Abstract

A macro-homogeneous model has been developed to evaluate the impact of replacing pure oxygen with ambient air on the performance of a rechargeable non-aqueous Li-air battery. The model exhibits a significant reduction in discharge capacity, e.g. from 1240 to 226 mAh gcarbon−1 at 0.05 mA cm−2 when using ambient air rather than pure oxygen. The model correlates the relationship between the performance and electrolyte decomposition and formation of discharge products (such as Li2O2 and Li2CO3) under ambient air conditions. The model predicts a great benefit of using an oxygen-selective membrane on increasing capacity. The results indicate a good agreement between the experimental data and the model.

Highlights

  • Several times higher specific energy than Li-ion batteries makes the rechargeable Li-air a candidate of new generation of energy storage devices [1e4]

  • Oxygen is reduced at the active surface with Liþ, leading to the desired discharge products of Li2O2 and the by-product of Li2CO3 or lithium alkyl carbonates resulting from the electrolyte decomposition [12,13,19]

  • As the Li-air battery system is complex with the various reactions and mass transport species along the entire cell, the buildup of Li2O2 and Li2CO3, and the change of porosity and interfacial surface area vary with time and space, several model assumptions were adopted to support the calculation as follow: C2O26À þ 4Liþ þ 2OÀ2 /2Li2CO3 þ 2O2 (1c)

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Summary

Introduction

Several times higher specific energy than Li-ion batteries makes the rechargeable Li-air a candidate of new generation of energy storage devices [1e4]. There is a small volume of published works demonstrating the behaviour of Li-air battery with air feeding [11,16,17,21] These studies solved the contaminated gases problems by using an oxygen-selective water barrier membrane covering the outer surface of the cathode to prevent moisture and permeate oxygen into the porous cathode at the same time. Mathematical model for Li-air battery with air feeding condition can be used to identify cell-limiting mechanisms and reduce the time-consuming work compared to experiment aspect It avoids the serious safety problems that could happen when the ingress of moisture reacts with lithium metal anode. This model can be used to describe the behaviour of Li-air batteries in ambient air condition as well as to optimise the performance and structure of these battery electrodes

Theoretical mechanism analysis
Effect of using ambient air condition
Electrolyte degradation
Solvent degradation
Model description and assumptions
Governing equations
Rate expression at cathode
Rate expression at anode
Specific surface area and porosity change
Results and discussion
Initial conditions
Boundary conditions
Li-air performance with air feeding
Comparing the Li-air model with experiment using air feeding
Li-air performance combining the electrolyte degradation effect
Membrane with high oxygen permeability
Conclusions
Full Text
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