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We have been conducting research to explore new materials and their use in batteries by pursuing the phenomenon of high ion diffusion in solids. Lithium ion conducting materials have been particularly explored because of their potential application to all-solid-state batteries with high energy density. In addition to an overview of lithium ionic conductors, we will review the material search process for Li10GeP2S12, which exhibits particularly high ionic conductivity. We will also review the research that clarified the formation region of this material, investigated the ionic conduction mechanism, and applied this material to all-solid-state batteries. [ABSTRACT FROM AUTHOR]

In the study of lithium‐sulfur batteries, the shuttle effect of polysulfide ions is widely regarded as the most critical factor in the battery performance deterioration. In this article, with the strategy of ion‐selection, a method of preparing a coating layer with solid‐phase conduction for a separator was used to suppress such an effect. The coating layer was based on calcined ceramic Li7La3Zr2O12 (LLZO) and formed through a simple coating method to be thin but dense. The gap between particles was filled with lithiated Nafion (Li‐Nafion) which could block polysulfide ions through coulombic interactions of sulfonate groups and allowed the lithium ion conduction. The properties of compactness and the ion‐selection formed a double barrier effect, manifested as the fact that the estimated lithium ion transport number achieved 0.79. Correspondingly, the lithium‐sulfur batteries assembled with the ion‐selective conduction separators had better lithium deposition behavior and exhibit brilliant cycling performances and capacity retention. [ABSTRACT FROM AUTHOR]

• Crystallization of Li 4x Mg 2 (1-x)P 2 O 7 glass shows an X-ray diffraction pattern similar to Li 2 ZnP 2 O 7 at the crystallization onset temperature. • Crystals similar to Li 2 ZnP 2 O 7 are metastable at the crystallization onset temperatures of glass. • The density difference between glass and crystal affects crack formation and ionic conductivity. • Heat treatment at the crystallization onset temperature shows surface crystallization tendency. In the Li 2 O-MgO-ZnO-P 2 O 5 system, glasses based on the LiMgP 2 O 7 composition were synthesized using the melt-quenching method, specifically focusing on two series: Li 4 x Mg 2(1- x) P 2 O 7 and Li 2 Zn y Mg (1- y) P 2 O 7. Li 2 MgP 2 O 7 (33.3mol% Li 2 O, 33.3mol% MgO, 33.3mol% P 2 O 5) showed an X-ray diffraction pattern similar to Li 2 ZnP 2 O 7 (LZPO) when heat-treated near its crystallization onset temperature, as determined by differential thermal analysis (DTA). However, at 700 °C, thermal decomposition into multiple phases, including Li 4 P 2 O 7 , was observed. In the Li 4 x Mg 2(1- x) P 2 O 7 glass series, LZPO-type crystals formed in the range of x = 0.5 to 0.75. The quasi-binary system of Li 2 MgP 2 O 7 and Li 2 ZnP 2 O 7 , represented by Li 2 Zn y Mg (1- y) P 2 O 7 , formed glasses across all compositions. These glasses formed LZPO-type crystals showing lithium-ion conductivity at the crystallization onset temperature. A surface crystallization tendency was confirmed where crystals grew from the surface towards the interior of the glass substrate. [ABSTRACT FROM AUTHOR]

Amorphous materials (a-LAGP(x = 0.5)) with the composition of Li1.5Al0.5Ge1.5(PO4)3 were prepared by mechanochemical synthesis method. Crystalline compounds with LiGe2(PO4)3-based NASICON-type structure were formed by heat treatment of a-LAGP(x = 0.5) at 400–700 °C in air. Solid electrolytes prepared by the heat treatment of pelletized-type a-LAGP(x = 0.5) and MgO-modified a-LAGP(x = 0.5) at 700 °C exhibited the lithium ion conductivities on the order of 10−5–10−4 S cm−1 at room temperature. The addition of MgO into a-LAGP(x = 0.5) increased the electrical conductivity. Lithium ion conductors prepared by low-temperature heat treatment of pelletized-type amorphous materials in the Li2O-Al2O3-GeO2-P2O5 system would be promising as solid electrolytes for all-solid-state batteries.

In this research, new lithium ion conductor glass-ceramics with NASICON-type structure (Li1+x+yAlxCryGe2-x-y (PO4)3, x+y=0.5) were synthesized using melt-quenching method and converted to glass-ceramics through heat treatment. Influence of addition of different concentrations of aluminum and chromium in LiGe2(PO4)3 glass-ceramic was investigated for ionic conduction improvement. Substitution of Ge4+ ions in NASICON structure by Al3+ and Cr3+ ions induced more Li+ ions in A2 vacant sites to obtain charge balance and also changed the unit cell parameters. These two factors led to ionic conductivity improvement of synthesized glass-ceramics. The glass-ceramics were characterized and the amorth structures were investigated by X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Energy-Dispersive X-ray spectroscopy (EDX), Differential Scanning Calorimetry (DSC) and Complex Impedance Spectroscopy (CIS). The highest lithium ion conductivity of 8.82×10-3 S/cm was obtained for x=0.4 and y=0.1 (Li1.5Al0.4Cr0.1Ge1.5(PO4)3) crystallized at 850 oC for 8 h with minimum activation energy of 0.267 eV.

Hydrogen as an energy carrier is very versatile in energy storage applications. Developments in novel, sustainable technologies towards a CO2-free society are needed and the exploration of all-solid-state batteries (ASSBs) as well as solid-state hydrogen storage applications based on metal hydrides can provide solutions for such technologies. However, there are still many technical challenges for both hydrogen storage material and ASSBs related to designing low-cost materials with low-environmental impact. The current materials considered for all-solid-state batteries should have high conductivities for Na+, Mg2+ and Ca2+, while Al3+-based compounds are often marginalised due to the lack of suitable electrode and electrolyte materials. In hydrogen storage materials, the sluggish kinetic behaviour of solid-state hydride materials is one of the key constraints that limit their practical uses. Therefore, it is necessary to overcome the kinetic issues of hydride materials before discussing and considering them on the system level. This review summarizes the achievements of the Marie Skłodowska-Curie Actions (MSCA) innovative training network (ITN) ECOSTORE, the aim of which was the investigation of different aspects of (complex) metal hydride materials. Advances in battery and hydrogen storage materials for the efficient and compact storage of renewable energy production are discussed.

