Integrated copper host/current collector engineering for enhanced sodium storage in SeS2 electrodes

Abstract

Selenium disulfide (SeS₂) emerges as a promising candidate for sodium storage electrodes, boasting a high theoretical specific capacity and superior electrical conductivity compared to sulfur. Nonetheless, the cycling performance of SeS₂ is significantly compromised by its limited electrical conductivity and the shuttle effect of sodium polysulfides/polyselenides (NaPSs/NaPSes). To overcome these obstacles, we introduce a copper host/current collector co-engineering strategy to optimize the SeS₂ electrode's electrochemistry, thereby enhancing its stability and reaction kinetics. Ex situ characterization offers profound insights into the synergistic interaction between the Cu@CNT host and Cu foil with NaPSs/NaPSes during cycling, which effectively stabilizes NaPSs/NaPSes and forms a robust Cu/electrode interface. As a result, the SeS₂ electrode undergoes a transformation into NaPSs/NaPSes and conductive Cu_1.95S/Cu_1.8Se composites, substantially bolstering electrode stability and improving charge transfer kinetics. The synergetic effect between the Cu@CNT host and Cu foil endows the SeS₂ electrode with exceptional cycling performance (maintaining 100% capacity over 600 cycles) and remarkable rate capability (579 mA h g⁻¹ at 10 A g⁻¹), with minimal Cu corrosion (≤2.5%). The proposed battery system shows immense promise for stable, cost-efficient grid-scale applications.