JPH01294372A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PURPOSE:To obtain a nonaqueous electrolyte secondary battery of high reliability which can be repeatedly charged/discharged for a long term by installing negative electrodes composed of organic fired body, positive electrodes including specified lithium compound and electrolyte into a battery-can, executing at least one charging operation and then sealing the can. CONSTITUTION:Installed into a battery-can 1 are negative electrodes 2 composed of organic fired body, positive electrodes 3 including LixMO2 (M being Co or Ni, 0.05<=x<=1.10) and electrolyte. At least one charging operation is executed and then the can is sealed. Thus, the gas generated by the charging operation is exhausted to the outside of the can. By sealing the can after the exhaustion, not so much gas is generated even if charging/discharging is repeated. Accordingly, nonaqueous electrolyte secondary battery which can be used for a long term can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a chargeable/dischargeable non-aqueous electrolyte secondary battery used as a power source for various electronic devices.

<Summary of the Invention> The present invention provides a negative electrode made of a fired organic material and a LixMO2 (
M represents at least one kind of Co or Ni, and 0.05≦
λ≦1.10. ) by charging a non-aqueous electrolyte secondary battery in which a positive electrode containing an electrolyte and an electrolyte are housed in a battery can at least once and then sealing the battery.
The idea is to suppress the generation of gas during charging and discharging, and to enable repeated use for a long period of time.

<Conventional technology> Conventionally, so-called non-aqueous electrolyte batteries that use light metals such as lithium or lithium alloys as negative electrode materials and organic electrolytes as electrolytes have a high working voltage (and extremely excellent storage stability). Since then, it has been widely used as a power source for electronic watches and various memory bank amplifiers as a battery with long-term reliability.

However, these currently used non-aqueous electrolyte batteries are used only as primary batteries, and their lifespan ends after one use, so there are points that need to be improved from an economic standpoint.

Therefore, along with the rapid progress of various electronic devices in recent years, the emergence of rechargeable non-aqueous electrolyte secondary batteries as a power source that can be used conveniently and economically for long periods of time has been awaited, and much research has been carried out. is in progress.

Generally, as a negative electrode active material for a non-aqueous electrolyte secondary battery, metallic lithium 5 lithium alloy (for example, Li-A1 alloy) is used.
, conductive polymers doped with lithium ions (such as polyacetylene and polypyrrole), and even compounds with lithium ions mixed into their crystals are used. A water electrolyte is used.

On the other hand, various materials have been proposed as positive electrode active materials as a result of research, and representative ones include, for example,
As described in Publication No.-54836, TiS2, M
Examples include oS2% NbSe2 and V205.

The discharge reaction of batteries using these materials proceeds as lithium ions in the negative electrode intercalate between the eyebrows of the positive electrode active material, and conversely, when charging, lithium ions deplete from the eyebrows of the materials to the negative electrode. Intercalate. In other words, by repeating the reaction in which lithium ions from the negative electrode move in and out of the cathode active material,
Can be repeatedly discharged and charged.

<Problems to be Solved by the Invention> However, as described above, for example, metallic lithium is used as the negative electrode active material, MO32 is used as the positive electrode active material, or Li-/1/! is used as the negative electrode active material. alloy.

When a lithium battery is made using TiS2 etc. as a positive electrode active material, Li and Li-
The problem is that the A1 alloy deteriorates and becomes powdery, making it impossible to use it for a long period of time.

Therefore, in order to solve such problems, it was proposed in Japanese Patent Application Laid-Open No. 62-908 to use a fired organic material as an electrode material for the negative electrode.
63, etc., and as a positive electrode active material, LixCoO2 (X = 0.05 to 1.10), which is a compound containing Li, is used because it has a high discharge potential.
It is proposed to use

However, when such a fired organic material is used as a negative electrode material, Li X Co Ot (-X = 0
．． If 05 to 1.10) is used as the positive electrode material, gas will be generated during charging and discharging, and the increase in internal pressure due to the gas generation will cause leakage of the electrolyte and damage to the battery, causing practical inconveniences. ing.

