Hitachi Doubles Life of Li-ion Battery With Mn-based Cathode Material

Apr 7, 2010
Tsunenori Tomioka, Nikkei Monozukuri

Hitachi Ltd developed a positive-electrode material that can double the life of the company's industrial lithium-ion (Li-ion) rechargeable battery using a manganese positive-electrode material.

The life of the battery was extended by (1) replacing part of the manganese contained in the positive-electrode material with another element to stabilize the crystal structure and (2) adding an acid-resistant composite oxide (an oxide that contains more than one metallic element) to the positive-electrode material to reduce the elution of manganese into the electrolyte.

Hitachi prototyped a battery cell with the new positive-electrode material and concluded that it is possible to realize a battery whose capacity decreases at half the rate and whose life is twice as long (more than 10 years) compared with the company's existing battery cell.

The material is expected to be used for storing electricity at renewable energy-based power plants such as wind-power plants as well as for supplying electricity to electric motor-driven construction machines, which can reduce CO2 emissions. This time, Hitachi prototyped the battery cell in collaboration with Shin-Kobe Electric Machinery Co Ltd.

Li-ion rechargeable batteries are used mainly for consumer electronic devices such as mobile phones and mobile PCs. And many of them use a positive-electrode material composed mainly of cobalt (Co), which is a scarce resource.

As an increasing number of Li-ion batteries are used for applications other than consumer electronic devices (e.g. electric hybrid vehicles and electric vehicles), the procurement of cobalt will become an issue. Therefore, Hitachi had an eye on manganese, which is abundantly available, as one of the candidates for a positive-electrode material composed mainly of a metal element other than cobalt.

The company has been researching, for example, a lithium-manganese spinel material (LiMn2O4, which has a spinel structure. Though LiMn2O4 features a high operating voltage and is suited for storing electricity, its capacity lowers due to charging and discharging.

It is possible to stably supply the new positive-electrode material at a low cost because it is composed mainly of manganese. Hitachi plans to enhance the performance of the battery cell by further improving the new positive-electrode material and the composition of the electrolyte in the aim of expanding its business of storage battery-related products.