Enhancing the lithium storage properties of SiO@NC anode by MnNb2O6 decoration

Abstract

The scalable application of SiO anode in lithium ion batteries is still limited by its low initial Coulombic efficiency and inferior cycle stability. Compositing SiO with other substances that own high structural stability, fast Li ion diffusion rate and good Li ion storage capacity has been proven of effectiveness to tackle the aforementioned problems. Herein, manganese niobate (MnNb2O6) that possesses 3-dimensional Li ion diffusion channels is used to modify SiO anode in conjunction with N-doped carbon coating to improve the Li-ion storage performance. Ex situ XRD measurements reveal that the orthorhombic MnNb2O6 is converted to amorphous LixMnNb2O6 during lithiation and reversed back to MnNb2O6 in the following delithiation process. The crystal structure of MnNb2O6 is well preserved after a long-term cycle test, suggesting its high structural stability. With such stable structure and ultrafast Li ion diffusion kinetics, the optimized SiO@MnNb2O6@NC composite anode exhibits obviously improved rate performance and cycle stability as compared to SiO@NC. A reversible capacity of 835 mAh g−1 is maintained at a relatively high current density of 3.0 A g−1, and a discharge capacity of 799 mAh g−1 is preserved after 200 cycles at 1.0 A g−1. This work provides a facile and promising strategy to modify SiO-based anode with Columbite-type Nb-based metal oxides towards better Li-ion storage properties.