Multielectron Conversion: Peculiar Transition Metal Sulfides with Mixed Vulcanized States toward High-Capacity Metal-Ion Storage

摘要

Transition metal sulfides with mixed vulcanized states (TMS-mVs) possesstremendous potential to realize highcapacity, superior redox reactions, andstructural reversibility for metal-ion (Mn+) storage owing to theirmultielectron reactions caused by the simultaneous participation of transitionmetal (TM) cations and S_2~(2?) anions as well as multifarious TM or S valencestates. Here, recent advances are systematically introduced regarding themainstream TMS-mVs that can be applied to M~(n+) storage. These TMS-mVscan be divided into two categories of TMS, those with mixed sulfur-valencestates (TMS-mSs) and those with mixed metal-valence states (TMS-mMs). Itis found that TMS-mV anodes mainly experience three reaction mechanisms,inculding insertion-accompanied conversion, insertion, and conversionreactions. During the reversible charge process, Li_2S is possibly oxidized intopolysulfides or even S. TMS-mVs have the ability to transfer more electronsthan other homogeneous TMSs. TMS-mS anodes usually present highertheoretical specific capacities than TMS-mM anodes. In these TMS-mVanodes, Mo-based, V-based, and Co-based TMS-mM anodes exhibit goodelectrochemical reversibility, Ni-based TMS-mM anodes exhibit moderateelectrochemical reversibility, and Fe-based TMS-mM and TMS-mS anodesexhibit poor electrochemical reversibility. The strategies for enhancement oftheir electrochemical performance are classified into composite, coating,nanostructure, heterointerface, and lattice engineering.