Nickel-Metal Hydride (NiMH) vs. Sodium-Ion (Na-Ion)
Comparing 2 standards across 9 specifications. 9 key differences identified.
Nickel-Metal Hydride (NiMH) is the dominant rechargeable consumer chemistry for standard cylindrical battery formats (AA, AAA, C, D). Operating at 1.2V nominal, NiMH provides 60–120 Wh/kg specific energy, eliminates toxic cadmium, and modern Low Self-Discharge (LSD / Eneloop) formulations retain 70–85% of charge after several years of storage.
Sodium-Ion (Na-Ion) chemistry replaces lithium with abundant, low-cost sodium compounds. Operating at 3.0V–3.1V nominal with energy densities of 140–160 Wh/kg, Na-ion cells deliver exceptional low-temperature capacity retention (>85% at -20°C, operable down to -40°C), zero thermal runaway risk at 0V discharge, and use aluminum current collectors on both cathode and anode.
Specification Comparison Table
9 Parameters| Parameter / Spec | ||
|---|---|---|
|
Nominal Cell Voltage
|
1.20 V | 3.00 – 3.10 V |
|
Gravimetric Energy Density
|
60 – 120 Wh/kg | 130 – 165 Wh/kg |
|
Volumetric Energy Density
|
180 – 300 Wh/L | 260 – 340 Wh/L |
|
Cycle Life (to 80% Capacity)
|
500 – 1,500 Cycles | 2,000 – 4,000 Cycles |
|
Thermal Runaway Threshold
|
> 250 °C | > 260 °C |
|
Operating Temperature Range
|
-20 to +50 °C | -40 to +60 °C |
|
Self-Discharge Rate
|
10–20% / Month (Standard) | < 1% / Month (LSD) | 2 – 3% / Month |
|
Primary Anode Material
|
Hydrogen-absorbing Rare Earth Alloy (AB5 or AB2 Metal Hydride) | Hard Carbon (Biomass-derived Non-graphitizable Carbon) |
|
Primary Cathode Material
|
Nickel Oxyhydroxide (NiOOH) | Prussian White Analogues / Layered Transition Metal Oxides (NaMO2) |