Abstract: Single‐crystal rods of Li6.5La3Zr1.5Ta0.5O12 were grown by floating zone melting. The typical size of the single‐crystal rod was 8 mm in diameter and 70 mm in length. Li6.5La3Zr1.5Ta0.5O12 crystallizes in a cubic structure with an Ia‐3d space group and the lattice parameter a=12.9455 (6) Å. The crystal structure of Li6.5La3Zr1.5Ta0.5O12 was refined to the conventional values of R=3.32 % and wR=4.45 % using single‐crystal X‐ray diffraction data, and to R=8.82 % and wR=7.45 % using single‐crystal neutron diffraction data. Li‐ions in the crystal structure occupied two crystallographic sites: the distorted tetrahedral 96 h site and the distorted octahedral 96 h site. Analyzing the results of AC impedance measurements, we estimated the total Li‐ion conductivity of member in Li6.5La3Zr1.5Ta0.5O12 to be 1.27×10−3 S cm−1 at 298 K. This value is the highest in the reported Li6.5La3Zr1.5Ta0.5O12 members. Using NMR spectroscopy, we determined the Li diffusion coefficient to be 1.57×10−13 m2 s−1 at 298 K and 7.96×10−13 m2 s−1 at 333 K. These values related to Li‐ion migration are higher than those reported for polycrystalline samples. [ABSTRACT FROM AUTHOR]

In the present work, the dominant Li+ conduction in 6 mol% LiI-doped KI-KBH4 solid solvent was verified by electrochemical measurement and time-of-flight secondary ion mass spectrometry (TOF-SIMS). After the potentiostatic reduction of the cell Li | KI-KBH4-LiI | Mo at − 0.5 V vs Li+/Li, the deposition of Li metal on the surface of Mo electrode was confirmed by TOF-SIMS measurement. A pair of reduction and oxidation currents are clearly observed at 0 V vs Li+/Li in a cyclic voltammogram of the cell Li | KI-KBH4-LiI | Mo, which is a direct indication for Li+ ion conduction in the KI-KBH4 solid solvent system. From the results of AC impedance measurement of KI-KBH4-LiI, the bulk resistance was mainly observed while the solid electrolyte was pelletized only by uniaxial pressing. The dense microstructure of the pellet supports the results of impedance measurement where the contribution of grain boundary resistance was not observed. The extreme plastic property of the Li+ ion conductor based on KI-KBH4 will allow the interfaces between the solid electrolytes and electrode active materials to be adhered closely. [ABSTRACT FROM AUTHOR]

Abstract: Complex hydrides have played important roles in energy storage area. Here a complex hydride made of Li2NH and LiBH4 was synthesized, which has a structure tentatively indexed using an orthorhombic cell with a space group of Pna21 and lattice parameters of a=10.121, b=6.997, and c=11.457 Å. The Li2NH‐LiBH4 sample (in a molar ratio of 1:1) shows excellent hydrogenation kinetics, starting to absorb H2 at 310 K, which is more than 100 K lower than that of pristine Li2NH. Furthermore, the Li+ ion conductivity of the Li2NH‐LiBH4 sample is about 1.0×10−5 S cm−1 at room temperature, and is higher than that of either Li2NH or LiBH4 at 373 K. Those unique properties of the Li2NH‐LiBH4 complex render it a promising candidate for hydrogen storage and Li ion conduction. [ABSTRACT FROM AUTHOR]

This study investigated the conductivity of lithium ions in new pyrochlore materials. A two-step synthesis method, comprising a simple solid-state reaction followed by a high-pressure solid-state reaction was used to synthesize single-phase undoped LiSrB2O6F (where B = Nb5+ or Ta5+). The samples were doped with the lower valent cation, Zr4+, which replaced Nb5+ or Ta5+ at B-sites in LiSrB2O6F and similarly, A-site point defects were introduced by reducing the amount of Sr in the sample. The crystal structure was determined by Rietveld analysis of the X-ray synchrotron diffraction data. Ionic conductivities of the samples were evaluated using electrochemical impedance spectroscopy. Sr2+ deficient samples showed better conductivity (8.21 × 10−6 S cm−1 for Nb-containing samples and 6.38 × 10−6 S cm−1 for Ta-containing samples at 300°C) than that of Zr4+-doped samples (5.58 × 10−6 S cm−1 for Nb-containing samples and 3.58 × 10−6 S cm−1 for Ta-containing samples at 300°C). [ABSTRACT FROM AUTHOR]

