Tuning Microstructures of Hard Carbon Anode by Rapid Pre-foaming Strategy for Superhigh-Rate Sodium-ion Storage Performance in Low-plateau Region

Fabricating suitable microstructures containing closed pore volume, closed pore size, interlayer spacing as well as C=O content in the glucose-based hard carbon (Glu-HC) can greatly enhance its electrochemical performance in sodium-ion batteries (SIBs) at low-voltage below 0.1 V. Unfortunately, the blistering nature of D-glucose makes it difficult to regulate precisely these microstructures for achieving an excellent Na⁺ storage performance, especially at high rates. Herein, D-glucose was rational pretreated by modulating KMnO₄ addition and hot acid-washing time to promote its condensation and aromatization, and avoid a foaming phenomenon. During carbonization, a deep chemical cross-liking reaction can be generated in the pretreated D-glucose to obtain HC concurrently featuring with these favorable microstructures. The optimal HC anode (HC-1100) shows high initial coulombic efficiency (89.62%), large total capacity of 421.6 and 215.3 mAh g⁻¹ at 0.1 and 20 A g⁻¹, respectively. Besides, it delivers high plateau capacities of 303.31 and 193.1 mAh g⁻¹ at 0.1 and 5 A g⁻¹ along with 87% capacity retention for 2000 cycles, far surpassing than these reported HC anodes. Additionally, the HC-1100//Na₃V₂(PO₄)₃ full cell exhibits high energy density of 194 Wh kg⁻¹. Furthermore, Na⁺ storage behaviors and theoretical calculations demonstrates that the HC material owning high C=O content, suitable closed pore size (0.9 nm) and interlayer spacing (0.5 nm) possesses a superior ultrahigh-rate performance. This work provides a significative guidance for rational constructing high-performance HC anode.