How does a nickel-hydrogen battery work? Well, a nickel-hydrogen battery uses nickel-based chemistry at its positive electrode, and hydrogen at its negative electrode.
Like other rechargeable batteries, it stores energy through reversible chemical reactions. Electricity supplied during charging changes the chemical state of the battery, allowing it to deliver electricity later.
The Positive Electrode Contains Nickel Oxyhydroxide
The positive electrode contains nickel oxyhydroxide and nickel hydroxide in different states of charge. The negative electrode uses a catalyst to help hydrogen participate in the reaction.
Both electrodes are surrounded by an alkaline electrolyte, usually potassium hydroxide. A separator keeps the electrodes apart while allowing ions to move through the electrolyte. That’s how a nickel-hydrogen battery works in practice.
External Electricity Supply Drives The Chemical Reactions
During charging, an external electricity supply drives the chemical reactions in reverse. Hydrogen generates at the negative electrode and accumulates inside the sealed cell. Its pressure rises as charging proceeds.
During discharging, hydrogen is consumed at the negative electrode, while the nickel-based positive electrode undergoes its corresponding chemical change. Electrons flow through the external circuit, providing useful electrical power.
A particularly important feature is the strong pressure-resistant metal enclosure. Unlike an ordinary battery case, it must safely contain hydrogen at substantial pressure.
Hydrogen pressure also provides engineers with useful information about the battery’s state of charge, although accurate assessment requires appropriate monitoring and operating controls.
Nickel-Hydrogen Batteries Are More Complicated
Nickel-hydrogen batteries are therefore more complicated than their basic chemistry might suggest. Their performance depends on electrode design, catalyst effectiveness, electrolyte condition, temperature and pressure management.
When properly engineered, however, they can deliver exceptional durability and tolerate thousands of charge-discharge cycles.
Nickel-Hydrogen Especially Suitable For Spacecraft
This combination of reversible chemistry and robust construction made nickel-hydrogen batteries especially suitable for spacecraft. Dependable operation over many years was more important than having the cheapest or smallest possible battery.
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