JPS63121258A - Nonaqueous secondary battery - Google Patents

Abstract

PURPOSE:To improve the cycling characteristic end overvoltage characteristic by using a specific compound oxide having a layer structure as a positive electrode. CONSTITUTION:A compound oxide having a layer structure and shown by Formula I is used as a positive electrode, where A is one type selected among alkaline metals; B is a transition metal; C is one type selected among a group of Al, In, and Sn; D indicates at least one type selected among a group of alkaline metals other than (a) A, transition metals other than (b) B, and second- sixth period elements of IIIb group, IVb group, Vb group, VIb group except (c) IIa group elements, (d) Al, In, Sn, carbon, nitrogen, and oxygen; and (x), (y), (z), and (w) indicate 0.05<=x<=1.10, 0.85<=y<=1.00, 0.001<=z<=0.10, 0.001<=w<=0.10 respectively. Thereby, the cycling characteristic and self-discharge characteristic are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a novel secondary battery, and more particularly to a small and lightweight secondary battery.

[Conventional technology] In recent years, electronic devices have become smaller and lighter at a remarkable rate, and as a result, there has been a great demand for smaller and lighter batteries that serve as power sources. Although small and lightweight batteries such as lithium batteries have been put into practical use, since these are secondary batteries, they cannot be used repeatedly, and their fields of application are limited. On the other hand, in the field of secondary batteries, lead batteries and nickel-cadmium batteries have conventionally been used, but both have major problems in terms of miniaturization and weight reduction.

From this point of view, non-aqueous secondary batteries have been attracting a lot of attention, but they have not yet been put into practical use.One of the reasons for this is that the positive electrode active material used in these secondary batteries has poor cycleability, self-discharge characteristics, etc. The problem is that no material has been found that satisfies practical physical properties.

On the other hand, a new group of cathode active materials that utilize the interreaction reaction of layered compounds, which has a fundamentally different reaction type from conventional nickel-cadmium batteries, lead-acid batteries, etc., are attracting attention.

Such new positive electrode active materials are expected to have extremely excellent charge-discharge cycle performance because they do not cause complex chemical reactions during electrochemical reactions during charging and discharging.

For example, chalcogenide compounds with a layered structure are attracting attention as an example of utilizing intercalation of layered compounds.For example, chalcogenide compounds such as Li, TiS2, LixMoS3, etc. have relatively excellent cyclability. Even when Li metal, which has a low electromotive force, is used for the negative electrode, the practical discharge voltage is around 2V at most, which is not satisfactory in terms of high electromotive force, which is one of the characteristics of non-aqueous batteries. On the other hand, LixV2O5, LixV60+s, Lix, which also have a layered structure
Metal oxide compounds such as V2O5 and Lixmi02 are attracting attention because of their high electromotive force. However, these metal oxide compounds have inferior performance in terms of cycleability, utilization rate, that is, the ratio that can actually be used for charging and discharging, and further overvoltage during charging and discharging, and have not yet been put into practical use.

In particular, the L disclosed in JP-A No. 55-138131
The positive electrode of secondary batteries such as ixCo02, Li, and old 02 is L.
When i-metal is used as a negative electrode, it has an electromotive force of 4V or more, and the theoretical energy density (per positive electrode active material) is 1
．． Despite having an amazing value of over 100WHr/kg, the proportion that can actually be used for charging and discharging is low.
The energy density obtained is far from the theoretical value.

[Problems to be Solved by the Invention] The present invention solves the problems of the metal oxide positive electrode described above, and provides a novel non-aqueous secondary battery that has excellent battery performance, particularly cycleability, utilization rate, and overvoltage characteristics. This was done to provide a positive electrode for next-generation batteries.

According to the present invention, it has a 1M layered structure and has the general formula % [where A is at least one selected from alkali metals, B is a transition metal, and C is AI! , In.

is at least one species selected from the group of Sn, and D is (a
) Alkali metal other than A, (b) Transition metal other than B, (c) Ila group element, (d) Al, In, S
n, excluding carbon, nitrogen, and oxygen <mb group, ■ b group, vb group,
Represents at least one element selected from the group of elements of the 2nd to 6th period of the VIB group, and X * V + Z + '' are each 0.05≦X≦1.10, 0.85≦y≦1 ．．
00゜0.001≦2≦0.10, 0.001≦W≦Q
, 10, ] A non-aqueous secondary battery is provided that uses a composite oxide represented by the following as a positive electrode.

The novel layered composite metal oxide of the present invention has the general formula AxBvC
zDw02, where A is at least one selected from alkali metals, such as Li, Ha,
K, of which Li is preferable, the value of X is the state of charge,
It varies depending on the discharge state, and the range is 0.05≦X≦1.
It is lO. That is, deintercalation of A@ ions occurs due to charging, and the value of X decreases, and in a fully charged state, the value of X reaches 0.05. In addition, intercalation of A@ ions occurs due to discharge, and the value of X increases, and in a fully discharged state, the value of X becomes 1.
Reach 10.

