An investigation of intercalation-induced stresses generated during lithium transport through sol–gel derived Li xMn 2O 4 film electrode using a laser beam deflection method

Abstract

The stress changes Δ σ generated during lithium transport through the sol–gel derived Li x Mn 2O 4 film electrodes annealed at 773 and 873 K were quantitatively determined as a function of the lithium stoichiometry x using a laser beam deflection method (LBDM). Δ σ generated during a real potential step between an initial electrode potential and a final applied potential was uniquely specified by the Δ σ versus x curve. The Li x Mn 2O 4 film annealed at 773 K for 24 h (low temperature (LT)-Li x Mn 2O 4) showed larger capacity than the Li x Mn 2O 4 film annealed at 873 K for 6 h (high temperature (HT)-Li x Mn 2O 4) and this result is ascribed to the fact that the smaller the grain size is, the more increases the electrochemically active area of the film electrode. From the analysis of the normalised Δ σ transient measured simultaneously along with the cyclic voltammogram in the potential range of 2.5–3.4 V Li / L i + , it is found that normalised Δ σ generated in the LT-Li x Mn 2O 4 was smaller than that in the HT-Li x Mn 2O 4 during the lithium intercalation/de-intercalation around 3.0 V Li / L i + region. This result gives an experimental evidence for the fact that the Jahn–Teller distortion is suppressed by the increase in the average oxidation state of manganese with decreasing in annealing temperature.