Lithium-Ion (Li-ion) batteries are rechargeable energy storage devices commonly used in portable electronics, electric vehicles, and renewable energy systems. They work by moving lithium ions between the positive and negative electrodes during charging and discharging, allowing for efficient energy transfer and storage. These batteries are favored for their high energy density, lightweight design, and long cycle life compared to other battery types. However, they require careful management to prevent overheating and degradation, making battery management systems essential for safety and performance in applications like smartphones, laptops, and electric cars.