Li₂TiS₃: Lithium Metal Sulphide Rocksalt As New Cathode Material for High Energy Batteries without Critical Materials

Most of the current Li-Ion cathodes use cobalt/nickel-based layered oxides as active materials. Due to the increasing demand of these critical and scarce elements in the coming years, it becomes urgent to develop new materials based on abundant elements. In 2014, Sakuda et al. introduce new sulphide rocksalt materials which can deliver a capacity higher than 400 mAh/g at 2.2 Volts.1 In 2019, a project named Spider funded by the European Union's Horizon 2020 research and innovation programme started with the objective to develop and use these materials in Li-Ion batteries. Several synthesis methods have been evaluated to produce Li2TiS3 materials. High capacities are obtained with these materials but they suffer from a poor cycle life. Several characterizations and experiments have been performed in order to obtain a better understanding of the material evolution during cycling. Ex-situ XRD are in good agreement with previous results reported by Sakuda et al. and we completed the investigation thanks to Ex-situ SEM and XPS characterizations.2 We highlight that the material is partially oxidized during the cathode manufacturing process which lead to a loss of the lithium content in the materials structure. Our conclusions will be helpful to overcome these issues. References (1) Sakuda, A.; Takeuchi, T.; Okamura, K.; Kobayashi, H.; Sakaebe, H.; Tatsumi, K.; Ogumi, Z. Rock-Salt-Type Lithium Metal Sulphides as Novel Positive-Electrode Materials. Sci. Rep. 2014, 4, 4883. https://doi.org/10.1038/srep04883. (2) Sakuda, A.; Ohara, K.; Kawaguchi, T.; Fukuda, K.; Nakanishi, K.; Arai, H.; Uchimoto, Y.; Ohta, T.; Matsubara, E.; Ogumi, Z.; et al. A Reversible Rocksalt to Amorphous Phase Transition Involving Anion Redox. Sci. Rep. 2018, 8 (1), 1–6. https://doi.org/10.1038/s41598-018-33518-4. Figure 1