One-Step Regulation of Pore Evolution in Hard Carbon from Open to Closed for High Rate and High Plateau Capacity Sodium-Ion Storage

Abstract

For hard carbon (HC) anodes in sodium ion batteries, performance is hampered by slow kinetics at potentials below 0.1 V and the lack of facile approaches to create closed pores.This work proposes a strategy for effectively constructing closed pores through a one-step pyrolysis of white dextrin. The overall capacity was significantly enhanced, attributable to the superior stability of thermodynamic sites for Na⁺ storage enabled by a combination of moderate graphitization and an optimal pore structure. Under 10 C, it maintains high reversible specific capacity (248.4 mAh g -¹)and outstanding performance after 9000 cycles, demonstrating an exceptionally low average cyclic capacity fade of just 0.0037%, which is primarily attributed to its sufficiently large opening size of closed pores on plateau capacity at high rates.Additionally, at 10 C, the anode still has 173.38 mAh g -¹ plateau capacity, maintaining nearly 100% retention compared to the low rate plateau capacity. A comprehensive elucidation of the mechanism for closed pore generation provided by this study will significantly advance the approaches for developing HC with high capacity.