LiFePO4 (LFP) is a commercially used Li ion battery material for high power applications. Particle shape and surface play an important role in the Li diffusion and thus the electrochemical performance of the material. Additionally, the change of lithium content during cycling can affect the Li ion dynamics in the material. After the successful experiment addressing the particle shape, we propose to measure the phonon density of states of LFP as a function of surface coatings at different levels of lithium content. For this, we kindly request six days of beam time at MARI. This will give us further insights on how surface phonon modes play a role in the size-dependent behavior of the lithium ion diffusion in LFP.