JP2547992B2 - Non-aqueous secondary battery - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a novel secondary battery, and more particularly, to a small and lightweight secondary battery.

[Related Art] In recent years, electronic devices have been remarkably reduced in size and weight, and accordingly, there has been a great demand for smaller and lighter batteries that serve as power sources. In the field of primary batteries, small and lightweight batteries such as lithium batteries have already been put into practical use, but since they are primary batteries, they cannot be repeatedly used, and their fields of use have been limited. On the other hand, in the field of secondary batteries, lead batteries and nickel-cadmium batteries have conventionally been used, but both have significant problems in terms of size and weight reduction.
From this viewpoint, non-aqueous secondary batteries have received a great deal of attention, but they have not yet been put to practical use. One of the reasons is that no positive electrode active material used for the secondary battery has been found to satisfy practical physical properties such as cycle characteristics and self-discharge characteristics.

Meanwhile, a new group of positive electrode active materials utilizing intercalation of a layered compound, which is a reaction type that is essentially different from that of conventional nickel-cadmium batteries, lead batteries, etc., has been attracting attention.

Such a new positive electrode active material does not cause a complicated chemical reaction in the electrochemical reaction during its charging and discharging, and therefore is expected to have an extremely excellent charge / discharge cycle property.

For example, as an example utilizing intercalation of a layered compound, a chalcogenite compound having a layered structure has attracted attention. For example, although chalcogenite compounds such as Li _x TiS ₂ and Li _x MoS ₃ have relatively excellent cycle characteristics, the practical electromotive voltage is at most even when the electromotive force is low and Li metal is used for the negative electrode. It was around 2V and was not satisfactory in terms of high electromotive force, which is one of the features of non-aqueous batteries. On the other hand, Li _x V ₂ O ₅ , Li, which also has a layered structure,
Metal oxide-based compounds such as _x V ₆ O ₁₃ , Li _x CoO ₂ , and Li _x NiO ₂ have attracted attention because they have the feature of high electromotive force. However, these metal oxide compounds have a high cycle property, a high utilization rate,
In other words, the performance in terms of the ratio that can actually be used for charging and discharging and the overvoltage during charging and discharging is inferior, and it has not yet been put to practical use.

In particular, Li _x CoO ₂ , disclosed in JP-A-55-136131,
The secondary battery positive electrode such as Li _x NiO ₂ has an electromotive force of 4 V or more when Li metal is used as the negative electrode, and the theoretical energy density (per positive electrode active material) is 1,100 WHr / kg, which is an amazing value. However, the ratio that can actually be used for charge and discharge is low, and only an energy density far from the theoretical value can be obtained.

[Problems to be Solved by the Invention] The present invention solves the above-mentioned problems of the metal oxide-based positive electrode and provides a novel non-aqueous secondary battery excellent in battery performance, particularly cycleability, utilization rate, and overvoltage characteristics. The purpose is to provide a positive electrode for a secondary battery.

According to the present invention has a layered structure, the general formula _{A x B y C z D w} O 2 [ where A is at least one selected from alkali metal, B is a transition metal, C is Al , In, Sn at least one selected from the group, D represents at least one selected from the groups (a) to (d), and x, y, z, w are each 0.05 ≦ x ≦ 1.10, 0.85 ≦ y ≦ 1.00, 0.001 ≦ z ≦ 0.10, 0.001 ≦ w ≦ 0.10.

(A) Alkali metal other than A, (b) Transition metal other than B, (c) Group IIa element, (d) Group IIIb (excluding Al and In), Group IVb (excluding carbon and Sn) , Vb group (excluding nitrogen), VIb group (excluding oxygen) elements of the second to sixth periods] is used as a positive electrode, and a non-aqueous secondary battery is provided. To be done.

 The novel layered composite metal oxide of the present invention has the general formula A_xB_yC_zD_w
O₂And A is selected from alkali metals
At least one selected from, for example, Li, Na, K, among which Li
Is preferred. The value of x varies depending on the charging status and discharging status
However, the range is 0.05 ≦ x ≦ 1.10. That is, by charging
A Ion deintercalation occurs,
The value becomes small, and the value of x is 0.05 in the fully charged state.
Reach Also, due to discharge, A Aeon's intercurry
Occurs, the value of x increases, and the state of full discharge is reached.
The value of x reaches 1.10.

