What battery type did Thomas Edison develop using nickel and iron electrodes?

Thomas Edison developed a nickel–iron battery using nickel and iron electrodes.

Edison worked on the rechargeable battery in the early twentieth century, seeking a durable alternative for electric vehicles, railway equipment, and other uses. The battery used nickel oxyhydroxide at the positive electrode and iron at the negative electrode, with an alkaline electrolyte, commonly potassium hydroxide.

Nickel–iron batteries were rugged and capable of long service lives, but they had disadvantages including relatively high cost, low energy efficiency, and significant gassing during charging. Those limitations restricted their competition with other battery technologies in many markets.

The battery is sometimes called the Edison battery, but Edison did not invent rechargeable batteries generally. His contribution was the development and commercialization of this particular nickel–iron chemistry, which remains of interest for durable stationary energy storage.