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摘要
Simultaneous transport of an electrolyte and dissolved oxygen is analyzed with Newman's concentrated-solution theory to assess how nonuniform oxygen distributions might impact the voltages of metal/air batteries. For a solution comprising a neutral solvent, a simple salt, and oxygen, the Onsager-Stefan-Maxwell transport equations are inverted, yielding flux-explicit laws for oxygen, anion, and cation transport that distinguish the effects of individual diffusion and migration driving forces. Along with the ionic conductivity, electrolyte diffusivity, oxygen diffusivity, and cation transference number, a migration coefficient and a cross-diffusion coefficient are identified, which respectively account for the effects of electro-osmotic drag on oxygen and diffusional drag between salt and oxygen. A derived current/voltage relation reveals how oxygen gradients can in principle affect the cell potential; significant diffusion potential can arise from oxygen if it experiences electro-osmotic drag. Prior models are proven to follow from an assumption that cross-diffusion and electro-osmosis are both negligible, or, equivalently, that oxygen/ion interactions are weak. Experiments to quantify the novel transport properties are discussed, along with quantitative estimates of the cross diffusivity and migration ;coefficient.
- 出版日期2017
