Regular Biporous Model of Active Layer of the Lithium–Oxygen Battery Positive Electrode

Abstract

To perform the oxygen reduction reaction effectively, the active layer of the lithium–oxygen battery positive electrode must have developed surface possessing a complicated pore structure. During discharge (the oxygen reaction cathodic component), the electrode accumulates lithium peroxide, a final product of electrochemical and chemical reactions (resulting in the conjunction of lithium ions, oxygen molecules. and electrons); the latter undergoes oxidation (the oxygen reaction anodic component) during the lithium–oxygen battery charging. The lithium peroxide is a water-insoluble compound that has no electronic conduction; when depositing on the electrode surface it seals openings of narrow pores and prevents oxygen penetration therein. To obtain more lithium peroxide via oxygen reduction in the presence of lithium ions, a cluster of large pores, practically unsealed with the lithium peroxide, is produced in the active layer; the pores supply oxygen deep into the active layer. The Li2O2 accumulation occurs in a cluster of lesser pores with developed surface. In the creating of the lithium–oxygen battery positive electrode active layer optimal structure, the difficulty is that some key quantities are unknown in advance. They are the large-scale and lesser pore average size and their volume fractions in the active layer. To solve the problem, the regular biporous model of the pore structure can be used. In the model, the pore radii are strictly fixed. This opens a relatively easy way for the interconnecting, by calculations, of parameters and the lithium–oxygen battery dimensioning specifications during its discharge. This work aimed at the proposing of the positive electrode active layer regular biporous model and developing of a procedure for the calculating of the lithium–oxygen battery dimensioning specifications during the discharge. it is shown, in a specific context, how the varying of the positive electrode active layer structure and the oxygen consumption constant k can control the Li2O2 accumulation.