Abstract
The 3d transition metal layered oxides derived from LiCoO₂ are critical components of our lithium-ion battery technology. Simply put, the Co and Ni ions are expected to oxidize to formal 4+ configurations when all the lithium is extracted upon charging. This is based on simple electron counting within crystal field if the oxygen ions remain formally O^2-. In real Li-ion batteries, the layered oxides are never fully delithiated during cycling because of degradation (oxygen loss) issues at high states of charge i.e. above 50% of lithium extraction. As a result, the ionic approximation has proven Goodenough (pun intended) to date. However, the push to increase energy densities by suppressing degradation has led to more attention on the redox mechanisms at high states of charge. In addition, lithium excess compounds have demonstrated capacities that cannot be accounted from by formal metal oxidation and indicate oxygen can participate in the charge compensation.

At WMG, we have led the integration of state-of-the-art Ni-rich Li-ion battery manufacturing of industry-relevant formats with advanced x-ray characterization. Here, I will summarize our work connecting a suite of x-ray characterization (including in-house operando EXAFS) revealing how the oxygen ions facilitate the charge compensation even in conventional layered oxides. These studies are supported by beyond density functional theory (DMFT) methods for spectroscopic simulations that reproduce our spectral observations. These findings revise the description of oxygen redox and explain why these systems suffer from accelerated oxygen loss at high states of charge.

Biography
Louis Piper is Professor of Battery Innovation and heads the Electrochemical Materials group in the Energy Directorate at WMG. He co-leads the renewed Faraday Degradation project with Prof. Clare Gray, along with leading the Faraday cell builds project upscaling new cathode materials from FutureCat consortium into real formats to improve performance within the Degradation Project. He has published over 175 papers (h index = 56) and was recently interviewed on BBC 2 “Secret Genius of Modern Life”. Louis did his PhD in surface Physics at Warwick University (2006) before moving stateside. First as beamline contact scientist for Boston University at NSLS, BNL (2006-2010) and then as faculty at State University of New York, Binghamton (Assistant Professor to Full professor, 2010-2020) where he worked alongside Nobel Laureate Prof. M. Stanley Whittingham on several projects (most notably NECCES). He returned to Warwick in 2020. With hindsight, he would not recommend moving in a pandemic.

Everyone is welcome to attend, and if anyone wishes to meet with Louis please get in touch with struan.simpson@warwick.ac.uk