JPS6041761A - Lithium organic secondary battery - Google Patents

Abstract

PURPOSE:To increase charge-discharge performance by applying silver plating to the portion where lithium is electrolytically deposited on the stainless steel surface of a negative current collector. CONSTITUTION:Lithium or lithium alloy with aluminium, mercury, zinc, or cadmium is used as a negative active material. For example, for a button battery, silver plating is applied to a negative can 2 and a negative current collecting net 3, and for a cylindrical battery, silver plating is applied to a negative can, a negative current collecting net, and negative current collecting rod. In this way, according to the battery construction, silver plating is performed in the portion where electrolytically deposited lithium is in contact with the negative current collector. Thereby, decrease of charge-discharge reversibility is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION It is an object of the present invention to provide a lithium organic secondary battery with excellent charging and discharging characteristics.

In a lithium organic secondary battery using lithium or a lithium alloy as the negative electrode/l'i'1t, stainless steel is generally used for the compatibility of the part in contact with the power generation element. This is based on the reason that stainless steel is stable when cut into active materials and electrolytes.

However, the charge/discharge reversibility of such a secondary battery using stainless steel for 15 minutes of current collection is lower than expected.

Considering these circumstances, we have conducted various studies and found that in a lithium organic secondary battery G in which lithium or lithium alloy is used as the negative electrode active material, lithium is charged on the stainless steel surface of the negative electrode current collector. It was discovered that when a silver coating is applied to the part that can be analyzed, the charge/discharge reversibility is dramatically improved, and the present invention was completed.

In the present invention, the negative electrode current collector refers to a negative electrode can, a current collecting network, a current collecting plate, a current collecting rod, a current collecting pipe, etc., regardless of its form.
This refers to something that acts as a current collector on the negative electrode side.

In the drawings below, 1. The present invention will now be explained in further detail.

Figure 1 shows a button-shaped lithium white T7 secondary battery. In the figure, 1 is a lithium alloy, 2 is a negative electrode can,
This 1'] pole case 2 is made of a nickel-stainless steel lathod plate, and its stainless steel surface is placed on the inside of the battery; γ1
1 has been done. 3 is a stainless steel 415 wire spot welded to the inner surface of the negative electrode can 2, and the lithium negative electrode
It is crimped onto the inner surface of the negative electrode can 2 via a current collecting network 3 of tobacco. Accordingly, in the battery, the negative electrode can 2 and the current collecting network 3
constitutes the f′i electrode current collector. 4 is titanium disulfide/+
11 things'i! The positive electrode is denoted by t, and 5 is a positive electrode can made of nickel-stainless steel (1-blank clad), and its stainless steel surface is placed inside the battery. 6 is a stainless steel current collection network spot welded to the inner surface of the positive electrode can 5, and 7 is a separator made by superimposing a microporous polypropylene film and a polypropylene nonwoven fabric, with the microporous polypropylene film side being rigid. The negative electrode 1 side is arranged on the negative electrode 1 side. 8 is a polypropylene annular gasket l-.

When this battery was discharged and then charged, lithium was exposed not only on the surface of the negative electrode 1 but also on the stainless steel surface between the part of the negative electrode can 2 where the current collecting network 3 was welded and the fitting part of the annular gasket 8. Electrodeposition is also carried out on part 2a. This electrodeposited lithium does not form a flat 111 plane and has a dendritic shape. When charging and discharging are repeated further, the lithium that maintains its original form gradually disappears, and finally the lithium J3 becomes a collection on the negative electrode side. r
The thin 3 and the 111 electric current 3 are connected to each other, and the electric current 41 is also applied to the t't +@1 of the black part.

According to the investigation by those who failed to decompose the battery, as the electrodeposited lithium comes into direct contact with the sunless surface, the charge/discharge ratio becomes rl, (and the charge/discharge characteristics become significantly 7. descend.

Based on such knowledge, the researchers have attempted to suppress the decline in charging reversibility by changing the compatibility of the stainless steel IFi surface with which the electrodeposited lithium of the negative electrode current collector can come into contact. As a result of extensive research, we have completed the present invention, which coats the surface of the spunless steel with silver plating as mentioned above.

In the present invention, the thickness of the silver plating may be 1 μm or more, and the button shape 11h as shown in the figure (,1,1'[
The electrode can 2 and the current collector net 3 on the negative electrode side are plated with silver, and in the case of a cylindrical battery, the 1'I pole flj, the 111 electrode on the negative electrode side, the negative electrode current collector rod, etc. are shaped like batteries! Accordingly, the portion where the electrodeposited lithium comes into contact with the f'l electrode 4-1 is plated.

In the battery of the present invention, the negative electrode active material C is lithium or a lithium alloy of lithium and, for example, aluminum, mercury, zinc, cadmium, etc., and the positive electrode active material is, for example, titanium sulfide, iron disulfide, Iron sulfides such as ferrous sulfide and ferric sulfide, manganese dioxide, (CF
), fluorocarbons such as (C2F)χ, niobium disulfide, ■6013, Cu5 V20H, etc. are used.

