This proposal seeks to test a new battery designed to allow in situ neutron diffraction measurements of lithium ion battery electrodes under charge and discharge. We have developed a new wound cell which contains large amounts of electrode material necessary for high quality diffraction data but arranges them in thin electrodes which will allow fast electrochemistry. All hydrogen containing components have been replaced with hydrogen free alternatives to avoid significant amounts of incoherent scattering.This cell will be used to investigate the structural changes in LiFePO4 at a series of rates. The reduced diffraction pattern collection times afforded by the upgraded Polaris instrument will allow study of high rates of charge and discharge. The cell will then be used to study the slow cycling structural changes occurring in LiFeSiO4 at 55 C during the first charge and discharge.