The ternary oxide glasses in the system of Li 3 BO 3 -Li 2 SO 4 -Li 2 CO 3 were prepared by mechanical milling. By heating the glasses to crystallize, the glass-ceramics were obtained. The 90Li 3 BO 3 ·7Li 2 SO 4 ·3Li 2 CO 3 (mol%) glass-ceramic electrolyte showed the conductivity of 1.0 × 10 − 5 S cm − 1 at room temperature, which was higher than that of the 90Li 3 BO 3 ·10Li 2 SO 4 glass-ceramic electrolyte. At the 33Li 3 BO 3 ·33Li 2 SO 4 ·33Li 2 CO 3 composition, a cold-pressed pellet at 720 MPa of the glass exhibited excellent formability with the relative density of 90%, which was comparable to that of sulfide glass electrolytes. By heating the glass, a metastable phase was precipitated and the glass-ceramic exhibited the conductivity of 1.8 × 10 − 6 S cm − 1 at room temperature. To obtain a denser pellet, hot-pressing at around its glass-transition temperature and consecutive crystallization were conducted. The hot-pressed pellet of the glass-ceramic was transparent and showed the conductivity of 2.3 × 10 − 6 S cm − 1 at room temperature. From the ultrasonic pulse-echo measurement, the bulk modulus of the glass was 44 GPa, which was lower than that of 68 GPa of the 90Li 3 BO 3 ·10Li 2 SO 4 glass. From the galvanostatic cycling test, the 33Li 3 BO 3 ·33Li 2 SO 4 ·33Li 2 CO 3 glass-ceramic electrolyte was kinetically stable against lithium metal negative electrode. The 33Li 3 BO 3 ·33Li 2 SO 4 ·33Li 2 CO 3 glass-ceramic electrolyte is therefore a promising material with both conductivity and ductility for the application to all-solid-state batteries. [ABSTRACT FROM AUTHOR]

Advanced techniques for overcoming problems encountered during in situ electron holography experiments in which a voltage is applied to an ionic conductor are reported. The three major problems encountered were 1) electric-field leakage from the specimen and its effect on phase images, 2) high electron conductivity of damage layers formed by the focused ion beam method, and 3) chemical reaction of the specimen with air. The first problem was overcome by comparing experimental phase distributions with simulated images in which three-dimensional leakage fields were taken into account, the second by removing the damage layers using a low-energy narrow Ar ion beam, and the third by developing an air-tight biasing specimen holder. [ABSTRACT FROM AUTHOR]

In this research, new lithium ion conductor glass-ceramics with NASICON-type structure (Li1+x+yAlxCryGe2-x-y (PO4)3, x+y=0.5) were synthesized using melt-quenching method and converted to glass-ceramics through heat treatment. Influence of addition of different concentrations of aluminum and chromium in LiGe2(PO4)3 glass-ceramic was investigated for ionic conduction improvement. Substitution of Ge4+ ions in NASICON structure by Al3+ and Cr3+ ions induced more Li+ ions in A2 vacant sites to obtain charge balance and also changed the unit cell parameters. These two factors led to ionic conductivity improvement of synthesized glass-ceramics. The glass-ceramics were characterized and the amorth structures were investigated by X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Energy-Dispersive X-ray spectroscopy (EDX), Differential Scanning Calorimetry (DSC) and Complex Impedance Spectroscopy (CIS). The highest lithium ion conductivity of 8.82×10-3 S/cm was obtained for x=0.4 and y=0.1 (Li1.5Al0.4Cr0.1Ge1.5(PO4)3) crystallized at 850 oC for 8 h with minimum activation energy of 0.267 eV. [ABSTRACT FROM AUTHOR]

The novel lithium-ion conductor Li 7 Ge 3 PS 12 was synthesized by slow cooling from the ternary Li 2 S–GeS 2 –P 2 S 5 system, and was shown to exhibit a cubic argyrodite-type structure. The phase composition was determined by varying the ratio of starting materials; the observed monophasic properties were close to those for the Li 7 Ge 3 PS 12 composition. The lattice parameter ( a =9.80192(3) Å) of Li 7 Ge 3 PS 12 was slightly smaller than that of Li 7 PS 6 ( a =9.993 Å), indicating that substitution of a Li cation by the smaller Ge cation contracted the cubic lattice. In addition, the novel structure consisted of a framework composed of four isolated (Ge/P)S 4 tetrahedra. Li + ions occupied tetrahedral sites within the framework, forming a three-dimensional conduction pathway. Finally, Li 7 Ge 3 PS 12 exhibited a high ionic conductivity of 1.1×10 −4 S cm −1 at 25 °C and an activation energy of 25 kJ mol −1 . [ABSTRACT FROM AUTHOR]

It is widely recognized that Al plays a dual role in the fabrication of garnet-type solid electrolytes, i.e., as a dopant that stabilizes the cubic structure and a sintering aid that facilitates the densification. However, the sintering effect of Al 2 O 3 has not been well understood so far because Al is typically “unintentionally” introduced into the sample from the crucible during the fabrication process. In this study, we have investigated the sintering effect of Al on the phase composition, microstructure, and ionic conductivity of Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 by using an Al-free crucible and intentionally adding various amounts of γ-Al 2 O 3 . It was found that the densification of Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 occurred via liquid-phase sintering, with evidence of morphology change among different compositions. Among all of the compositions, samples with 0.05 mol Al per unit formula of garnet oxide (i.e., 0.3 wt% Al 2 O 3 ) exhibited the optimal microstructure and the highest total ionic conductivity of 5 × 10 − 4 S cm − 1 at room temperature. [ABSTRACT FROM AUTHOR]

Thin films of crack-free lithium ionic conductive LiAlTi (PO) (LATP) solid electrolyte could be fabricated by a modified Pechini-type polymeric precursor method with controlled amount of citric acid (CA), pH, and viscosity of precursor at low temperatures between 600 and 700 °C. It turned out that the increase in molar ratio of citric acid to total metal salts ( M) in the precursor gave drastic change of thermal reactions and crack-free LATP thin films could be obtained from the precursor with CA/ M = 5. In addition, the formation of LATP crystal phase required the viscosities more than 0.100 Pa s. It was also found that the pH control of the coating solutions was a key step to obtain homogeneous thin films. FT-IR measurements revealed that the change of pH in the precursors gave structural changes in precursor complexes. The LATP thin film of 200 nm in thickness prepared from the solution at CA/ M = 5, 0.100 Pa s, and pH = ca. 10, sintered at 650 °C showed an ionic conductivity of ca. 0.029 S/cm at 300 °C. Graphical Abstract: [ABSTRACT FROM AUTHOR]

