Search Results (11)

After reviewing the state of the art of the fluorination of inorganic solid electrolytes, an application of gas/solid fluorination is given and how it can be processed. Garnet-type oxide has been chosen. These oxides with an ideal structure of chemical formula A₃B₂(XO₄)₃ are mainly known for their magnetic and dielectric properties. Certain garnets may have a high enough Li⁺ ionic conductivity to be used as solid electrolyte of lithium ion battery. The surface of LLZO may be changed in contact with the moisture and CO₂ present in the atmosphere that results in a change of the conductivity at the interface of the solid. LiOH and/or lithium carbonate are formed at the surface of the garnet particles. In order to allow for handling and storage under normal conditions of this solid electrolyte, surface fluorination was performed using elemental fluorine. When controlled using mild conditions (temperature lower or equal to 200 °C, either in static or dynamic mode), the addition of fluorine atoms to LLZO with Li_6,4Al_0,2La₃Zr₂O₁₂ composition is limited to the surface, forming a covering layer of lithium fluoride LiF. The effect of the fluorination was evidenced by IR, Raman, and NMR spectroscopies. If present in the pristine LLZO powder, then the carbonate groups disappear. More interestingly, contrary to the pristine LLZO, the contents of these groups are drastically reduced even after storage in air up to 45 days when the powder is covered with the LiF layer. Surface fluorination could be applied to other solid electrolytes that are air sensitive. Full article

Lithium-conducting NASICON materials have emerged as a promising alternative to organic liquid electrolytes for high-energy-density Li-metal batteries, owing to their superior ionic conductivity and excellent air stability. However, their practical application is hindered by poor sintering characteristics and high grain boundary resistance. In this investigation, Li_1.3Al_0.3−xY_xTi_1.7(PO₄)₃ (LAYTP-x, x = 0.00, 0.01, 0.03, 0.05, and 0.07) were successfully synthesized via conventional solid-state reaction to explore the impact of Y³⁺ on both ionic conductivity and chemical stability. The structural, morphological, and transport properties of the samples were comprehensively characterized in order to identify the optimal doping concentration. All samples exhibited a NASICON structure with a uniform distribution of Y elements within the electrolyte. Due to its highest relative density (95.8%), the LAYTP-0.03 electrolyte demonstrated the highest total conductivity of 2.03 × 10⁻⁴ S cm⁻¹ with a relatively low activation energy of 0.33 eV, making it suitable for solid-state batteries. When paired with the NCM811 cathode, the Li/LAYTP-0.03/NCM811 cell exhibited outstanding electrochemical performance: a high capacity of 155 mAh/g was achieved at 0.2C after 50 cycles with a Coulombic efficiency of approximately 100%, indicating highly reversible lithium plating/stripping facilitated by the LAYTP-0.03 electrolyte. These results suggest that the LAYTP-0.03 ceramic electrolyte could be a promising alternative for developing safe solid-state Li-metal batteries. Full article

Stabilized Li_6.25La₃Al_0.25 Zr₂O₁₂ (cubic LLZO or c-LLZO) is a Li⁺-conducting ceramic with ionic conductivities approaching 1 mS-cm. Processing c-LLZO so that it is suitable for use as a solid state electrolyte in all solid state batteries, however, is challenging due to the formation of secondary phases at elevated temperatures. The work described in this manuscript examines the formation of one such secondary phase La₂Zr₂O₇ (LZO) formed during sintering c-LLZO at 1000 °C. Specifically, spatially resolved Raman spectroscopy and X-ray Diffraction (XRD) measurements have identified gradients in Li distributions in the Li ion (Li⁺)-conducting ceramic Li_6.25La₃Al_0.25 Zr₂O₁₂ (cubic LLZO or c-LLZO) created by thermal processing. Sintering c-LLZO under conditions relevant to solid state Li⁺ electrolyte fabrication conditions lead to Li⁺ loss and the formation of new phases. Specifically, sintering for 1 h at 1000 °C leads to Li⁺ depletion and the formation of the pyrochlore lanthanum zirconate (La₂Zr₂O₇ or LZO), a material known to be both electronically and ionically insulating. Circular c-LLZO samples are covered on the top and bottom surfaces, exposing only the 1.6 mm-thick sample perimeter to the furnace’s ambient air. Sintered samples show a radially symmetric LZO gradient, with more LZO at the center of the pellet and considerably less LZO at the edges. This profile implies that Li⁺ diffusion through the material is faster than Li⁺ loss through volatilization, and that Li⁺ migration from the center of the sample to the edges is not completely reversible. These conditions lead to a net depletion of Li⁺ at the sample center. Findings presented in this work suggest new strategies for LLZO processing that will minimize Li⁺ loss during sintering, leading to a more homogeneous material with more reproducible electrochemical behavior. Full article

