Study On Solid Polymer Electrolyte Of PAN For Sodium(ion)battery

As is known to all,the sodium element is friendly to environment.The sodium?ion?battery has the advantages of low cost and abundant resources compared with the lithium ion battery.At present,sodium ion batteries mostly use flammable liquid electrolyte,which is not good for its application.Using solid electrolyte to replace organic electrolyte can effectively improve the safety of sodium ion battery.And metal sodium can be used to improve the energy density of battery greatly.Therefore,solid sodium battery has become one of the research hotspots in the field of energy storage.However,the development of solid-state sodium batteries has been greatly limited by the development of sodium electrolytes.Solid electrolyte of Sodium ion battery is mainly divided into organic and inorganic,inorganic electrolyte is generally high conductivity,but usually brittle and thick,poor processing,not suitable for application.Organic electrolyte of polymer is easy to process into film,and the interface resistance is low.It is suitable for applications in batteries.However,solid polymer electrolytes usually have low ionic conductivity and poor mechanical flexibility at room temperature.Therefore,the design and preparation of solid polymer electrolyte with high ionic conductivity and mechanical flexibility are crucial to the development of solid sodium batteries.In this paper,sodium ion solid polymer electrolyte with high ion conductivity and mechanical flexibility is prepared by electrostatic spinning.The effects of electrolyte salt concentration,polymer blending and inorganic phase doping in solid polymer electrolyte properties are investigated.The thesis mainly studies the following three aspects:First,PAN/sodium perchlorate?NaClO₄?solid polymer electrolyte is prepared by combining electrostatic spinning with cold pressing.It is found that PAN solid electrolyte films prepared by electrostatic spinning have low crystallinity and great mechanical flexibility,and the elongation rate is 115%.Under pressure of 3 mN,the probe is pressed to a depth of 1560 nm.We found that the ionic conductivity of PAN/NaClO₄ solid polymer electrolyte prepared by electrostatic spinning increased first and then decreased with the concentration of sodium salt(NaClO₄/ethylene glycol dimethyl ether?DME?.When the sodium concentration is 2 mol,the ionic conductivity of PAN/NaClO₄ solid polymer electrolyte at room temperature reaches the highest value of 2.24×10^-4 S cm^-1.Secondly,polyvinylidene fluoride?PVDF?is mixed with PAN,then PAN&PVDF/NaClO₄ solid polymer electrolyte is prepared by combining electrostatic spinning with cold pressing.It is found that the introduction of PVDF effectively improved the tensile and elastic properties of solid polymer electrolyte.When mass ratio of PAN and PVDF is 1:3,the tensile elongation rate and mechanical strength of PAN&PVDF/NaClO₄ solid polymer electrolyte are 180%and 28 Mpa,56%higher than PAN/NaClO₄.Under the pressure of 3 mN,the depth of the probe is 3375 nm,which is 2.16 times that of PAN/NaClO₄.When the concentration of NaClO₄/DME is1.5 mol,the ionic conductivity of PAN&PVDF/NaClO₄ solid polymer electrolyte could reach 1.29×10^-4 S cm^-1.Finally,this work found that the introduction of carbon quantum dots?CQDs?into the PAN&PVDF solid polymer electrolyte can effectively reduce the crystallinity of the polymer and improve the ion transport rate of electrolyte.When the content of CQDs is 2 wt%,the ionic conductivity of PAN&PVDF/CQDs electrolyte is 6.8×10^-55 S cm^-1.The hardness of the solid polymer electrolyte is 0.037 Gpa,and the depth of the probe under the pressure of 2 mN is 2206 nm.