The plant in Xi'an is selling products to major Chinese customers and was the first in China. Two of its rivals, LG and Panasonic, plan to start operation of their factories there from late this year.

The Xi'an plant, which will be jointly operated by two Chinese companies, will supply batteries to major carmakers, as well as Yutong, the world's top bus manufacturer, and Foton, China's biggest truck producer.

The number of SDI's battery clients in China increased to 10. The Xi'an factory can supply up to 40,000 battery packs annually for use in electric vehicles (EVs). The next part of the expansion will involve battery cells and modules.

Company spokesman Song Young said Samsung wants to invest $600 million to expand the facilities by 2020. Samsung SDI aims to have $1 billion sales in 2020.

This will make China the biggest market in EVs. SDI expects the country to take up more than 10 percent of the global EV demand as the Chinese government drives initiatives to cut carbon emissions and pushes more eco-friendly business projects. Beijing wants 5 million charging stations across the country by 2020 to help the EV industry grow.

SDI said the completion of the battery plan represents the conglomerate's moves to diversify its portfolio amid heated competition in consumer electronics such as smartphones, televisions and home appliances.