Enabling Long Cycling with Excellent Structure Stability for High-Nickel Layered Cathodes in Lithium Metal Batteries

Abstract

Rechargeable Li metal batteries (LMBs) constructed from Li metal and high-Ni NMCs have attracted much attention because of their high energy density in electrical vehicles. The choice of electrolyte plays a crucial role in determining the performance of Li||high-Ni NMC LMBs. In this work, we investigated the electrochemical performance and microstructure change of Li||0.7Nb-NMC 9055 LMBs using ether-based electrolyte (LiFSI–1.2DME–3TTE) and carbonate electrolyte (1 M LiPF6 in EC/DMC). The results show that ether-based electrolyte can significantly enhance the cycling life of Li||0.7Nb-NMC 9055 battery, providing a capacity of 203 mAh/g vs 179 mAh/g (carbonate electrolyte) for 150 cycles without voltage decay at C/5 charge and C/2 discharge rates. The excellent electrochemical performance (capacity and voltage) originates from the perfect structural stability confirmed by the dQ/dV versus V curves, which was further supported by electrochemical impedance spectroscopy test, showing nearly no surface charge transfer resistance increase in ether-based electrolyte, versus continuous growth in carbonate electrolyte.