ELECTRON-ANION EXCHANGE AS A NEW MECHANISM FOR NON-REDOX FLUORIDE-ION BATTERY ELECTRODES

Typically, the insertion of ions into a crystalline material is accompanied by the oxidation or reduction of atoms in the host lattice. For example, when Li+ ions enter a LiCoO2 cathode during electrochemical discharge, the oxidation state of Co atoms changes from 4+ to 3+. However, I recently discovered a new insertion phenomenon where anion intercalation into materials called electrides does not perturb the oxidation states of the host atoms. Electrides are ionic materials in which electrons act as the negative charge balance instead of anions, and the “electride electrons” occupy lattice sites separate from atomic nuclei. The chemical nature of electrides allows for exchange of interlayer electrons with small anions, such as F-, because of their similar size and charge, avoiding the need to oxidize or reduce the electride lattice. I identified an opportunity to use “electron-anion exchange” as a new mechanism for anion charge storage, where electrides offer high charge capacities (> 260 mAh/g) and large voltages (< 4 V) for fluoride-ion batteries. In this dissertation, I describe the suitability of electrides for high energy density fluoride-ion battery electrodes and give experimental evidence for the electron- anion exchange phenomenon. Additionally, I provide a brief history of electrides and fluoride- ion batteries with an explanation of how batteries work and common methods of electrochemical testing.Doctor of Philosoph