JPS59128760A - Manufacture of nonaqueous electrolyte battery - Google Patents

Abstract

PURPOSE:To secure formation of a protective film on the surface of lithium so as to improve the preservation performance and reduce variation in the preservation performance of a lithium battery by leaving the lithium to stand in an atmosphere of carbon dioxide gas before the lithium is incorporated in the battery. CONSTITUTION:Lithium is left to stand in an atmosphere containing carbon dioxide gas prior to being incorporated in a battery. For instance, in the first process of making a negative electrode, ingot-like lithium is formed into a long ribbon-like shape of 0.25mm. thickness and 20mm. width in dry air of below 4% relative humidity by extrusion molding while the ribbon-like lithium is wound in hoop-like form which is then sealed and stored in a metallic can charged with argon. Next the ribbon-like lithium is punched into disks of 14mm. diameter and 0.25mm. thickness in dry air. Then the thus obtained disk-like lithium 3 is pressed and integrated with a negative current collector net 2 welded to the inner surface of a sealing plate 1. Next this is left to stand in an atmosphere of carbon dioxide gas for a given time before being combined with other parts. After that electrolyte is poured in the battery before it is sealed.

Description

Detailed Description of the Invention: Industrial Field of Application The present invention uses lithium as a negative electrode active material, uses a non-aqueous electrolyte in which an inorganic salt is dissolved in an organic solvent as an electrolyte, and uses various oxides and halides as a positive electrode. , relates to a method for manufacturing a non-aqueous electrolyte battery using any solid active material such as sulfide.

2.

Structures of conventional examples and their problems There are various types of non-aqueous electrolyte batteries, and batteries with different characteristics can be obtained depending on the type of positive electrode active material and electrolyte. The Yosimi Pond system is classified. The positive electrode active materials include manganese dioxide, copper oxide, bismuth oxide,
Oxides such as lead oxide, vanadium pentoxide, chromium oxide, carbon fluoride, halides such as copper chloride, nickel fluoride, copper fluoride, sulfides such as binary molybdenum, iron sulfide, copper sulfide, and the above. There are too many types of solid positive electrode active materials, such as composite compounds, chromates, and tungstates. Among these, typical batteries that have been put into practical use include fluorocarbon/lithium batteries and manganese dioxide/lithium batteries, both of which have a power consumption of approximately 3V.
voltage can be obtained.

In addition, copper oxide/lithium batteries and iron sulfide/lithium batteries, which can obtain a voltage of about 1.5 μ, are also in practical use.

On the other hand, the electrolytes used in these various battery systems vary, but generally they are a single solvent of r-butyrolactone propylene carbonate, or a combination of these with 1-2 dimethoxyethane, dioxolane, tetrahydrofuran, etc.
Inorganic salts such as lithium perchlorate and lithium fluoroborate are dissolved in a solvent mixed with acetonitrile or the like. Among these lithium batteries, at least the above-mentioned batteries that are currently in practical use have not only high energy density but also excellent storage properties, and have recently been replaced by various conventional aqueous batteries. So electronic watch,
It occupies the position as the main power source for various fields such as calculators and memory backup.

