JPH02239574A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PURPOSE:To avoid current concentration and restrict formation change at peripheral parts of a negative pole by disposing an insulation layer at the peripheral parts. CONSTITUTION:For a nonaqueous electrolyte secondary battery having a positive pole 2 mainly consisting of active material which can be re-charged and a negative pole 4 consisting of lithium or lithium alloy, an insulation layer 7 is formed by applying epoxy resin (for solder-resist) for a width of 0.5mm at peripheral parts of a disc-formed negative pole 7 of lithium-aluminum alloy and drying it. If lithium is solely used for the negative pole, metal lithium of a purity of more than 99.99% shall preferably be used.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a positive electrode based on a rechargeable active material such as molybdenum trioxide, vanadium pentoxide, manganese oxide, titanium or niobium sulfide. The present invention relates to a non-aqueous electrolyte secondary battery equipped with a negative electrode made of lithium or a lithium alloy.

mouth. Conventional uL technology In this type of secondary battery, when discharging, lithium, which is the negative electrode active material, becomes ions and dissolves in the electrolyte, and when charging, the reverse reaction occurs and the metal lithium is electrolytically deposited on the negative electrode. There is a problem in that metallic lithium grows in a dendritic shape on the negative electrode due to repeated discharges, and eventually reaches the positive electrode, causing an internal short circuit.

To solve this problem, we used a lithium alloy as the negative electrode,
For example, it has been proposed to use a lithium-aluminum alloy.

There are two methods for producing lithium alloys: the chemical production method and the electrochemical production method.
Due to its characteristics, it is produced using an electrochemical method.

Electrochemical manufacturing methods include a method in which lithium is pressed onto an alloy substrate to form a crimped object, and then this crimped object is immersed in an organic solvent containing a lithium salt, and a method in which lithium metal is used as a counter electrode and a separator is formed. There is a method in which an alloy substrate is cathodically reduced in an organic solvent containing a lithium salt.

However, even in lithium alloys, if charging and discharging are repeated, fA. There is a problem in that current concentration occurs at the edge of the periphery of the electrode plate of the rod, the shape of the negative electrode changes significantly due to charging and discharging, and the periphery of the negative electrode lithium alloy becomes brittle and easily breaks. Therefore, in order to suppress the weakening of the peripheral edge of the negative electrode plate,
The crimping area SLI of lithium is S++. /SAt≦
A method has been proposed in which a lithium-aluminum alloy is produced by crimping the aluminum plate with the peripheral edge of the crimped side surface exposed so that the lithium-ion temperature is 0.99, and using the vapor chemical fishing method (
(See Japanese Patent Application Laid-open No. 146351/1983). The lithium-aluminum alloy manufactured by this method is difficult to break and is easy to handle during manufacture, but when a battery is actually assembled using this lithium-aluminum alloy as a negative electrode and repeatedly charged and discharged, the aluminum base is exposed at the periphery of the lithium-aluminum alloy. As a result, alloying also occurs in the aluminum base portion at the periphery, and eventually the entire surface of the aluminum plate is alloyed. Therefore, when charging and discharging are repeated, the alloy at the peripheral edge becomes brittle and crumbles, causing internal short circuits and shortening the cycle life.

As described above, even if a lithium alloy is used as the negative electrode, the problem of the peripheral portion remains. Similarly, this problem at the periphery, ie, shape change, also occurs when lithium is used alone.

C. Problems to be Solved by the Invention The present invention aims to suppress the deterioration of battery performance caused by the tL pole as described above.

two. Means for Solving the Problems The present invention is characterized by comprising a positive electrode mainly made of a rechargeable active material and a negative electrode made of lithium or a lithium alloy, with an insulating layer disposed around the periphery of the negative electrode. Secondary non-aqueous electrolyte! It's at the pond.

Further, it is preferable to use 4r@lithium with a purity of 99.99% or more as the negative electrode.

Ho. Function According to the device of the present invention, since the insulating layer is disposed on the peripheral edge of the negative electrode, current concentration does not occur and changes in the shape of the peripheral edge are suppressed.

In addition, when using lithium alone as the negative electrode, purity 9
9.9 It is preferable to use 9% or more of metallic lithium. To explain the reason in detail, lithium metals generally used in batteries have a purity of about 99.8% and contain impurities such as sodium, calcium, potassium, and iron. These impurities have a large effect on the tree-like growth of metallic lithium. That is, when lithium is repeatedly dissolved and deposited in the negative electrode due to charging and discharging, the impurity concentration on the negative electrode surface increases. Here, there is a difference in potential between lithium and impurities, and this complicated potential distribution facilitates the formation of nuclei during metal lithium electrodeposition.

Therefore. When using metallic lithium alone as a negative electrode, the purity is 9.
9.9 It is advantageous to use 9% or more.

fart. Example Examples of the present invention will be described in detail below.

