JPS63307663A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PURPOSE:To design high potential and large capacity by using a specific substance as a positive electrode active substance, using a lithium alloy capable of absorbing and releasing lithium as a negative electrode active substance, and using one or two substances selected from LiClO4, LiAsF6 and LiPF6 as electrolyte. CONSTITUTION:A battery is constituted with a substance expressed by beta-LixV2O2 (0.1<=x<=0.6) as a positive electrode active substance, with a lithium alloy capable of absorbing and releasing lithium as a negative electrode active substance, and with one or more than one kinds of substances selected from LiClO4, LiAsF6 and LiPF6 as electrolyte. The lithium content in the lithium alloy is preferably 10-60% by the percentage of the number of atoms.

Description

[Detailed description of the invention] Hiko W Shi 1 minute! One aspect of the present invention relates to a chargeable/dischargeable non-aqueous electrolyte secondary battery that has a high potential, high energy density, long charge/discharge life, and excellent stability and reliability.

Many proposals have been made for high energy density batteries that use lithium as the negative electrode active material, and lithium batteries that use fluorinated graphite or manganese dioxide as the positive electrode active material are already commercially available. ing. However, these batteries are primary batteries.

There was a drawback that it could not be charged.

For secondary batteries that use lithium as the negative electrode active material, conventionally, metallic lithium is used as the negative electrode and titanium disulfide (T) is used as the positive electrode.
A non-aqueous electrolyte secondary battery has been proposed (Japanese Patent Application Laid-Open No. 50-54836) that uses xSx).However, this battery has a low potential of 2V on average due to the low oxidation-reduction potential of the Ti flood. In addition, dendrites are generated when charging negative i metal lithium, resulting in poor cycle characteristics.To solve this dendrite problem, the negative electrode contains 63% to 92% of the number of atoms. Lithium containing lithium
It has also been proposed to use an aluminum alloy (Japanese Unexamined Patent Publication No. 52-5423).

Although this battery shows improvements in cycle characteristics.

This had the disadvantage that the potential further decreased.

On the other hand, in order to obtain a high-potential secondary battery, it has also been proposed to use metallic lithium for the negative electrode and vanadium pentoxide (vioi) for the positive electrode (for example, JP-A-48-60240: W, B, Ehner and W.C.

Merz, Roc 2 8th power 5
sources Sympo, June 1978, P2
14), L, This battery also has the problem of poor cycle characteristics because it uses metallic lithium for the negative electrode, and V and Os have poor conductivity. In this case, in this battery, if a lithium-aluminum alloy is used instead of metallic lithium as the negative electrode, the cycle characteristics are considerably improved, but there is a drawback that the capacity at 2 V or more is lowered.

A major use of lithium secondary batteries is as a backup power source for IC memory;
If the voltage is less than 2V, memory backup becomes difficult.
Capacity at 2V or more is important, and a lithium secondary battery having high capacity at a potential of 2V or more is desired.

The present invention was made in view of the above circumstances, and an object of the present invention is to provide a high-potential non-aqueous electrolyte secondary battery that has a large capacity at a high potential of 2 V or more and has excellent cycle characteristics.

. In order to achieve the above object, the present invention provides the following formula (1) % formula %
(1) The material shown in (1) is used as a positive electrode active material, a lithium alloy capable of intercalating and releasing lithium is used as a negative electrode active material, and LiC
A non-aqueous electrolyte secondary battery is constructed using one or more selected from jlO4, LiAsF, and LiPF as an electrolyte.

That is, the present inventors have conducted extensive studies on positive electrode active materials for non-aqueous electrolyte lithium secondary batteries, and have found that the material represented by the above formula (1) has excellent characteristics as a positive electrode active material, and that it has excellent properties as a positive electrode active material. Combining lithium alloys such as lithium-aluminum alloys.

Furthermore, as an electrolyte 1"LiCjlO,, LiAsF,,L
iPF.

By using one or more of the following, non-aqueous electrolyte lithium has a high potential, high energy density, and long charge/discharge life as described above, and is suitable for use as a backup power source for IC memory. It was discovered that a secondary battery could be obtained, and this led to the present invention.

The present invention will be explained in more detail below.

As mentioned above, the secondary battery according to the present invention has the following formula (1): %formula%) The material represented by is used as the positive electrode active material.

Here, the value of X is in the range of 0.1 or more and 0.6 or less,
More preferably, it is in the range of 0.2 or more and 0.4 or less.

