A redox flow battery is a type of rechargeable battery that stores electrical energy in chemical solutions contained in external tanks. The energy is stored in the form of two electrolytes with different redox potentials that flow through a cell where they undergo redox reactions to produce electricity. Redox flow batteries are known for their scalability and long cycle life, making them ideal for grid-level energy storage applications. They are being researched and developed as a cost-effective and efficient solution for storing renewable energy and balancing the grid.