Applications And Performance Of Flexible,Self-Healable And Conductive Hydrogels In Functional Supercapacitors

At present,the functional design of supercapacitor has become one of the research hotspots in recent years due to its application prospect in the field of new intelligent electronic devices such as smart clothes.In addition to the basic energy storage performance,it is also required to have good mechanical properties and self-healing performance to ensure the stable energy output after being subjected to various deformations or sudden damages.Double network hydrogels behave high mechanical properties,and some with dynamic network can possess self-healing properties.Therefore,the dual network hydrogels are used as matrix materials to develop the strong and self-healable hydrogel electrodes and hydrogel electrolytes,and try to assemble the flexible,all-hydrogel supercapacitors with self-healing ability.It may provide reference for the application of hydrogels in the field of energy storage and the functionalization of supercapacitors.The details are as follows:（1）In-situ copolymerization of Maba and aniline occurring in double network hydrogels consisting of borate ester bonds and ionic bonds,the PVA/PANI hydrogel（PPH_n）electrode is prepared by ionic bonding to form physical entanglement between polyvinyl alcohol（PVA）chains and polyaniline（PANI）chains.The introduction of PANI enhances the mechanical and electrochemical properties of hydrogels.The presence of Maba allows PANI to enter and distribute evenly in hydrogels,and PANI chains and PVA chains are involved in the subsequent self-healing process.The research on the influence of variables shows that PPH_0.03 electrode not only has the best mechanical properties and electrochemical properties,but also has excellent self-healing performance,fatigue resistance,stability and flexibility.（2）The integrated all-hydrogel supercapacitor is prepared through a layer-by-layer gelation strategy,while the PPH_0.03 works as the electrode layer and the protonated double network hydrogel（PCH）works as the electrolyte layer.The design of the integrated structure improves the electrochemical performance of the all-hydrogel supercapacitor.The integrated hydrogel supercapacitor has excellent flexibility and self-healing properties.Even after being subjected to various deformations（e.g.,stretching,compressing,bending and even pinning）,it can maintain stable energy output.（3）Hydroxypropyl cellulose（HPC）,which is both a porogen and a powerful ion-adsorbent,is introduced to PCH electrolyte to prepare the PVA-CPBA-HPC-Ca hydrogel electrolyte.Furthermore,it is integrated with graphite foil electrode to form the integrated supercapacitors.Due to the strong ionic dipole interaction between HPC and free ions,a large number of free ions are absorbed into the hydrogel,thus improving the mechanical properties,electrochemical properties and self-healing properties of the hydrogel electrolyte.The research on the influence of variables shows that PVA-CPBA-HPC_0.5-Ca₁₀electrolyte has the best performances.In addition,the addition of HPC can improve the self-discharge resistance of hydrogel electrolyte.