For the lithium super-ionic conductor Li 10 GeP 2 S 12 , the partial substitution of sulfur by oxygen is achieved via a solid-state reaction. The solid-solution range of oxygen is found to be 0 ≤ x < 0.9 in Li 10 GeP 2 S 12− x O x . Structure refinements using synchrotron X-ray diffraction data confirm the preference for oxygen substitution in the PS 4 tetrahedra. The local structural change in the P(S/O) 4 tetrahedra upon substitution is also indicated by Raman spectroscopy. Ionic conduction properties are maintained even after the oxygen substitution in Li 10 GeP 2 S 12 ; the ionic conductivity of Li 10 GeP 2 S 12− x O x (0.3 ≤ x ≤ 0.6) ranges from 1.03 × 10 −2 to 8.43 × 10 −3 S cm −1 at 298 K. No redox current is observed by cyclic voltammetry from nearly 0 to 10 V versus Li/Li + except for that due to the lithium deposition/dissolution reactions. All-solid-state batteries using Li 10 GeP 2 S 12− x O x ( x = 0.3 and 0.6) as solid electrolytes with Li metal anodes show discharge capacities exceeding 100 mAh g −1 and better cycling performance compared to batteries using the original Li 10 GeP 2 S 12 . The partial substitution of oxygen for sulfur in Li 10 GeP 2 S 12 affords a novel solid electrolyte, Li 10 GeP 2 S 12− x O x , with high conductive properties and electrochemical stability. [ABSTRACT FROM AUTHOR]

New high lithium ion conductor glass–ceramics with NASICON-type structure (Li 1 + x + y Al x Cr y Ge 2 − x − y (PO 4 ) 3 , x + y = 0.5) were synthesized using melt-quenching method and converted to glass–ceramics through heat treatment. Influence of addition of different concentrations of aluminum and chromium in LiGe 2 (PO 4 ) 3 glass-ceramic was investigated. Substitution of Ge 4 + ions by Al 3 + and Cr 3 + ions induced more Li + ions in A 2 vacant sites and also changed the unit cell parameters and resulted in ionic conductivity improvement of glass–ceramics. The glass–ceramics were characterized by X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Energy-Dispersive X-ray spectroscopy (EDX), Differential Scanning Calorimetry (DSC), Complex Impedance Spectroscopy (CIS) and cyclic voltammetry (CV). The highest lithium ion conductivity of 6.65 × 10 − 3 S/cm was obtained for x = 0.4 and y = 0.1 (Li 1.5 Al 0.4 Cr 0.1 Ge 1.5 (PO 4 ) 3 ) crystallized at 850 °C for 8 h with minimum activation energy of 0.292 eV. [ABSTRACT FROM AUTHOR]

Li-rich layered cathode Li[Li 0.2 Mn 0.54 Ni 0.13 Co 0.13 ]O 2 is prepared via a co-precipitation followed with high-temperature calcination, and then successfully modified with nano-Li 3 PO 4 by ball milling and annealing. The TEM and EDS reveal that Li 3 PO 4 is homogeneously coated on the particle surface of Li[Li 0.2 Mn 0.54 Ni 0.13 Co 0.13 ]O 2 . And the electrochemical performance of Li[Li 0.2 Mn 0.54 Ni 0.13 Co 0.13 ]O 2 is significantly improved by coating with lithium ion conductor Li 3 PO 4 . The Li 3 PO 4 -coated sample delivers a high initial discharge capacity of 284.7 mAhg −1 at 0.05 C, and retains 192.6 mAhg −1 after 100 cycles at 0.5 C, which is higher than that of the pristine sample (244 mAhg −1 at 0.05 C and 168.2 mAhg −1 after 100 cycles at 0.5 C). The electrochemical impedance spectroscopy (EIS) demonstrates that the resistance for Li/Li 3 PO 4 -coated Li[Li 0.2 Mn 0.54 Ni 0.13 Co 0.13 ]O 2 cell was reduced compared to Li/Li[Li 0.2 Mn 0.54 Ni 0.13 Co 0.13 ]O 2 , which indicates the Li 3 PO 4 coating layer with high ionic conductivity (6.6 × 10 −8 S cm −1 ) facilitates the diffusion of lithium ions through the interface between electrode and electrolyte and accelerates the charge transfer process. What is more, the Li 3 PO 4 coating layer can also act as a protection layer to protect the cathode material from encroachment of electrolyte. The two aspects account for the enhanced electrochemical performance of Li 3 PO 4 -coated Li[Li 0.2 Mn 0.54 Ni 0.13 Co 0.13 ]O 2 . [ABSTRACT FROM AUTHOR]

Novel lithium-ion (Li + )-conducting oxysulfides of the Li 10 GeP 2 S 12 family were found in the ternary Li 2 S–P 2 S 5 –P 2 O 5 system; Li 10 GeP 2 S 12 -type solid solutions with compositions Li 3 + 5 x P 1 − x S 4 − z O z ( x = 0.03–0.08, z = 0.4–0.8) were confirmed. The solid solutions showed ionic conductivities from 4.14 × 10 − 5 to 2.64 × 10 − 4 S cm − 1 at 298 K and a wide electrochemical window of 0–5.0 V ( vs. Li/Li + ). Among the solid solutions synthesized, the purest phase had the composition Li 3.35 P 0.93 S 3.5 O 0.5 ( x = 0.07, z = 0.5). Structural analysis revealed that the novel oxysulfides are isostructural to the original Li 10 GeP 2 S 12 structure and the (P/□)(S/O) 4 tetrahedra, which indicates the presence of cation defects with oxygen substitution in the crystal structure. Electrochemical stability of the oxysulfides was confirmed in the voltage range of 0–5.0 V. The solid-electrolyte interphase (SEI) resistivity and its cycle-dependence evaluation for new materials demonstrated that the oxysulfides had lower resistivities and furnished well-contacted SEI layers during the charge–discharge process. [ABSTRACT FROM AUTHOR]

