Iron oxide is promising for use in aqueous energy storage devices due to the high capacity, but one of the most challenging problems is cycling instability within the large potential window that results from the complete quasi‐conversion reaction. Herein, a conformal surface coating strategy toward iron oxide via atomic layer deposition (ALD) is presented and an Fe₃O₄@TiO₂ core–shell nanorod array anode is reported that exhibits remarkable cycling performance exceeding 30 000 times within a wide potential window in neutral lithium salt electrolyte. ALD offers a uniform and precisely controllable TiO₂ shell that not only buffers the inner volume expansion of Fe₃O₄, but also contributes extra capacity through Li⁺ intercalation/de‐intercalation and helps to alleviate the water electrolysis. Furthermore, by pairing with a pseduocapacitive cathode of V₂O₃@carbon and using a hydrogel electrolyte of PVA‐LiCl, a unique flexible quasi‐solid‐state hybrid supercapacitor can be assembled. With a high voltage of 2.0 V, the device delivers high volumetric energy and power densities (2.23 mWh cm⁻³, 1090 mW cm⁻³), surpassing many recently reported flexible supercapacitors. This work highlights the importance of ALD conformal multifunctional shell to instable nanoarray electrodes in aqueous electrolytes and brings new opportunities to design advanced aqueous hybrid energy storage devices.

中文翻译：

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氧化铁纳米棒转化电极上的共形多功能二氧化钛壳可实现超过30 000次循环的高稳定性

氧化铁由于其高容量而有望用于水性储能设备，但最具挑战性的问题之一是由于完全的准转化反应而导致的大的潜在窗口内的循环不稳定性。在此，提出了一种通过原子层沉积（ALD）对氧化铁进行共形表面涂覆的策略，并且据报道，Fe ₃ O ₄ @TiO ₂核-壳纳米棒阵列阳极在宽的潜在窗口内具有超过3万次的出色循环性能。在中性锂盐电解质中。ALD提供了均匀且可精确控制的TiO ₂壳，不仅可缓冲Fe ₃ O ₄的内部体积膨胀，但通过Li ⁺插层/脱插层也可提供额外的容量，并有助于减轻水的电解。此外，通过与V ₂ O ₃ @碳的假阴极电容配对并使用PVA-LiCl水凝胶电解质，可以组装独特的柔性准固态混合超级电容器。与2.0伏的高电压，该器件提供了高体积能量密度和功率密度（2.23 mWh的厘米^-3，1090毫瓦厘米^-3），超过了最近报道的许多柔性超级电容器。这项工作突显了ALD保形多功能壳对于水性电解质中不稳定的纳米阵列电极的重要性，并为设计先进的水性混合储能装置带来了新的机遇。