Further, B represents a transition metal, and among them, Xi and Co are preferable.The value of y does not change due to charging and discharging, but 0.
The range is 85≦y≦1.00. In this case, B contains two or more types of transition metals, and the total X value is 0.
85≦X≦1. This includes cases that do not deviate from the scope of OO. If the value of y is less than 0.85 or more than 1.00, the performance as an active material for a secondary battery is not sufficient, that is, phenomena such as a decrease in cycleability and an increase in overvoltage occur, which is not preferable.

C is at least one selected from the group of Al, In, and Sn, with Sn being preferred; in this case, C is
The novel secondary battery use of the present invention includes two or more of Al, In, and Sn, and includes cases where the total X value does not deviate from the range of 0.001≦2≦0.10. In materials, the function of C is extremely important, and it exhibits extremely excellent cyclability, especially in deep charging and deep discharging cycles. The value of 2 does not vary with charging and discharging, but is in the range of 0.001≦2≦1.10, preferably in the range of 0.005≦2≦0.075. If the value of 2 is less than 0.001, the effect of C will not be sufficiently exhibited, the cycleability in deep charging and deep discharging as described above will be low, and the overvoltage will increase significantly during deep charging, which is undesirable. The value is 0. If it exceeds 1O, the hygroscopicity becomes too strong, making it difficult to handle, and the basic characteristics as a positive electrode for a secondary battery are impaired, which is not preferable.

D is (a) an alkali metal other than A, (b) a transition metal other than B, (c) a group IIa element, (d) Aj', I
Excluding n, Sn, carbon, nitrogen, and oxygen <MB group, IVb group, Vb group.

Represents at least one element selected from the group of elements of the 2nd to 6th period of the vIb group, and the value of W does not change due to charging and discharging, but is in the range o, oot≦W≦0.10, preferably 0. The range is .001≦W≦0.005. in this case,
D includes cases where two or more of the above element groups are included and the total W value does not deviate from the above range. W
If the value of is less than 0.001.

The effect of D is not sufficiently exhibited, the cycleability during deep charging and deep discharging described above is low, and the overvoltage during deep charging increases, which is undesirable.

The value of W is 0. If it exceeds 1O, the effect of the above-mentioned C element will be inhibited, and the basic performance as a positive electrode for a secondary battery will be impaired, which is undesirable. After mixing the oxides, hydroxides, carbonates, nitrates, organic acid salts, etc. of metals A, B, C, and D, the mixture is heated at eoo°C to 850°C in air or under an oxygen atmosphere.
, preferably by firing at a temperature range of 700°C to 900°C.

The firing time is usually about 5 to 48 hours.

AxByCzDw02 obtained by this method has a discharge state as a secondary battery positive electrode, that is, the value of X is usually 0.9.
A value in the range of 0-1.10 is obtained.

The value of
Varies within the range of X≦1.10.

The reaction is represented by the following formula. (Here, !' represents the value of X before charging, and X'' represents the value of X after charging.) The above-mentioned utilization rate is a value defined by the following formula.

The novel active material for nonaqueous secondary batteries of the present invention is characterized by a high utilization rate, that is, it has extremely stable cyclability against deep charging and discharging.

The novel composite oxide for secondary battery positive electrodes of the present invention has a very negative potential of 3.9 to 4.5V compared to Li standard potential, especially when used as a positive electrode of non-aqueous secondary batteries. Demonstrates particularly excellent performance.

Next, a secondary battery using the positive electrode of the present invention will be described. When manufacturing an electrode using the positive electrode for secondary batteries of the present invention,
The positive electrode can be used in various shapes.

That is, it can be used in any form such as film, fam, powder, etc. depending on the purpose, but especially when used in powder form,
The active material can be formed into any shape such as a sheet and used.

A common method for molding is to mix the active material with a powdered binder such as Teflon powder or polyethylene powder, and then compression mold the mixture.

A more preferable method is to form an electrode active material using an organic polymer dissolved and/or dispersed in a solvent as a binder.

Although non-aqueous batteries have conventionally been superior in terms of performance such as high energy density, small size and light weight, they have disadvantages in output characteristics compared to aqueous batteries, and have not yet been widely used, especially for secondary batteries that require high output characteristics. In the field of batteries, this drawback is one of the factors preventing practical application.

The reason why non-aqueous batteries have inferior output characteristics is that aqueous electrolytes have high ionic conductivity, usually 1o-1Ω-I Cl11-1
For non-aqueous systems it usually has a value of the order of 10
This is due to the fact that it does not have a low ionic conductivity of -2 to 10-4Ω-I C11-1.

