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　　Ni-MH battery technology training: Ni-MH battery performance and technology

　　Nickel metal hydride battery technology training provided by electronic enthusiasts: performance and technical requirements of nickel metal hydride batteries A rechargeable battery composed of potassium electrolyte and separators, which is combined with nickel-cadmium batteries

　　Ni-MH battery technical training: Ni-MH battery performance and technical requirements

　　Nickel metal hydride battery is a rechargeable battery composed of hydrogen storage alloy negative electrode, nickel positive electrode, potassium hydroxide electrolyte and separator. The essential difference between it and nickel-cadmium battery is that the negative electrode material does not matter. The voltage of this battery is exactly the same as the nickel-cadmium battery, which is 12 volts. It can be used directly on devices using nickel-cadmium batteries. The idea of nickel-metal hydride batteries was mentioned in the 1970s, a large amount of research was concentrated in the 1990s, and industrial production began in the early years of the last 10 years of the 20th century. The hydrogen storage alloy used as the negative electrode material is an alloy formed of two metals, A and B, in which metal A (La, TI, Zr, etc.) can absorb a large amount of hydrogen to form a stable hydride. While B metals (Ni, Co, Fe, Mn, etc.) cannot form stable hydrides, but hydrogen can easily move in them. That is to say, metal A controls the amount of hydrogen storage, while metal B controls the reversibility of hydrogen storage and desorption. According to the crystal structure of the alloy, the hydrogen storage alloy can be divided into AB5 type, AB2 type, AB type, solid solution type, etc. Among them, AB5 type alloy mainly uses rare earth metals. The AB5 type hydrogen storage alloy is mainly composed of copper lanthanide and nickel, and a small amount of aluminum, manganese, cobalt, etc. are added at the same time. Not all hydrogen storage alloys can be used as negative electrode materials for nickel-metal hydride batteries. The production of nickel metal hydride batteries in Japan mainly uses rare earth metals and mixed rare earth metals as negative electrodes, and the batteries produced account for more than 90% of the world's battery production. The United States mainly uses titanium-silver-based alloys as negative electrodes, and the batteries produced account for about 5% of the world's output, the production company has several companies such as Offenik and Durasel.

　　1. Advantages of nickel metal hydride batteries.

　　Ni-MH batteries have the characteristics of high energy density, high power density, fast charge and discharge, long cycle life, no memory effect, no pollution, easy maintenance, and safe use. They are called green batteries. Compared with the nickel pot battery, the performance index of this kind of battery is generally higher than that of the nickel-cadmium battery; the specific energy of the Ni-MH battery is 1.5-2 times that of the nickel-cadmium battery. When the current is charged and discharged, it has no memory effect, good low-temperature characteristics, and comprehensive performance is better than nickel-cadmium batteries. At the same time, the waste batteries of nickel-cadmium batteries are complicated to deal with. In today's energy shortage and serious environmental pollution, Ni-MH batteries show broad application prospects. . Because the extremely nickel electrode is exactly the same as the nickel-cadmium battery, all electrical appliances that can use nickel-cadmium batteries can use nickel-metal hydride batteries; it is non-toxic, environmentally friendly and has better overall performance than nickel-cadmium batteries, and it will not be as high as lithium The sub-battery is prone to explosion when exposed to moisture. Therefore, the production development speed in the past five years is much higher than that of nickel-cadmium batteries.

　　2. Current status of nickel metal hydride batteries

　　Nickel-metal hydride batteries have the same voltage as nickel-cadmium batteries. The difference is that the self-discharge rate is about high. Other performance indicators are high and low, some are higher than nickel-cadmium batteries, and some are lower than lithium-ion batteries. Table 1 details the current performance levels of nickel metal hydride batteries in Japan.

　　Performance status of small hydrogen storage batteries in Japan

　　Performance Parameters Cadmium/Nickel Batteries Nickel Metal Hydride Batteries

　　Discharge voltage (V) 1.—1.01.2—1.0

　　Weight specific energy (WH/Kg) 50-6060-80

　　Volume specific energy (WH/|) 140-180240-300

　　Price ($/time) 0.060.1

　　Energy price ($/WH) 0.3O.4

　　Low temperature performance (-2O degrees, discharge%) 5O5O

　　Self-discharge (%/month) 1520

　　Fast charging (rate C) 43-20

　　Power density (W/I) 10001000

　　Working temperature (Celsius) -4O—45-40—45

　　Service life (year) 4-84-8

　　Charge control limit (V) 1.41.4

　　Discharge control voltage (V) critical 0.8 critical 0.8