Microwave Sintered Cubic Si-Doped Li7La3Zr2O12 with Improved Li-Ion Conductivity and High Density

Abstract

Microwave Sintered Cubic Si-Doped Li7La3Zr2O12 with Improved Li-Ion Conductivity and High Density XU Ding-hao, WU Yong-min, TIAN Wen-sheng, TANG Wei-ping (Shanghai Institute of Space Power-Sources, Shanghai 200245, China) High energy density and high security batteries have been widely used in intelligent has been widely used in intelligent devices and power and energy areas. With significant advantages on the specific energy and safety by using a solid electrolyte, all solid state lithium batteries are the future direction of development. Among all solid electrolytes which are suitable for all solid state lithium battery, Li7La3Zr2O12(LLZO) with its high theoretical density, small grain boundary impedance and low interfacial reaction dendrite probability has become an extremely promising material. In order to obtain a high density of Li7La3Zr2O12, calcinations is the primarily preparation method. The sintering temperature is higher than 1200℃ and sintering time is more than 30 hours. The calcinations can be repeated to reduce porosity. At the same time, in order to improve the ion conductivity of the interface and reduce grain boundary surface of the lithium-ion overflow barrier, it generally doped zirconium-bit or lanthanum-bit types of metal elements such as Ta, Nb, Hf, Al, etc, so as to reduce the structural barriers and improve ion transmission capacity. Microwave reaction is particularly suitable for the manufacture of high density material because of its high efficiency high heating rate and high reaction uniformity. Therefore, we chose to use the microwave sintering method, the auxiliary powder tab letting process, at a temperature of 900℃ and no more than 12 hours, to obtain high purity cubic Li7La3Zr2O12. This method greatly improves the efficiency of the reaction. At the same time, an amount of Al, Si oxide is adding to the powder through ball mill. These oxides adjust the microwave absorption rate of each micro region, thereby improving reaction uniformity. On the basis of improve the density of the solid electrolyte film, doping at the A-bit and C-bit can increase lattice size, improve cell symmetry, increase vacancy concentration and improve lithium ion transport kinetics rate of the solid electrolyte. The results show that the doped Li7La3Zr2O12 prepared by microwave method oxygen, its room temperature ionic conductivity is about 0.7ms/cm. this method with advantages of low energy consumption, high reaction efficiency can not only promote the all solid-state lithium battery technology, but also be applied to the preparation of Li1.4Al0.4Ti1.6(PO4)3, Li10GeP2S12 and other types of solid electrolyte so as to broaden the research and development ideas of the solid electrolyte material.