Abstract An ultrafast (∼20 min), inexpensive and scalable ice crystal-assisted precipitation approach was developed to synthesize unique self-assemblies of nickel ferrite nanoparticles (NiFe2O4 NPs) and zinc ferrite nanorods (ZnFe2O4 NRs) that contain plenty of porous voids for supercapacitor applications. The void-rich NiFe2O4 NPs and ZnFe2O4 NRs provide the required electroactive sites, multiple redox couples, and fast ion transportation pathways for electrolyte ions. Due to the formation of these self-assembled porous networks of nanostructures and their high specific surface area, NiFe2O4 NP- and ZnFe2O4 NR-based electrodes demonstrate excellent charge storage properties. Particularly, the individual NiFe2O4 NP and ZnFe2O4 NR electrodes manifest high specific capacities of 1403 and 1005 C g−1 at a current density of 1 A g−1, respectively, and excellent durability with a high capacity retention (>97%) for up to 15,000 cycles. A flexible NiFe2O4 NP//ZnFe2O4 NR-based asymmetric supercapacitor (ASC) device was fabricated using NiFe2O4 NPs as the positive electrode, ZnFe2O4 NRs as the negative electrode, and a PVA-KOH electrolyte. Importantly, the flexible NiFe2O4 NP//ZnFe2O4 NR device exhibits a superhigh energy density of 99.55 Wh kg−1 at a power density of 1.28 kW kg−1. During the long-term stability tests, this flexible ASC device shows a capacity retention of 95% after 15,000 GCD cycles. Thus, the present work offers an alternative low-cost and rapid ice crystal-assisted precipitation approach for the development of self-assembled porous networks with void-rich structures to enhance the overall performance of energy storage devices.

中文翻译：

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用于柔性高能量密度非对称超级电容器的 NiFe2O4 和 ZnFe2O4 纳米结构的超快冰晶辅助合成

摘要 开发了一种超快（~20 分钟）、廉价且可扩展的冰晶辅助沉淀方法来合成独特的镍铁氧体纳米粒子 (NiFe2O4 NPs) 和锌铁氧体纳米棒 (ZnFe2O4 NRs) 的自组装，其中包含大量用于超级电容器的多孔空隙。应用程序。富含空隙的 NiFe2O4 NPs 和 ZnFe2O4 NRs 为电解质离子提供了所需的电活性位点、多个氧化还原对和快速离子传输途径。由于这些纳米结构的自组装多孔网络的形成及其高比表面积，NiFe2O4 NP-和 ZnFe2O4 NR 基电极表现出优异的电荷存储性能。特别是，单独的 NiFe2O4 NP 和 ZnFe2O4 NR 电极在 1 A g-1 的电流密度下分别表现出 1403 和 1005 C g-1 的高比容量，以及出色的耐用性和高达 15,000 次循环的高容量保持率 (>97%)。使用NiFe2O4 NPs作为正极，ZnFe2O4 NRs作为负极和PVA-KOH电解质制造了柔性NiFe2O4 NP//ZnFe2O4 NR基非对称超级电容器（ASC）器件。重要的是，柔性 NiFe2O4 NP//ZnFe2O4 NR 器件在 1.28 kW kg-1 的功率密度下表现出 99.55 Wh kg-1 的超高能量密度。在长期稳定性测试中，这种灵活的 ASC 设备在 15,000 次 GCD 循环后显示出 95% 的容量保持率。因此，目前的工作提供了一种替代的低成本和快速冰晶辅助沉淀方法，用于开发具有富空隙结构的自组装多孔网络，以提高储能设备的整体性能。