JPH0255910B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to electrolytes for various types of primary or secondary batteries. [Prior Art] Aiming at improving power supplies, many studies have been conducted to improve the performance, particularly the size, weight, and capacity of various primary and secondary batteries. these are,
It is mainly applied in the fields of hearing aids, space and satellite equipment, and electric non-hazardous vehicles. During this time, of course, the electrolytes used in such batteries were also studied. The factor of interest here is the current conductivity, which has a capacity-damping effect on the electrodes and other battery components. This factor varies with electrolyte concentration, temperature, electrode solubility and additives. Other considerations are the rate of charge transfer due to chemical reactions, the formation of dendrites in many rechargeable batteries, deterioration of the electrode structure,
The problem is a decrease in capacity and therefore a shortened service life. Various additives have been tested in different types of electrochemical cells, and inorganic or organic additives sometimes used in the electroplating industry have been shown to inhibit dendrite formation, improve charge transfer, reduce internal resistance, Or tested to improve the performance and lifespan of general batteries. References include the following: U.S. Patent No. 4074028 (Will Corporation February 14, 1987)
"Dendrite-Suppressing Electrolyte and Rechargeable Aqueous Zinc-Halogen Battery Filled with the Electrolyte" U.S. Pat. No. 3,466,195 (Spellman ESB, 1969)
September 9, 2013) “Addition of silicate ions to electrolytes” U.S. Patent No. 3,433,679 (Spellman F&B, Inc.)
March 18, 1969) “Lithium ions added to electrolyte” U.S. Patent No. 3658593 (Caiola Soc.Acc. France April 25, 1972) “Tetrabutylammonium chloride of propylene carbonate” U.S. Patent No. 3540935 Keating Nutt EI
Pont November 17, 1970) “Addition of Sodium Cyanide to Prevent Dendrites” U.S. Patent No. 3716412 (Peters ESB Ltd.U.
K. February 16, 1973) "Amorphous Silica for Acidic Electrolytes" U.S. Patent No. 3,669,743 (Swindells Melpar 1972)
(June 13, 2015) "Solid Zinc Salt Composite Electrolyte" Additives can also be added to the electrode structure to help reduce capacity loss and electrode deterioration effects, or even improve electrolyte penetration into the electrode structure. , attempts were made to make effective use of available materials. Most modifiers and additives used and proposed to date oxidize, are incompatible, react irreversibly with electrodes and other battery components, or dissipate, reducing their effectiveness. Because of this, sufficient stability over a long period of time could not be obtained during continuous repeated use in electrochemical cells. [Means for Solving the Problems] The present invention provides an electrolytic solution for primary or secondary batteries, regardless of whether cyanide or ferricyanide is used in the electrode material of these batteries.
The above problem was solved by including potassium or sodium ferrocyanide or ferricyanide as an additive that increases the electrical conductivity and reduces the solubility of the electrode. These ferrocyanides include hexacyanoferrate () (Fe(CN) ₆ ^4- ₎ ^;
It is included. The electrolytic solution according to the present invention can be prepared, for example, as follows. First, the concentration is 1.12 at 20℃.
Prepare 13% by weight potassium hydroxide (KOH) g/ml (2.6 molar concentration) and add potassium ferricyanide ( _K3Fe (CN) ₆ ) to it until a concentration of 1.14-1.2 g/ml is obtained. . Or in distilled water
15g KOH granules (KOH85%) and 4g potassium ferricyanide ( _K3Fe (CN) ₆ ) per 100ml
may be understood as This absolute ratio is not particularly critical, and in many cases, even the addition of very small amounts of potassium ferricyanide to the electrolytes of various conventional cells will significantly improve performance. The concentration of electrolyte used in various types of batteries is
They vary widely and are selected to suit the particular operating temperature and conditions and battery components and electrodes. Selection criteria for the use of electrolytes or additives in accordance with the present invention may likewise be varied by the manufacturer depending on the intended use and conditions of use, and may deviate from the desirable ranges provided as a guideline herein. There will be. [Effect] Chemical reactions during charging and discharging of various electrochemical batteries are not fully understood, and many competing reaction systems are often involved. It is not critical for those skilled in the electrochemical cell art to fully understand all of the reactions involved in using the present invention. The description of the operation described below is conceptual. The electrolyte according to the invention is particularly suitable for silver-zinc (Ag-zinc)
Used in rechargeable batteries such as Zn) batteries, nickel-cadmium (Ni-Cd) batteries, nickel-zinc (Ni-Zn) batteries, nickel-iron (Ni-Fe) batteries, and lead oxide (PbO) batteries. It has many effects, but it is also effective for other batteries. The main reason for this is that the electrolytic solution according to the present invention has a higher ion concentration and a higher charge transfer rate than a normal electrolytic solution containing only KOH due to the presence of hexacyanoferrate (Fe(CN) ₆ ) ions. it is conceivable that. Therefore, the internal resistance of the battery is reduced and the conductivity is improved. Also, for the same reason, the electrochemical capacity of the electrodes and therefore the electrode materials are utilized more effectively than before, improving the output voltage, storage capacity and efficiency of the battery. In addition, the electrolyte
By adding Fe(CN) ₆ ions, the ion concentration is higher than before, even at low temperatures, and the charge transfer rate is increased. Therefore, the low temperature performance of the battery is improved. Furthermore, due to the presence of Fe(CN) ₆ ions,
For example, the solubility of zinc (Zn ⁺⁺ ) ions and cadmium (Cd ⁺⁺ ) ions in the electrolyte is significantly reduced. Thus, in rechargeable batteries, dendrite formation is suppressed by reducing electrode solubility and changing electrode conditions. Additionally, in silver-zinc batteries, battery deterioration due to migration of silver ions to the zinc electrode is greatly reduced, and the reuse life can be significantly extended without relying on special separators. The number 260 cycles shown in the experimental data described below is
This is extremely long compared to the cycle life of conventional silver-zinc batteries. The electrolytic solution according to the invention is characterized in that it contains potassium or sodium ferrocyanide or ferricyanide, regardless of whether cyanide or ferricyanide is used in the electrode material, and is suitable for use in electrochemical cells (primary or secondary battery)
It can be used as an electrolyte in the form of a solution or as an additive in the form of a solution or salt to an electrolyte. Metal (Fe) contained in the electrolyte of the present invention
The bond retains (CN) ₆ , and as mentioned above, the Fe(CN) ₆ complex, which is involved in charging and discharging, does not disappear even after repeated use. Particularly in the case of rechargeable batteries with zinc electrodes, it is advantageous to add a small amount of a suitable fluoride NaF or KF and to saturate the electrolyte with zincate ZnO, as described below. [Effects of the Invention] The effects of the present invention are as described above, and they can be summarized as follows. (1) The internal resistance of the battery decreases. (2) Better performance at low temperatures. (3) Battery output voltage increases. (4) Efficiency is improved. (5) Improved utilization of electrode materials. (6) Suppress the formation of dendrites. (7) Battery life is extended. Although these effects exist to a greater or lesser extent in all of the embodiments of the present invention described below, they will not be individually described again in each embodiment. [Example] 1. For a conventional silver-zinc (Ag-Zn) type pre-charged dry storage battery, a concentration of 1.14 g/ml of potassium hydroxide (KOH) is obtained at 20°C with a concentration of 1.12 g/ml. The electrolytic solution of the present invention to which potassium ferricyanide (K ₃ Fe(CN) ₆ ) was added was used up to the point in time. 4 commercially available Ag-Zn with nominal capacity 2Ah
On the other hand, Table 1 shows the results of measuring the actual capacity and repeatedly performing rapid discharge using the conventional electrolytic solution and the electrolytic solution of the present invention.

