Preparation Of Reversible Thermal-Responsive Self-Protective Electrolyte And Its Application In Supercapacitors

In the past few decades,the performance of energy storage devices such as lithiumion batteries and supercapacitors has made great progress.However,their safety has always been difficult to be guaranteed,especially issue of thermal runaway.For supercapacitors,if the heat accumulation cannot be eliminated in time,it will not only reduce the performance and service life of the supercapacitors,but may cause serious consequences such as fire or explosion.In this paper,based on thermal-responsive polymers,two safe electrolytes with reversible self-protection and thermal-switching functions are prepared,which are used in the field of micro-energy and flexible energy storage respectively.On this basis,the changes of specific capacitance,ionic conductivity,AC impedance,capacitance inhibition effect and other important parameters at different temperatures were studied.In combination with the analysis of material structure characterization and phase transition,the self-protection mechanism of reversible thermal-responsive polymer electrolyte was explored.The main work of this paper includes the following two specific aspects.(1)The all-printed self-protective micro-supercapacitor(ASP-MSC)based on Pluronic-g-(NIPAM&AM)thermal-responsive sol-gel transition electrolyte can achieve dynamic and controllable adjustment of electrochemical performance within a temperature window of 25-80 ℃,and it can reach a high specific capacitance loss ratio of more than 90% at high temperature of 80 ℃,as well as the ionic conductivity is less than 1% of the initial value.When the temperature drops to 25 ℃,its electrochemical performance can be restored.After multiple heating-cooling cycles,the ASP-MSC still possesses stable thermal runaway resistance behavior.On the basis of a single supercapacitor,the self-protection function after series-parallel connection is further explored and analyzed.(2)The safer self-protective flexible supercapacitor(SP-FSC)based on PNIPAMco-NMAM thermal-responsive solid-state electrolyte can realize the controllable adjustment of the capacity according to temperature changes.Thanks to the highly reversible thermal hydrophobic association of the PNIPAM-co-NMAM molecular chains and the hydrophilic-hydrophobic transition on the surface of the gel electrolyte,the self-protective polyelectrolytes with thermal-switching behavior can effectively inhibit the migration of conductive ions and make the specific capacitance of the flexible energy storage system drop sharply around 46 ℃,as well as the capacity attenuate by more than 85% when the temperature rises to 70 ℃.Even after multiple heating-cooling cycles,SP-FSC still possesses normal electrochemical performance and self-protection as opposed to one-time protection.