Reactive sintering of garnet-type Li6.4La3Zr1.4Ta0.6O12 (LLZTO) from pyrochlore precursors prepared using a non-aqueous sol–gel method

Robust and Manufacturable Lithium Lanthanum Titanate-Based Solid-State Electrolyte Thin Films Deposited in Open Air

“…The complementary Bode plot shows two plateaus, which correspond to the bulk and grain boundary semicircles seen in the Nyquist plot. An equivalent circuit also shown in Figure a was used to fit impedance semicircles in low, medium, and high frequency ranges to extract the bulk and grain boundary impedances and to estimate electrode contact resistance. ,− Li + transport and conduction through grain boundaries and thin-film bulk are characterized by the ionic conductivities calculated according to eqs – film 0.25em ionic 0.25em conductivity 0.25em ( S cm ) , σ ion − film = l 0.25em ( cm ) R total 0.25em ( Ω ) × A 0.25em ( cm 2 ) bulk 0.25em ionic 0.25em conductivity 0.25em ( S cm ) , σ ion − bulk = l 0.25em ( cm ) R bulk 0.25em ( Ω ) × A 0.25em ( cm 2 ) grain 0.25em...…”

“…The complementary Bode plot shows two plateaus, which correspond to the bulk and grain boundary semicircles seen in the Nyquist plot. An equivalent circuit also shown in Figure a was used to fit impedance semicircles in low, medium, and high frequency ranges to extract the bulk and grain boundary impedances and to estimate electrode contact resistance. ,− Li + transport and conduction through grain boundaries and thin-film bulk are characterized by the ionic conductivities calculated according to eqs – σ total , σ bulk , and σ gb for the thin film were 2.17 × 10 –5 , 7.2 × 10 –5 , and 3.11 × 10 –5 S/cm, respectively.…”

Lithium Dendrite Propagation in Ta-Doped Li7La3Zr2O12 (LLZTO): Comparison of Reactively Sintered Pyrochlore-to-Garnet vs LLZTO by Solid-State Reaction and Conventional Sintering

“…P2G LLZTO was prepared from Ta-doped pyrochlores synthesized using a nonaqueous sol–gel method as described in our previous work . Briefly, the pyrochlore was synthesized from a mixture of metal organic precursors dissolved in propionic acid and dichloromethane that was combusted at 850 °C for 8 h, followed by ball-milling with LiOH (25 mol % excess Li) and then pressing into a green pellet with uniaxial pressure at ∼300 MPa with a SpecAc press.…”

“…The raw materials were ball milled (SPEX 8000M, 1050 cycles per minute for 90 min) for good mixing, calcined at 950 °C for 12 h, ball milled again, and then prepared into a green pellet using uniaxial pressing at ∼300 MPa with a SpecAc press. The pellets were sintered in MgO crucibles under a Li 2 O-rich environment, as described in our previous works, , in air using a tube furnace (Lindberg/Blue M TF55030A) with Al 2 O 3 tubes and a heating rate of 5 °C/min. The P2G and SSR pellets were sintered at 1100 °C for 2 or 6 h, while some SSR pellets were also sintered at 1200 °C for 9 h. The nominal composition of both types of LLZTO was Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 .…”

“…Among the various kinds of doped LLZO, Ta 5+ -doped LLZO (LLZTO) is known to have good ionic conductivity and electrochemical stability . LLZTO is commonly synthesized via solid-state reactions (SSRs) that require synthesis and then sintering at high temperatures (>1100 °C) for long durations (>6 h), which can be accompanied by Li loss and formation of poorly conducting phases. , To reduce the temperature and time required for both synthesis and sintering of LLZTO, we recently developed a new reactive sintering method that forms and densifies LLZTO from pyrochlore-type precursors in one step. , In this approach, which we call pyrochlore-to-garnet (P2G), Ta 5+ -doped pyrochlore La 2.4 Zr 1.12 Ta 0.48 O 7.04 is first synthesized using molten salt or nonaqueous sol–gel methods and then reacted with a Li source (typically LiOH) to obtain LLZTO. During the reactive sintering process, the LiOH melts and then decomposes into Li 2 O, which subsequently reacts with the pyrochlore to form LLZTO.…”