Secondary Zn‐air batteries with stable voltage and long cycle‐life are of immediate interest to meet global energy storage needs at various scales. Although primary Zn‐air batteries have been widely used since the early 1930s, large‐scale development of electrically rechargeable variants has not been fully realized due to their short cycle‐life. In this work, we review some of the most recent and effective strategies to extend the cycle‐life of Zn‐air batteries. Firstly, diverse degradation routes in Zn‐air batteries will be discussed, linking commonly observed failure modes with the possible mechanisms and root causes. Next, we evaluate the most recent and effective strategies aimed at tackling individual or multiple of these degradation routes. Both aspects of cell architecture design and materials engineering of the electrodes and the electrolytes will be thoroughly covered. Finally, we offer our perspective on how the cycle‐life of Zn‐air batteries can be extended with concerted and tailored research directions to pave the way for their use as the most promising secondary battery system of the future.
Developing a high-performance ORR (oxygen reduction reaction) catalyst at low cost has been a challenge for the commercialization of high-energy density and low production cost aluminium-air batteries. Herein, we report a catalyst, prepared by pyrolyzing the shell waste of peanut or pistachio, followed by concurrent nitrogen-doping and FeCo alloy nanoparticle loading. Large surface area (1246.4 m2 g-1) of pistachio shell-derived carbon can be obtained by combining physical and chemical treatments of the biomass. Such a large surface area carbon eases nitrogen doping and provides more nucleation sites for FeCo alloy growth, furnishing the resultant catalyst (FeCo/N-C-Pistachio) with higher content of N, Fe, and Co with a larger electrochemically active surface area as compared to its peanut shell counterpart (FeCo/N-C-Peanut). The FeCo/N-C-Pistachio displays a promising onset potential of 0.93 V vs. RHE and a high saturating current density of 4.49 mA cm-2, suggesting its high ORR activity. An aluminium-air battery, with FeCo/N-C-Pistachio catalyst on the cathode and coupled with a commercial aluminium 1100 anode, delivers a power density of 99.7 mW cm-2 and a stable discharge voltage at 1.37 V over 5 h of operation. This high-performance, low-cost, and environmentally sustainable electrocatalyst shows potential for large-scale adoption of aluminium-air batteries.
Design and synthesis of low‐cost and efficient bifunctional catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in Zn‐air batteries are essential and challenging. We report a facile method to synthesize heterostructure carbon consisting of graphitic and amorphous carbon derived from the agricultural waste of red bean pods. The heterostructure carbon possesses a large surface area of 625.5 m2 g−1, showing ORR onset potential of 0.89 V vs. RHE and OER overpotential of 470 mV at 5 mA cm−2. Introducing hollow FeCo nanoparticles and nitrogen dopant improves the bifunctional catalytic activity of the carbon, delivering ORR onset potential of 0.93 V vs. RHE and OER overpotential of 360 mV. Electron energy‐loss spectroscopy (EELS) O K‐edge map suggests the presence of localized oxygen on the FeCo nanoparticles, suggesting the oxidation of the nanoparticles. Zn‐air battery with these carbon‐based catalysts exhibits a peak power density as high as 116.2 mW cm−2 and stable cycling performance over 210 discharge/charge cycles. This work contributes to the advancement of bifunctional oxygen electrocatalysts while converting agricultural waste into value‐added material.
Zinc–air batteries with seawater
electrolyte utilize abundant
and cheap resources. However, it requires an electrocatalyst with
high bifunctional activity in seawater. In this work, a carbon electrocatalyst
is obtained via one-step pyrolysis of the shell waste of cranberry
beans. During the oxygen reduction reaction (ORR) in seawater electrolyte,
the cranberry bean shell-derived carbon catalyst exhibits an ORR onset
potential of 0.69 V vs RHE and an ORR saturating current density of
2.93 mA cm–2, which are promising compared to the
ORR performance of Pt/C in seawater electrolyte (0.78 V vs RHE and
3.15 mA cm–2). During OER (oxygen evolution reaction)
in seawater electrolyte, the carbon catalyst shows an overpotential
of 582 mV at 5 mA cm–2, 35 mV smaller than the commercial
Ir/C catalyst (617 mV). Furthermore, when the catalyst is applied
to the zinc–air battery with seawater electrolyte, the cell
is able to exhibit discharge and charge voltages of 0.93 and 2.2 V,
respectively, which are stable for more than 120 cycles of the cycling
test. This work highlights the fabrication of metal–air batteries
with cost-effective and sustainable resources.
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