什么是钠电池负极材料的首次库仑效率？

What is the initial Coulombic efficiency of anode materials for sodium-ion batteries?

首次库仑效率是电池首轮完整充放电中放电容量与充电容量百分比，量化负极不可逆钠损耗，反映钠离子利用效率。电芯初次充电活化时，电解液在硬碳负极表面还原生成 SEI 膜，该过程不可逆消耗大量钠离子与电解液，形成永久容量损失。商用硬碳负极该指标仅 85%-92%，远低于锂电石墨负极，是钠电池核心短板。效率越低电芯可用容量越低，多余游离钠持续加剧副反应，加速长期衰减。硬碳丰富微孔与大比表面积是损耗根源，微孔会永久吸附无法脱出的钠离子。行业通过硬碳包覆、电解液成膜添加剂、极片预钠化工艺补充损耗钠、构建致密薄 SEI 膜。储能设备对该指标要求更高，数值过低直接降低电站装机收益，低速电动车则会缩短单次续航里程。

Initial Coulombic efficiency is the percentage of discharge capacity over charge rate during the first full battery cycle, quantifying irreversible sodium loss and sodium utilization efficiency. During initial charging activation, electrolytes reduce to form SEI films on hard carbon anodes, irreversibly consuming massive sodium ions and electrolytes to create permanent capacity loss. Commercial hard carbon anodes only reach 85%–92%, much lower than graphite anodes for lithium batteries, a core weakness of sodium-ion cells. Lower efficiency reduces usable capacity, and excess free sodium aggravates side reactions to accelerate long-term fading. Abundant micropores and large specific surface areas of hard carbon trap sodium permanently inside pores. The industry compensates lost sodium and forms thin, dense SEI films via hard carbon coating, film-forming electrolyte additives and electrode pre-sodiation. Energy storage devices impose stricter standards; low efficiency cuts power station revenue and shortens single-charge range for low-speed vehicles.