Researchers in China found a simple way to keep tin anodes from falling apart in sodium-ion batteries: cap the capacity the electrode can use. By limiting discharge to 600 mAh/g instead of letting tin fully alloy with sodium, they avoided the extreme volume swelling that fractures particles. In testing, microsized tin anodes held up for 170 cycles at about 99% Coulombic efficiency, and full cells paired with a sodium vanadium phosphate cathode delivered stable capacity for 100 cycles. The approach matters because microsized tin is cheap and easy to process compared with nanostructured alloys. Capacity limitation is an operating protocol, not a new material, so it could be programmed into a battery management system. The tradeoff is lower usable capacity per cycle, which may be acceptable for stationary storage where longevity and cost matter more than peak energy density. The research was published in Ionics.
