A Model of the Potassium-Oxygen Battery and its Application in Cathode Design

Abstract

The potassium-oxygen battery (KOB) is a new type of metal-oxygen battery with high rechargeability and long cycle life. Currently, the energy density is rather limited and must be improved for KOB to become a viable energy storage technology for practical applications. In this study, a two-dimensional, multiphase KOB model is developed to design an optimized cathode structure. The model is validated and is used to study the influence of cathode porosity, surface area, and thickness on the discharge behavior. Higher cathode porosity and surface area are found to increase the discharge capacity and lower the discharge overpotential. However, using a microporous cathode may not be ideal for KOB. The electronic transport properties of the discharge product KO2 are assessed, suggesting an effectively higher conductivity of KO2 than previously predicted. In consequence, the formation of large KO2 deposits with several µm thickness may effectively inhibit oxygen transport in microporous materials. Thus, a hierarchical cathode porosity together with an optimized current collector design may be the key to significantly higher discharge performance.

Hierarchical Porosity and Surface Oxygenation of Carbon-Based Cathodes Enhances Discharge Capacity and Decreases Discharge Overpotential of Potassium-Oxygen Batteries

“…Recently we were able to show that surface functionalization of a commercial carbon paper cathode with hydrophobic PTFE enhances the discharge capacity by improving the mass transport [23]. Further improvements we have achieved by O2 partial pressure increase [24], and by means of a very recently introduced physical-mathematical model, which describes the influence of cathode porosity and the microstructure on the discharge performance, we predicted that increasing cathode porosity and volumetric surface area is further supportive for the discharge performance [25]. Thereby it became evident that a combination of micropores and mesopores is particularly supportive to avoid oxygen transport limitations in inner cathode regions [26].…”

Hierarchical Porosity and Surface Oxygenation of Carbon-Based Cathodes Enhances Discharge Capacity and Decreases Discharge Overpotential of Potassium–Oxygen Batteries

“…Further improvements were achieved by an O2 partial pressure increase [22], and by means of a very recently introduced physical-mathematical model, which describes the influence of cathode porosity and the microstructure on the discharge performance. We predicted that increasing the cathode porosity and volumetric surface area is further supportive for the discharge performance [23]. Through this, it became evident that a combination of micropores and mesopores is particularly supportive to avoid oxygen transport limitations in inner cathode regions [23].…”

“…We predicted that increasing the cathode porosity and volumetric surface area is further supportive for the discharge performance [23]. Through this, it became evident that a combination of micropores and mesopores is particularly supportive to avoid oxygen transport limitations in inner cathode regions [23]. Therefore, a hierarchical pore design of cathode material is anticipated to be most promising.…”