Preparation of Enriched Closed-Pores Hard Carbon for High-Performance Sodium-Ion Batteries by the Poly(vinyl butyral) Template Method

Closed pores play an essential role in improving the performance of sodium-ion batteries. Various strategies have been proposed to increase the closed-pore ratio, but most of them face challenges related to cost and waste disposal. Here, we chose furfural as the resin precursor to synthesize the raw material and prepare enriched closed-pore hard carbon using poly(vinyl butyral) (PVB) as the in situ pore-forming agent. At 450 °C, the decomposition of PVB within furfural resins leads to the formation of numerous micropores, which sets the stage for the creation of hard carbon with closed pores. The optimal hard carbon sample exhibits a low specific surface area (N2) of 10.54 m2 g–1 and a high volume of closed pores (0.090 cm3 g–1). The optimal pore structure of the hard carbon resulted in a high reversible sodium storage capacity of 367 mAh g–1 and an initial Coulombic efficiency (ICE) of 88.5% at 30 mA g–1. Furthermore, the use of PVB as a pore-forming agent is minimal and the decomposition products are environmentally friendly. This is a practical guide for producing high-performance hard carbon.