When creating a positive electrode using this positive electrode material, the particle size of the positive electrode material is not necessarily limited, but a positive electrode with higher performance can be created by using one with an average particle size of 3 μm or less.

In this case, the positive electrode is prepared by adding and mixing a conductive agent such as acetylene black or a binder such as fluororesin powder to these powders, kneading with an organic solvent, rolling with a roll, and drying. can be created. The amount of conductive agent mixed is 3 to 100 parts by weight of the positive electrode material of formula (1).
In the present invention, since the positive electrode material has good conductivity, the amount of the conductive agent used can be reduced. Further, it is preferable that the binder is mixed in an amount of 2 to 25 parts by weight based on 100 parts by weight of the above-mentioned positive electrode material.

A lithium alloy capable of intercalating and deintercalating lithium is used as the negative electrode active material of the secondary battery of the present invention. in this case,
Lithium alloys include Ila and Il containing lithium.
b, I[Ia, IVa, Va group metals or 6 alloys of 2 or more thereof can be used, but especially A containing lithium
Fi, In, Sn, Pb, Bi, Cd, Zn, or alloys of two or more of these are preferred, and lithium-aluminum alloy is most preferred. in this case.

The lithium content in lithium alloy is 1 as a percentage of the number of atoms.
The lithium content is preferably 0 to 60%, most preferably 25 to 40%, and by using a lithium alloy with such a lithium content, especially a lithium-aluminum alloy, the above-mentioned object of the present invention can be further achieved. effectively achieved.

There are no restrictions on the method for producing lithium alloys, and any known method can be used6.For example, when obtaining a lithium-aluminum alloy, metallurgical melting and electrochemical alloying methods may be used. Can be adopted. However, among these, aluminum that is electrochemically alloyed in an electrolytic solution is more preferable. In this case, the shape of aluminum can be selected as appropriate, and plate-shaped or powdered aluminum may be used depending on the type of battery. Those bonded and molded with a binder are used.

Furthermore, the electrolyte constituting the secondary battery of the present invention is Li(J
io,, LiAsF5. LiPF, and one of these
A species or two or more species may be used.

These electrolytes are usually used in a state dissolved in a solvent, and in this case, the solvent is not particularly limited, but relatively polar solvents are preferably used.

Specifically, propylene carbonate, ethylene carbonate, tetrahydrofuran, 2-methyltetrahydrofuran, dioxolane, and dioxane.

Glymes such as dimethoxyethane and diethylene glycol dimethyl ether, lactones such as γ-butyrolactone, phosphoric acid esters such as triethyl phosphate,
Boric acid esters such as triethyl borate, sulfolane,
Sulfur compounds such as dimethyl sulfoxide, nitrites such as acetonitrile, amides such as dimethylformamide and dimethylacetamide, dimethyl sulfate, nitromethane,
One or a mixture of two or more of nitrobenzene, dichloroethane and the like can be mentioned. Among these,
Especially ethylene carbonate, propylene carbonate,
One or more mixed solvents selected from butylene carbonate, tetrahydrofuran, 2-methyltetrahydrofuran, dimethoxyethane, dioxolane, and γ-butyrolactone are suitable.

The secondary battery of the present invention is usually constructed by interposing an electrolyte between the positive and negative electrodes, but in this case, a separator can be interposed between the positive and negative electrodes to prevent short circuiting of current due to contact between the two electrodes. As the separator, it is possible to use porous materials that allow the electrolyte to pass through or be contained therein, such as nonwoven fabrics, woven fabrics, and nets made of synthetic resins such as polytetrafluoroethylene, polypropylene, and polyethylene.

Charging Button 1 The secondary battery according to the present invention has a high potential of 2 V or higher, a large capacity, a high energy density, excellent cycle characteristics, and excellent stability and reliability.

Examples and comparative examples will be shown below, but the present invention is not limited to the following examples.

[Example 1] β-Li, ..., V, OS powder (average particle size 0.19%) was used as the positive electrode active material, and 15 parts by weight of acetylene black as a conductive agent and 15 parts by weight of acetylene black as a binder were added to 100 parts by weight of the powder. After adding 15 parts by weight of fluororesin powder and mixing thoroughly, it was kneaded with an organic solvent and rolled to about 350 mm with a roll.
The positive electrode was dried in vacuum at ℃ and punched out to a predetermined diameter.

The negative electrode is made by pressing lithium onto an aluminum plate punched to a predetermined size, and then forming the aluminum-lithium (AΩ-L) in an electrolytic solution.
i) Using an alloyed material (lithium content 30 at%), 1 liter of lithium/arsenic hexafluoride (LiAsF) was added to a mixed solvent of 2-methyltetrahydrofuran and ethylene carbonate (volume ratio 1:1). A battery A shown in FIG. 1 was assembled using the solution dissolved in mol/] as an electrolyte.

