Rapid Electron/Ion Transport in a 3D Holey-Graphene Aerogel Framework toward High-Loading Na–Se Batteries

Abstract

Seleniumized polyacrylonitrile (SePAN) has emerged as a promising cathode for sodium–selenium (Na–Se) batteries due to its covalent C–Se bonding configuration that suppresses polyselenide dissolution. However, its practical application under high mass loading is hindered by sluggish electron/ion transport within thick electrodes. Herein, we report a freestanding SePAN cathode integrated with a three-dimensional holey graphene aerogel framework (SePAN@3DHG), which boosts the electronic conductivity of SePAN by nearly five orders of magnitude (1.33 × 10–1 S cm–1). Concurrently, H2O2-etched nanopores create abundant Na⁺ diffusion channels, significantly reducing ion-transport resistance. In-situ electrochemical impedance spectroscopy combined with distribution of relaxation times analysis reveals substantially reduced charge-transfer resistance and diffusion impedance throughout the charge–discharge process, confirming the enhanced reaction kinetics enabled by the holey architecture. As a result, the designed SePAN@3DHG cathode enables Na–Se batteries to deliver a high reversible capacity of 361.6 mAh g–1 at an ultra-high areal loading of 13.2 mg cm–2. Moreover, a capacity of 226.8 mAh g–1 is maintained after 2000 cycles at 1 C under a high areal loading of ~6 mg cm–2. This work establishes an effective electron/ion synergistic transport strategy for high-loading Na–Se batteries.