This NURP project leads to fundamental knowledge about degradation of electrodes that is necessary to develop long cyclic life (i.e., durable) and high energy density batteries, which are crucial for weight sensitive applications such as unmanned underwater and aerial vehicles and weapons systems used in US Navy.Abstract: Despite the rapid advances in Li-ion battery technology in recent years, the performance (e.g., energy density and durability) of batteries is still not adequate to meet the growing energy demands. Lithium-ion battery electrodes are porous composites consisting of active particles (that are responsible for energy storage) held together by a polymer binder. This binder forms bridgesbetween active particles to provide electrical network that connects all the particles to a current collector; this network is necessary to sustain chemical reactions throughout composite electrode. Mechanical failure of the binder bridges will electrically isolate active particles contributing to capacity fade. Hence, binder-particle interaction plays a critical role in determining the cyclicbehavior of the electrodes. In spite of this, the understanding of the particle-scale mechanics andthe mechanisms that determine the cyclic life of batteries is missing. In addition, studies on the effect of binder on the passive layer (or solid electrolyte interphase, SEI) formation is almost nonexistent in the literature. Hence, we propose a series of experimental and theoretical tasks with the following two primary objectives: (i) to carry out in situ and ex situ measurements of stress and deformation at the particle level in ideal electrode geometries to elucidate the degradation mechanisms and the conditions that trigger these mechanisms (e.g., stress and deformation levels,state of charge, number of cycles, particles distribution); and (ii) understand the effect of binder on the nature, properties, formation mechanism and location of SEI formation in a composite electrode by carrying out X-ray photoelectron spectroscopy (XPS) analysis.We will consider two polymers: polyvinylidene fluoride (PVdF) and carboxymethylcellulose (CMC) as binders; and two high energy density materials: Si and Ge as the active materials to achieve the above objectives. Specific tasks that will be carried out towards the project objectives include: (1) fabricating a composite electrode with regularly spaced micro-pillar particles connected with binder to enable stress and deformation measurements at the particle level. The stresses in these binder-particle geometry will be measured in real-time (i.e., while charging/discharging) using a substrate curvature method; and (2) carrying out XPS and SEManalysis on binder coated Si and Ge electrodes that are lithiated under various electrochemical conditions to probe the effect of binder on SEI formation. The successful execution of this project leads to fundamental knowledge about degradation of electrodes that is necessary to develop long cyclic life (i.e., durable) and high energy density batteries, which are crucial for weight sensitive applications such as unmanned underwater and aerial vehicles and weapons systems used in US Navy.
|Effective start/end date||2/27/17 → …|
- U.S. Navy: $37,946.00