The positive electrode material of nickel cadmium batteries is a mixture of nickel hydroxide and graphite powder, the negative electrode material is a sponge mesh sieve like cadmium powder and cadmium oxide powder, and the electrolyte is usually a solution of sodium hydroxide or potassium hydroxide. When the ambient temperature is high, use a sodium hydroxide solution with a density of 1.17-1.19 (at 15 ℃). When the ambient temperature is low, use a potassium hydroxide solution with a density of 1.19-1.21 (at 15 ℃). When below -15 ℃, use a potassium hydroxide solution with a density of 1.25~1.27 (at 15 ℃). To balance low-temperature performance and charge retention capacity, sealed nickel cadmium batteries use a potassium hydroxide solution with a density of 1.40 (at 15 ℃). In order to increase the capacity and cycle life of batteries, a small amount of lithium hydroxide is usually added to the electrolyte (approximately 15-20g per liter of electrolyte).

After charging a nickel cadmium battery, the active substance on the positive electrode plate becomes nickel hydroxide [NiOOH], and the active substance on the negative electrode plate becomes metallic cadmium; After discharging the nickel cadmium battery, the active substance on the positive electrode plate becomes nickel hydroxide, and the active substance on the negative electrode plate becomes cadmium hydroxide.