Statistical Analysis of Li-Oxygen Batteries

Abstract

In this article we develop a mathematical model and analyze the variability of discharge characteristics and impedance spectra in Li-air batteries with organic electrolyte. These batteries are well known to display a large variability of their characteristics from battery to battery (particularly of their specific capacity, energy and power densities), however, the exact reasons of this variability are still under investigation. Our model shows that the intrinsic variability of the pore microstructure which include the variability of the porosity and specific area from one macroscopic location to another macroscopic location inside the same battery and from one battery to another battery can be, at least in part, responsible for the large discrepancy of the results reported in the literature for the discharge characteristics and impedance spectra. It is shown that, while the variance of the specific capacity decreases slightly when the discharge current of the cell is increasing, the relative varianceto-mean ratio increases dramatically.

Stochasticity of Pores Interconnectivity in Li–O2 Batteries and its Impact on the Variations in Electrochemical Performance

“…On the modeling side, the common approach to study Li–O 2 batteries is to use continuum models and to capture the effects of pores interconnectivity via a tortuosity factor. The tortuosity is usually described via the Bruggeman relationship, which oversimplifies the role of pore sizes and connectivity on transport. − Recently, Mehta et al showed, for the first time, that the local variation of porosity and carbon surface area (CSA) in the cathode can lead to variations in performance as well . In their model, the positive electrode is discretized into fine meshes, and each mesh is assigned slightly different porosity and CSA values.…”

“…17−19 Recently, Mehta et al showed, for the first time, that the local variation of porosity and carbon surface area (CSA) in the cathode can lead to variations in performance as well. 20 In their model, the positive electrode is discretized into fine meshes, and each mesh is assigned slightly different porosity and CSA values. The porosity and CSA values are chosen based on the overall properties and standard deviations at the macroscopic level.…”

Unraveling the Li2S Deposition Process on a Polished Graphite Cathode for Enhancing Discharge Capacity of Lithium–Sulfur Batteries

“…The detailed description of the transport model and the boundary conditions at anode and cathode can be found in Supporting Information. The EIS spectra were computed using the technique presented in ref 35. We assumed a small-signal harmonic perturbation of the discharge current i ̃ejωt where i ̃is the complex magnitude and ω is the angular frequency of the signal and computed the small-signal response of the cell voltage, vẽ jωt , numerically.…”