Modification Of Ether Electrolyte For Sodiumion Battery And Calculation Prediction

The biggest obstacle to the practical application of sodium-ion batteries is that the graphite negative electrode in traditional lithium-ion batteries performs poorly in sodium-ion batteries.The ether-based sodium ion electrolyte makes the graphite negative electrode possible,and it uses the co-intercalation mode to make the graphite negative electrode be used in sodium ion batteries.However,the ether electrolyte exhibits lower oxidation potential and cycle stability in the sodium ion positive electrode.The electrolyte is prone to oxidative decomposition at the high potential of the positive electrode,which increases the irreversible reaction of the electrolyte.In order to solve this problem,this article uses the addition of sodium nitrate to increase the oxidation potential of the electrolyte.This method is relatively simple and low in cost,which is of great significance to the development of sodium ion battery.It also predicts the performance of the electrolyte through density functional theory calculations,which can greatly reduce the development cycle of sodium ion electrolyte.This thesis focuses on the following contents for the modified electrolyte:1.Using a simple method of dissolving sodium nitrate to prepare diethylene glycol dimethyl ether（G2）/Na NO₃ electrolyte,the oxidation voltage of the modified electrolyte obtained is increased to 4.6 V,the cycle performance is increased to 200 cycles,and the coulombic efficiency is 98%the above.Through electrochemical and physical chemical characterization,it is found that Na₃N is formed in the cathode solid electrolyte interface after adding sodium nitrate.The mechanism of Na₃N’s performance improvement is explained by computational materials science,and the actual application of the ether-based sodium ion full battery is carried out.The voltage can reach 1.5 V～3.5 V.2.The choice of traditional electrolyte solvents and additives is random,and it takes a lot of trial and error to find suitable electrolyte solvents and additives.In the first part,the relationship between the electrolyte solvent,the positive electrode,and the additive is summarized.This part uses the following calculation conclusions:（1）The lower the charge oscillation in the differential charge density calculation,the less likely the reaction is to proceed.Easily oxidized electrolyte solvent;（2）The higher the HOMO value,the easier it is for the additive to be adsorbed on the positive electrode.The oxidation reaction is limited to protect the electrolyte.Using this method,it is predicted that the tetraethylene glycol dimethyl ether solvent（G4）and Na Cl O₄ additives have better performance.Calculate and predict the performance of electrolyte solvents and additives,which can greatly reduce the cycle and cost of electrolyte research and development.