In this work, we explored the vast materials database of sulphate-based insertion materials for potassium-ion batteries. Apart from containing economic and Earth-abundant elements, sulphate-based minerals can, in principle, exhibit high theoretical capacities owing to their low molecular weight. In our exploration of the sulphate chemistry for potassium-ion batteries, we are able to take advantage of an extensive database of known minerals, particularly the bimetallic and hydrated sulphate derivatives such as karpovite, alunite, fedotovite K2Cu3O(SO4)2, langbeinite (K2M2(SO4)3; M=Fe, Mn, Cu, Co, Ni), picromerite, mereiterite, etc. One such mineral is goldichite, with the general chemical formula K2M(SO4)2・nH2O. Noting that its structure contained possible K-ion diffusion channels, we attempted to design a yavapaiite insertion compound for potassium batteries. We will highlight the syntheses and electrochemical performance in K-ion cells of such sulphate-based minerals.
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