Introducing the Solvent Co‐Intercalation Mechanism for Hard Carbon with Ultrafast Sodium Storage

Abstract As the most successful anode material for sodium‐ion batteries, hard carbon has attracted extensive attention from researchers. However, its storage mechanism is still controversial. In this paper, a solvent co‐intercalation mechanism into hard carbon is proposed and is proved by in situ XRD and ex situ TEM XPS results successfully. Thanks to the co‐intercalation of solvent, the platform capacity of hard carbon maintains well at very high current densities. It can even exhibit 245 mAh g −1 at 5 A g −1 , which is the best rate performance obtained for hard carbon anode as far as it is known. The full battery assembled with Na 3 V 2 (PO 4 ) 3 has a high energy density of 157 Wh kg −1 at 3800 W kg −1 (relative to the electrode). This finding brings new insights with regard to the design of hard carbon materials and sodium storage mechanisms.