The present invention prevents electrolyte leakage and battery damage caused by gas generated by repeated charging and discharging of a non-aqueous electrolyte secondary battery as described above, and provides a reliable battery that can be repeatedly charged and discharged for a long period of time. This was proposed for the purpose of providing a non-aqueous electrolyte secondary battery with high performance.

<Means for solving the problem> Therefore, in order to achieve the above object, the present inventors analyzed the phenomenon of gas generation and found that the largest amount of gas is generated at the initial stage of charging. .

The present invention was proposed based on the above findings, and
A negative electrode made of a fired organic material and LiχM O2 (M is Co
or represents at least one type of Ni, and 0.05≦χ≦1.
A positive electrode containing IO (IO) and an electrolyte are housed in a battery can, and the battery can is sealed after one charging operation.

The negative electrode of the nonaqueous electrolyte secondary battery according to the present invention uses a fired organic material as an electrode active material. Examples of materials for the fired organic material that satisfy the conditions of the present invention include thermal decomposition of various organic compounds. An example of the above-mentioned organic material fired material of the present invention that can be obtained by firing or carbonization is vapor-grown carbon fiber. This vapor-grown carbon fiber is a carbon material obtained by subjecting carbon compounds such as benzene, methane, and carbon oxide to vapor-phase thermal decomposition in the presence of a transition metal catalyst, etc., using a known method similar to this. It refers to everything that can be obtained by. It is usually obtained in the form of fibers, that is, carbon fibers, by such a method, and it may be used as it is, or it may be used in the form of pulverized powder. Another example is a pinch type carbonaceous material. - Examples include petroleum pitch, asphalt pinch, coal tar pinch, crude oil cracking pinch, petroleum sludge pitch, etc., pinch obtained by thermal decomposition of carbon, pinch obtained by thermal decomposition of high molecular weight polymers, tetrabenzo Examples include pitch obtained by thermal decomposition of organic low-molecular compounds such as phenazine.

Ru. Furthermore, pitch-based calcined carbides such as needle coke and calcined carbides of polymers containing acrylonitrile as a main component can also be used.

On the other hand, the positive electrode contains L ix MO2 (M represents at least one transition metal, preferably Co or Ni, and 0.0
5≦X≦1.10), such as Li, coo2, LiClO4 or LixNi
A complex oxide represented by l Co(x-s)Oz (0≦3<l) is used.

The above-mentioned composite oxide can be obtained by using carbonates of lithium, cobalt, and nickel as starting materials, mixing them according to the composition, and firing the mixture. Of course, the starting materials are not limited to these, and the synthesis can be similarly performed using hydroxides and oxides of these metals. Further, the firing temperature may be appropriately set depending on the starting materials, but is usually in the temperature range of 600 to 1100°C.

In the resulting composite oxide, cobalt and nickel can be freely replaced depending on the raw material composition, but 1 in the above general formula
It is not particularly limited as long as the value of is in the range of 0≦Iris<1.

The electrolyte is not particularly limited, but includes, for example, propylene carbonate, ethylene carbonate,
1,2-dimethoxyethane, 1,2-jethoxyethane, γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3 dioxolane, 4-methyl-1,3-dioxolane, diethyl ether, sulfolane, methylsulfolane, acetonitrile, pro- A single solvent such as pionitrile or a mixture of two or more types can be used.

Any conventionally known electrolytes can be used, including LiC
lO4,, LiAsF5. LiPFe.

LiBF4, LIB(CoHs)4, Li
C1゜Libr, CH3SOa Lis CFa
One type or a mixture of two or more types, such as SO3Li, can be used.

Further, the separator may be made of any conventionally known insulating material, such as polypropylene, polytetrafluoroethylene, polyethylene, polyacetal, etc.

