Study On The Synthesis And Performance Of Electrolyte For Aluminum Electrolytic Capacitor

An aluminum electrolytic capacitor is composed of aluminum casing,a core package and working electrolyte.The working electrolyte is the actual cathode of the aluminum electrolytic capacitor,which determines the electrochemical performance of the aluminum electrolytic capacitor.At present,the commonly used electrolyte in medium and high voltage electrolytic capacitor is branched long chain ammonium carboxylate,and the solvent is generally capacitive grade glycol.By introducing branched or oxygen-containing groups on the carbon chain,the solubility of electrolyte is increased and the ability to quickly repair defects in aluminum anodic oxide film,branched long chain ammonium carboxylate is considered to be the most promising electrolyte.In this project,three new types of branched long chain carboxylic acids(LC-PA,LC-MA and LC-DA),optimizes the synthesis process;and through a series of analysis and testing methods to carry out the structure of the branched long-chain carboxylic acid characterization;use solubility parameter theory and solubility experiment to investigate the solubility properties of LC-PA,LC-MA,LC-DA and commercial solutes sebacic acid and dodecanedioic acid,and study the high-temperature properties of the solutes;each solute is made into ammonium salt and boiled to obtain a working electrolyte,and the electrochemical performance and low-temperature performance of the working electrolyte are studied.The main research contents are as follows:1.Preparation of branched long-chain carboxylic acid:using 1,2-cyclohexanedione and dibenzylidene acetone as raw materials,the LC-PA product is synthesized through the Stetter reaction,esterolysis reaction and acidification process,with a maximum yield of 74.5%;Replace 1,2-cyclohexanedione with?-ketoglutarate,and use?-ketoglutarate and dibenzylidene acetone as raw materials to obtain LC-MA and LC-DA in one step through Stetter reaction,the highest total yield is 80.1%.2.Structural characterization:use ¹H NMR,¹³C NMR,FT-IR,MS and other analytical testing methods to characterize the structure of electrolyte.3.Performance test:the solubility parameter difference|??|of LC-PA,LC-MA,LC-DA,sebacic acid and dodecanedioic acid in ethylene glycol is estimated by solubility parameter theory.Compared with commercial solutes,LC-PA,LC-MA,and LC-DA have lower|??|in ethylene glycol;solubility experiment shows that LC-PA ammonium,LC-MA ammonium and LC-DA ammonium all have good solubility,the solubility in ethylene glycol is up to20%,while the solubility of ammonium sebacate is only 15%,and the solubility of ammonium dodecanedioate is 5%;TG thermogravimetric analysis founds that LC-PA,LC-MA and LC-DA have higher thermal decomposition temperature,indicating that they have better high-temperature stability;and the low-temperature performance test of the working electrolyte is carried out.LC-PA,LC-MA,LC-DA working electrolyte shows increased viscosity at-25?,but no solute precipitation,indicating that it has good low temperature stability;compared with sebacic acid,LC-PA,LC-MA,LC-DA working electrolyte has a higher flash voltage value,but the conductivity is slightly lower.