JPS63259976A - Electrically chargeable electrochemical device - Google Patents

Abstract

PURPOSE:To extremely enhance the high temperature charge/discharge characteristics of the device in the caption by employing a nonaqueous solvent containing ethoxymethoxyethane as an electrolyte. CONSTITUTION:gamma-butyrolactone (gamma-BL), ethoxymethoxyethane (EME) and gamma-BL, 1-butylene carbonate (BC) EME etc. can be used as a solvent for electrolyte. Further, all of the solvent materials applicable to a lithium cell such as LiClO4, LiAsF6, LiPF6 etc., besides LiBF4 can be employed as a solvent material for electrolyte.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a rechargeable electrochemical device used as a mobile DC power source, a backup power source, or the like.

Conventional technology As a rechargeable electrochemical device, activated carbon mainly uses an electric double layer for the positive electrode, and lithium alloy for the negative electrode.

Devices using a non-aqueous organic solvent as an electrolyte are known. The electrolyte in this device includes propylene carbonate (hereinafter referred to as PC) and T-butyrolactone (hereinafter referred to as γ
Furthermore, lithium borofluoride (LiBF4) or lithium perchlorate (LiC
A solution containing a solute such as 1O4) was used.

Problems to be Solved by the Invention In this conventional configuration, PC has relatively excellent charge/discharge cycle characteristics, γ-BL has excellent overdischarge resistance characteristics, and DME
has low viscosity and has the effect of improving the fluidity of the electrolyte and improving the load characteristics. B
A three-component mixed solvent of L and DME was used. However, even if such an electrolytic solution is used, it is not necessarily sufficient, and there are still points to be improved, such as long-term charging/discharging characteristics and temperature characteristics. One of the reasons for this is that DME is not necessarily stable and is easily decomposed, perhaps because its boiling point is as low as 85.2°C during high-temperature charging and discharging at temperatures above 60°C.
It had a negative impact on lifespan.

Means for Solving the Interstitial Point In order to improve the charging and discharging characteristics of devices using the above-mentioned lithium negative electrode, especially devices using activated carbon as the positive electrode, the present invention uses an electrolyte instead of conventional DME. There is also one that uses a nonaqueous solvent containing ethoxy methoxy ethane (hereinafter referred to as EME).

Effect Table 1 shows the physical properties of each solvent. DME is characterized by its low viscosity, and is effective in facilitating the work of impregnating separators with electrolyte and in heavy-load discharge, but as mentioned above, its boiling point is lower than that of PC, γ-BL, etc. There was a drawback.

However, the EME of the present invention has a boiling point of 104°C, which is higher than that of DME.
The temperature is nearly 2oC high, and the viscosity is 0.47/CPS.
(3o℃), which is rather lower than DME.

Therefore, it is expected that the high-temperature characteristics will be improved without causing problems in workability or heavy-load discharge as described above.

From this, γ-BL is suitable as a solvent for electrolyte solution.

EME system, γ-BL, PC, EME system, r-BI,
B.C.

After examining EME systems, it was found that high-temperature charge/discharge characteristics were significantly improved.

Table 1 Examples FIG. 1 shows a rechargeable electrochemical device using activated carbon as a positive electrode, a lithium alloy as a negative electrode, and an electrolytic solution consisting of a non-aqueous solvent. In the figure, 1 is a case that also serves as a positive electrode terminal, 2 is a sealing plate that is punched from the same material as the case and serves as a negative terminal, 3 is a polypropylene gasket that insulates the case and the sealing plate, and 4 is a positive electrode. After kneading 70 parts by weight of activated carbon powder, 10 parts by weight of acetylene black as a conductive material, and 20 parts by weight of an aqueous dispersion (relative solid content) of fluororesin as a binder (solid content: 60 parts by weight) and forming into a sheet. , which was transferred onto a titanium lath plate with a thickness of 0.2 m, which forms the current collector 6.

