In-situ investigation of the water absorption/desorption behavior of LiFePO4

We utilize high-sensitive in-situ thermogravimetric measurements under controlled relative humidity levels to elucidate in detail the water absorption/desorption characteristics of the positive electrode material LiFePO4. Both plain (with carbon-coating only) and composite–electrode powder samples are investigated. It is revealed that not only the amount of absorbed water but also the speed of absorption depend on the humidity level of the surrounding atmosphere. The additives used for manufacturing the LiFePO4 composite electrode protect the material to some extent against the water absorption. Partial substitution of iron by manganese increases the amount of absorbed water but at the same time improves the reversibility of the water absorption/desorption process.