In the search for more energy- and power- dense battery materials, the cathode is most often the component that is engineered to boost operating voltage and capacity. However, new approaches to battery design have yielded performance improvements by designing electrolytes with reactive species that increase capacity and energy density of full-cells. These approaches borrow insights from commercial battery technologies such as Pb-H₂SO₄, Li-SO₂, or Li-SOCl₂, where the cathodic reaction involves liquid-phase active species^1–3, while employing solid-phase cathode materials.

To better understand how specific examples of electroactive electrolytes improve rather than impede performance, our work focuses on two battery chemistries: a primary Li-CFx cell with an irreversible electrolyte reaction, and a secondary Li-LMR cell with a reversible electrolyte reaction. For each case, we develop a 1-D COMSOL model to investigate how the reaction of electrolyte species affects cell impedance, impacts Li cation transport, alters the electrolyte conductivity, and finally how each of these mechanistically impact the energy and power density of the cell. Our modeling work is complemented by experimental studies that measure important electrolyte and cathode properties at various states of discharge or cycling.

(1) Park, H.; Lim, H.-D.; Lim, H.-K.; Seong, W. M.; Moon, S.; Ko, Y.; Lee, B.; Bae, Y.; Kim, H.; Kang, K. High-Efficiency and High-Power Rechargeable Lithium–Sulfur Dioxide Batteries Exploiting Conventional Carbonate-Based Electrolytes. Nat. Commun. 2017, 8 (1), 14989. https://doi.org/10.1038/ncomms14989.

(2) Schlaikjer, C. R.; Goebel, F.; Marincic, N. Discharge Reaction Mechanisms in Li / SOCl2 Cells. J. Electrochem. Soc. 1979, 126 (4), 513–522. https://doi.org/10.1149/1.2129078.

(3) Ruetschi, P. Aging Mechanisms and Service Life of Lead–Acid Batteries. J. Power Sources 2004, 127 (1–2), 33–44. https://doi.org/10.1016/j.jpowsour.2003.09.052.