Imidazolium-based Polymeric Ionic Liquids:Synthesis,Self-healing Ability And Functionalization

Self-healing materials as a new type of smart materials are able to heal the mechanical damage and cracks during the application,which can further improve the lifetime and reliability of the materials.Over the last decades,self-healing materials have been widely studied,reported and made a significant progress.The discovery of new driving forces that are based on noncovalent interactions and dynamic covalent bonds to heal materials is a key factor in the progression of self-healing materials.Moreover,developing the functional materials with self-healing ability is very important for their application.Polymeric ionic liquids?PILs?are a new class of functional polymeric materials.PILs,especially imidazolium-based PILs,have been widely used in lithium ion battery,supercapacitor,catalysis and other fields due to their unique properties such as noninflammability,nonvolatility,wide electrochemical window,good thermostability and superior processability.However,these PILs also have been faced the mechanical damage during the use,which can decrease the lifetime and reliability of the PILs.Unfortunately,few studies have been devoted to the development of self-healing/healable PILs,possibly because of the complexity of the covalent modification in PILs and/or the degradation of PIL functions following the covalent modification.Here,we develop a series of self-healing imidazolium-based PILs.We further used the self-healing imidazolium-based PILs materials as solid polymer electrolytes in lithium matel battery and binder for Si anode in lithium ion battery,which can improve the service life and reliability of the batteries.All the contents as follows:1.A new kind of self-healing PILs were fabricated by taking advantage of their inherently featured chemistry.The healing performances of the imidazolium-based PIL copolymers can be effectively mediated by the counteranions in which the bulkier counteranions enhance the healing of the resultant copolymers.The bulkier the counterions are,the more easily?i.e.,at lower temperature?the PIL copolymers can be healed because the larger-sized counterions promote the mobility of the polymer chains and decrease the anion-cation interactions.The healing function of the PIL copolymers benefits from the inherently featured chemistry of the PIL segments that contain reversible anion-cation interactions,which can retain the excellent properties of PILs.2.We prepared a new solid-state ionogel polymer electrolyte that unprecedentedly combines beneficial properties of high conductivity(10^-3 S/cm at 25?C),flexibility,thermostability,healability and adhesiveness to the Li metal.The ionogel membranes were prepared by electrostatically immobilization of ionic liquids and Li salts in a hydrogen-bonded network of polymeric ionic liquids bearing ureido-pyrimidinone groups.The reversible nature of the hydrogen-bonding and electrostatic interactions in the ionogels endow them with capability to heal physical damages outside or inside a LMB,which can further enhance the safety of the battery and prolong the battery lifetime.3.We prepared a new Si anode binder via electrostatic complexation of a self-healing polymeric ionic liquids?PILs?with poly?acrylic acid?.This binder can adapt the large volume changes of Si anode during cycling and makes even pulverized Si particles remain coalesced without disintegration during repeated?de?lithiation,which offers an effective strategy to improve the cycling stability of Si electrode.Moreover,PIL is a well known material for solid polymer electrolytes in lithium ion batteries?LIBs?,which can effectively transfer Li ion and improve ionically conductive properties and specific capacity.The binder effect on the battery performance was also investigated by a series of galvanostatic measurements.For this testing,coin-type half-cells incorporating Li metal as both the reference and counter electrodes were prepared.The battery achieves a high discharge capacity of about2000 mA h/g at 500 mA/g and coulombic efficiency above 99%after about 80 cycles.This is the first time to use self-healing PIL for Si anode binder and thus expands the applications of PILs.This new binder will be used in the future for Si anode.4.We have prepared a self-healing PIL material by complexation of the imidazolium-based PILs,poly?sodium 4-styrenesulfonate?and SiO₂ in acid aqueous solution and then compaction.The as-prepared complexes possess excellent resistance to strong acid such as H₂SO₄ and HCl.The complexes also show superior self-healing ability due to the high flexibility and low charge density of the PILs.Moreover,the self-healing complexes gel can be used as polymer electrolyte in supercapacitor and healed after damage.