloud.

Example 1 FIG. 1 is a sectional view of a coin-type battery that is a specific example of a lithium battery according to the present invention. In the figure, 1 is a stainless steel sealing plate, 2 is a polypropylene gasket, 3 is a stainless steel positive electrode case, 4 is a lithium negative electrode, 5 is a polypropylene separator, and 6 is a positive electrode mixture pellet.

First, a metal lithium negative electrode 4 placed under pressure on a sealing plate l is inserted into the recess of the gasket 2, and the separator 5 and positive electrode mixture pellets are placed on the lithium negative electrode 4 at the opening of the sealing plate 1. 6 in this order, and after injecting and impregnating an appropriate amount of 1.5 N -LiAsF6/2-methyltetrahydrofuran (2Me THF) as an electrolyte, cover the positive electrode case 3 and swage it to a diameter of 23 mm. , a coin-type battery with a thickness of 2+nm was created.

The positive electrode active material is prepared by: (1) mixing 205 and T i 02 so that the mol% of TiO2 is in the range of 10% to 50%;
Baked in the air at a temperature of 600 to 680°C for 24 hours,
Alternatively, after adding 30 mol % or less of P2O5, the melt diameter quenching treatment was performed at about 800° C. to obtain the above-mentioned crystalline and amorphous positive electrode active materials, respectively.

The prepared positive electrode active material was pulverized for about 70 minutes using a mixing pulverizer, and then mixed with acetylene black 8B and tetraph J rheoloethylene in a weight ratio of 70:25:5.
mixed in the ratio of The mixture is roll-formed to a thickness of 0.
．． A 6 mm diameter piece was punched out to obtain a positive electrode mixture pellet 6.

Using the lithium battery created as described above, 0.
The results of constant current discharge at a current density of 5 mA/cm2 were used as positive electrode active materials for various compositions of v2o5 )x (
Ti02)y (however, x+y =1, 0.1≦y
Table 1 shows the case of a crystalline material and an amorphous material of a double oxide given by ≦0.5).

Table 1 Discharge capacity at 0,5mA/Cm2 (2V end) Unit: ^h 7kg Also, from Table 1, as a representative example, (V2 O5
)o, 7r(T i 02 1o, 2) FIG. 2 shows a discharge curve when crystalline and amorphous materials of the double oxide of (T i 02 1o, 2) are used as the positive electrode active material.

Example 26 Using a lithium battery prepared in the same manner as Example 1,
A voltage regulated charge/discharge test between 2v and 3.5o was conducted at a constant current density of 0.5m^/cm2. The discharge capacity at the fifth cycle is shown in Table 2 for various crystalline and amorphous materials.

Table 2 Discharge capacity (2V final) in cm2 to 0.5m8 Unit: Ah 7kg Also, as a representative example from Table 2, ("205
) (+, 74; (T i 02 ), , 117) The cycle characteristics when crystalline and amorphous materials are used as positive electrode active materials are shown in FIG.

As shown in Table 1, crystalline materials are better in terms of simple discharge capacity, but amorphous materials are better in terms of cycleability. In particular, for both the crystalline material and the amorphous material, the Ti02 mo1 fraction is 0.25 mo1%.
It can be seen that the overvoltage is low and the best cycle characteristics are exhibited in the case of .

[Effects of the Invention] As explained above, according to the present invention, it is possible to construct a small, high energy density lithium battery with little loss in charge/discharge capacity, and the battery of the present invention can be used in various fields such as coin-type batteries. It has the advantage that it can be used for

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a configuration example of a coin-type battery according to an embodiment of the present invention, FIG. 2 is a characteristic diagram showing the discharge characteristics of a battery according to an embodiment of the present invention, and FIG. FIG. 2 is a characteristic diagram showing the charging and discharging characteristics of a battery in one example. DESCRIPTION OF SYMBOLS 1... Stainless steel sealing plate, 2... Polypropylene gasket, 3... Stainless steel positive electrode case, 4... Lithium negative electrode, 5... Polypropylene separator, 6... Positive electrode mixture pellet.

Claims (1)

[Claims] A binary oxide consisting of V_2O_5 and TiO_2, the composition of which is given by (V_2O_5)x(TiO_2)y (where x+y=1, 0.1≦y≦0.5). The positive electrode active material is a double oxide material, and the negative electrode active material is lithium or lithium alloy, which is chemically stable with respect to the positive electrode active material and the negative electrode active material, and lithium ions are A lithium battery characterized in that an electrolyte material is a substance that can move to perform an electrochemical reaction with a negative electrode active material.