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 the electrolyte. This is the power source of most electric bicycles 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

　　Low temperature lithium iron phosphate battery 3.2V 20A -20℃ charging, -40℃ 3C discharge capacity ≥70%

　　Nickel-metal hydride batteries are very close to our daily lives. From the early days of Suisse to today's small appliances such as rechargeable toothbrushes, they are very common. The positive electrode is a nickel-hydrogen compound and the negative electrode is a metal hydride. Its energy density and number of charge and discharge are compared with each other. Lead-acid batteries have been greatly improved, and the electrolyte is non-flammable, safe, and the manufacturing process is mature. BYD was the world's second largest nickel-metal hydride battery manufacturer before it built 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

　　Low temperature and high energy density 18650 3350mAh-40℃ 0.5C discharge capacity ≥60%

　　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.

　　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.

　　Denza EV400 extreme mileage test results

　　The negative impact of low temperature is not easy to solve from the battery itself, so many car manufacturers find ways to heat the battery pack and add temperature control systems specifically for power batteries. Most brand models that adopt this approach have a certain relief effect, but The actual effect is not an excellent solution to the problem, because the power consumption of some electric vehicle temperature control systems is greater than the loss of low temperature.

　　Emgrand EV450 is equipped with version 2.0 of ITCS battery intelligent temperature control management system

　　What we can look forward to in this regard is that General Motors Group is already interested in cooperating with South Korea's LG Group to purchase products that are directly equipped with multiple temperature control components inside the battery pack. Not only can they dissipate heat for the battery as well as now, but they can also be used in cold weather. Weather increases battery temperature. The implementation of this technology is worth looking forward to. It is reported that GM Group’s next round of new pure electric and plug-in hybrid cars will use it to replace the battery packs currently supplied by the Hitachi brand.

　　hydrogen fuel cell

　　Everyone knows that water is the final product of H2+O2 combustion, so hydrogen is an ideal clean energy source. As far as hydrogen itself is concerned, combustion can release a lot of energy and perform well at low temperatures. The most important thing is that hydrogenation is highly efficient. It only takes 5 minutes to drive more than 600 kilometers with hydrogenation. There is still room for improvement in this data. Above These are far superior to existing lithium batteries.

　　Regarding the investment in hydrogen fuel cell vehicles, car companies in Japan and South Korea have already started research, and now they have invested in the markets of their respective countries on a small scale. For example, the Hyundai NEXO hydrogen fuel cell vehicle that the author tested before the Spring Festival has been used in large quantities. Used in the Pyeongchang Winter Olympics and put on the market.

　　Hyundai NEXO hydrogen fuel cell vehicle

　　And hydrogen is such a good energy source, why isn’t it promoted? Because it is too difficult to obtain hydrogen with current technology. Everyone has learned that hydrogen can be obtained by electrolyzing water, but it consumes electricity to electrolyze water and then burn the hydrogen to eventually turn into water. The power consumption and loss of this process are not as high as directly charging the lithium battery, which is too expensive. The cost and technology are more suitable to be extracted from oil and natural gas, but the quantity is not large, so fuel cell vehicles are "only known by their name and difficult to promote."

　　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.

　　Solid lithium battery

　　As the name suggests, solid-state lithium batteries no longer use liquid electrolytes but use solid electrolytes. Their capacity density is far higher than that of current mainstream lithium batteries. This means that pure electric vehicles have a higher cruising range and can even reach the range of energy-saving gasoline vehicles, and can be charged Efficiency has also made a qualitative leap compared to the current stage. It is reported that electric vehicles equipped with solid-state batteries can increase the charging speed by 800 kilometers in one minute at the most ideal charging speed. This can be said to be the best core component of new energy vehicles.

　　At this stage, some overseas energy and technology companies, as well as battery manufacturers such as Panasonic, have begun the research and development of solid-state batteries. Only the three major Japanese car companies, Toyota, Honda and Nissan, are involved in this area. This is due to the assistance from the Japanese national level. push. Judging from the plans of various parties that have begun to study solid-state batteries, it is expected that there will be breakthroughs in cost, energy density and manufacturing in 2020. It will be 2030 before this research and development result can be implemented and widely popularized in the field of new energy vehicles, which is still far away from us. This is why major car companies did not mention solid-state vehicles when they released their response strategies to the global ban on the sale of fuel vehicles in 2025. Battery reasons.

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