Interrelation Between External Pressure, SEI Structure, and Electrodeposit Morphology in an Anode‐Free Lithium Metal Battery

Abstract

AbstractThe interrelation is explored between external pressure (0.1, 1, and 10 MPa), solid electrolyte interphase (SEI) structure/morphology, and lithium metal plating/stripping behavior. To simulate anode‐free lithium metal batteries (AF‐LMBs) analysis is performed on “empty” Cu current collectors in standard carbonate electrolyte. Lower pressure promotes organic‐rich SEI and macroscopically heterogeneous, filament‐like Li electrodeposits interspersed with pores. Higher pressure promotes inorganic F‐rich SEI with more uniform and denser Li film. A “seeding layer” of lithiated pristine graphene (pG@Cu) favors an anion‐derived F‐rich SEI and promotes uniform metal electrodeposition, enabling extended electrochemical stability at a lower pressure. State‐of‐the‐art electrochemical performance is achieved at 1MPa: pG‐enabled half‐cell is stable after 300 h (50 cycles) at 1 mA cm−2 rate −3 mAh cm−2 capacity (17.5 µm plated/stripped), with cycling Coulombic efficiency (CE) of 99.8%. AF‐LMB cells with high mass loading NMC622 cathode (21 mg cm−2) undergo 200 cycles with a CE of 99.4% at C/5‐charge and C/2‐discharge (1C = 178 mAh g−1). Density functional theory (DFT) highlights the differences in the adsorption energy of solvated‐Li+ onto various crystal planes of Cu (100), (110), and (111), versus lithiated/delithiated (0001) graphene, giving insight regarding the role of support surface energetics in promoting SEI heterogeneity.