On April 20, 2025, the high-energy deep-sea oil-filled self-pressurized lithium-ion silicon-carbon battery pack independently developed by the Changchun Institute of Applied Chemistry (CIAC), Chinese Academy of Sciences, successfully completed field verification at a depth of 4,200 meters in the South China Sea, marking a major technological breakthrough for China in this field.

This deep-sea battery pack overcame the key technology of high-energy lithium-ion silicon-carbon cells, achieving an energy density exceeding 400 Wh/kg. The battery management system (BMS) architecture was optimized to build an intelligent energy management network under complex deep-sea operating conditions. The project systematically addressed the technical challenges of the self-pressurized power supply structure under the extreme deep-sea pressure environment of 121 MPa. Key innovations include pressure-adaptive regulation design, highly integrated battery pack solutions, enhanced high-voltage system stability, and full-lifecycle reliability verification for deep-sea equipment. The battery pack was deployed on a lander developed by the Institute of Deep-sea Science and Engineering (IDSE), Chinese Academy of Sciences, completing a total of four deep-sea operations at 4,200-meter depth, with sustained system operation exceeding 72 hours. This technology achieves lightweighting (approximately 40% weight reduction compared to conventional power solutions of the same specifications), high reliability, and extended endurance (50% longer single-dive operation cycle) for deep-sea equipment energy systems.

This technological breakthrough marks China as the first country in the world to apply 400 Wh/kg-class high-energy lithium secondary battery technology to deep-sea equipment, providing a revolutionary lightweight energy solution for deep-sea exploration equipment. It effectively addresses the energy supply challenge under high-pressure deep-sea environments and provides critical technical support for strategic areas including deep-sea resource development, marine scientific research, and national defense security.

(Contributed by the State Key Laboratory of Rare Earth Resources. Written by Liu Tong.)

High-energy lithium battery pack

Deep-sea test operation 1

Deep-sea test operation 2