EcoPro said Wednesday it has celebrated 10 years of supplying battery materials to Sony, later acquired by Murata Manufacturing.

According to the company, it first supplied high-nickel cathode materials for Sony in 2013 for the first time for a Korean company. The two companies have kept business ties even after Murata, a Japanese electronics manufacturer, took over Sony’s loss-making battery business in 2017.

EcoPro has been providing thousands of tons of nickel, cobalt and aluminum (NCA) cathode materials annually for non-IT sector batteries for Murata’s electronic devices, wireless vacuums and electric bikes. It has gradually expanded the supply of materials, the company said.

“It was an unprecedented case of a small Korean firm like us to have supplied battery materials to Sony, the world-class battery cell maker who first commercialized lithium-ion batteries in 1993,” EcoPro said in a statement. “It is also memorable for Korean and Japanese companies to have maintained partnership for up to 10 years.”

Looking back on the early 2000s when its rival companies drastically cut the price of battery precursors, the company said the chicken game paradoxically gave them an opportunity for a turnaround as it downsized the precursor business and expanded high-nickel cathode materials sector.

Lee Dong-chae, former EcoPro chairman, at that time urged executives to land a deal with Sony, seeking a breakthrough in overcoming the sales drop of precursors, the battery materials maker said.

Knocking on Japan’s door, EcoPro participated in the major battery exhibition called “Battery Japan” in 2010 and 2011. Sony showed interest in the Korean company’s cathode materials technology but demanded a more high-quality product.

A year after, Sony dispatched a task force team to EcoPro’s Ochang plant in North Chungcheong Province, where it gave tips on how to minimize contamination during production. After Sony agreed to receive 5 tons of cathode material prototypes in 2013, the Japanese and Korean companies signed a long-term deal on March 2015.

In 2015, EcoPro built its third plant in Ochang, reaching an annual production capacity for high-nickel cathode materials of 4,300 tons. The company surpassed the 100 billion won ($75.6 million) mark in sales revenue in the same year, stepping up as the world’s second-largest NCA cathode materials manufacturer following Japan’s Sumitomo Corp.