Mercury free process and control of alkaline manganese dioxide battery

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Mercury free process and control of alkaline manganese dioxide battery

Mercury free process and control of alkaline manganese dioxide battery

(1) Improve the conductivity of zinc paste

The "wettability" of mercury contributes to the connection (adhesion) between zinc powder and between zinc powder and collector, improves the conductivity of zinc paste, and makes the battery have better anti vibration performance. After mercury removal, the conductivity of the battery decreased significantly. To improve the conductivity of zinc paste, we can use zinc paste thickener with high viscosity and good stability, appropriately increase the proportion of zinc powder in zinc paste and add other conductive materials to zinc paste.

(2) Control pollution in production process

The production of mercury free alkaline manganese battery must maintain a clean production environment and pollution-free production process. According to the experience of foreign battery industry, the production is generally required to be carried out under constant temperature and humidity conditions, with the appropriate temperature of 20 ℃ ~ 28 ℃ and humidity of 30% ~ 60% (RH). The assembly of negative electrode assembly is not suitable for low temperature, and the steel shell coated with conductive graphite is not suitable for high humidity. The whole production process shall be dust-free to prevent impurities that increase zinc hydrogen evolution. Intermittent processing of spare parts, many manual operations, parts pollution can not be controlled, and the quality can not be guaranteed.

(3) Controlled carbonation

It is one of the important technological measures to effectively control the carbonation of positive and negative electrodes in the production process of mercury free alkaline manganese dioxide battery. Firstly, the concentration of CO2 in the air shall be controlled. The preparation of zinc paste shall be carried out under vacuum. The electrolyte, zinc paste and positive powder must be sealed and packaged. The exposure time of KOH and mercury free zinc powder to the air shall be reduced as much as possible. When the package is damaged, it shall be prohibited to use, etc. The equipment and conveying track before sealing process shall be equipped with protective shield to reduce air exchange and prevent carbonation of battery products. Attention shall also be paid to controlling the on-line time of the battery. The maximum shutdown time of mercury free battery production under special circumstances shall not exceed two hours. The reliability of domestic equipment is relatively poor and prone to failure. Emergency measures to prevent equipment failure shall be taken.

(4) Pay attention to the influence of Cu and ultra-fine zinc powder on mercury free battery

Copper basically exists in the combined state in the cathode of alkaline manganese battery. Under the action of potential, it is easy to migrate to the anode. The zinc in the anode of the battery accelerates the migration of ultra-fine particles to the cathode due to mercury removal. When there are defect points in the diaphragm tube, Cu2 + and Zn undergo redox reaction at the defect points, and the hydroxide crystal branches of copper gradually penetrate the diaphragm to form a short circuit. The pollution of Cu must be strictly controlled in the production process, and the ultrafine particles in mercury free zinc powder should be limited to prevent the battery short circuit caused by the migration of zinc powder.

(5) The new structure is more suitable for mercury free requirements and battery capacity improvement

The Fuji structure of Japan is still the mainstream of alkaline manganese battery. As for the sealing form, the reliability of this structure is questionable due to the increase of gas evolution of mercury free alkaline manganese battery. The negative electrode assembly with auxiliary sheet is more conducive to sealing. Due to the good consistency of nylon, nylon is better than polypropylene in terms of reliability. Unfortunately, the cost of nylon sealing ring is higher. The structure of alkaline manganese battery in Europe and America is worthy of reference in China. In addition to reliable sealing, the available space of the battery becomes larger, which is more conducive to the improvement of battery capacity.

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Mercury free process and control of alkaline manganese dioxide battery_Alkaline manganese battery