Tortuosity of binder-free and carbon-free high energy density LiCoO2 electrodes for lithium-ion batteries
Conventional thin electrodes, by volume, contain a large amount of electrochemically inactive materials, which lowers the overall energy capacity of a cell, making it difficult to realize high volumetric energy with thin electrode architectures. Researchers have been actively pursuing methods which will enable the fabrication and full utilization of ultra-thick electrodes (< 200µm) in order to mitigate the amount of inactive material required in a cell. One approach which has emerged is to fabricate low tortuosity sintered electrode structures. This paper aims to correlate John Newman’s macro-homogeneous porous electrode model to thick high energy density carbon-free and binder-free sintered electrode samples fabricated at Palo Alto Research Center (PARC) and prior art studies on solid phase diffusion behavior and tortuosity in LiCoO2. Zhang et al. have shown that it is often difficult to correlate a macro-homogeneous electrode model across all C-rates. Often new model extensions are created to capture better correlation at slow and fast C-rates. This is more difficult when one is dealing with a new materials set. We examine how assumptions about tortuosity and diffusion effect model predictions across a range of C-rates. Our efforts focus on understanding the model parameters which can be used in Newman’s existing model without significant modification to the underlying equations.
C.L. Cobb and C.-J. Bae, Tortuosity of Binder-free and Carbon-free High Energy Density LiCoO2 Electrodes for Lithium-ion Batteries, ECS Transactions, 58(13), pp. 13-24, 2014.