Important Progress in the Study of Interface Regulation for All-solid-state Lithium Batteries

The next generation of lithium-ion batteries for electric vehicles and mobile phones will choose all-solid-state lithium-ion batteries with higher energy density and better safety. In order to accelerate the research and development of new materials and all-solid-state lithium-ion batteries, the 13th Five-Year Plan set up the National Key Research and Development Program of Material Genome Technology for the first time. We hope to accelerate the research and development of all-solid-state lithium-ion batteries through the new concepts and technologies of high-throughput computing, synthesis, detection and database (machine learning and intelligent analysis of large data). A national key project on the research and development of all-solid-state batteries based on material genome technology was set up, which was jointly undertaken by Professor Pan Feng, School of New Materials, Shenzhen Graduate School, Peking University, as the chief scientist and led by 11 organizations.

The important part of this project includes the research and development of new solid electrolyte and solid battery materials. Solid electrolyte is mainly divided into inorganic solid electrolyte, solid polymer electrolyte and composite solid electrolyte. Traditional solid-state polymer electrolytes have low conductivity and narrow potential window near room temperature, while inorganic solid-state electrolytes have poor flexibility and large interface impedance. As a combination of the two, composite solid electrolyte not only has flexibility, but also has good conductivity at relatively low temperature, which has broad research prospects.

Professor Pan Feng's group has made important progress in the research of composite solid electrolyte and interface regulation recently. Inorganic-organic composite solid electrolyte (CSE-B-71515) was prepared by mixing inorganic solid electrolyte (Li.3Al 0.3Ti1.7 (PO4) 3), organic polyoxyethylene (PEO) and borated polyethylene glycol (BPEG) in a ratio of 7:1.5:1.5. Inorganic solid electrolytes provide channels for lithium ion and make composite solid electrolytes have high mechanical strength. Organic macromolecule PEO not only conducts lithium ion, but also plays a role in bonding ceramic particles. Organic small molecule BPEG first reduces the crystallinity of PEO, and then changes the hard contact between solid-solid interface to soft. Contact can make lithium deposit and release more uniformly on lithium metal. With the above characteristics, the electrolyte can well block the formation of lithium dendrites physically and chemically. In addition, lithium iron phosphate and lithium metal were used as positive and negative electrodes for the composite solid electrolyte at 60 degrees Celsius. The specific capacity of 158 mAhg-1 was obtained at 0.1C ratio and 94 mAhg-1 was obtained at 2C ratio. This study has important guiding value for the study of solid electrolyte.

The research was published in the latest international journal Advanced Energy Materials (Adv. Energy. Mat., 2017, 1701437, DOI: 10.1002/aenm. 201701437, with an impact factor of 16.7). The work was conducted by Professor Pan Feng and co-authored by postdoctoral Yang Luyi as the first author and team. This work is supported by the National Key Material Gene Project and Guangdong Innovation Team.

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