LR621 battery.Sealed lead-acid battery pack

　　Nickel hydrogen battery

　　Nickel hydrogen batteries are very close to our daily lives. From the early audio, it can be heard that small appliances such as rechargeable toothbrushes are common nowadays. The positive electrode is made of nickel hydrogen compounds, and the negative electrode is made of metal hydride. Its energy density and charging and discharging times are significantly improved compared to lead-acid batteries. Moreover, the electrolyte is non flammable, safe, and the manufacturing process is mature. Before making cars, BYD was the world's second largest manufacturer of nickel hydrogen batteries.

　　Nickel hydrogen battery pack

　　However, due to its average charging efficiency, memory effect, and low working voltage (unable to use high-voltage fast charging), nickel hydrogen batteries are not suitable for a single power source in automobiles and are suitable for assisting engine operation. The best performer in this regard is Toyota, which uses an Atkinson engine and a nickel hydrogen battery pack in its hybrid system. The Atkinson engine itself has the advantage of high efficiency in the middle speed range, but it also has the problem of low and high speed weakness. The nickel hydrogen battery can precisely solve the problem of insufficient starting and high-speed power.

　　After the widespread use of lithium-ion batteries, nickel hydrogen batteries have also shown a trend of being completely replaced in automobiles, such as the Toyota new generation hybrid system adopting a more efficient combination of engine and lithium-ion batteries. Compared to lithium-ion batteries, nickel hydrogen batteries have no advantages in terms of capacity, cycle charging life, and environmental protection. The cost advantage has also been weakened by the strong development of lithium-ion batteries, which is precisely why nickel hydrogen batteries are gradually withdrawing from the automotive industry.

　　Lithium ion batteries

　　Lithium ion batteries are currently the mainstream choice for new energy vehicles. Lithium compounds (such as lithium manganate and lithium iron phosphate) are used as electrode materials, while graphite is used as negative electrode material. Its advantages lie in high energy density, small size, light weight, and high charging efficiency. The important factor determining the type or performance of lithium-ion batteries lies in the materials of the battery poles, among which the positive electrode material is the key at present, such as mainstream lithium iron phosphate, lithium cobalt oxide in ternary materials, nickel cobalt manganese, etc. There are differences in capacity, cost, low-temperature charging and discharging, safety, and other dimensions.

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