A pure electric vehicle is a vehicle that uses a battery as an energy storage unit and an electric motor as a drive system. The characteristics of pure electric vehicles are relatively simple structure and relatively mature production technology; its disadvantage is that the charging speed is relatively slow. Therefore, pure electric vehicles are suitable for vehicles with relatively fixed driving routes and capable of charging for a long time, such as: buses, airport shuttles, small delivery vehicles, etc. However, when charging stations are not as popular as gas stations, and commercial mechanisms such as battery replacement and leasing are not yet mature, pure electric cars and long-distance buses cannot be used on a large scale.
Compared with fuel vehicles, electric vehicles have shown significant fuel-saving and environmental protection effects. The calculation results show that after more than 20,000 buses and 70,000 taxis in Beijing are converted to electric vehicles, it can save 3 million tons of fuel and emit nearly 10 million tons of carbon dioxide gas every year. The development of electric vehicles is also of great significance to the effective use of power resources. Since 2002, the power shortage situation in China has become more and more serious. The number of provincial power grids with power cuts increased from 12 in 2002 to 23 and 26 in 2003 and 2004 respectively. Since the Ninth Five-Year Plan, Beijing’s electricity load has also increased rapidly. In 2004, Beijing’s shared electricity was about 50 billion kilowatt-hours, and its dependence on external power exceeded 60%. The peak load of electricity consumption in Beijing is in summer, and office air-conditioning load accounts for more than 40% of the total load. About half of the electricity is idle at night when the electricity consumption is low. The current situation makes the waste of power resources very serious. Can make full use of the excess electricity at night to meet the needs of charging electric buses and taxis. In addition, home and office energy storage devices made of large-capacity power batteries to store cheap electricity at night for use during the day will also greatly ease the problem of unbalanced use of day and night power resources.
In 2004, China surpassed Germany to become the world's third largest automobile country. It is estimated that China will become the world's second largest automobile country in the future. If no measures are taken, the ensuing energy, environmental, transportation and health problems in China will be much more serious than they are now. Therefore, continuous improvement of power lithium-ion battery and electric vehicle technology will have important social and strategic significance for alleviating energy and environmental problems in China and the world.
Power battery technology is one of the key technologies of electric vehicles, and major automobile companies are making every effort to develop the core technology of electric vehicles-new battery technology. The three major U.S. automobile companies established the Advanced Battery Association (US-ABC) and formulated technical performance indicators for mid- and long-term research and development of advanced batteries. The medium-term goal is to significantly improve the performance of power batteries for electric vehicles, and realize the commercialization of power batteries by 2000; the mid-to-long-term goal is to ultimately make electric vehicles competitive with fuel-fueled vehicles in terms of performance and price. China’s "Eleventh Five-Year" National 863 Program "Energy-saving and New Energy Vehicles" is a major project plan that by 2010, hybrid vehicles will achieve breakthroughs in industrial scale on the basis of mastering product development technologies, pure electric vehicle technology to meet the needs of industrialization, and will realize the market development of commercial applications. Electric vehicles will become an important means of transportation in the 21st century.
So far, the power (energy storage) batteries for electric vehicles have gone from valve-regulated lead-acid batteries to nickel-cadmium, nickel-metal hydride and other alkaline batteries to lithium-ion batteries (including polymer lithium-ion batteries). Compared with other batteries, lithium-ion batteries have higher specific energy, specific power and cycle life, and become one of the first choice power batteries for electric vehicles. Nissan Altra EV was equipped with SonyLA 4 LIB in July 1997, and it was introduced to the California market in January 1998; in October 1997, France launched the VEDELIC new technology project for electric vehicles. The Peugeot 106 EV equipped with LIB is the first electric vehicle in Europe to use lithium-ion batteries as a power source.
