Inhibiting grain coarsening and inducing oxygen vacancies: the roles of Mn in achieving a highly reversible conversion reaction and a long life SnO2–Mn–graphite ternary anode

Abstract

To obtain highly reversible conversion reactions, high Coulombic efficiencies, and long lifetimes in SnO₂-based anodes for lithium storage, a new ternary SnO₂–Mn–graphite composite has been constructed by scalable ball-milling. It is demonstrated that nanosized Mn additives successfully inhibit Sn coarsening, and favor the formation of oxygen vacancies in SnO₂, which together promote the high reversibility of conversion reactions in lithiated SnO₂. The SnO₂–Mn binary hybrid with 30 wt% Mn contributes a stable long-life with a capacity retention of 100% after 900 cycles at 1 A g⁻¹. The ternary SnO₂–Mn–graphite composite demonstrates high average initial Coulombic efficiencies of ∼77%, large stable capacities of 850 mA h g⁻¹ at 0.2 A g⁻¹, and long lifetimes of more than 1000 cycles at both high rates (2 A g⁻¹) and narrow potential ranges (0.01–2.4 V), with Coulombic efficiencies of 99.7%, which are among the best reported so far for SnO₂-based anode materials. The simple material design strategy and fabrication method, together with the excellent electrochemical performances, demonstrate that this new ternary SnO₂–Mn–graphite composite could contribute a new class of Sn-based anode materials for high capacity battery applications.