Lithium Aluminum Germanium Phosphate Research Articles

Co-Sintering of Lithium Aluminum Germanium Phosphate (LAGP) Glass/Powder Composite Electrolyte for Multilayer Ceramic Batteries

Inorganic solid electrolytes are one of the key materials instead of organic liquid electrolytes for next-generation all-solid-state batteries (ASSBs). The advantages of ASSBs are long cycle life and high safety due to the non-flammable of the solid electrolyte. The ASSBs can be stacked layer by layer, reducing the volume in battery packaging and resulting in increased energy density. These ASSBs can be applied to wearable or healthcare or smart home devices in the form of multilayer ceramic battery (MLCB), in addition to energy storage devices and electric vehicles. However, the MLCBs are difficult to fabricate due to the high sintering temperature and high interfacial resistance of the solid electrolyte. The Li-based solid electrolytes of NASICON-type have received much attention as prospective solid electrolytes due to their high ionic conductivity and high stability against moisture. Especially, lithium aluminum germanium phosphate (LAGP) is potential solid electrolyte material in the NASICON family due to superior stability. LAGP glass electrolyte was selected to enable sintering at low temperatures and reduce resistance at the interface for the application to MLCB.In this study, a LAGP-based solid electrolyte ceramic sheet was prepared using glass/powder composite at 750 °C. The obtained LAGP-based solid electrolyte exhibited a NASICON-type hexagonal structure and a total ionic conductivity of 1.45 × 10-4 S/cm at 25 ˚C. A Coin cell with the LAGP composite electrolyte, LiCoO2 (LCO) as cathode, and Li metal as anode was assembled. The coin cell was charged and discharged by using a battery cycler and the charge capacity was approximately 130 mAh∙g-1. Additionally, we prepared a LiMnPO4 glass-based cathode (LMP) using conventional melt quenching techniques and then stacked it layer by layer with the LAGP electrolyte and co-sintered at 650°C. After co-sintering the LAGP/LMP cell, it was confirmed that the interface between the LAGP composite electrolyte and the LMP cathode was well attached, and its ionic conductivity maintained a value similar to that of the LAGP composite electrolyte. Subsequently, an electrochemical analysis of the LAGP/LMP cell was performed.

Quasi-solid-state composite polymer electrolyte with NASICON-type nanofillers for high performance lithium-oxygen batteries

This study designs a quasi-solid-state composite polymer electrolyte (QSCPE) to improve the performance of LiO2 batteries by integrating a composite solid framework and liquid electrolyte. The solid framework, containing poly(vinylidene difluoride-co-hexafluoropropylene) (PVDF-HFP) and sodium superionic conductor (NASICON)-type lithium aluminum germanium phosphate (LAGP) filler, is prepared using a conventional solution casting method. The framework is then activated using a liquid electrolyte to fabricate the QSCPE. The optimized electrolyte exhibits a high ionic conductivity and wide electrochemical stability. The Li/QSCPE/Li symmetric cell shows an overpotential of below 100 mV and a cycle life of >250 cycles at 1 mA cm−2 at a capacity of 2 mA h cm−2, ensuring electrochemical stability. The LiO2 cell fabricated using the optimized electrolyte exhibits significantly improved cyclability with a cycle life of 152. The QSCPE effectively prevents contamination of Li and suppresses the growth of Li dendrites. These results suggest that the LAGP nanofillers-containing QSCPE is a promising approach for further improving the performance of LiO2 batteries.

Progress and Perspectives of Lithium Aluminum Germanium Phosphate‐Based Solid Electrolytes for Lithium Batteries

AbstractSolid‐state lithium batteries are considered promising energy storage devices due to their superior safety and higher energy density than conventional liquid electrolyte‐based batteries. Lithium aluminum germanium phosphate (LAGP), with excellent stability in air and good ionic conductivity, has gained tremendous attention over the past decades. However, the poor interface compatibility with Li anode, slow Li‐ion conduction in thick pellets, and high‐temperature sintering procedure limit the further development of LAGP solid electrolytes in practical applications. This review comprehensively summarizes the crystal structure, Li‐ion conducting mechanism, and various synthesis methods, especially the latest thin‐film preparation approach. The underlying reason for Li/LAGP interfacial instability is identified, followed by several advanced interface engineering strategies, for example, introducing a functional interlayer. The integration design of LAGP‐based solid electrolytes and cathode is also highlighted to enable high‐loading cathodes. Additionally, recent progress of lithium‐oxygen and lithium‐sulfur batteries with LAGP‐based solid electrolytes is discussed. Moreover, the different Li‐ion migration pathways, preparation procedures, and electrochemical performance of polymer‐LAGP composite solid electrolytes in Li‐ion batteries are introduced. Lastly, the remaining challenges and opportunities are proposed to encourage more efforts in this field. This review aims to provide fundamental insights and promising directions toward practical LAGP‐based solid‐state batteries.