The solid oxide electrolyte Li_1.5Al_0.5Ge_1.5(PO₄)₃ (LAGP) with a NASICON structure has a high bulk ionic conductivity of 10⁻⁴ S cm⁻¹ at room temperature and good stability in the air because of the strong P⁵⁺-O²⁻ covalence bonding. However, the Ge⁴⁺ ions in LAGP are quickly reduced to Ge³⁺ on contact with the metallic lithium anode, and the LAGP ceramic has insufficient physical contact with the electrodes in all-solid-state batteries, which limits the large-scale application of the LAGP electrolyte in all-solid-state Li-metal batteries. Here, we prepared flexible PEO/LiTFSI/LAGP composite electrolytes, and the introduction of LAGP as a ceramic filler in polymer electrolytes increases the total ionic conductivity and the electrochemical stability of the composite electrolyte. Moreover, the flexible polymer shows good contact with the electrodes, resulting in a small interfacial resistance and stable cycling of all-solid-state Li-metal batteries. The influence of the external pressure and temperature on Li⁺ transfer across the Li/electrolyte interface is also investigated. Full article

Lithium batteries, as energy storage devices, are playing an increasingly important role in human society. As a result of the low safety of the liquid electrolyte in batteries, more attention has been paid to solid electrolytes. Based on the application of lithium zeolite in a Li-air battery, a non-hydrothermal conversed lithium molecular sieve was prepared. In this paper, in-situ infrared spectroscopy, together with other methods, was used to characterize the transformation process of geopolymer-based zeolite. The results showed that Li/Al = 1.1 and 60 °C were the best transformation conditions for the Li-ABW zeolite. On this basis, the geopolymer was crystallized after 50 min of reaction. This study proves that the formation of geopolymer-based zeolite occurs earlier than the solidification of the geopolymer and shows that the geopolymer is a good precursor for zeolite conversion. At the same time, it comes to the conclusion that the formation of zeolite will have an impact on the geopolymer gel. This article provides a simple preparation process for lithium zeolite, explores the preparation process and mechanism, and provides a theoretical basis for future applications. Full article

Thermal abuse of lithium-ion batteries (LIBs) leads to the emission of gases, solids, fires and/or explosions. Therefore, it is essential to define the temperatures at which key events occur (i.e., CID activation, venting, and thermal runaway (TR)) and to identify the related emissions for identifying the hazards to which people and especially rescue teams are exposed. For this purpose, thermal abuse tests were performed on commercial lithium nickel cobalt aluminum oxide (NCA) 18650 cells at 50% state of charge in a reactor connected to an FT-IR spectrometer by varying test conditions (feed gas of N₂ or air; heating rates of 5 or 10 °C/min until 300 °C). In particular, the concentrations of the gases and the composition of the condensed-phase emissions were estimated. As regards gases, a high concentration (1695 ppmv) of hydrofluoric acid (HF) was measured, while the emissions of condensed matter consisted of organic compounds such as polyethylene oxide and paraffin oil, and inorganic compounds containing Li (0.173 mg/m³) and Al (0.344 mg/m³). The main safety concerns were caused by the temperatures (564 ± 85 °C) reached by the cell during TR, by the HF concentration which exceeded the toxicity limits of 30 ppm, the IDLH defined by the NIOSH, and the diameter of the particles (1.54 ± 0.69 µm) that rose the PM2.5 concentration. These results are also useful for identifying personal protection equipment for rescue teams. Full article

NASICON-type Li_1.5Al_0.5Ge_1.5(PO₄)₃ (LAGP) is a remarkable solid-state electrolyte due to its high ionic conductivity and excellent air stability. However, the weak LAGP|Li interfacial compatibility (e.g., chemical instability of LAGP with Li metal and lithium dendrite growth) limits its practical application. Herein, an ultrathin CuS layer was fabricated on the surface of the LAGP electrolyte by magnetron sputtering (MS). Then, an in situ Li₂S/Cu nano-layer formed via the conversion reaction between CuS and molten Li was constructed at the LAGP|Li interface. The Li₂S/Cu nano-layer enables effective hindering of the reduction reactions of LAGP with Li metals and the suppression of lithium dendrite growth. The assembled Li symmetric battery with the Li₂S/Cu@LAGP electrolyte shows a promising critical current density (CCD) of 0.6 mA cm⁻² and a steady battery operation for over 700 h. Furthermore, the full LiFePO₄ battery comprising the Li₂S/Cu@LAGP electrolyte shows excellent capacity retention of 94.5% after 100 cycles, providing an appropriate interface modification strategy for all-solid-state Li metal batteries. Full article

