The new solid-state battery technology can realize the "future core" of new energy vehicles

In China, power batteries, as one of the core components for the development of electric vehicles, have always been a hot topic in battery research. In the new energy vehicle special research and development program launched in 2016, the project "Research on New Materials and New Systems for Long-Range Power Lithium Batteries" led by Li Hong, a researcher at the Clean Energy Laboratory of the Institute of Physics, Chinese Academy of Sciences, aims to develop high-energy-density lithium batteries to enhance the driving range of electric vehicles. The three types of long-range power lithium batteries proposed by the project, namely lithium-ion batteries, semi-solid lithium-sulfur batteries and solid lithium-air batteries, may become the core of China's new energy vehicles in the future.

Challenge the energy density of batteries

Increasing the energy density of power battery cells to over 400Wh/kg will significantly enhance the driving range of electric vehicles. Take the BAIC EV200 as an example. A 400Wh/kg battery cell is equivalent to a volume energy density of over 800Wh/L. Keeping the current battery pack volume and power consumption per ton per 100 kilometers unchanged, a single charge can not only provide a range of 620 kilometers; It can also reduce costs, extend service life and address the significant performance gap between electric vehicles and fuel vehicles at present. Recently, Li Hong said in an interview with a reporter from Science and Technology Daily.

As an important part of the overall layout for the research and development of new energy vehicle power batteries, the task of this project is to develop new types of batteries with an energy density of over 400Wh/kg in the industrial chain, accumulate the understanding of key basic scientific issues and key technologies of high energy density batteries, and provide important reference basis and guidance for enterprises to develop 300Wh/kg battery cells simultaneously.

The R&D team of "Research on New Materials and New Systems for Long-Range Power Lithium Batteries" undertook the task of challenging the energy density of batteries in this project.

The energy density of mass-produced battery cells can reach 300Wh/kg

Reporters found from the public research and development plans submitted by enterprises that for the 300Wh/kg lithium-ion power battery route, some project teams have chosen high-nickel cathodes and nano-silicon-carbon anodes.

Judging from the progress, the technical target of achieving an energy density of 300Wh/kg for mass-produced battery cells can be realized. Li Hong said.

In the recent research on new battery systems, the R&D team of "Research on New Materials and New Systems for Long-Range Power Lithium Batteries" has achieved an energy density of 348Wh/kg for the battery cells with lithium-rich materials as the cathode and silicon-carbon materials as the anode, while the specific energy of the battery cells with lithium-rich materials as the cathode and metallic lithium as the anode has reached 573Wh/kg. The specific energy of lithium-sulfur batteries reaches 600Wh/kg. The specific energy of a single lithium-air battery reaches 780Wh/kg.

The development of high energy density batteries with an energy density exceeding 300Wh/kg, where the negative electrode contains metallic lithium, is an important common technology. Some research teams have proposed the use of solid electrolytes or mixed solid-liquid electrolytes to address the main technical challenges faced by batteries that use or contain lithium metal anodes. Li Hong said.

In November 2013, the Chinese Academy of Sciences launched the Strategic Priority Research Program of the Chinese Academy of Sciences, which simultaneously supported the development of solid-state batteries. Among them, three teams made progress in polymer, sulfide and in-situ solid-state technologies respectively.

The technical route is clear but still faces challenges

At present, in the soft-pack cells of liquid electrolyte lithium-ion batteries under development and production, the weight percentage of the general liquid electrolyte is 15% to 25%, and the negative electrode is made of carbon, silicon, etc. In the long run, the future requires the development of all-solid-state metal lithium batteries, with metallic lithium as the negative electrode and no liquid in the battery. Li Hong said.

Although the technical route is relatively clear, it is currently facing significant challenges. Li Hong said that from the perspective of developing hybrid solid-liquid electrolyte batteries and all-solid-state lithium metal batteries, it is necessary to develop solid electrolytes and lithium metal materials to solve the problems of ion and electron transfer at the interface, as well as volume deformation and thermal stability. Most manufacturing equipment can be achieved by adopting the manufacturing equipment of the existing lithium-ion battery and primary metal lithium battery industries.

In addition, the production environment control technologies such as drying rooms for large-scale production of metal lithium batteries have also been mastered. Although the development of hybrid solid-liquid electrolyte batteries and all-solid-state lithium metal batteries still faces many scientific and technological challenges, including those related to cost control.

"As long as the fundamental scientific issues are thoroughly and deeply studied and feasible, creative and comprehensive solutions are proposed, even if there are numerous difficulties, there is still hope." " Li Hong said