Preparation And Performance Study Of Polyvinyl Alcohol-based Organic Gel Electrolyt

Portable electronic devices have attracted much attention because of their lightweight and diverse characteristics.Practicality is severely limited by the fact that traditional electrolytes bear large deformations that can cause damage to equipment or leakage of toxic liquids.Compared with traditional electrolytes,flexible gel electrolytes have good plasticity,extremely high safety,and high modulus values.Therefore,flexible electrolytes have attracted extensive research.At present,the research of flexible supercapacitors focuses on the flexibility of electrodes and the preparation of gel electrolytes.However,most of the flexible supercapacitors still have the problems of low ionic conductivity and low energy density.In addition,flexible supercapacitors also need to solve the problems of aging of gel electrolyte over time and poor stability of device performance caused by the water loss of the material itself.To solve these problems,a series of organogels with various excellent properties were prepared in this thesis.By adding different materials to change the crosslinking mode and coordination mode of ions of polyvinyl alcohol（PVA）,the design and preparation of gel polymer electrolyte was carried out.The machinability,safety and electrochemical performance of flexible devices is improved.This paper includes the following aspects:（1）PVA was selected as the research object,and terephthalic acid（PTY）was added to cross-link and esterify PVA to form strong force ester bonds to improve the mechanical properties of the gel.In addition,the bicoordinate Co²⁺was used instead of the widely used tricoordinated Fe³⁺,a stable self-healing polymer gel electrolyte PVA/PTY/Co Cl₂was obtained.The effects of the ratio of PVA to PTY and the content of Co²⁺on the gel strength were investigated by tensile test and electrochemical characterization.The properties of the prepared PVA/PTY/Co Cl₂organogel electrolyte were well maintained after repeated stretching.It can still recover quickly after stretching more than eight times,demonstrating good flexibility and stability.The supercapacitor fabricated with activated carbon exhibited small ohmic resistance（Rs:1.16Ω）and charge-transfer resistance（Rct:1.34Ω）values and an ionic conductivity of43.3 m S cm^-1.（2）A multifunctional antifreeze conductive organogel polyelectrolyte PVA/TTY was prepared by simultaneously introducing Tripentaerythritol（TTY）and H₂O/DMSO binary solvents to generate strong chemically bonded ether linkages via a high-temperature reaction using PVA.Based on the freezing resistance of the binary solvent H₂O/DMSO,the organogel exhibited good mechanical properties and long-term stability over the temperature range from-20 to 20℃.Meanwhile,the fabricated flexible supercapacitor showed excellent electrode specific capacitance,high ionic conductivity(45.2 m S cm^-1),the fabricated device still exhibits small Rs（3.02Ω）and Rct（0.95Ω）values even at low temperature of-20℃.Furthermore,the prepared organogels exhibited adjustable optical properties in different polar solvents and could serve as information storage devices for recording and wiping.（3）PVA as the system and adding benzimidazole derivative molecules（Bh）to form PVA/Bh multi-performance organogel in the binary solvent of ethylene glycol/water（H₂O/EG）.The prepared gel polymer electrolyte not only has a certain mechanical strength and flexibility but also exhibited fluorescence,light transmission,and recyclability.At the same time,PVA/Bh organogel has tunable optical behavior under the action of different metal ions,and then realizes the writing,reading and encryption of information.In addition,the flexible supercapacitor prepared by sandwiched PVA/Bh organogel between activated carbon electrodes exhibited small Rs（1.5Ω）and Rct（1.04Ω）,and the ionic conductivity of PVA/Bh organogel was 29.5 m S cm^-1.