Lithium Aluminum Germanium Phosphate Research Articles

Hybrid Solid Electrolyte Composed of Lithium Aluminum Germanium Phosphate and Poly(ethylene oxide) for All Solid-State Lithium Batteries

Lithium-ion batteries have rapidly become the dominant power sources for portable electronic devices and electric vehicles, due to their high energy density and long cycle life [1,2].However, safety issues still prevent full utilization of these batteries owing to the use of flammable liquid electrolytes, and safety problems have become a significant concern especially in large capacity applications such as electric vehicles and energy storage systems. In this respect, fabrication of all solid-state lithium batteries by using solid electrolytes may give a fundamental solution for the safety issue of lithium batteries [3,4]. Glass ceramic electrolytes present potential advantages, such as absence of electrolyte leakage, large electrochemical stability window, absence of problems relating to vaporization of organic solvents and high thermal stability. However, sheet manufacturing, especially using thin-film technologies for making large-scale batteries, is considered to be difficult because of hard and brittle ceramic materials. In this work, solvent-free hybrid solid electrolytes composed of lithium aluminum germanium phosphate and poly(ethylene oxide) (PEO) were prepared in the form of flexible film, and their electrochemical characteristics were investigated. Their morphological properties were examined using SEM, EDS and XRD. The ionic conductivities and electrochemical stability of hybrid solid electrolytes were much higher than those of PEO-based polymer electrolyte. The optimized hybrid solid electrolyte was applied to the solid-state Li/LiFePO4 cell, and its electrochemical performance was evaluated.

All Solid-State Lithium Batteries Assembled with Hybrid Solid Electrolytes

Lithium-ion batteries have rapidly become the dominant power sources for portable electronic devices, electric vehicles and energy storage systems, due to their high energy density and long cycle life [1,2]. However, safety issues still prevent full utilization of these batteries. One of the most efficient methods to enhance the battery safety is to use solid electrolyte [3-5]. Solid inorganic electrolytes present potential advantages, such as a wide electrochemical stability window, enhanced thermal stability, absence of solvent leakage and high resistance to shocks, which are important safety assets. However, sheet manufacturing, especially using thin-film technologies for making large-scale batteries, is considered to be difficult because of brittle characteristics of ceramic materials. In this work, the hybrid solid electrolytes composed of lithium aluminum germanium phosphate (LAGP) and poly(ethylene oxide)(PEO) were prepared in the form of flexible thin film, and their electrochemical properties were investigated. Their morphological properties studied using SEM, EDS and XRD. The ionic conductivities and electrochemical stability of hybrid solid electrolytes were much higher than those of PEO-based polymer electrolyte. All solid-state lithium batteries assembled with hybrid solid electrolyte exhibited high discharge capacity and excellent capacity retention with a coulombic efficiency exceeding 99.5% at 55 oC.

Study on effect of poly (ethylene oxide) addition and in-situ porosity generation on poly (vinylidene fluoride)-glass ceramic composite membranes for lithium polymer batteries

The effect of blending polyethylene oxide with poly (vinylidene fluoride)–lithium aluminum germanium phosphate (LAGP) composite and in-situ porosity generation on the electrochemical performance of polymer electrolytes based on non-woven fibrous mats is studied. Electrospinning process parameters are controlled to get a fibrous membrane consisting of bead-free, multilayered, three dimensional network structure of ultrafine fibers. The electrospun membranes are subjected to a preferential polymer dissolution process to prepare a highly porous structure. The membranes show high surface roughness with uniformly sized and distributed pores on the fibers. The membranes with good mechanical strength, thermal stability and high porosity exhibit high swelling when activated with liquid electrolyte. The prepared composite polymer electrolytes show high ionic conductivity. The addition of the glass ceramic improves the mechanical and thermal stability, while blending and in-situ porosity generation improves the ionic conductivity, charge–discharge performance, cycling stability, interface properties and compatibility with lithium electrode.

Effect of annealing on properties of lithium aluminum germanium phosphate electrolyte thick films prepared by aerosol deposition

Li1.5[Al0.5Ge1.5(PO4)3] glass-ceramic powder was used for the deposition of thick films on silicon substrate by aerosol deposition. The deposited films were annealed at 873 K and 1023 K for 6 h in air. The thickness of the films was 10–12 m and the relative density was 78%–82%. As-deposited films had nano-scale grains and amorphous regions while in the annealed films, the grain growth and improved crystallinity were observed. The grain size was increased from 12 nm to 25 nm and 97 nm after annealing at 873 K and 1023 K, respectively. The ionic conductivity of the as-deposited film was 8.49 × 10−9 S cm−1, which increased to 1.06 × 10−5 S cm−1 and 1.16 × 10−4 S cm−1 after annealing at 873 K and 1023 K, respectively. The increased ionic conductivity is explained in terms of the increased grain size as well as the improved crystallinity.

