Tomographic reconstruction of oxygen orbitals in lithium-rich battery materials

Abstract

Electrification of heavy-duty transport and aviation requires a paradigm shift in electrode 1 materials and anionic redox represents one possible approach to meeting these demanding targets. However, questions on the validity of the O 2− /O − oxygen redox paradigm remain open and alternative explanations for the origin of the anionic capacity have been proposed because electronic orbitals associated with redox reactions cannot be measured by standard experiments. Here, by using high energy x-ray Compton measurements along with firstprinciples modeling, we show how the electronic orbital that lies at the heart of the reversible and stable anionic redox activity can be imaged and visualized and its character and symmetry can be determined. Differential changes in the Compton profile with Li concentration are shown to be sensitive to the phase of the electronic wave function and carry signatures of electrostatic and covalent bonding effects. Our study not only provides a picture of the workings of a lithium-rich battery at the atomic scale but also suggests pathways for improving existing cathodes and designing new ones.

Tailoring Co3d and O2p Band Centers to Inhibit Oxygen Escape for Stable 4.6 V LiCoO2 Cathodes

“…Effective detection of lattice oxygen activity requires new techniques that are more sensitive to the chemical state of lattice oxygen. [23] To experimentally probe the nature of oxidized oxygen at different charging states in the Bare-LCO and LM0.01COF0.02 samples,OK-edge RIXS was performed as shown in Figure 3a and d. Both the Bare-LCO and LM0.01COF0.02 samples show similar features in their pristine form and discharge state.H owever,i nt he charge state,the feature that the oxygen redox activity (O 2À !O 2 nÀ ) is more or less constant for the LM0.01COF0.02 samples after two cycles,w hile it clearly increases for the Bare-LCO.T his indicates that oxygen redox in the particle shell of the LM0.01COF0.02 sample is less involved in the chemical reaction.…”

Study of Rechargeable Batteries Using Advanced Spectroscopic and Computational Techniques

“…Moreover, X-ray resonant inelastic scattering (RIXS) at the oxygen K edge is an experimental soft X-ray technique capable of directly probing the oxygen activity in the redox processes [14]. On the other hand, the use of high-energy X-ray scattering at synchrotron radiation facilities has enabled the study of the electronic wavefunctions associated with redox processes by means of Compton scattering [9,[15][16][17]. An advantage of X-ray Compton scattering is that it can be effectively applied to commercial batteries, thanks to the high penetration power of high-energy X-rays [18,19].…”

“…The challenges in this endeavour are many. It is important to first realise that the challenges faced present a complexity implicating a hierarchy of scales, i.e., from the atomic scale [9] to the macroscopic scale [10]. Their study calls for joint experimental and theoretical work, as well as an interdisciplinary approach, involving physics, chemistry, materials science, and engineering, as the various scale hierarchies are coupled to each other and to the functionality of the Li-ion batteries in an intricate manner.…”

Magnetic Compton Scattering Study of Li-Rich Battery Materials

“…Details of the anionic redox mechanisms are not fully understood because experiments that can directly probe redox orbitals are limited. In this connection, Hafiz et al have reconstructed the orphaned O − 2p orbital of LTMO in momentum space by combining high-energy X-ray Compton scattering with accurate first-principles calculations [3]. This visualization was enabled by the bulk sensitivity of the Compton scattering technique.…”