　　 During the 2008 Beijing Olympic Games, 50 electric buses were put into operation in the Olympic Village. This is the earliest large-scale application of electric buses in China and the first large-scale application of lithium battery electric buses in the world. Today, electric buses have been more developed, mainly including pure electric buses and plug-in/extended hybrid buses. Among them, the pure electric bus technology model also includes the battery quick change mode, the vehicle fast charge mode, the vehicle slow charge mode, the dual source system online charge mode and so on.
Huang Xuejie, a laboratory researcher at the Institute of Physics of the Chinese Academy of Sciences, told reporters that although current policies for electric buses in China are based on plug-in/extended hybrid buses, the technical model of pure electric buses is also due to policy, technology, and market factors. In the continuous development process. The electric bus used in the Olympic Games uses battery quick-change technology. At present, the fast-charging mode of the vehicle is applied in some areas such as Shanghai and Chongqing, but the application of the slow-charge mode of the vehicle is relatively wider. In addition to these, the technology of dual-source online charging mode is also in the process of rapid development.
“Regardless of which mode of electric bus technology is used, the role of the battery can not be ignored.†Huang Xuejie said that different technical models have different battery requirements. For example, dual-source online charging mode, this technical route puts forward higher requirements for battery life. So, what is the current situation of the battery development of China's electric buses? During the "13th Five-Year Plan" period, what is the development direction of the battery?
　　 Lithium-ion batteries support the development of electric buses in China
At present, in China, whether it is a plug-in passenger bus, a pure electric bus, or a dual-source electric bus, lithium-ion batteries are undoubtedly the “protagonists.†China’s electric car batteries are still stuck in the development stage of lithium-ion batteries.
Lithium-ion batteries work by relying on the movement of lithium ions between the positive and negative electrodes, that is, during charging and discharging, Li+ reciprocates between the two electrodes. Generally, a material containing a lithium element is used as an electrode. Since many materials can be used for a lithium ion battery, there are many kinds and uses of lithium ion batteries. To meet the power battery material, it is necessary to satisfy the following two conditions: First, the battery safety factor is higher, and secondly, the cost of the material is low due to the large amount of battery used in the vehicle. After considering these two conditions, only materials such as lithium manganate, lithium iron phosphate, ternary materials, and high voltage lithium nickel manganese spinel can be used as car batteries.
Huang Xuejie said: "In all applicable materials, lithium iron phosphate lithium batteries support the demonstration operation of China's new energy vehicles. Although lithium iron phosphate in some aspects is inadequate, but it has high safety, long life, relatively low cost Low-level features, in addition, due to the international protection of lithium iron phosphate patents to China's 'open side,' thus giving China's lithium iron phosphate lithium battery industry development opportunities in China's battery industry and manufacturing level In the lower stage, Lithium-ion lithium-ion batteries have maintained the operation of large-scale electric vehicles including electric buses in China."
At present, in China's pure electric passenger car brand, Zhongtong pure electric LCK6660EVG uses lithium iron phosphate battery. After market feedback, the battery type has the advantages of high charging and discharging efficiency, high safety, and high temperature resistance. In addition, the Yutong pure electric bus E series includes E7, E8, E10, E12 and other full range of pure electric buses from 7 meters to 13 meters. It uses the batteries of domestic famous battery manufacturer ATL, and is also a lithium iron phosphate battery technology. route.
In addition to China Tongyu and Yutong, the Haier KLQ6129GEV pure electric city bus uses a lithium-ion battery pack and has good dynamic performance. It can be charged for more than 180 kilometers after charging for 4 to 5 hours. Meet the needs of city buses.
　　 According to different electric bus technology modes, choose different materials to constitute the battery
　　 Lithium-ion batteries as the main force of the current electric car battery, its application is not generalized. For example, when using a hybrid bus, the positive and negative materials must be adjusted. At present, lithium-ion battery cathode materials use lithium iron phosphate, graphite materials used more negative materials, this composition will affect the battery's fast charge performance. Therefore, for fast-charging passenger cars or dual-source passenger cars, the negative electrode of lithium-ion batteries should be filled with more than half of hard carbon materials, and the charging performance will be greatly improved.
On the market, Daikin Long pure electric bus XMQ6661AGBEV1 is a fast-charging lithium battery . It adopts a fast charging method. The single charging mileage is 100km, and it is full for 15 minutes. The actual single-use charging is done once or back and forth, charging for 5-7 minutes. Lithium battery life of up to 6--8 years, so the vehicle life cycle without replacement.
"In the face of different vehicle application requirements, we should adjust the positive and negative materials of the battery to meet its actual charging requirements." Huang Xuejie said, "At present, there are also successful cases in the world, through the adjustment of positive and negative materials, let The battery's charge and discharge meets the needs of hybrid buses."
