Materials, performance, and system design for integrated solar flow batteries – A mini review

Integrating renewable energy such as solar and wind energy into the grid has become an urgent need nowadays since the energy supply continues to be tight and uneven. To address the intermittent and fluctuating issues of solar energy, in recent years, integrated solar flow batteries have experienced a rocketing development due to their unique advantages of integrated high efficiency conversion-storage-power supply from solar to chemical energies, and flexible compact structure. Till now, both solar cells and flow batteries have been extensively investigated, while the integration of the two has not reached maturity. In this mini-review, the basic features and classification of solar flow batteries are firstly described. Several important performance indicators of solar flow batteries including light response capability, battery life and spontaneity of charging in actual supply of this battery to the grid are also introduced. The design, matching and optimization of photoelectrodes, counter electrodes, electrolytes, package-energy level alignment, as well as future perspective of integrated solar flow batteries are discussed afterwards, with emphases on the photoelectrode and electrolyte to increase the photocurrent, reduce electron transfer resistance and enlarge the energy density. This mini review aims to provide a reference of both scientific understanding and practical application of integrated solar flow batteries, as well as suggest promising research directions for further development.