The Improvement Of Lithium/Sodium Storage Capacity Of Calix[4] Quinone With Polysiloxane Imidazole Electrolyte

Secondary batteries stand out among the new energy storage technologies due to their fast response,flexible application scenarios and long service life.Compared with inorganic cathodes,organic cathodes show the advantages of green and environmental protection and structural designability.At present,organic small molecules as cathode and lithium/sodium metal as anode in the batteries are facing two major challenges:the small molecules are easily soluble in traditional organic electrolyte causing rapid capacity degradation,and the metal dendrites at the anode may cause short circuit by puncturing the battery diaphragm.Solid electrolytes with excellent mechanical properties can inhibit the growth of dendrites and do not contain or store electrolyte inside them.Using solid electrolytes in the above batteries is a good strategy to solve the both problems.In this work,a siloxane imidazole polyionic liquid was synthesized and prepared as a quasi-solid electrolyte membrane PS4（Polysiloxane imidazole ionic liquid-M2-40%Polyvinylidene fluoride hexafluoropropylene,PSI-M2-40%PVDF-HFP）.The same electrolyte（1 M Li PF₆in EC/DMC=1:1,v/v）was used to prepare the PS4 gel polymer electrolyte with quinone Calix[4]quinone（C4Q）as the anode,and was compared with the purchased Celgard 2500 diaphragm（already infiltrated with electrolyte）to assemble the secondary batteries and explore the influences of electrolyte on C4Q cathode lithium/sodium storage performance.（1）The target product gel polymer（PS4）was synthesized by one-step polymerization,anion exchange and cross-linking of polyvinylidene fluoride hexafluoropropylene.The ionic conductivity of gel polymer electrolyte is 1.8×10^-4 S cm^-1,lithium-ion migration number up to 0.75,lithium/sodium electrochemical stability window 5.0V and 4.0V,thermodynamic stability,excellent mechanical properties,suitable for use as electrolyte materials for lithium ion and sodium ion batteries.（2）In lithium-ion batteries,the specific capacity of Li|Celgard 2500|C4Q rapidly decays from the initial 441 m Ah g^-1 to 23 m Ah g^-1 after 20 cycles at 1.0 C,and the capacity retention rate is less than 10%.In contrast,after 1000 cycles,the battery capacity of Li|PS4|C4Q remains at 153 m Ah g^-1,and the coulomb efficiency is close to 100%.When the current density is increased to 5 C,the discharge specific capacity can still be maintained at 122 m Ah g^-1.（3）In sodium-ion batteries,the specific capacity of Na|Celgard 2500|C4Q battery rapidly decays less than 50 m Ah g^-1 after 20 cycles.The capacity of Na|PS4|C4Q can achieve 417 m Ah g^-1,and the specific capacity after 5000 charge and discharge is maintained at 136 m Ah g^-1,and the coulomb efficiency is more than 100%.