Proving the pseudocapacitive nature of Cryolithionite as a novel electrode material for lithium-ion capacitors

We recently propose a new anode material, a Li-fluoride garnet (Na3Fe2Li3F12), with pseudocapacitive properties, and no irreversible capacity loss for lithium-ion capacitor. Despite evidence from electrochemical studies the pseudo-capacitive nature has not definitely been proven, due to the absence of information about redox chemistry, changes in structure and microstructure, which would allow to distinguish, e.g., between pseudocapacitive or conversion-type behaviour. The aim of this experiment is, therefore, to identify and track changes in structure, lattice parameter, and oxidation states, as well as potential strain causing amorphization during cycling by using operando XRD in combination with EXAFS and PDF. The results will provide unique quantitative data on the structural response of Cryolithionite under electrochemical load in a Li-ion capacitor, hence, open the door for the systematic further improvement of this novel class of material pushing the field of Li-ion capacitors.