A Bifuctional Presodiation Reagent for Hard Carbon Anodes Enhancing Performance of Sodium-Ion Batteries

As the benchmark anode material for sodium-ion batteries, hard carbon (HC) is still confronted by unsatisfactory initial Coulombic efficiency and an unstable solid electrolyte interphase (SEI), which degrade the energy density and cycling performance. Herein, we demonstrate the first-time application of sodium alkoxyaluminum hydride (RA) as a bifunctional presodiation reagent for the HC electrode. By driving the homogeneous accommodation of Na into the HC electrode and concurrently inducing the formation a passivative Al 2 O 3 nanolayer, electrolyte decomposition on the HC anode surface and consumption of active Na are substantially alleviated, resulting in higher energy density and cycling reversibility of a Na 3 V 2 (PO 4 ) 3 ||HC full cell. In addition, the in situ surface modification of a passivative Al 2 O 3 nanolayer also mitigates the sensitivity of the presodiated HC to dry air. This work highlights a bifunctional reagent realizing in situ HC anode surface modification and Na compensation toward long-lifetime sodium-ion batteries with higher energy density.