Amorphous lithiophilic cobalt-boride@rGO interlayer for dendrite-free and highly stable lithium metal batteries

Abstract

Lithium metal batteries (LMBs) are recognized to be crucial for secondary battery technology targeting electric vehicles and portable electronic devices. However, the undesirable growth of lithium dendrites would result in reduced capacity, short-circuit, and overheating, seriously hindering the practical applications of LMBs. To address this issue, a neoteric lithiophilic interlayer on a commercial polypropylene separator is presented for the first time, which is constructed by amorphous CoB nanoparticles decorated reduced graphene oxide nanosheets (CoB@rGO). Density Functional Theory calculations and experimental analysis reveal remarkable lithiophilicity features for CoB@rGO and provide multiple Li deposition sites and improved electrolyte wettability, which facilitates the formation of durable solid electrolyte interphase (SEI), reduces side reactions, and improves Li⁺ flux regulation for long-term cycling stability in LMBs. Taking advantage of these merits, the symmetric Li//Li cell with CoB@rGO/PP separator exhibits stable cycling for up to 1600 h at 1 mA cm⁻² with 1 mAh cm⁻². Employed with CoB@rGO separator, the Li//LiFePO₄ full cell with a high LiFePO₄ loading of 11 mg cm⁻² delivers a high initial specific capacity of 115.3 mAh g⁻¹ and a low decay rate of 0.08% per cycle after 200 cycles even at a high rate of 2C.