JPS6079670A - Negative electrode for lithium battery - Google Patents

Abstract

PURPOSE:To improve charge-discharge performance of a lithium battery by using alloy of lithium with at least one of Pt, Ni, Pd in the VIII group of the prriodic tabel as a negative electrode. CONSTITUTION:An alloy of lithium with at least one of Pt, Ni, Pd is used as a negative electrode in lithium primary and secondary battery. Since Pt, Ni, and Pd belong to the VIII group of the periodic table, two electrons whose energy level is lower than that of electron in the outermost S orbit do not exist its structure. By using this lithium alloy, deposition of lithium becomes smooth, and reaction activity with organic solvent is reduced, and charge-discharge efficiency of negative electrode is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a lithium negative electrode for use in lithium batteries.

Batteries using lithium as a negative electrode active material are being researched as small-sized batteries with high energy density, but secondaryization has become a major problem.

Many compounds have been investigated as positive electrode active materials that can be secondaryized. For example, batteries using sulfides, selenides, and tellurides of titanium, zirconium, hafnium, niobium, tantalum, and vanadium (U.S. Pat. No. 408
9052) etc. have been disclosed.

However, compared to such research on positive electrode active materials for secondary batteries, research on the charging and discharging characteristics of Li electrodes is not sufficient, and in order to realize lithium secondary batteries, charging and discharging efficiency, cycle life, etc. The production of lithium electrodes with good thermal properties has become a serious problem.

In an attempt to improve the charging and discharging characteristics of lj electrodes, there have been attempts to use lithium treated with gases such as op, co2, etc. for negative four (J, EIelectrochem, Soc,
, Vol. 125, pp. 1371-1377] and Li
An attempt to use the alloy of 81 and 81 as a negative electrode (J, EIect
rochem, Soc, , Vol. 127 No. 210
[pp. 0-2104] have been carried out, but they are not necessarily sufficient, and efforts are being made to produce Li negative electrodes with even better characteristics.

The present invention has been made in consideration of the current situation, and
The purpose is to provide a lithium negative electrode with excellent discharge and charge characteristics.

To summarize the present invention, the negative electrode active material is lithium, the positive electrode active material is a material that undergoes a reversible electrochemical reaction with lithium ions, the electrolyte material is chemically stable with respect to the positive electrode material and lithium, In addition, an alloy of lithium and one or more of Pt, Ni, or Pd is used as a negative electrode used in lithium-primary and secondary batteries, which is a material in which lithium ions move to perform an electrochemical reaction with a positive electrode active material. It is characterized by the fact that it was used.

By using the negative electrode for a lithium battery according to the present invention, there is an advantage that a lithium battery with excellent charge and discharge characteristics can be manufactured.゛The present invention will be explained in more detail.

The above-mentioned Pt, Ni, Pd, belong to group metals, and the outermost S
There is a shortage of 2IlliI electrons below the energy level below the orbit.

Generally, a lithium metal plate is often used as a lithium negative electrode, but in this case, when the discharging or charging current increases, holes are formed in the lithium negative electrode due to local reaction acceleration, and tentrite-shaped lithium is deposited during charging. This causes phenomena such as falling off from the negative electrode. In addition, lithium has a high electron-donating property and has the disadvantage of reductively decomposing organic solvents. These are the causes of lowering the charging and discharging efficiency of the lithium electrode.

Therefore, the purpose is to smooth the precipitation form of lithium, lower the reaction activity with the organic solvent, and improve the charging/discharging efficiency of the lithium negative electrode.

The method of alloying lithium is not fundamentally limited in the present invention. Any method may be used as long as lithium is alloyed with one or more of l'L, Ni, and Pd. For example, 1) a method for electrochemically attaching lithium to a group II metal in a solution containing Li'' ions, 2) a method for electrochemically attaching lithium to a group II metal in a molten salt, and 3) a method for electrochemically attaching lithium to a group II metal in a molten salt. Methods such as immersing the group ■ metal in a lithium metal melt, 4) causing 47i of lithium to be released from the group ■ metal with n-butyllithium, and 5) vapor depositing lithium on the group ■ metal can be used. .

In the examples below, lithium is electrochemically alloyed with Ni, Pt, or Pd in an organic solvent, and used as the negative electrode. This is not intended to limit the invention.

Example 1 Li slope (size 1 cIi!, thickness 0.2
5 Tsuru) as the positive electrode, and a PT plate (size 1 cJ, thickness 0
．． Assemble a battery using 05m1+), I M 1. i
c]0 to 1m in propylene carbonate/C
+a for 80 minutes to produce an Lj-Pt alloy. The electrochemical amount of Li in this alloy was 2.4 C/cTa.

Using the Li-Pt alloy prepared as described above as a working electrode,
Assemble a battery using Li as the negative electrode and Li as the reference electrode, and
A charging/discharging test was conducted on the i-P alloy. I M LiCIO4-propylene carbonate was used as the electrolyte.

First, the measurement was performed using a constant current of 0.5 mA/cJ.
- A cycle test was repeated in which a part of the L alloy (0.6 C/cJ) was discharged as L bioions and then further discharged at a capacity of 0.6 C10il. The average charge/discharge efficiency E per cycle is determined by the change in the potential of the Li--Pt electrode, and when the number of cycles showing an efficiency of 100% is repeated n times, E is fitted by equation f11.

Equation (1) The results are shown as 8 in Table 1 below. In addition, in Table 1,
B is a comparative example to show the effect of the present invention, and shows the results of a similar experiment using a Cu plate of the same thickness instead of a PT plate (Cu has a 1412 alloy. It has been reported that it is difficult to use (J, F, 1ectrocl+
em, soc, + 118 volumes + 1547 pages, 1971
Year)〕.

From Table 1 below, it can be seen that the use of Li--Pt alloy significantly improves the charging and discharging efficiency of Li.

Example 2 Example 1 except that Li-Ni was used as the Li alloy.
The charging and discharging efficiency of the Li-Ni alloy was measured in the same manner.

The results are shown as C in Table 1 below. It was found that the charge/discharge efficiency was significantly improved by using the Li-Ni alloy compared to the case where a Cu plate was used (B in Table 1).

Example 3 Same as Example 1 except that 1 mole/1 LiCIO4 dissolved in a 1:1 volume ratio mixed solvent of propylene carbonate and 1,2-dimethoxychne was used as the electrolyte. The charging and discharging efficiency of the Li-P L alloy was measured.

The results are shown as D in Table 1 below. For reference, the case where a Cu plate was used under the same conditions is shown as E.

As is clear from Table 1, by using an alloy for Li-P, the charge/discharge efficiency is significantly increased.

Example 4 Example 3 except that Li-Pd was used as the Li alloy.
The charging and discharging efficiency of the Li-Pd alloy was measured in the same manner.

The results are shown as F in Table 1 below.

Li-
By using a Pd alloy, the charging and discharging efficiency is significantly improved.

As is clear from the explanations in Table 1 and above, the present invention has the advantage that by using an alloy of lithium and N1, PT, or Pd, a lithium secondary battery with excellent charge and discharge characteristics can be realized. .

Applicant's representative: Masaki Ame Miya

Claims (1)

[Claims] ■ A lithium battery characterized by containing an alloy of lithium and one or more of Ni, Pd, and PT, which are metals lacking two electrons below the energy level of the outermost S orbit among flexible metals. negative electrode.