Nickel-cadmium cell
Definition and meaning of Nickel-cadmium cell in chemistry.
Nickel-cadmium cell (NiCad battery) is a rechargeable electrochemical cell that stores and delivers electrical energy through reversible redox reactions between metallic cadmium and nickel oxide hydroxide electrodes immersed in an alkaline potassium hydroxide electrolyte. These batteries can sustain hundreds of charge-discharge cycles, making them reliable for demanding applications.
In more detail
During discharge, cadmium metal at the anode oxidizes to cadmium hydroxide while nickel oxide hydroxide at the cathode reduces to nickel hydroxide, generating current through an external circuit. This reaction reverses during recharging. NiCad cells exhibit exceptional tolerance to overcharging, short circuits, mechanical shock, and deep discharge, with stable voltage output over most of the discharge curve. However, they are susceptible to the memory effect (capacity loss if not fully discharged before recharging) and contain toxic cadmium, which has led to their replacement by lithium-ion batteries in modern portable electronics.
Key facts
| Cell Reaction | Cd + 2NiO(OH) + 2H2O yields Cd(OH)2 + 2Ni(OH)2 |
|---|---|
| Nominal Voltage | 1.2 V per cell |
| Cycle Life | 500-1000 cycles |
| Field | Inorganic Chemistry |
NiCad batteries powered cordless drills, two-way radios, and emergency lighting systems throughout the 1970s-1990s. For instance, a typical AA-sized NiCad cell with nominal voltage of 1.2 V could deliver several hundred complete charge cycles before degradation became significant.
Frequently asked questions
What is the memory effect in NiCad batteries?
If a NiCad battery is recharged before being completely discharged, it 'remembers' the shorter effective capacity and will subsequently provide less usable energy until a full discharge-recharge cycle is performed.
Why are NiCad batteries no longer widely used?
Cadmium is toxic and hazardous to the environment; additionally, lithium-ion and nickel-metal-hydride batteries offer superior energy density, lack the memory effect, and do not contain toxic metals, making them preferable for most modern applications.