Preparation And Electrochemical Performance Of PVA-based Gel Electrolyte For Zinc Ion Batteries

With the demand for energy in modern society is growing day by day,the limitation of fossil fuels and the environmental pollution caused by it make mankind urgently need clean,safe and efficient energy conversion and energy storage technology.Owing to their high theoretical capacity(820 mAh g-1),proper working potential(-0.76 V vs E°),abundant reserves and intrinsically safe nature,aqueous zinc ion batteries(AZIBs)are recognized as one of the alternative choices for next generation energy storage systems.In the practical application of aqueous zinc ion batteries,there are serious problems such as dendrite growth,continuous side reactions and electrolyte leakage.As a solution for flexible wearable devices,gel electrolyte is expected to solve these problems.However,due to the high viscosity,poor fluidity,and the interaction between filler functional groups and electrolyte ions,gel electrolytes have low ionic conductivity.The gap between the ionic conductivity of the gel electrolyte and the liquid electrolyte limits the practical application of the gel electrolyte.Thus,the development of suitable gel electrolyte is crucial for the zinc ion battery system.Therefore,this paper explores the zinc ion battery gel electrolyte based on PVA system,and its main contents are as follows:1.Electrochemical and mechanical properties of ionic liquid EMIM TFSI doped gel electrolyte were studied.The electrochemical and mechanical properties of gel electrolytes with different EMIM TFSI contents were investigated.When the doping amount is appropriate,the electrochemical performance of gel electrolyte is significantly enhanced,and the mechanical properties are also improved.Due to the improvement of electrolyte performance,the Zn symmetrical batteries based on this shows a stable cycle of up to 4000 hours.In the meantime,the full cells with V2O5 cathode and Zn metal anode also achieved higher cycle specific capacity and better rate performance.This research provides a research strategy for future zinc ion batteries and other electrochemical energy storage systems that may use gel electrolyte.2.Synthesis of MXene based TiO2 nanosheets,electrochemical performance,mechanical properties and reaction mechanism of gel electrolytes with different TiO2 doping levels.TiO2 nanosheets have been successfully fabricated from the Ti3C2Tx MXene by a one-step hydrothermal reaction as additive for gel polymer electrolytes.The effects of synthesis conditions on composition and structure of the Ti3C2Tx MXene are explored.The obtained TiO2 nanosheets are applied as additives for PVA-based gel polymer electrolyte.The evolution of ionic conductivity and mechanical properties of the GPEs with different TiO2 additions have been probed.With excellent mechanical properties,high ionic conductivity and satisfying self-healing ability,PZ3T is used as the electrolyte for ZIBs.Remarkably,the growth of Zn dendrite is efficiently inhibited by PZ3T,Zn symmetric cell delivers a stable cycle life of more than 3000 h.Matched with V2O5 cathode and Zn metal anode,full cell with PZ3T shows an excellent Coulombic efficiency of 99.8%and a high charge capacity of 216 mAh g-1(after 115 cycles)with superior cycling performance.The above results demonstrate the potential and feasibility of the MXene-based TiO2 nanosheets based hybrid gel electrolyte for highly stable ZIBs.Moreover,the hybrid gel electrlyte presents potential applications in other power source systems such as Li/Na/K and supercapacitor,etc.