Enhanced Performance of Li_6.4La₃Zr_1.4Ta_0.6O₁₂ Solid Electrolyte by the Regulation of Grain and Grain Boundary Phases

Abstract

The application of Li-ion conducting garnet electrolytes is challenged by their large interfacial resistance with the metallic lithium anode and the relative small critical current density at which the lithium dendrites short-circuit the battery. Both of these challenges are closely related to the morphology and the structure of the garnet membranes. Here, we prepared four polycrystalline garnet Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 (LLZTO) pellets with different particle sizes (nano/micro) and grain boundary additive (with/without Al 2 O 3 ) to investigate the influence of grain size, the composition of the grain boundary, and the mechanical strength of the pellet on the total Li-ion conduction of the pellet, Li/garnet interfacial transfer, and lithium dendrite growth in all-solid-state Limetal cells. The results showed that the garnet pellets prepared with nanoparticles and LiAlO 2 -related grain boundary phase had decreased total Li-ion conductivity because of the increased resistance of the grain boundary; however, these pellets showed higher mechanical strength and improved capability to suppress lithium dendrite growth at high current densities. By controlling the grain size and optimizing the grain boundary with Al 2 O 3 sintering additive, the hot-pressing sintered LLZTO solid electrolytes can reach up to 1.01 × 10 −3 S cm −1 in Li + conductivity and 0.29 eV in activation energy. LLZTO with nanosized grain and LiAlO 2 -modified grain boundary showed the highest critical current density, which is 0.6 mA cm −2 at room temperature and 1.7 mA cm −2 at 60 °C. This study offers a useful guideline for preparing a high-performance LLZTO solid electrolyte.

The Influence of Surface Chemistry on Critical Current Density for Garnet Electrolyte

“…The LLZO slab was constructed based on the cubic polymorph with partial occupancies of 0.542 and 0.448 on the 24 day and 96 h Li-sublattice sites, respectively. These occupancies are similar to the experimental values of 0.564 (12) and 0.442(3) for these sites, respectively. [42] The interfaces between Li 2 CO 3 (001), LLZO (001), Au (111), ZnO (1120), MoS 2 (0001), Al 2 O 3 (0001), and Li (001) were constructed from the low-energy surfaces.…”

“…[5][6][7][8] However, the high electrode-electrolyte interfacial impedance and the attendant low critical current density (CCD) have severely hindered the development of solid-state batteries (SSBs). [9][10][11][12] Lithiophobic Li 2 CO 3 impurity can form on the surface of LLZO pellet when stored in the air, which was found to be the origin of the sluggish Li-ion transport. [13] Therefore, polishing or acid treatment has been used to remove the Li 2 CO 3 layer.…”

Interphase Formed at Li6.4La3Zr1.4Ta0.6O12/Li Interface Enables Cycle Stability for Solid‐State Batteries

“…Next, calcination of the cold-pressed pellets was performed at 1200 °C for 10 h with a temperature ramp-up rate of 5 °C min -1 . The LLZTaO sample shows high purity; all the diffraction peaks can be indexed to a cubic garnet structure (PDF #40-0894), [29] as shown in the XRD pattern (Figure S8, Supporting Information). LLZTaO pellets, with a relative density of about 99.3%, were obtained after the abovementioned treatments.…”

Influence of P and Ti on Phase Formation at Solidification of Synthetic Slag Containing Li, Zr, La, and Ta

“…The incorporation of Li into perovskite, zirconate, and pyrochlore, or the formation of complex oxides with Li, Ca, Ti, Zr, and La, are plausible because all of the elements except for Ca can form Li compounds (titanate, zirconate, lanthanate). Garnets of the type of Li x La 3 Zr y Ta z O 12 are used as the solid-state electrolyte (Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 , e.g., [55]). The same applies to perovskite (CaTiO 3 )-based compounds, such as Li x La y TiO 3 , as is reported by Li et al (Li 0.33 La 0.557 TiO 3 , [56]).…”