Out-of-Cell Oxygen Diffusivity Evaluation in Lithium-Air Batteries

The diffusion rate of oxygen has a significant impact on the power density, rate capacity, discharge capacity, and electrolyte stability of lithium-air batteries (H.-G. Jung, J.Hassoun, J.-B. Park, Y.-K. Sun, B. Scrosati, Nat. Chem. 2012, 4, 579- 85; J. Read, K. Mutolo, M. Ervin, W. Behl, J. Wolfenstine, A. Driedger, D. Foster, J. Electrochem. Soc. 2003, 150, A1351-A1356; Y. Cui, Z. Wen, X. Liang, Y. Lu, J. Jin, M. Wu, X. Wu, Energy Environ. Sci. 2012, 5, 7893-7897). Oxygen diffusivity in the solid porous cathodes of gas-based batteries is typically obtained by employing a few electrochemical models. In addition to the indirect computing characteristic, previous methods of evaluating oxygen diffusivity require multiple voltage-current experiments over intact lithium-air batteries, and can cause unnecessary costs resulting from the waste of materials from other battery components (J. Read, J. Electrochem. Soc. 2006, 153, A96-A100). In this report, through derivation and analytical design, a methodology is proposed for the direct out-of-cell oxygen diffusivity measurement in lithium-air batteries. The proposed electrochemical devices allow for efficient diffusivity measurements in porous solid cathodes, as well as subsequent quantitative pre-evaluation of important battery parameters including electrode porosity, thickness, and tortuosity. The proposed methodology is expected to facilitate the development of low-cost battery systems for a variety of applications, such as large capacity automobile batteries and electronics.