Research progress in lithium metal battery -Lithium - Ion Battery Equipment

New progress in research field of lithium metal battery -Lithium - Ion Battery Equipment

Supported by the general program of the National Natural Science Foundation of China, the Young Talents Promotion Program of the Chinese Association for Science and Technology and the Science and Technology Innovation Program of Beijing University of Technology, the research team of Huang Jiaqi, a special researcher of the Institute of Frontier and Cross cutting Sciences of Beijing University of Technology, has made new progress in the research of high safety lithium metal anode in the next generation of high energy density lithium metal ion batteries. Recently, relevant research achievements were published online in Advanced Functional Materials (impact factor 12.124) on January 8, 2018 under the title of "Artificialsoft – rigid protective layer for dendrite freelithium metalanode".(Lithium - Ion Battery Equipment)

Lithium metal is considered to be one of the high specific energy cathode materials with development prospects because of its extremely high theoretical specific capacity (3860mAh? 1) and negative electrode potential (? 3.045V vs. standard hydrogen electrode). However, the practicability of lithium metal electrode is limited by lithium dendrite growth and low cycle efficiency. Lithium metal is a highly active metal. When it contacts with electrolyte, it forms a solid electrolyte interface with complex structure and composition. It is difficult to maintain the stability of the interface in the electrochemical reaction process. Therefore, the uneven deposition of lithium ions at the interface is prone to lead to needle like, dendritic and mossy lithium deposition. On the one hand, the growth of lithium dendrites will pierce the membrane and cause battery short circuit when contacting with the positive pole, resulting in potential safety hazards; On the other hand, it also increases the contact area between lithium metal and electrolyte, which increases the side reactions and further reduces the cycle efficiency of the battery.

In order to build a stable metal lithium/electrolyte interface and regulate the uniform deposition of lithium, the research group proposed to use inorganic LiF as the rigid component and PVDF-HFP polymer as the flexible component to build a "rigid flexible" composite film to stabilize the interface between metal lithium and electrolyte during the electrochemical cycle. Among them, the flexibility and scalability of flexible polymer supply can withstand the interface fluctuation in the process of lithium metal electrode deposition/dissolution, while the introduction of rigid components can further improve the mechanical modulus of the modified layer, thereby inhibiting the growth of lithium dendrites and achieving uniform lithium deposition. After introducing this interface modification layer with good deformation performance, high mechanical modulus and ionic conductivity into button cell, the cycle life and cycle stability of Li Cu half cell and Li Li symmetric cell are significantly improved; In the full battery test matched with lithium iron phosphate cathode, the cycle life of the battery modified by the composite layer was increased by 2.5 times.



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