Preparation Of Lilanthanum Zirconium Oxideceramic Nanofiber Membrane And Its Application In Solid-state Lithium Batteries

In view of the fact that traditional liquid lithium batteries can no longer meet the requirements of the current market for energy storage systems,all-solid-state lithium metal batteries have been favored by scholars due to their advantages of safety,stability and high specific capacity.However,single organic and inorganic solid electrolytes have certain limitations,so the combination of the two has become a research hotspot.At present,the method of preparing organic/inorganic composite electrolyte by filling inorganic ceramic nanoparticles is easy to cause agglomeration of nanoparticles and affect the continuous conduction of Lithium ion（Li⁺）.On the other hand,the free movement of anions in the polymer matrix leads to serious concentration polarization of electrolyte in the battery charging and discharging process,which leads to the obstruction of Li⁺transmission at the interface between electrolyte and electrode.In addition,the accumulation of Li⁺at the interface induces the growth of lithium dendrites,which limits the long cycle stability of the battery.Previous studies have demonstrated that when the content of ceramic filler in the composite electrolyte is high,the transport of Li⁺is dominated by the ceramic part,and the electrochemical performance of the composite electrolyte is closely related to the structure of the ceramic part.However,during long-term charge-discharge cycles,when the mechanical properties of the composite electrolyte formed by inorganic fillers and polymers are insufficient,the growth of lithium dendrites cannot be suppressed,resulting in anode passivation and ultimately affecting battery life.Therefore,regulating the structure of the ceramic part and the Li metal anode interface is an important means to construct the uniform distribution and conduction of Li⁺in the electrolyte and suppress the growth of Li dendrites.In this paper,a Li_6.25La3Al_0.25Zr₂O₁₂（LLZAO）ceramic nanofiber electrolyte membrane with good room temperature stability and high ionic conductivity was prepared by electrospinning by means of aluminum（Al）element doping,and used as a three-dimensional（3D）composite electrolyte.3D network framework into which LLZAO-PEO-Li TFSI composite electrolytes were prepared by casting polyethylene oxide（PEO）and bis-trifluoromethanesulfonimide（Li TFSI）,and its electrochemical properties were systematically studied.Doping with Al element during the spinning process is beneficial to smooth the crystal interface,reduce the interface impedance and stabilize its structure.The prepared highly oriented LLZAO ceramic nano-3D structure provides a fast,continuous and uniform Li⁺transport path for the composite electrolyte,avoiding the occurrence of particle agglomeration in the traditional preparation method.And the ionic conductivity at 50°C is as high as 1.24×10^-3S/cm,the electrochemical stability window is significantly broadened（5 V vs Li/Li⁺）,the lithiumion migration number(t _Li+=0.631)is significantly improved compared to PEO-Li TFSI polymer electrolyte(t _Li+=0.235),the mechanical properties are also improved.The strength can reach about 6 MPa.In addition,although the interface contact between composite electrolyte and lithium metal anode is improved compared with inorganic solid electrolyte,there are still gaps between the solid-solid interface.In view of the above two problems,this paper coats the Ga-Sn-In mixed liquid metal on the surface of the lithium metal negative electrode to form a solid-liquid interface with the electrolyte,which further improves the interfacial contact between the electrolyte and the metal lithium negative electrode.Moreover,the modified Li anode significantly reduces the nucleation barrier of Li,making Li deposition uniform,and the assembled modified Li|LLZAO-PEO-Li TFSI|modified Li symmetric battery can cycle stably at a current density of 0.2 m A/cm~2 at 1200 h and 50 ℃.