Enhancing the Li+ storage capability of transition metal sulfides by in-situ regulating the phase conversion in operating batteries

Abstract

Transition metal sulfides (TMSs), with the advantages of high capacity and low cost, are attractive conversion-type anode materials towards all-solid-state lithium or lithium-ion batteries (ASSLBs, LIBs). However, the intrinsic phase conversion property also conveys structural destruction and short lifespan in repeated lithiation-delithiation reaction. Herein, size-controlled and phase-controlled failure mechanisms of various TMSs species are confirmed in LIB models, which are generated from the binding energy differences of TMSs interlayers. In ZnS, MoS2 and WS2 groups, the large particle size beyond 10 nm of secondary Zn/ZnS’, Mo/MoS2’ and W/WS2’ phase-converted products lead to capacity decay due to reduced Li+/e- transfer efficiency. In the FeS group, although the particle structure is remained without obvious destruction, phase conversion from pristine hexagonal FeS to low-active tetragonal FeS leads to capacity decay owing to increased Li+ transfer energy barrier. In comparison, enhanced Li+ storage capability is easily achieved by introducing a metastable amorphous Al2O3 nanocoating on TMSs particles’ surfaces. It’s found that the modulation characteristic of Al2O3 originates from the Al2O3-TMs bonding during long-term cycling processes, thus the size-controlled and phase-controlled failure mechanisms are in-situ restrained by the strong interface interaction. It’s expected to provide guidelines for the design and optimization of TMSs anodes.