The present invention provides a high-energy-density secondary lithium-ion battery, including: a lithium-ion cell, a steel shell, a protection IC, an integrated IC, resistors, capacitors, an inductor, a MicroUSB interface, a plastic structural part, a square rigid FR-4 substrate, a circular rigid FR-4 substrate and a metal cap, for integrating three functions of a constant voltage output, charge management and protection, overcharge and overdischarge protection, and overcurrent protection. Compared with the prior art, the large-capacity secondary battery of the present invention can achieve multi-functional integration of the battery, and also can save the space occupied by accessory structural parts of the battery and achieve a high energy density of the battery, and is also conducive to improving the reliability.