SEOUL, July 17 (Yonhap) — SK Holdings Co. said Friday it has invested an additional 100 billion won (US$83 million) in Chinese copper foil manufacturer Lingbao Wason Copper Foil in the latest move to solidify its electric vehicle (EV) battery business.

The move came 15 months after the holding firm of South Korean energy and telecoms conglomerate SK Group invested 270 billion won in Lingbao Wason Copper Foil, becoming the second-largest shareholder of the Chinese company.

Lingbao Wason Copper Foil is the world’s largest manufacturer of copper foil, a material used as the negative electrode current collector of a lithium ion battery.’

SK Holdings has made a series of investments in foreign companies in recent years as part of its efforts to diversify its revenue sources.

In May, SK Holdings Co. invested 8 billion won in Singapore’s Hummingbird Bioscience, which focuses on the development of novel antibody-based therapeutics.

Last year, SK Holdings invested about $5 million in the Chinese biotech company Harbour BioMed.

In 2017, SK Holdings invested $1 billion in Eureka Midstream, a U.S. midstream energy company handling the gathering, transportation and compression of natural gas.