What is the material of the positive electrode of a nickel-hydrogen battery?

Cathode material in NiMH battery:

Nickel-based current collector: foamed nickel or nickel foil;

Active material: nickel hydroxide nickel (Ni) 2;

Conductive agent: nickel powder;

Additives: cobalt, cobalt oxide, Y2O3, Yb2O3, etc.;

Adhesive: CMC, PTFE, etc.

Powder (including positive electrode active material and negative electrode active material) → pole piece production [including positive electrode negative electrode sheet, process coating, drying (not required for dry film production), rolling, cutting, weighing, positive electrode sheet Need to spot the ear and cover the ear with insulating tape] → Winding into the shell (previously need to prepare the appropriate size of the diaphragm) → rolling groove → filling the electrolyte → adding sealing ring → spot welding battery cover → sealing → battery activation →Capacity sorting

Nickel-metal hydride batteries are a good battery. Nickel-metal hydride batteries are classified into high-voltage nickel-hydrogen batteries and low-voltage nickel-hydrogen batteries. The positive electrode active material of the nickel-hydrogen battery is Ni(OH)2 (called NiO electrode), the negative electrode active material is metal hydride, also called hydrogen storage alloy (electrode called hydrogen storage electrode), and the electrolyte is 6 mol/L potassium hydroxide solution. Nickel-hydrogen batteries have become more and more important as an important direction for hydrogen energy applications.

Since fossil fuels have become less and less in the case of large-scale development and utilization of human beings, the development and utilization of hydrogen energy has received increasing attention in recent years. Nickel-hydrogen batteries have become more and more important as an important direction for hydrogen energy applications. Although nickel-metal hydride batteries are indeed a good performance battery,special nickel-metal hydride batteries are high-voltage nickel-hydrogen batteries (hydrogen pressure up to 3.92 MPa, or 40 kg/cm2). Such high-pressure hydrogen is stored in thin-walled containers. It is easy to explode, and nickel-metal hydride batteries also need precious metals as catalysts, making its cost very expensive, which is difficult to accept for civilian use. Therefore, foreign low-voltage nickel-metal hydride batteries have been explored since the 1970s. Nickel-metal hydride batteries are classified into high-voltage nickel-hydrogen batteries and low-voltage nickel-hydrogen batteries. High-voltage nickel-metal hydride batteries were first developed in the early 1970s by M. Klein and J. F. Stockel of the United States. The trend of replacing nickel-hydrogen batteries with nickel-hydrogen batteries and applying them to variousspecials has been formed.

The positive electrode active material of the nickel-hydrogen battery is Ni(OH)2 (called NiO electrode), the negative electrode active material is metal hydride, also called hydrogen storage alloy (electrode called hydrogen storage electrode), and the electrolyte is 6 mol/L potassium hydroxide solution. The process of forming the electrode sheet of the active material mainly includes sintering type, slurry type, foam nickel type, fiber nickel type and inlay type. The electrodes prepared by different processes have large differences in capacity and large current discharge performance. The battery is produced according to a process using different conditions. Most of the consumer batteries such as communication use a slurry-type negative electrode and a foamed nickel-type positive electrode to form a battery. The charge-discharge chemical reaction is as follows [1]:

Positive electrode: Ni(OH)2+OH-=NiOOH+H2O+e-

Negative electrode: M+H2O+e-=MHab+OH-

Total reaction: Ni(OH)2+M=NiOOH+MH

Note: M: hydrogen alloy; Hab: adsorption of hydrogen; the process of the reaction from left to right is the charging process; the process of the reaction from right to left is the discharge process.

Ni(OH)2 and OH- of the positive electrode react to form NiOOH and H2O during charging, and release e- together to form MH and OH-. The total reaction is Ni(OH)2 and M to form NiOOH, hydrogen storage alloy hydrogen storage; discharge In contrast, MHab releases H+, H+ and OH- to form H2O and e-, NiOOH, H2O and e- regenerate Ni(OH)2 and OH-. The standard electromotive force of the battery is 1.319V.

Nickel-metal hydride batteries are classified into high-voltage nickel-hydrogen batteries and low-voltage nickel-hydrogen batteries.

The low-voltage nickel-hydrogen battery has the following characteristics: (1) the battery voltage is 1.2~1.3V, which is equivalent to the cadmium-nickel battery; (2) the energy density is high, 1.5 times or more of the cadmium-nickel battery; (3) the rapid charge and discharge, low temperature Good performance; (4) sealable, strong resistance to overcharge and discharge; (5) no dendritic crystal formation, can prevent short circuit inside the battery; (6) safe and reliable, no pollution to the environment, no memory effect. [1]

The high-voltage nickel-hydrogen battery has the following characteristics: (1) High reliability. It has better over-discharge and over-charge protection, and can withstand high charge and discharge rates and no dendrite formation. Has a good ratio characteristic. Its mass specific capacity is 60A·h/kg, which is five times that of cadmium nickel batteries. (2) The cycle life is long, up to thousands of times. (3) Fully sealed and less maintenance. (4) The low temperature performance is excellent, and the capacity does not change significantly at -10 °C.

NiMH batteries should be maintained during use.

(1) Avoid using the process of charging. Within the cycle life, the use process should not overcharge, because overcharge easily causes the positive and negative electrodes to swell, causing active material shedding and diaphragm damage, conductive network damage and battery ohmic polarization to become larger.

(2) Prevent deterioration of the electrolyte. During the cycle life of Ni-MH batteries, the hydrogen evolution of the battery should be suppressed.

(3) Storage of nickel-metal hydride batteries. The nickel-metal hydride battery should be stored in a fully charged state. If the battery is stored for a long period of time without storing electrical energy in the battery, the function of the battery negative hydrogen storage alloy will be weakened and the battery life will be shortened.

(4) Charging after the battery is exhausted. Nickel-metal hydride batteries and nickel-cadmium batteries have the same "memory effect", that is, if the battery is repeatedly charged while the battery is still in the middle of the discharge, the battery will soon be unavailable.

Nickel-metal hydride batteries are already a mature product. At present, the number of nickel-hydrogen batteries produced in the international market is about 700 million. The scale and output of nickel-hydrogen battery industry in Japan has always been among the highest in the world. The United States and Germany are only in Japan, in Ni-MH. The battery field has also been developed and developed for many years. China's rare earth metal resources for the manufacture of nickel-hydrogen battery raw materials are abundant, and proven reserves account for more than 80% of the world's proven reserves. At present, the raw material processing technology of nickel-hydrogen battery researched and developed in China is also becoming mature. Nickel-metal hydride batteries can be used interchangeably with zinc-manganese batteries and cadmium-nickel batteries. In the future, circular batteries will mainly develop toward product diversity and commercialization, and the development of square batteries is mainly used as a power source for power vehicles.

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