Closed pore engineering of activated carbon enabled by waste mask for superior sodium storage

Carbonaceous materials with closed pore structure have emerged as intriguing anode materials for sodium-ion batteries (SIBs). However, it remains a significant challenge to precisely regulate the structure of closed pores to achieve superior electrochemical Na-storage performance. Herein, a simple but practical strategy is proposed to convert the open pores in activated carbon (AC) into closed pores with the assistance of polypropylene (PP) waste masks. This transition occurs via the carbonization of light aromatic compounds from PP, which deposit on the entrance of the AC's open pore and generate PP-based carbon layer thus regulating the pore configuration of AC. When configured as an anode for SIBs, the hard carbon with optimal closed pores (CMAC-2) delivered a high reversible capacity of 335.5 mAh g−1 with satisfactory initial coulombic efficiency of 88.7 % as well as remarkable cycle and rate capability. Additionally, the assembled O3-NaNi1/3Fe1/3Mn1/3O2//CMAC-2 full cell achieves a high energy density of 277.5 Wh kg−1 (based on the total mass of anode and cathode) with an outstanding rate capability. This work not only offers an ingenious method to fabricate closed pore structure with boosted Na+ storage performance, but also provides a sustainable practice by repurposing polyolefin waste into value-added energy storage products.