RESUMEN
Solid-state lithium metal batteries (SSLMBs) are attracting increasing attentions as one of the promising next-generation technologies due to their high-safety and high-energy density. Their practical application, however, is hindered by lithium dendrite growth and propagation in solid-state electrolytes (SSEs). Herein, an in situ grain boundary modification strategy relying on the reaction between Li2 TiO3 (LTO) and Ta-substituted garnet-type electrolyte (LLZT) is developed, which forms LaTiO3 along with lesser amounts of LTO/Li2 ZrO3 at the grain boundaries (GBs). The second phases of LTO/Li2 ZrO3 inhibit abnormal grain growth. The presence of LaTiO3 at the GBs reduces electronic conductivity and improves mechanical strength, which can hinder dendrite formation and block lithium dendrite penetration through the LLZT. Moreover, the adjacent grains by LaTiO3 build a continuous Li+ transport path, providing a homogeneous Li+ flux throughout the whole LLZT-4LTO. As a result, symmetric cells of Li | LLZT-4LTO | Li shows a high critical current density of 1.8 mA cm-2 and a long cycling stability up to 2000 h at 0.3 mA cm-2 . Moreover, the high-voltage full cells demonstrate remarkable cycling stability and rate performance. It is believed that this novel grain boundary modification strategy can shed light on the constructing of high-performance SSEs for practical SSLMBs.
RESUMEN
Li-garnet Li7La3Zr2O12 (LLZO) is a promising candidate of solid electrolytes for high-safety solid-state Li+ ion batteries. However, because of its high reactivity to water, the preparation of LLZO powders and ceramics is not easy for large-scale amounts. Herein, a method applying water-based solvent is proposed to demonstrate a possible solution. Ta-doped LLZO, that is, Li6.4La3Zr1.4Ta0.6O12 (LLZTO), and its LLZTO/MgO composite ceramics are made by attrition milling, followed by a spray-drying process using water-based slurries. The impacts of parameters of the method on the structure and properties of green and sintered pellets are studied. A relative density of â¼95%, a Li-ion conductivity of â¼3.5 × 10-4 S/cm, and uniform grain size LLZTO/MgO garnet composite ceramics are obtained with an attrition-milled LLZTO/MgO slurry that contains 40 wt % solids and 2 wt % polyvinyl alcohol binder. Li-sulfur batteries based on these ceramics are fabricated and work under 25 °C for 20 cycles with a Coulombic efficiency of 100%. This research demonstrates a promising mass production method for the preparation of Li-garnet ceramics.