One possible way to solve this problem is to increase the area of the electrode, that is, to use a thin film or a large-area electrode.

The above method is a particularly preferred method for obtaining such a g-film and large-sided end electrode.

When using such an organic polymer as a binder, there is a method in which an electrode active material is dispersed in a binder solution in which the organic polymer is dissolved in a solvent and used as a coating liquid, or a water emulsion dispersion of the organic polymer is used. Examples include a method in which a liquid in which an electrode active material is dispersed is used as a coating liquid, and a method in which a solution and/or dispersion of the organic polymer is applied to a preformed electrode active material. The amount of binder used is not particularly limited, but is usually in the range of 0.1 to 20 parts by weight, preferably 0.5 to 10 parts by weight, based on 100 parts by weight of the electrode active material.

The organic polymer used here is not particularly limited, but when the organic polymer has a specific electrical constant of 4.5 or more at 25° C. and a frequency of 1 KHz, particularly favorable results can be obtained. In particular, it has excellent battery performance in terms of cycleability, overvoltage, etc.

Examples of organic polymers that meet these conditions include polymers or copolymers of acrylonitrile, methacrinitrile, vinyl fluoride, vinylidene fluoride, chloroprene, vinylidene chloride, nitrocellulose, cyanoethylcellulose, polysulfide rubber, etc. Can be mentioned.

When manufacturing an electrode using this method, the coating solution is applied onto a base material and dried to form the electrode. At this time, if necessary, it may be molded together with the current collector material, or alternatively, a current collector such as aluminum foil or copper foil may be used as the base material.

The binder, conductive aid, and other additives such as thickeners, dispersants, fillers, adhesion aids, etc. may be added to the battery electrode manufactured using the active material of the present invention. It refers to a material containing at least 25% by weight or more of the active material of the present invention.

Examples of the conductive aid include metal powder, conductive metal oxide powder, and carbon. Particularly, when AXBVCZD1102 of the present invention is used, the addition of such a conductive auxiliary agent has a remarkable effect.

Among them, carbon gives preferable results, and is usually used in an amount of 1 to 3 parts by weight of AXB, CZDw02 1'OO.
Addition of 0 parts by weight produces a significant overvoltage reduction effect and exhibits excellent cycle characteristics.

The term carbon here does not necessarily mean specific carbon.

Examples of such carbon include graphite and carbon black. A particularly preferable combination is carbon with an average particle size of 0.1 to 10IL and an average particle size of 0.01p.
~0.08! Particularly excellent effects are obtained when carbon is used in combination.

The negative electrode is not particularly limited, but may include a light metal such as Li or Na or an alloy thereof, LixFe203. Lix
Fe:+Oa.

Metal oxide negative electrodes such as L 1XWO2, conductive polymer negative electrodes such as polyacetylene and poly-p-phenylene, carbonaceous material negative electrodes such as vapor grown carbon fibers, pitch carbon, polyacrylonitrile carbon TA fibers, etc. Can be mentioned.

As basic components when assembling the non-aqueous secondary battery of the present invention, an electrode using the positive electrode and the negative electrode of the present invention;
Further examples include separators and non-aqueous electrolytes. The separator is not particularly limited, but includes woven fabrics, non-woven fabrics, glass woven fabrics, synthetic resin microporous membranes, etc. As mentioned above, when using thin films and large-area electrodes, for example, A synthetic resin microporous membrane disclosed in No.
In particular, polyolefin microporous membranes are preferred in terms of thickness, strength, and membrane resistance.

The electrolyte of the non-aqueous electrolyte is not particularly limited, but examples include Li(1'Oa, LiBFn, LiAs
F6゜CF3SO3Li, LiPF6. LiI,
LiAjiCj? 4. NaC1)04°NaBFa,
Mal, (niu)aNLBci)On, (n-
Bu)aN”BFa.

Examples include KPF6. In addition, examples of organic solvents used in the electrolytic solution include ethers, ketones, lactones, nitriles, amines, amides, sulfur compounds, chlorinated hydrocarbons, esters, carbonates, nitro compounds, and phosphorus. Acid ester compounds, sulfolane compounds, etc. can be used, and among these, aircils, ketones, nitriles, chlorinated hydrocarbons, carbonates, and sulfolane compounds are preferred. More preferred are cyclic carbonates.

Representative examples of these include tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, anisole, monoglyme, acetonitrile, propionitrile, 4-methyl-2-pentanone, butyronitrile, valeronitrile, benzonitrile, 1,2- Dichloroethane, γ-butyrolactone, dimethoxyethane, methylformate, propylene carbonate, ethylene carbonate, vinylene carbonate, dimethylformamide, dimethylsulfoxide, dimethylthioformamide,
Examples include sulfolane, 3-methyl-sulfolane, trimethyl phosphate, triethyl phosphate, and mixed solvents thereof, but are not necessarily limited to these.

