Synthesis And Modification Of Lithium Superionic Conductors Of Lithium Silicate Ramification And NASICON Type And Study On Property

Lithium inorganic solid electrolytes include lithium polymer ones and lithium inorganic ones, Because the preparation conditions are very rigorous, the systems are complicated, the influence factors the electrical property are numerous, etc. The studying progress of lithium inorganic ones is slower. Lithium silicate and its ramification solid electrolytes and NASICON solid electrolytes were specially studied in this dissertation for the relation of preparation and property of lithium fast ion conductors at present.This dissertation deals with the synthesis and characterization of Li₄SiO₄-based and LiTi₂(PO₄)₃-based new lithium fast ion conductors prepared by high temperature solid state reaction using refined nature coal gangue as a starting part material. They are Li₈Al_1-xSi_2xP_1-xO₈ andLi_1+2x+2yAl_xMg_yTi_2-x-ySi_xP_3-xO₁₂(Li_1.4Al_0.1Mg_0.1Ti_1.8Si_0.1P_2.9O₁₂(shortened formTM1)and Li_1.8Al_0.1Mg_0.3Ti_1.6Si_0.1P_2.9O₁₂(shortened form TM2)). Some perfect reaction conditions were discovered, and many measuring methods were used. For example, X-ray powder diffraction, A. C. impedance, FT-IR and SEM, etc.Lithium silicate has poor lithium ions and low conductivity, its conductivity is only 2.4 × 10^-10 S · cm^-1 at 298K, 2.5 × 10^-5 S · cm^-1 at 573K. But its conductivities may improve when adulterating different ions for producing moving ions and cavities. Chapter two deals with the synthesis and characterization of Li₄SiO₄-based new superionic conductors (Li₈Al_1-xSi_2xP_1-xO₈(x=0.1⁰.9)) prepared by high temperature solid statereaction using refined nature coal gangue as a starting part material. X-ray diffraction analysis indicated that a single solid solution phase with the P2i/m space group was formed in the composition range of 0.54 S ? cm"1 at room temperature , while at 673K the composition with x = 0. 1 y = 0. 3 possesses the best ionic conductivity of 2.93 X 10"2 S ? cm"1.LigAl^xSi^Pi.xOg and Lii+2x+2yAlxMgyTi2.x.ySixP3.xOi2 systems prepared using refined nature coal gangue as a starting part material were compared with the two ones prepared using analytical material, we found they were same in structure and similar in electrical property.Chapter four based Chapter three, Pure analytic reagent has been used for preparing new lithium superionic conductors (TMland TM2)system at high temperature (850 °C, 900 "C, 950 °C) solid phase reaction .The ionic conductivities of TM1 and TM2 were measured by AC impedance method at 298K.The conductivities of TM1 synthesized at 850 °C,900 °C and 950 °C were 1.05XI0"4S -cm"1, 1.11 X 10"4 S -cm"1, 1.31X10"4 S-aiT1;theones ofTM2 were7.41 XI0'5S -cm'1, 7.81X10"5 S-cm"1, 8.11 X 10"5 S'cm"1.The data indicated the conductivities of TMland TM2 raised with the reaction temperature. The conductivities measured at 373K,473K,573K and 673K had the same trend, we found the conductivities of the conductors synthesized at 950 °C are the highest, while the ones of the materials synthesized at 850 °C are the lowest. The temperature of 950 °C is the fit reaction one for preparing TMland TM2. 7^ 100 °C ,the conductivities of TM2 are bigger than the ones of TM1. X-ray powder diffraction showed that a Lisicon phase withR3c space group exists the conductors which were prepared at different high temperature.