Here, in FIG. 1, 1 is a positive electrode, 2 is a positive electrode current collector made of stainless steel, and the positive electrode 1 and current collector 2 are integrated, and the current collector 2 is attached to the inner bottom of the positive electrode can 3. Spot welded to ml. In addition, 4 is a negative electrode, 5 is a negative electrode current collector,
The negative electrode 4 is spot welded to a current collector fixed to the inner bottom surface of the negative electrode can 6.

Furthermore, 7 is a separator made of polypropylene nonwoven fabric, which is impregnated with the electrolytic solution. In addition, 8
is an insulating backing. Also, the battery dimensions are 20mm in diameter.
It is 0m and 1.6cm thick.

This battery A has a discharge end voltage of 2 at a charging/discharging current of 1 mA.
．． OV, repeat charging and discharging at a charge end voltage of 3.5V, 5
The discharge curve at the 1st cycle and the capacity at that time were investigated. Figure 2 shows the discharge curve, and Table 1 shows the capacity results.

In addition, Table 2 shows the results of the cycle characteristics when this battery A was subjected to a constant capacity charge/discharge cycle test with a constant capacity discharge of 6 m AH and a charge end voltage of 3.5 V. In this case, the cycle life was Capacity is 3m at discharge end voltage 2, OV
The time point at which AH occurred was evaluated as the number of times the test was completed.

[Example 2] Lithium phosphorus hexafluoride (LiPF) 1 as an electrolyte
Battery B was prepared in the same manner as in Example 1, except that mol/base was dissolved in a mixed solvent of ethylene carbonate and propylene carbonate (volume ratio 1:1). A constant capacity charge/discharge cycle test was conducted. The results are shown in Table 2.

[Example 3] Lithium perchloride (LiCQ) was used as the electrolyte.
Battery C was prepared in the same manner as in Example 1 except that 1 mol/a of O4) was dissolved in a mixed solvent of propylene carbonate and tetrahydrofuran (volume ratio 1:1). A constant capacity charge/discharge cycle test was conducted using the method. The results are shown in Table 2.

[Comparative Example 1] A battery cell shown in FIG. 1 was prepared in the same manner as in Example 1 except that V and O were used as the positive electrode active materials.

A charge/discharge test was conducted on this battery in the same manner as in Example 1 except that the end-of-charge voltage was set to 3.3V. The discharge curve at the 5th cycle is shown in Figure 2, and the capacity at that time is shown in Table 1.The reason why the charging end voltage was set to 3.3V is because the charging curve rises suddenly if the potential is raised higher than this. be.

[Comparative Example 2] Lithium boron tetrafluoride (LiBF4) 1 as electrolyte
Battery E was prepared in the same manner as in Example 1, except that mol/capsule was dissolved in a mixed solvent of ethylene carbonate and propylene carbonate (volume ratio 1:1). A constant capacity charge/discharge cycle test was conducted. The results are shown in Table 2.

[Comparative Example 3] Battery F was prepared in the same manner as in Example 1 except that a lithium wheel punched out to a predetermined size was used as the negative electrode, and a constant capacity charge/discharge cycle test was conducted in the same manner as in Example 1. I did it. The results are shown in Table 2.

From the results shown in Table 1 and Table 2, it is confirmed that the battery according to the present invention has a large capacity at 2V or more and a long cycle life. Therefore, according to the present invention, the battery has a high discharge capacity at a high potential. It is possible to obtain an excellent non-aqueous electrolyte secondary battery having the following characteristics, and its industrial value is extremely large.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of the battery used in the charge/discharge test, and Figures 2 and 3 are positive electrode active materials such as β-Lta and av.
zos and v20. The discharge curve of the battery is shown.

Claims (1)

[Claims] 1. The following formula (1) β-Li_xV■O_5... (1) (However, 0
．． 1≦x≦0.6) is used as a positive electrode active material, a lithium alloy capable of intercalating and releasing lithium is used as a negative electrode active material, and LiC
A nonaqueous electrolyte secondary battery characterized in that an electrolyte is one or more selected from lO_4, LiAsF, and LiPF_6. 2. The battery according to claim 1, wherein the amount of lithium in the lithium alloy is 10 to 60 at.%. 3. The battery according to claim 1 or 2, wherein the lithium alloy is a lithium or aluminum alloy.