Synthesis Of Nitrogen-doped Oxide Solid Electrolyte And Its Modification Of Separator

With advances in microelectronic devices and implantable small armamentarium,the need for high-performance all-solid-state batteries（ASSBs）has grown considerably.A solid electrolyte with high ionic conductivity and low electronic conductivity is the key component of ASSBs.So far,LiPON is the solid electrolyte used in almost all commercial thin-film battery products.However,the lower ion conductivity of LiPON limits its application in more application scenarios.Therefore,new LiPON-based materials are expected to exhibit higher ionic conductivity while inheriting their excellent electrolyte performance.This study aims to develop a novel N-doped solid electrolyte material and study the effect of N doping on its conduction mechanism.Furthermore,to meet the requirements of power batteries with high specific energy storage,a solid-liquid proposed electrolyte system was proposed in this study,which consist of liquid electrolyte and LiPON/PP/LiPON.The system benefits from the superior interfacial performance of the composite solid electrolyte and exploits the advantages of the liquid electrolyte in bulk phase conduction to solve the interfacial issues of high-capacity arising from the use of the lithium anode.The main objectives and novelty of this study are as follows:（1）N was successfully introduced into LiAl O₂ via reactive sputtering under a N₂atmosphere,and LiAl ON solid electrolyte thin films were successfully prepared.The factors affecting the ionic conductivity of LiAl ON thin-film solid electrolytes under different preparation processes were studied.The results showed that the N-doped LiAl O₂（LiAl ON）thin-film electrolytes prepared at different sputtering powers and pressures are amorphous and compact films without pinhole cracks.The optimum preparation process parameters were a pressure of 2 Pa,power of 120 W,and gas flow of 50 sccm.The LiAl ON thin-film solid electrolyte prepared under these conditions exhibited the highest ionic conductivity(up to 3.99×10^-6 S/cm at room temperature).Doped N forms a triple coordination site（-N<）in the thin-film structure,which is responsible for ionic conductivity improvement.On the one hand,the triply coordinated N facilitates the formation of a crosslinked network and provides continuous pathways for Li⁺transport.On the other hand,the triply coordinated N which is less electronegative than O can provide a weak hopping sites for Li⁺.（2）The N-doped oxide solid electrolyte,LiPON was deposited on the surface of the PP separator,combined with a liquid electrolyte separator to form a composite solid-liquid proposed electrolyte system.Benefiting from the superior interfacial properties of the composite solid electrolyte and exploiting the advantages of the liquid electrolyte in volume phase conduction,a mechanically and chemically stable interface between the composite electrolyte and the lithium metal anode was constructed.This system can effectively solve the interface problems such as the growth of lithium dendrite,the generation of"dead lithium",and the adverse reaction between the lithium electrode and electrolyte;thus,its practical applicability was confirmed.Moreover,stable deposition and stripping of lithium at a high rate（5 m A/cm²）over 2000 h were achieved in a Li-symmetric battery using the proposed composite electrolyte system.The average Coulombic efficiency of Li|Cu cells over 200 cycles was up to 98%.The Li|LFP battery capacity retention rate was as high as 92.3%after 550 cycles（130 m Ah/g）,and Coulombic efficiency was always stable in the process of circulation at levels close to100%.Finally,more researchs on the conduction mechanism of amorphous solid electrolyte should be operated.Based on the preparation and research of LiAl ON,the new solid electrolyte of nitrogen doped oxide should be further developed.More researchs on the application of composite electrolyte system in real estate industry should be carried out.