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

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 Na₃ V₂ (PO₄ )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.