In order to probe Li content, cation distribution and defects in a series of LiFe1-xMnxPO4 nanoparticles, we propose the use of neutron powder diffraction and pair distribution function analysis using the Polaris beamline. The electrochemical performance of such insertion electrodes is heavily influenced by such parameters and the studies we will carry out here will complement our previous X-ray diffraction, muon spectroscopy and X-ray absorption spectroscopy measurements. This will afford a complete structural analysis of these important materials, allowing us to probe the mechanisms underpinning their electrochemical behaviour.