Mesoporous Nitrogen‐Doped Carbon‐LiSICON Glass Ceramics as High Performance Cathodes in Solid‐State Lithium–Oxygen Batteries

Power trip! A new composite cathode for lithium–oxygen batteries is developed by using a highly mesoporous nitrogen-doped carbon blend and 20 wt % lithium aluminum germanium phosphate. This composite exhibits excellent electrochemical activity for oxygen reduction. The lithium–oxygen cell performance is an order of magnitude higher than that of cells with cathodes fabricated by using only carbon.

Crystallization kinetics of lithium aluminum germanium phosphate glass by DSC technique

The crystallization kinetics of Li2O-Al2O3-GeO2-P2O5 (LAGP) glass fabricated via the conventional melt-quenching method was studied by differential scanning calorimetry (DSC) under nonisothermal condition at different heating rates. The activation energy of glass transition Eg is 634.4 kJ/mol, indicating that LAGP glass is easy to crystallize at an elevated temperature. The activation energy of crystallization Ec and Avrami index n obtained from Matusita’s model are 442.01 kJ/mol and 1.7, respectively. The value of n reveals that bulk crystallization predominates slightly over surface crystallization during crystallization process. LAGP glass-ceramics after different heat treatments have the same crystalline phases determined as major phase LiGe2(PO4)3, with AlPO4 and GeO2 as their impurity phases.

Mesoporous Nitrogen-Doped Carbon-Glass Ceramic Cathodes for Solid-State Lithium–Oxygen Batteries

The composite of nitrogen-doped carbon (N-C) blend with lithium aluminum germanium phosphate (LAGP) was studied as cathode material in a solid-state lithium-oxygen cell. Composite electrodes exhibit high electrochemical activity toward oxygen reduction. Compared to the cell capacity of N-C blend cathode, N-C/LAGP composite cathode exhibits six times higher discharge cell capacity. A significant enhancement in cell capacity is attributed to higher electrocatalytic activity and fast lithium ion conduction ability of LAGP in the cathode.

Influence of Al 2O 3 additions on crystallization mechanism and conductivity of Li 2O–Ge 2O–P 2O 5 glass–ceramics

The crystallization mechanism and conductivity of lithium aluminum germanium phosphate [LAGP] glass–ceramics fabricated from Li 1+ x Al x Ge 2− x (PO 4) 3 ( x=0.0–0.7) glass system were investigated as a function of Al 2O 3 additions. A non-isothermal analysis was performed to study the crystallization behavior of LAGP glass–ceramics at various heating rates (5–25K min −1) by the Kissinger equation and the Augis–Bennett equation, illustrating volume crystallization for the glass-ceramics. The crystal identification and microstructure in glass–ceramics containing various Al 2O 3 contents were analyzed by means of XRD and FESEM. The main phase of the glass–ceramics was found to be LiGe 2(PO 4) 3, with AlPO 4 as the impurity phase. Additionally the highest total ionic conductivity (5.8×10 −4 S/cm) at room temperature was obtained when x=0.5 for Li 1+ x Al x Ge 2− x (PO 4) 3 ( x=0.0–0.7) glass–ceramics, suggesting that it was a promising electrolyte for practical application in all-solid-state lithium batteries.

Lisicon Glass-Ceramics Mediated Catalysis of Oxygen Reduction

Abstract : The role of lithium aluminum germanium phosphate (LAGP) glass-ceramic (a lisicon structure) on catalysis of the oxygen reduction reaction (ORR) is investigated by conducting thermo gravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) and cyclic voltammetry (CV) measurements. The analysis of the CV data reveals that the LAGP glass-ceramic possesses some inherent catalytic activity toward reduction of oxygen. However, the data also suggest an irreversible nature of the reaction. The TGA and BET data complement the CV results. The Lisicon family of materials appears to be an attractive catalyst for ORR.

Cathodes for Solid-State Lithium–Oxygen Cells: Roles of Nasicon Glass-Ceramics

The roles of lithium aluminum germanium phosphate (LAGP) glass-ceramic (GC) in cathodes of totally solid-state lithium–oxygen electrochemical cells are delineated by conducting discharge experiments as a function of cathode chemistry. It is proposed that LAGP possesses an inherent characteristic to adsorb oxygen molecules due to its open structure. The adsorption is followed by reduction of oxygen to superoxide and peroxide molecules. Subsequently, these molecules react with lithium ions to form respective discharge products. In addition to being an important constituent of the cathode, the LAGP also serves as a solid-state electrolyte membrane due to its superionic lithium-ion conductivity. The dual functions of the LAGP GCs make it a feasible material to process an integrated membrane–cathode element of a cell, although this is not demonstrated in this paper.

