At the forefront of technological advancement, the proliferation of portableand wearable electronics has necessitated the development of innovativepower solutions. As these devices become increasingly indispensable in dailylife, the demand for sustainable and adaptable power sources has intensified.This review focuses on integrated self-charging power systems (SCPSs),which synergize energy storage systems, particularly through rechargeablebatteries like lithium-ion batteries, with energy harvesting from solar,mechanical, thermal, and chemical energy. These SCPSs extend operationaltimes, reduce recharging frequency, and have the potential to developself-sufficient power systems. The study explores various approaches tooptimize both individual components and the integrated power system forwearable and flexible electronics, covering SCPSs that combine multipleenergy-harvesting strategies. Special attention is given to designconsiderations, material advancements, and engineering challenges,alongside the latest research breakthroughs in energy harvesting and storagetechnology. The review concludes with an assessment of the prospects andchallenges in the field of battery-integrated energy harvesting systems,highlighting the need for advancements in energy density, power output, andsafety to meet the demands of modern electronics.