In order to obtain a lithium battery with excellent storability, it is necessary to meet many requirements, including the fact that the active material of the positive electrode is melted into the electrolyte, that no chemical reaction occurs, and that the electrolyte itself is The main conditions are that it is chemically stable and does not deteriorate over a long period of time, and that it is also stable against the redox effects of the positive and negative electrode active materials. By combining an active material and an electrolyte that meet these conditions, a lithium battery that can be put to practical use as described above can be constructed. Among the above conditions, in order to suppress the chemical reaction between the lithium of the negative electrode active material and the electrolyte during storage, it is essential that an extremely thin reaction prevention film be formed on the surface of the lithium. Without this protective film, almost all nonaqueous electrolytes react with lithium, corroding the lithium, and decomposing or polymerizing themselves, resulting in significant self-depletion and expansion of the battery due to gas generation.Therefore, The degree to which contact between the active lithium surface and the electrolyte is cut off by the eyelid membrane during battery storage is a factor that determines storage performance. In order to reliably satisfy this factor, even batteries that are currently in use require more advanced technology, reducing quality variations in storage conditions and further improving performance. Among these, propylene carbonate and γ-butyrolactone have the property of forming a protective film on the lithium surface relatively easily when they come into contact with lithium. protects the surface of the negative electrode lithium, and when the discharge reaction begins, it is physically destroyed and the active lithium comes into contact with the electrolyte, allowing the electrochemical oxidation reaction to proceed smoothly.However, the above-mentioned sole solvent The electrolyte solution in which non-IP is dissolved has low conductivity,
Since the viscosity is also high, strong load discharge and low temperature performance are insufficient, and in many cases, solvents with relatively low boiling point and low viscosity, such as 1-2 dimethoxyethane, dioxolane,
Mix ether solvents such as tetrahydrofuran and relatively low viscosity solvents such as acetonitrile in appropriate ratios,
Obtain electrolyte with low viscosity and high conductivity, strong load discharge characteristics,
A method is adopted to ensure low-temperature properties. However, when the above-mentioned ether-based solvents come into contact with lithium, they not only have a poor ability to form a protective film, but if the formation of a thin protective film is incomplete, they may destroy the already formed protective film and further activate the lithium. It has the property of corroding and decomposing or polymerizing itself. Therefore, when using an electrolytic solution in which an inorganic salt is dissolved in a mixed solvent, the discharge performance is improved, but the storage performance of lithium is unstable, and γ- It is necessary to ensure storage performance by setting the mixing ratio with low viscosity solvents such as ethers within a range where the formation of a protective film by butyrolactone or propylene carbonate is sufficient. Generally, ether solvents are mixed at a volume ratio of 30 to 70%, and the composition is determined based on the requirements that are emphasized in each case, such as storage stability, discharge performance, cost, and compatibility with the manufacturing process. This is done with an appropriate balance in mind. However, even in formulations that take these balances into consideration, there is a lack of reliability in ensuring storage performance. This is due to the lack of certainty regarding the formation of the protective film on the surface of the negative electrode. Factors that affect the formation or destruction of this protective film include the type of inorganic salt to be dissolved in addition to the blending ratio of the solvent mentioned above.
Due to the complex effects of various factors such as impurities and moisture in the positive and negative electrodes and in the electrolyte, it is extremely difficult to control the process to reliably manufacture batteries with good storage life. There is a need to establish a method for manufacturing homogeneous batteries.

Purpose of the Invention The purpose of the present invention is to improve the storage performance and reduce variations in non-aqueous electrolyte batteries using lithium as a negative electrode.
This provides a means for reliably forming the above-mentioned protective film on the surface of lithium.

Structure of the Invention In order to achieve the above-mentioned object, the present invention involves, in the manufacturing process of a non-aqueous electrolyte battery using lithium as a negative electrode active material, leaving lithium in a carbon dioxide atmosphere before incorporating it into the battery. It is characterized by providing a process.

Lithium negative electrodes are usually produced by extrusion molding a lithium ingot into a hoop shape of a predetermined thickness, rolling if necessary, and then cutting into a predetermined electrode shape by punching, extrusion, etc. It is incorporated into the battery after a process of connecting it to the collector. In normal cylindrical batteries, the negative electrode is constructed by press-fitting a porous current collector such as nickel net or expanded metal into a rectangular lithium plate, and in button-shaped batteries, the negative electrode is formed by press-fitting a porous current collector such as nickel net or expanded metal into a rectangular lithium plate. Generally, lithium is processed into a disk shape and crimped together, and these processes are performed in a dry atmosphere as part processing steps, and the processed negative electrode is used to create positive electrodes, separators, and battery cases.

It goes into the assembly process along with other battery parts such as electrolyte.

In the above negative electrode processing steps, physical changes occur on the outer surface including the cut surface due to mechanical processing of lithium, such as extrusion molding, rolling, cutting, and crimping of lithium. Normally, these processing and storage processes are carried out in an inert gas atmosphere such as argon or in dry air. When exposed to a dry atmosphere for a long time, a thin film composed of lithium carbonate, lithium oxide, etc. is formed on the surface, making it somewhat more inactive than the original lithium surface, but after the mechanical processing described above, When the thin film is destroyed, a new active surface is exposed. Therefore, when processed and stored in an argon atmosphere, the surface remains relatively active with almost no thin film formation, and when processed and stored in dry air, the surface becomes relatively inert. However, as the material goes through the processing steps, active parts and inactive parts become unevenly distributed. The above thin film is similar to the protective film formed by reaction with γ-butyrolactone and propylene carbonate in the electrolyte after battery construction, and prevents self-depletion of the negative electrode and deterioration of the electrolyte during battery storage. Although it has a somewhat supportive effect, the degree of formation of the thin film varies depending on the area, and even if a uniform film is formed in a dry atmosphere, the formed layer is extremely thin, and it alone is insufficient for the negative electrode. It's impossible to suppress the wear and tear.

