Preparation And High Temperature Performance Of Cr₃C₂ Coating On The Surface Of Sodium Sulfur Battery Current Collector

Sodium-sulfur batteries have the advantages of high energy density,high power density,low self-discharge rate,wide application fields,and low raw material costs.It has good prospects as an energy storage power station and special power source.However,the abnormal attenuation of sodium-sulfur battery capacity is currently a very common problem,which limits its large-scale application.The main reason for this problem is the corrosion of the sodium-sulfur battery current collector.Since sodium-sulfur batteries usually operate at 350?,the high-temperature corrosion resistance of the metal current collector must be improved to solve this problem.In this thesis,Cr₃C₂ coating was deposited on the surface of SS304 stainless steel by surface modification.The effect of reactive and non-reactive magnetron sputtering deposition process parameters on the microstructure and corrosion performance of the coating was studied.The following results have been achieved:We have sputtered Cr₃C₂ coating on SS304 stainless steel surface at different temperatures(100?,200?,350?,500?)using non-reactive magnetron sputtering technology.And we found that when the temperature was 500?,the coating structure was denser,the grains were more refined and the crystallinity was better.When the target power was changed,it was found that when the target power is 160w,more atoms of Cr and C elements were sputtered on the substrate.Argon gas flow rate and working pressure have little effect on the coating.The surface of the Cr₃C₂ coating prepared with a single Cr₃C₂ compound target is dense,the content ratio of Cr and C is 28:44,and the coating components are mainly Cr₃C₂ and Cr7C3.XPS analysis showed that the amorphous carbon(sp3)content in the coating was relatively low,indicating that the surface stress was small and the coating was relatively stable.It was found that after being corroded in molten sodium polysulfide at 350? for 180h,the coating surface did not change significantly.Electrochemical impedance spectroscopy results show that the impedance of the coating was 2-3 orders of magnitude higher than that of the substrate.Combined with XRD,a small amount of NaCrS2 was generated on the coating surface,which had a certain blocking effect on the corrosive medium.Therefore,the non-reactive magnetron sputtering coating could still maintain good corrosion resistance after being corroded for 180h at high temperature.Cr₃C₂ coating was prepared by reactive magnetron sputtering technology.By changing the flow rate ratio of acetylene to argon to 1:8,1:6 and 1:4,it was found that when acetylene/argon was 1:6,the Cr and C content of the coating was 33:56 and the oxygen content was only 4.35%.The main components of the coating were Cr₃C₂ and Cr7C3.Compared with the non-reactive magnetron sputtering,the sp3 a-c content in the coating was higher,indicating that the surface stress was higher.The XRD pattern showed that the crystallinity of the films prepared by reactive magnetron sputtering was better.After corrosion in molten sodium polysulfide for 120h,there was no obvious change in the surface of the coating,and only a small amount of NaCrS2 was formed.The results of electrochemical impedance spectroscopy show that the Rt value of the coating decreases first and then increases.Combined with XRD analysis,it shows that the products on the surface of the coating inhibit the progress of corrosion during the corrosion process and have a good protective effect on the substrate.