Full‐Cell Presodiation Strategy to Enable High‐Performance Na‐Ion Batteries

Abstract As promising alternatives to lithium‐ion batteries, sodium‐ion batteries suffer from low coulombic efficiency, which stems from Na‐deficiency and unstable interfaces for both cathode and anode materials. Exhibiting a favorable solvation structure, Na‐naphthalene/tetrahydropyran (Na‐NP/THP) is screened and selected as a full‐cell presodiation solution for hard carbon (HC) anodes and a P‐2 type Na 0.67 Fe 0.1 Al 0.1 Mn 0.8 O 2 (NFAM) cathode, which are both Na‐deficient. Through a wealth of characterizations, it is revealed that the proposed presodiation agent not only boosts the initial coulombic efficiency of both HC and NFAM electrodes effectively, but also facilitates robust solid–electrolyte interphase (SEI) and cathode–electrolyte interphase (CEI) on both electrodes. Consequently, the long‐term cycling and rate performance are greatly improved thanks to the stabilized structures of electrode materials. Furthermore, a proof‐of‐concept NFAM||HC pouch cell based on this presodiation strategy is assembled, showing a high reversible capacity and superior cycling performance. By offering a remedy to a full cell system subjected to severe Na‐deficiency, this work conceptually demonstrates a feasible strategy to fully tap the potential of high‐energy‐density materials in sodium‐ion batteries.