Researchers in China have developed a bismuth carbon composite anode for sodium ion batteries that keeps most of its capacity after 1000 charge cycles. The material, made from a bismuth based metal organic framework, uses a porous carbon scaffold to absorb the swelling that normally breaks alloying anodes. At 1 A/g it held 416.5 mAh/g with 99.9% coulombic efficiency. Sodium ion batteries are a cheaper alternative to lithium for stationary storage, but anode durability has been a weak point. This work, published in the Journal of Materials Science, shows a controllable synthesis route using solvent ratios and temperature to tune the structure. That matters for manufacturing reproducibility. The results are lab scale and need full cell testing, but they point to a practical path for longer lived sodium ion packs in grid and building storage applications.
