Visualizing redox orbitals and their potentials in olivine materials for advanced lithium-ion batteries

The key reactions that take place in lithium batteries are reduction-oxidation (redox) reactions, which involve transfer of conduction electrons from the lithium anode to an orbital of the cathode. Our study of high-energy x-ray Compton scattering spectroscopy on olivine lithium iron phosphate $(LiFePO_{4})$ shows that inelastic scattering spectra of high-energy photons yield faithful reconstructions of the redox orbitals. The knowledge of the redox orbital-momentum distribution allows the extraction of information related to kinetic energies involved in the redox reactions and the visualization of trends in the voltage. Our results demonstrate that x-ray Compton scattering spectroscopy provides unique descriptors for monitoring fundamental quantum mechanical effects determining the battery voltage in olivine materials.