Hard carbon with an opened pore structure for enhanced sodium storage performance

The pore structure of hard carbon has a significant impact on its Na+ storage capacity. Herein, a waste wood-derived hard carbon with opened pores (OP-HC) was fabricated with polyvinyl pyrrolidone (PVP) as an additive. Ex situ SAXS and HR-TEM testing results indicate that OP-HC with opened pores and enlarged d002 interlayer spacing facilitates the reversible (de)sodiation of Na+ ions. In situ TEM and XRD testing results demonstrate that OP-HC shows excellent structure stability during the (de)sodiation process. Thus, OP-HC delivers a high reversible charge capacity of 350.7 mA h g-1 at 0.05 C and an ultra-high initial Coulombic efficiency (ICE) of 94.9%. Moreover, OP-HC exhibits excellent cycling stability, and the assembled 18650 full cell with an OP-HC anode can achieve a high capacity retention of 94.5% after 400 cycles at 1.0 A. The excellent electrochemical performance and deep insights into OP-HC with opened pores and increased d002 interlayer spacing offer a new strategy to design high-performance HC anodes for SIBs. OP-HC shows a high specific capacity of 350.7 mA h g-1 with ultra-high ICE. These results are attributed to its opened pore and enlarged d002 interlayer spacing, which can enhance the reversibility of Na+ adsorption, intercalation and filling process.