Japanese electronics maker Matsushita has begun mass-production of a new lithium-ion battery it says is safe from the overheating problems that have plagued laptop computers this year.

Matsushita, the parent company of Panasonic, said Monday they will begin producing five million units of the new batteries per month. The company was making 100,000 a month when the batteries were first introduced in April.

The battery features a heat-resistant metal oxide layer on the surface, which the company says will prevent overheating.

The announcement follows a series of incidents in which laptop batteries have overheated or caught fire. Sony had to recall millions of battery packs to computer makers, affecting Dell and Apple, among others.

The most spectacular case was a Dell laptop battery that exploded and burned at a June 2006 conference in Japan.

The liquid inside laptop batteries can sometimes contain microscopic pieces of pure lithium, a highly reactive metal. When one of these particles punctures the separator between the anode and cathode inside the battery, it can cause a short circuit that increases both heat and pressure in the battery, which Sony blamed for some of the problems with its batteries.

Matsushita owns 13 per cent of the global lithium-ion battery market, behind Sanyo, Sony and Samsung.