Nickel-Metal Hydride (NiMH) vs. Zinc-Air
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.
Zinc-Air is an open-cathode primary battery chemistry that utilizes atmospheric oxygen as the active cathode material. Because the cathode reactant does not need to be stored inside the cell, Zinc-Air achieves exceptional gravimetric energy densities of 400–500 Wh/kg and volumetric densities up to 1,400 Wh/L, making it the universal standard for hearing aids.
Specification Comparison Table
9 Parameters| Parameter / Spec | ||
|---|---|---|
|
Nominal Cell Voltage
|
1.20 V | 1.40 – 1.45 V |
|
Gravimetric Energy Density
|
60 – 120 Wh/kg | 400 – 500 Wh/kg |
|
Volumetric Energy Density
|
180 – 300 Wh/L | 1,100 – 1,400 Wh/L |
|
Cycle Life (to 80% Capacity)
|
500 – 1,500 Cycles | Single Use (Activated upon seal removal) |
|
Thermal Runaway Threshold
|
> 250 °C | > 200 (Safe) °C |
|
Operating Temperature Range
|
-20 to +50 °C | 0 to +50 °C |
|
Self-Discharge Rate
|
10–20% / Month (Standard) | < 1% / Month (LSD) | < 2% / Year (Sealed) | Drains in 2–4 Weeks (Unsealed) |
|
Primary Anode Material
|
Hydrogen-absorbing Rare Earth Alloy (AB5 or AB2 Metal Hydride) | High-purity Zinc Powder (Zn) |
|
Primary Cathode Material
|
Nickel Oxyhydroxide (NiOOH) | Atmospheric Oxygen (O2) via Gas Diffusion Membrane |