Preparation Of PVA Based Self-healing Hydrogel Electrolyte And Its Application In Supercapacitor

Flexible supercapacitors are often subjected to external loads such as bending and stretching,and are vulnerable to destruction or even fracture,resulting in the performance of the device thus decreased or even disappeared.It is an effective solution to prepare self-healing supercapacitors using electrolytes materials with excellent mechanical and self-healing properties.Therefore,in this paper,polymer hydrogel electrolyte with outstanding mechanical and self-healing properties was prepared by freezing-thawing cycles,and polyaniline electrode material was polymerized in situ on the surface of electrolyte to form an all-in-one self-healing supercapacitor.The main work is as follows:（1）Physical crosslinked polyvinyl alcohol/sulfuric acid（PVA/H₂SO₄）hydrogel electrolyte was prepared by freezing-thawing cycles,with tensile strength of 0.29 MPa and ionic conductivity of57.8 m S cm^-1.The self-healing ability was characterized by ionic conductivity.After10 cutting/healing cycles,the ionic conductivity was still 25.9 m S cm^-1.Then all-in-one self-healing PANI-PVA/H₂SO₄ supercapacitor was prepared by in situ oxidation polymerization of polyaniline electrode on electrolyte surface.When the concentration of aniline is 0.2 mol L^-1 and the current density is 0.2 m A cm^-2,the supercapacitor shows the specific area capacitance of 470 m F cm^-2.Capacitance remains 75%after once healing.（2）PVA/BC/H₂SO₄ double network hydrogel electrolyte was prepared with bacterial cellulose（BC）as the second network.When the BC mass was 0.4%of PVA,the ionic conductivity was 138.9 m S cm^-1 and the tensile strength was 0.41 MPa,which were 140%and 41%higher than PVA/H₂SO₄hydrogels,respectively.After 2 cutting/healing cycles,the ionic conductivity is 81.9m S cm^-1.For all-in-one PANI-PVA/BC/H₂SO₄ supercapacitor,when the BC mass is0.6%of PVA and the aniline concentration is 0.2 mol L^-1,the specific area capacitance of the capacitor is 581 m F cm^-2 at the current density of 0.2 m A cm^-2,which is higher than the specific area capacitance of the supercapacitor based on PVA/H₂SO₄ electrolyte.The capacitance retention was 66%after once healing.（3）PVA/Gly/H₂SO₄ hydrogel electrolyte was prepared by compositing PVA and glycerin（Gly）.When the mass ratio of Gly to water is 1:2,the maximum tensile strength of hydrogel is 0.55 MPa,which is about 90%higher than that of PVA/H₂SO₄ hydrogel.When the mass ratio of Gly to water is 4:5,the ionic conductivity reaches the maximum of 66.9 m S cm^-1.And after 10 cutting/healing cycles,the ionic conductivity is 25.9 m S cm^-1.When the concentration of aniline is 0.3 mol L^-1,the PANI-PVA/Gly/H₂SO₄ supercapacitor shows the largest specific capacitance of 476m F cm^-2 at the current density of 0.2 m A cm^-2,the specific capacitance was higher than that of the PANI-PVA/H₂SO₄ supercapacitor.The capacitance retention was 57%after once healing.