The next generation of all-solid-state batteries can feature battery safety that is unparalleled among conventional liquid batteries. The garnet-type solid-state electrolyte Li₇La₃Zr₂O₁₂ (LLZO), in particular, is widely studied because of its high Li-ion conductivity and stability in air. However, the poor interface-contact between Li and the electrolyte (garnet) severely limits the development of solid electrolytes. In this study, we synthesize cubic phase Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZTO) using a secondary sintering method. In addition, a thin aluminum nitride (AlN) layer is introduced between the metal (Li) and the solid electrolyte. Theoretical calculations show that AlN has a high affinity for Li. Furthermore, it is shown that the AlN coating can effectively reduce the interface impedance between Li and the solid electrolyte and improve the lithium-ion transport. The assembled symmetric Li cells can operate stably for more than 3600 h, unlike the symmetric cells without AlN coating, which short-circuited after only a few cycles. The hybrid solid-state battery with a modified layer, which is assembled using LiFePO₄ (LFP), still has a capacity of 120 mAh g⁻¹ after 200 cycles, with a capacity retention rate of 98%. This shows that the introduction of an AlN interlayer is very helpful to obtain a stable Li/solid-electrolyte interface, which improves the cycling stability of the battery. Full article

Lithium aluminum germanium phosphate (LAGP) solid electrolyte is receiving increasing attention due to its high ionic conductivity and low air sensitivity. However, the poor interface compatibility between lithium (Li) metal and LAGP remains the main challenge in developing all-solid-state lithium batteries (ASSLB) with a long cycle life. Herein, this work introduces a thin aluminum oxide (Al₂O₃) film on the surface of the LAGP pellet as a physical barrier to Li/LAGP interface by the atomic layer deposition technique. It is found that this layer induces the formation of stable solid electrolyte interphase, which significantly improves the structural and electrochemical stability of LAGP toward metallic Li. As a result, the optimized symmetrical cell exhibits a long lifetime of 360 h with an areal capacity of 0.2 mAh cm⁻² and a current density of 0.2 mA cm⁻². This strategy provides new insights into the stabilization of the solid electrolyte/Li interface to boost the development of ASSLB. Full article

Li₇La₃Zr₂O₁₂ garnet (LLZO) belongs to the most promising solid electrolytes for the development of solid-state Li batteries. The stability of LLZO upon exposure to air is still a matter of discussion. Therefore, we performed a comprehensive study on the aging behavior of Al-stabilized LLZO (space group (SG) $Ia\overline{3}d$) and Ga-stabilized LLZO (SG $I\overline{4}3d$) involving 98 powder and 51 single-crystal X-ray diffraction measurements. A Li⁺/H⁺ exchange starts immediately on exposure to air, whereby the exchange is more pronounced in samples with smaller particle/single-crystal diameter. A slight displacement of Li from interstitial Li2 (96h) toward the regular tetrahedral Li1 (24d) sites occurs in Al-stabilized LLZO. In addition, site occupancy at the 96h site decreases as Li⁺ is exchanged by H⁺. More extensive hydration during a mild hydrothermal treatment of samples at 90 °C induces a structural phase transition in Al-LLZO to SG $I\overline{4}3d$ with a splitting of the 24d site into two independent tetrahedral sites (i.e., 12a and 12b), whereby Al³⁺ solely occupies the 12a site. Li⁺ is preferably removed from the interstitial 48e site (equivalent to 96h). Analogous effects are observed in Ga-stabilized LLZO, which has SG $I\overline{4}3d$ in the pristine state. Full article

Solid Al–air batteries are a promising power source for potable electronics due to their environmentally friendly qualities and high energy density. However, the solid Al–air battery suffers from anodic corrosion and it is difficult to achieve a higher specific capacity. Thus, this work aims at suppressing the corrosion of Al anode by adding an electrospun Al₂O₃ interlayer on to the surface of the anode. The Al₂O₃ interlayer effectively inhibits the self-corrosion of the Al anode. Further, the effects of the thickness of the Al₂O₃ film on corrosion behavior were investigated. The results showed that the Al–air battery with a 4 μm Al₂O₃ interlayer is more suitable for a low current density discharge, which could be applied for mini-watt devices. With a proper thickness of the Al₂O₃ interlayer, corrosion of the anode was considerably suppressed without sacrificing the discharge voltage at a low current density. The Al–air battery with a 4 μm Al₂O₃ interlayer provided a significantly high capacity (1255 mAh/g at 5 mA/cm²) and an excellent stability. This wo presents a promising approach for fabricating an inhibiting corrosion interlayer for solid Al–air battery designed for mini-watt devices. Full article