Ultrathin Bilayer of Graphite/SiO_2 as Solid Interface for Reviving Li Metal Anode

摘要

Lithium metal anodes are expected to drive practical applications that require high energy-density storage. However, the direct use of metallic lithium causes safety concerns, low rate capabilities, and poor cycling performance due to unstable solid electrolyte interphase (SEI) and undesired lithium dendrite growth. To address these issues, a radio frequency sputtered graphite-SiO2 ultrathin bilayer on a Li metal chips is demonstrated, for the first time, as an effective SEI layer. This leads to a dendrite free uniform Li deposition to achieve a stable voltage profile and outstanding long hours plating/stripping compared to the bare Li. Compared to a bare Li anode, the graphite-SiO2 bilayer modified Li anode coupled with lithium nickel cobalt manganese oxide cathode (NMC111) and lithium titanate shows improved capacity retention, higher capacity at higher rates, longer cycling stability, and lower voltage hysteresis. Graphite acts as an electrical bridge between the plated Li and Li electrode, which lowers the impedance and buffers the volume expansion during Li plating/stripping. Adding an ultrathin SiO2 layer facilitates Li-ion diffusion and lithiation/delithiation, provides higher electrolyte affinity, higher chemical stability, and higher Young's modulus to suppress the Li dendrite growth.