Synthesis Of Cyclic Sulfite Derivatives And Their Application In Lithium Ion Batteries

With the rapid development and commercialization of electric vehicles,the storage of new energy sources such as wind and solar energy is urgently demanding for high-performance batteries.Based on the related literature,we combined cyclic glycerol sulfite with cyclic glycerol carbonate and designed a series of cyclic glycerol sulfite derivatives:bis((2-oxido-1,3,2-dioxathiolan-4-yl)methyl)terephthalate(abbreviated as BDMT),bis((2-oxido-1,3,2-dioxathiolan-4-yl)methyl)oxalate(abbreviated as BDMO),(2-oxido-1,3,2-dioxathiolan-4-yl)methyl benzenesulfonate(abbreviated as ODMB),(2-oxido-1,3,2-dioxathiolan-4-yl)methyl 4-methylbenzenesulfonate(abbreviated as ODMM).The chemical structures of four derivatives were characterized by 1H NMR and FTIR.Their thermal stability and the pyrolysis process were investigated by TG-FTIR technology.We measured the wettability of the electrolyte by a contact angle analyzer.Finally,the four compounds were used as electrolyte additives to study their effects on the electrochemical performance of Li/LiCoO2 batteries by electrochemical tests,and the surface morphology of cathode before and after the cell cycle was observed using scanning electron microscope.The results were as follows:1H NMR and FTIR data indicated that the intermediate 1,2-cyclic sulfite glycerol and its four derivatives with high purity were successfully synthesized,and the yields of BDMT?BDMO?ODMB?ODMM were 77.09%,23.3%,71%,53%,respectively.TG-FTIR results showed that the 5 wt.%pyrolysis temperatures of BDMT,BDMO,ODMB and ODMM was 245?,236 0C,256? and 255?,respectively,which mean all had good thermal stability.The wettability of the electrolyte results presented that when BDMT,BDMO,ODMB and ODMM was added at a concentration of 0.5 wt.%,respectively,the contact angle was smaller(40.8°?42.7°?37.8°?38.6°)than the blank electrolyte(44.3°);when the wettability time of the electrolyte and the separator was extended,the contact angles of the electrolytes of 0.5 wt.%ODMB and ODMM were getting smaller and smaller,arrived to 30.3°?27°,respectively,indicating that they can both improve the wettability of the electrolyte and the separator,especially after adding ODMB and ODMM,the separator can be quickly wetted,and the formation time of the battery was effectively shortened.The electrochemical performance test of Li/LiCoO2 half-cell showed that when the addition amount of BDMT and BDMO was 0.3 wt.%,the battery had better cycle stability;when 0.7 wt.%of ODMB and ODMM were added,the battery not only had high capacity(reached to 147.98 mA h·g-1?136.91 mA h·g-1)and cycle efficiency(reached to 98.86%?99%),but also had excellent cycle stability,especially when 0.7 wt.%of ODMB was added,the battery could circulate at a high rate and maintain a high capacity.According to the AC impedance and SEM test results,when 0.3 wt.%of BDMT,BDMO and 0.7 wt.%of ODMB and ODMM were added respectively,the impedance value of lithium-ion batteries was smaller than other cells after 50 cycles.It was indicated that the addition of additives at this concentration could effectively improve the interface stability between the electrolyte and the electrode,and form a uniform and dense SEI protective film on the surface of LiCoO2 electrode material.