| Lithium-ion batteries are widely used in electronics and energy storage devices.With the ascension of human needs and the advancement of technology,the application of lithium ion secondary battery also enlarged toward miniaturization and flexible development,gradually widely used in large storage power station,new energy electric vehicles and flexible skin New demand bring new performance requirement,especially the safety and energy density,etc.Then developed solid-state lithium secondary battery is the development direction of the next generation of lithium batteries a solid electrolyte,which is the core of the solid-state batteries,is the key to a new generation of lithium batteries.Li7La3Zr2O12?LLZO?solid electrolyte with high ionic conductivity at room temperature,chemical stability and thermal stability,which greatly improves the garnet in solid-state electrolyte battery application prospect.However,its conductivity is still relatively low compared with the traditional liquid electrolyte.How to improve the conductivity is the key to the application of LLZO solid electrolyteIn this paper,with element doping as the starting point,the process and mechanism of LLZO doping were explored.First,the adaptability of undoped LLZO process parameters was explored.The pre-pressing process obtained well-formed electrolyte pieces,and the sintering process obtained electrolyte pieces with good performance.The crucible size on the influence of precursor sintering was also explored,precursor XRD phase analysis found that small pot reduce the volatilization of lithium volatiles to a certain extent.With the optimization of sintering process,six groups of different Fe element doping amount of LLZO precursor and ceramic electrolyte was prepared.Precursor of XRD phase analysis results show that the Fe element doping can get room temperature stability of the cubic phase LLZO,one of the Fe = 0.30 LLZO obtained the optimal doping effect.In the fracture analysis of the electrolyte piece,the double-layer coating structure was found,which guaranteed the stability of the inner lithium element and provided a new idea for the control of lithium volatilization.On the basis of single-element doping process,in order to explore the double-element co-doping of LLZO,Fe?Ta double-element was selected to carry out exploration test on the Li?Zr co-doping of LLZO.The XRD phase analysis of the doped precursor shows that LLZO is stable at room temperature under the double-element doping system,and the doping effect is better than that of Fe single-doping.In order to explain LLZO mechanism under different Fe doping and predict its electrical performance,four doping contents Fe=0.1,0.2,0.3 and 0.4 were selected for molecular dynamics calculation based on LAMMPS.A suitable force field was selected to optimize LLZO under the doping concentration of four Fe elements.On the basis of optimization,molecular dynamics simulation of 2000 ps was carried out.By analyzing cell parameters and element radial distribution function,it is found that compared with other Li-bit doped elements Al and Ga,Fe has a larger atomic radius,which reduces the influence of lattice distortion and is a favorable condition for obtaining a higher conductivity.The results of molecular dynamics show that when Fe= 0.3,the best average azimuth-shifting parameter is obtained,and the calculated conductivity reaches 10-3 S·cm-1. |
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