Preparation and Performance Study of Ga-Doped LLZTO Solid Electrolyte

石榴石型Li7La3Zr2O12 (LLZO)固态电解质凭借其宽电化学窗口和良好的热化学稳定性，成为储能器件领域的重要研究对象。目前该材料仍然面临两个关键难题，室温离子电导率较低制约了其产业化，较高的电极与电解质界面阻抗影响离子传输效率，现有研究主要通过掺杂改性和构建界面缓冲层等策略进行优化。本研究基于元素掺杂策略对LLZO进行改性，在LLZO体系中引入Ga、Ta元素，构成Ga元素掺杂的LLZTO石榴石固态电解质，重点探究其对材料离子传输效率与界面稳定性的协同提升机制。本研究采用Ga掺杂策略制备了Li6.5-3xGaxLa3Zr1.5Ta0.5O12 (x = 0、0.05、0.1、0.15)石榴石固态电解质，系统考察Ga元素掺杂含量对于LLZTO的影响。结果表明，Ga掺杂促使石榴石固态电解质从四方相向立方相转变，且当x = 0.1，Ga01LLZTO样品经1150℃烧结6 h后致密度达94.2%，离子电导率高达3.95 × 10−4 S·cm−1及1.2 mA·cm−2极限电流密度。基于此制备的锂对称电池在50℃下以0.15 mA·cm−2持续循环2000次无短路，磷酸铁锂全电池0.1 C倍率循环50次后容量保持率80.5% (库仑效率99.9%)，证实Ga掺杂的LLZTO由于有利于界面稳定性提升。Garnet Li7La3Zr2O12 (LLZO) solid electrolyte has become an important research object in the field of energy storage devices due to its wide electrochemical window and good thermal chemical stability. Currently, this material still faces two key challenges: the low room-temperature ionic conductivity restricts its industrialization, and the high electrode-electrolyte interface impedance affects the ionic transport efficiency. Existing research mainly optimizes through strategies such as grain boundary modification and construction of interface buffer layers. This study modifies LLZO based on the element doping strategy, introducing Ga and Ta elements into the LLZO system to form Ga-doped LLZTO garnet solid electrolyte, focusing on exploring the mechanism of its synergistic improvement of material ionic transport efficiency and interface stability. In this study, Ga-doped Li6.5-3xGaxLa3Zr1.5Ta0.5O12 (x = 0, 0.05, 0.1, 0.15) garnet solid electrolytes were prepared by a Ga doping strategy, and the effects of Ga doping content on LLZTO were systematically investigated. The results show that Ga doping promotes the transformation of the garnet solid electrolyte from the tetragonal phase to the cubic phase. When x = 0.1, the density of the Ga01LLZTO sample sintered at 1150˚C for 6 hours reaches 94.2%, with an ionic conductivity as high as 3.95 × 10−4 S·cm−1 and a limiting current density of 1.2 mA·cm−2. The lithium symmetric cells fabricated based on this material can be continuously cycled 2000 times at 0.15 mA·cm−2 without a short circuit at 50˚C. The capacity retention rate of the LiFePO4 full cell after 50 cycles at a 0.1C rate is 80.5% (Coulombic efficiency 99.9%), confirming that Ga-doped LLZTO is beneficial for improving the interface stability.