Thermal Structural Behavior of Electrodes in Li-Ion Battery Studied In Operando

Abstract

© 2018 The Electrochemical Society. Structural response of Li-ion battery electrodes was studied under ex situ conditions using the electrode powders or extracted electrode sheets and in situ conditions using cylindrical Li-ion batteries of 18650-type in charged and discharged states by high-resolution neutron powder diffraction. Structural studies were performed in a broad temperature range 4–360 K covering the usual one relevant for the operation of typical Li-ion cells. Lattice parameters and thermal expansion coefficients, atomic coordinates, interatomic distances and lithium concentrations were independently determined using the Rietveld refinement technique. Besides the lattice softening observed upon delithiation of LiCoO2an anomalous structural behavior of stage II in lithiated graphite was noticed. A comparison of the experimental results for stage II collected in both ex situ and in situ modes indicated certain differences, which may be attributed to a temperature-driven development of non-equilibrium states in a Li-ion battery upon heating.