Ni-Cd Batteries Alan Kim / Mitchell Stasko / Bryan Zhang

History 1899 / Created by a Swede, Waldemar Jungner / Patented in the U.S. by Edison / Production began in the U.S / Technological advances lead to creation of the modern sealed battery. 1990s / Sales plummeted due to increasing popularity of NiMH and Li-ion batteries.

Components Four parts: NiOOH cathode. Cd anode. Separator. KOH electrolyte.

Uses Can be used in electronics and toys. Good for power tools! NiCads operate at full capacity for an entire charge. Also used with remote-controlled toys.

Electrochemistry Half-reaction at the anode oxidizes cadmium. Cd + 2OH - → Cd(OH) 2 + 2e - Half-reaction at the cathode reduces nickel oxide-hydroxide. NiO(OH) + H 2 O + e - → Ni(OH) 2 + OH - The net redox reaction: 2NiO(OH) + Cd + 2H 2 O → 2Ni(OH) 2 + Cd(OH) 2

Secondary Cell NiCad batteries are secondary cells. The redox reaction is reversible but goes forward spontaneously. An electrical current can force the reaction to go backwards by changing the flow of electrons.

Advantages Low internal resistance. Works safely from C to 70 0 C and thus is more reliable than Li-ion batteries. Can be used for 500 recharge cycles. Endothermic charging allows for short recharge times. The electrolyte, KOH, is easy to obtain. Can be made in many different sizes and capacities.

Disadvantages Easily damaged by overcharging. Cadmium is a toxic heavy metal that pollutes landfills and must be carefully disposed of. It’s also really expensive! NiMH and Li-ion batteries have replaced NiCad batteries in the last two decades because of their relative affordability.

The Memory Effect Another disadvantage of NiCd batteries Occurs from repeatedly recharging a battery that isn’t fully discharged. Can also be caused by long periods of inactivity and exposure to high temperatures. These lead to a buildup of cadmium crystals. Battery voltage drops significantly even though the battery isn’t near complete discharge. Can be prevented with full recharge cycles.

Manufacturing 1.Nickel powder sintered on a wire mesh. 2.NiOOH and Cd deposited on the plate. 3.Nickel tab welded onto the plate corners. 4.Multiple plates put together by aligning tabs. 5.Porous plastic separator placed between. 6.Aqueous KOH added.

Disposal It’s dangerous to throw away or incinerate NiCads. Most countries try to recycle these batteries. Short-term exposure to cadmium can cause pneumonitis. Long-term exposure can cause lung cancer and kidney damage. The EU has banned all NiCad sales except for medical use, alarms, emergency lighting, and power tools.

Wet Cell Wet Cell NiCd batteries use liquid cadmium and solid Nickel Maintains a solid 1.2 V discharge up until it is depleted Advantages: Maintains its voltage as opposed to slowly losing it, durable. Disadvantages: Hard to determine charge, extremely heavy, spillage hazards Used mostly for heavy industrial purposes now due to cost and safety dangers.

Ventilated Used for large capacities and high discharge rates. Releases excess hydrogen or oxygen gas created by redox reactions. Safer, weighs less, and cheaper than other cells. It is not damaged by overcharge, discharge, or negative charge. Lasts 20 years longer than other NiCads. Used in aviation, rail and mass transit, and telecoms backup power. Electrolyte must be replaced regularly.

Dry Cell Uses a paste electrolyte. Cathode rod with anode wrapped around. Only uses the moisture necessary for current to flow. Good for portable things because it can operate in any position!

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