What are the types and technologies of power batteries for new energy vehicles?

　　Pure electric vehicles first used lead-acid batteries. Lead and its oxides were used as electrode materials and sulfuric acid solution was used as the electrolyte. This is the power source of most battery vehicles today. Low cost is its biggest advantage. However, because the energy density of lead-acid batteries is low, it brings about problems such as large size and small capacity. It cannot meet the weight control of a car, the consumption of driving force, and even the service life of more than 10,000 kilometers per year. Therefore, It could not be used on mass-produced vehicles on a large scale and was eventually eliminated by automobile manufacturers.

　　Sealed lead-acid battery pack

　　NiMH batteries

　　Nickel-metal hydride batteries are a new type of green battery developed in the 1990s. They have the characteristics of high energy, long life, and no pollution. Nickel-metal hydride batteries are very close to our daily lives. From the early days of Suisse to the present Rechargeable toothbrushes and other small appliances are very common. The anode is a nickel-hydrogen compound and the cathode is a metal hydride. Its energy density and number of charge and discharge times are greatly improved compared to lead-acid batteries. The electrolyte is non-flammable and safety is guaranteed. , the manufacturing process is mature, and BYD was the world's second largest nickel-metal hydride battery manufacturer before building cars.

　　NiMH battery pack

　　However, because the charging efficiency of nickel-metal hydride batteries is average, there is a charging memory effect, and the working voltage is low (high-voltage fast charging cannot be used), it is not suitable for the single power source of the car and is suitable for auxiliary engine work. Toyota is the best in this regard. Its hybrid system uses an Atkinson engine + a nickel-metal hydride battery pack. The Atkinson engine itself has the advantage of being efficient in the middle speed range, but it also has the problem of weakness at low and high speeds. , and the nickel-metal hydride battery can be a great help to solve the lack of power at starting and high speed.

　　Since lithium batteries have been widely used, nickel-metal hydride batteries have also been completely replaced in cars. 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. location.

　　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 anode materials. Its advantages include 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 battery poles. The material of the positive electrode is the key at this stage, such as the mainstream lithium iron phosphate, lithium cobalt oxide, nickel cobalt manganese, etc. in the ternary materials. In terms of capacity There are differences in multiple dimensions such as cost, low-temperature charging and discharging, and safety.

　　Lithium battery pack

　　However, regardless of type, all lithium battery packs will face the "natural enemy" of low temperature. Although there are certain differences in the optimal operating temperatures of different lithium battery types, the decrease in lithium ion activity that occurs when the temperature is lower than the optimal range has a greater impact on the cruising range. This has also been reflected in our previous tests: The actual range of electric vehicles equipped with lithium battery packs in northern winter can generally only reach more than 60% of the theoretical range, or about 70% at most.

　　hydrogen fuel cell

　　Everyone knows that water is the final product of H2+O2 combustion, so hydrogen is an ideal clean energy source. It is characterized by no pollution, no noise, and high efficiency. As for the hydrogen itself, combustion can release a large amount of energy and has excellent low-temperature performance. The most important thing is that the hydrogenation efficiency is high. It only takes 5 minutes to drive more than 600 kilometers with hydrogenation. , with a speed of 140~150 kilometers per hour. And there is still room for improvement in this data. All of the above are far superior to existing lithium batteries. However, a hydrogen fuel cell car is more than 200 kilograms heavier than a similar type of internal combustion vehicle and is more than five times more expensive.

　　It is not yet popular in China, and the reason is that it is expensive.

　　graphene battery

　　Regarding the discussion of power batteries for future new energy vehicles, the most reliable and most discussed one is the graphene battery. To "translate" some professional interpretations is: there are two ways to use this material combined with lithium batteries. One is The graphene composite material is used as the conductive agent of the lithium battery, and the second is directly used as the negative electrode. The effect is to increase the activity of the lithium battery, thereby improving the cruising range and charging speed of the electric vehicle.

　　Graphene-carbonized sponge lithium-oxygen battery

　　Graphene batteries can effectively solve the shortcomings of lithium batteries, and the product characteristics are directly linked to the use of new energy vehicle users. The benefits of this material are indeed great, and South Korea's Samsung has also announced that it has mastered this technology, but the cost is a major bottleneck. It is not easy to obtain graphene. In the early days, it was a material used in the aerospace field. When and How to reduce costs will be a major problem for this high-quality product to "fly into the homes of ordinary people". Various automobile manufacturers have not yet announced plans to make efforts in this regard.

　　To put it simply, the working principle of pure electric vehicles is to "charge directly with electricity", while hydrogen fuel cell vehicles "burn" (chemical reaction) H2+O2 into electricity and water, which is equivalent to "burning hydrogen" to generate electricity. Both "batteries" are also zero-emission. The lithium battery of electric vehicles has smaller capacity density, poor low-temperature activity, which affects battery life, and slow charging speed. Hydrogen fuel cells do not have the problem at all, and their working efficiency is much higher. This is exactly The reason hydrogen is called a premium energy source.

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