Preparation And Performance Study Of Solid Sodium Ion Battery Based On NASICON Solid Electrolyte

The growing demand for energy storage systems in many areas has spurred the development of rechargeable batteries other than lithium ion batteries?LIBs?,such as sodium ion batteries?SIBs?.Due to the abundant resources of sodium salts in the earth's crust and ocean,SIB is more suitable for large-scale energy storage systems.The traditional SIB uses an organic electrolyte,which is easy to cause safety problems such as leakage and flammability.In contrast,solid-state sodium batteries?SSSB?show greater potential for solving safety problems because they can utilize non-flammable solid electrolytes?SSE?,which can achieve higher safety and higher energy density.However,several challenges including low ionic conductivity,poor wettability,low stability/incompatibility between electrodes and electrolytes,may degrade performance and hinder the development of practical applications.Therefore,how to deal with the above challenges is the key point.In this paper,the NZSP solid electrolyte membrane was synthesized by casting method.The dispersant content?4-5 wt%?was determined by sedimentation experiment,and the binder?4-6 wt%?was adjusted by the crack generated by the blank.The plasticizer content?1-2 wt%?was determined by the density of the sintered body and the thermo gravimetric test to determine the heating rate?1 °C/min?and the row of rubber phase?room temperature-600 ??,and found the most excellent casting formulation and crafts.The NZSP solid electrolyte membrane has the following advantages:a.NZSP film shortens the sodium ion transport distance;b.NZSP film has an ionic conductivity of 1.65x10^-4 and 9.40x10^-4 Scm^-1 at room temperature and 80 ?,respectively;c.The film thickness can be designed by the casting method,and the three-dimensional pore structure can be designed to facilitate subsequent research.The interface modification was carried out by adding the interface wetting agent BMIPF₆.The first cycle discharge capacity of the solid NVP/IL+NZSP/Na?IL:0.5M NaClO₄/BMIPF₆?was 90.9 mAhg^-1,which reached 77.69%of the theoretical capacity.By circulating 70 cycles,the solid state battery was discharged at room temperature.By designing the three-dimensional double-layer?dense layer and porous layer?NZSP structure for interface modification,the positive electrode material was encapsulated in the porous layer,which reduces the separation caused by volume change,and the battery first discharge was achieved 21 mAhg^-1 at 70 ?.The NZSP-PVDF composite solid electrolyte membrane was synthesized by simple solution casting method,and the content of inorganic filler NZSP was changed to obtain a composite membrane with high ionic conductivity and good mechanical strength.The preferred content was PVDF-NaC104-25 wt%NZSP.The composite solid electrolyte membrane has certain flexibility and wettability,and good contact with the positive electrode material,which reduces the interface impedance.The electrochemical window can reach 5 V,and the first discharge capacity reaches 92.3 mAhg^-1 under 0.1C condition.After 100 cycles,the capacity retention is 95.12%,achieving better electrochemical performance.