The present invention includes a step of exposing the lithium surface to a carbon dioxide atmosphere in order to ensure that a protective film of lithium carbonate is formed over the entire surface of the negative electrode reaction surface in the lithium negative electrode processing process prior to battery assembly. It is something that Thereby, even if the protective film formed within the battery is insufficient, self-depletion of the negative electrode can be suppressed by the protective film formed in the above processing step. Normally, there is about 0.03% carbon dioxide gas in the air, and even in the dirty air of the living environment of the subcommittee, at most less than 0.0% carbon dioxide gas exists1.
0-5, only. According to the results of experiments described below, the carbon dioxide concentration at which a lithium carbonate film effective as a negative electrode protective film can be formed is preferably at least 1% or more.
% or more, and the other components may be any inert gas such as dry air or argon.

DESCRIPTION OF EXAMPLES Next, a battery for which the effects of the present invention have been experimentally confirmed and a manufacturing method thereof will be described.

The figure shows a cross section of a flat battery. In the figure, 1 is a stainless steel sealing plate, 2 is a negative electrode current collector net made of nickel net electrically welded to the inner surface of the sealing plate 1, and 3 is a negative electrode current collector. Disc-shaped metallic lithium is crimped onto the net 2, 4 and 4' are separators made of polypropylene nonwoven fabric, 5
6 is a positive electrode formed by mixing carbon heptide with acetylene black and a binder made of styrene butadiene rubber, 6 is a stainless steel positive electrode case, and 7 is titanium electrolyzed on the inner surface of the positive electrode case 6. The positive electrode current collector is a hollow disc-shaped positive electrode made by the company, and is in close contact with the positive electrode 5. Reference numeral 8 denotes a polypropylene gasket, which serves to seal the opening of the positive electrode case 6 by bending the opening. Inside the battery, electrolytes of various compositions, which will be described later, are sealed.

In the battery processing process, the negative electrode side is first processed by extrusion molding of ingot-shaped lithium at a relative humidity of 4%.
Thickness 0.25Wrrn in dry air below.

The ribbon was processed into a long ribbon with a width of 2 of and wound into a hoop, and then stored in a metal can sealed with argon. Next, this can was opened in dry air, and in the same atmosphere, it was pressed into a disk shape with a diameter of 14 mm and a thickness of 0.25 m, and then a negative electrode current collector net 2 was welded to the inner surface of the sealing plate 1. A disc-shaped lithium is crimped onto the lithium and integrated. Next, this is placed in a carbon dioxide atmosphere of a predetermined concentration, which will be described later, and left for a predetermined period of time. Then, take it out from the carbon dioxide atmosphere,
It is assembled with other parts, and after injecting electrolyte, it is sealed. The external shape of this battery is 2Of1m in diameter.

The total height is 2.0m. Next, we will describe the results of various battery prototypes manufactured using the above manufacturing method by changing the treatment conditions for the negative electrode in a carbon dioxide atmosphere and the composition of the electrolyte, and storage tests at high temperatures. Table 1 shows the trial production conditions for each battery.

Table 1 3 PC stands for glopylene carbonate) and DME stands for dimethoxyethane.

Table 2 shows the discharge capacity maintenance rate (average value of n = 10,
, maximum value, minimum value).

Margin below 4 Table 2 15 As seen in Table 2, both batteries A and P, whose negative electrodes were simply treated with dry air (relatively less than 4 inches), had a significant capacity deterioration due to storage, and their capacity decreased. The variation is also large. On the other hand, negative electrodes treated in dry air containing various proportions of carbon dioxide gas, argon gas, and carbon dioxide gas alone exhibit uniformly less capacity deterioration and variation, and in an atmosphere with a large amount of carbon dioxide gas. The more treated, the more effective the treatment is for a short period of time, and similar effects were obtained in both cases where lithium fluoroborate and lithium perchlorate were used as the solute in the electrolytic solution.

Effects of the Invention As mentioned above, these results show that by forming a protective film of lithium carbonate on the lithium surface, self-depletion of the negative electrode and deterioration of the electrolyte during storage are effectively suppressed, and the storage performance of the battery is improved. This can be effectively improved by implementing the present invention.

[Brief explanation of the drawing]

The figure is a sectional view of a flat lithium battery assembled in an example to confirm the effects of the present invention. 1... Sealing plate, 3... Lithium negative electrode,
4.4'...Severe~ri, 6...Positive electrode,
6...Battery case, 8...Insulating gasket.

Claims (2)

[Claims] (1) A method for manufacturing a non-aqueous electrolyte battery using lithium as a negative electrode active material, characterized by including a step of leaving the battery in an atmosphere containing carbon dioxide gas prior to incorporating lithium into the battery. Manufacturing method for non-aqueous electrolyte batteries. (2) Manufacturing the nonaqueous electrolyte battery according to claim 1, wherein the carbon dioxide atmosphere is dry air or an atmosphere in which argon and carbon dioxide are mixed at a weight ratio of 99=1 to o:1oo. Law.