Mechanochemical synthesis of LAGP/PEG hybrid solid electrolyte: Investigation of surface structure and chemistry

The drive towards all solid state lithium ion batteries requires discovery of new methods for synthesis of true hybrid solid electrolytes in which organic and inorganic components are chemically associated to simultaneously maximize lithium ion conductivity and processability. Herein, the first mechanochemical milling synthesis of an ambient processable hybrid lithium aluminum germanium phosphate (Li1.5Al0.5Ge1.5(PO4)3)/polyethylene glycol (PEG) solid electrolyte is presented. Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA) provide evidence that the mechanochemical milling procedure impels a condensation reaction between the ceramic and organic phases which produces a surface product, water. Solid state nuclear magnetic resonance (NMR) spectroscopy confirms that protons from the polymer or associated surface water product are in bonding proximity to the Q2 metaphosphate sites of the glassy phase of the ceramic. This work thus establishes the viability of mechanochemical milling as a synthetic pathway for a class of promising ambient processable hybrid electrolytes.

PEO-based Interlayers for LAGP-type Solid-State Lithium-Metal Batteries

Solid-state electrolytes (SSEs) are expected to play a decisive role for the realization of safer rechargeable batteries and may, additionally, allow for the employment of lithium-metal anodes, thus, paving the way for significantly higher energy densities. 1, 2 There are essentially two main groups of SSEs: (i) polymer and (ii) inorganic solids. The latter can be divided, e.g., into sulfide and oxide based electrolytes. 3 Among the oxides, the so-called NASICON-type electrolytes such as LAGP (lithium aluminum germanium phosphate) are considered as attractive low-cost alternative compared to sulfides. 4 Nonetheless, the incompatibility of LAGP with lithium metal accompanied by the formation of highly resistive interfacial reaction products, detrimentally affecting cycle life and rate capability, remain a great challenge. 5 To overcome this issue, the introduction of polyether (e.g., polyethylene oxide, PEO) as protective interlayer between the lithium-metal anode and the LAGP SSE was proposed. 6, 7, 8 The successful use of such interlayers, however, requires a fast and efficient charge transfer across this interlayer. Herein, we present a comprehensive investigation of PEO-based interlayers comprising varying amounts of ionic liquid-based electrolytes, which consist ofN-butyl-N-methyl pyrrolidinium-based and lithium cations as well as bis(fluorosulfonyl)imide (FSI-) and bis(trifluoromethanesulfonyl)imide (TFSI-) anions. Optimized compositions and the incorporation of selected additives further enhances the charge transfer across this interlayer and the two interfaces with the LAGP electrolyte and lithium metal, enabling long-term stable cycle life and good rate capability of the resulting lithium-metal battery cells.

The Effect of Pressure during Sintering on the Interface between Oxide Solid Electrolyte and Cathode in Solid State Lithium Batteries

Conventional Li-ion batteries (LIBs), which have been widely used as main power sources for various electronic devices, are facing huge challenges with the explosive growth of electric vehicles (EVs) market. The safety problems of LIBs in EVs causing fire incident mainly result from the use of liquid electrolytes which provide fuel for combustion. Therefore, solid state lithium batteries using a solid electrolyte are widely accepted as promising candidates for next generation energy storage devices with superior safety performances. However, solid state batteries have limitations that originate from solid-solid interfaces between electrode and solid electrolyte, hindering practical development of solid state batteries. Especially, compared to sulfide based solid electrolyte, oxide based solid electrolyte is rigid, resulting in difficulty in forming intimate contact between solid electrolyte and electrode materials. In this study, using lithium vanadium phosphate (Li3V2(PO4)3, LVP) and lithium aluminum germanium phosphate (Li1.5Al0.5Ge1.5(PO4)3, LAGP) as cathode material and oxide solid electrolyte model system, we demonstrate the effect of pressure during sintering on the contact between LVP and LAGP, and concomitant cell performance. In addition, we found that the crystallinity of solid electrolyte and the content of carbon conducting agent critically affect the contact. Without any complicated interfacial modification, we successfully made decent cathode-solid electrolyte interface with simple method for superior solid state lithium batteries.

