FUZHOU -- China's largest lithium battery producer, Contemporary Amperex Technology Co Ltd (CATL), has announced that it has created a lithium-ion sample battery cell with an energy level of 304Wh/kg.

CATL batteries are primarily focused on prismatic cell formats using NMC (lithium nickel manganese cobalt oxide) chemistries, which have found massive application in China's booming electric vehicles (EV) market.

Energy density, or energy per unit mass, presents a bottleneck for lithium-ion batteries and the EV industry, said Wu Kai, chief scientist with CATL.

Wu said the company had developed a high-performance anode cobalt material to improve battery capacity, and managed to extend battery life with a new coating method in the cathode.

He said CATL also used high-end light and solid aluminum material, a common material in the undercarriage of aircraft, as the lower box in its battery packs to improve energy density.

CATL is now capable of achieving a 240Wh/kg energy density level in mass production.

Headquartered in the city of Ningde in southeast China's Fujian province, the battery giant posted 29.6 billion yuan (4.4 billion US dollars) in revenue last year, up 48.1 percent.

Founded in 2011, CATL has inked supply contracts with a slew of global car manufacturers including BMW, Volkswagen, Daimler and Honda.