Famous batteries

Primary batteries

Not rechargeable, useless when reach equilibrium; includes Alkaline and zinc-air batteries

Nickel-metal hydride battery

Rapidly replacing nickel-cadmium because it does not suffer from memory effect. Rechargeable. Type of rechargeable battery similar to a nickel-cadmium (NiCd) battery but has a hydrogen-absorbing alloy for the anode instead of cadmium. Like in NiCd batteries, nickel is the cathode. A NiMH battery can have two to three times the capacity of an equivalent size NiCd and the memory effect is not as significant. However, compared to the lithium-ion battery, the volumetric energy density is lower and self-discharge is higher. Applications of NiMH type batteries include hybrid vehicles such as the Toyota Prius.

Secondary batteries

Rechargeable; includes: lead-acid, nickel-cadmium, nickel-metal hydride, and lithium ion batteries

Lead-acid battery

Used in automobiles, the electrodes are made of lead and lead-oxide with a strong acidic electrolyte. They are rechargeable. Despite having the second lowest energy-to-weight ratio (next to the nickel-iron battery) and a correspondingly low energy-to-volume ratio, their ability to supply high surge currents means that the cells maintain a relatively large power-to-weight ratio. This, along with their low cost, makes them ideal for use in cars, as they can provide the high current required by automobile starter motors. Each cell contains (in the charged state) electrodes of lead metal (Pb) and lead (IV) oxide (PbO2) in an electrolyte of about 37% (5.99 Molar) w/w sulfuric acid (H2SO4).

Alkaline battery

Used in common Duracell and Energizer batteries. The electrodes are zinc and manganese-oxide, with an alkaline electrolyte. Inside an alkaline battery, manganese dioxide molecules are converted into manganese oxide and hydroxyl ions. The hydroxyl ions then react with zinc to form zinc oxide and water, releasing electrons. The electrons move toward the carbon rod and flow out around the circuit, producing an electric current. The battery stops producing electricity when all the manganese dioxide is used up.

Nickel-cadmium battery

Uses nickel-hydroxide and cadmium electrodes, with potassium-hydroxide as the electrolyte. Rechargeable. Until recently, virtually all rechargeable batteries were nickel-cadmium (NiCd, usually pronounced "nicad"). Although very dependable, they need to be discharged fully before you charge them up or the amount of charge they will store (and their effective lifespan) can be greatly reduced.

Lithium-ion battery

Very good power-to-weight ratio, often found in high-end laptop computers and cell phones. Rechargeable. High discharge rates don't significantly reduce its capacity, nor does it lose very much capacity after each cycle, still retaining 80% of its energy capacity after 500 recharge cycles. Early versions were prone to exploding in the labs and people still claim there is a risk with these batteries.

Zinc-air battery

small, non-rechargeable batteries with open circuit voltages of 1.15 to 1.4 V per cell. They use surrounding air (O2) as the cathode. They are long lasting, high performance batteries used in small devices such as hearing aids and pagers.

Reasons batteries are important to us

•produce a lot of energy; •produce a lot of current; •don't weigh very much or take up much space; •aren't toxic or environmentally dangerous; •have reversible reactions (are rechargeable); •oh, and don't cost very much.