Electroplating of Lithium-metal electrode in different electrolyte for lithium batteries

Abstract

The effect of different electrolyte additives, including lithium difluoro(oxalato) borate (LiDFOB), lithium bis(oxalato) borate (LiBOB), lithium tetrafluoroborate (LiBF₄) and lithium bis(fluorosulfonyl) imide (LiFSI), on the cycling stability of lithium (Li) metal batteries were systematically and comparatively investigated. The initial coulombic efficiency (ICE) of Li plating was found to follow the order: LiBF₄ (42.5 %) < LiFSI (45.5 %) < No additive (69.5 %) < LiBOB (76.0 %) < LiDFOB (93.2 %), indicating that the LiDFOB exhibits the highest ICE value among those tested. LiDFOB also effectively protects the surface of Li metal anode from side reactions, resulting in a capacity retention of 94.06 % after 25 cycles. Electrochemical evaluation of the Li∥NCM622 full cell with LiDFOB additive demonstrated the highest capacity retention of 94.10 % after 20 cycles. Additionally, various aspects of Li metal electroplating and stripping were examined, including electrode morphology and the properties of solid electrolyte interphase (SEI) layer on the Li electrode. A key finding is that electrolyte additives, particularly LiDFOB, play a crucial role in enhancing the SEI of Li metal, which is essential for achieving high performance in Li metal batteries.