Unlocking the Design Paradigm of In‐Plane Heterojunction with Built‐in Bifunctional Anion Vacancy for Unexpectedly Fast Sodium Storage

Abstract

Transition metal chalcogenide (TMD) electrodes in sodium‐ion batteries exhibit intrinsic shortcomings such as sluggish reaction kinetics, unstable conversion thermodynamics, and substantial volumetric strain effects, which lead to electrochemical failure. This report unlocks a design paradigm of VSe2−x/C in‐plane heterojunction with built‐in anion vacancy, achieved through an in situ functionalization and self‐limited growth approach. Theoretical and experimental investigations reveal the bifunctional role of the Se vacancy in enhancing the ion diffusion kinetics and the structural thermodynamics of NaxVSe2 active phases. Moreover, this in‐plane heterostructure facilitates complete face contact between the two components and tight interfacial conductive contact between the conversion phases, resulting in enhanced reaction reversibility. The VSe2−x/C heterojunction electrode exhibits remarkable sodium‐ion storage performance, retaining specific capacities of 448.7 and 424.9 mAh g−1 after 1000 cycles at current densities of 5 and 10 A g−1, respectively. Moreover, it exhibits a high specific capacity of 353.1 mAh g−1 even under the demanding condition of 100 A g−1, surpassing most previous achievements. The proposed strategy can be extended to other V5S8−x and V2O5−x‐based heterojunctions, marking a conceptual breakthrough in advanced electrode design for constructing high‐performance sodium‐ion batteries.

The progress of research on vacancies in HMF electrooxidation

“…Thermal activation represents a prevalent mechanism wherein elevated temperatures empower atoms within the metal lattice with adequate energy to surmount energy barriers, thus facilitating the migration of specific anions and leaving vacancies in their wake. This phenomenon is commonly observed during heat treatments or annealing processes, where the application of high temperatures fosters atomic mobility and the formation of lattice imperfections ( Wu et al, 2021 ; Ma et al, 2024 ). Moreover, radiation-induced damage serves as another notable pathway for anionic vacancy formation.…”

“…Moreover, radiation-induced damage serves as another notable pathway for anionic vacancy formation. Exposure to radiation, such as neutrons or gamma rays, can instigate atomic displacement and structural modifications within the metal crystal lattice, thereby engendering anionic vacancies ( Liu et al, 2019 ; Ma et al, 2024 ). This occurrence is frequently encountered in environments like nuclear reactors, radioactive material handling, or other nuclear applications.…”