| With the continuous improvement of people’s quality of life,smart bracelets,watches,mobile phones and other industries have gradually developed into an indispensable part of daily life.The advent of folding screen mobile phones also shows that flexible electronics devices have become a promising direction in the field of electronic devices.However,as an important energy storage element,traditional liquid batteries have problems such as electrolyte leakage and lack of flexibility.Therefore,a high-performance flexible solid-state battery is urgently needed to replace it,and how to prepare flexible solid-state electrolyte has become the current research focus.Gel electrolyte（GPE）,as a new type of semi-solid/semi-liquid phase material with polymer network as skeleton,has relatively high ionic conductivity and good flexibility,and is considered as one of the alternative materials of liquid electrolyte.However,its semi-solid/semi-liquid phase structure also leads to poor environmental stability of GPE,easy volatilization of liquid electrolyte and obvious difference of ionic conductivity compared with liquid electrolyte,which limits its further application.In recent years,flexible nanocomposites provide a new direction for the further development of traditional GPE.In this paper,the wood pulp fiber was oxidized by TEMPO（tetramethylpiperidine oxide）,and the uniform and stable carboxyl modified cellulose nanofiber（C-CNFs）was obtained after homogenization.C-CNFs and polyvinyl alcohol solution were mixed and crosslinked by one-pot sol method to obtain cellulose mixed gel matrix,and gel electrolyte（GPE）was obtained by soaking electrolyte.The stability and ionic conductivity of GPE were studied,and the effects of oxidation degree and addition number of C-CNFs on its performance were analyzed.A flexible zinc-air battery was constructed by laminating zinc foil,air electrode and cellulose mixed GPE,and its electrochemical performance was studied.The microstructure of cellulose mixed GPE,the binding form and strengthening mechanism of C-CNFs in GPE were analyzed.The main research results are as follows:（1）Using softwood pulp as raw material for TEMPO oxidation treatment and mechanical homogenization to obtain translucent and uniform carboxylated modified cellulose nanofibers.After oxidation modification,coniferous wood fiber swelled in volume and became more uniform and transparent.The introduction of polar group（-COOH）led to a significant increase in water retention value,which increased by0.37 g/g and 15.4%compared with CNFs.SEM images show that there is not much difference in fiber morphology between CNFs and C-CNFs,and the ratio of length to diameter is kept at 100:1.（2）Cellulose mixed GPE prepared by one-pot sol method has been significantly improved in ionic conductivity and environmental stability.The PVA-0.8%C-CNFs-based GPE obtained by controlling the addition amount of Na Cl O in the oxidation process at 9mmol/L has excellent properties,the ionic conductivity reaches0.31 S·cm-1,the mass retention rate reaches 76%after standing at room temperature for 48 hours,the maximum tensile stress reaches 689 k Pa,and the deformation amount reaches 131%.（3）Sandwich structure zinc-air battery was prepared by lamination method,and low resistance carbon paper-air cathode was prepared by wet paper making and surface coating process,which was compounded with zinc foil and GPE to build a stable battery system.The electrochemical performance of the assembled zinc-air battery was tested.it was found that when the GPE content in C-CNFs was 0.8%（relative to PVA）,the initial voltage window of the assembled zinc-air battery was1.63V,the maximum current density reached 124.3 m A cm-3,the maximum peak power density reached 62.2 m W cm-3,and the discharge capacity reached 149.1 m Ah cm-3.at the same time,it could stably charge and discharge at constant current for 60hours,and the cycle times could reach 180.At the same time,the flexible zinc-air battery still keeps stable working performance in the bending state. |
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