nickel hydrogen battery is a good performance of the battery. NiMH batteries divided into high and low-voltage nickel-hydrogen batteries nickel-hydrogen batteries. NiMH battery positive electrode active material of Ni (OH) 2 (referred NiO electrode), the negative electrode active material is a metal hydride, hydrogen storage alloy, also known as (hydrogen storage electrode, said electrode), an electrolyte of 6mol / L potassium hydroxide solution. NiMH batteries direction as a important application of hydrogen energy is more and more people pay attention.
1. The nickel-metal hydride batteries nickel hydrogen batteries appear
fossil fuels become less and less in the case of large-scale human development and utilization in recent years, the development and utilization of hydrogen energy have received increasing attention. NiMH batteries direction as a important application of hydrogen energy is more and more people pay attention. Although nickel-hydrogen battery is indeed good performance of the batteries, but nickel-hydrogen batteries for aerospace high-voltage nickel hydrogen battery is (a hydrogen pressure up to 3.92MPa, i.e. 40kg / cm2), such a high pressure hydrogen gas stored in the thin-walled containers explosive, but NiMH batteries also need to do a noble metal catalyst, so that its cost becomes very expensive, making it difficult for the civilian accepted, therefore, foreign civilian since the 1970s began to explore low-voltage nickel-metal hydride batteries.NiMH batteries divided into high and low-voltage nickel-hydrogen batteries nickel-hydrogen batteries. High-voltage nickel-metal hydride battery is the early 1970s and developed by the American M.Klein J.F.Stockel other first. Instead of nickel-cadmium batteries and nickel-hydrogen batteries for trend has been formed on the various satellites.
2. The structure and principle of a nickel hydrogen battery
nickel hydrogen battery positive electrode active material of Ni (OH) 2 (referred NiO electrode), the negative electrode active material is a metal hydride, hydrogen storage, also known as alloy (hydrogen storage electrode, said electrode), an electrolyte of 6mol / L potassium hydroxide solution. Process electrode constituting the electrode active material embodiment of the main-sintered sheet, pull paddle, foamed nickel type, nickel-type and fiber type and the like embedded infiltration, electrodes of different preparation processes there is a big difference in capacity, large current discharge characteristics, general the production process conditions of different batteries. Most civilian communications battery using a negative electrode pull paddle, a nickel positive electrode for constituting the battery. Charge-discharge chemical reaction is as follows:
of the positive electrode: Ni (OH) 2 + OH- = NiOOH + H2O + e-
negative electrode: M + H2O + e- = MHab + OH-
The overall reaction: of Ni ( OH) 2 + M = NiOOH + MH
Note: M: hydrogen storage alloy; Hab: hydrogen absorbed; the reaction of formula from left to right during a charging process; reactive right to left during the discharge process.
of the positive charging Ni (OH) 2 and NiOOH reaction of OH- and H2O, while releasing e- MH and OH- generated with a total reaction is Ni (OH) 2 and NiOOH M generated, the hydrogen storage alloy reservoir hydrogen; discharge contrary, MHab release H +, H + and OH- generated H2O and e-, NiOOH, H2O and e- regenerate Ni (OH) 2 and OH-. Standard electromotive force cell was 1.319V.
3. NiMH batteries Category
into high-voltage nickel-hydrogen battery and a nickel hydrogen battery low-voltage nickel-hydrogen battery.
low-voltage nickel-hydrogen battery has the following characteristics: (1) the battery voltage of 1.2 ~ 1.3V, comparable Ni-Cd battery; (2) high energy density, is 1.5 times or more nickel-cadmium batteries; (3) fast charge discharge, good low temperature performance; (4) a sealable, strong resistance to overcharge discharge capability; (5) generating no dendrites short circuit the battery can be prevented; (6) safe environmental pollution, no memory effect.
high-voltage nickel-hydrogen battery has the following characteristics: strength (1) reliability. Has better overdischarge, overcharge protection, can withstand high rate charge and discharge and no dendrite formation. Good ratio characteristics. The mass ratio of capacity of 60A · h / kg, 5 times of the Ni-Cd battery. (2) long cycle life, up to thousands of times. (3) fully sealed, low maintenance. Excellent (4) low temperature performance, at -10 deg.] C, no significant change in capacity.
4. Maintenance of the nickel hydrogen battery
In NiMH batteries should pay attention to maintenance.
(1) using the procedure avoid overcharging. In the cycle life, the use of the process avoid overcharging, the overcharge because easy to make positive and negative electrode expands, resulting in loss and active membrane damage and cell damage conductive network ohmic polarization becomes large and so on.
(2) to prevent deterioration of the electrolytic solution. In the cycle life of the nickel hydrogen battery, the battery should be suppressed hydrogen evolution.
(3) deposited nickel-hydrogen battery. NiMH batteries should be stored fully charged, if the battery is not in a case where long-term storage battery for storing electric energy, the hydrogen storage alloy negative electrode of the battery will weakened, and results in shortened battery life.
(4) after charging the battery is empty. The same nickel-hydrogen batteries and nickel-cadmium batteries, have a “memory effect”, i.e., if the discharge way rechargeable battery still remains in the state of use of power, the battery can not be used quickly.