Solid oxide fuel cells are perspective electrochemical devices for hydrogen energy applications and require long time performance. The paper studies the influence of the processes of particles coarsening and cation interdiffusion on the degradation kinetics of the LSM-YSZ cathode material catalytic activity as related to the interaction processes with oxygen from the gas phase. The exchange kinetics with the gas phase oxygen was studied by the oxygen isotope exchange method with the gas phase equilibration at the temperature of 850 degrees C and Po-2 = 10(-2) atm. The samples were exposed for 1000 h. The coefficient of gas phase and surface oxygen exchange was found to decrease at the exposure. The paper discusses the physical reasons, which lead to the oxygen surface exchange coefficient decrease in LSM-YSZ electrodes and degradation of the polarization conductivity measured by electrochemical impedance spectroscopy. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.