Sulfur‐doped hard carbon hybrid anodes with dual lithium‐ion/metal storage bifunctionality for high‐energy‐density lithium‐ion batteries

Abstract Bifunctional hybrid anodes (BHAs), which are both a high‐performance active host material for lithium‐ion storage as well as a guiding agent for homogeneous lithium metal nucleation and growth, exhibit significant potential as anodes for next‐generation high‐energy‐density lithium‐ion batteries (LIBs). In this study, sulfur‐doped hard carbon nanosphere assemblies (S‐HCNAs) were prepared through a hydrothermal treatment of a liquid organic precursor, followed by high‐temperature thermal annealing with elemental sulfur for application as BHAs for LIBs. In a carbonate‐based electrolyte containing fluoroethylene carbonate additive, the S‐HCNAs showed high lithium‐ion storage capacities in sloping as well as plateau voltage sections, good rate capabilities, and stable cyclabilities. In addition, high average Coulombic efficiencies (CEs) of ~96.9% were achieved for dual lithium‐ion and lithium metal storage cycles. In the LIB full‐cell tests with typical NCM811 cathodes, the S‐HCNA‐based BHAs containing ~400 mA h g−1 of excess lithium led to high energy and power densities of ~500 W h kg−1 and ~1695 W kg−1, respectively, and a stable cycling performance with ~100% CEs was achieved.