Boosting Molecular Cross-Linking in a Phenolic Resin for Spherical Hard Carbon with Enriched Closed Pores toward Enhanced Sodium Storage Ability
Liewen Guo, Chuang Qiu, Renlu Yuan, Xiaotian Li, Xin Li, Kairan Li, Wanxiong Zhu, Xue‐Wei Liu, Ang Li, Haiyan Liu, Xiaohong Chen, Huaihe Song
Abstract
Phenolic resin (PF) is considered a promising precursor of hard carbon (HC) for advanced-performance anodes in sodium-ion batteries (SIBs) because of its facile designability and high residual carbon yield. However, understanding how the structure of PF precursors influences sodium storage in their derived HC remains a significant challenge. Herein, the microstructure of HC is controlled by the degree of cross-linking of resorcinol-benzaldehyde (RB) resin. We reveal that robust molecular cross-linking in RB resin induced by hydrothermal treatment promotes closed-pore formation in the derived HC. The mechanism is devised for the decomposition of a highly cross-linked RB three-dimensional network into randomly stacked short-range graphitic microcrystals during high-temperature carbonization, contributing to the abundant closed pores in the derived HC. In addition, the high cross-linking degree of RB resin endows its derived HC with a small-sized spherical morphology and large interlayer spacing, which improves the rate performance of HC. Consequently, the optimized hydrothermal treatment HC anode shows a higher specific capacity of 372.7 mAh g –1 and better rate performance than the HC anode without hydrothermal treatment (276.0 mAh g –1 ). This strategy can provide feasible molecular cross-linking engineering for the development of closed pores in PF-based HC toward enhanced sodium storage.