What are the reasons for the self-discharge of Ni-MH batteries

Self-discharge is also called charge retention capability, which refers to the retention capability of the stored power of the Ni-MH battery under certain environmental conditions in an open circuit state. Generally speaking, self-discharge is mainly affected by manufacturing processes, materials, and storage conditions. Self-discharge is one of the important parameters for weighing the performance of Ni-MH batteries. Generally, the lower the storage temperature of the Ni-MH battery, the lower the self-discharge rate, but it should also be noted that the temperature is too low or too high, which may cause the battery to be damaged and unusable. Generally speaking, conventional batteries require a storage temperature range of -20 to 45°C. A certain degree of self-discharge is normal after the battery overflows and is left open for a period of time. The basic types of Ni-MH battery self-discharge: (1) physical self-discharge; (2) chemical self-discharge. (1) Physical self-discharge: refers to the self-discharge caused by physical reasons. When the battery self-discharges, electrons flow from the negative electrode of the battery to the positive electrode of the battery to form an electronic current and the ion current in the electrolyte to form a current loop. The characteristics of physical self-discharge: ①Slightly affected by temperature; ②It can cause the final open circuit voltage of the battery to be zero. (2) Chemical self-discharge: refers to the self-discharge caused by chemical reasons. When the battery self-discharges, no current is formed between the positive electrode and the negative electrode of the battery. The characteristics of chemical self-discharge: ①It is greatly affected by temperature; ②It is greatly affected by the state of charge of the battery; ③Chemical self-discharge cannot cause the battery voltage to be zero. Reasons and characteristics of the self-discharge of Ni-MH batteries 1. Diaphragm ①Poor separation performance of the diaphragm. Poor tensile strength. Poor average performance. ②Poor electronic insulation performance. ③Self-discharge characteristics of the diaphragm. Physical self-discharge or chemical self-discharge. Close to 2. Pole piece ①Pole piece powder drop The characteristics of self-discharge of the pole piece powder A, physical self-discharge B, the whole batch appears C, the self-discharge degree is close to D, the battery is disassembled and the powder is removed clearly ②The winding dislocation 3. The current collector ①The current collector has burrs ②There is a sharp front in the welding part of the tab ③The self-discharge characteristics of the current collector Physical self-discharge occurs in some cases. The degree of self-discharge is severe. Short-circuit occurs. The phenomenon of battery disassembly is unclear. There are impurities in the positive active material self-analysis of the negative active material self-analysis of the pole piece active material self-discharge characteristics A, chemical self-discharge B, the entire batch of C, the degree of self-discharge is related to the state of charge ③diaphragm eluate ④the impurity self-discharge characteristics chemistry Self-discharge The whole batch of self-discharge is close to the phenomenon of disassembling the battery. It is unclear. 5. Other reasons ①External micro short circuit ②Declaration of conductive material deposited on the diaphragm: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete it. A: Overview of the development of power lithium battery technology