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.