| Solid electrolytes have become the focus of rechargeable battery research field because of their high energy density and high safety.Polymer electrolytes have attracted more and more attention because of their good mechanical properties and flexibility,and they usually have better interface compatibility with solid electrodes,which can effectively reduce the interface resistance.However,most polymer electrolytes usually have some defects,such as poor electrochemical performance at room temperature and narrow electrochemical window.Succinonitrile has good ionic conductivity,good thermal stability and high oxidation stability,which has been widely concerned by researchers.Based on this,the research of gel polymer electrolyte based on SN is carried out in this paper.The details are as follows:firstly,the influence of SN addition on the ionic conductivity and cycle performance of the polymer electrolyte is studied by UV curing in situ polymerization,and on the basis of which,the effect of the addition of on the ionic conductivity and cycle performance of the polymer electrolyte is studied.A double-layer electrolyte material is constructed to enhance the interfacial stability of SN polymer gel electrolyte.In addition,considering that different polymer matrix has different effects on the electrochemical performance of the battery,a series of electrochemical performances such as ionic conductivity of different polymer electrolytes added with SN electrolyte are compared.Finally,the best polymer matrix is selected to prepare the lithium battery with excellent performance.1.The PEGDA-Li TFSI-SN gel electrolyte based on SN is prepared by UV curing in situ polymerization firstly.The glass fiber,which is used as an electrolyte skeleton,is completely immersed in the electrolyte precursor and penetrated for 2 hours under negative pressure,so that the glass fiber was completely saturated;,and then the glass fiber used as electrolyte skeleton is completely immersed into the electrolyte;Finally,UV curing for 5 minutes,resulting in gel electrolyte,the ionic conductivity of the electrolyte reached 6.56×10-4 S cm-1;Furthermore,in order to improve the stability of the electrolyte to lithium,the PEO slurry was mixed and stirred,then the coating was dried,and the thickness of 10?m.So the strategy of double-layer electrolyte is realized.The ionic conductivity of the composite polymer electrolyte can reach 4.27×10-4 S cm-1 at room temperature,and the range of electrochemical window is 5.1 V(relative to Li+/Li).The lithium metal symmetrical battery has no short circuit phenomenon after cycling for more than 250 hours.The discharge capacity of the Li Fe PO4//Li battery is168 m Ah g-1 at 0.2 C.2.In order to further study the influence of polymer matrix on the electrochemical performance of gel polymer electrolyte,the representative chitosan alginate,PVDF-HFP and bacterial septum are selected as the representative,and the electrochemical properties are compared with the succinonitrile based electrolyte(SN-Li TFSI-Li DFOB).Succinonitrile based chitosan alginate gel electrolyte is prepared.Due to the existence of ionic crosslinking,the two polymers of sodium alginate and chitosan is blending in the process of spontaneous formation of polyionic complexes,which improves the thermal stability and structural strength of the polymer.The gel electrolyte can not only maintain the electrochemical properties of the electrolyte,but also be used as a diaphragm to prevent internal short circuit and meet the requirements of flexible battery.Finally,the ionic conductivity of the chitosan alginate gel electrolyte which infiltrates SN-Li TFSI electrolyte reaches 1.7×10-3 S cm-1.The succinonitrile based PVDF-HFP gel electrolyte is prepared.It has 3D porous network and excellent flexibility.The PVDF-HFP gel electrolyte immersed in SN-Li TFSI-Li DFOB-10V%FEC electrolyte and SN-Li TFSI-Li DFOB-1wt%Li NO3 electrolyte exhibit good stability for lithium metal and the ionic conductivity arrive at 3.21×10-4 S cm-1.Bacterial cellulose has unique and complex 3D porous network structure,which can provide large surface area,abundant porosity and high mechanical properties.These characteristics are conducive to gelation process,and also ensure the absorption of electrolyte and provide extensive ion channels.Abundant-OH and EO groups can interact with lithium ions strongly.The ionic conductivity of the bacterial silk gel immersed in SN-Li TFSI-Li DFOB-1wt%Li NO3 electrolyte arrive at 3.18×10-3 S cm-1,and the lithium metal batteries based on BC-GPE also exhibit excellent electrochemical performance.In order to improve the stability of the electrolyte to lithium,the lithium sheet passivated by FEC was used as the anode.The batteries show excellent cycle performance and rate performance. |
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