2, Sandia National Laboratories, Livermore, California, United States
3, Stanford University, Stanford, California, United States
The insertion of lithium ions into solid host structures is the key mechanism for energy storage in lithium ion batteries and has recently been demonstrated as a means to dynamically tune material properties for solid-state switching devices. In situ investigations of lithium insertion processes are complicated by the air-sensitivity of the lithium-containing electrodes and electrolytes. The quantification of the lithium fraction in a certain host particle using electrochemical methods is further complicated by unequal lithiation kinetics in different host particles and side reaction currents originated at current collector-electrolyte interfaces.
Here, we present an experimental platform for the quantitative investigation of lithium insertion into a single-particle host structure, enabling the use of in situ time-resolved x-ray and optical techniques, combined with electrochemical analysis. Using a single flake of MoS2 as a model host system we demonstrate in situ measurements of the structural evolution, optical properties, thermal properties and the layer-to-layer binding as a function of lithium fraction by means of ultrafast x-ray and optical techniques. Our picosecond time-scale optical pump x-ray diffraction probe experiments define a new method for directly probing cross-plane and interfacial phonon transport as a function of the concentration of an intercalated species.