Design, Synthesis, Crystal Structure And Performance Optimization Of New Li Ionic Electrolyte Materials

Compared with liquid electrolytes,all-solid electrolyte materials have obvious advantages in safety,stability and ease of design of assembled batteries,and they have good enough application prospects in the field of high safety chemical power supply.In fact,all-solid state（ASS）ion batteries are fully integrated into our life due to their high mechanical strength and safety,high energy and volume density,long cycle life and other performance advantages,such as portable electronic devices,notebooks,smartphones,electric/hybrid electric vehicles,fixed energy storage systems,etc.This paper is mainly devoted to finding solid electrolytes with good conductive properties at low and medium temperatures,then designing and synthesized a series of defective solid solutions.On the one hand,this paper is to improve the structural stability and circulation performance of the materials by modifiing（doping subseed,changing synthesis methods,etc.）on the existing glass ceramic mother-to-female compound.On the other hand,the new oxides with ion conductivity response at medium and low temperatures are discovered,and synthetic solid solutions are designed according to their ion radius and distribution environment in crystals to enhance electrochemical properties.1.By doping Sb⁵⁺at the Sn⁴⁺position in the oxide Li₂Sn O₃,which is a Na Cl layered structure,the series Li_3-x(Li Sn_2-xSb_x)O₆（x=0.2,0.4,0.6,0.8）solid solution is formed,and through doping high-priced Sb⁵⁺to add to the lithium vacancies in the structure and increase the disorder of the lithium metal layer（Li/Sn）,that reduces the bottleneck of the lithium migration path,and finds its upper doping limit and optimal doping concentration to improve ion conductivity.The experimental results show that the electrochemical performance increases obviously with the increase of lithium vacancies.The highest is the sample is x=0.8,the conductivity of the grain and boundaries at 250°C can reach 10^-3 S/cm,and its conductivity is two orders of magnitude higher in the medium and low temperature region than the Li₂Sn O₃ parent sample.And in the conductive literature report at low temperature,the optimization of doped solid oxides such as Li_1.8Mg_0.1Sn O₃,Li_2.2Mg_0.1Sn_0.9O₃are 1 orders of magnitude lower.At the same time,we also synthesized Li_3-x(Sn_2-xAl_xLi)O₆ samples to construct interstitial lithium conduction,although it also showed ion conductivity response,but the doping upper limit only reached Al=0.2.2.A series of Ca_1-xNa_2xAl₂B₂O₇（x=0.2,0.4,0.6,0.8,1.0）and Ca_1-xLi_2xAl₂B₂O₇（x=0.1,0.2,0.3,0.4）solid solutions were synthesized respectively,Through them,the Li-doped series of solid solutions exhibited ionic conductance response at lower temperatures.With the increase of Li concentration,the electrical conductivity shows a trend of first increasing,tending to saturation and then gradually decreasing,which is mainly due to the high Li⁺concentration blocking the three-dimensional migration channel of Li⁺migration.The optimal doping concentration is x=0.3 and this shows that proper doping can improve electrochemical performance.However,all the pure phase oxide samples doped with Na have no conductivity response.We attribute it to the low two-dimensional packing density of Ca_1-xNa_2xAl₂B₂O₇.3.A new oxide Li₉La Te₂O₁₂ with Li ion conductivity was found and an ion conductivity response was shown at lower temperatures.Although the attempt to dop Mg in Li position failed,they contributed to subsequent studies.