Magnetoelectric coupling drives ultrafast-charging MoS₂ anodes for sodium-ion batteries

Abstract

Understanding and regulating the interfacial Na+-storage kinetics of MoS2 anodes remains a key challenge for sodium-ion batteries. Here, Co-doped MoS2 is employed as a model to elucidate, from the perspective of the dynamic evolution of spin-polarized electrons, a magnetoelectric coupling-dominated mechanism that accelerates interfacial Na+ storage. During the conversion reaction, Co atoms doped into the MoS2 lattice generate ~ 4 nm Co0 nanocrystals. In-situ magnetometry reveals that the spin-split bands of these magnetic Co0 nanocrystals effectively accommodate spin-polarized electrons, thereby generating a spin-polarized surface capacitive effect (“magnetic” contribution), which in turn enables ultrafast Na+ storage at the Co0/Na2S interfaces. Moreover, a portion of spin-polarized electrons stored in Co0 nanocrystals are transferred to electrolyte molecules, catalyzing their directional decomposition and promoting the formation of NaF-riched solid electrolyte interphase (“electric” contribution). Benefiting from this magnetoelectric coupling effect, the Co-doped MoS2 electrode exhibits excellent fast-charging capability in both half cells and full cells. This study not only establishes a direct link between spin-polarized electron dynamics and interfacial reaction pathways, but also provides important insights for the co-design of heterogeneous catalysis and interfacial dynamics.