Based on energy storage methods, energy storage can be divided into three categories: Physical energy storage, chemical energy storage, and electromagnetic energy storage. Physical energy storage mainly includes pumped hydro storage, compressed air storage, and flywheel energy storage; chemical energy storage mainly includes lead-acid batteries, lithium-ion batteries, sodium-sulfur batteries, and flow batteries; and electromagnetic energy storage mainly includes supercapacitor energy storage and superconducting energy storage.
In high-power applications, lead-acid batteries are generally used, primarily for emergency power supplies, electric vehicles, and storing surplus energy from power plants. In low-power applications, rechargeable dry-cell batteries, such as nickel-metal hydride batteries and lithium-ion batteries, can also be used.