First principles study of layered scandium disulfide for use as Li-ion and beyond-Li-ion batteries

The growing demand for high efficiency portable batteries has prompted a deeper exploration for alternative cathode materials. Due to low Earth abundance, scandium has not received much attention, however its low atomic mass makes it ideal for high gravimetric capacity electrodes. Here we have performed a comprehensive first-principles study to assess the performance of layered ScS2 as a potential cathode for lithium-ion and beyond-lithium-ion batteries. We have explored the configuration space of ScS2 and its intercalated compounds using a mix of machine learning and ab initio techniques, finding the ground state geometry to be layered in nature. This layered structure is found to have a high voltage, reaching above 4.5 V for Group I intercalants, ideal volume expansions below 10% for lithium and magnesium intercalation, is electronically conductive, and is ductile once intercalated. Of the intercalants considered, we find that lithium is the best choice for cathode applications, for which we have used a combination of thermodynamic phase diagrams, ab intio phonon calculations, and evaluation of the elastic tensor to conclude that ScS2 possesses a reversible capacity of 182.99 mA h g(-1), on par with current state of the art cathode materials such as LiCoO2, NMC, and NCA. Finally, we substitute foreign metal species into the ScS2 material to determine their effect on key cathode properties, but find that these are overall detrimental to the performance of ScS2. This does, however, highlight the potential for improvement if scandium were mixed into other layered systems such as the layered transition metal oxides.

Automated summary

The study explores the potential of layered ScS2 as a cathode material for high efficiency portable batteries. Through a comprehensive first-principles study, it is found that ScS2 possesses desirable properties such as high voltage, low volume expansion, electronic conductivity, and ductility once intercalated. Lithium is determined to be the best choice for cathode applications, with ScS2 exhibiting a reversible capacity on par with current state of the art cathode materials. The substitution of foreign metal species into ScS2 is found to be detrimental to its performance, suggesting the potential for improvement by mixing scandium into other layered systems.