A highly effective and controllable chemical prelithiation of Silicon/Carbon/Graphite composite anodes for lithium-ion batteries

Chemical prelithiation has become an increasingly popular method for compensating the initial irreversible capacity loss of lithium ion batteries and improving their initial Coulombic efficiency (ICE). For composite anode materials composed of silicon, amorphous carbon and graphite (SCG), pre-embedding Li+ into all three components simultaneously by chemical prelithiation is challenging because of different activation potential. In this study a chemical prelithiation method using lithium-biphenyl (Li-Bp) as the lithiation reagent and a 2-methyl tetrahydrofuran (2-meTHF) solution as the reducing solvent is designed to enhance the ICE for SCG anodes. The prelithiation reagent by mixed with Li-Bp combined 2-meTHF facilitates the formation of a stable solid electrolyte interface (SEI) film composed of Li2O/Li2CO3 and forms LixSiy alloy. The ICE of prelithiated SCG in half-cell format can be increased from 76.8% to 93.98% when prelithiated twenty minutes (SCG-20). When matched with a LiFePO4 cathode, the coin full cell with prelithiated SCG exhibits an improved ICE from 38.92% to 56.88% and cycling performance than the pristine cells. This work highlights the promise of adopting chemical prelithiation for composite anodes to achieve practical high-energy batteries.