JPS60207258A - Secondary battery - Google Patents

Abstract

PURPOSE:To achieve increased charge-and-discharge coulomb efficiency of a secondary battery, having electrodes to which solutions are supplied, without causing any side reaction by using an acid halogen solution of iron, copper, tin, nickel or a halogen as electrolyte of the positive and the negative active materials. CONSTITUTION:A secondary battery is constituted of an electrolytic cell 1 consisting of liquid-transmitting positive and negative electrodes 2 and 3 and bipolar partition plates 4, diaphragms 5 each installed between two adjacent positive and negative electrodes 2 and 3, an anolyte and a catholyte line 6 and 7 and liquid supply pumps 10 and 11 for supplying anolyte and catholyte to the positive and the negative electrodes 2 and 3 respectively, and tanks 8 and 9 in which the above anolyte and catholyte are stored. In this battery, when an acid halide solution of iron, copper, nickel or a halide is used as a positive or a negative active material, no side reaction occurs during positive and negative reactions. Therefore, high charge-and-discharge coulomb efficiency of the battery is achieved. Particularly in a zinc-halogen battery, any dentrite does not occur.

Description

[Detailed description of the invention] It relates to secondary batteries using electrodes.

Zinc is mainly used as the negative electrode active material of secondary batteries that use halogen as the positive electrode active material. Zinc-bromine batteries and zinc-chlorine batteries are examples of this, and by having a large electrode potential on the zinc side and a large electrode potential on the halogen side, it is possible to obtain an electromotive force greater than 1V in a single cell. However, these batteries have a major defect in that dendrites (zinc whisker-like crystals) are generated during charging, which tends to cause cell short circuits.To suppress the formation of dendrites, surfactants and other substances are used. A method of adding additives has been developed, but this poses a problem.On the other hand, batteries that use hydrochloric acid as the active material solution, such as chromium-iron batteries, have problems with the electrode reaction of chromium. There is a side reaction that generates hydrogen during charging, and the use of a catalyst must be taken into account from a kinetic point of view.Additionally, it has the disadvantage of being prone to self-discharge.These factors reduce the charging and discharging efficiency.
In addition, we have solved the drawbacks of single-iron batteries, etc., which are the cause of increased manufacturing costs. After storing in the positive and negative electrolyte tanks,
The secondary battery that is recycled to the electrolytic cell is characterized in that a halogen acidic solution of iron, copper, tin, nickel, or halogen is used as the electrolytic solution for the positive and negative electrode active materials.

The configuration of the present invention will first be explained by taking an iron-chlorine battery as an example. In this case, the positive electrode reaction of the battery is (1°+2e--2
CJ″″, the negative electrode reaction is Fe(If)−=Fe(III
) becomes +e-. The electrolytic solution, which is a battery active material, is a hydrochloric acid acidic iron chloride aqueous solution, which is common to both electrodes, and can be obtained as an electrolytic solution in a discharged state by dissolving ferrous salt or metallic iron in hydrochloric acid. The solution after charging this battery is chlorine water on the positive electrode side, and ferric iron solution on the negative electrode side: When storing high concentration chlorine on the positive electrode side, the temperature should be kept below 15 degrees Celsius to avoid corrosion. The temperature is more preferably 5°C or lower.

FIG. 1 shows a typical example of the device configuration of a secondary battery according to the present invention. An electrolytic cell (battery main body) consisting of an electrolytic cell (battery body) 4 (if installed in a terminal plate), a diaphragm 5 provided between the positive electrode 2 and the negative electrode 3, and a positive electrode liquid that supplies electrode liquid to the positive electrode 2 and negative electrode 3, respectively. line 6, negative electrode liquid line 7, and liquid pump 10.
11, and tanks 8 and 9 for storing the positive and negative electrode liquids.

In the above configuration, taking an iron-chlorine battery as an example,
In the charged state, an aqueous solution of divalent iron ions (Fe") and chlorine water (CJ2) are stored in separate tanks 9 and 8, respectively. When these are flowed into the flow-through electrolytic cell 10, chlorine molecules become electrons at the positive electrode 2. It receives two ions and becomes chlorine ion Cj!−, and the negative electrode 2″e is p e2+ which loses one electron and becomes trivalent F
It becomes e12. The electrons exchanged between the negative electrode 2 and the positive electrode 3 perform work through an external circuit, for example, and emit power. The electrolytic cell body 1 that performs charge/discharge reactions has, especially on the positive electrode side,
Since chlorine is generated, the bipolar partition plate, electrodes, and diaphragm must all be constructed of materials with high chlorine resistance.

