Edge-Propagation Discharge Mechanism in CF_<i>x</i> Batteries—A First-Principles and Experimental Study

Graphite fluoride (CFx) cathodes coupled with lithium anodes yield one of the highest theoretical energy densities (>860 Wh/g) among primary batteries. In practice, observed discharge voltage (~2.5 V) is significantly lower than thermodynamic limits (>4.5 V), rate low, and so far Li/CFx has only been used in Understanding mechanism at atomic length scales will improve practical CFx density, capability, rechargeability. So far, purely experimental techniques have not identified correct or explained voltage. We apply Density Functional Theory calculations to demonstrate that a CFx-edge propagation based on insertion CF/C boundary partially discharged exhibits range 2.5 2.9 V -- depending whether solvent molecules are involved. The voltages dependence agrees our galvanostatic intermittent titration technique measurements. predicted kinetics consistent operations. Finally, we predict rechargeability under application high potentials, along charging pathway different from discharge. Our work represents general, quasi-kinetic framework understand conversion cathodes, circumventing widely phase diagram approach which most likely does because equilibrium conditions attained this system.