Na2SnO3 as a novel anode for high performance lithium storage and its electrochemical reaction mechanism

Highlights: • Na₂SnO₃ was employed as anode material for LIBs. • Na₂SnO₃ showed outstanding cycling stability due to the synergetic effect of "Na₂O″ intrinsic matrix and "Li₂O″ extrinsic matrix. • Na₂SnO₃ showed dramatically enhanced electrochemical performance in terms of capacity, cycling stability and rate capability in comparison to SnO₂ and Li₂SnO_3. • The electrochemical reaction mechanism of Na₂SnO₃ with Li was investigated by ex situ XRD technique. -- Abstract: Herein, Na₂SnO₃ is employed as an anode for rechargeable lithium ion battery (LIB). We thoroughly investigated the electrochemical performance of Na₂SnO₃ in comparison with the most commonly used Sn based oxides, such as SnO₂ and Li₂SnO₃. It is found that Na₂SnO₃ is greatly superior to SnO₂ and Li₂SnO₃ in terms of capacity, cycling stability and rate capability. Impressively, Na₂SnO₃ presents favorable specific capacity of 480 mA h g⁻¹ at current density of 200 mA g⁻¹ after 100 cycles and still delivers a capacity of 439 mA h g⁻¹ at extremely large current density of 1000 mA g⁻¹, which are leading the performance in anodes for LIBs. Ex situ SEM analysis of anodes after different cycles revealed the surface microstructure of anodes plays a critical role in determining cycling stability. The SEM results show big cracks on the surface of electrode for SnO₂ after less 15 cycles and for Li₂SnO₃ after more 100 cycles, resulting from their severe volume change during charging-discharging process. However, Na₂SnO₃ electrode exhibits uniform surface morphology after 100 cycles. It is concluded the "Na₂O″ intrinsic matrix of Na₂SnO₃ combining with "Li₂O″ formed from the conversion reaction can act as a mixture buffering matrix that contributes to keeping the electrochemically formed nanoscale Sn particles apart and preventing their agglomeration during Li−Sn alloy formation and decomposition, thus inhibiting the volume expansion and the capacity fading by maintaining the electrode integrity. In addition, the electrochemical reaction mechanism of Na₂SnO₃ with Li is investigated by ex situ XRD technique. The findings in this study provide a new valuable anode for high-performance LIBs and an insightful viewpoint of developing anode materials with high electrochemical performance by introducing the electrochemical inactive intrinsic matrix.