After that, after drying in a high temperature vacuum, the thickness was adjusted to 0.7+III+, punched into pellets with a diameter of 14.0 m, a part of the mixture was peeled off to expose the titanium lath plate, and this was made into case 2.
Welded to. 6 is a lithium storage negative electrode alloy, which consists of 20 parts by weight of bismuth, 60 parts by weight of lead, 27 parts by weight of cadmium, and 3 parts by weight of lithium, and has a thickness of 0.1 m and a diameter of 15.
97 is a negative electrode current collector;
A stainless steel net with a wire diameter of 0.1 mm and 60 meshes was used. 8 is a separator made of polypropylene nonwoven fabric.

The electrolytic solution used was one in which the solvent was adjusted as shown in Table 2, and 1 mol/l of lithium fluoroborate was dissolved therein as a solute.

Table 2 Using these devices, charging and discharging tests were conducted at room temperature and 60° C. under the charging and discharging conditions shown below.

In the initial cycle, when the time taken for the voltage to reach 2v from 3v is set as 100, the time taken for the voltage to reach 2v in each cycle was calculated, and the charge/discharge cycle life was compared. The results are shown in FIGS. 2 and 3.

As is clear from FIG. 2, γ-BL of A-4.

Conventional products using PC and DME deteriorate between 2000 and 3000 cycles, but series A-1 to A-3 using EME are all superior to the conventional products, especially P C + B C The one with the in it is better.

Furthermore, in the 60° C. atmosphere shown in FIG. 3, the conventional product A-4 deteriorates quickly, while A-1 to A-3 are relatively stable even after 200 o cycles. From these facts, it can be seen that EXE is superior to DME, and is particularly effective in high temperature regions. And, regarding the charge/discharge cycle life, PC and BC
It can also be seen from the comparison of A-1 to A-3 in FIG. 2 that this is effective.

Furthermore, after charging to 3V using these devices, 5~
A heavy load discharge was carried out and the instantaneous voltage drop of each device was investigated, but all were about 200 mV, with almost no difference. From this, EME is not inferior to DME in any way even in heavy load discharge characteristics.

In addition, as an example, bismuth, lead,
Although a cadmium alloy was used, any alloy capable of charging and discharging lithium, including an At alloy, can be used.

In addition, as a solute of the electrolyte, in addition to L I B F 4,
All possible solutes suitable for lithium batteries can be used, such as LiCl0 LiAsF LiPF6.

Effects of the Invention As is clear from the above, the present invention provides an organic electrolyte-based chargeable/dischargeable electrochemical device that uses activated carbon as a positive electrode and a lithium alloy as a negative electrode, and improves charging/discharging characteristics at room temperature and especially in a high-temperature atmosphere. Demonstrates excellent effects.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a chargeable/dischargeable electrochemical device according to an embodiment of the present invention, and FIGS. 2 and 3 are characteristic comparison diagrams of the devices according to an embodiment of the present invention. 1... Case, 2... Sealing plate, 3...
...Gasket, 4...Positive electrode, 6...
...Positive electrode current collector, e...Negative electrode, 7...
- Negative electrode current collector, 8...Separator. Name of agent: Patent attorney Toshio Nakao and 1 other person f-
--Case 2-Strike I] Obscene 3--Ichiriki°Sugat 1 C-@Earth 7--- # Certain/Itj Book Figure 2

Claims (1)

[Scope of Claims] (1) An electrochemical device comprising a positive electrode made of activated carbon, a negative electrode made of a lithium alloy, and an electrolytic solution made of a nonaqueous solvent, the electrolytic solution containing ethoxy, methoxy, and ethane. A rechargeable electrochemical device comprising: (2) The rechargeable electrochemical device according to claim 1, wherein the electrolytic solution consists of a mixed solvent of γ-butyrolactone and ethoxy-methoxy-ethane. (2) The rechargeable electrochemical device according to claim 1, wherein the electrolytic solution consists of a mixed solvent of γ-butyrolactone, propylene carbonate, and ethoxy-methoxy-ethane. (4) The rechargeable electrochemical device according to claim 1, wherein the electrolytic solution consists of a mixed solvent of γ-butyrolactone, 1-butylene carbonate, ethoxy/methoxy, and ethane.