The China National Intellectual Property Administration (CNIPA) on December 9 invalidated the patent ZL200780042406.4 covering a co-extruded, multi-layered battery separator owned by US battery separator producer Celgard, LLC. The petition for a trial for invalidation before the CNIPA was filed by its Chinese rival Shenzhen Senior Technology Material Co., Ltd. (深圳市星源材质科技股份有限公司).

The subjects of the litigation between the two parties have been separators in lithium-ion batteries (LIB). Separators are critical components in liquid electrolyte batteries. Celgard filed a patent infringement lawsuit against Senior and its wholly-owned subsidiary with the United States District Court Northern District of California in September 2019. About two months later, Senior filed a patent infringement lawsuit against Celgard and its Chinese related parties with the Shenzhen Intermediate People's Court of Guangdong province.

Before 2013, Celgard and Japan’s two companies Asahi and Toray were the main battery separator producers in the world. Chinese companies such as Senior and SEMCORP have grown rapidly. Senior even became LG Corporation's battery separator supplier in 2013 and has been leading the world for 5 consecutive years. As of 2020, China's lithium battery separator output has accounted for more than half of the global output, the rest of which are delivered by Japan companies companies and South Korean companies. Comparatively speaking, Japanese companies have better technology and Chinese and South Korean companies have better cost control methods.