Synthesis And Application Of Tetrafluoroboric Acid Spirocyclic Quaternary Ammonium Salt For Supercapacitor Electrolyte

Supercapacitors are also called electrochemical capacitors, the performance of which is between chemical batteries and conventional electrostatic capacitors.Currently, the biggest shortcoming of supercapacitors is lower energy density.Scientists have been paying more attention on how to advance the energy density in the field of supercapacitors in recent years. The formula of energy density is as follows:2（28）5.0 CUE（E means energy density, C means capacitance, U means operating voltage）. the capacitance is determined by electrode and the operating voltage is mainly determined by electrolyte. The electrolyte applied in supercapacitors can be classified as four types. One of them is organic electrolyte, which is the current commercial mainstream electrolyte because of its low cost, excellent electrochemical properties,higher operating voltage. Electrode are mainly classified as three types by active materials, based electrode is widely applied in supercapacitors due to lower cost, longer cycle life, higher charge /discharge efficiency.Synthesis of Tetrafluoroborate spiro cyclic quaternary ammonium salt（SQA-BF₄）from 8-oxa-5-azonia-spiro[4,5]decane bromide（SQA-Br） and Tetrafluoroborate（HBF₄）was by means of ion exchange under negative pressure conditions in this thesis. To get the optimal synthesis conditions range, the factors like reaction solvent, molar ratio, reaction temperature, reaction time on Conversion rate were tested. The relationship among the factors was precisely analyzed to get the optimized condition;The characterization of sample was by means of FT-IR、LC-MS、NMR、TG—DTG;The purified,vacuum dried tetrafluoroborate spiro cyclic quaternary ammonium salt（SQA-BF₄） was formulated as electrolyte with solvent in a glove box that was under a nitrogen atmosphere, then the Conductivity of the electrolyte was tested. The electrode and electrolyte were assembled as supercapacitors, which is used to test the electrochemical performance. To get the optimal Integrated ElectrochemicalPerformance of supercapacitors, the factors like type of solvent, Concentration of the electrolyte, type of activated carbon material, the type of the conductive agent were taken in consideration.The single factor experiment told that the reaction solvent is ethanol, the range of molar ratio:SQA-Br::HBF₄ =1:1.5¹:2.5, temperature: 50⁷0℃, time: 4⁶h. Then the results of REM experiments were as follows: molar ratio of n SQA-Br: n HBF₄ was 1;2.5; the reaction temperature was 72℃; and the reaction time was 4h. Finally,the conversion rate of SQA-Br is 86.66% in this optimized condition.FT-IR proved that CH₂ absorption peak appear in 2856cm^-1, 1465cm^-1, C-N absorption peak appear in 1256cm^-1, C-C absorption peak appear in 1020cm^-1, C-O-C absorption peak appear in 1205cm^-1, C-N absorption peak appear in 1080cm^-1, C-O-C absorption peak appear in 911cm^-1, which proved the production has the same structure of Tetrafluoroborate spiro cyclic quaternary ammonium salt（SQA-BF₄）.NMR analysis showed that, ¹³C- NMR was occurred in 63.11 ppm, 61.97 ppm,58.99 ppm, 20.94 ppm, which is the same as the theoretical target product in the number of peaks and the chemical shift, ¹H NMR was occurred in δ 4.03 – 3.88（m,4H）, 3.65 – 3.50（m, 5H）, 3.48 – 3.36（m, 4H）, 2.20 – 2.05（m, 4H）, which is the same as the theoretical target product in the number of peaks and the chemical shift,19F-NMR was occurred in δ^-150.36. Thermal gravimetric analysis proved that the sample did not decomposed within the range from room temperature to 382℃, which had a good thermal stability and could be applied in electrolyte of the supercapacitor with high stability.The factors like type of solvent and concentration of the electrolyte were tested.the optimal conditions were that the solvent of the electrolyte was AN+PC+DMF（1:1:1）, the concentration of the electrolyte was 1 mol/L, The results showed that the operating voltage was 3.0V, the capacitance was 18.53F·g^-1, the charge/discharge efficiency is 94.31%, the energy density was 83.40J·g^-1, Which was better than Et4NBF₄ in the same condition.The factors like type of activated carbon material and the type of the conductive agent were taken into consideration. The optimal conditions were that the type of activated carbon material was KLL, the typeof the conductive agent was graphene. The results showed that the operating voltage was 3.8V, the capacitance was 20.14F·g^-1, the energy density was 145.41J·g^-1.