In addition, examples of electric power include 1,2-dimethoxyethane, 1,2-jethoxyethane, pyrene carbonate, γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-thioxolane, 4-pyrene carbonate, Methyl-1,3-dioxolane, 4,4-dimethyl-1,3-dioxolane, 4,5-dimethyl-1
, 3-dioxolane, 2-methyl-1,3-dioxolane, 2,4-dimethyl-1,3-dioxolane, (CH
30)3 P=O1(C21-150)3 P=0, (
C4HsO)3P-0, (CsH170)3
P=O, (CI CH2C1120) 3 I2i CI
04, LiPl'6, LiBF4, LiA SF6
, Li5bl'6 , Li Δ ICI4, LiB1
゜CI 10, L i 1312 CI 12, L
i H(C61(5) 4, LiB(p-FCs 1
14) An electrolyte with a /8 resolution such as 3 CH3 and LiB (p-FC6H4)4 is used.

Next, the present invention will be explained with reference to Examples.

Example 1 Li B CC6Its > 4 as an electrolyte
A mixed solvent of methyl-1,3-dioxolane and 1,2-dimethoxyethane with a volume ratio of 70:30 (1,f
The cycle characteristics were evaluated by examining the number of cycles of charging and discharging to a positive electrode utilization rate of 0% or more in a button type battery as shown in FIG. The results are shown in Table 1. Seikle test 1. (The test was carried out at a constant current of 1 mA/cnl between discharge 1.5 V and charge 7ii 2.7'V.

The negative electrode can is Ninogel 5US304 clad plate, L-shaped, negative electrode side 0 doors 1', 71i tli:I is 5LJS
Made of 316 + 7) ``l' tQl + I'd te,
These ('1-electrode inner surfaces O,)-H(-electrophase 1 were plated with I)J to a thickness of approximately 10 μm.
2.1 L:1 This is an enlarged view of part A in Figure 1, and in Figure 2,
Reference numeral 9 indicates silver plating 1n formed on the inner surface of the fI pole can 2. As described above, the battery configuration was such that the negative electrode was lithium, the positive electrode was a titanium disulfide mixture with titanium disulfide as the positive electrode active material, and the separator was a layered layer of a microporous polypropylene film and a polypropylene nonwoven fabric. The separator was made of microporous polypropylene film and was placed facing the negative electrode.

Comparative Example 1 A battery similar to Example 1 except that the negative electrode can and the current collection network were not silver-plated, with a positive electrode utilization rate of 30%.
The number of charge/discharge cycles is l! jl solid. The results are shown in Table 1.

Example 2 Using lithium for the negative electrode and a titanium disulfide mixture for the positive electrode, the lithium was crimped onto a plain weave mesh made of 5US316, and the titanium disulfide mixture was held in the same 4p electrical order as on the negative electrode side.
A negative electrode current collecting pipe manufactured by No. 3 (14) was used as a core frame and wound into a spiral shape to form a spiral electrode, and using this, a cylindrical lithium-containing iJl secondary electric current tI!! was made of bamboo.

The electrolyte solution and separator were the same as in Example 1, and the positive electrode was covered with a separator to isolate it from the negative electrode.

In order to form the battery, silver agate with a length of about 10.1 m was placed in advance on the negative electrode side current collection network and negative electrode current collection pipe at 17°C.

Table 2 shows the results of examining the number of positive charge/discharge cycles of this battery.

Comparative example 2 Negative electrode side collection? li 11? 1 with + and 1. A cylindrical lithium battery was formed in the same manner as in Example 2, except that silver agate was not used for the electrode current collecting pipe, and the number of charge/discharge cycles at a positive electrode utilization rate of 30% or more was examined. The results are shown in Table 2.

As shown in Tables 1 and 2, the battery of the present invention has a large number of cycles and has poor charge/discharge characteristics.

The relationship between the number of cycles and the charge/discharge ratio of the battery of Example 1 and the battery of Comparative Example 1 is shown in the 31st page, and the relationship between the number of cycles and the charge/discharge ratio of the battery of Example 20) and the battery of Comparative Example 2, ! Figure 4 shows the relationship between the number of cycles and the charge 1jk electrification. In addition, the charge/discharge ratio and ε: 11・1゛) for charging electricity (TTIΔh) charge/discharge ratio −・−m=−□−−−−−−−−−−−−−−−
-One discharge electricity Ii (mΔh) It is the ratio between the amount of electricity released in each cycle and the charging electricity meter, and the closer the charge/discharge IL is to 1, the better the charge/discharge 'l'f!l is. show.

As shown in the 31st page 1 and the 41st page 1, the battery of the present invention has a small increase in the charging/discharging ratio due to an increase in the number of cycles of 11 to 1, and the charge/discharge ratio is small. 1 is good! It is IT.

[Brief explanation of the drawing]

Figure 1 shows an example of a phosphorescent type lithium-ion battery according to the present invention.
G:1 This is an enlarged view of the Δ section in Figure 1. Part 31 is a diagram showing the relationship between the number of cycles and the charging IJk current ratio of the battery of Example 1 of Example 1 of the present invention and the battery of Example 1 of Comparative Example 1.
The figure is a diagram showing the relationship between the battery of Example 2 of the present invention and the 7-hour battery life of Example 2 and the charge/discharge ratio. 1.Negative electrode, 2..Negative electrode can, 3..Negative electrode side current collector 1
12+, 9...♀艮め、Ki 1 line Yoshi 1m Undershirt 2 figure

Claims (1)

[Claims] (1) Lithium organic secondary batteries that use lithium or lithium alloy as the negative electrode active material! : 几1te, f'! A lithium organic secondary/battery characterized by silver plating on the stainless steel surface of the electrode current collector where lithium can be deposited.