FIG. 1 shows a half-sectional view of a flat non-aqueous electrolyte secondary battery according to an embodiment of the present invention. ) are pressed together via the positive electrode current collector (3).The positive electrode (2)
is manganese dioxide containing Li@MnOs as an active material and acetylene brane as a conductive agent.
A predetermined amount of a positive electrode mixture prepared by mixing a fluorine resin and a fluorine resin as a binder in a ratio of 85:10:5 was taken and molded.

(4) is a negative electrode made of a lithium-aluminum alloy plate, which is crimped to the inner bottom surface of a stainless steel negative electrode can (6) via a negative electrode current collector (5).

Here, negative i(4) is created using the following method. That is, the diameter is φ19. Oi. Epoxy resin (for solder resist) is applied to the periphery of one side of a disc-shaped aluminum plate with a thickness of 0.7M in a width of 0.5 mm, and dried to form an insulating layer (
7). This aluminum plate is used as a cathode and the thickness is 0.
．． 3 5all lithium plate Fn pole L. Tei I
M L i C J! 04-PC/DME(1/
1. ) in an electrolytic solution and left for 20 hours to obtain a lithium-aluminum alloy.

The diameter of the aluminum alloy surface obtained in this way is φ18. OIIIffi, and the diameter of the aluminum base is φ1 9. Omm, so the area ratio is 0.90
It becomes. The paint applied to the aluminum plate is not limited to epoxy resin, but polytetrafluoroethylene, silicone resin, etc. can also be used.

Furthermore, the solute and solvent used in producing the alloy are not limited to those mentioned above, and can be used.

(8) is a polypropylene sebaret, in which L is added to a mixed solvent of propylene carbonate and dimethoxyethane.
iCIO. It is impregnated with a non-aqueous electrolyte in which IM is dissolved. (9) is insulating packing. Battery dimensions are diameter φ2
4, Qm, thickness 3.0-1, and the theoretical capacities of the positive and negative electrodes are 100ffi^h and 280 mAh, respectively. This invention battery is referred to as (A).

Comparative Example 1 A disc-shaped aluminum plate with a diameter of φ1 9.01111 mm and a thickness of 0.71 all was used as a cathode, and a lithium plate with a diameter of φ 18.0 mm and a thickness of 0.35 wm was used as an anode, obtained in the same manner as in Example. A comparative battery (81) was prepared in the same manner as in the example except that a lithium-aluminum alloy, that is, an alloy in which the aluminum substrate was exposed at 0.5 of the periphery of the lithium-aluminum alloy, was used as the negative electrode.

Comparative Example 2 A disk-shaped aluminum plate with a diameter φ1 9.Qm and a thickness 0.7Il1lll is used as a cathode, and a diameter φ1 9.0+ss
A lithium-aluminum alloy obtained in the same manner as in the example using a 0.3-5 m thick lithium plate as an anode, that is, an alloy in which the entire surface of the aluminum plate is alloyed to form a lithium-aluminum alloy, is used as the negative electrode. A comparative battery (B2) was prepared in the same manner as in the example except for the following.

FIG. 2 shows the charge/discharge cycle characteristics of these batteries.

The charging and discharging conditions are: discharging at a current of 3 mA for 8 hours;
The battery was charged at A, and the final charge voltage was 3.5V. It can be seen from FIG. 2 that the battery (A) of the present invention has improved cycle characteristics.

to. Effects of the invention] As mentioned above, a non-aqueous electrolyte secondary equipped with a negative electrode made of lithium or lithium alloy! In a pond, by disposing an insulating layer around the periphery of the paddle, it is possible to prevent current from concentrating on the periphery, and it is possible to suppress deterioration of battery performance due to changes in the shape of the periphery. Its industrial value is extremely large.

In the examples, a lithium-aluminum alloy was used as the lithium alloy, but the metal alloyed with lithium is not limited to aluminum, and alloys with other metals such as indium, magnesium, and lead may also be used. can.

Alternatively, the insulating layer may be provided by a method in which a lithium alloy is created, and then a paint is applied to the periphery of the lithium alloy and then dried.

Furthermore, lithium alone may be used as the negative electrode, and in that case, it is preferable to use metallic lithium with a purity of 99.99% or more.

[Brief explanation of drawings]

FIG. 1 is a half-sectional view of the battery of the present invention, and FIG. 2 is a diagram of the charge/discharge cycle characteristics of the battery. (1)...Positive electrode can, (2)...Positive electrode, (4)...
Negative electrode, (6)...each negative electrode, (7)...insulating layer, (8
)...Severator, (9)...Insulating packing.

Claims (2)

[Claims] (1) A non-aqueous electrolyte secondary comprising a positive electrode mainly made of a rechargeable active material and a negative electrode made of lithium or a lithium alloy, with an insulating layer disposed around the periphery of the negative electrode. battery. (2) The non-aqueous electrolyte secondary battery according to claim 1, wherein the negative electrode is made of metallic lithium with a purity of 99.99% or more.