A series of Li 1 + x Al x Zr 2-x (PO 4 ) 3 samples with varied amount of Al doping have been prepared using a solid state reaction method and the optimum doping amount of aluminum is determined as 0.6. All the doped samples showed an increased conductivity, which is attributed to the transformation of the triclinic phase to the rhombohedral phase and the density increasement upon doping of Al. By mixing powders calcined at two different temperatures (700 °C and 1100 °C), samples Li 1.6 Al 0.6 Zr 1.4 (PO 4 ) 3 with the optimum doping amount of Al have been made to study the effect of the mixed degrees of sintering. The overall conductivities of samples with mixed degrees of sintering are all improved and peaked at 20–30% of powders calcined at 700 °C. This improvement is thought to relate to the role of powders calcained at 700 °C, which acted as “bridges” to connect all the other well-defined grains together. [ABSTRACT FROM AUTHOR]

A novel molecular crystal, Li{N(SO 2 CF 3 ) 2 }(C 6 H 4 (OCH 3 ) 2 ) ( 1 ), was synthesized by heating LiTFSA with DMB in 1:1 molar ratio. Single crystal x-ray diffraction study of 1 revealed that the compound possesses a dinuclear structure with five-coordinate lithium centers bridged by TFSA anions. AC impedance measurements showed that ionic conduction through the crystallites of 1 takes place via a hopping mechanism at ambient temperature. [ABSTRACT FROM AUTHOR]

Solid solutions of the lithium ion conductor LaLiO 2 were synthesized using a solid-state reaction method. For the strontium-doped system, Sr 2 + was partially doped at the La sites with the composition La 1 − x Sr x Li 1 + x O 2 ( x = 0.1, 0.2), which introduced excess lithium into the structure, while for the magnesium-doped system, Mg 2 + was partially doped at the Li + site with LaLi 1 − 2 y Mg y O 2 ( y = 0.1, 0.2) which introduced Li + vacancies. The magnesium-doped sample with y = 0.1 in LaLi 1 − 2 y Mg y O 2 showed higher ionic conductivity of 9.22 × 10 − 5 S cm − 1 than that of the respective Sr doped sample of x = 0.1 in La 1 − x Sr x Li 1 + x O 2 (4.64 × 10 − 5 S cm − 1 ) at 300 °C. Higher ionic conductivity in the Mg doped system indicates that vacancies led to high lithium ion conduction in LaLiO 2 . The doped LaLiO 2 systems are a novel lithium conductive oxides family. [ABSTRACT FROM AUTHOR]

Lithium-sulfur batteries show fascinating potential for advanced energy system due to their high specific capacity, low-cost, and environmental benignity. However, their wide applications have been plagued by low coulombic efficiency, fast capacity fading and poor rate performance. Herein, a facile method for preparation of S@PDA (PDA = polydopamine) composites with core–shell structure and good electrochemical performance as well as the First-Principles calculations on the interactions of PDA and polysulfides are reported. Taking the advantages of the core–shell structure with porous sulfur core, the high mechanical flexibility of PDA for accommodating the volumetric variation during the discharge/charge processes, the good lithium ion conductivity and the strong chemical interactions between the nitrogen/oxygen atoms with lone electron pair and lithium polysulfides for alleviating their dissolution, the S@PDA composites exhibit high discharge capacities at different current densities (1048 and 869 mAh g −1 at 0.2 and 0.8 A g −1 , respectively) and excellent capacity retention capability. A capacity decay as low as 0.021% per cycle and an average coulombic efficiency of 98.5% is observed over a long-term cycling of 890 cycles at 0.8 A g −1 . The S@PDA electrode has great potential as a low-cost cathode in high energy Li–S batteries. [ABSTRACT FROM AUTHOR]

High lithium ion conductivity solid electrolytes of Li 1 + x Cr x Ti 2 − x (PO 4 ) 3 (x = 0–0.5) and Li 1.4 Al x Cr 0.4 − x Ti 1.6 (PO 4 ) 3 (x = 0–0.4) with the NASICON-type structure were synthesized using a precursor prepared by the sol–gel method. The highest total electrical conductivity of 3.55 × 10 − 4 S cm − 1 at 25 °C was obtained for x = 0.4 in Li 1 + x Cr x Ti 2 − x (PO 4 ) 3 (LACTP) sintered at 1120 °C for 6 h in air. Higher electrical conductivity was observed by the partial substitution of Cr 3 + with Al 3 + . The highest total electrical conductivity of 1.06 × 10 − 3 S cm − 1 and bulk conductivity of 1.77 × 10 − 3 S cm − 1 at 25 °C were obtained for x = 0.3 in Li 1.4 Al x Cr 0.4 − x Ti 1.6 (PO 4 ) 3 sintered at 1070 °C for 6 h in air. The contribution of electronic conductivity to the total conductivity was negligibly small. Li 1.4 Al 0.3 Cr 0.1 Ti 1.6 (PO 4 ) 3 was unstable in water, but stable in saturated LiOH with saturated LiCl aqueous solution. [ABSTRACT FROM AUTHOR]

Newly designed oxide glass–ceramic electrolyte of Li2.9B0.9S0.1O3.1 with high Li+ ion conductivity and low melting property was prepared by mechanical milling and subsequent heat treatment at 290 °C. This material showed 1.4 × 10−5 S cm−1 at room temperature and excellent deformation properties to obtain powder-compressed pellets with low interfacial resistance like in the case of sulfide solid electrolytes. The glass–ceramic exhibited favorable mechanical properties to form favorable solid–solid contacts in solid-state batteries by pressing without high temperature heat treatments. All-solid-state In/LiCoO2 cells using these oxide glass–ceramic electrolytes operated as secondary batteries at room temperature. [ABSTRACT FROM AUTHOR]

