SiO@Nb2O5@NC composite anodes with enhanced rate and cycle performance for Li-ion batteries

Abstract

Although SiO/G (G denotes graphite) products are commercially available in nowadays, their scalable applications in Li-ion batteries are still limited by their poor stability and high cost. Herein, niobium oxide (Nb2O5) with open tunnel structure is composited with SiO in combination with N-doped carbon (NC) coating, which have jointly enhanced the rate and cycle performance of the resulting SiO@Nb2O5@NC composite anodes. Under optimum conditions, a capacity retention of 74% is preserved after 200 cycles at 0.2 A g−1, together with a high capacity of 666 mA h g−1 at 3 A g−1. Ex situ XRD analysis reveals that Nb2O5 is transformed to amorphous LixNb2O5 and electrochemical-inert NbO in the first lithiation process. The former exhibits fast Li+ migration rate and capacitive Li ion storage behavior, which may help to improve the electrochemical performance of SiO. Further mixing the SiO@Nb2O5@NC composite with spent graphite extracted from used LiFePO4 battery yields a high capacity and stable anode material that shows a high capacity retention of 79% after 500 cycles at 0.4 A g−1. This work may shed a light on the development of stable yet low cost SiO/G anode materials through pre-modification of SiO with Nb2O5 and utilization of cheap graphite resource.