Electrochemically prelithiated carbon anodes with regulated Na-ion intercalation behaviours for advanced sodium-ioni energy storage devices

Sodium-ion capacitors (SICs) have long been pursued as economically favorable alternatives to their well-developed lithium-ion counterparts. However, their commercialization suffers from the immature pre-sodiation technology in existence, primarily due to the increased cost and risk invoked by the use of highly reactive metallic sodium and sodium containing additives as sodium sources. Herein, we uncover a unique approach based on the use of prelithiated carbon as the anode for SICs. The prelithiated hard carbon anode with the preformed solid-electrolyte-interphase (SEI) layer can effectively compensate the large irreversible capacity loss and greatly improve the initial coulombic efficiency of SICs. Besides, the preformed Li-based SEI layer is effective in controlling the Na-ion intercalation behavior of the carbon anode, as confirmed by the reversible capacity that is mainly contributed by the extended slope region without the low-potential plateau region, thus avoiding the safety issues from Na metal plating. These features endowed by the pre-lithiation strategy enable us to use a slope region-dominated soft carbon anode for high-safety SICs with high capacity and superior rate capability. This work possesses far-reaching potential to implant the mature pre-lithiation technology into sodium-ion energy storage systems to resolve the scientific bottleneck from the immature pre-sodiation technology.