Interphase engineering by tunable redox of (p-d) π-bond additive toward extended lifespan of sodium-ion batteries

Abstract

The durability of the cathode and anode interphases is critical for long-term stable cycling of sodium-ion batteries, however, difficult to achieve precise modulation in conventional carbonate-based electrolytes. Herein, from the perspective of functional additives, the sulfur-containing interphase engineering is introduced by the cyclic sulfate esters with tunable redox mechanism, which are oriented to alter specific decomposition and film-forming pathways on the surface of the cathode and anode, compensating for the deficiencies of the fluorinated interphases, such as improving the inhomogeneous and fragile characteristics, while enhancing the ion transport efficiency. As a result, the cells based on hard carbon (HC) and high voltage Na₃V₂(PO₄)₂O₂F (NVPF) demonstrate excellent cycling stability (1000 and 8000 cycles with more than 80 % and 83 % capacity retention, respectively). Moreover, the assembled HC//NVPF full cell also achieves a cycle life of more than 2500 cycles with a capacity retention of 91%, which is far superior to that of conventional carbonate electrolytes. Furthermore, the high-voltage oxide cathode also demonstrates extended cycling stability (80 % capacity retention after 300 cycles). In short, the proposed sulfur-based additive strategy enables to effectively improve the problems encountered in carbonate-based electrolytes, providing certain reference and application value.