NEC develops smaller, lighter battery

The new cells use a manganese laminate to replace the iron or aluminium commonly used in battery casing, the company said in a statement. It dissipates heat as well as the bulkier metal casings and helps the company increase the energy density of batteries by 25 percent to 150Wh/kg (watt hours per kilogram).

The new casing is being used first in a family of three batteries for cellular telephones and PDAs (personal digital assistants) -- both devices for which designers are constantly striving to reduce volume and weight.

In addition to the new case, the batteries also employ an NEC-developed proprietary manganate spinel cathode material -- a crystal structure that offers greater safety when batteries are accidentally overcharged, over discharged or when current limits are exceeded.