Carrier Depletion-Induced Suppression of Solid Electrolyte Interphase and Conversion Reaction in Zn_1–xMg_xO Nanocrystal Solid Solution Li-Ion Batteries

In this study, we investigated the effects of charge carrier depletion on the formation of the solid-electrolyte interphase (SEI) followed by conversion reaction involving alloying/dealloying reactions during the cycling of Li-ion batteries. In our investigation, Zn 1– x Mg x O nanocrystal solid solutions were used as the anode, focusing on a range where x varied between 0.05 and 0.15. We observed that a significant decrease in electrical conductivity occurred at x = 0.15, accompanied by a marked decrease in field-effect transistor (FET) mobility and carrier concentration. Consequently, both SEI formation and the conversion reaction were suppressed in the initial discharge process, resulting in a specific capacity significantly lower than that of ZnO ( x = 0). Our findings revealed that the Zn 0.85 Mg 0.15 O sample exhibits a strong depletion of surface charge carriers by trapping compared to ZnO and Zn 0.95 Mg 0.05 O. This was demonstrated by ultraviolet (UV)-induced (FET) and photoluminescence (PL) measurements. Since the processes of Li-ion alloying, ZnO reduction, and SEI formation are influenced by trap-induced surface carrier depletion, controlling these traps could enhance the energy density of Li-ion batteries. This advancement holds particular significance for high-demand applications, such as electric vehicles and grid storage systems.