The exhausted graphite from spent Li-ion batteries is recycled and reused as a favorable anode for Na/K-ion batteries, and the insights into structural de-/intercalation model are realized.

Hard carbon is regarded as a promising anode material for sodium‐ion batteries (SIBs). However, it usually suffers from the issues of low initial Coulombic efficiency (ICE) and poor rate performance, severely hindering its practical application. Herein, a flexible, self‐supporting, and scalable hard carbon paper (HCP) derived from scalable and renewable tissue is rationally designed and prepared as practical additive‐free anode for room/low‐temperature SIBs with high ICE. In ether electrolyte, such HCP achieves an ICE of up to 91.2% with superior high‐rate capability, ultralong cycle life (e.g., 93% capacity retention over 1000 cycles at 200 mA g−1) and outstanding low‐temperature performance. Working mechanism analyses reveal that the plateau region is the rate‐determining step for HCP with a lower electrochemical reaction kinetics, which can be significantly improved in ether electrolyte.

Although ether-based electrolytes have been extensively applied in anode evaluation of batteries,a nodic instability arising from solvent oxidability is always at remendous obstacle to matching with high-voltage cathodes.H erein, by rational design for solvation configuration, the fully coordinated ether-based electrolyte with strong resistance against oxidation is reported, whichr emains anodically stable with high-voltage Na 3 V 2 (PO 4 ) 2 O 2 F( NVPF) cathode under 4.5 V (versus Na + /Na) protected by an effective interphase.T he assembled graphite//NVPF full cells displays uperior rate performance and unprecedented cycling stability.Beyond that, the constructed full cells coupling the high-voltage NVPF cathode with hardc arbon anode exhibit outstanding electrochemical performances in terms of high average output voltage up to 3.72 V, long-term cycle life (such as 95 %c apacity retention after 700 cycles) and high energy density (247 Wh kg À1 ). In short, the optimizede ther-based electrolyte enriches systematic options,t he ability to maintain oxidative stability and compatibility with various anodes,e xhibiting attractive prospects for application.

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