All‐Climate Iron‐Based Sodium‐Ion Full Cell for Energy Storage

Abstract The anode materials for sodium‐ion batteries (SIBs) such as soft carbon, hard carbon, or alloys suffer from low specific capacity, poor rate capability, and high cost. Various transition metal oxides materials possess high specific capacity and suitable working potential, however, huge volume change and unstable electrode/electrolyte interfaces limit their practical applications. Herein, an ultrathin carbon‐coated iron‐based borate, (Fe 3 BO 5 ), as an anode material for SIBs is reported. The carbon coated Fe 3 BO 5 composite as an anode material possesses a reversible specific capacity of 548 mAh g −1 with a high initial coulombic efficiency of 72.6% at a current density of 50 mA g −1 , and maintains a capacity retention ratio of 99% after 1000 cycles at 2000 mA g −1 . Moreover, this anode can work well over a wide temperature range (‐40–60 °C). Furthermore, a sodium‐ion full cell using this anode coupling with iron‐based cathode (Na 3 Fe 2 (PO 4 ) 2 (P 2 O 7 )@rGO) cathode is fabricated, which exhibits a wide operating temperature range from −40 to 60 °C with a maximum energy density of 175 Wh Kg −1 and a maximum power density of 1680 W Kg −1 . Most importantly, this full‐cell configuration is low‐cost due to its inexpensive iron based raw material for both anode and cathode.