A novel low-cost and environment-friendly cathode with large channels and high structure stability for potassium-ion sto
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Published online 12 November 2020 | https://doi.org/10.1007/s40843-020-1512-0
A novel low-cost and environment-friendly cathode with large channels and high structure stability for potassium-ion storage 1,3†
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Weike Wang , Bifa Ji , Wenjiao Yao , Xinyuan Zhang , Yongping Zheng , Xiaolong Zhou , 6 1,3 1,2,3,4* Pinit Kidkhunthod , Haiyan He and Yongbing Tang ABSTRACT Potassium-ion batteries (KIBs) are promising candidates for large-scale energy storage due to the abundance of potassium and its chemical similarity to lithium. Nevertheless, the performances of KIBs are still unsatisfactory for practical applications, mainly hindered by the lack of suitable cathode materials. Herein, combining the strong inductive 2+ effect of sulphate and the feasible preparation of Fe -containing compounds in oxalate system, a compound with novel architecture, K4Fe3(C2O4)3(SO4)2, has been identified as a lowcost and environmentally friendly cathode for stable potassium-ion storage. Its unique crystal structure possesses an unprecedented two-dimensional framework of triple layers, with 3.379 Å interlayer distance and large intralayer rings in the size of 4.576×6.846 Å. According to first-principles simulations, such a configuration is favorable for reversible Kion migration with a very low volume change of 6.4%. Synchrotron X-ray absorption spectra and X-ray diffraction characterizations at different charging/discharging states and electrochemical performances based on its half and full cells further verify its excellent reversibility and structural stability. Although its performance needs to be improved via further composition tuning with multi-valent transition metals, doping, structural optimization, etc., this study clearly presents a stable structural model for K-ion cathodes with merits of low cost and environmental friendliness. Keywords: potassium-ion cathode, Fe-based polyanionic compound, low cost, environment friendly
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INTRODUCTION Due to the limited Li resources and their geographic unevenness, lithium-ion batteries (LIBs) can hardly satisfy large-scale energy storage fields for renewable energy sources such as solar, wind, etc., where the cost and environmental influence should be considered even in the sacrifice of energy densities to a certain extent [1–4]. Among potential alternatives, potassium-ion batteries (KIBs) are attracting intense academic and technological interest due to the abundance of potassium and its chemical similarity to lithium over sodium [5–7]. For KIB technologies, several families have been explored as anode materials with high capacity and long cyclability, including intercalation-type, conversion-type, and alloying type materials [8–16]. In comparison, the development of ideal cathode materials, such as Prussian blue analogues (PBAs), oxides, polyanions, and organics [17–22] are sluggish. For instance, despite of enormous investigations on PBAs, of which the three-dimensional (3D) open framework structure is promising for K-ion storage, the preparation of def
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