(Digital Presentation) A Polymeric/Inorganic Composite Coatings on the Separator for High-Energy Lithium Metal Battery

Abstract

Lithium metal (Li) is a highly promising anode for next-generation rechargeable due to its high specific capacity (3,860 mA/g) and low negative electrochemical potential (-3.040 V vs. the standard hydrogen electrode). However, the issues such as high reactivity with electrolyte, infinite volume expansion, and uneven Li plating/stripping, cause low Coulombic efficiency, unstable growth of the solid-electrolyte interphase (SEI), and lithium dendrites. SEI plays an important role in the stabilization of lithium metal anodes in rechargeable batteries. Here we report a polymeric inorganic composite coatings (PICC) on the Celgard separator to regulate the Li-ion transport during charge/discharge of the battery. Such coatings enable uniformly deposition of Li, form a stable SEI film and in turn improve the electrochemical performance of the rechargeable batteries. Firstly, poly(vinylidene fluoride) (PVDF) and Li6.03La3Zr1.75Nb0.25Al0.24O12 (LLZO) were mixed at a mass ratio of 1:2, 1:1 and 1:2 in DMF, respectively. Afterwards the mixtures were coated onto the Celgard separator using doctor blades. In the carbonate-based electrolyte, the cycle life of Li‖Cu batteries with coating (PVDF:LLZO=1:2) increases from 30 cycles for uncoated batteries to 120 cycles of and a high Coulomb Efficiency of 96% is achieved. Moreover, when a high mass loading of 15 mg/cm2 NCM811 is chosen as cathodes, the Li‖NCM811 batteries using the PICC exhibit decent rate and cycling performance. After 100 cycles, the capacity retention at 0.2C of 94% is obtained, and the specific capacity is still 191 mAh/g. These results indicate that PICC can improve the electrochemical performance of Li anodes for high-energy rechargeable lithium metal batteries.