Abstract: We investigated the development of a novel lithium garnet-type oxide electrolyte, which is co-sinterable with a metal oxide cathode, for practical all-solid-state lithium ion batteries using metal oxide electrolytes. The sintering temperature of Li6.8(La2.95,Ca0.05)(Zr1.75,Nb0.25)O12 was found to significantly lower to 790 °C by addition of Li3BO3 and Al2O3, due to simultaneous interdiffusion of Al and Ca elements between garnet-type oxide and additives. The sintered electrolyte exhibited high lithium ion conductivity of 0.36 mS cm−1 at 25 °C despite of the low sintering temperature. An all-solid-state lithium ion battery was successfully prepared by co-sintering of the electrolyte and LiCoO2 (cathode), followed by coating of Li metal (anode), and confirmed to function well as a secondary battery with charge and discharge capacities of 98 and 78 mAh g−1, respectively. These results opened the potential for fabrication of all-solid-state lithium ion batteries by a simple and well-established co-sintering process. [Copyright &y& Elsevier]

Abstract: A Li0.17La0.61TiO3(111)/LiMn2O4(111) solid electrolyte/electrode hetero-epitaxial system with applications in all solid-state batteries has been synthesized on a SrRuO3(111)/SrTiO3(111) substrate using pulsed laser deposition. XRD patterns provided evidence for the epitaxial growth of Li0.17La0.61TiO3(111) on LiMn2O4 at a low deposition temperature of 750°C. X-ray reflectivity analysis confirmed that the low temperature deposition resulted in intimate contact between LiMn2O4 and Li0.17La0.61TiO3, although small amounts of oxygen and titanium were found to have diffused between the materials. The Li0.17La0.61TiO3/LiMn2O4 film exhibited reversible electrochemical activity between 3.0 and 4.5V. No significant structural changes were observed in the cycled film, indicating that the Li0.17La0.61TiO3/LiMn2O4 interface is chemically and electrochemically stable during the battery reaction. The integration of electrode and solid electrolyte oxides in epitaxial multi-layer structures is expected to allow the design of new configurations for all solid-state batteries. [Copyright &y& Elsevier]

Phase stability of the Garnet-structured lithium ion conductor Li7La3Zr2O12 (LLZ) was investigated using high-temperature X-ray diffraction (HT-XRD). The tetragonal LLZ containing CO2 transformed to the cubic phase around 150°C. However, once the tetragonal LLZ heated up to 1000°C, the cubic phase transformed back to the tetragonal phase again, because of the CO2 loss during the heating process. After the CO2 loss, the phase transformation temperature shifted to 650°C. The HT-XRD study for Al-doping process was also performed. The addition of γ-Al2O3 to the tetragonal LLZ eliminated the formation of impurity phase such as La2Zr2O7 and La2O3, resulting in the formation of a pure cubic phase. A comparison of the HT-XRD results suggested that the Li loss is necessary to stabilize the cubic phase with Al. [ABSTRACT FROM AUTHOR]

Abstract: Al2O3 was doped (0.5, 1.0. and 2.0wt.%) into the garnet-type lithium ion-conducting solid electrolyte with a nominal composition of Li7La3Zr2O12 (LLZ) by solid state reaction at 1180°C. The effect of the Al2O3 content in LLZ on the interface behavior with lithium metal was investigated. The lowest interface resistance was observed for 0.5wt.% Al2O3-doped LLZ, which had the highest relative density of 93.7%. The Li/Al2O3-doped LLZ/Li cell showed a short circuit after a limited polarization period. Short circuiting is considered to be due to lithium dendrite formation. The longest period until short circuit was 1000s of polarization at 0.5mAcm−2 and room temperature for the 0.5wt.% Al2O3 doped LLZ. [Copyright &y& Elsevier]

A lithium ion conductor with the garnet-type structure, Li7La3Zr2O12 (LLZ), showing a high Li+ conductivity of 0.49mScm−1 at 25°C, is synthesized via milling (500rpm, 12h) and following sintering at 1125°C for 20h. The improved Li+ conductivity is attributed to the decrease of the particle size, the uniform distribution of particles before sintering, the high concentration of Li+ in the octahedral site (96h), and low occupancies of Li+ in the tetrahedral site (24d). Also, it is found that the cubic phase of LLZ is stabilized by a contamination of Al3+ ion into the LLZ lattice. The structural position of Al3+ is verified to be in the tetrahedral site (24d) by analyzing SEM images, MAS NMR, Pawley refinement using X-ray powder diffraction, and structural refinement using neutron powder diffraction data. [ABSTRACT FROM AUTHOR]

Oxide-based all solid state battery (ASSB) systems require highly enhanced cell assemblies technology in the light of the sintering issue, although various inorganic-based lithium ion conductors have been proposed and attempted to be adopted in battery systems. Here, the compatibility of Li–La–(Zr–Ta)–O garnet related lithium ion conductors with ASSB systems processed by spark plasma sintering (SPS) is reported. Further, the challenges with respect to the material and processing are also discussed. Li7−x La3Zr1.5Ta0.5O12−d processed by SPS shows a high ionic conductivity of 1.35 × 10−3 S cm−1 and 1.23 × 10−2 S cm−1 at 25 °C and 80 °C, respectively. In addition, the material also shows good structural stability, which is a critical challenge encountered in garnet structured materials treated under severe SPS process conditions. An ASSB assembled by SPS using the Li4Ti5O12–Li7−x La3Zr1.5Ta0.5O12−d composite electrode shows a surface capacity of 0.2 mAh cm−2 at 80 °C. The battery shows a well-organized structure with a good lithium diffusion percolation path and the low solid contact resistance without any defects and undesirable reactions arising from the sintering method. [ABSTRACT FROM AUTHOR]

