PHYSICAL PROPERTY CHANGE OF FEOOH(AD)(1 4) DURING LITHIUM INSERTION AND EXTRACTION/

The physical state changes of amorphous FeOOH incorporating aniline de rivatives [FeOOH(AD)(1/4)] in the course of discharge and charge cycli ng were studied using electron spin resonance (ESR). Two peaks were ob served for the ESR signal of FeOOH(AD)(1/4), which were related to the radicals in the aniline derivative and electron spin of the iron ions . The electron spin concentrations corresponding to these peaks were e stimated from the ESR signals. In the first discharge and charge cycle , the electron spin concentration for iron ions changed irreversibly. However, the change in the electron spin concentration for iron ions w as reversible for the second and subsequent discharge and charge cycle s. These findings clearly show that the irreversible physical property changes for FeOOH(AD)(1/4) take place during the first discharge. The electron spin concentration for the aniline derivatives also changed with the oxidation or reduction of iron ions in FeOOH(AD)(1/4). This r esult suggests the presence of an electronic interaction between anili ne derivatives and iron ions in FeOOH(AD)(1/4).