A non-aqueous electrolyte secondary battery is obtained by storing the above-mentioned materials in a battery can and sealing it, but in the present invention, a charging operation is performed before the sealing. It is necessary to perform this charging operation at least once, but considering that gas generation occurs most often at the beginning of charging and discharging and that it is necessary to shorten the time of non-aqueous electrolyte secondary batteries. You just need to decide on an appropriate number of times.

Furthermore, after performing the above-described charging and before caulking the battery, the gas generated within the battery may be degassed, for example, in a predetermined vacuum processing apparatus.

In a non-aqueous electrolyte secondary battery that uses a fired organic material as the negative electrode and l, i, MO2 as the negative electrode, impurities attached to the fired organic material are decomposed or electrolyzed during charging and discharging because the battery voltage is high. Gas generation is observed, which seems to be due to decomposition of the liquid.

In contrast, in the non-aqueous electrolyte secondary battery according to the present invention, charging is performed at least once before sealing the negative electrode, positive electrode, etc. stored in the container, so the gas generated by this charging is is evacuated from inside the container to the outside.

Therefore, since the container is sealed after this degassing, a large amount of gas will not be generated even if charging and discharging are repeated.

<Example> Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

The present embodiment of the present invention described below is an application of the present invention to a non-aqueous electrolyte secondary battery provided with a so-called explosion-proof mechanism. Therefore, first, the configuration of a non-aqueous electrolyte secondary battery provided with the above explosion-proof mechanism will be briefly described.

As shown in Fig. 1, the above-mentioned secondary battery has a negative electrode (2) and a positive electrode (3) wound several times through a separator (4) and housed in an outer can (1) as a power generating body. . In addition,
The outermost periphery of the power generating body serves as a negative electrode (2) and is in contact with the inner peripheral surface of the outer can (1), and the separator (4) is impregnated with an electrolytic solution (not shown). Therefore, the above negative electrode (2).

A battery reaction is caused by the positive electrode (3) and the electrolyte. A positive electrode lead (3a) is provided from the positive electrode (3) for connection to a safety valve (7) to be described later.

An insulating plate (5) is disposed above the power generating body. A small hole (not shown) is bored in the center of the insulating plate (5) through which the positive electrode lead (3a) is inserted. Moreover, above this insulating plate (5), an outer can (
1) is provided with a disc-shaped safety valve (7) held through a gasket (6) fitted into the inner periphery of the battery, and on the top of this safety valve (7) is a lid body that serves as the positive terminal of the battery. (8
) are provided. The safety valve (7) and the lid (8) are disposed in contact with each other at their peripheries, and the positive electrode (2) and the lid (8) are connected to the positive electrode lead (3a).
and are connected via a safety valve (7). Further, the upper surface of the safety valve (7) has grooves (7) radially extending from the center.
a) is formed and the pressure inside the outer can (1) increases, as shown in FIG. 2, the groove (7a) is torn and the gas inside escapes to the outside. In addition,
The lid body (8) has two gas insertion holes (8a) so that the gas blown out to the outside (in the direction of the arrow X in Figure 2) due to the bursting of the safety valve (7) is blown out to the outside of the battery.
, (8a) is perforated.

Next, the negative electrode of the non-aqueous electrolyte secondary battery having the above-mentioned configuration,
A positive electrode, an electrolytic solution, and the like were further created through each process described below, and the non-aqueous electrolyte secondary battery created through this process was charged and discharged under the conditions described below.

10 parts by weight of polyvinylidene fluoride was mixed with 90 parts by weight of crushed pinch coke as the lJ1 negative electrode (2), and N
- Melted in methylpyrrolidone to form a slurry. This slurry was coated on both sides of a copper foil with a thickness of o and o t am, and after drying, it was pressed to a thickness of 0.2 mm. Length 290mm.

An electrode of medium size 37 Hoho was prepared, and the weight of the negative electrode mixture was 2 g.