China’s research level on lithium-ion batteries has already exceeded most of the targets set by the USABC’s 2010 long-term indicators. The loading test of the 100A·h high-capacity lithium manganate power battery provided by CITIC Guoan Mengguli Power Technology Co., Ltd. for the Beijing Olympic Electric Vehicle Project has been completed (Figure 1). It has been running for more than 50,000 kilometers and the battery is in good working condition. It is reported that the charging time of this kind of electric bus is short, the charging capacity can reach 95% in 3h, and it can run 200~400km every time it is charged, and the battery capacity will decrease by 8.3% every 500 times, and its operating cost is only 1/5 of that of a fuel vehicle. At present, the leading manufacturers in the development of power battery LIB are Sony of Japan, Varta of Germany and Saft of France. In addition, polymer lithium-ion batteries (PLB) have a higher specific energy than LIB, and have been identified by the United States Advanced Battery Association (USABC) as a power battery for electric vehicles to achieve the 2010 long-term goal.
Figure 1 - 100A·h lithium-ion battery electric bus that has been running for 50,000 kilometers
Although the development level of traditional Chinese cars is more than 30 years behind the advanced levels of other countries, due to the short development period of electric vehicles in other countries and the same key component technology platform, China's electric vehicle research and development level is almost on the same starting line as that of developed countries, and the biggest gap is no more than 5 years. Therefore, electric vehicles have become a breakthrough for China to catch up with the world's advanced level. However, for China's electric vehicles to be industrialized, there are still three major bottlenecks that need to be broken.
The first is policy. The government's support for the production and use of environmentally friendly, energy-saving and new energy vehicles will affect the progress of development. It is necessary to formulate relevant policies and regulations as soon as possible to encourage consumers to purchase energy-efficient vehicles, and give manufacturers a certain policy preference. Japan, France and other countries have implemented tax reductions and exemptions for their citizens to purchase environmentally friendly cars. Although China's new automobile industry policy reflects this desire, it is only a programmatic document and should be implemented as soon as possible. In addition, the problem of blank legislation standards for new energy vehicles needs to be resolved urgently. The registration procedures, safety standards, and maintenance standards for electric vehicles should be promulgated as soon as possible.
The second is cost. The manufacturing cost and use cost of new energy vehicles are still high. The average manufacturing cost of an ordinary pure electric car is two to three million yuan, while the market price of an ordinary fuel car is less than 100,000 yuan. After the new power vehicles are on the road, because the product structure is different from ordinary fuel vehicles, manufacturers need to re-establish a set of maintenance and maintenance service systems, and the investment is huge. Moreover, the current profits of traditional fuel vehicles are quite good, and manufacturers lack the enthusiasm to promote alternative products.
The third is technology. Electric vehicles are currently only "manually" produced and are in the trial operation stage. The real commercial operation requires further technical improvements to reduce battery costs and improve battery efficiency. At present, electric vehicles have a long charging time and limited mileage. They can only partially replace traditional vehicles in specific occasions such as cities and scenic spots.
As a high specific energy lithium-ion power battery, from the perspective of basic materials, in addition to the diaphragm, other key materials in China have been localized, and regardless of scale and product stability, they can meet the technical requirements of lithium-ion power battery industrialization. However, in the field of new materials research, it is obviously lagging behind other countries, which will restrict the long-term development of the lithium battery industry from a long-term perspective. From the perspective of industrialization, companies should make great efforts to solve two key technologies: One is battery safety performance, and the safety of the power supply system must be ensured in the case of short-circuit, collision and extrusion. The positive electrode materials used today have certain safety issues, and each company adopts a comprehensive system approach (functional electrolyte, battery pretreatment process, power management system, etc.) to ensure the safety of the power supply system. The rise of lithium iron phosphate cathode materials provides a reliable guarantee for the solution of the above-mentioned problems. Although its density and conductivity are lower than other cathode materials, from the perspective of power supply type, it still has obvious advantages compared with lead acid and nickel hydrogen. The second is the cycle life. The battery performance should be able to charge and discharge 1200 times. The general family car is scrapped for 15 years. The lithium-ion battery can travel 150km on a single charge and charge 1200 times. It can be used for 15 years after including the capacity degradation.
The solution of the above two key technologies will lay a solid foundation for the industrialization of pure electric vehicles.