B represents a transition metal, and Ni and Co are preferable among them. The value of y does not change due to charging and discharging, but 0.85 ≦ y
It is in the range of ≦ 1.00. In this case, B is 2 of the transition metals
It also includes the case where the number of types is more than one and the total y value does not deviate from the range of 0.85 ≦ y ≦ 1.00. When the value of y is less than 0.85 or exceeds 1.00, sufficient performance as an active material for a secondary battery, that is, a phenomenon such as deterioration of cycleability and increase of overvoltage occurs, which is not preferable.

C is at least one selected from the group consisting of Al, In and Sn, and Sn is particularly preferable. In this case, C contains two or more of Al, In, and Sn, and the total z value is 0.001 ≦ z.
It also includes the case where it does not deviate from the range of ≤0.10. In the novel active material for a secondary battery of the present invention, the function of C is extremely important and exhibits an excellent cycle property, particularly in deep charge and deep discharge cycles.
The value of z does not change due to charging and discharging, but 0.001 ≦ z ≦
The range is 0.10, preferably 0.005 ≦ z ≦ 0.075. When the value of z is less than 0.001, the effect of C is not sufficiently exhibited, the cycleability in deep charging and deep discharging described above is low, and the overvoltage during deep charging remarkably increases, which is not preferable. On the other hand, when the value of z exceeds 0.10, the hygroscopicity becomes too strong, the handling becomes difficult, and the basic characteristics of the 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) a group IIIb (excluding Al and In), a group IVb (carbon, Sn Group), V b group (excluding nitrogen),
It represents at least one element selected from the group of elements of the VI b group (excluding oxygen) of the 2nd to 6th periods, and the value of w does not fluctuate due to charging or discharging, but is in the range of 0.001 ≦ w ≦ 0.10, preferably The range is 0.001 ≦ w ≦ 0.005. In this case, D includes a case where two or more kinds of the above element groups are included and the total w value does not deviate from the above range. The value of w is 0.
When it is less than 001, the effect of D is not sufficiently exerted, the cycleability in deep charging and deep discharging described above is low, and the overvoltage during deep charging increases, which is not preferable. Also w
If the value exceeds 0.10, the effect of the C element is hindered, and the basic performance as the positive electrode for a secondary battery is impaired, which is not preferable.

In order to produce such a novel secondary battery positive electrode composite oxide of the present invention, A, B, C, D each metal oxide, hydroxide,
After mixing carbonates, nitrates, organic acid salts, etc., in air or in an oxygen atmosphere, 600 ° C to 950 ° C, preferably 70
It is obtained by firing in a temperature range of 0 ° C to 900 ° C.

A firing time of about 5 to 48 hours is usually sufficient. According the present invention obtained _{A x B y C z D w} O 2 , the discharge state of the secondary battery positive electrode, i.e. the value of x is obtained in the range of usually 0.90 to 1.10.

Thus _{A x B y C z D w} O 2 resulting charged as described above, de-intercalation reaction by the discharge, and the intercalation reaction, the value of x varies the range of 0.05 ≦ x ≦ 1.10.

If the reaction is represented by a formula, Is represented by (Here, x ′ represents the value of x before charging, and x ″ represents the value of x after charging).

The above utilization factor is It is a value defined by.

The novel active material for a non-aqueous secondary battery of the present invention is characterized in that this utilization rate is large, that is, it has an extremely stable cycle property against deep charge and discharge.

The novel composite oxide for a secondary battery positive electrode of the present invention has a very noble potential of 3.9 to 4.5 V with respect to the Li standard potential, and is particularly excellent when used as a positive electrode of a non-aqueous secondary battery. It exhibits 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 a secondary battery of the present invention, the positive electrode can be used in various shapes.

That is, it may be used in any shape such as a film, a fiber, and a powder, depending on the purpose.
The active material can be molded into an arbitrary shape such as a sheet and used.

As a molding method, a method is generally used in which the active material is mixed with a powdery binder such as Teflon powder or polyethylene powder and compression molded.

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

Conventionally, non-aqueous batteries have been excellent in performance such as high energy density and small size and light weight, but have disadvantages in output characteristics as compared with water-based batteries, and have not been widely used. In particular, in the field of secondary batteries that require output characteristics, this drawback is one of the factors hindering practical use.

The cause of poor output characteristics of non-aqueous batteries is high ionic conductivity in the case of aqueous electrolytes, which usually has a value of the order of 10 ^-1 Ω ^-1 cm ^-1 , whereas that of non-aqueous batteries is usually 10 ^-2 to 10 ^-4 Ω ^-1 cm ^-1
And has a low ionic conductivity.

