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Lithium ion battery is a good choice for current electric vehicles

by:UFO      2020-01-13

The safety of power batteries is the premise for the promotion and use of electric vehicles, and the industry has been making active efforts to this end. However, since cars equipped with lithium-ion power batteries began to demonstrate and promote on a global scale, the world has always had doubts about the safety of lithium-ion power batteries, in fact, there has always been some negative information about the safety of lithium-ion power batteries for automobile batteries, while the domestic situation is more serious. So, is there an unavoidable risk in the mechanism of the safety of lithium ion power batteries? In this regard, the author has the following understanding on the safety of lithium ion power batteries through communication with relevant experts, research and development personnel and tracking and understanding of some accident cases, and shares with people concerned about battery safety:

first, in terms of electrochemistry, compared with other materials, lithium ion batteries take into account the specific energy, safety, specific power, service life and other characteristics required by electric vehicles, as well as relatively low cost, before the development of new material systems, lithium ion batteries should be a good choice for the development of electric vehicles. Judging from the development of global lithium ion power battery technology, there are theoretically solutions to the safety problem. However, to ensure the safety of vehicles equipped with lithium ion batteries, it is not only a technical problem, it is not only the problem of materials themselves and battery cells, but also the improvement of relevant research and development and manufacturing management systems, as well as the strengthening of coordination and cooperation among all parties.

Secondly, the safety of batteries is mainly manifested by combustion and explosion. The root cause of its generation mechanism is thermal runaway caused by short circuit and overcharge. Therefore, preventing thermal runaway caused by short circuit and overcharge is the main direction to solve lithium ion power batteries. The causes of short circuit include material factors, process factors, and factors such as low-temperature charging, high-current charging and discharging, and rapid attenuation of negative electrode during use. Overcharge is mainly caused by high current charging. At present, the main ways to prevent thermal runaway are: material technology, development of flame retardant diaphragm, electrolyte system, negative insulation layer, etc, the main topic is how to realize high temperature resistance, flame retardant, high strength, environmental protection, easy industrialization and low cost; In the aspect of battery core manufacturing, efforts should be made to solve consistency problems, such as dust prevention, dislocation of positive and negative poles, Burr of pole plates, electrolyte/quality uniformity, etc. , among which there are both technical problems and quality control capability of production systems; In terms of battery design, the self-excitation safety technology of the battery is developed to enable the battery to have self-protection function, such as the spontaneous charging voltage clamping technology and the spontaneous thermal control technology of the battery; In terms of battery system, develop efficient thermal management system, battery management system and high safety structure. Some of these technologies are relatively mature in the world and are applied to some battery production or vehicle loading.

third, although thermal runaway is the fundamental cause of the safety of lithium ion power batteries, its occurrence is closely related to heat production and rate, ambient temperature and humidity, in other words, it is a problem of probability. How to reduce the probability is a big challenge currently facing us. Relevant materials, batteries, batteries and vehicle enterprises must work closely together, which is of vital importance. This is because different vehicle enterprises, different vehicle models, different use conditions and environments have different requirements on the technical conditions of battery cells and battery systems, if there is no full communication and cooperation between battery enterprises and car enterprises in the vehicle development stage, it is difficult to prevent potential safety hazards of battery systems. For example, the size of the battery cell has an impact on safety. From the theory of thermal runaway, the limit of monomer capacity is confirmed, and the safety of small-capacity batteries is high (Such as below 10Ah) However, some vehicle enterprises need vehicles or designs, without fully understanding the safety characteristics of batteries and fully mastering relevant safety technologies, like buying a mobile phone battery, buying and using large-capacity batteries from battery manufacturers to form a group system lacks technical support to effectively prevent thermal runaway, resulting in frequent safety accidents.

fourth, the establishment of a cross-disciplinary power battery safety evaluation system should be accelerated. At the recent academic conference on safety technology of lithium ion power batteries held by the Chinese Academy of Engineering, Academician Chen Qingquan of the Academy of Engineering issued an appeal: The power battery safety evaluation system is the key and the most important. During the meeting, Dr. Wang Fang from the laboratory of China Automotive Technology Research Center introduced the progress of the safety testing standards for automotive power batteries led by the Ministry of Industry and Information Technology, including BMS function test, vibration test, impact test, fire test, immersion test, etc. However, some experts at the meeting suggested that in addition to the traditional test standards, it is necessary to speed up the prediction of battery safety probability and the evaluation of batteries in use, and strengthen the battery explosion after of the human body hurt very big of CO, HF (Hydrogen fluoride) Research on relevant standards for harmful gas control, and requires the joint participation of materials, batteries, and car companies to formulate and improve relevant standards, establish a systematic safety evaluation system including specifications to guide R & D and production consistency, evaluation of new batteries and batteries in use, and reduction of injuries after accidents.

as the country continues to carry out the promotion and application of new energy vehicles, the prevention and control of air pollution and the implementation of relevant urban action plans, the marketization process of new energy vehicles will accelerate, there will be more and more electric vehicles on the road, and the problem of battery safety will become more and more urgent. Research institutions, enterprises and industries should put the safety of power batteries in the first place under the guidance of relevant government departments, strengthen research and cooperation to ensure the safety of batteries, systems and vehicles and the safety of people's lives!

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