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Synthesis And Properties Of NiO-doped SmBaCo2O5+?-based Cathode Material

Posted on:2017-10-22Degree:MasterType:Thesis
Country:ChinaCandidate:L N XiaFull Text:PDF
GTID:2321330512475775Subject:Materials Processing Engineering
Abstract/Summary:PDF Full Text Request
Solid oxide fuel cell(SOFC)is a power generation device that converts chemical directly into electrical energy with high energy conversion efficiency,convenience and environment friendly.As one of the core components,cathode materials determine the whole performance of SOFC.The doule pervoskite material SmBaCo2O5+?(SBCO)as a mixed ionic-electronic conductor,has high electrical conductivity,oxygen diffusion and interfacial exchange,which is considered as a promising candidate for intermediate-temperature solid oxide fuel cell(IT-SOFC)cathode.In order to lower the thermal expansion coefficient(TEC)of SBCO,a proper amount of Ni was used to replace Co,and the electrolyte SDC was introduced into cathode to form composite cathodes.Moreover,the effects of Ni and SDC dopping in the cathode materials and different preparation methods were investigated in this paper.The effects of Ni dopping on the Co sites in SmBaCo2-xNixO5+?(SBCNx)and the Ni content on SBCN were studied.The results showed the electrical conductivities of SBCNx decreased as the Ni content increased,and the electrial conductivity of SBCO was 1091 S·cm-1 at 250 ?.The TEC had a decreased trend with Ni content increasing from 19.96×10-6 K-1 for SBCO to 16.26×10-6 K-1 for SBCN0.5,while the TEC of SBCN0.3 reached a minimum of 15.59×10-6 K-1.With the increase of Ni dopping,the polarization resistance(Rp)of SBCNx had an increased trend but the output power density of single cell decreased.Among them,SBCN0.3 exhibited a combination of low thermal expansion(15.59x10-6 K-1),a reasonably low Rp value(0.0464 ?·cm2 at 800 0C)and high powerdensity(536 mW·cm-2 at 800 0C).In order to study the effects of different preparation methods on the properties of cathode materials,SBCN0.3 was synthesized by an EDTA-glycine process(EGP)and solid state reaction(SSR).The results indicated that SBCN0.3 was synthesized by EGP had a good double perovskite structure after calcining at 900 ? for 5 h,and the resulting powders had fine grain sizes and uniform distribution.TEC of the SBCN sample was 15.59×10-6 K-1 between 25 ? and 800 ? in air,which was much smaller than that of solid state reaction(SSR)for 19.05×10-6 K-1.The electrical conductivity of the SBCN reached 471 to 256 S-cm-1 from 500 to 800 ?,which was higher than that of SSR.A symmetrical half cell with cathode power prepared by EGP had better morphologyies fine particles,uniform distrubution,and good gas connection and three-phase interface.Thus,its electrochemical performance was better than that of SSR.To further reduce TEC of cathode materials,electrolyte was introduced into SBCN0.3 cathode to form composite cathode SBCN0.3-xSDC.The results showed that the TEC and the electrical conductivity decrease with an increase in the SDC content of SBCN-xSDC composite cathodes.The Rp reduced first and then increased.When the content of SDC was 20 wt%,the Rp value reached the minimum 0.0272?·cm2 at 800 ? and the single cell Ni-SDC/SDC/SBCN0.3-20SDC obtained a maximum power density of 628 mW·cm-2 at 800 ?.
Keywords/Search Tags:solid oxide fuel cell, electrochemical performance, thermal expansion, SmBaCo2O5+?, double perovskite
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