What is the most significant advantage of flow batteries over lithium-ion batteries for grid-scale energy storage?

The most significant advantage of flow batteries over lithium-ion batteries for grid-scale energy storage is their ability to independently scale energy capacity and power rating. In a flow battery, the energy is stored in liquid electrolytes housed in external tanks, while the power is determined by the size of the electrochemical stack where the chemical reaction occurs. This separation allows for independent scaling: increasing the size of the electrolyte tanks increases the energy capacity (how long the battery can discharge), while increasing the size of the stack increases the power rating (how quickly the battery can discharge). This modular design provides greater flexibility in designing energy storage systems to meet specific grid requirements. Lithium-ion batteries, on the other hand, have a fixed ratio between energy and power. Increasing the energy capacity of a lithium-ion battery also increases its power rating proportionally, which may not be optimal for applications requiring long-duration storage with moderate power output. This independent scaling capability makes flow batteries particularly well-suited for grid-scale applications such as long-duration storage for renewable energy integration and peak shaving, where the ability to store large amounts of energy for extended periods is critical.