Combined intercalation and space-charge mechanism enabled high-capacity, ultrafast and long-lifespan sodium-ion storage for chalcogenides anodes

Abstract

The increasing demand for advanced battery redox chemistry, surpassing intercalation, conversion, and alloying processes, is pivotal in driving the rapid progress of next-generation rechargeable batteries. Herein, we discover a new ionic storage mechanism of combined intercalation and space-charging chemistry in the transition metal dichalcogenides (TMDs) of group IV and V elements (specifically Ti, Nb, and Ta). Taking NbS2 as an example, a new ternary intercalation compound Cu0.43DME0.12NbS2 is spontaneously formed through a Cu+-ether co-intercalation process with Cu current collectors in ether-based electrolytes. Subsequently, Na+ ions can reversibly (de)intercalate into Cu0.43DME0.12NbS2 with limited volume expansion, and Na+ can adsorb on the surface of in-situ electrochemical-induced Cu nanoparticles with fast kinetics and extra storage. Such synergistic processes enable a high specific capacity of 705 mAh g-1, surpassing its theoretical limit, a superior rate capability of 116 mAh g-1 at 75 A g-1, and an impressive cycle longevity over 1 year. Combined with Na3V2(PO4)3 (NVP), the full cell demonstrates an exceptional power density of 17453 W kg-1. The study paves the way for designing functional electrode materials for high-power and long-lifespan batteries.