Selection of zinc alloy powder for low mercury in alkaline batteries

Date:2021-10-09
Summary:

Today, people’s awareness of environmental protection c […]

Today, people’s awareness of environmental protection continues to increase. Commonly used alkaline batteries have achieved low mercury or even mercury-free. Among them, the choice of alloy gold powder is the main improvement measure for alkaline batteries to reduce mercury.
In order to reduce mercury in the negative electrode of the battery, the zinc powder alloy must first meet the following conditions: (1) It is difficult to corrode in the high electrolyte; (2) Has no adverse effect on the zinc powder anode; (3) Does not contain or contains less harmful additives Elements; (4) The purity of zinc powder should be high; (5) The cost of materials does not increase much. The amalgamation of zinc powder in alkaline zinc-manganese batteries is mainly to increase the hydrogen overvoltage of the zinc powder in the alkaline electrolyte and inhibit the generation of hydrogen in the lye. The amalgamation film formed after the amalgamation of zinc powder can cover the surface of the zinc powder evenly and smoothly, thereby changing the surface condition of the zinc particles and activating the zinc electrode, thereby improving the electrical performance of the battery and reducing the leakage rate of the battery. In the battery discharge process, mercury continuously diffuses from the surface of the zinc particles to the inside of the zinc particles, so that the discharge is stable. Therefore, under the condition of low amalgamation rate, to maintain the corrosion resistance of zinc powder, it is necessary to add an appropriate amount of trace elements that can increase the hydrogen overpotential and prevent mercury from diffusing into the zinc particles before the battery is discharged, and without affecting the discharge Within the reaction range, appropriately reduce the specific surface area of ​​the zinc powder.
Selected translations of trace addition elements generally use indium as a necessary addition element, because it can not only increase the hydrogen overvoltage on the surface of the zinc alloy particles, but also easily make the zinc surface easy to alloy with mercury, and the effect of addition is more obvious. Therefore, whether it is a low-mercury zinc oxide or a mercury-free zinc powder, the indium element is currently a must-add element. Other added elements are: lead, aluminum, bismuth, cadmium, etc. The cadmium element itself has high hydrogen overvoltage, so it has good corrosion resistance, but they are more toxic, and should be used as little as possible in some low mercury or mercury-free batteries Or not.
In the production of low-mercury alkaline batteries, battery manufacturers have also adopted measures such as the addition of organic surfactants and the treatment of silver nails in the current collector.