Effect of Sintering Additives on Relative Density and Li‐ion Conductivity of Nb‐Doped Li₇La₃ZrO₁₂ Solid Electrolyte

Abstract

Lithium ion conductors with garnet‐type structure are promising candidates for applications in all solid‐state lithium ion batteries, because these materials present a high chemical stability against Li metal and a rather high Li+ conductivity (10−3–10−4 S/cm). Producing densified Li‐ion conductors by lowering sintering temperature is an important issue, which can achieve high Li conductivity in garnet oxide by preventing the evaporation of lithium and a good Li‐ion conduction in grain boundary between garnet oxides. In this study, we concentrate on the use of sintering additives to enhance densification and microstructure of Li7La3ZrNbO12 at sintering temperature of 900°C. Glasses in the LiO2‐B2O3‐SiO2‐CaO‐Al2O3 (LBSCA) and BaO‐B2O3‐SiO2‐CaO‐Al2O3 (BBSCA) system with low softening temperature (<700°C) were used to modify the grain‐boundary resistance during sintering process. Lithium compounds with low melting point (<850°C) such as LiF, Li2CO3, and LiOH were also studied to improve the rearrangement of grains during the initial and middle stages of sintering. Among these sintering additives, LBSCA and BBSCA were proved to be better sintering additives at reducing the porosity of the pellets and improving connectivity between the grains. Glass additives produced relative densities of 85–92%, whereas those of lithium compounds were 62–77%. Li7La3ZrNbO12 sintered with 4 wt% of LBSCA at 900°C for 10 h achieved a rather high relative density of 85% and total Li‐ion conductivity of 0.8 × 10−4 S/cm at room temperature (30°C).

Impedance Spectroscopy Screening of Various Nanocrystalline Metal Oxides: Effect of Lithiation on Electrical Properties

“…Typical solid electrolytes for Li‐Ion battery applications include garnet‐structured materials such as LiLaZrO 2 as well as sulfides. UCT materials exhibit very low ionic conductivity compared to literature, with some literature examples reaching 10 −4 /10 −3 S cm −1 . The low conductivity of 10 −6 S cm −1 is likely due to the high concentration of grain boundaries in nanocrystalline materials.…”

“…Ty pical solid electrolytes for Li-Ion battery applications include garnet-structured materials such as LiLaZrO 2 as well as sulfides.U CT materials exhibit very low ionic conductivity compared to literature, [19,26] with some literature examples reaching 10 À4 /10 À3 Scm À1 .T he low conductivityo f1 0 À6 Scm À1 is likely due to the high concentrationo fg rain boundaries in nanocrystalline materials.A lthough beneficial for minimizing electronic conductivity, this characteristic of the materials negatively impacts the ionic conductivityc ompared to these other systems.…”

“…These electrolytes must transport lithium ions through the medium with high ionic conductivity; however, further development is needed to improve the mobility to reach levels comparable with liquid electrolytes . Currently, garnet LiLaZrO 2 (LLZO) and sulfide electrolyte materials are popular candidates . Properties including morphology, crystallinity, grain size, grain boundaries, and porosity play a significant role in dictating the performance of ionic systems .…”

“…[17,18] Currently,g arnet LiLaZrO 2 (LLZO)a nd sulfide electrolyte materials are popular candidates. [19,20] Properties including morphology,crystallinity,grain size,grain boundaries, and porosity play as ignificant role in dictating the performance of ionic systems. [21] To this end, we selected as eries of first-row transition metal oxides (Mn, Fe,C o, Ni)s ynthesized through an evaporative-induced self-assembly method, which gives rise to nanostructured particles with regular porosity and crystallinity, [22] and chemically lithiated them using as imple method.…”

Submicron Sized Nb Doped Lithium Garnet for High Ionic Conductivity Solid Electrolyte and Performance of All Solid-State Lithium Battery

“…Many solutions had adopted to solve above issues. For example, doping Al, Ga, Fe, Ta, Nb, W, Y, Sb to stabilize the cubic phase; [18][19][20][21][22][23][24][25] Adopting hot pressing sintering, plasma sintering and microwave sintering to increase the relative density and sintering additives [26][27][28]; Investigating Y2O3, Al2O3, B2O3, CaO, MgO, Li3PO4 and Li4SiO4 to reduce the grain boundary resistance [29][30][31][32][33][34][35].…”