One method of solving such a problem is to increase the electrode area, that is, to use a thin film or a large-area electrode.

The above method is a particularly preferable method for obtaining such a thin film and a large-area electrode.

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

The organic polymer used here is not particularly limited, but when the organic polymer has a relative dielectric constant at 25 ° C. and a frequency of 1 KHz of 4.5 or more, particularly preferable results are obtained, particularly as battery performance. It has excellent characteristics in terms of cycleability and overvoltage.

Examples of organic polymers satisfying such conditions include polymers or copolymers of acrylonitrile, methacrylonitrile, vinyl fluoride, vinylidene fluoride, chloroprene, vinylidene chloride, nitrocellulose, cyanoethyl cellulose, polysulfide rubber and the like. Can be mentioned.

In producing an electrode by such a method, the electrode is formed by applying and drying the coating liquid on a substrate. At this time, if necessary, it may be molded together with the current collector material, or alternatively, a current collector such as an aluminum foil or a copper foil may be used as the base material.

The battery electrode manufactured using the active material of the present invention, the binder, a conductive auxiliary, and other additives, for example, a thickener, a dispersant, a bulking agent, an adhesive auxiliary may be added, A material containing at least 25% by weight of the active material of the present invention.

Examples of the conductive auxiliary agent include metal powder, conductive metal oxide powder, carbon and the like. The addition of particular according auxiliary conductive agent is found A _x B _y C _z D remarkable effect when using the _w O ₂ of the present invention.

Among them, it is carbon that gives favorable results,
Normal _{A x B y C z D w} O significant overvoltage reduction effect of the addition of 1 to 30 parts by weight to ₂ 100 parts by weight is expressed and exhibits excellent cycle characteristics.

The carbon mentioned here does not always mean the specified carbon.

Examples of such carbon include graphite and carbon black. As a particularly preferable combination, carbon having an average particle diameter of 0.1 to 10 μ and average particle diameter of 0.01 μ to 0.08 μ
When the above carbons are mixed and used, a particularly excellent effect is given.

The negative electrode is not particularly limited, but is a light metal such as Li or Na or an alloy negative electrode thereof, a metal oxide negative electrode such as Li _x Fe ₂ O ₃ , Li _x Fe ₃ O ₄ , or Li _x WO ₂ , polyacetylene, poly-p. -A conductive polymer negative electrode such as phenylene, a vapor growth carbon fiber, a carbonaceous material negative electrode such as pitch-based carbon, polyacrylonitrile-based carbon fiber, and the like.

The basic components for assembling the non-aqueous secondary battery of the present invention include an electrode using the positive electrode and the negative electrode of the present invention, a separator, and a non-aqueous electrolytic solution. The separator is not particularly limited, and examples thereof include woven cloth, non-woven cloth, glass woven cloth, synthetic resin microporous membrane, and the like.
As described above, when using a thin film, a large area electrode, for example, a synthetic resin microporous film disclosed in JP-A-58-59072,
In particular, a polyolefin microporous film is preferable in terms of thickness, strength and film resistance.

 The electrolyte of the non-aqueous electrolyte is not particularly limited.
For example, LiClO_Four, LiBF_Four, LiAsF₆, CF₃SO₃Li, LiPF₆, Li
I, LiAlCl_Four, NaClO_Four, NaBF_Four, NaI, (n-Bu)_FourN ClO_Four, (N
-Bu)_FourN BF_Four, KPF₆Etc. In addition,
Examples of the organic solvent for the dissolution include ethers, ketones
, Lactones, nitriles, amines, amides, sulfur
Yellow compounds, chlorinated hydrocarbons, esters, carbon dioxide
G, nitro compounds, phosphate compounds, sulfo
Run compounds can be used.
But ethers, ketones, nitriles, chlorinated hydrocarbons
Preferred are elementary compounds, carbonates, and sulfolane compounds.
Yes. 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-butyl lactone, dimethoxyethane, methyl Formate, propylene carbonate, ethylene carbonate, vinylene carbonate, dimethylformamide, dimethylsulfoxide, dimethylthioformamide, sulfolane, 3-methyl-sulfolane, trimethyl phosphate, triethyl phosphate and a mixed solvent thereof can be mentioned. It is not necessarily limited to these.

