What factors affect the sodium storage capacity of sodium-ion battery anodes?

负极储钠容量由材料本征属性、微观结构、极片制造、使用工况四大维度共同约束。材料种类决定理论上限：硬碳依靠层间与微孔储钠，容量 300-350mAh/g；锑、锡合金理论容量极高，但膨胀超 300% 无法量产；钛基负极稳定但容量不足 200mAh。微观层面碳层间距、微孔占比、结晶度至关重要，间距不足阻碍嵌钠，微孔过多增大不可逆损耗，结晶过高减少储钠位点。极片工艺上压实过高堵塞微孔，浆料不均、缺导电剂造成局部极化，烘干残留水分破坏负极界面。工况层面低温大幅降低钠离子扩散速度，快充仅表层材料参与储钠，高温加厚 SEI 损耗容量；电解液钠盐浓度、溶剂匹配度也直接改变离子迁移效率，左右实际可释放容量。

Sodium storage capacity of anodes is jointly restricted by four factors: intrinsic material properties, microstructure, electrode manufacturing and operating conditions. Material types set theoretical limits: hard carbon stores sodium via interlayers and micropores at 300–350 mAh/g; antimony/tin alloys have ultra-high theoretical capacity yet cannot be mass-produced due to over 300% volume expansion; titanium-based anodes are stable but below 200 mAh/g. Microstructure factors include carbon interlayer distance, micropore ratio and crystallinity: narrow gaps hinder sodium intercalation, excessive pores raise irreversible loss, and high crystallinity reduces storage sites. Excess compaction blocks micropores; uneven slurry and insufficient conductive agents cause partial polarization; residual moisture after drying damages anode interfaces. At low temperatures, sodium diffusion drops sharply, only surface materials function during fast charging; high temperatures thicken SEI films to lose capacity. Sodium salt concentration and solvent compatibility of electrolytes also alter ion transport efficiency and practical capacity.