Kinetics of Initial Lithiation of Crystalline Silicon Electrodes of Lithium-ion Batteries
Matt Pharr (Harvard University), Zhigang Suo (Harvard University), Kejie Zhao (MIT), Joost Vlassak (Harvard University)
Lithium ion batteries: When Chemistry meets Mechanics
Mon 4:20 - 5:40
Salomon 003
Electrochemical experiments have been conducted on {100}, {110}, and {111} silicon wafers to characterize the kinetics of the initial lithiation of crystalline Si electrodes. Under constant current conditions, we have observed constant cell potentials for all orientations, indicating the existence of a phase boundary that separates crystalline silicon from the amorphous lithiated phase. For a given potential, the velocity of this boundary was found to be faster for {110} silicon than for the other two orientations. From mechanical modeling, we have found that these measurements of varying phase boundary velocities can accurately account for anisotropic morphologies and fracture developed in crystalline silicon nanopillars. I will also present a kinetic model by considering the redox reaction at the electrolyte/lithiated silicon interface, diffusion of lithium through the lithiated phase, and the chemical reaction at the lithiated silicon/crystalline silicon interface. From this model, the rates of the reactions at the interfaces can be quantified and a lower bound on the diffusivity through the lithiated silicon phase can be estimated. Other recent experimental results will also be discussed.