Flexible supercapacitors (FSCs) are considered to be a promising electrochemical energy source for wearable electronic products. However, the absence of high-performance electrode materials and effective manufacturing techniques of devices hinder the volume production of FSCs. Here, a facile surface-etching method is investigated to prepare high-performance nickel hexacyanoferrate (NiHCF) electrode materials, and further, a screen-printing strategy is employed to realize high-volume production of FSCs. Compared with conventional NiHCF electrodes, the Na₂Ni[Fe(CN)₆]-based electrode with surface defect offers a specific capacity of 184 C g⁻¹ (100 C g⁻¹ for conventional NiHCF), and its capacity retention is 91% after 10 000 cycles. According to density functional theory (DFT) calculations, the excellent cycling stability can be attributed to the negligible structural distortion during the Na⁺ insertion/extraction process (∼6% volume change). Subsequently, symmetric FSCs are constructed by printing the NiHCF electrode materials on flexible PET substrates, displaying excellent areal capacitance of 7.3 mF cm⁻² (0.1 mA cm⁻²) and energy density and power density of 0.65 μW h cm⁻² and 0.4 mW cm⁻², respectively. The surface-defect engineering provides a low-cost strategy to construct nickel hexacyanoferrate materials with outstanding electrochemical properties. The printed electronic techniques we have demonstrated for large-scale and low-cost printing FSCs applications are inspiring.

中文翻译：

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用于高性能印刷柔性超级电容器的六氰基铁酸镍材料的表面缺陷工程

柔性超级电容器 (FSC) 被认为是可穿戴电子产品的一种很有前途的电化学能源。然而，缺乏高性能的电极材料和有效的器件制造技术阻碍了FSCs的量产。在这里，研究了一种简便的表面蚀刻方法来制备高性能六氰基铁酸镍 (NiHCF) 电极材料，并进一步采用丝网印刷策略实现 FSC 的大批量生产。与传统的NiHCF电极相比，具有表面缺陷的Na ₂ Ni[Fe(CN) ₆ ]基电极的比容量为184 C g ^-1 (100 C g ^-1对于传统的NiHCF)，10 000次循环后其容量保持率为91%。根据密度泛函理论 (DFT) 计算，出色的循环稳定性可归因于 Na ⁺插入/脱出过程中可忽略不计的结构变形（~6% 体积变化）。随后，通过在柔性 PET 基板上印刷 NiHCF 电极材料构建对称 FSC，显示出 7.3 mF cm ^-2（0.1 mA cm ^{-2 ）的优异面电容以及 0.65 μW h cm -2}和 0.4 mW的能量密度和功率密度厘米^-2， 分别。表面缺陷工程为构建具有出色电化学性能的六氰基铁酸镍材料提供了一种低成本策略。我们为大规模和低成本印刷 FSC 应用展示的印刷电子技术令人鼓舞。