CN1366356A

CN1366356A - Liquid leakage prevention method of zinc-air battery

Info

Publication number: CN1366356A
Application number: CN01129823A
Authority: CN
Inventors: 周震涛; 周晓斌; 于东生
Original assignee: South China University of Technology SCUT
Current assignee: South China University of Technology SCUT
Priority date: 2001-10-30
Filing date: 2001-10-30
Publication date: 2002-08-28
Anticipated expiration: 2021-10-30
Also published as: CN1169238C

Abstract

A method for preventing leakage of zinc-air battery features that a water-absorbing resin layer is arranged at internal surface of battery case to absorb the leakage of battery and prevent the leakage of electrolyte from battery case, so greatly increasing the discharge current of battery and preventing the leakage of electrolyte from corroding and damaging its electric equipment.

Description

Liquid leakage prevention method of zinc-air battery

The invention relates to the field of electrochemistry, in particular to a liquid leakage prevention method for a zinc-air battery.

The zinc-air battery is a battery which takes zinc as a negative electrode active material and oxygen in the air as a positive electrode active material, the oxygen required by the battery can be continuously supplemented from the air after being consumed, and current is continuously generated, so that the battery can continuously and continuously work as long as sufficient negative electrode materials of zinc and electrolyte exist. Therefore, the battery has the remarkable characteristic of high specific energy which can reach 1350Wh/Kg theoretically. Taking a common alkaline zinc-air battery as an example, the reaction of the two electrodes and the battery is as follows:

negative electrode

Positive electrode

Cell reaction

Since zinc-air batteries rely in principle on the diffusion of oxygen from the air into the battery, the entire battery system cannot be designed as a closed system. The oxygen electrode is similar to the oxygen electrode in a fuel cell and mainly comprises a waterproof breathable layer, a conductive net and a catalytic layer. The waterproof and breathable layer is mainly made of hydrophobic materials, such as polytetrafluoroethylene, polyethylene and the like. A large number of capillary holes are formed therein, and when it comes into contact with the electrolyte, the liquid level inside the capillary holes takes on a meniscus shape due to the hydrophobicity of the material to generate an additional pressure directed to the inside of the liquid. This pressure prevents leakage of the internal liquid, but outside air can enter the cell's electrolyte through the capillary holes. The pressure is related to the pore size of the micropores of the air diffusion electrode, the contact angle of the electrolyte on the surface of the micropore inner wall material, the vapor pressure of the electrolyte and the like, and is the key of the battery sealing problem.

In fact, the main reason why zinc-air batteries have not been put into practical use and industrialized on a large scale for many years is that the key technical problems of alkali leakage, low discharge current density and the like have not been solved well. The former can lead the electrolyte leaked out of the battery shell of the zinc-air battery to corrode and damage equipment using the battery in the using process; the latter makes it only suitable for low-power electric equipment, and limits the range of battery use. Moreover, there is a congenital contradiction between the two: in order to prevent the alkali leakage of the battery, the effective method is to reduce the aperture of the micropores of the air diffusion electrode and the total area of the air diffusion channel, namely the total area of the micropores, but the diffusion speed of air entering the battery is reduced, so that the discharge current of the battery is reduced; on the contrary, it is an effective method to increase the discharge current of the zinc-air battery, increase the pore diameter of the micropores of the air diffusion electrode, and increase the total area of the micropores by increasing the air diffusion channel, but this will aggravate the alkali-leakage of the battery. This is a drawback of the zinc-air cell principle. For this reason, the research on zinc-air batteries in china and countries in the seventies has been hot, and the batteries have gradually cooled down after the eighties. In recent years, due to rapid development and update of portable electronic information products, higher requirements are put on technical indexes of batteries, so that the zinc-air battery with ultrahigh specific capacity is attracting the attention of many chemical and electric power research workers at home and abroad. Attempts have been made to find solutions in the fields of battery sealing structures, battery sealing materials, additives for electrolyte formulations, and the like, but fundamental breakthroughs have not yet been made.

The present invention is directed to a method for increasing the discharge current density of a zinc-air battery by increasing the pore diameter of micropores of an air diffusion electrode and the total area of air holes, and simultaneously, a method for preventing leakage of electrolyte inside the battery is adopted, wherein the method comprises the steps of structural design and application of a water-absorbent resin material, so that the leakage of the battery is completely absorbed inside the battery, and the electrolyte is prevented from leaking outside the battery case. The discharging current of the battery can be greatly improved, the battery can be prevented from leaking liquid and corroding to damage the electric appliance of the battery, and therefore the congenital contradiction defect of the zinc-air battery is effectively overcome.

The invention relates to a night leakage preventing method for a zinc-air battery, which is characterized in that a water-absorbing resin layer is arranged on the inner side of a battery case.

Fig. 1 is a schematic view of a zinc-air battery provided with a water-absorbent resin layer: the electrolyte in the negative electrode calamine cream 5 is absorbed by the water-absorbing resin layer 2 attached to the inner side of the battery case 1 immediately after leaking out through the diaphragm cylinder 4 and the air diffusion electrode 3, so that the electrolyte does not leak out through the air vent hole 7 in the battery case. The air diffusion electrode 3 is connected with the battery shell 1 through a tab 8, and the negative current collecting needle 6 and the negative cover 9 are connected into a whole.

The water-absorbent resin layer used in the present invention may be a porous structure layer such as a mesh-like, fibrous or foamed porous structure. And the thickness thereof should be controlled according to actual needs.

