The Electrochemical Performance Study And The Synthesis Of Bismuth Oxyhalide(X=F,Cl)

Since the 21 st century,the issues of environment and resource highlighted,what is needed to do is not only reducing emissions and pollution,saving energy,but also developing clean and green energy.In order to ease the pressure on resources and environment,we should develop more efficient energy storage devices.Putting forward the new concept of battery,developing new electrode materials and studying new systems of battery,is the power source to drive the battery technology progress,and the hotspot in the research of energy storage.In this paper,BiOF and BiOCl were synthesised and studied as negative electrode materials in BiOX // C asymmeteric supercapacitor and BiOX // Ni?OH?₂ alkaline rechargeable battery respecitively.The main contents of this paper are as follows:1.The sub-micro oxyfluoride bismuth powder material was synthesised by the precipitation reaction between bismuth nitrate and sodium fluoride at room temperature.Then the electrodes of Bi OF and active carbon were prepared,and were assembled into asymmeteric supercapacitor to study electrochemical performance.The optimum conditions were obtained by a series of condition experiments of the proporation of bismuth nitrate and sodium fluoride,the dropping speed of the sodium fluoride,and the solvent.The obtained BiOF is clusters form in sub-micro grade,which is constructed by nanosheets with thickness of 20⁴0 nm.The specific capacitance of the BiOF electrode was 818 F g-1,with a retention of 90% after 1000 cycls.2.The BiOF // Ni?OH?₂ secondary battery was fabricated with nickel hydroxide and BiOF synthesised by the ways as the third chapter mentioned.The effect of different electrolyte on electrochemical performance was studied then.KOH coupled with KF was found more suitable for this battery by comparing the electrochemical performances of pure KF system and KOH system.Cyclic voltammograms tests under different scan rates,constant current charge-discharge tests under different current densities and cycle life test were taken in the selected electrolyte.What is worthy mentioned is that the rate performance in 2 M KF + 4 M KOH electrolyte is relatively better than its in 6 M KOH electrolyte.The specific capacitances kept well with the specific capacitance at 2 A g-1was 98.4% of it at 0.5 A g-1.3.Two different BiOCl materials with different shape and size were synthesisedby hydrolysis reaction under different conditions.The two materials are micron-flower and nanosheets with lamellar structure respectively,obviously,their sizes are very different.Then the BiOCl // Ni?OH?₂ secondary battery was constructed with spherical nickel hydroxide and BiOCl to study the electrochemical properties.The results showed that specific capacity of BiOCl nanosheets with smaller size is higher,exhibiting a specific capacitance of 146 mAh g-1at 0.5 A g-1,while the rate performance and cycle stability of BiOCl micron-flower with better dispersion are better,the specific capacitance at 5 A g-1 was 90.2% of it at 1 A g-1,and it showed 78%retention after 500 cycles.