Crystal structure and morphology of B-Al doped-lithium lantanum zirconate (original) (raw)
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Solid State Ionics, 2017
In this study, Li 3 BO 3 glass ceramic was utilized as a sintering additive for producing garnet-type Li 7 La 3 Zr 2 O 12 solid electrolytes by low temperature sintering. The shrinkage and wetting behaviors of the Li 7 La 3 Zr 2 O 12-Li 3 BO 3 composite powder during heating were analyzed by dilatometry. The sintering shrinkage of the Li 7 La 3 Zr 2 O 12-Li 3 BO 3 composite powder occurred in two stages and was related to the densification of the composite. It was also closely related to the wetting behavior of the Li 3 BO 3 glass. The sintering of Li 7 La 3 Zr 2 O 12-Li 3 BO 3 from around 700°C is driven by the viscous sintering of Li 3 BO 3 glass, while sintering above 850°C is due to particle rearrangement in Li 7 La 3 Zr 2 O 12 as well as the solid-state sintering of Li 7 La 3 Zr 2 O 12 after the melting of Li 3 BO 3. The density of the Li 7 La 3 Zr 2 O 12-8 wt% Li 3 BO 3 composite sintered for 8 h at 1100°C was 86.4% of the theoretical density, whereas the ionic conductivity was 1.94 × 10 −5 S cm −1 .
Journal of the Korean Ceramic Society, 2016
In this study, we investigate the effect of the Li 3 BO 3 additive on the densification and ionic conductivity of garnet-type Li 7-La 3 Zr 2 O 12 solid electrolytes for all-solid-state lithium batteries. We analyze their densification behavior with the addition of Li 3-BO 3 in the range of 2-10 wt.% by dilatometer measurements and isothermal sintering. Dilatometry analysis reveals that the sintering of Li 7 La 3 Zr 2 O 12-Li 3 BO 3 composites is characterized by two stages, resulting in two peaks, which show a significant dependence on the Li 3 BO 3 additive content, in the shrinkage rate curves. Sintered density and total ion conductivity of the system increases with increasing Li 3 BO 3 content. After sintering at 1100 o C for 8 h, the Li 7 La 3 Zr 2 O 12-8 wt.% Li 3 BO 3 composite shows a total ionic conductivity of 1.61 × 10 −5 Scm −1 , while that of the pure Li 7 La 3 Zr 2 O 12 is only 5.98 × 10 −6 Scm −1 .
2024
Solid-state batteries have garnered attention due to their potentiality for increasing energy density and enhanced safety. One of the most promising solid electrolytes is garnet-type Li7La3Zr2O12 (LLZO) ceramic electrolyte because of its high conductivity and ease of manufacture in ambient air. The complex gas-liquid-solid sintering mechanism makes it difficult to prepare LLZO with excellent performance and high consistency. In this study, an in-situ Li2O-atmosphere assisted solvent-free route is developed for producing the LLZO ceramics. First, the lithium-rich additive Li6Zr2O7 (LiZO) is applied to in-situ supply Li2O atmosphere at grain boundaries, where its decomposition products (Li2ZrO3) build the bridge between the grain boundaries. Second, comparisons were studied between the effects of dry and wet routes on the crystallinity, surface contamination, and particle size of calcined powders and sintered ceramics. Third, by analyzing the grain boundary composition and the evolution of ceramic microstructure, the impacts of dry and wet routes and lithium-rich additive LiZO on the ceramic sintering process were studied in detail to elucidate the sintering behavior and mechanism. Lastly, exemplary Nb-doped LLZO pellets with 2 wt% LiZO additives sintered at 1,300 °C × 1 min deliver Li+ conductivities of 8.39 × 10-4 S cm-1 at 25 °C, relative densities of 96.8%, and ultra-high consistency. It is believed that our route sheds light on preparing high-performance LLZO ceramics for solid-state batteries.