Plasma Charge Carrier Attachment Induced Transport in Solid Ionic Materials

Lithium aluminum germanium phosphate of the stoichiometric formula Li1.5Al0.5Ge1.5(PO4)3 has been studied by means of the femtosecond laser plasma charge attachment induced transport (fs-plasma CAIT) [1]. The technique is based on attaching polarity selected charge carriers from a plasma to the front side of a sample, which induces transport of mobile charge carriers in the bulk of this sample. First, in a conductivity study, an activation energy of 0.73 eV for lithium ion transport has been measured by means of proton attachment. Second, a constant-voltage attachment experiment employing deuterium ions has been performed and subsequently analyzed by time-of-flight secondary ion mass spectrometry. The resulting concentration depth profile revealed a replacement of native lithium ions by deuterons in the first 350 nm of the sample. A theoretical analysis of the profile by means of the Nernst−Planck−Poisson equations provides access to the concentration dependent diffusion coefficient and the unique site energy distribution of the natively contained lithium ions. A full width at half-maximum of 113 meV for the SED of the Li+ ions is determined. The approach discussed can be applied to many more materials, where the potential energy landscape affects the function.More recent efforts in studying solid state ionic materials by means of the Plasma-CAIT technique will also be presented.[1] Jan L. Wiemer, Martin Schäfer, and Karl-Michael Weitzel, J. Phys. Chem. C, 125, 4977−4985, (2021) Figure 1

Improving the Stability of Lithium Aluminum Germanium Phosphate with Lithium Metal by Interface Engineering.

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.

Enhancing Electrochemical Performances of Rechargeable Lithium-Ion Batteries via Cathode Interfacial Engineering.

Lithium-ion batteries (LIBs) have transformed modern electronics and rapidly advancing electric vehicles (EVs) due to their high energy and power densities, cycle-life, and acceptable safety. However, the comprehensive commercialization of EVs necessitates the invention of LIBs with much enhanced and stable electrochemical performances, including higher energy/power density, cycle-life, and operational safety, but at a lower cost. Herein, we report a simple method for improving the high-voltage (up to 4.5 V) charge capability of LIBs by applying a Li+-ion-conducting artificial cathode-electrolyte interface (Li+-ACEI) on the state-of-the-art cathode, LiCoO2 (LCO). A superionic ceramic single Li+ ion conductor, lithium aluminum germanium phosphate (Li1.5Al0.5Ge1.5(PO4)3, LAGP), has been used as a novel Li+-ACEI. The application of Li+-ACEI on LCO involves a scalable and straightforward wet chemical process (sol-gel method). Cycling performance, including high voltage charge, of bare and LAGP-coated cathodes has been determined against the most energy-dense anode (lithium, Li metal) and state-of-the-art carbonate-based organic liquid electrolyte (OLE). The application of an LAGP-based Li+-ACEI on LCO displays many improvements: (i) reduced charge-transfer and interfacial resistance; (ii) higher discharge capacity (167.5 vs 155 mAh/g) at 0.2C; (iii) higher Coulombic efficiency (98.9 vs 97.8%) over 100 cycles; and (iv) higher rate capability (143 vs 80.1 mAh/g) at 4C. Structural and morphological characterizations have substantiated the improved electrochemical behavior of bare and Li+-ACEI LCO cathodes against the Li anode.

Improving the Stability of Lithium Aluminum Germanium Phosphate with Lithium Metal by Interface Engineering

Improving the Stability of Lithium Aluminum Germanium Phosphate with Lithium Metal by Interface Engineering

(Student Battery Slam Best Presentation Award Winner) Enhancing the Stability of the Electrode/Electrolyte Interface in Solid State Li-Ion Batteries

