In situ analysis of LiFePO 4 batteries: Signal extraction by multivariate analysis

The electrochemical reaction behavior of a commercial Li-ion battery (LiFePO 4 -based cathode, graphite-based anode) has been measured via in situ neutron diffraction. A multivariate analysis was successfully applied to the neutron diffraction data set facilitating in the determination of Li bearing phases participating in the electrochemical reaction in both the anode and cathode as a function of state-of-charge (SOC). The analysis resulted in quantified phase fraction values for LiFePO 4 and FePO 4 cathode compounds as well as the identification of staging behavior of Li 6 , Li 12 , Li 24 , and graphite phases in the anode. An additional Li-graphite phase has also been tentatively identified during electrochemical cycling as LiC 48 at conditions of ∼5% to 15% SOC.