In addition to the rapid and efficient absorption of water by the water-absorbent resin material, factors such as the absorption effect of the water-absorbent resin material on electrolyte ions and the volume change of the material after absorbing liquid are also considered. The inventors have found that the water-absorbent resins of starch or cellulose modification type (such as grafted acrylonitrile), polyacrylic acid type, and polyvinyl alcohol (PVA) type are most effective through exploratory tests. The reason is that the water absorbing chain segments containing nonionic polar groups can generate a complexing effect with electrolyte ions in the solution, and therefore, the water absorbing chain segments also have a good absorption effect on the electrolyte solution.

Compared with the prior art, the invention has the following advantages: (1) The alkaline electrolyte leaked from the air diffusion electrode is absorbed by adopting the water-absorbent resin in the zinc-air battery, and the leaked electrolyte is strictly controlled in the battery, so that the use safety of a battery electric appliance is not influenced; (2) Since the leakage of the zinc-air battery is not related to the pore size of the air-permeable micropores of the air diffusion electrode and the total area of the air-permeable pores, the battery can increase the discharge current by arbitrarily increasing the total area of the air-permeable pores and the pore size of the air-permeable micropores. Therefore, the spear shield and the defects of the principle between eliminating the liquid leakage prevention and alkali climbing of the zinc-air battery and increasing the discharge current are fundamentally solved; (3) The invention is suitable for zinc-air batteries with various sizes and capacities and structures such as cylindrical, square and button structures; (4) The invention goes out of the traditional leakage-proof thought and technical route of the zinc-air battery technology, solves the difficult problems of liquid leakage, alkali leakage and small discharge current which puzzle the practicability and industrialization of the battery for a long time, and undoubtedly brings fundamental turning to the realization of large-scale practicability and industrialization of the zinc-air battery.

Fig. 1 is a schematic view showing the structure of a zinc-air battery provided with a water-absorbent resin layer according to the method of the present invention.

The invention is further illustrated by the following examples and figures.

EXAMPLE 1 fabrication of air diffusion electrode for Zinc-air Battery

The materials of the waterproof breathable layer and the catalytic layer are respectively placed on a large-roller mixing device, are repeatedly rolled and uniformly mixed, are fiberized, and are added on a small-roller forming device for roll-wrapping forming, so that two cylindrical films are prepared; the two cylindrical films and a cylindrical current collecting net are sleeved together and then rolled on a small-roll forming device to form a cylindrical air diffusion electrode. The air diffusion electrode comprises a current collecting net layer, a waterproof breathable layer and a catalytic layer from outside to inside in sequence. Preparation of Zinc electrode, separator and Battery case

The zinc electrode adopts pasty zinc paste, the diaphragm material is a polypropylene non-woven fabric film, the battery shell is the same as the shell of a common zinc-manganese battery, but the positive electrode end of the battery needs to be additionally provided with holes as air holes. A layer of reticular grafted acrylonitrile water-absorbing resin is adhered on the inner side of the battery shell. Assembly of sample cells

After the cylindrical air electrode is formed, it is connected with positive electrode cover of battery by means of tab welding, its internal liner is covered with cylindrical diaphragm cylinder, then the zinc paste is injected into the diaphragm cylinder, and inserted into negative electrode current-collecting needle and covered with negative electrode cover, finally the battery shell is sealed so as to obtain the zinc-air battery shown in attached figure I.

The external dimension of the assembled AA type zinc air sample battery is as follows: 14.0mm in diameter and 49.5mm in height, and discharged with a constant current of 100 mA. The open-circuit voltage of the battery is 1.43V, the average working voltage is 1.20V, the discharge capacity reaches 5600mAh, and the zinc-air battery has no liquid leakage and alkali leakage phenomenon when being placed for 3 months at normal temperature in the discharge process.

EXAMPLE 2 fabrication of air diffusion electrode for Zinc air Battery

The preparation method is the same as the first embodiment, but the square pole piece of 10 multiplied by 10cm is finally cut. Preparation of Zinc electrode, separator and Battery case

The zinc electrode adopts pasty zinc paste, the diaphragm material is a polypropylene non-woven fabric film, and the battery shell adopts a porous plastic shell. A fibrous polyacrylic acid water-absorbent resin was attached to the inside of the battery case. Assembly of sample cells

After the air electrode is formed, the air electrode is connected with a battery positive electrode cover through tab welding, the positive electrode and the negative electrode of the battery are separated through a diaphragm on an inner liner, and finally the battery shell is sealed to obtain the square zinc-air battery.

The external dimension of the assembled square zinc-air sample battery is as follows: 102 mm. Times.12 mm. Times.102 mm, and discharged with a constant current of 300 mA. The open circuit voltage of the battery is 1.43V, the average working voltage is 1.25V, the discharge capacity reaches more than 30Ah, and the zinc-air battery does not have the phenomena of alkali leakage and liquid leakage when being placed for 3 months at normal temperature in the discharge process.

Claims

1. A method for preventing leakage of zinc-air battery is characterized by that a water-absorbing resin layer is placed in the inner side of battery shell.

2. The method for preventing leakage of zinc-air battery according to claim 1, wherein the water-absorbent resin layer is a porous structure layer.

3. The method for preventing night leakage of a zinc-air battery according to claim 2, wherein the porous structure layer has one or more porous structures selected from the group consisting of a net structure, a fiber structure and a foam structure.

4. The method of claim 1 or 2, wherein the water-absorbent resin is a starch or cellulose modified water-absorbent resin.

5. The method of claim 1 or 2, wherein the water-absorbent resin is a polyacrylic acid water-absorbent resin.

6. The method of claim 1 or 2, wherein the water-absorbent resin is a polyvinyl alcohol-based water-absorbent resin.