Abstract: Li1+x Cr x Sn2−x P3−y V y O12 solid electrolyte materials with x = 0.8 and y = 0, 0.2, 0.4, 0.6 and 0.8 are prepared by mechanochemical milling method followed by heat treatment at 1000 °C. The conductivities of the pellets are determined using AC impedance spectroscopy. X-ray diffraction is used to determine the crystallographic phases while scanning electron microscope and energy dispersive X-ray are used to study morphological properties and elemental compositions respectively. Combined substitution of both chromium and vanadium in LiSn2P3O12 system results in enhancement of room temperature ionic conductivity up to two orders of magnitude compared to the unsubstituted LiSn2P3O12 system. The increase in conductivity in the systems with y of 0.2 and 0.4 as compared to the sample of y = 0 is attributed to the absence of Li6P6O18 impurities. Furthermore, the sample with y = 0.4 shows higher ionic conductivity compared to the sample with y = 0.2. This sample exhibits bulk conductivity of 10−3 S cm−1 and grain boundary conductivity of 10−5 S cm−1 at elevated temperatures. This is attributed to larger crystallite size and better contact between grains. This sample is also structurally stable toward temperature and thus suitable for thermal electrochemical device application. [Copyright &y& Elsevier]

Abstract: Li3SO3N has been prepared by the mechanochemical reaction between lithium sulfamate (LiSO3NH2) and lithium amide or lithium hydride. This is the first example of an anhydrous compound containing the rare [SO3N]3− polyanion. Li3SO3N adopts the low-temperature β structure of isoelectronic Li3PO4. Structural refinement from neutron powder diffraction data supports disordering of nitrogen over two of the three anion sites, although a fully disordered model cannot be conclusively refuted. While the compound is a poor ionic conductor, it is electrochemically stable to at least 5 V vs. Li+/Li0. This simple mechanochemical pathway should be suitable for preparing a host of other alkali-rich nitrogen-containing polyanionic compounds. [Copyright &y& Elsevier]

Abstract: Amorphous a-LATP (x = 0.3) fine powder with the composition of Li1+x Al x Ti2−x (PO4)3 in Li2O–Al2O3–TiO2–P2O5 system was prepared directly from a mixture of Li2O, γ-Al2O3, TiO2, and P2O5 as starting materials, by using a mechanical milling (MM) technique at room temperature. A NASICON-type Li1+x Al x Ti2−x (PO4)3 (x = 0.3) (c-LATP (x = 0.3)) solid solution was obtained by the heat treatment of mechanochemically prepared amorphous a-LATP (x = 0.3) material. The sintered c-LATP (x = 0.3) pellet showed high lithium ion conductivity of the order of 10−4 S cm−1 at room temperature and activation energy of about 35 kJ mol−1. The high-conducting lithium ion c-LATP (x = 0.3) solid electrolyte fine powders were investigated as surface modification materials of LiCoO2 cathode in lithium cells using nonaqueous electrolyte solutions. The c-LATP (x = 0.3)-modified LiCoO2 electrodes exhibited high capacity (ca. 180 mAh g−1) and good cycle performance with a high charge cut-off potential of 4.5 V (vs. Li/Li+) in lithium cell. The increase in the electrode/electrolyte interfacial resistance for the LiCoO2 electrode modified with c-LATP (x = 0.3) fine powder was inhibited. [Copyright &y& Elsevier]

Abstract: A Li1.4Al0.4Ge1.6(PO4)3 (LAGP) sheet was prepared using a tape casting method with a fine LAGP power prepared from a sol–gel precursor. The addition of nanosize TiO2 as a sintering additive was effective to enhance the ionic conductivity of the tape-cast sheet. The highest electrical conductivity of 8.37 × 10−4 S cm−1 was observed for the tape-cast LAGP sheet with 5 wt.% TiO2 at 25 °C. A hybrid sheet of the tape-cast LAGP and epoxy resin was water impermeable. The electrical conductivity of the water impermeable hybrid sheet with ca. 4% epoxy resin was 4.19 × 10−4 S cm−1 at 25 °C. The three-point bending strength of the LAGP–5 wt.% TiO2–epoxy resin hybrid sheet was 111 N mm−2, which is comparable with a Li1+x+y Al x Ti2−x P3−y Si y O glass ceramic plate. The Li/PEO18(CF3SO2)2N/LAGP–5 wt.% TiO2–epoxy sheet was successfully operated as a lithium electrode in saturated LiCl aqueous solution. [Copyright &y& Elsevier]

A new potentiometric CO2 gas sensor using lithium–lanthanum–titanate (Li0.35La0.55TiO3, LLTO) electrolyte, Li2CO3 sensing electrode, and Li2TiO3 +TiO2 reference electrode was investigated. The microstructure and electrical properties of the optimized solid electrolyte were examined and the measured conductivity values were found consistent with those reported in literature. The performance of the sensor depended both on the fabrication temperature and the sensor operation temperature. Sensors with the sensing electrode fabricated above 500°C performed poorly. For sensing electrodes fabricated at 500°C, as the sensing temperature increased from 300 to 450°C, the performance of the sensor improved (near Nernstian response), but above 450°C, the sensor degraded. The proposed hypothesis for the degradation beyond 450°C is that at low levels of CO2 (ppb in the background), Li2CO3 reacts with LLTO resulting in insertion of Li+ into LLTO that causes changes in the electrical properties of the electrolyte. Poor performance of sensors fabricated at 700°C was due to formation of a new phase, LaLi1/3Ti2/3O3. Thermodynamic calculations combined with X-ray diffraction of the reaction products are used to support the hypothesis. Introduction of high concentrations of CO2 (~99.99%) during sensor fabrication (650°C) eliminated the reaction between Li2CO3 and LLTO, and also facilitated the bonding between the electrode and the electrolyte. As for long-term device performance, it is shown that the sensor can measure changes in CO2 concentrations reproducibly below temperatures of 450°C, as long as it is operated in conditions where there is a background of CO2, such as in ambient atmosphere or combustion environments. The sensor exhibits minimal interference toward oxygen, but significant interference to humidity. [ABSTRACT FROM AUTHOR]

