Polymerized ionic liquids(PILs),containing one or more ionic liquids monomer in a repeating unit,are a new type of polymer.PILs possess designable chemical structures,tunable morphology and well functionalization.Moreover,with the merits of inherent high ionic conductivity,PILs are widely used in the separator,binder and electrolyte of lithium-ion batteries(LIBs).In theory,PILs incorporated redox groups are capable of realizing lithium storage,which are potential to replace commercial graphene for further increasing the specific capacities by“superlithiation performance”.Herein,this work prepared redox PILs with positively charged skeletons as anode materials for the first time.To enhance electronic conductivity,PILs are designed by selecting suitable ILs monomers,improving the utilization efficiency of redox sites to realize“superlithiation performance”.The specific studies are as follows:1,imidazolium polymerized ionic liquids(PILs-Im)have been prepared by imidazolium ionic liquids(ILs-Im)as monomers under the condition of zinc chloride(Zn Cl2)molten salt as template and catalyst at 400 oC.The repeating unit of obtained PILs-Im consists of one imidazolium ring,one triazine ring and the methylene between them.PILs-Im anode exhibits a discharged capacity of 846.6 m Ah g-1 at the current density of 0.1 A g-1,which means forming Li3(C/N)6 compound during lithiation process;Due to the positively charged skeleton and stable chemical structure,PILs-Im anode exhibits the discharge capacity of 165 m Ah g-1 at 10 A g-1,indicating excellent rate performance;PILs-Im anode displays the capacity retention rate of nearly 100%after 500 cycles at 1 A g-1.In situ FTIR,in situ XPS and DFT calculations indicate that the N atom on the aromatic ring and the C atom on the methylene ring participate in Li-storage.2,pyridinium polymerized ionic liquids(PILs-Py)have been prepared by pyridinium ionic liquids(ILs-Py)as monomers by the same method.To investigate the most suitable polymerization temperatures for forming triazine rings,the polymerization temperatures are set as 300,400 and 500 oC.The molecular composition and morphology of PILs-Py-400 obtained at 400 oC are in line with the design envision,which is composed of a pyridonium ring,a triazine ring and methylene between them.The repeating unit of obtained PILs-Py consists of one pyridinium ring,one triazine ring and the methylene between them.PILs-Py-400 anode exhibits the highest discharged capacity of 1640.0 m Ah g-1 at the current density of 0.1 A g-1,which means forming Li6(C/N)6 compound and realizing“superlithiation performance”during lithiation process;PILs-Py-400 anode exhibits the discharge capacity of 1098 m Ah g-1 at 5 A g-1,indicating excellent rate performance;Moreover,PILs-Py-400 anode displays the capacity retention rate of 92.2%after 500 cycles at 1 A g-1.In situ FTIR,DFT and Gibbs free energy calculations indicate that all atoms in repeating units participate in Li-storage.3,in order to regulate the surface charge distribution of PILs-Py,PILs-Py-2%GN and PILs-Py-5%GN composites with graphene(GN)content of 2wt%and 5wt%were prepared using layered GN with high conductivity as the polymeric substrate.XRD,Raman and HRTEM results show that PILs-Py-2/5%GN materials have been successfully synthesized.The electrochemical performances show that PILs-Py-2%GN can further improve the magnification performance of the material on the basis of realizing ultra-lithium performance.After running50 cycles at the current density of 0.1 A g-1,the specific capacity of PILs-Py-2%GN was 1688m Ah g-1.Moreover,PILs-Py-2%GN displayed superior rate capacity of 508.2/360.6 m Ah g-1at 5/10 A g-1.The capacity retention rate was 88.8%after 500 cycles at 10.0 A g-1.The results of CV,EIS and GITT show that the combination of GN is beneficial to the improvement of lithium ion diffusion kinetics and charge transfer kinetics. |