Zinc–air batteries (ZABs) have recently attracted
revived
interest. However, critical issues pertaining to the labile zinc anode
and sluggish air cathode have yet to be adequately addressed. Here,
we demonstrate a redox-mediated zinc–air fuel cell (RM-ZAFC)
to tackle the above problems. Upon operation, the complex cobalt triisopropanolamine
serves as an electrolyte-borne electron carrier and homogeneous catalyst
to boost the 4e– oxygen reduction reaction in a
separate gas diffusion tank, which makes the system free of a sophisticated
air electrode. With mediation by the ultrafast reaction with a phenazine
derivative, zinc could be liberated from the electrode to a separate
“fuel” tank at high utilization (>90%), making it
feasible
to be “refueled” after it is depleted. Above all, RM-ZAFC
has the combined advantages of both ZABs and alkaline fuel cells and
can operate with high energy density, good flexibility, scalability
and safety at low cost and thus is promising for various energy storage
applications.
Zinc-based redox flow battery is regarded as one of the most promising electricity storage systems for large-scale applications. However, dendrite growth and the formation of “dead zinc” of zinc electrodes...
Efficient and cost‐effective technologies are highly desired to convert the tremendous amount of low‐grade waste heat to electricity. Although the thermally regenerative electrochemical cycle (TREC) has attracted increasing attention recently, the unsatisfactory thermal‐to‐electrical conversion efficiency and low power density limit its practical applications. In this work, a thermosensitive Nernstian‐potential‐driven strategy in the TREC system is demonstrated to boost its temperature coefficient, power density, and thermoelectric conversion efficiency by rationally regulating the activities of redox couples at different temperatures. With a Zn anode and [Fe(CN)6]4−/3−‐guanidinium as the catholyte, the TREC flow cell presents an unprecedented average temperature coefficient of −3.28 mV K−1, and achieves an absolute thermoelectric efficiency of 25.1% and apparent thermoelectric efficiency of 14.9% relative to the Carnot efficiency in the temperature range of 25–50 °C at 1 mA cm−2. In addition, a thermoelectric power density of 1.98 mW m−2 K−2 is demonstrated, which is more than 7 times the highest power density of reported TREC systems. This activity regulation strategy can inspire research into high‐efficiency and high‐power TREC devices for practical low‐grade heat harnessing.
With the increasing penetration of renewable energy sources in the past decades, stationary energy storage technologies are critically desired for storing electricity generated by non-dispatchable energy sources to mitigate its impact on power grids. Redox flow batteries (RFBs) stand out among these technologies due to their salient features for large-scale energy storage. The primary obstacle to the successful industrialization and broad deployment of RFBs is now their high capital costs. A feasible route to cost reduction is to develop high-power RFBs, since the increase in power performance has a pronounced impact on the cost of RFB systems. In this review, an in-depth inspection of the power performance of RFBs is presented. Perspectives for the future development of high-power RFBs along with implementable strategies addressing both the intrinsic and extrinsic limiting factors are summarized, which are expected to provide useful references steering the further improvement in the power density of RFBs. redox flow batteries, power density, aqueous electrolytes, redox kinetics, polarizations
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