Table 2 In a conventional nickel-cadmium (Ni-Cd) type battery, the electrolyte of the present invention prepared as in Example 1 above was used in place of the conventional electrolyte of KOH or NaOH. This cell also exhibited improved characteristics and power levels over conventional cells. Other improvements will depend on the specific construction of the electrode and cell. Commercially available Ni-Cd pocket exhaust type batteries and Ni-
Table 2 shows the results of a comparative test using a Cd sintered exhaust type battery.

【table】

[Table] 3 Ordinary nickel-iron (Ni-Fe) batteries also
Improvements were likewise made with the use of the electrolyte of the invention. 4. Batteries of the metal-air type, preferably of the zinc-air type, have likewise been improved by the use of the electrolytes of the present invention. 5 Nickel-zinc (Ni-Zn) type batteries were similarly improved by the use of the electrolyte of the present invention. 6. The electrolyte of a rechargeable battery of the nickel-zinc (Ni-Zn) type using the electrolyte according to the invention includes:
zincate _{ZnO ,} highly fluoride KF or _NaF and _{Na2B4O7 , K3BO3} or orthoboric acid _H3BO3
Boron was added in the form of In this example, the electrolytic solution of the present invention was used in a conventionally configured nickel-zinc (Ni-Zn) battery. This electrolyte had a concentration of 1.12 g/ml as in the above example.
It was prepared by adding potassium ferricyanide to a KOH solution to a concentration of 1.14 to 1.18 g/ml. If the electrodes are based on zinc in rechargeable batteries, small amounts of potassium fluoride KF or sodium fluoride NaF and forms such as Na ₂ B ₄ O ₇ , K ₃ BO ₂ or orthoboric acid H ₃ BO ₃ Adding boron and zincate to the electrolyte to further suppress the solubility of the zinc electrode
It was found that saturation with ZnO is beneficial. The electrolyte according to the present invention has a concentration as described above.
Concentration of about 1.14 to 1.12g/ml potassium hydroxide KOH
It is made by adding potassium ferricyanide (K ₃ Fe(CN) ₆ ) to increase the concentration to ~1.2 g/ml. The absolute ratio is by no means critical since even very small amounts (K ₃ Fe(CN) ₆ ) added to the electrolyte are sufficient to significantly improve performance. The electrolyte according to the invention is not limited in any way to its use in the above embodiments, but can also be used with other electrode devices and additives. Such additives are often used to alter electrode conductivity, overpotential, or reduce gassing, self-discharge, etc., to name a few examples: graphitic carbon. , Ni, Pb, Mn, V, Ti, Zr,
There are Hf, Nb, Hg, etc. When using the electrolyte according to the invention, it is advantageous to add some such additives in the form of cyanides or ferricyanides, such as potassium cyanomercurate (K ₂ Hg(CN) ₄ ). Although the essence, preferred embodiments, and various advantages and effects of the present invention have been described above, the present invention should not be construed to be limited to the specific embodiments described or disclosed herein. These are merely illustrative rather than restrictive. The present invention can be modified and changed in various ways by those skilled in the art without departing from the spirit thereof.

Claims (1)

[Claims] 1. In an electrolytic solution for a primary battery or a secondary battery,
An electrolytic solution characterized by containing potassium or sodium ferrocyanide or ferricyanide. 2. The electrolytic solution according to claim 1, which contains a fluoride. 3. The electrolytic solution according to claim 1 or 2, to which a borate or orthoborate is added. 4. The electrolytic solution according to claims 1 to 3, which contains an oxide or hydroxide of a battery electrode material.