If necessary, a battery is configured using components such as a current collector, a terminal, and an insulating plate. In addition, the structure of the battery is not particularly limited, but a positive electrode, a negative electrode, and, if necessary, a paper type battery having a single or multiple layers of separators, a laminated type battery, or a positive electrode, a negative electrode, For example, a form of a cylindrical battery or the like in which a separator is wound in a roll shape is given as an example.

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

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

Example 1 1.05 mol of lithium carbonate, 1.90 mol of cobalt oxide, 0.084 mol of stannic oxide, and 0.002 mol of scandium oxide were mixed, calcined at 650 ° C. for 5 hours, and then calcined in air at 850 ° C. for 12 hours. A composite oxide having a composition of Li _1.03 Co _0.95 Sn _0.042 Sc _0.002 O ₂ was obtained. This composite oxide was pulverized with a ball mill to an average of 3 μm, and then 1 part by weight of the composite oxide was mixed with 1 part by weight of a dimethylformamide solution of polyacrylonitrile (concentration: 2 wt%) and 0.2 part by weight of graphite as a conduction aid. Afterwards, 15μm aluminum foil 1cm × 5cm
Was coated on one side to a film thickness of 75 μm.

This test piece was used as a positive electrode, lithium metal was used as a negative electrode, and a 0.6M-LiClO ₄ -propylene carbonate solution was used as an electrolytic solution to assemble the battery shown in FIG. 1.

After charging with a constant current of 25 mA (current density 5 mA / cm ² ) for 30 minutes, the battery was discharged with a constant current of 25 mA to 3.8 V. The end-of-charge voltage, the open-circuit terminal voltage, and the overvoltage at this time were 4.20V, 4.15V, and 0.05V, respectively.

After this, cycle test under the same charge and discharge conditions,
The open-circuit terminal voltage and the overvoltage in each cycle are as shown in Table 1 and hardly changed.

Examples 2 to 4 and Comparative Examples 1 to 5 The same operation as in Example 1 was 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. Various complex oxides were obtained. The composition ratio is also shown in Table 2.

This composite oxide was assembled into a battery similar to that of Example 1,
An evaluation was made.

 Table 3 shows the open circuit voltage and overvoltage.

Examples 5 to 14 The same battery evaluations were carried out as in Example 1 except that 0.002 mol of scandium oxide was replaced by the oxide or carbonate shown in Table 4 in the same mol number as shown in Table 4. . The composition of the obtained composite oxide and the measured overvoltage are also shown in Table 4.

Examples 15 to 17 The same battery evaluations as in Example 1 were carried out except that the oxide shown in Table 5 was used instead of 0.084 mol of stannic oxide in the same mole number as shown in Table 5. The composition of the obtained composite oxide and the measured overvoltage are also shown in Table 5.

Example 18 The same operation as in Example 1 was carried out except that 1.90 mol of nickel oxide was used instead of 1.90 mol of cobalt oxide.
A composite oxide having a composition of _1.05 Ni _0.96 Sn _0.04 Sc _0.002 O ₂ was obtained. When a battery similar to that of Example 1 was assembled from this composite oxide and evaluated, the overvoltage was 0.09V.

[Brief description of drawings]

FIG. 1 is a sectional view of a configuration example of a secondary battery of the present invention. In FIG. 1, 1 is a positive electrode, 2 is a negative electrode, 3, 3 ′ are current collector rods,
4,4 'is a SUS net, 5,5' is an external electrode terminal, 6 is a battery case, 7 is a separator, and 8 is an electrolytic solution or a solid electrolyte.

Claims (1)

(57) [Claims] 1. A has a layered structure, the general formula _{A x B y C z D w} O 2 [ where A is at least one selected from alkali metal, B is a transition metal, C is Al, It is at least one selected from the group of In and Sn, D represents at least one selected from the group of (a) to (d), and x, y, z, and w are each 0.05 ≦ x ≦ 1.10. , 0.85 ≦ y ≦ 1.00, 0.001 ≦ z ≦ 0.10, 0.001 ≦ w ≦ 0.10. (A) Alkali metal other than A, (b) Transition metal other than B, (c) Group IIa element, (d) Group IIIb (excluding Al and In), Group IVb (excluding carbon and Sn) , Vb group (excluding nitrogen), VIb group (excluding oxygen) elements of the 2nd to 6th periods] is used as a positive electrode, a non-aqueous secondary battery.