Impurities in LiFePO[sub 4] and Their Influence on Material Characteristics

impurity was found in hydrothermally grown samples made with excess Li. The impurity dissociates in water, leading to an apparent alkaline nature of the sample. The impurity can be removed by washing the sample in a neutral buffer solution, after which an increase in specific capacity of the sample was observed. , as an inactive component within the active material, reduces the energy density of . Additional experiments were performed to study the reactivity of in different environments. It is found that decomposes in a strong alkaline solution and the decomposition can be slowed down by carbon coating the material. After prolonged storage in water, the specific capacity of carbon-coated is reduced and Fe dissolution is observed. Material degradation is thought to be due to interactions among , impurities, and water.