Reversible and Irreversible Deformation Mechanisms of Composite Graphite Electrodes in Lithium-Ion Batteries

Abstract

Repeated charge and discharge of graphite composite electrodes in lithium-ion batteries cause cyclic volumetric changes in the electrodes, which lead to electrode degradation and capacity fade. In this work, we measure in situ the electrochemically-induced deformation of graphite composite electrodes. The deformation is divided into a reversible component and an irreversible component. Reversible expansion/contraction of the composite electrodes is correlated with localized changes in graphite layer spacing associated with different graphite-lithium intercalation compounds. Phase transitions between different intercalation compounds are manifested during galvanostatic cycling as peaks in the derivative of capacity with respect to voltage; these peaks correspond remarkably well with peaks in the derivative of strain with respect to voltage. Irreversible electrode deformation is correlated with deposition of electrolyte decomposition products on graphite particles during the formation and growth of the solid electrolyte interphase (SEI). Both the irreversible capacity and the irreversible strain developed during galvanostatic cycling increase with increasing electrode surface area and increasing cycling time. During a potentiostatic voltage hold at 0.5 V vs Li +/0 , in which electrolyte decomposition is the dominating electrochemical reaction, both the capacity and the electrode strain increase proportional to the square root of time. Interestingly, the choice of polymer binder, either carboxymethyl cellulose (CMC) or polyvinylidene fluoride (PVdF), has a significant influence on the irreversible electrode deformation, suggesting that the formation and growth of the SEI layer is influenced by the polymer binder.

A Review of the Design of Advanced Binders for High‐Performance Batteries

“…The binder materials are used to be considered as an "inactive" component in the electrode; however, it has been widely recognized recently that the binder can play a significant role on the SEI formation on graphite electrode. [16][17][18][19][20] As for full cell, the capacity fade not only originates from cathode degradation but also stems from the SEI degradation on the graphite side. The SEI formation is critical for the graphite electrode; thick SEI film can significantly increase the resistance of the graphite electrode and result in fast capacity fade.…”

“…A similar observation was also made by Jones et al and they suggested the irreversible capacity is closely related to the electrode deformation and binder with high stiffness can constrain the electrode deformation and help to form a thin SEI layer. [20] Another aqueous binder material, polyacrylic acid (PAA), has also been widely investigated. The abundant carboxyl groups along the PAA chain can have strong interaction with graphite particles via hydrogen bonding.…”

Thermal and diffusion induced stresses in a structural battery under galvanostatic cycling

“…This assumption is made to simplify the analysis and is motivated by the fact that only small volume changes have been reported due to the continuous change of the SEI layer with repeated electrochemical cycling after the first charge/discharge cycles. For refined damage models, the accumulation of SEI formation-induced stresses should be accounted for in future studies [40]. In Fig.…”

A Dilatometric Study of Graphite Electrodes during Cycling with X-Ray Computed Tomography

“…29 Binders such as PVDF influence the tensile strength of electrodes and adhesion strength of the active material to the current collector. 30 This is particularly important in systems with electrodes that undergo large dimensional changes. Li et al investigated the effect of the binder on electrode strain in Li-sulfur battery electrodes using a similar experimental set-up.…”