Rapid, Non-Invasive Method for Quantifying Particle Orientation Distributions in Graphite Anodes

Abstract

For materials with 1D or 2D lithiation pathways and non-spherical particle shapes, knowledge of the crystallographic grain orientation in the particle and the active particle orientation in the porous electrode is important for quantifying battery performance. Here we study graphite anodes and show how X-ray diffraction based texture measurements can be used to quantify both the particle orientation, which develops during the coating and calendaring process, and the grain orientation within a specific type of graphite. This lab-based, non-invasive approach to study electrode structure and active particles can assist in engineering improved lithium ion batteries. © The Author(s) 2017. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. [DOI: 10.1149/2.1291712jes] All rights reserved.Manuscript submitted June 23, 2017; revised manuscript received August 14, 2017. Published September 8, 2017 In order to optimize a lithium ion battery, it is important to understand the lithiation pathways within the active material 1-5 as well as the lithium transport through the pore space of the electrode, which is governed by the shape and orientation distribution of particles in the electrode.6,7 Here, we present X-ray diffraction (XRD)-based texture measurements as a quantitative, non-invasive method to characterize the crystallographic grain orientation of particles and the orientation of these particles within lithium ion battery porous electrodes.The importance of this structural information is highlighted in the case of graphite, which is the most widely used active material for negative lithium ion battery electrodes. The two-dimensional structure of graphite is responsible for the anisotropy of its electronic, ionic, and thermal conductivity as well as its mechanical properties. 8(De)lithiation occurs along the (002) planes, causing directional volumetric expansion in the [001] direction, which can also translate to directional changes in electrode porosity as the graphite particles swell into the pore space during lithiation. 9 The two-dimensional nature of graphite is also reflected in the shape of graphite particles: they are naturally platelet-shaped. 10 Earlier work has shown that non-spherical particles align during porous electrode fabrication, leading to large tortuosity of the pore-phase, reducing effective transport of lithium in the electrolyte.6 Tortuosity can be somewhat reduced by using spherical graphites, which often exhibit complex grain distributions depending on the manufacturing process. 10For graphite anodes, the electronic and ionic conductivity of the graphite particles does not limit cell performance, 11,12 so most efforts have focused on quantifying and reducing tortuosity, which limits the fast charging of high energy dense cells. 13,14 To determine tortuosity of an e...

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“…Newman and team [15,[17][18][19] proposed a porous electrode model using a concentrated solution framework. Baade et al [20] described the quantification procedure for particle orientation in porous graphite electrodes. Hosseinzadeh et al [21] studied the effect of customized porosity and noted lesser heat generation than uniform porosity.…”

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“…Wood and Ebner 22 studied electrode formation with the magnetic field, which was further verified by Billaud et al 23 They noted a significant increment in specific capacity for the newly aligned electrode. Baade et al 24 experimented and quantified the results of particle distribution, porosity, and orientation using X-ray diffraction. Peterson and Wheeler 25 noted the electrode's electronic conductivity and its interdependence with porosity, pressure, carbon fraction, and electrolyte presence.…”