Electrochemical variability of natural mineral mixtures as electrode materials in Li-ion batteries.

Natural mineral systems can be effectively used to make battery material supply chains more secure and sustainable. However, the impact of their multi-mineral electrochemistry must be considered for effective deployment. Mine tailings are shown as a potential sustainable natural mineral source. A simplified ternary system of pyrite, quartz and muscovite was examined for its trends in electrochemical performance. Mixing of minerals is shown to adversely affect charge transfer impedance (R ct) and diffusion coefficient (D Li+ ) values post-cycling; R ct values are 10 times greater for mixtures than pure phase minerals, and D Li+ values are an order of magnitude lower than pure phase minerals. Within mixtures, the component of capacity from pyrite decays more rapidly than in a pure mineral phase. A comparison with two mine tailings reveals the inclusion of lesser amounts of pyrite in a majority silicate mixture to boost electrochemical performance, while the opposite leads to reduced performance. The results convey that a clear link between mineral composition and expected electrochemical performance is required to fully realise the benefits of mixed natural mineral sources for sustainable battery electrodes.