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Flow batteries have received extensive recognition for large‐scale energy storage such as connection to the electricity grid, due to their intriguing features and advantages including their simple structure and principles, long operation life, fast response, and inbuilt safety. Market penetration of this technology, however, is still hindered by some critical issues such as electroactive species crossover and its corresponding capacity loss, undesirable side reactions, scale‐up and optimization of structural geometries at different scales, and battery operating conditions. Overcoming these remaining challenges requires a comprehensive understanding of the interrelated structural design parameters and the multivariable operations within the battery system. Numerical modeling and simulation are effective tools not only for gaining an understanding of the underlying mechanisms at different spatial and time scales of flow batteries but also for cost‐effective optimization of reaction interfaces, battery components, and the entire system. Here, the research and development progress in modeling and simulation of flow batteries is presented. In addition to the most studied all‐vanadium redox flow batteries, the modelling and simulation efforts made for other types of flow battery are also discussed. Finally, perspectives for future directions on model development for flow batteries, particularly for the ones with limited model‐based studies are highlighted.

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Passive fuel cells, using diffusion and natural convection for fuel delivery, are regarded as promising candidates for powering portable devices including mobile phones and laptops. However, the performance of passive fuel cells which employ typical liquid alcohol fuels are still limited, which thereby greatly hampered their commercialization progress. Recently, a novel concept named the electrically rechargeable liquid fuel (e-fuel), with its rechargeability, cost-effectiveness, and superior reactivity, has attracted increasing attention. In this study, a passive fuel cell using the liquid e-fuel and the ambient air for electricity production is designed and fabricated. This passive fuel cell is demonstrated to achieve a peak power density of 116.2 mW cm −2 along with a stable operation for over 350 h, exhibiting great prospect for future applications.

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