Characteristic analysis of lithium–oxygen batteries considering the discontinuous deposit and electrolyte degradation effects during discharge

The modeling research plays a crucial role in grasping the reaction mechanisms and forecasting the performance of lithium‑oxygen (Li[sbnd]O₂) batteries. A transient Li[sbnd]O₂ battery model including continuity, transportation, and reaction kinetics by simultaneously considering the discontinuous deposit of discharge product Li₂O₂ and the formation of by-product Li₂CO₃ due to electrolyte degradation, is developed to reveal the discharge phenomena. The effects of operating conditions and electrolyte and electrode properties on the discharge behaviors including voltage-capacity curve, energy density, profiles of O₂ concentration (C_O2) and porosity (ɛ) at the cathode are quantitatively studied. It is found that enhancing O₂ solubility (S_O2) and diffusivity (D_O2) significantly improves discharge capacity and voltage plateau; the promotion of voltage plateau will be inconspicuous as electrolyte conductivity (κ) is enlarged over 1 S/m. With the rise of ɛ from 0.73 to 0.93, the specific capacity is boosted from 874 to 6122 mAh/g_‑carbon, and the corresponding specific energy upgrades from 2260 to 15,610 mWh/g_‑carbon. Shortening cathode thickness (L_ca) facilitates the efficient utilization of carbon cathode material but this comes at the expense of lowering the mass loading of carbon, the practical energy drops 59.4 % as L_ca reduces from 750 μm to 100 μm. After 20 consecutive charge-discharge cycles, the capacity retention obtained is 36.884 %, accompanied by a 13.8 % volume fraction of Li₂CO₃ formation inside the cathode. This work may guide in designing electrodes and electrolytes and provide performance regulation strategies for Li[sbnd]O₂ batteries.