New power battery will become the core of the future of China's new energy vehicles

In China, as one of the core components for the development of electric vehicles, power batteries have always been a hot spot in the field of battery research. In the key national special research and development plan for new energy vehicles launched in 2016, Hong Li, researcher of the Clean Energy Laboratory of the Institute of Physics, Chinese Academy of Sciences, is responsible for the “Long-term Power lithium battery New Materials and New System Research” project, aiming to develop high energy, high density, high-safety lithium battery to improve the cruising range of electric vehicles, the project proposed to study lithium-ion batteries, semi-solid lithium-sulfur batteries, solid-state lithium-air batteries, three long battery lithium batteries will become the future of China's new energy vehicles core.

Challenge battery limit energy density

“Improving the energy density of the power battery cell to reach 400Wh/kg or more will help to significantly improve the driving range of the electric vehicle. Take the Beiqi EV200 as an example, 400Wh/kg battery core, which is equivalent to the energy density above 800Wh/L. There is a battery pack volume and a power consumption of 100 kilometers per ton. The first charge can not only last for 620 kilometers; it can also reduce the cost and extend the service life, and solve the big difference between the current performance of electric vehicles and fuel vehicles." Recently, Li He said in an interview with the reporter.

As an important part of the overall layout of the national new energy vehicle power battery research and development, the task of the project is to develop a new type of battery with energy density above 400Wh/kg at the forefront of the industry chain, and to recognize and key the key basic scientific issues of accumulating high energy density batteries. Technology, and provide important reference and guidance for enterprises to develop 300Wh/kg batteries simultaneously.

The R&D team of “Study on New Materials and New Systems for Long Endurance Power lithium batteries” is responsible for challenging the ultimate energy density of batteries in this project.

Mass production cell energy density 300Wh/kg can be realized

The reporter found from the public research and development program declared by the company that for the 300Wh/kg lithium-ion power battery route, the project team chose high-nickel positive electrode and nano-silicon carbon negative electrode.

"From the recent progress, the technical indicators of mass production of cell core energy density of 300Wh / kg can be achieved." Li said.

In the recent research on new system batteries, the lithium-rich material used in the R&D team of “Long-life lithium-ion battery new materials and new systems research” is the positive electrode, and the energy density of the silicon-carbon material as the negative electrode reaches 348Wh/kg. The specific energy of the lithium-rich material is positive electrode, the lithium metal is the negative electrode reaches 573Wh/kg, the specific energy of lithium-sulfur battery reaches 600Wh/kg, and the specific energy of the primary lithium-ion battery reaches 780Wh/kg.

“The development of high energy density batteries over 300Wh/kg, the negative electrode containing lithium metal is an important common technology. Some research teams have proposed using solid electrolytes or mixed solid-liquid electrolytes to solve the main problems faced by batteries using or containing lithium metal anodes. Technical challenges," Li said.

In November 2013, the Chinese Academy of Sciences laid out the Strategic pilot project of the Chinese Academy of Sciences, which also supported the development of solid-state batteries. Three of the teams made progress in polymer, sulfide and in-situ solid-state technology.

Clear technical route but still facing challenges

"In the soft-packed battery of liquid electrolyte lithium-ion battery currently developed and produced, the weight percentage of liquid electrolyte is generally 15% - 25%, and the negative electrode is carbon, silicon, etc. In the long run, it is necessary to develop an all-solid metal lithium battery and a negative electrode in the long run. Contains lithium metal, the battery does not contain any liquid," Li said.

Although the technical route is clearer, it is currently facing great challenges. Li Wei said that from the development of mixed solid-liquid electrolyte batteries and all-solid metal lithium battery industry, it is necessary to focus on the development of solid electrolytes and metallic lithium materials to solve the problem of interface ion and electron transport, volume deformation and thermal stability. Most manufacturing equipment can be realized by using existing lithium ion batteries and manufacturing equipment of the primary metal lithium battery industry.

In addition, production environment control technologies such as drying rooms for large-scale production of lithium metal batteries have also been mastered. Despite the development of hybrid solid-liquid electrolyte batteries and all-solid metal lithium batteries, there are many scientific and technological challenges, including cost control challenges.

"As long as we thoroughly study the basic science problems and put forward feasible and creative comprehensive solutions, even if the difficulties are serious, it is full of hope."Hong Li said.

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