Analysis of the development of power lithium battery technology -Lithium - Ion Battery Equipment
Lead-acid batteries
Pure electric vehicles first used lead-acid batteries. Lead and its oxides were used as electrode materials, and sulfuric acid solution was used as electrolyte. This is the power source of most electric bicycles. Low cost is its biggest advantage. However, due to the low energy density of lead-acid batteries, it brings problems such as large volume and small capacity, which cannot satisfy a car's self-weight control, driving force consumption, and even a service life of more than 10,000 kilometers per year. It could not be used in mass production vehicles on a large scale, and was eventually eliminated by car manufacturers.
NiMH batteries
Nickel-metal hydride batteries are very close to our daily life. From the early days, we heard that small electrical appliances such as charging toothbrushes are very common. The positive electrode is a nickel-metal hydride compound, and the negative electrode is a metal hydride. Lead-acid batteries have improved a lot, and the electrolyte is non-flammable, safe, and the manufacturing process is mature. BYD was the world's second largest manufacturer of nickel-metal hydride batteries before it built cars.
NiMH battery pack
However, due to the general charging efficiency of nickel-metal hydride batteries, the memory effect of charging, and the low working voltage (high-voltage fast charging cannot be used), it is not suitable for the single power source of the car and is suitable for assisting the engine to work. Toyota has done the best in this regard. Its hybrid system uses Atkinson engine + NiMH battery pack. Atkinson engine itself has the advantage of high efficiency in the middle speed range, but it also has the problem of low speed and high speed weakness. , and the nickel-metal hydride battery is just a big boost to solve the lack of starting and high-speed power.
After the widespread introduction of lithium batteries, nickel-metal hydride batteries also tend to be completely replaced in automobiles. For example, Toyota's new-generation hybrid system uses a more efficient engine + lithium battery combination. Compared with lithium batteries, nickel-metal hydride batteries have no advantages in terms of capacity, cycle charging life and environmental protection. The cost advantage has also been weakened by the vigorous development of lithium batteries. This is the reason why nickel-metal hydride batteries are gradually withdrawing from the automotive field. where.
lithium battery
Lithium batteries are the mainstream choice for new energy vehicles at this stage. Lithium compounds (lithium manganate, lithium iron phosphate, etc.) are used as electrode materials, and graphite is used as negative electrode material. Its advantages are high energy density, small size, light weight, and charging efficiency. high. The main factor that determines the type or performance of lithium batteries lies in the materials of the two poles of the battery, of which the material of the positive electrode is the key at this stage, such as the mainstream lithium iron phosphate, lithium cobalt oxide in ternary materials, nickel cobalt manganese, etc. There are differences in many dimensions such as cost, low temperature charge and discharge, and safety.
General Group Lithium Battery Pack
However, no matter what type, all lithium battery packs will face the "natural enemy" of low temperature. Although the optimal working temperature of different lithium battery types is different to a certain extent, the reduction in the activity of lithium ions accompanying the lower than the optimal range has a great impact on the cruising range, which is also reflected in our previous tests: The battery life of electric vehicles equipped with lithium battery packs in actual use in winter in the north can generally only reach more than 60% of the theoretical battery life, and at most about 70%.