In addition to the reasonable deployment of battery materials, the hybrid energy storage system that combines the supercapacitor energy storage and the supercapacitor and lithium battery energy storage technology pioneered by Golden Trip has also been recognized by the industry and is currently on the market. It has been widely promoted, and its pure electric Costed model XML6700JEV has got a good response from the market.
　　 Battery Application Environment "Heat Management" Can Affect Battery Life
Huang Xuejie introduced that the battery performance will be affected by the battery application environment. A well-known battery company in France tested the battery application environment and performed 6000 cycles at room temperature. The battery capacity can still reach 80%, but if the temperature is raised to 45 degrees, about 1000 cycles will occur, the capacity will be Drop to 80%, cycle to 2000 or so, it will drop to 70%.
Around 2008, China made a technological breakthrough in the lithium iron phosphate battery, and the product gradually matured into the international market. However, after years of development, the application of batteries to some electric buses has still not reached the best level. One of the most important reasons is that proper thermal management control has not been implemented.
At present, there are many electric buses in China, especially pure electric buses , which operate at high ambient temperatures but do not have reasonable thermal management. After three years of use, the capacity of lithium iron phosphate batteries is basically around 60%, and some are even lower. This has also affected the image of pure electric buses in the hearts of users, causing difficulties in promotion. "The lithium iron phosphate battery can only meet the demand for pure electric buses only if strict operating control is required to control the maximum operating temperature," said Huang Xuejie.
　　 During the "Thirteenth Five-Year Plan", a number of initiatives to promote the development of electric vehicle batteries
Fang Jianhua, general manager of Hefei Guoxuan Hi-Tech Power Co., Ltd., believes that the current production-type power battery company represented by Guoxuan has a stable technology level and has basically met the needs of current bus and bus operations. Fang Jianhua introduced that Guoxuan promoted “technological development†with “mass production applicationsâ€, and mass production applications also formed the best test for reliability, consistency, stability, and safety of batteries.
Of course, as a new high-tech industry, power batteries are faced with more room for improvement or development challenges. “Now vehicle companies and operating customers continue to make higher demands on batteries. This is the driving force behind the advancement of battery technology. Based on this, our related companies must effectively coordinate cost control with practical prices to promote the industrialization of new energy buses. The process," said Fang Jianhua.
During the “Thirteenth Five-Year Plan†period, the state’s development goal for electric passenger car batteries is to reduce battery bricks, increase battery utilization, and develop high-power and long-life batteries. Huang Xuejie introduced that at present, the specific energy of high-power and long-life batteries in China can reach 50Wh/kg, and some technologies can reach 100Wh/kg. It is estimated that by 2020, the passenger car's battery specific energy can reach 300Wh/kg, while passenger car power battery will reach 150Wh/kg. The development of high-power, long-life batteries will have a positive impact on the development of new energy buses.
Huang Xuejie also revealed that under the support of the special funds of the Ministry of Finance, during the “Thirteenth Five-Year Plan†period, the Institute of Physics of the Chinese Academy of Sciences will establish a national battery comprehensive analysis and test platform. This platform will be open to the world and will be used for battery products of various research institutions and companies. In this way, the battery development level of electric vehicles in various countries will be better , especially the development of electric vehicle batteries in China will play a positive role in promoting.
Power battery manufacturing engineering capabilities, including manufacturing equipment and process capabilities, are the basis for determining a country's battery development level. “The process and equipment for power battery industrialization has always been a shortcoming for China’s industrial development. In the past, in order to produce good batteries, it was necessary to import relevant production equipment from abroad, which not only increased the cost of batteries, but also caused difficulties for large-scale production.†Huang Xuejie Said that during the 13th Five-Year Plan period, in addition to the establishment of the test platform, relevant departments will also increase the research level of power battery technology and equipment. With the support of the Ministry of Industry and Information Technology and the Ministry of Finance, the Institute of Industrial Technology of the Chinese Academy of Sciences has established a battery technology. And equipment research platform to better serve our country's power battery industry."
In addition to national efforts, companies are also making unremitting efforts to improve. Fang Jianhua said that with the intensification of market competition, power battery supply will tend to be intensified, and the competition for large-scale operations, mass production, and cost control capabilities will become stronger. At present, Guoxuan has established a systematic technology research and development system, improved the customization of process equipment, achieved the goals of production generation, reserve generation, and R&D generation, ensuring the continuous and reliable progress of battery R&D technology and the continuous improvement of manufacturing engineering capabilities.
On the basis of the existing battery development level, the “Thirteenth Five-Year Plan†attaches importance to electric vehicles, especially electric vehicle batteries, and the efforts of companies like Guoxuan will usher in a new development for the development of China’s power batteries. "spring". We believe that during the “Thirteenth Five-Year Plan†period, passenger car batteries will usher in a mature period of development. At the same time, China’s pure electric buses will usher in a new round of development boom.
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