An analytical model is proposed to investigate properties of composite electrodes that utilize more than one active material. We demonstrate how the equations can be applied to aid in the design of electrodes by comparing silicon-graphite and tin-graphite composite negative electrodes as examples with practical relevance. Based on simple assumptions, the results show how volume expansion tolerance and initial porosity are important factors for the achievable gravimetric and volumetric capacities as well as volumetric energy density. A Si-alloy/graphite composite electrode is used as an experimental system to corroborate the formulated analysis. Kinetic limitations are also addressed based on a novel heuristic approach.

Li and C 1s core-electron excitation spectra of electrochemically prepared stage-II and stage-I lithiated graphite were investigated by means of inelastic X-ray scattering spectroscopy. The near-edge structure is discussed, and the spectral features are interpreted using ab initio calculations. Our results confirm the invariance of the excitation threshold for transitions from C 1s core-states to empty ${\pi }^{*}$ states upon Li intercalation for stage-I and show this invariance also occurs for the second stage of intercalation. A systematic shift of the ${\sigma }^{*}$ excitation threshold to lower energies with the Li content was observed. The Li core spectra reveal an ionic character of the intercalated Li in stage-I and in stage-II. The present results provide further valuable information for forthcoming in situ studies of lithiation/delithiation processes in graphite anodes by inelastic X-ray scattering spectroscopy.