Furthermore, if necessary, the battery is constructed using parts such as a current collector, a terminal, and an insulating plate. The structure of the battery is not particularly limited, but may include a paper type battery with a positive electrode, a negative electrode, and if necessary a separator in a single layer or multiple layers, an aM type main battery, or a positive electrode, a negative electrode, and if necessary, a separator. For example, a cylindrical battery formed by winding a separator into a roll can be cited.

[Effects of the Invention] The battery of the present invention is small and lightweight, has particularly excellent cycle characteristics and self-discharge characteristics, and is extremely useful as a power source for small electronic devices, electric vehicles, power storage, and the like.

[Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

Example 1 Lithium carbonate 1.05 mol, cobal oxide 1.90 mol, stannic oxide 0.084 mol, scandium oxide 0
．． After mixing 002 mol and calcining at 850°C for 5 hours,
Baked in air at 850℃ for 12 hours.

Li+, osCoo, vsSno, 04ZSC11,
A composite oxide having a composition of 00202 was obtained. After pulverizing this composite oxide into an average layer of 3 μm using a ball mill, 1 part by weight of a dimethylformamide solution of polyacrylonitrile (concentration 2% by weight) and 0.2 part by weight of graphite as a conductive additive were added to 1 part by weight of the composite oxide. After mixing 1
5. Finish: The film was coated on one side of aluminum foil 1 cm x 5 cr to a film thickness of 75 mm.

The battery shown in FIG. 1 was assembled using this test piece as a positive electrode, lithium metal as a negative electrode, and a 0.6M LiC1)Oa-propylene carbonate solution as an electrolyte.

3 at a constant current of 25+sA (current density 5 mA/cs2)
After charging for 0 minutes, discharging was performed to 3.8V at the same constant current of <25+sA. The end-of-charge voltage, open terminal voltage, and overvoltage at this time are 4.20V, respectively.
.

They were 4.15V and 0.05V.

Thereafter, a cycle test was conducted under the same charging and discharging conditions, and the open terminal voltage and overvoltage in each cycle were as shown in Table 1, with almost no change.

Table 1 Examples 2-4. Comparative Examples 1 to 5 The same operations as in Example 1 were carried out except that the amounts of lithium carbonate, cobalt oxide, stannic oxide, and scandium oxide were changed to the amounts shown in Table 2, and various composite oxides were prepared. Obtained. The composition ratios are also shown in Table 2.

A battery similar to that of Example 1 was assembled using this composite oxide and evaluated.

Table 3 shows the open terminal voltage and overvoltage.

Table 3 Example 5~! 4 In Example 1, 0.002 mol of scandium oxide was replaced with an oxide or carbonate shown in Table 4.

The batteries were evaluated in exactly the same manner except that the number of charged moles shown in Table 4 was used. The obtained composite oxide composition and the measured overvoltage are also shown in Table 4.

Examples 15 to 17 Completely similar battery evaluations were carried out in Example 1, except that instead of 0.084 mol of stannic oxide, the oxides shown in Table 5 were used in the number of moles shown in Table 5. Ta. The obtained composite oxide composition and the measured overvoltage are also shown in Table 5.

(The following is a blank space) Example 18 The same operation as in Example 1 was performed except that 1.90 mol of nickel oxide was used instead of 1.90 mol of cobalt oxide, and Li+, os old o, 96sno, oasco, oo
A composite oxide having a composition of 2 oz. was obtained. When a battery similar to that of Example 1 was assembled using this composite oxide and evaluated, the overvoltage was found to be 0.09V.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a configuration example of a secondary battery of the present invention. In Fig. 1, l is the positive electrode, 2 is the negative electrode, 3.3' is the current collector rod, 4.4' is the SUS wire 7), 5.5' is the external electrode terminal,
6 is a battery case, 7 is a separator, and 8 is an electrolytic solution or solid electrolyte.

Claims (1)

[Claims] It has a layered structure and has the general formula A_xB_yC_zD_wO_2 [where A is at least one selected from alkali metals, B is a transition metal, and C is selected from the group of Al, In, and Sn. and D is (a) an alkali metal other than A, (b) a transition metal other than B, (c) IIa
At least one element selected from the group of group elements, (d) elements of the 2nd to 6th period of the IIIb group, IVb group, Vb group, and VIb group excluding Al, In, Sn, carbon, nitrogen, and oxygen. Representation,
x, y, z, w are 0.05≦x≦1.10, 0.8, respectively
5≦y≦1.00, 0.001≦z≦0.10, 0.0
It represents the number 01≦w≦0.10. ] A non-aqueous secondary battery characterized by using a composite oxide represented by these as a positive electrode.