Study On The Coating Of Y-doped ZrO₂ On K₂FeO₄ And Its Effect On Electrochemical Performance Of The Cathode Material

Since"super-iron"battery first reported in 1990's, regarded as the revolutionary discovery, it has become a hot spot in battery field for its many attractive advantages. However, super-iron battery has not brought its advantages into full application due to the instability and zersetzlichkeit of ferrate itself. The application of protective coating can be an ideal choice for improving the stability of potassium ferrate. In this thesis, zirconia doped by yttria (Zr/Y) was chosen to coat K₂FeO₄ and the technique of Zr/Y coated ferrates was firstly researched. Followed by the electrochemical performance of the coated potassium ferrate, the discharge performance of the button cells assembled with coated potassium ferrate were systematically discussed.In this paper, the Zr/Y coatings were obtained through the conversion of ZrOCl₂ and Y(NO₃)₃. The influence factors (the amount of Zr and Y used in the coating process, the drying temperature of coated K₂FeO₄ and the pH adjusted in the coating process ) on the discharge performance of K₂FeO₄ cathodes were investigated. The optimum coating technology obtained at room temperature can be listed as follows: m(ZrOCl₂.8H₂O):m(K₂FeO₄) is 2:100³:100; n(Y):n(Zr) is 9:100; the coating pH is adjusted to 7⁸, and the drying temperature is 60℃.Then using zinc as anode, the stimulated cells were assembled to test the coated potassium ferrate cathode material. The results show that when the coated potassium ferrate cathode was stored in dried air for four months, the discharge efficiency can still remain above 50%; Similarly, when it was stored in saturated KOH for two weeks, the discharge efficiency can be 63%; When discharged in 10 mol.L-1 KOH, the specific capacity of the coated potassium ferrate cathode reaches up to 206mAh.g-1, which suggests that the entry of Y to the lattice of ZrO₂ can evidently improve the discharge process of K₂FeO₄ cathode.when Y enters the lattice of ZrO₂, the discharge process of potassium ferrate can be evidently improved. Extra evidence obtained from Alternating Current Impedance and Cyclic Voltammogram shows that when potassium ferrate was coated with Y-doped ZrO₂ film, the stability of potassium ferrate is sustained compared with that potassium ferrate coated with Zr film. What is more, Y-doped ZrO₂ film can also improve the conduction of the electron in the cathode material, and greatly improve the discharge performance of potassium ferrate eventually. Finally, the coated potassium ferrate cathode material is assembled into button cell, the sorts and usage of the conductive agent were investigated. And the battery separators were chosen from different membrane. Eventually, acetylene black and non-woven polypropylene grafted membrane were chosen as the optimum for button cells. The factors such as discharge capacity, discharge voltage plateau and performance stability of the potassium ferrate button cells are superior to the crown cells assembled in the experiment.