Study On Preparation And Performance Of Microtubule Solid Oxide Fuel Cell Stacks By 3D Printing

Solid oxide fuel cell（SOFC）is widely used because of its wide range of fuel application,high power generation efficiency,environmental friendliness and other advantages.However,the complex preparation process and long preparation cycle of SOFC stack have always been an important factor restricting its commercialization process,and the connectors and seals of various materials during assembly are also easy to cause problems of stack operation stability and durability.The application of stereolithography（SLA）3D printing technology in the field of ceramics provides a way to simplify the assembly steps of the stack and improve its operation stability,and can effectively improve the transfer effect through the stack structure design to enhance the electrochemical performance.In this study,the SLA 3D printing technology is used to prepare the electrolyte support of the integrated microtubule SOFC stack,and then the anode and cathode are coated on the electrolyte.The stack is directly prepared without the assembly process,so as to achieve high-performance output.Specific research contents and results include:（1）Photocurable ceramic slurry with good rheological and light-curing properties are the basis for realizing SLA 3D printing,and the preparation of photosensitive resin premixes with low viscosity and high curing depth is the prerequisite for the successful preparation of photocurable ceramic slurry.In this paper,the effects of the type and content of resin monomer and the content of photoinitiator on the curing performance and viscosity of photosensitive resin premixes were investigated.The results showed that when the mass ratio of trimethylolpropane triacrylate（TMPTA）to 1,6-hexanediol diacrylate（HDDA）was 1.5:8.5 and the content of photoinitiator diphenyl（2,4,6-trimethylbenzoyl）phosphine oxide（TPO）was 1 wt%,the photosensitive resin premix had excellent curing performance and low viscosity of 2.1 m Pa·s.Based on the above optimized photosensitive resin premixes,8 mol%yttria doped zirconia（8YSZ）photocurable ceramic pastes were prepared and their rheological properties,stability and photocurability were investigated.The results showed that the solid content of the prepared 8YSZ photocurable slurry was as high as 50 vol%,and its viscosity was only2.48 Pa·s at 20^oC and 30 s^-1 shear rate,which was a typical shear thinning fluid.When the laser pulse width≥26%,the slurry curing depth can reach more than four times of the print layer thickness（≥100μm）,with good curing performance;After 180 days of sedimentation test,no obvious sedimentation phenomenon was found,and the slurry had excellent stability.The successful preparation of the photocurable slurry laid a good foundation for the preparation of microtubule SOFC electrolyte support.（2）Appropriate heat treatment process is a necessary condition for the preparation of dense SOFC electrolyte support.This paper optimized the heat treatment process,including one-step（sintering）and two-step（degreasing sintering）.At the same time,the effects of different sintering temperatures on electrolyte density,maximum fracture load and microstructure were investigated.The results showed that the electrolyte obtained by the two-step heat treatment process of degreasing in vacuum environment and sintering in air environment had high apparent precision,dense microstructure,and no lattice distortion and impurity phase during degreasing and sintering;1400 ^oC to 1550 ^oC could be applied to the sintering of 8YSZ electrolyte.The density of electrolyte under 1550 ^oC sintering is 99.89%.（3）The performance of solid oxide fuel cell is an important standard to reflect the quality of 3D printing electrolyte.In this part,firstly,the effects of different sintering temperatures on the electrode microstructure were investigated,and the conductivity and activation energy of Electrolytes Prepared by 3D printing and traditional dry pressing were compared.Then,the electrolyte supports prepared by 3D printing were assembled into microtubule SOFCs and their electrochemical properties were tested.Three channel honeycomb SOFCs and independent channel three tube SOFCs were prepared by multi-channel parallel in order to improve the battery output power.The results showed that the electrodes sintered at 1050°C were loose and porous and can be firmly attached to the electrolyte.8YSZ electrolytes prepared by 3D printing had a conductivity of 4×10^-2S·cm^-1 at 800°C,and their activation energy was calculated to be 0.87 e V,similar to that of 8YSZ electrolytes（0.95 e V）fabricated by the dry pressing method.The peak power density of single-tube SOFC at 850°C can reach 292 m W·cm^-2,and the power was 100m W.The peak power density of three channel honeycomb SOFC stack at 850°C was only 152 m W·cm^-2,the gas transmission outside the microtubule was blocked,and the mass transfer channel in the central area of the honeycomb was invalid.The peak power density of 3D printed independent channel three tube SOFC stack can reach 283m W·cm^-2 at 850°C,which was close to the power density of single tube SOFC.The power was 300 m W,which was three times the power of single tube SOFC.The electrochemical performance was multiplied with the increase of the number of tubes,indicating the possibility of SLA 3D printing technology in preparing microtubule SOFC stack with higher electrochemical performance,At the same time,it was proved that 3D printing technology can enhance the transfer effect and electrochemical performance of SOFC by optimizing the stack structure.