Rechargeable Alkaline Batteries Vs. Rechargeable Lithium Ion Batteries

Construction

• Alkaline rechargeable batteries employ an aqueous solution of potassium hydroxide -- a strong alkali, or base -- as an electrolyte, rather than the acidic chlorides used in traditional zinc chloride batteries. The positive electrode, or anode, is a gelled mixture of amalgamated zinc powder and the negative electrode, or cathode, is a mixture of high purity manganese dioxide and carbon. Lithium ion rechargeable batteries, on the other hand, consist of a positive electrode, or anode, made from lithium-cobalt-oxide, and a negative electrode, or cathode, made from carbon, immersed in an organic solvent as the electrolyte.

Starting Voltage

• Lithium is highly electropositive or, in other words, readily releases negatively charged particles, known as electrons. Rechargeable lithium ion batteries typically have a starting voltage of 3 volts or more, compared with 1.5 volts for rechargeable alkaline batteries. Lithium ion batteries also have up to three times the energy density, or energy per unit volume, of their alkaline counterparts. Rechargeable lithium ion batteries are therefore particularly suitable for portable devices, such as cellular phones, where long operating times are important.

Internal Resistance

• Internal resistance is the opposition to the flow of electrical current within a battery. Rechargeable lithium ion batteries employ a complex, organic electrolyte, which has a resistance between 10 and 100 times higher than the aqueous electrolyte employed by rechargeable alkaline batteries. As a result, the internal resistance of lithium ion batteries is higher, leading to higher energy losses. The higher internal resistance does mean, however, that lithium ion batteries don̵7;t present a safety hazard if short circuited.

Hazards

• The fact that lithium is highly electropositive can create major problems for the manufacture and use of rechargeable lithium ion batteries. The lithium ions tend to destroy the inorganic components of the battery and lithium reacts on contact with water to form hydrogen, which can ignite or create excessive pressure inside the battery casing. Rechargeable alkaline batteries contain caustic concentrated potassium hydroxide, but do usually not present a hazard unless they are subjected to high temperatures or physically, mechanically or electrically abused.