(1) Electrode active material of NiMH battery
The electrode active material determines the theoretical capacity of the electrode and the electrode equilibrium potential, thereby determining the NiMH battery capacity and battery electromotive force. The theoretical capacity of the electrode refers to the amount of electricity calculated according to Faraday’s law that all active materials participate in the flow reaction of the battery.
In addition to the higher theoretical capacity and the more positive (positive) or negative (negative) balance potential of the battery active material, it also requires the active material to have a suitable crystal type, particle size, surface state, etc., so as to obtain a higher activity. Moreover, when the battery is open, the active material should have good stability and have no effect on the components in the battery.
(2) Electrolyte of NiMH battery
The electrolyte is one of the main components of the battery. The properties of the electrolyte (freezing point, boiling point, melting point, etc.) directly determine the operating temperature range of the battery. Improving the properties of the electrolyte can expand the battery’s operating temperature range and improve the battery’s high and low-temperature performance.
The specific conductance of the electrolyte directly affects the internal resistance of the battery. Generally, the higher specific conductance should be selected. But you should also pay attention to the battery’s operating conditions, such as working at low temperatures, but also consider the freezing point of the electrolyte.
For non-aqueous organic solvent electrolytes, the larger the dielectric constant of the electrolyte, the better, and the smaller the viscosity, the better.
The electrolyte needs to be stored in the battery for a long time, so it is required to have good stability. When the battery is open, the electrolyte does not react in any way.
(3) Diaphragm of NiMH battery
The basic requirement of the chemical power supply for the diaphragm is to have sufficient chemical stability and electrochemical stability. It has a certain degree of alkali resistance, corrosion resistance, sufficient isolation, and electronic insulation, and can ensure the mechanical separation of the positive and negative electrodes. It prevents the migration of active substances, has sufficient liquid absorption and moisture retention capacity and ion conductivity to ensure good ion conductivity for positive and negative injections. In addition, it must have good air permeability, sufficient mechanical properties, and shock resistance. The above properties of the separator have an important impact on the battery’s internal resistance, discharge characteristics, storage performance, self-discharge, cycle performance, internal pressure, and overcharge resistance. A reasonable choice of the type and thickness of the separator is particularly important for battery performance. . Commonly used in MH-Ni batteries are polypropylene felt diaphragm, polyamide diaphragm, and so on.
(4) Electrode preparation process of nickel-hydrogen battery
The manufacturing methods of the electrode include powder compaction method, paste coating method, sintering method, and deposition method. Different manufacturing methods have their own characteristics. The pressing method is simple in equipment, convenient to operate, and more economical. It can be used in general battery series; the paste method is also common, and the battery made by the paste method has a longer life and less self-discharge; The sintered electrode has a long life and good high-current discharge performance. The electrodeposited electrode has a high porosity, a large specific surface area, and high activity, which is suitable for the high-power and rapid activation of batteries.
In the electrode preparation process, it is often necessary to add some conductive agents, dispersants, liquid retention agents, and additives to the active material to increase the utilization rate of the active material and improve the electrode conductivity, thereby increasing the actual capacity of the electrode and the discharge performance of the battery, Cycle performance, etc. Electrode preparation technology is often the key and core of battery manufacturing technology.
(5) Battery structure and assembly of NiMH battery
A reasonable battery structure is conducive to the best performance of the battery. The ratio of the two-pole materials, the tightness of the battery assembly, and the size of the upper air chamber of the battery all have a certain degree of influence on the battery’s internal resistance, internal pressure, and utilization of active materials.
The welding method and welding quality of the battery in the assembly process also have a greater impact on the discharge performance of the battery.