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 <i>operando</i> 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.