All-solid-state Lithium-ion batteries (LIBs) based on solid ceramic electrolytes are a promising next-generation energy storage technology for high energy density and enhanced cycle life. A key requirement for such batteries is packing high energy in low form factor (i.e. in thin-film form) to increase both the gravimetric and volumetric energy densities. Lithium superionic conducting (LISICON) solid electrolytes are prominent candidates among liquid, gel, polymer and solid electrolytes that can enable safety and optimum performance in a high energy density battery with thin-film cell components. One particular LISICON material, lithium aluminum germanium phosphate (LAGP), is a promising solid-electrolyte due to its high ionic conductivity (~ 5 mS/cm at 23 °C), high electrochemical stability window (> 5V), and single Li+ ion conduction (high transference number, low porosity mitigating dendrite propagation), enabling a high energy battery and mitigating safety and packaging issues of conventional LIBs. However, most solid electrolytes, suffer from low chemical stability with the lithium (Li) anode. This is especially true for LAGP, with such chemical instability invariably leading to the formation of a highly resistive electrode/electrolyte interface which is detrimental for high power and cell longevity. Therefore, despite the promise of solid ceramic electrolytes for next-generation solid-state LIBs, if they are to be practical for use in solid-state LIBs with Li metal anodes, it is very important to design a chemically stable interface with kinetically efficient charge transport processes (i.e. Li+ transport). In order to enhance the chemical stability of the electrode/electrolyte interface, we identified lithium compatible materials (such as thin film of lithium phosphorus oxynitride (LIPON), gold (Au), carbon nanotube (CNT) layer, aluminium oxide (Al2O3) and suitable methods to apply them at the Li metal/LAGP interface. The evolution of the interfacial resistance as a function of time was monitored using Electrochemical Impedance Spectroscopy (EIS). We will present data showing that the application of the lithium-compatible, thin film interfacial layer, results in enhanced stability and a significant reduction in resistance compared with the unmodified Li metal/LAGP interface, offering an interfacial engineering approach for improved performance of an all-solid-state LIB.

Li+ Ion Site Energy Distribution in Lithium Aluminum Germanium Phosphate

Lithium aluminum germanium phosphate of the stoichiometric formula Li1.5Al0.5Ge1.5(PO4)3 has been studied by means of the femtosecond laser plasma charge attachment induced transport (fs-plasma CAI...

Highly conductive lithium aluminum germanium phosphate solid electrolyte prepared by sol-gel method and hot-pressing

A hot-pressing process is applied to improve sinterbility of NASICON (Na ion conductor)-type of Li1.5Al0.5Ge1.5(PO4)3 (LAGP) solid electrolyte prepared by sol-gel method. During the hot-pressing process, amorphilization caused by Li loss and reduction of LAGP is observed due to a contact with a carbon mold. To compensate the Li loss, addition of 15% LiNO3 into LAGP powder before the hot-pressing is needed. By the hot-pressing, the porosity of the LAGP pellet is decreased from 12% to 4%. The grain boundary conductivity of hot-pressed LAGP pellet is 5 times higher than that of conventional atmospheric sintered LAGP pellet. Contrary, bulk conductivities are almost same, indicating that the hot-pressing affects only grain boundaries, not crystal structure. The highest conductivity is obtained in the hot-pressed LAGP pellet with 15% LiNO3 addition and bulk, grain boundary and total conductivities are 3.22 × 10-4, 1.69 × 10-3, 2.7 × 10-3 S cm-1, respectively. The activation energy is 0.31 eV, which is comparable to that prepared by conventional melt-quenching method.

Thermophysical Properties of Lithium Aluminum Germanium Phosphate with Different Compositions

The NASICON system LAGP (Li1+xAlxGe2−x (PO4)3 was studied, which is a candidate material for solid state electrolytes. LAGP substrates with different compositions (x = 0.3–0.7) were prepared using a melt quenching route with subsequent heat treatment. In order to develop a better understanding of the relationships between the structure and the ionic as well as the thermal conductivity, respectively, the samples were characterized by X-ray diffraction. The ionic conductivity was measured using impedance spectroscopy while the thermal diffusivity and the specific heat were determined by Laser Flash technique and differential scanning calorimetry, respectively. Additionally, thermal analysis was performed in order to evaluate the thermal stability a higher temperatures and, also to identify the optimum temperature range of the thermal post-processing. The measured values of the ionic conductivities were in the range of 10−4 Ω−1·cm−1 to 10−3 Ω−1·cm−1 at room temperature, but exhibited an increasing behavior as a function of temperature reaching a level of the order 10−2 Ω−1· cm−1 above 200 °C. The thermal conductivity varies only slowly as a function of temperature but its level depends on the composition. The apparent specific heat depends also on the composition and exhibits enthalpy changes due to phase transitions at higher temperatures for LAGP samples with x > 0.5. The compositional dependencies of the ionic and thermal transport properties are not simply correlated. However, the compound with the highest Li-doping level shows the highest ionic conductivity but the lowest thermal conductivity, while the lowest doping level is associated with highest thermal conductivity but the lowest ionic conductivity.

