Alloy-type anodes in alkaline ion batteries have to face the challenges of huge volume change and giant structure strain/stress upon cycling. Here, reducing the structure stress for advanced performances by voltage regulation is demonstrated by using microsized Sn (μ-Sn) for sodium ion batteries as a model. Density functional theory and finite element analysis indicate that Sn/NaSn3 is the crucial phase transition highly responsible for inducing surface cracks, particle aggregations, and cell failures. Eliminating this phase transition by the control of cutoff voltages successfully extends the cycle life of μ-Sn to 2500 cycles at 2 A g-1, much longer than ∼40 cycles in a regular voltage window. The specific capacity is still retained at ∼455 mAh g-1, leading to a capacity decay of only ∼0.0088% per cycle. The results provide a simple way to achieve the outstanding performances without complicated preparation, expensive reagents, and laborious processing.
Keywords: Alloy-type anodes; Phase transition; Sodium-ion batteries; Structure stress; Tin.