General Motors has introduced a new light electrification system known as eAssist in its full-sized 2012 Buick LaCrosse and 2012 Buick Regal. However, how does the new system work?
At the heart of its power is an 115V, 0.5kWh lithium-ion battery system built with Hitachi third generation power optimised cells. In the latest edition of Hitachi Review, the company’s engineers looked at the characteristics of these cells and their efforts to create a fourth generation for hybrids as well as their plans for a prismatic cell for plug-in hybrid electric vehicles.
The third generation cells include a manganese based cathode and amorphous carbon anode with a high power density of 3,000W/kg. The engineers noted that they optimised the proportion of lithium and other metals in the cathode while controlling the microstructure to reduce charge transfer resistance.
In addition, there were improvements in the anode structure and new electrolyte additives that boosted calendar life compared to the previous generation of cells. Hitachi also developed packs to meet GM’s requirements, with each consisting of two 16cell modules with two blocks of eight cells and with the battery monitoring module on top of the battery modules. The pack was air-cooled and other parameters were optimised to reduce cell temperature rise. Currently, the company has a production capacity of around 300,000 cells a month.
Going forward, its fourth generation hybrid electric vehicle power cell will have a power density of 4,500W/kg and use manganese based materials designed with optimum grain size and thinner electrodes to reduce transfer resistance. The fourth generation cell will boast 1.5times the output power density of the third generation as well as good heat radiation performance.
In addition, Hitachi is developing a prismatic battery that will combine high energy and high output that can be used as a power source for plug-in hybrid electric vehicles.