Crystallization behavior of Li1+xAlxGe2-x(PO4)3 glass-ceramics: Effect of composition and thermal treatment

Lithium aluminum germanium phosphate (LAGP) glass-ceramics are promising solid electrolytes for all solid-state lithium ion batteries and other electrochemical applications. LAGP glass-ceramics (Li1+xAlxGe2-x(PO4)3, x = 0.5–0.8) were synthesized using a two-step heat treatment based on characteristic temperatures from Differential scanning calorimeter (DSC) analysis. X-ray diffraction (XRD) and scanning electron microscope (SEM) were used to characterize the crystal phases and their morphologies. Our results show that high purity ion conductive phase can be obtained for the compositions with P/Ge = 2.3 and 2.4 by a two-step heat treatment, instead of the commonly adopted single step heat treatment for composition with P/Ge = 2.0. Electrochemical impedance spectroscopy (EIS) measurements show that Tg + 60%∆T (∆T = Tc-Tg) is the optimal nucleation temperature to obtain high ionic conductivity. Crystallization energies were calculated from the modified Kissinger equation based on DSC measurements and it was concluded that the crystal phase form mainly through internal nucleation. We have found in this paper that, by using a two-step heat treatment, high phase purity LAGP glass-ceramics with lower GeO2 concentration can be obtained to achieve high ionic conductivity.

How Metallic Protection Layers Extend the Lifetime of NASICON-Based Solid-State Lithium Batteries

The use of solid-state electrolytes (SSEs) within batteries is a promising strategy to safely access the high capacity of lithium metal anodes. However, most SSEs with practical ionic conductivity are chemically unstable in contact with lithium metal, which is detrimental to battery performance. Lithium aluminum germanium phosphate (LAGP) is an SSE with high ionic conductivity (10−4-10−3 S cm−1) and good environmental stability, but it forms an amorphous interphase region that continuously grows in contact with Li, leading to chemo-mechanical failure within solid-state batteries. Here, we find that thin (∼30 nm) chromium interlayers deposited between the lithium electrode and LAGP extend cycle life to over 1000 h at moderate current densities (0.1–0.2 mA cm−2), compared to ∼30 h without protection. This significantly improved stability occurs because the metallic interlayer alters the trajectory of interphase formation and the nature of the electrochemical reaction at the interface. This work shows the promise of interface engineering for a variety of SSE materials within solid-state batteries, while emphasizing the necessity of understanding how protection layers affect dynamic evolution of interfaces.

The Role of Metallic Protection Layers in Extending the Stability of Nasicon Electrolytes for Solid-State Batteries

Solid-state batteries with lithium metal anodes are promising candidates for next-generation energy storage devices with improved safety and higher energy density. However, most solid electrolytes with practical ionic conductivities are thermodynamically unstable against lithium metal. Upon interfacial contact with lithium metal, unstable solid electrolytes undergo phase transformations that can be detrimental to battery performance. Lithium aluminum germanium phosphate (LAGP) is a NASICON-type solid electrolyte with relatively high ionic conductivity (10-4 - 10-3 S/cm) and chemical resistance to air and moisture. However, LAGP reacts with lithium to form an electrically-conducting interphase. This interphase continues to propagate from the interface towards the bulk of the solid electrolyte, ultimately leading to failure by causing the solid electrolyte to fracture [1]. In this work, we find that a thin layer of a metal that does not alloy with Li can extend the cycle life of LAGP in symmetric lithium cells from 30 h to more than 800 h at moderate current densities. Interestingly, this significantly improved electrochemical stability is not due to the prevention of interphase formation. Instead, the metal layer alters the morphology evolution of the interphase, creating a uniform and compact interphase. In addition, we find that the inclusion of an electrically insulating thin film, such as Al2O3, between the metal protection layer and the solid electrolyte favors lithium plating and prevents interphase formation over short periods of time. This dual layer approach also extends the electrochemical stability to more than 1000 h during cycling. However, using only the insulator without a metal is not beneficial for electrochemical stability. These results suggest that metallic protection layers may be necessary for attaining stable cycling even if suitable electrically insulating protection layers are developed to completely prevent interphase formation. Our findings are important for enabling the use of a wider range of solid electrolyte materials in solid-state batteries. [1] J.A. Lewis, et at. Interphase Morphology between a Solid-State Electrolyte and Lithium Controls Cell Failure. ACS Energy Lett. 2019, 4, 2, 591-599

Spark Plasma Sintering of Lithium Aluminum Germanium Phosphate Solid Electrolyte and its Electrochemical Properties.