In this review work it has been tried to briefly summarize solid state electrolytes conductivity status. As the very essential component for battery efficiency and performance, electrolytes need be given due attention as safety problems could also emanate from it as well. The oxide solid state electrolytes are very promising electrolytes for allsolid-state batteries for large applications. The garnet-structured Li 7 La 3 Zr 2 O 12 has shown high ionic conductivity that is comparable to the liquid electrolytes with large potential windows. At lower temperature Li 7 La 3 Zr 2 O 12 will have high Li-ordered and forms the tetragonal structure which is less ionic conductor as compared to the less Li-ordered cubic structure. A total ionic conductivity of the order of 10 -3 Scm -1 has been achieved by the cubic structures of Li 7 La 3 Zr 2 O 12 which will let it to be applicable in practice.
Journal of Nanoscience and Nanotechnology, 2019
In this study, a Li 3 BO 3 (LBO) compound is synthesized via the heat-treatment of polymeric precursors containing Li and B in air at 700 C for 5 h to use as a sintering additive for the densification of Li 7 La 3 Zr 2 O 12 (LLZ) solid electrolyte. The synthesized LBO powder is suitable for promoting the densification, cubic phase stability, and ionic conductivity of LLZ. X-ray diffraction analysis indicated that monophasic cubic LLZ could be obtained by the addition of LBO in sintering, changing to cubic LLZ phase from LZ impurities detected in raw LLZ. The sintered LLZ-12 wt% LBO showed that the densification of the LLZ with LBO occurred by a coupling effect including the particle rearrangement of LLZ in the melted LBO phase and grain growth of LLZ particles. The density of the LLZ-12 wt% LBO composite sintered at 1100 C for 8 h was 3.72 g/cm 3 (86% of theoretical density); the composite showed the high Li-ion conductivity of 1.18 × 10 −4 S • cm −1 at 28 C.
Tantalum-doped garnet (Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 , LLZTO) is a promising candidate to act as a solid electrolyte in all-solid-state batteries owing to both its high Li + conductivity and its relatively high robustness against the Li metal. Synthesizing LLZTO using conventional solid-state reaction (SSR) requires, however, high calcination temperature (>1000°C) and long milling steps, thereby increasing the processing time. Here, we report on a facile synthesis route to prepare LLZTO using a molten salt method (MSS) at lower reaction temperatures and shorter durations (900°C, 5 h). Additionally, a thorough analysis on the properties, i.e., morphology, phase purity, and particle size distribution of the LLZTO powders, is presented. LLZTO pellets, either prepared by the MSS or the SSR method, that were sintered in a Pt crucible showed Li + ion conductivities of up to 0.6 and 0.5 mS cm −1 , respectively. The corresponding activation energy values are 0.37 and 0.38 eV, respectively. The relative densities of the samples reached values of approximately 96%. For comparison, LLZTO pellets sintered in alumina crucibles or with γ-Al 2 O 3 as sintering aid revealed lower ionic conductivities and relative densities with abnormal grain growth. We attribute these observations to the formation of Al-rich phases near the grain boundary regions and to a lower Li content in the final garnet phase. The MSS method seems to be a highly attractive and an alternative synthetic approach to SSR route for the preparation of highly conducting LLZTO-type ceramics.
