Preparation And Application Of Fully Physically Crosslinked Hydrogel-Based Flexible Supercapacitors

Due to the growing demand for wearable portable electronic devices,flexible supercapacitors are receiving increasing attention.This thesis starts with the structural design and bases on the preparation strategy of full physical hydrogels,according to the self-crosslinking of N-hydroxyethyl acrylamide（HEA）monomer and the molecular template of poly（vinyl alcohol）（PVA）,the supramolecular full physical poly（vinyl alcohol）/poly（N-hydroxyethyl acrylamide）（PVA/PHEA）hydrogel with multiple hydrogen bonds was prepared.In addition,relying on the excellent properties of the hydrogel,by introducing conductive ions and organic solvents,two hydrogel electrolytes were prepared in this paper,and their applications in flexible all-in-one supercapacitors were explored,the details are as follows:（1）The self-crosslinkable HEA was used as a monomer,and PVA molecular chain with a large number of hydroxyl groups was introduced into its network without adding any chemical crosslinking agent to prepare PVA/PHEA hydrogel with full physical cross-linking.Due to the molecular template of PVA,under the optimal conditions,PVA/PHEA hydrogels exhibit excellent mechanical properties（tensile strength of 1.51MPa,tensile strain of 3090%and elastic modulus of 183.82 k Pa）.In addition,PVA/PHEA hydrogel also has self-healing property,fast self-recovery and excellent fatigue resistance property.（2）By introducing sulfuric acid（H₂SO₄）,PVA/PHEA hydrogel electrolyte（HGE）,which is strong and highly conductive（tensile strength of 1.13 MPa and ionic conductivity of 85.37 m S/cm）,was prepared based on the PVA/PHEA hydrogel.In addition,the stretchable and flexible supercapacitor based on the polyaniline（PANI）-decorated PANI-HGE film was prepared by rapid in-situ polymerization of high concentration of aniline（ANI）.Under optimal conditions,the stretchable and flexible supercapacitor has a high specific capacitance（98 m F/cm² at a current density of 0.2m A/cm²）,and the PANI-HGE has excellent mechanical properties（tensile strength of1.07 MPa and tear energy of 2492 J/m²）,good cycle stability and excellent flexibility.In addition,the stretchable and flexible supercapacitor has excellent deformation insensitivity during and after deformation,resistance to fatigue and self-recovery of the capacitor.More importantly,after the 7th self-healing cycle,the stretchable and flexible supercapacitor also has a specific capacitance retention of 84%.（3）The organic solvent Glycerin was introduced to prepare a tough,low temperature resistant PVA/PHEA-Glycerin HGE（ionic conductivity of 51.28 m S/cm and tensile strength of 1.91 MPa;it can still be stretched and conductive at-40℃）.In addition,the low temperature resistant and flexible supercapacitor was prepared by in-situ polymerization.Under optimal conditions,the specific capacitance of the low temperature resistant and flexible supercapacitor is 305 F/g（current density of 0.25A/g）.The low temperature resistant and flexible supercapacitor also has good low temperature resistance（it can be charged and discharged normally at-40℃,and the specific capacity retention is 61%）and excellent flexibility（not damaged after 20000cycles of 90°bent,and specific capacitance retention is 77%）.