Uncovering and preventing polytellurides dissolution enables stable sodium-ion storage: A case study of SnTe

Abstract

Metal tellurides (MTes) have emerged as promising candidates for high-specific energy sodium-ion batteries owing to their superior volumetric capacity and exceptional intrinsic conductivity. Nevertheless, their practical application faces challenges associated with pronounced capacity degradation associated with unclear decay mechanisms. In this study, we uncover, for the first time, that the dissolution and shuttling of intermediates (NaxTey) are responsible for the rapid capacity decay in alloy- and conversion-type MTe anodes. Based on this discovery, we propose a novel structural engineering strategy that involves confining ultrafine SnTe nanoparticles within a fibrous carbon matrix, facilitating the smooth immobilization and highly reversible conversion of NaxTey. State-of-the-art in-/ex-situ tests and density functional theory calculations elucidate the evolution and shuttling mechanisms of NaxTey, highlighting the van der Waals barrier of the carbon matrix and the remarkable chemisorption of N and S dopant sites towards Na2Te2 and Na2Te intermediates. Significantly, the chemisorption capacity of NaxTey is enhanced through the optimization of doping content and bonding type of N and S, resulting in excellent stability of SnTe embedded in a high-content N and S co-doped carbon fiber matrix (SnTe@SHNC). The elaborate SnTe@SHNC composites demonstrate exceptional performance, enduring over 1000 cycles at 1.0 A g−1 with an ultraslow capacity decay rate of 0.028 % per cycle. This work provides valuable insight into the pivotal role of controlling NaxTey in the design of durable MTe anodes for advanced SIBs.