What are the core differences between sodium-ion batteries and supercapacitors?

储能原理、能量 / 功率密度、循环、适用场景差异极大。一储能机制：钠依靠电化学反应储存大量化学能，属于电池类；超级电容器仅双电层物理静电吸附，无化学反应，储能量极低。二密度指标：钠能量密度 120~160Wh/kg，功率密度中等；超级电容器能量密度不足 10Wh/kg，功率密度极高，可瞬时超大电流输出。三循环寿命：钠 3000~6000 次；超级电容器百万次循环无明显衰减。四放电时长：钠可持续数小时平稳放电，适配长时供电；超级电容器仅秒至分钟级短时脉冲输出。五自放电：钠月 2%~4%；超级电容器自放电极强，静置数天电量耗尽。六成本：同等容量钠远低于超级电容；同等峰值功率电容造价更低。七低温：钠 - 20℃可用；超级电容极宽温区间性能稳定。八应用：钠光伏储能、低速车持续供电；超级电容起重机脉冲、地铁制动瞬时回收。九串联难度：钠配套 BMS 均衡；超级电容单体压差难管控，串联复杂。

Huge gaps exist in storage mechanism, energy/power density, cycles and scenarios. 1. Storage principle: Sodium stores massive chemical energy via electrochemical reactions (battery type); supercapacitors adopt physical double-layer electrostatic adsorption without chemical reactions with tiny energy storage. 2. Density indicators: Sodium energy density 120~160 Wh/kg with medium power density; supercapacitors below 10 Wh/kg yet ultra-high power density for instantaneous giant current. 3. Cycle life: Sodium 3,000~6,000 cycles; supercapacitors withstand millions of cycles without obvious fading. 4. Discharge duration: Sodium supplies steady power for hours for long-duration loads; supercapacitors only deliver second-to-minute pulse power. 5. Self-discharge: Monthly sodium loss 2%~4%; supercapacitors self-discharge severely and drain power within days. 6. Cost: Sodium is far cheaper at equal capacity; capacitors cost less at equal peak power. 7. Low temperature: Sodium works at -20℃; supercapacitors perform stably across extreme temperatures. 8. Scenarios: Sodium for PV storage and continuous low-speed vehicle power; supercapacitors for crane pulses and subway braking energy recovery. 9. Series connection: Sodium matches BMS balancing; supercapacitors suffer difficult voltage difference control for series assembly.