DISCHARGE OF LITHIUM-OXYGEN POWER SOURCE: MONOPOROUS CATHODE THEORY AND ROLE OF CONSTANT OF OXYGEN CONSUMPTION PROCESS

The paper deals with a characteristic feature of the discharge process of the cathode of a lithium-oxygen current source (LOCS) with the electrolyte based of a nonaqueous solvent, which is the clogging the positive electrode pores with the insoluble electrolyte and nonconductive reaction product, lithium peroxide Li₂O₂. Lithium peroxide is formed in a multistage complex reaction occurring in the course of oxygen reduction. In the reverse process, i.e., anodic LOCS charging, lithium peroxide accumulated in the course of discharge is decomposed with formation of lithium ions, oxygen molecules, and electrons. It is advisable to obtained as much as possible lithium peroxide during the LOCS discharge. However, it “clogs” the cathode pores, prevents the flow of oxygen into them, that, in turn, complicates the further lithium peroxide accumulation.  Thus, the calculations show that the cathode discharge process can be mainly carried out only in a relatively thin porous layer bordering on the gas phase. Therefore, in the absence of special measures, the capacity calculated per square centimeter of the outer cathode surface is small. Usually, when the functioning of the active cathode layer is studied, a certain value is assumed for the oxygen consumption that is the main constant of the LOCS charging process (its value is characterized by parameter k). This paper uses computer simulation with variation of k in a wide range. The corresponding variation of the overall characteristics of the LOSC cathode is demonstrated. The causes of the changes in the cathode pores are explained. The study shows that a decrease in constant k (which lead to a decrease in consumption of oxygen intended for formation of Li₂O₂) and an increase in the pore radius (at a transition from micropores to mesopores) result in an increase in the specific cathode capacitance and the amount of lithium peroxide accumulated in the cathode and not in their decrease.

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