LAUSR

Despite the high theoretical energy densities of tin as the anode of the sodium-ion batteries (SIBs), its electrochemical performance has been plagued by the inadequate initial Coulombic efficiency (ICE) and poor cycle life. While it is generally believed that mechanical degradation, namely pulverization and subsequent loss of electrical contact, is the underlying cause, here we show gassing is an essential problem in sodium-ion batteries with Sn anode. Since the gas generation appears at a certain voltage, reducing the voltage through metallurgically pre-alloying Sn with Na could be a solution, with an added benefit of compensating for "live" Na loss in future cycles. When the metallurgically alloyed foil was used as the anode in Na3V2(PO4)2F3 (NVPFs)//alloy full cells, the ICE is significantly improved from 24.68% to 75%, and from the 2nd cycle to the 100th cycle, the average Coulombic efficiency can maintain up to 99.44%. The full cell can run for 100 cycles, with acceptable capacity decay to 81.4mAh/g(NVPF) from the initial 112.5mAh/g(NVPF).