In a collaborative effort, the Changchun Institute of Applied Chemistry of the Chinese Academy of Sciences and the Institute of Deep-sea Science and Engineering have achieved a groundbreaking milestone. They have successfully developed a high-energy-density rechargeable lithium battery pack capable of withstanding the immense pressure found at full ocean depths, boasting an energy density exceeding 400Wh/kg. Sea trials have been successfully completed. This innovative battery pack addresses the challenge of carrying sufficient power for deep-sea exploration, where batteries must function under extreme high pressure conditions and within strict load capacity limits. This represents a significant advancement in China's energy system for deep-sea equipment.