According to the above battery, the following effects are achieved.

(1) The negative electrode reaction uses divalent iron, which has an extremely high reaction rate.
Since this is a trivalent electrode reaction, battery design and manufacture are easy.

(2) There are no side reactions in both the positive and negative electrode reactions, so the charge/discharge coulombic efficiency of the battery is high (zinc-based batteries have a side reaction of hydrogen generation).

(3) Both the positive and negative electrodes use solution flow type electrodes, and when a battery reaction is not performed, the entire active material liquid is dropped from the cell into a tank and stored. Therefore, there is no self-discharge.

(4) For zinc-halogen batteries, there is no problem of dendrite formation. In addition, for chromium-halogen batteries, the electrode reaction of chromium (Cr(II)-Cr(I[
) +e-) worsens (electrode reaction rate decreases)
there is no problem.

Most of the above advantages also apply to copper, tin, nickel, and halogen versus halogen batteries. The main positive electrode reactions and negative electrode reactions of these batteries are shown in the table below.

The active material solution of the present battery is not limited to an aqueous solution, and may be carbon tetrachloride, a protic or aprotic polar solvent, etc. without any particular problem in terms of the structure. Further, the halogen referred to in the present invention may be selected from fluorine, chlorine, bromine, and iodine, and this is determined by taking into consideration electromotive force and the like.

In addition, secondary batteries that use halogen acid halide solutions of iron, copper, tin, halogen, and nickel as positive and negative electrode active materials,
For example, in a secondary battery using a hydrochloric acid acidic iron chloride solution, an electromotive force of only about 0.6 V can be obtained, but this can be solved by increasing the number of cells stacked in series. The cells used in the present invention are extremely inexpensive, have a simple structure, and are easy to stack, so a reduction in the electromotive force of a single cell is not a problem.

(Background of the Invention) As described above, according to the present invention, by selecting a halogen acidic solution of a specific element and an electrolyte of positive and negative electrode active materials,
A secondary battery having no side reactions and high charge/discharge coulombic efficiency can be provided.

(Examples of the Invention) Example 1 A charging/discharging experiment was conducted using a battery shown in FIG. 1 using a 6N hydrochloric acid acidic 2 mol/l ferrous chloride aqueous solution.

The electrolytic cell body was composed of a bipolar partition plate made of a sheet of PVC-bound carbon powder, a liquid-permeable electrode made of pitch-based carbon fiber felt, and a diaphragm made of a porous PVC membrane, and 30 cells were stacked in series.

The results of a charge/discharge test at an operating electrolytic cell temperature of 15° C. were as follows.

Depth of charge of negative electrode liquid (FeII/Fe1II ratio) Charging/discharging coulombic efficiency based on 95% Average voltage efficiency 76% (Current density 30 mA/cIA) Average discharge voltage 0.65 V Example 2 6N Hydrochloric acid acidity 2 mol/l chloride Cupric aqueous solution, about 12 N hydrochloric acid acidic 2 mol/! Stannous chloride aqueous solution, 6N hydrochloric acid acidic 2 mol/β nickel chloride aqueous solution, 6N hydrochloric acid acidic 1
A similar study was conducted using the apparatus in Example 1 using a mol/l aqueous iodine solution as the electrolyte. The results are shown in Table 2.

Table 2 Examples 1 and 2 both have a Coulombic efficiency of 95% as the upper limit.The second reason is that the loss due to shunt current in the electrolytic cell body (loss due to leakage current flowing through the liquid feed pipe to each electrode chamber) is 5%.
A value of 95% indicates that there is no loss due to side reactions or self-discharge.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a secondary battery showing a typical embodiment of the present invention. 1... Electrolytic cell (battery body), 2... Positive electrode (liquid permeable electrode), 3... Negative electrode (liquid permeable electrode), 4... Multipolar partition plate or terminal plate, 5... - Diaphragm, 6... Positive electrode liquid line, 7... Negative electrode liquid line, 8... Positive electrode liquid tank, 9... Negative electrode liquid tank, 10.11... Liquid sending pump. Agent Patent Attorney Takenaga Kawakita

Claims (1)

[Claims] (1) Electrolytic cell with i9 liquid flow type electrodes on the positive and negative electrodes (
After flowing the electrolyte through the battery body and storing the electrolyte after charging and discharging in the positive and negative electrolyte tanks,
In the secondary battery to be recycled to the electrolytic cell, a halogen acidic solution of iron, copper, tin, nickel or halogen -
A secondary battery characterized in that the electrolyte of the positive and negative electrode active materials is used as an electrolyte.