Subzero temperature promotes stable lithium storage in SnO2

Abstract It is known that low operating temperature reduces significantly the discharging capacity and cycling stability of lithium ion battery (LIB). In addition LIBs are unable to charge at subzero temperatures because of the propensity for Li dendrite formation on graphite anodes. The present work we found that SnO2 anode can deliver high capacity under subzero temperature, 71% of its 30°C capacity at –20°C in a commercial LiPF6-EC/PC based electrolyte, which is much higher than that of intercalating graphite and Li4Ti5O12, alloying Si-C anodes and other materials. Most surprisingly, different from the serious capacity attenuation of electrodes occurring at room temperature, subzero temperatures effectively promotes the good cycling stability of pure SnO2 anodes toward Li storage. High capacities of 603.1 mAh g–1 at –20°C and 423.8 mAh g–1 at –30°C can be maintained stable throughout the cycles. In-situ X-ray diffraction monitoring reveals that subzero temperature suppresses Sn coarsening in lithiated SnO2 anodes to maintain a high reversibility for alloying and conversion reactions, which ensures stable capacities in 0-1.0 V and 1.0-2.4 V potential range. Furthermore, allotropy transformation from β-Sn to α-Sn could be helpful to build faster transfer channels for Li-ions during de-/lithiation in subzero temperatures. This work shows that SnO2-based anode materials could qualify the LIBs for a safe and long-life running in low-temperature environments.