|Energy and Power Densities of SK HEV/PHEV Cells (H65, H75, P155). Click to enlarge. Source: SK Energy|
South Korea-base SK Energy will invest 159 billion won (US$110 million) to expand its lithium-ion battery production, according to a filing with the Korea Exchange.
SK Energy was the first Korean company, and the third in the world, to independently develop a lithium-ion battery separator, which features proprietary technology for low shrinkage and heat resistance. The company began commercial Li-ion battery production in 2005, targeting mobile devices, and is developing high energy density power batteries for hybrid electric (HEV), plug-in hybrid electric (PHEV) and electric (EV) vehicles.
SK Energy uses LiMn2O4 (manganese spinel) as its cathode material. Manganese spinel enables a higher voltage cell with excellent safety characteristics; however, it has known cycle life problems because of manganese dissolution, which are exacerbated at higher temperatures.
To solve this, some cell developers have substituted amorphous carbon for crystalline carbon in the anode, resulting in reduced energy density due to the high initial irreversible capacity loss, according to SK Energy’s Jeon Keun Oh.
Instead, SK Energy is opting for crystalline carbon as the anode material to deliver a battery system with higher energy density. To address the problem of lifecycle decay at high temperature due to manganese dissolution, SK Energy uses a polymer gel ingredient, coated electrode materials and SEI enhancement additives.
As a result, said Oh at the 1st International Conference on Advanced Lithium Batteries for Automobile Applications, organized by Argonne National Laboratory, more than 90% of the power remains even after 200 days storage at 45°C. More than 70% of the capacity and power is maintained after 5,000 full cycles at 5C.
SK produced and tested prototype packs in HEV and PHEV vehicles for testing; these battery systems are now ready for production.