Synthesis And Application For Li Batteries Of Novel Organic Cathode Material Calix[8] Quinone

Organic cathode materials are one of the most potential electrode materials due to their numerous advantages,such as large specific capacity,designability,abundant raw materials,environmental friendliness,renewability.However,their easy solution in organic electrolyte and poor stability limits their development.A cyclic structure Calix[8]quinone（C8Q）with8 p-benzoquinone units connected by methylene groups is designed and synthesized,which can be used for 16 Li⁺insertion/extraction(C_theo=446 mAh g^-1).Due to the exist of methylene,the steric hindrance is small,and reversible redox reactions can take place in all active sites.C8Q has a larger molecular weight and cavity structure than its similar substances,calix[4]quinone（Calix[4]quinone,C4Q）and calix[6]quinone（C6Q）,Its cycle stability in 1 MLiPF6/EC+DMC（1:1,w/w）electrolyte has been significantly improved.In addition,this paper also studied the lithium storage performance of C8Q in 4.2 MLiTFSI/AN’s high-concentration electrolytes（HCE）and localized high-concentration electrolytes（LHCE）.（1）Using calix[8]arene or its p-tert-butyl and p-benzyloxy derivatives as raw materials,three different synthesis methods are tried:one-step oxidation（HCl O₄/Pb O₂ oxidation method）,reduction-oxidation method,and debenzylation-oxidation method.Finally,using4-benzyloxyphenol as a raw material,C8Q is successfully synthesized through a three-step reaction of ring formation,debenzylation and oxidation,and the yield is as high as 23%.（2）At a current density of 0.2 C,the initial discharge specific capacity of C8Q LIBs using 1 MLiPF₆/EC+DMC electrolyte reaches 408 mAh g^-1.After 100 cycles,the capacity still maintains at 213 mAh g^-1,and the coulombic efficiency is close to 99%.Matching C8Q with HCE,the first-cycle discharge capacity of the battery is 426 mAh g^-1.After 100 cycles,the capacity still matains 341 mAh g^-1,and the average coulombic efficiency is 99.99%.In addition,the ultra-concentrated system battery also shows better rate performance.In addition,the high-concentration system battery also shows better rate performance.Even at a high current density of 5 C,the discharge specific capacity remains up to 160 mAh g^-1.（3）HCE has the problems of high viscosity and high cost.The thesis also tries to use1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether（HFE）dilute the HCE above and prepare it according to the volume ratio of HCE and HFE at 1:1 and 1:2 to obtain to prepare localized high-concentration electrolytes LHCE（1:1）and LHCE（1:2）,reducing the cost and viscosity of HCE and studying their electrochemical performance.The viscosity of LHCE（1:1）and LHCE（1:2）is greatly reduced,and the wettability is significantly improved.In addition,the conductivity of the two electrolytes increases from 0.97 m S cm^-1（4.2 MLiTFSI/AN）to2.19 m S cm^-1 and 2.22 m S cm^-1,respectively.The initial discharge specific capacities of C8Q LIBs using two localized high-concentration electrolytes are 439 mAh g^-1 and 439mAh g^-1,respectively.At 0.2 C,the specific discharge capacities are 302 mAh g^-1and 300mAh g^-1 after 100 cycles,respectively.And the coulombic efficiency is about 100%.Among them,LCHE（1:2）electrolyte are better in viscosity,impedance and rate performance.Even at a high current density of 5 C,the discharge capacity is close to 170 mAh g^-1.