What is the correct composition of the electrolyte in a nickel-cadmium battery?

• A. Water only
• B. Sodium hydroxide and water
• C. Hydrogen peroxide solution
• D. Potassium hydroxide and water

Answer: (D)

Nickel-cadmium cells rely on an alkaline electrolyte to enable the nickel and cadmium electrodes to exchange electrons efficiently. This electrolyte is a concentrated potassium hydroxide solution, with water forming the liquid medium. The alkaline environment provides OH− ions that participate in the cell’s redox reactions and gives high ionic conductivity while remaining chemically compatible with the nickel oxyhydroxide and cadmium electrodes. Water alone wouldn’t supply the needed ions for conduction, and hydrogen peroxide would promote unwanted side reactions that could degrade performance. While other alkaline solutions exist, potassium hydroxide in water is the standard electrolyte for NiCd cells, making potassium hydroxide and water the correct composition.