Sodium superionic conductor (NASICON)-type lithium aluminum germanium phosphate (LAGP) has attracted increasing attention as a solid electrolyte for all-solid-state lithium-ion batteries (ASSLIBs), due to the good ionic conductivity and highly stable interface with Li metal. However, it still remains challenging to achieve high density and good ionic conductivity in LAGP pellets by using conventional sintering methods, because they required high temperatures (>800 °C) and long sintering time (>6 h), which could cause the loss of lithium, the formation of impurity phases, and thus the reduction of ionic conductivity. Herein, we report the utilization of a spark plasma sintering (SPS) method to synthesize LAGP pellets with a density of 3.477 g cm−3, a relative high density up to 97.6%, and a good ionic conductivity of 3.29 × 10−4 S cm−1. In contrast to the dry-pressing process followed with high-temperature annealing, the optimized SPS process only required a low operating temperature of 650 °C and short sintering time of 10 min. Despite the least energy and short time consumption, the SPS approach could still achieve LAGP pellets with high density, little voids and cracks, intimate grain–grain boundary, and high ionic conductivity. These advantages suggest the great potential of SPS as a fabrication technique for preparing solid electrolytes and composite electrodes used in ASSLIBs.

Novel L AGP − PEI Composite Electrolyte

Solid electrolytes (SE) have major advantages as an alternative to liquid electrolytes, in terms of reliability, safety, and easy design. SEs are generally defined as electronically insulating solid materials with high mobility and selective transport of charged ionic species within their structure. In general, they can be divided into two main categories: polymeric and inorganic. In this study we focus on the development of a novel composite Li1.5Al0.5Ge1.5(PO4)3 – Polyethyleneimine (LAGP−PEI) polymer-in-ceramic electrolyte, which contains high concentrations of ionic charge carriers with a minimal polymer concentration. Commercial nanoparticles of lithium aluminum germanium phosphate (Li1.5Al0.5Ge1.5(PO4)3, LAGP) were used as a ceramic matrix. Polyethyleneimine (PEI) was tested as a binder and lithium-ion-conducting medium. The combination of nanosize LAGP glass ceramics and PEI polymer was chosen to provide mechanical flexibility with the benefit of the high ionic conductivity of LAGP. The composite electrolytes were prepared by electrophoretic deposition (EPD). TGA, DSC, XRD, ESEM, NMR and EIS tests were used for the characterization of the samples. The dielectric properties of pristine LAGP and LAGP-based quasi-solid electrolytes, containing different concentrations of LiTFSI-based Pyr14 ionic liquid ions, were studied with the use of the BDS 80 (NOVOCONTROL) with automatic temperature control by a QUATRO Cryosystem. The complex, non-Debye dielectric response of the composite electrolyte has been described in terms of several distributed relaxation processes separated by different frequency and temperature ranges. While at low temperatures, the main contribution is from LAGP, at the middle- and high-temperature regions, the superposition of a few non-Arrhenius processes is observed. 7Li diffusion of the composite electrolyte measured by NMR at 90°C was about 6±2 E-11 m2/s. The correlation of ion-transport phenomena with XRD, DSC and ESEM data will be presented in detail. Acknowledgements The research was funded by the Israel Ministry of Science and Technology, grant 53886 and by the Israel Science Foundation (INREP project).

Stabilizing Solid Electrolyte-Anode Interface in Li-Metal Batteries by Boron Nitride-Based Nanocomposite Coating

Summary Solid-state Li-metal batteries are promising to improve both safety and energy density compared to conventional Li-ion batteries. However, various high-performance and low-cost solid electrolytes are incompatible with Li, which is indispensable for enhancing energy density. Here, we utilize a chemically inert and mechanically robust boron nitride (BN) film as the interfacial protection to preclude the reduction of Li1.3Al0.3Ti1.7(PO4)3 (LATP) solid electrolyte by Li, which is validated by in situ transmission electron microscopy. When combined with ∼1–2 μm PEO polymer electrolyte at the Li/BN interface, Li/Li symmetric cells show a cycle life of over 500 h at 0.3 mA·cm−2. In contrast, the same configuration with bare LATP dies after 81 h. The LiFePO4/LATP/BN/PEO/Li solid-state batteries show high capacity retention of 96.6% after 500 cycles. This study offers a general strategy to protect solid electrolytes that are unstable against Li and opens possibilities for adopting them in solid-state Li-metal batteries.