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

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Advanced battery electrode materials require careful design on a nanoscale. Often, even slight changes in morphology and composition result in great changes in the efficiency and stability. Therefore, it is fundamental to correlate synthesis parameters with material performance and resulting electrochemical metrics. Only by this way, we can establish a knowledge platform rather than relying on empiric trial-and-error. A great example for the challenges in nanoengineering of materials are metal sulfides. Metal sulfides have a huge potential as battery electrodes due to their inherent high theoretical capacity. However, while performing in such application, they face fast capacity drop that leads to an overall inefficient device. This is because they undergo great volumetric variation during charge/discharge cycles, causing particle aggregation, electrode cracking, besides other effects that compromise material stability. In addition, metal sulfides in general are not conductive being often combined with carbon additives to improve charge mobility. The lack of proper interaction or blending of these components result in a diminished conductivity along the cycles hindering the electrode performance. To capitalize metal sulfides capacity with a long-term stability and efficiency, material structure must be carefully considered.The present application focuses on Prussian blue and analogues (PBA - M[M’(CN)6]) as precursors for metal sulfide preparation. PBA are cheap, easy to prepare and are water and air stable, different from many metal oxide and sulfides precursors. Acting as both metal and carbon source, they can be converted into metal oxides, porous carbon or hybrids between those. By adding a sulfur source, they can produce metal sulfides with high porosity. Currently there are no consistent studies on the precursor character and treatment parameters in the resulting derivative with studies often limited to one sample-one treatment. Preliminary work by the applicant demonstrates the feasibility of the project and the same time shows the complex relation between synthesis parameters and resulting properties. This proposal aims to fill the gap of the link between derivatization parameters and electrochemical properties of metal sulfides produced from PBA. The project involves a systematic derivatization/sulfidation of PBA under different conditions, where morphology, composition and structure are carefully characterized. By doing so, we will be able to design a PBA-derived metal sulfide that can fulfill electrode requirements for a long-term stable battery. This will be demonstrated by tuning derivative properties through synthesis control and evaluating their electrochemical performance as battery cathodes in combination with post-mortem analysis to elucidate material transformations within testing. The project is an important milestone for the development of the applicant as an independent researcher.