Out‐of‐Cell Oxygen Diffusivity Evaluation in Lithium–Air Batteries

Abstract

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. 2012,5,[7893][7894][7895][7896][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 lowcost battery systems for a variety of applications, such as largecapacity automobile batteries and electronics.-With a high energy density and simple operation, the lithiumair battery has evolved to be an exceptionally promising candidate for mitigating the increasing unsustainability from the aggravated consumption of fossil resources. [1][2][3] Despite tremendous interest drawn to the lithium-air battery, it still suffers from a number of issues associated with the performance of its electrolyte and electrode materials. [2,4] High-performance electrolyte/electrode materials not only provide large energy densities, but also endure a number of operation cycles. Both aspects largely rely on efficient mass transport, that is, lithiumion conduction and oxygen diffusion in the operation of the lithium-air battery. [5,6] Unlike electrode-supported solid-oxide fuel cells, the maximum attainable current density is limited by polarization losses at the electrodes; in the case of bulk lithium-air batteries, the Li-ion diffusion coefficient in the electrolyte is lower than the fuel gas diffusion at the cathode. However, for lithium-air batteries with nanostructured cathodes, the cathode gas diffusion is governed by Knudsen diffusion, and thus the total mass transport associated with the batteries can be limited by cathode gas diffusion. Conductivity of lithium ions has been measured through electrochemical impedance spectroscopy and the galvanostatic intermittent titration technique, among others. [7,8] Except for indirect methods through computations based on multiple voltage-current measurements, an efficient methodology for the direct measurement of oxygen diffusivity in lithium-air batteries is still lacking. In this report, we show that direct oxygen diffusivity measurements can be realized by using a series of electrochemical devices, upon analytical derivation based on c...

Interfacial lattice-strain effects on improving the overall performance of micro-solid oxide fuel cells

“…As the operating temperatures are decreased directly to the low states, the ionic conductivity in electrolyte and the surface oxygen exchange rate at cathode will become sluggish. [36][37][38] Currently, with the development of thin film technology, more attention has been turned to fabricating the nanoscale heterostructures using existing conventional materials because of the discovery of the interfacial strain effects in the nanoscale heterostructures on improving overall performance, including facilitating the ionic migration, the oxygen vacancy formation, and the oxygen molecule adsorption. [24][25][26][27][28][29][30] In the past decades, major efforts were focused on the search for novel electrolyte/electrode materials with enhanced the ionic conductivity and oxygen surface exchange kinetics, or modifying the microstructure of the materials.…”

Comment on “Out‐of‐Cell Oxygen Diffusivity Evaluation in Lithium–Air Batteries” by He et al.

“…The electrochemical device described by He et al . is illustrated in Figure , which is identical to that shown in Figure 1 a of that article.…”

“…Recently, He et al . reported an out‐of‐cell oxygen diffusivity evaluation of the porous cathode of Li–air batteries (LABs).…”

“…The setup of Figure is proposed for determining the oxygen diffusivity of LAB cathodes based on the assumption that “the Knudsen diffusivity of the cathode is smaller than the oxygen diffusivity in the electrolyte” …”

Gas transport evaluation in lithium–air batteries with micro/nano-structured cathodes

“…The correlation between the parameters associated with a bulk cathode and the performance of the lithiumeair battery has been investigated recently by the authors [28]. However, there has been rare theoretical investigation into the gas transport properties of nano-sized cathodes.…”