Authors: Zhenzhuang Wen, Ruiguang Zhao, Tongtong Tian, Tao Zhang, Xin Wang, Xinyi Yang, Wanqing Song, Yanan Chen, Jia Ding, Wenbin Hu
Published: 2025-03-25
Source: Full article
AbstractHigh energy density of sodium‐ion batteries (SIBs) requires high low‐voltage capacity and initial Coulombic efficiency for hard carbon. However, simultaneously achieving both characteristics is a substantial challenge. Herein, a unique molecular stitching strategy is proposed to edit the polymeric structure of common starch for synthesizing cost‐effective hard carbon (STHC‐MS). A mild air‐heating treatment toward starch is employed to trigger the esterification reaction between carboxyl and hydroxy groups, which can effectively connect the branched polysaccharide chains thereby constructing a highly cross‐linked polymeric network. In contrast with the pristine branched‐chain starch, the cross‐linking structured precursor evolves into highly twisted graphitic lattices creating a large population of closed ultramicro‐pores (<0.3 nm) enabling the storage of massive sodium clusters. Resultantly, STHC‐MS delivers a reversible capacity of 348 mAh g−1 with a remarkable low‐voltage (below 0.1 V) capacity of 294 mAh g−1, which becomes more attractive by combining the high initial Coulombic efficiency of 93.3%. Moreover, STHC‐MS exhibits outstanding stability of 0.008% decay per cycle over 4800 cycles at 1 A g−1. STHC‐MS||Na3V2(PO3)4 full cells achieve an energy density of 266 Wh kg−1, largely surpassing the commercial hard carbon‐based counterpart. This work opens the avenue of molecular‐level modulation in organic precursors for developing high‐performance hard carbon in SIBs.