Ionics, 2005
This paper reports a novel approach to designing advanced solid Li ion electrolytes for application in various solid state ionic devices, including Li ion secondary batteries, gas sensors, and electrochromic displays. The employed methodology involves a solid-solution reaction between the two best-known fast Li ion conductors in the garnet-family of compounds Li 6 BaLa 2 M 2 O 12 (M) Nb, Ta) and Li 7 La 3 Zr 2 O 12. Powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), AC impedance, and 7 Li nuclear magnetic resonance (Li NMR) spectroscopy were employed to characterize phase formation, morphology, ionic conductivity, and Li ion coordination in Li 6.5 La 2.5 BaZrMO 12. PXRD shows for formation of a cubic garnet-like structure and AC impedance data is consistent with other known solid Li ion electrolytes. Li 6.5 La 2.5 BaZrTaO 12 exhibits a fast Li ion conductivity of about 6 × 10-3 S cm-1 at 100°C, which is comparable to that of currently employed organic polymer electrolytes value at room temperature. The Nb analogue shows an order of magnitude lower ionic conductivity than that of the corresponding Ta member, which is consistent with the trend in garnet-type electrolytes reported in the literature. Samples sintered at 1100°C shows the highest electrical conductivity compared to that of 900°C. 7 Li MAS NMR shows a sharp single peak at 0 ppm with respect to LiCl, which may be attributed to fast migration of ions between various sites in the garnets, and also suggesting average distributions of Li ions at average octahedral coordination in Li 6.5 La 2.5 BaZrMO 12. The present work together with literature used to establish very important fundamental relationship of functional property-Li concentration-crystal structure-Li diffusion coefficient in the garnet family of Li ion electrolytes.
High conductivity of mixed phase Al-substituted Li7La3Zr2O12
Journal of Electroceramics, 2015
Al-substituted Li 7 La 3 Zr 2 O 12 (LLZ:Al) was synthesized via conventional solid state reaction. Different dwell times at sintering temperature of 1200°C led to a varying Li content in LLZ:Al which significantly affected the Li-ion conductivity. Electrochemical impedance spectroscopy and X-ray diffraction were used to characterize the sintered pellets which showed a maximum total ionic conductivity of~3 × 10 −4 S cm −1 at room temperature although the samples were composed of cubic and tetragonal LLZ:Al, with the tetragonal phase as its major phase. Inductively coupled plasma optical emission spectroscopy revealed that the Li content steadily decreased from 7.5 to 6.5 Li per formula unit with increasing sintering time. The highest conductivity was observed from the sample with the lowest Li concentration at 6.5 per formula unit. Scanning electron microscopy images revealed the formation of large grains, about 500 μm in diameter, which additionally could be the reason for achieving high total Li-ion conductivity. Electrochemical tests showed that mixed phase LLZ:Al is stable against metallic Li up to 8 V.
Chemistry of Materials, 2016
Several "Beyond Li-Ion Battery" concepts such as all solid-state batteries and hybrid liquid/solid systems envision the use of a solid electrolyte to protect Li-metal anodes. These configurations are very attractive due to the possibility of exceptionally high energy densities and high (dis)charge rates, but they are far from being realized practically due to a number of issues including high interfacial resistance and difficulties associated with fabrication. One of the most promising solid electrolyte systems for these applications is Al or Ga stabilized Li 7 La 3 Zr 2 O 12 (LLZO) based on high ionic conductivities and apparent stability against reduction by Li metal. Nevertheless, the fabrication of dense LLZO membranes with high ionic conductivity and low interfacial resistances remains challenging; it definitely requires a better understanding of the structural and electrochemical properties. In this study, the phase transition from garnet (Ia3̅ d, No. 230) to "non-garnet" (I4̅ 3d, No. 220) space group as a function of composition and the different sintering behavior of Ga and Al stabilized LLZO are identified as important factors in determining the electrochemical properties. The phase transition was located at an Al:Ga substitution ratio of 0.05:0.15 and is accompanied by a significant lowering of the activation energy for Li-ion transport to 0.26 eV. The phase transition combined with microstructural changes concomitant with an increase of the Ga/Al ratio continuously improves the Li-ion conductivity from 2.6 × 10 −4 S cm −1 to 1.2 × 10 −3 S cm −1 , which is close to the calculated maximum for garnet-type materials. The increase in Ga content is also associated with better densification and smaller grains and is accompanied by a change in the area specific resistance (ASR) from 78 to 24 Ω cm 2 , the lowest reported value for LLZO so far. These results illustrate that understanding the structure−properties relationships in this class of materials allows practical obstacles to its utilization to be readily overcome.