Why are Ni-MH batteries not adopted by new energy vehicles?

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Ni-MH batteries have low energy density, short service life, and memory effect characteristics, which are the fundamental reasons why new energy vehicle power batteries exclude it.

Power battery is one of the most core components of new energy vehicles. It not only affects the driving range of new energy vehicles through energy storage capacity, but also determines the service life of the vehicle through the cost of construction, and even has a profound impact on the safety performance and acceleration performance of the vehicle. It can be said that the quality of power batteries is extremely important for the development of new energy vehicles.

The basic function of a power battery is energy storage. In the battery market, in addition to the familiar lead-acid batteries and lithium-ion batteries, there are also nickel-cadmium batteries, nickel-hydrogen batteries, etc., among which Ni-MH batteries are favored by Toyota and Honda for energy storage in hybrid electric vehicles. , And new energy vehicles choose lithium-ion batteries as power batteries.

Compared with nickel-chromium batteries, nickel-metal hydride batteries have the advantages of low memory effect, good environmental performance, and long service life. The storage capacity is also about 30% higher than that of nickel-cadmium batteries. However, the cost of nickel-metal hydride batteries is much more expensive than nickel-cadmium batteries.

Compared with lithium-ion batteries, the only advantage of nickel-hydrogen batteries is that they are relatively cheap, but in terms of performance, they are far lower than lithium-ion batteries.

As mentioned earlier, the power battery has an important impact on the driving range, cost, service life, and safety performance of new energy vehicles. In particular, the driving range, which is the main embodiment of the technical level of new energy vehicles, is basically Determined by the power battery.

The complex environment of new energy vehicles and the high requirements for power output determine that power batteries require a higher voltage platform. The voltage of Ni-MH battery is only 1.2V, while the voltage of Li-ion battery can reach 3.7-4.2V. The voltage platform of lithium-ion batteries is higher.

At present, the number of charging cycles in the life cycle of lithium-ion batteries can reach more than 1,000 times (ternary lithium batteries), and lithium iron phosphate batteries can reach more than 2,000 times. The number of charging cycles of nickel-hydrogen batteries is only about 500 times, and the service life is much lower than that of lithium-ion batteries.

Due to the active nature of lithium ions, the charging speed is faster. A lithium-ion battery can be fully charged in about 3 hours, while the charging speed of a nickel-metal hydride battery is much slower.

In terms of energy density, lithium-ion batteries are even more dominant. At present, the energy density of lithium-ion batteries can reach 300Wh/kg, while the highest energy density of nickel-hydrogen batteries is only 140Wh/kg. If nickel-hydrogen batteries are used as power batteries, the driving range of new energy vehicles will be very short. However, the lower energy density characteristics make the safety performance of nickel-hydrogen batteries better than lithium-ion batteries.

The self-discharge rate of Ni-MH batteries is much higher than that of Li-ion batteries, up to 25%-35% per month, while Li-ion batteries are only 2%-5%.

Ni-MH batteries have low energy density, short service life, and memory effect characteristics, which are the fundamental reasons why new energy vehicle power batteries exclude it. The basic reason for choosing nickel-metal hydride batteries as power batteries for gasoline-electric hybrid vehicles that do not require high energy storage is the cost. However, as the cost of lithium-ion batteries has been declining year by year, Honda's hybrid electric vehicles have given up using nickel-metal hydride batteries. At present, nickel-metal hydride batteries are basically used in emergency lights, remote controls, toys, etc., in areas where there is no special requirement for energy storage, and the usage is also declining year by year.

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