Preparation Of Polymer Electrolyte With High Sodium Ion Conductivity And Study On Its Performance For Sodium Metal Full Battery

The battery assembled with organic electrolyte and sodium metal process the issue that the sodium metal decomposes the electrolyte,the SEI film on the surface of sodium metal is unstable,and the sodium dendrite penetrates the separator.At present,the solution to the above problems is mainly to construct a protective layer on the surface of sodium metal and modify electrolyte.Nevertheless,the protective layer constructed on the surface of sodium metal hinders ion transmission and increases the interface resistance,which is not conducive to the occurrence of electrochemical reactions.Considering the above factors,we focuses on the preparation of polymer electrolyte with excellent performance to inhibit the growth of sodium dendrite.Meanwhile,a high-mass specific capacity and excellent cycle stability cathode and sodium metal anode were matched and assembled into a full battery to apply for high energy density.The details are as follows:(1)Gel electrolyte membrane(GPH)was prepared by using graphene oxide(GO)as polymer matrix filler of polyvinylidene fluoride-hexafluoropropylene(PVDF-HFP).When the ratio of GO is 2wt%,the compressed Young's modulus of the gel electrolyte membrane(2-GPH)can be increased by 10 times(2.5 GPa).The results show that the growth of sodium dendrite can be effectively suppressed.(2)Modified PEO polymer electrolyte using NASICON-like Na3Zr2SiP2O12 nanoparticles as fillers,and discussed the effect of different introduction amounts on ionic conductivity.When the introduction amount is 45%,the highest conductivity is 1.4 × 10-4 S cm-1 and the decomposition voltage is widened to 4.45 V.Meanwhile,the interface stability with sodium metal is improved,and the interface resistance is reduced by two times.(3)Solid electrolyte possess better performance than gel electrolyte in preventing liquid leakage.Polyethylene glycol acrylate(PEGDA)was used as monomer to polymerize into polymer electrolyte(IPE)directly in glass fiber membrane under the action of thermal initiator 2,2-azodiisobutyronitrile(AIBN).The ionic conductivity of IPE is 0.8 × 10-3 S cm-1 and 4.5 × 10-3 S cm-1 at 20? and 60?,respectively(4)By embedding Na3V2(PO4)3(NVP)nanoparticles on ZIF-67 derived carbon,NVP cathode with good cycle and high capacity retention rate was prepared.Subsequently,sodium metal battery assembled with the NVP cathode,the sodium metal anode,and polymer electrolyte produces excellent electrical performance.After 1000 cycles of Na/GPH/NVP battery at 1 C(1C=117 mA g-1),the capacity retention rate reached 93.5%.At room temperature,the capacity of Na/NZSP-CPE/NVP full battery is stable at 100 mAh g-1 after 100 cycles at 0.1C.At 50?,the capacity retention rate of Na/IPE/NVP polymer solid-state battery is 91.4%and the coulombic efficiency is close to 99%after 1100 cycles at the rate of 0.3 C.