Lithium‐Pretreated Hard Carbon as High‐Performance Sodium‐Ion Battery Anodes

Hard carbon (HC) is the state‐of‐the‐art anode material for sodium‐ion batteries (SIBs). However, its performance has been plagued by the limited initial Coulombic efficiency (ICE) and mediocre rate performance. Here, experimental and theoretical studies are combined to demonstrate the application of lithium‐pretreated HC (LPHC) as high‐performance anode materials for SIBs by manipulating the solid electrolyte interphase in tetraglyme (TEGDME)‐based electrolyte. The LPHC in TEGDME can 1) deliver > 92% ICE and ≈220 mAh g−1 specific capacity, twice of the capacity (≈100 mAh g−1) in carbonate electrolyte; 2) achieve > 85% capacity retention over 1000 cycles at 1000 mA g−1 current density (4 C rate, 1 C = 250 mA g−1) with a specific capacity of ≈150 mAh g−1, ≈15 times of the capacity (10 mAh g−1) in carbonate. The full cell of Na3V2(PO4)3‐LPHC in TEGDME demonstrated close to theoretical specific capacity of ≈98 mAh g−1 based on Na3V2(PO4)3 cathode, ≈2.5 times of the value (≈40 mAh g−1) with nontreated HC. This work provides new perception on the anode development for SIBs. Hard carbon (HC) with high initial Coulombic efficiency (ICE) and good rate capability for sodium‐ion batteries is enabled by lithium‐pretreatment in tetraglyme electrolyte. The lithium‐pretreated HC can demonstrate >92% ICE and ≈150 mAh g−1 specific capacity at 4 C rate (1 C = 250 mA g−1), ≈15 times of the capacity (10 mAh g−1) in carbonate, along with good full cell performance.