Facile preparation of V2O3/black fungus-derived carbon composite with hierarchical porosity as a promising electrode for lithium/sodium ion batteries

Transition metal oxides are potential electrodes for lithium/sodium-ion batteries, but they are generally characterized by low electronic conductivity and a large volume change during charge/discharge. Metal oxide/bio-carbon composites have shown tremendous promise, but traditional methods for the preparation of bio-carbon-based composites are incapable of achieving high porosity and even distribution. Herein, we used a combined strategy aided by salts and ball milling to facilely prepare vanadium oxide/biomass (i.e., black fungus)-derived carbon (BFC) composites for mass production. The optimized composite (e.g., V2O3/BFC), assembled in lithium-ion batteries, offers high reversible capacity of 461.9 and 377.2 mAh g−1 after 120 cycles at 0.5 and 1.0 A g−1, and demonstrates good capacity retention after experiencing rate-capability and long-term measurements. Notably, the V2O3/BFC composite further shows good cycle stability for sodium-ion batteries, with 253.3 mAh g−1 at 0.2 A g−1 after 160 cycles. The excellent electrochemical performance of V2O3/BFC can be attributed to the simultaneous introduction of salts and ball milling in effectively cracking bulk carbon and dispersing V2O3, leading to the formation of a hierarchically porous structure with a high specific surface area and a homogeneous distribution of V2O3. Furthermore, the hierarchically porous structure favors ion/mass transport and alleviates the adverse impacts of volume expansion, while electrons are facilely transferred via the carbon framework. The work highlights a combination method that includes salts and ball milling, and the feasibility of employing natural-abundant biomass and commercial vanadium oxide for high-performance lithium/sodium-ion batteries.