Synthesis And Performance Research Of LSM-BSCF Composite Cathode For IT-SOFC

With the rapid development of international industrial level and human living standards,the total energy for industrial production and human life increase extremely and the traditional energy could not meet the total requirements,besides,the traditional energy has lots of disadvantage such as low energy efficiency and high environmental pollution,therefore,the development of new energy has become an important international energy research direction,Solid oxide fuel cell is a high efficient electrochemical device that can directly transform the energy released by the chemical reaction to the electrical energy with the advantages such as wide ranges of fuel sources,low noise and zero emission,it has brilliant application prospect in the 21^st when the fossil energy will be gradually depleted.However,the conventional high-temperature SOFCs are difficult to commercialize due to the long-term performance decay problems and high manufacturing and operating costs,so,it is necessary to reduce the operating temperature to 600-800°C,the stability of the electrode materials has been greatly improved at intermediate temperature,but the catalytic of electrode will be greatly abated with the reduce of operating temperature,so the research of the cathode with good electrocatalytic activity and long-term stability at intermediate temperature has become the hotspot.BSCF is one of the common perovskite cathode materials with wonderful ionic and electronic conductivity,outstanding electrochemical properties at intermediate temperature,BSCF shows the perfect performance in the chemical and thermal compatible with the common electrolyte material GDC,however,BSCF is easily reacted with CO₂ producing the impurity of barium and strontium carbonate,resulting the performance of BSCF cathode tailing off,Sr-doped LaMnO₃?LSM?with high electrochemical activity,electronic conductivity is a relatively mature material widely used in SOFCs operated at high temperatures,but it could not be used in IT-SOFCs for the extremely low ionic conductivity,therefore we could combine the advantages of two materials using solid-solution method,we can coat the LSM particles on the surface of BSCF particles to avoid the reaction between BSCF particles and CO₂,besides,LSM materials could offset the drawback of BSCF with low ionic conductivity.BSCF powders was added into LSM solution to prepare the LSM-BSCF composite powders,we research the CO₂ resistivity of LSM-BSCF with different mass ratio,we prepare the BSCF cathode and LSM-BSCF cathode by screen printing and research the electrochemical performance of cathode.In this article,we use the sol-gel method to synthesize the BSCF powders,the powders were indicated with pure perovskite structure after calcined at 900^oC for two hours according the result of the X-ray diffraction,the BSCF powders tended to react with CO₂ producing barium and strontium carbonate.BSCF cathode show the extremely low polarization resistance at operating temperature,the polarization resistance of BSCF cathode was 0.72,0.25,0.09 and 0.046?cm² respectively at 600 ^oC,650 ^oC,700 ^oC,750oC.In this article,we use the solid-solution method to prepare the LSM-BSCF composite powders with different mass ratio,the CO₂ resistivity of all LSM-BSCF composite powders was tested,the result showed that the LSM-BSCF composite powders with mass ratio of 1:30 has the good CO₂ resistivity,LSM particles were well grow at the surface of BSCF particles according the result of scanning electron microscope and element mapping,the polarization resistance of LSM-BSCF cathode was 7.4,2.1,0.35 and 0.1?cm² respect at 600 ^oC,650 ^oC,700 ^oC,750 ^oC,which was much larger than BSCF cathode,the LSM shell thickness is too thick when BSCF particles can be achieved to prevent the reaction with CO₂,the oxygen ion is hardly to pass through the LSM shell,so the three phase reaction interface of LSM-BSCF was much smaller than BSCF cathode after BSCF particles were fully coated by LSM particle without ionic conductivity in intermediate temperature.