Deciphering the Performance Enhancement, Cell Failure Mechanism, and Amelioration Strategy of Sodium Storage in Metal Chalcogenides-Based Andes.

Transition metal chalcogenides (TMCs) emerge as promising anode materials for sodium-ion batteries (SIBs), heralding a new era of energy storage solutions. Despite their potential, the mechanisms underlying their performance enhancement and susceptibility to failure in ether-based electrolytes remain elusive. This study delves into these aspects, employing CoS 2 electrodes as a case in point to elucidate the phenomena. Our investigation reveals that CoS 2 undergoes a unique irreversible and progressive solid-liquid-solid phase transition from its native state to sodium polysulfides (NaPSs), and ultimately to a Cu 1.8 S/Co composite, accompanied by a gradual morphological transformation from microspheres to a stable 3D porous architecture. This reconstructed 3D porous structure is pivotal for its exceptional Na + diffusion kinetics and resilience to cycling-induced stress, being the main reason for ultra-stable cycling and ultrahigh rate capability. Nonetheless, the CoS 2 electrode suffers from an inevitable cycle life termination due to the micro-short-circuit induced by Na metal corrosion and separator degradation. Through a comparative analysis of various TMCs, we establish a predictive framework linking electrode longevity to electrode potential and Gibbs free energy. Finally, the cell failure issue is significantly mitigated at a material level (graphene encapsulation) and cell level (polypropylene membrane incorporation) by alleviating the NaPSs shuttling and micro-short-circuit. This article is protected by copyright. All rights reserved.