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Tailoring sulfidation and derivatization of Prussian blue analogues towards electrochemically stable metal sulfides/carbon nanohybrids

Subject Area Synthesis and Properties of Functional Materials
Term from 2021 to 2022
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 463914313
 
Final Report Year 2023

Final Report Abstract

The sharp rise in demand for batteries requires the development of more sustainable and easier to recycle battery materials, substituting costly and strategic elements like Li, Ni and Co by widely and more evenly available ones like Na and Fe in the electrode materials. Prussian blue (PB) and its analogues (PBA, AM[M’(CN)6]) are cheap, non-toxic, water and air-stable and can be entirely synthesized in water-based methods, showing a high degree of sustainability. Given PBA porous framework, they have been used as templates to prepared the so-called PB derivatives (PBD) which present a booming number of compositions including metal oxides, sulfides, carbides, hybrids, and an array of morphologies. In this work, the PBA copper ironhexacyanoferrate(II) (CuPB) is explored as precursor to produce mixed Cu/Fe sulfides for Lithium-ion battery. To control the particle size, dopamine or tannic acid are added to the system and polymerized in situ during CuPB growth. The presence of the polymers favors K-rich CuPB while the thickness of the polymer shows key-role in preventing particle coarsening during sulfidation process and enable its application in LIB, which otherwise is prohibited due to lack of structural and electrochemical stability. Through mild thermal treatment conditions (300 °C, 10 min), carbon-coated (K)CuFeS2 is produced. Standard coating with NMP and PVDF binder are explored together with greener alternatives like ethanol and PVP to process the PBD for electrochemical testing. The C-coated KCuFeS2 electrodes showed capacities up to 800 mAh/g at 10 mA/g with nearly 100% capacity recovery after rate handling and a capacity of 380 mAh/g at 250 mA/g after 500 cycles. KCuFeS2 showed to be sensitive to water and prevented the substitution of NMP with water in slurry preparation. The work demonstrates that control over PBD properties is not trivial and can be highly influenced by minor changes in PBA synthesis.

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