Real time stress measurements on composite lithium-battery electrodes
Vijay Sethuraman (Brown University), Nathan Van Winkle (Brown University), Annam Nguyen (Brown University), Siva Nadimpalli (Brown University), Michael Chon (Brown University), Hailong Wang (Brown University), Daniel Abraham (Argonne National Laboratory), Allan Bower (Brown University), Vivek Shenoy (The University of Pennsylvania), Pradeep Guduru (Brown University)
Lithium ion batteries: When Chemistry meets Mechanics
Tue 9:00 - 10:30
Salomon 003
Real-time stress measurements made during electrochemical cycling of composite lithium-battery electrodes will be presented. Composite electrodes are porous in nature and are made of an active lithium-intercalation material mixed with a polymeric binder and a conductive additive. During electrochemical intercalation of an electrode made with graphite particles, the compressive stress increases with the electrode’s state-of-charge, reaching a maximum value of 10 – 12 MPa. De-intercalation at a slow rate results in a similar linear decrease in electrode stress. Tensile stress of a few MPa develops at the end of deintercalation in the first few cycles, after which the electrode remains under compressive stress only. During galvanostatic lithiation, the stress in a composite Si electrode made with a carboxymethyl cellulose binder becomes compressive and increases to 70 MPa, where it reaches a plateau and increases slowly thereafter with capacity. Polyvinylidene-binder based composite Si electrode exhibits similar behavior, although with lower peak compressive stress of about 12 MPa. These experiments indicate that the stress evolution in a Si composite electrode depends strongly on the mechanical properties of the binder. During delithiation of a composite electrode made with Li1.2Ni0.15Mn0.55Co0.1O2 active material, the biaxial stress becomes tensile and increases to 1 MPa fairly quickly (when the state of charge is 15%) and decreases gradually thereafter (when the state of charge is 90%). The stress falls rapidly thereafter a state of zero stress. Upon lithiation, the stress becomes compressive and continues to increase to a maximum of 7 MPa. This behavior repeats during subsequent delithiation/lithiation cycles albeit with a lower peak tensile and peak compressive stresses, possibly due to mechanical damage on the electrode.