Next, as a positive electrode (3), LixC was prepared by mixing Li2Co3 and C0Co3 and firing the mixture in air at 900°C.
6 parts by weight of graphite and 3 parts by weight of polyvinylidene fluoride were mixed with 91M parts of crushed oCo2, and N-
A slurry made by dissolving it in methylpyrrolidone was applied to both sides of A1 foil with a thickness of 0.02 m, and after drying, it was pressed to make an electrode with a thickness of 0.2 m, a medium diameter of 37 N, and a length of 290 m, and a positive electrode. An electrode was prepared using a mixture weighing 5 g.

Then, current collecting leads were attached to the negative electrode (2) and positive electrode (3), respectively, and a microporous film with a width of 40 m and a thickness of 0.025 m was used as a separator to form a wire with a diameter of 14 m.
It was assembled into an exterior can (1) with a height of 451 cm and a height of 451 cm.

Next, insert the gasket (6) into the outer can (1),
Then, 1 mol/l of LiPF5 was added to propylene carbonate-dimethoxyethane (1:1 volume ratio) as an electrolyte.
2.5 ml of the melted liquid was injected at a ratio of 2.5 ml, and an aluminum safety valve (7) and a lid body (8) serving as a positive terminal were attached. The safety valve (7) used was one that bursts at 15 atm.

In this state, charging and discharging were repeated five times before caulking the outer can (1). Thereafter, it was degassed under vacuum to remove the gas generated by the charging and discharging.

In addition, the above assembly process and degassing process are both -60
It was carried out in dry air with a dew point of °C.

Next, the outer can (1) was caulked to be sealed.

The battery produced through the above steps is referred to as an example battery.

During the manufacturing process of the non-aqueous electrolyte secondary battery in the above example,
A comparative example battery was created by caulking the battery as it was without performing the charging/discharging process and the subsequent gas degassing process.

Each of the example battery and comparative example battery manufactured as described above was repeatedly charged and discharged 10 times under the following conditions: discharge 190mAX for 3 hours (maximum voltage 4.QV) charge 16.2Ω (final voltage 2.OV) .

After further repeating the above charging and discharging, each battery was stored at a temperature of 60° C. for 15 hours.

As a result, in the example battery, there was no abnormality in the safety valve (7), whereas in the comparative example battery, the safety valve (7) was found to have no abnormality.
) was activated, and the electrolyte filled inside leaked out of the battery, making it impossible to use it thereafter.

As is clear from the comparison with the example battery and the comparative example battery explained in the above example, during the process of creating the non-aqueous electrolyte secondary battery, charging and discharging were not performed at the stage before caulking and sealing the battery. By using the gas generated by this charging and discharging as a nonaqueous electrolyte secondary battery, it is possible to obtain a nonaqueous electrolyte that can be repeatedly charged and discharged for a long period of time.

In this example, the present invention was applied to a so-called jelly roll type non-aqueous electrolyte secondary battery, but
It goes without saying that the present invention can be applied to non-aqueous electrolyte secondary batteries, such as button-shaped and coin-shaped non-aqueous electrolyte secondary batteries.

<Effects of the Invention> According to the non-aqueous electrolyte secondary battery according to the present invention, a large amount of gas is not generated even when charging and discharging are repeated.

Therefore, it is possible to provide a nonaqueous electrolyte secondary battery that can withstand long-term use while avoiding deformation of the battery and leakage of the electrolyte filled inside due to repeated charging and discharging.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG. 2 is a sectional view showing a safety valve in a ruptured state. (1)...Exterior can (2)...Negative electrode material (3)...Cathode material patent Applicant: Sony Corporation Agent
Patent Attorney Koike Mima Sakae Tamura - Masaru Sato Figure 1 Figure 2

Claims (1)

[Claims] A negative electrode made of a fired organic material, Li_x, MO_2(M
represents at least one type of Co or Ni, 0.05≦x
≦1.10. ) and an electrolytic solution are housed in a battery can, which is sealed after at least one charging operation.