钠电池正极材料的比容量是什么意思？

What does the specific capacity of cathode materials for sodium-ion batteries mean?

钠电池正极材料的比容量是衡量正极储钠能力核心指标，单位 mAh/g，指 1 克正极活性物质在标准充放电条件下可逆存储释放的电量，分为理论与实际两类。理论值由材料化学式可脱嵌钠总量计算，为性能上限；实际比容量受结晶度、粒径、包覆、电解液匹配、极片压实工艺限制，永远低于理论值。三类主流正极参数差异明显：普鲁士蓝 120-160mAh/g，聚阴离子 100-130mAh/g，层状氧化物 150-180mAh/g。电芯设计必须做正负极容量匹配，负极总储容量略高于正极，防止充电析出金属钠造成短路。比容量直接决定电芯同等重量下的储能与续航表现，是企业材料筛选首要标准，结合压实密度可算出体积能量密度，适配储能、低速电动车等多元应用场景。

The specific capacity of sodium-ion battery cathodes, measured in mAh/g, is a core metric evaluating sodium storage capacity. It refers to the reversible electric charge stored and released by one gram of cathode active material under standard charge-discharge conditions, split into theoretical and practical values. The theoretical value, calculated based on total extractable sodium ions in material formulas, marks the performance ceiling. Practical specific capacity is always lower, restricted by crystallinity, particle size, surface coating, electrolyte compatibility and electrode calendering. Three mainstream cathodes differ greatly: Prussian blue analogs deliver 120–160 mAh/g, polyanions 100–130 mAh/g, layered oxides 150–180 mAh/g. Cell design requires cathode-anode capacity matching with slightly higher anode capacity to avoid sodium metal precipitation and short circuits. As a primary screening standard for manufacturers, specific capacity directly determines cell energy storage and endurance, and volumetric energy density can be calculated with compaction density to fit energy storage and low-speed vehicle scenarios.