Cs-based artificial SEI enable high voltage Li metal battery with soft-matter electrolyte

Soft-matter electrolytes have garnered significant attention due to their improved safety features, rendering them viable options for the creation of Li metal batteries with high energy densities. However, establishing effective interfacial contact between the electrodes and soft-matter electrolyte remains a significant challenge, necessitating modifications at the interface. In this study, we design an artificial composite electrolyte interphase (PEG-Cs SEI) on the surface of the Li metal anode to improve ion transport between the soft-matter electrolyte and Li metal. The PEG-Cs SEI layer exhibits high flexibility and mechanical strength, effectively mitigating the lithium dendrite growth and volume expansion. As a result, Li||Li cells assembled with PEG-Cs SEI-modified lithium metal anodes exhibit stable performance for more than 1700 h, maintaining small overpotential even at high current densities and capacities (2.45 mAh cm −2 ). With a LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622) cathode, the battery shows a capacity up to 182 mAh g −1 at first discharge with cut-off voltage of 4.5 V. Furthermore, in a pouch cell configuration, the battery achieves 100 % capacity retention over 90 cycles and successfully passes safety tests, without fire or smoke. Combining the modified lithium metal anode with soft-matter electrolytes paves a promising way for the effective implementation of high-energy-density Li metal cells.