Abstract: Low temperature cubic garnet-type Li7La3Zr2O12 was obtained by annealing the tetragonal Li7La3Zr2O12 at 450°C for 20h in air. The cubic phase was not observed by annealing at 450°C in oxygen and argon atmospheres. The phase transition of the tetragonal to cubic phase was reversible in air and could be explained by CO2 absorption of around 2.5wt.%. The low temperature cubic Li7La3Zr2O12 had a low bulk ionic conductivity of 1.3×10−6 Scm−1 at 25°C, which is lower than those of the tetragonal Li7La3Zr2O12 (3.3×10−6 Scm−1) and high temperature cubic phases (5.8×10−4 Scm−1). [Copyright &y& Elsevier]

Abstract: Lithium-ion conducting solid electrolytes in the composition (100-x)Li3PS4·xLiAlS2 (mol%) were prepared by the use of a high-energy ball-milling process at room temperature. Amorphous samples were obtained in the composition range of x=0 to x=13.1. In the composition of x≥18.2, a crystalline Al2S3 phase remained in the samples which were ball-milled for 35h. The lithium ion conductivity at 298K of the obtained amorphous samples was increased with an increase in the compositional parameter x and showed the maximum at the compositional parameter x=13.1 (86.9Li3PS4·13.1LiAlS2: σ298K =6.0×10−4Scm−1 at 298K). [Copyright &y& Elsevier]

Abstract: We performed nanoscopic cyclic voltammetry and chronoamperometry on the Ohara lithium ion conductive glass ceramic. When the critical bias voltage was exceeded, metallic lithium particles were deposited irreversibly under the conductive AFM tip acting as working electrode. Due to the huge area difference between working electrode and counter electrode, a reference electrode was not required. We present an in-situ method for studying the particle growth mechanism by simultaneously monitoring the reduction current and the particle height. We found good agreement between the topographically determined volume of the lithium particles and the volume expected from the charge flow. The results for time dependence of the particle growth can be used for controlling the vertical and lateral dimensions of the particles. [Copyright &y& Elsevier]

Abstract: In the present work, we focus attention on the effect of LiI addition to newly discovered pure lithium ion conductor, LiBH4. Solid solution of the composition LiBH4–LiI (LiI: 6.25–33.3mol%) was synthesized by solid state reaction. Electrical conductivity was measured from room temperature to 140°C by ac impedance method, which revealed the fast-ion conduction phase of LiBH4 can be stabilized to lower temperature, below the room temperature. Solid solution with LiI showed higher conductivities and lower activation energies in comparison with LiBH4. Powder XRD measurement was carried out at 120°C (just above the transition temperature of LiBH4). The lattice constants of the solid solution were determined. DSC measurement showed a systematic compositional dependence on the transition temperature. The stabilization mechanism was discussed. [Copyright &y& Elsevier]

Lithium exchanged phases of amorphous and crystalline zirconium titanium phosphate have been synthesized by an ion exchange technique. These materials have been characterized by elemental analysis (ICP-AES and AAS), spectral analysis (FTIR), thermal analysis (TGA) and X-ray diffraction studies. The conductance properties of these materials have been explored by measuring specific conductance at different temperatures in the range of 30-250 °C at 10 °C intervals, using impedance analyzer over a frequency range 1 Hz - 32 MHz at a signal level below 1 V. Lithium exchanged phases of amorphous and crystalline zirconium phosphate and titanium phosphate have also been synthesized under identical conditions, characterized and their conductance properties investigated for comparative studies. It is observed that, in all cases, conductivity decreases with increasing temperature. Conductance performance is discussed based on conductivity data and activation energy. [ABSTRACT FROM AUTHOR]

Abstract: We report on the development of a potentiometric sensor with Li3PO4 electrolyte and BaCO3-coated Li2CO3 sensing electrode for measuring CO2 over a wide range of concentrations (500ppm to 20%) at 500°C with minimal interference to humidity. The active element in the sensing electrode for CO2 detection is Li2CO3. However, sensors with just Li2CO3 electrodes showed interference from humidity, which was eliminated by use of the BaCO3 layer. Infrared spectroscopy as well as electrode preparations involving heating above the eutectic temperature of BaCO3–Li2CO3 suggests that the BaCO3 layer wets the Li2CO3 electrode surface, making it more hydrophobic and thereby reducing the interference from humidity. [Copyright &y& Elsevier]

Abstract: A series of triple ionic compounds consisting of double armed anions and one cation were prepared as lithium cation conductive matrices. As anions, lithium borates derived from lithium-9-borabicyclo[3,3,1]nonane hydride were introduced. The sterically hindered borate anion structures prevented the crystallization of triple ionic compounds. Introduction of ethylene oxide chains attached to the borate anions led to lower glass transition temperature, and also improved ionic conductivity. A lithium transference number of 0.73 was observed in spite of the presence of ethylene oxide chains. [Copyright &y& Elsevier]

Abstract: The lithium ion conducting solid lithium phosphorous nitride (LiPON) has been sputtered on the water-stable NASICON-type lithium ion conducting solid electrolyte Li1+x+y Al x Ti2−x P3−y Si y O12 (LATP). The stability and the interface resistance of the Li–Al/LiPON/LATP/LiPON/Li–Al cell have been examined. It is shown that the LiPON film protects LATP from reacting with the Li–Al alloy. The impedance of the Li–Al/LiPON/LATP/LiPON/Li–Al cell has been measured in the temperature range 25–80°C. The total cell resistance is about 8600Ωcm2 at room temperature and 360Ωcm2 at 80°C. The analysis of the impedance profiles suggests that the Li–Al/LiPON interface resistance is dominant at lower temperatures. The LATP plate immersed in water for 1 month shows only a slight degradation in the conductivity. [Copyright &y& Elsevier]