How does the electrolyte affect the Ni-MH battery?

Date:2021-12-02
Summary:

With the continuous improvement of nickel-hydrogen batt […]

With the continuous improvement of nickel-hydrogen battery performance, its application scope is further expanding. Electrolyte is one of the important components of nickel-hydrogen battery, and its composition, concentration, content and impurity type will have a very important influence on the performance of nickel-hydrogen battery.

Usually the electrolyte mainly uses KOH instead of NaOH. The main reason is that the specific conductivity of KOH is higher than that of NaOH, and adding a small amount of LiOH to the KOH solution can increase the discharge capacity of the battery. Because LiOH can be adsorbed around the active material particles to prevent the particles from growing and keep them in a highly dispersed state. However, adding LiOH should not be too much, otherwise it will affect the electro-activation process.

It is generally believed that iron will reduce the overvoltage of oxygen evolution and decrease the charging efficiency of the battery. The carbonate will form a film on the electrode surface, which will increase the internal resistance of the battery; the sulfide will form a dendritic product and cause the battery to short-circuit; The electrode capacity is lost; chloride causes electrode corrosion; therefore, the impurity content in the electrolyte must be controlled.

For a sealed finished rechargeable battery, the space in it is certain. If the electrolyte is too much, the space of the sealed air chamber will become smaller and the internal pressure of the battery will rise during the charging and discharging process; on the other hand, too much electrolyte will block the diaphragm pores and prevent the conduction of oxygen, which is not good for the rapid recombination of hydrogen. , It will also increase the internal pressure of the battery and may oxidize the pole pieces to passivate the pole pieces and decrease the capacity. The increase in internal pressure may cause the battery to leak, climb alkali, and cause the battery to fail.

However, if the electrolyte is too small, the pole pieces will not be completely immersed in the electrolyte, and the electrochemical reaction will be incomplete or some parts of the pole pieces will not be electrochemically reacted, making the battery capacity less than the design requirements, and the internal resistance will change. Larger, shorter cycle life.

In addition, attention must be paid to the concentration of the electrolyte in industrial production to reduce the concentration resistance and ensure that the superior performance of the nickel-hydrogen battery is not affected.