Spatially confined transition metals boost high initial coulombic efficiency in alloy anodes†

Abstract

Alloy-type materials hold significant promise as high energy density anodes for lithium-ion batteries. However, the initial coulombic efficiency (ICE) is significantly hindered by the poor reversibility of the conversion reaction and volume expansion. Here, the NiO/SnO₂ multilayers with a hybrid interface of alloy and transition metal oxides are proposed to generate Ni nanoparticles within confined layers, catalyzing Li₂O decomposition and suppressing the coarsening of Sn or Li₂O particles. Supported by density functional theory (DFT) calculations and revealed by operando magnetometry, the spatially confined, well maintained Ni active sites lower the energy barrier for Li–O bond rupture and enhance the migration dynamics of Li⁺. The enhanced reaction kinetics lead to achievement of an impressive ICE of 92.3% and a large capacity of 1247 mA h g⁻¹ with 97% retention after 800 cycles. Furthermore, the NiO/SnO₂ anode exhibits excellent electrochemical performances in both Na/K-ion batteries. Notably, when constructed with the same framework, SiO₂ also delivers significantly improved lithium storage properties with ultra-high ICEs. This work paves the way for advanced designs of alloy-type anodes that satisfy both ICE and overall electrochemical performance.