The effects of crystallization parameters on the ionic conductivity of a lithium aluminum germanium phosphate glass–ceramic

This paper reports on a relationship between the conductivity and crystallization parameters (time and temperature) of a lithium aluminum germanium phosphate (LAGP) glass–ceramic. To study the relationship, a specific formulation of the LAGP [Li 1+ x Al x Ge 2− x (PO 4) 3 ( x = 0.5)] glass was chosen. The glass was crystallized at different temperatures and times and it was characterized for microstructures and ionic conductivity. The highest total conductivity of the glass–ceramic material, 4.22 × 10 −3 S cm −1 at 27 °C, was obtained by crystallizing the glass at 825 °C for 8 h. The superionic conductivity in the specimens is attributed to the space charge-mediated effect resulting from the presence of the dielectric phase (AlPO 4). The impurity phase AlPO 4 imparted a characteristic non-linearity in the Arrhenius plots. A decrease in conductivity with an increase in crystallization temperature and time was observed. The observed conductivity was explained on the basis of the blocking effect resulting from an increased concentration or size of the impurity phase, AlPO 4. The thermally unstable nature of the LAGP is reflected by the relationship between the conductivity and the crystallization parameters. Conductivity of the glass–ceramic is believed to be significantly affected by the space charge and blocking effects that originate from and relate to the crystallization temperature and time.

Space-Charge-Mediated Superionic Transport in Lithium Ion Conducting Glass–Ceramics

This paper describes an investigation of the properties of superionic glass–ceramic specimens synthesized from the lithium–aluminum–germanium–phosphate system. The specimens were characterized using differential scanning calorimetry, X-ray diffraction, scanning electron microscopy, and impedance spectroscopy. The concentration of lithium oxide in the glass–ceramic formulations was the primary variable investigated. It is shown that the ionic conductivity of the specimens was dependent on the lithium oxide concentration. An optimized composition exhibited a conductivity approaching at around room temperature. The superionic conductivity in these specimens is attributed to the space-charge-mediated effect resulting from the presence of the dielectric phase. The specimens also displayed different conductivities during heating and cooling scans, referred to in this paper as hysteresis effect.

Superionic Conductivity in a Lithium Aluminum Germanium Phosphate Glass–Ceramic

In this paper, processing and characterization of sheet, pellet, and membrane specimens based on the lithium aluminum germanium phosphate (LAGP) glass–ceramic system is reported. X-ray diffraction patterns exhibited the presence of as the primary phase. Increasing heat-treatment temperature from led to the precipitation of an impurity phase, , and a large increase in LAGP grain size. The highest total conductivity of the LAGP glass–ceramic material at was obtained by crystallizing the glass sheet at for . The total conductivity of the specimen was in the range of in the temperature range. The pelletized specimen prepared from the glass–ceramic powder and sintered at for exhibited a slightly lower conductivity at . The membrane conductivity was above in the temperature range. High grain boundary conductivity is apparent in the LAGP glass-ceramic materials. The impurity phases and were attributed to a characteristic nonlinearity in the Arrhenius plots and mediated the transport of the lithium ion, which is associated with a higher activation energy.

Composite effect in superionically conducting lithium aluminium germanium phosphate based glass-ceramic

Superionically conducting lithium aluminum germanium phosphate (LAGP) glass-ceramic and barium strontium titanate, Ba 0.6Sr 0.4TiO 3 (0.6BST)-doped specimens were processed and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and AC impedance techniques. The XRD patterns exhibited the existence of LiGe 2(PO 4) 3 as the primary phase with impurity phases AlPO 4 and Li 2O. SEM images revealed the presence of large LAGP crystals. The highest conductivity (5.08 × 10 −3 S cm −1) at 27 °C was obtained for the glass-ceramic sheet specimen crystallized at 850 °C for 12 h. Pelletized specimens prepared from the glass-ceramic powder and sintered at 850 °C for 9 h exhibited a slightly lower conductivity (4.62 × 10 −3 S cm −1) at 27 °C. The nonlinearity in the Arrhenius plots of total conductivity was attributed to the impurity phases, AlPO 4 and Li 2O and mediated the transport of lithium ion which is associated with higher activation energy. Doping of dielectric 0.6BST to the LAGP led to the shifting of the temperature of inflection towards the higher temperature in the Arrhenius plot of total conductivity and enhanced the space charge effect.