Liao Jiaying, Yuan Zeyu, Hu Qiao, Sheng Xinru, Song Lili, Xu Yifan, Du Yichen, Zhou Xiaosi
School of Chemistry and Materials Science, Nanjing Normal University, Nanjing, 210023, China.
College of Chemical Engineering, Nanjing Forestry University, Nanjing, 210037, China.
Angew Chem Int Ed Engl. 2024 Aug 26;63(35):e202409145. doi: 10.1002/anie.202409145. Epub 2024 Jul 26.
Metal hexacyanoferrates (HCFs) are regarded as promising cathode materials for potassium-ion batteries (PIBs) on account of their low cost and high energy density. However, the difficult-to-remove [Fe(CN)] vacancies and crystal water lead to structural instability and capacity deterioration as well as the stereotype of poor thermostability of conventional HCFs. Herein, we report (100) face-oriented potassium magnesium hexacyanoferrate (KMgHCF) nanoplates with low [Fe(CN)] vacancies and high crystallinity, enabling thermostability up to 550 °C, high-temperature carbon coating and crystal water elimination. The as-obtained KMgHCF/C nanoplates exhibit superior potassium storage properties, including a large reversible capacity of 84.6 mAh g, a high voltage plateau of 3.87 V, excellent long-term cycling performance over 15000 cycles and high rate capability at 5 A g. The unprecedented cycling stability of KMgHCF/C is attributed to the synergistic effect of a highly reversible two-phase reaction, low [Fe(CN)] vacancies and no crystal water, a specially exposed steady (100) surface, and a protective carbon coating. This work provides a new material selection and modification strategy for the practical application of HCFs in PIBs.
金属六氰合铁酸盐（HCFs）因其低成本和高能量密度而被视为钾离子电池（PIBs）颇具前景的阴极材料。然而，难以去除的[Fe(CN)]空位和结晶水会导致结构不稳定、容量衰减，以及传统HCFs热稳定性差的固有问题。在此，我们报道了具有低[Fe(CN)]空位和高结晶度的（100）面取向钾镁六氰合铁酸盐（KMgHCF）纳米片，其热稳定性可达550 °C，可实现高温碳包覆并消除结晶水。所制备的KMgHCF/C纳米片展现出优异的钾存储性能，包括84.6 mAh g的大可逆容量、3.87 V的高电压平台、超过15000次循环的出色长期循环性能以及5 A g的高倍率性能。KMgHCF/C前所未有的循环稳定性归因于高度可逆的两相反应、低[Fe(CN)]空位和无结晶水的协同效应、特别暴露的稳定（100）表面以及保护性碳包覆。这项工作为HCFs在PIBs中的实际应用提供了一种新的材料选择和改性策略。
