A lithium-ion battery is a type of rechargeable battery commonly used in portable electronics, electric vehicles, and renewable energy storage. It operates by moving lithium ions between the positive and negative electrodes during charging and discharging, which allows it to store and release energy efficiently. These batteries are popular due to their high energy density, lightweight design, and low self-discharge rate. They can be found in devices like smartphones, laptops, and tablets, making them essential for modern technology. However, they require careful handling and recycling to minimize environmental impact.