Accessing polyanionic redox in high voltage Li-rich thiophosphates
In the search for novel cathodes for lithium-ion batteries, Li-rich sulphides are attracting increasing interest due to the possibility of multielectron redox chemistry. However, despite the success of polyoxyanion cathodes such as LiFePO4, their thiophosphate counterparts are largely unexplored, and the understanding of their redox processes remains incomplete. Here, we investigate the Li-rich thiophosphate Li2FeP2S6 which exhibits the highest voltage (3V) for a sulphide, but shows limited lithium extraction due to phase instability at high states of charge. Isostructural transition metal™ substitutions are explored by ab initio simulations accelerated by machine learning techniques, identifying a previously unknown Mn-substituted compound, Li2Fe0.8Mn0.2P2S6, which exhibits higher capacity than the pure Fe system. HAXPES and molecular dynamics simulations indicate that Mn incorporation activates S-S dimerization and polyanionic redox beyond the TM redox capacity with no evidence of TM migration.

This study widens the possibilities to explore new thiophosphate structures as lithium-ion cathode materials.
Date: 10 June 2022, 14:00 (Friday, 7th week, Trinity 2022)
Venue: 21 Banbury Road Lecture Theatre and livestream: https://ox.cloud.panopto.eu/Panopto/Pages/Viewer.aspx?id=5db6d881-013b-494e-9c14-aeac00914a78
Speaker: Dr Pezhman Zarabadi-Poor (University of Oxford)
Organising department: Department of Materials
Organiser: Joseph Prentice (University of Oxford)
Organiser contact email address: joseph.prentice@materials.ox.ac.uk
Part of: Oxford Advanced Materials Network
Booking required?: Not required
Audience: Members of the University only
Editor: Samantha Pearce