Full process control to ensure the safety of lithium battery

  Lithium battery production line. Photo courtesy of vision china

  ◎ Chen Ke Our reporter Changfeng Wu

  With the popularity of mobile phones and electric cars, lithium batteries are playing an increasingly important role in people’s lives. However, the fire and explosion accidents of electric vehicles and energy storage power stations caused by the inherent thermal runaway of lithium batteries also make the safety of lithium batteries a problem that cannot be ignored. This is also a long-term technical challenge faced by the lithium battery industry.

  At the Sichuan Science and Technology Awards Conference held recently, the team of Professor Xiang Yong from the University of Electronic Science and Technology of China, as the first completion unit, won the first prize of Sichuan Science and Technology Progress Award for the project "Key Technologies and Applications of Safety Control of Lithium Batteries Based on Multi-field Perception and Independent Flame Retardation". "How to improve the safety of lithium batteries and reduce the risk of overheating and explosion of batteries is a must." Xiang Yong said that in order to overcome this hurdle, he and his team have been exploring and struggling for more than ten years.

  Overcoming three major problems of lithium battery safety

  "Since 2012, we have gradually developed a complete electrochemical Qualcomm characterization platform and made a series of achievements in the research of lithium battery electrolytes, electrode materials and packaging materials." Xiang Yong said that he and his team began to try to apply the electrochemical Qualcomm characterization technology to the research on the dynamic change of the safety performance of lithium batteries in the whole life cycle, but during the research and development process, they found that the parameters monitored by the existing characterization methods were not enough to directly reflect the thermal runaway risk of lithium batteries.

  In Xiang Yong’s view, the thermal runaway process of lithium batteries involves manufacturing defects, aging and deterioration, management failure, abnormal environmental conditions and other factors, as well as manufacturing, storage and transportation, service and other links, and many technical problems need to be solved urgently.

  "There are three main problems to be overcome to solve the safety management and control of lithium batteries throughout their life cycle." Xiang Yong told Science and Technology Daily that real-time monitoring of thermal runaway of lithium battery is the first difficult problem. The difficulty lies in that conventional sensors cannot be embedded in the battery, and external signal sensing can only be relied on to infer the safety state of the battery, which will lead to inaccurate monitoring data.

  "Early warning and protection of lithium battery thermal runaway process is the second problem." Xiang Yong said that the measures taken after the thermal runaway of lithium batteries are usually "one size fits all", that is, shutting down the whole power supply system, which can not fundamentally eliminate safety accidents and will damage the service reliability of the power supply system.

  "The combustion blocking after the lithium battery caught fire is the third problem." Xiang Yong said that in the electrolyte of lithium battery, the organic solvent will produce flammable and explosive components when it is decomposed by heat, which will become the root cause of the fire and explosion of lithium battery after being mixed with oxygen. Therefore, once the lithium battery catches fire, it is extremely difficult to block the combustion.

  After clarifying the R&D problems and selecting the R&D direction, Xiang Yong team, together with Sichuan Institute of Safety Science and Technology, Sichuan Institute of Product Quality Supervision, Inspection and Testing, Sichuan Branch of China Tower Co., Ltd., Southwest Petroleum University and other Industry-University-Research companies, conducted in-depth research and exploration on the monitoring and control of the safety status of lithium batteries throughout their life cycle. Under the leadership of Xiang Yong, the participating research institutes have made concerted efforts to tackle key problems, giving full play to their respective strengths in the fields of theoretical research, technology development and application promotion.

  "We have successfully developed the in-situ preparation integration technology of multi-parameter thin film sensor and lithium battery current collector, realized the integrated integration, and solved the problem of sensor ‘ Buried, measured accurately, transmitted, with little influence ’ Key technical challenges. " Xiang Yong said that the team independently developed a special algorithm for artificial intelligence electrochemical countermeasure migration learning, and combined with the precise design model developed in the early stage, the accuracy of fault battery identification was improved to 98.6% in one fell swoop; Self-developed Qualcomm electrolyte preparation and screening technology and related devices improve the screening efficiency by 100 times, and realize the rapid optimization of the flame retardant and electrochemical properties of electrolyte.

  On April 24th, 2022, an expert group headed by Academician Wu Feng, a famous lithium battery expert, evaluated the technical achievements of lithium battery safety series developed by Xiang Yong team. The expert group agreed: "This achievement belongs to the international frontier technology field, and its indicators, model prediction accuracy and electrolyte self-extinguishing time are at the international leading level."

  Accumulated economic benefits exceeded 1 billion yuan.

  Since 2019, China Tower Energy Company has applied the project results to the power supply system of China Tower communication base station, supported the real-time online monitoring of more than 500,000 lithium batteries in the standby system of Sichuan communication base station, and warned the safety risks of lithium batteries for more than 20,000 times, with a success rate of 100%. More than 13,000 failed batteries were safely returned, and fire hazards were eliminated for more than 1,500 times, which effectively ensured the safe operation of the tower communication base station without any lithium battery thermal runaway accident.

  Shanghai Institute of Space Power Supply applied this achievement to solve the problem of sudden safety failure of lithium battery module. At present, this technology has been applied to Fengyun-4 02 satellite, new technology test satellite and other models; Sichuan Changhong Power Supply Co., Ltd. has developed a special integrated power supply with high weight ratio and high density of batteries and accessories based on the results of this project.

  In October 2019, after introducing the technical achievements of the project, Hubei Yiwei Power Co., Ltd. further developed the online capacity prediction technology of lithium batteries, and successfully applied the new technology to the transformation of existing production lines and the construction of new production lines, effectively improving the production capacity of lithium batteries.

  Xiang Yong told reporters that the popularization and application of the project results can help to develop high-safety and high-reliability new lithium battery products, eliminate hidden dangers of production safety risks, and also help to develop new lithium battery safety management system and improve the safety management and control level of lithium battery system. "Especially for lithium battery users, it can reduce the accident rate of lithium battery thermal runaway, reduce disaster losses and save operation and maintenance costs."

  The data shows that since March 2019, the achievements of this project have accumulated over 1 billion yuan in economic benefits, and produced a wide range of social benefits, playing a role in serving major and key national projects.