Preparation Of Gel Electrolyte Based On Multiple Physical Interactions And Its Application In Integrated Flexible Supercapacitors

Due to the growing demand for wearable portable electronic devices,flexible supercapacitors are received increasing attention.In general,the flexible supercapacitor is composed of solid electrode and gel electrolyte multilayers.However,in practical applications,when multiple stretching and bending occurred,it is easy to delamination and dislocation between layers,resulting in device failure.Therefore,it is necessary to design a self-healing hydrogel polymer electrolyte（GPE）that can withstand tension and bending.The conductive ions commonly used in GPE are Li⁺,Na⁺and K⁺.In recent years,multivalent ions(Ca²⁺,Mg²⁺)have attracted extensive research interest due to their stable valence and relatively small ionic radius.Compared with monovalent cations,polyvalent cations can associate with multiple carboxyl groups at the same time,resulting in a larger coordination number and a multidimensional valence bond structure,resulting in a more compact network.More importantly,this multivalent cation can transfer multiple electrons to improve the specific energy,and can be applied to supercapacitors.In this paper,three kinds of GPE were prepared based on polyvalent ions,and their applications in flexible integrated supercapacitors were explored.The specific contents are as follow:System 1:prepared physically crosslinked self-healing PAA-PHA-Co SO₄GPE by hydrophobic association.The ionic conductivity reached 2.87 S/m and the elongation at break was 3100%.The experimental results showed that the synergistic effect of hydrogen bonds and metal ions coordination in the hydrophobic association system made PAA-PHA-Co SO₄GPE exhibit good self-healing ability,and the self-healing efficiency reached 95%.In addition,PANI-PAA-PHA-Co SO₄based integrated flexible supercapacitor（IFSC）prepared by in-situ polymerization of aniline showed a maximum specific capacitance of 220 m F/cm²at a current density of 0.5 m A/cm².Due to the self-healing property of PAA-PHA-Co SO₄GPE,PANI-PAA-PHA-Co SO₄-based IFSC also has self-healing property at low temperature and room temperature,and still has 95%high capacitance retention after 6 times cutting/repairing.And PANI-PAA-PHA-Co SO₄-based IFSC still has 80.25%capacitance retention after 35 consecutive mechanical stimuli（bending,extrusion,torsion,rolling and compression）.System 2:Polyvinyl alcohol/sodium alginate/cobalt sulfate gel polymer electrolyte（PVA-SA-Co SO₄GPE）with multiple physical crosslinking was prepared by freezing-thawing method and soaking method.The experimental results showed that due to the synergistic effect of hydrogen bonds and ion coordination,the double network GPE had a high tensile strength（1.25 MPa）.and good ionic conductivity（3.67 S/m）.PANI-PVA-SA-Co SO₄-based IFSC prepared by in-situ polymerization of ANI exhibited a maximum specific capacitance of 149 m F/cm²at a current density of 1 m A/cm².PANI-PVA-SA-Co SO₄based IFSC had excellent bending behavior,with 95%capacitance retention at different bending angles and 82%capacitance retention at-20°C.In addition,PANI-PVA-SA-Co SO₄-based IFSC still exhibited excellent energy storage capacity under different mechanical stimuli（magnetic stirring,hammering,loading and repeated bending）.System 3:Poly（hydroxyethyl acrylamide）/xanthan gum/calcium chloride gel polymer electrolyte（PHEA-XG-Ca Cl₂GPE）was prepared by free radical polymerization,and the GPE exhibited low temperature resistance,self-healing and good conductivity.Its tensile strength was 0.457 MPa,elongation was 3160%,ionic conductivity was 2.88 S/m,and the GPE still had good mechanical strength and conductivity at low temperature（-20°C）.The PANI-PHEA-XG-Ca Cl₂based IFSC was obtained by in-situ deposition of ANI on GPE,which had a specific capacitance of161.93 m F/cm²（current density of 2 m A/cm²）.IFSC had good flexibility（86%capacitance retention after different bending angles）.In addition,the flexible supercapacitor also had excellent low temperature resistance,and the capacitance retention was still 93%at low temperature-20°C.PANI-PHEA-XG-Ca Cl₂-based IFSC had self-healing property,and still had high capacitance retention of 98%after four cutting/repairing.