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To overcome the challenges associated with the toxicity of the majority of organic solvents for the liquid phase synthesis of solid electrolytes toward the human body and environment, we demonstrate the synthesis of tin-based sulphide electrolytes using water, which is the most environmentally friendly solvent. ortho-Thiostannate, i.e., Li4SnS4, was obtained from a mixture of Li2S, Sn, and S using aqueous solution synthesis. Furthermore, Li10SnP2S12, a superionic conductor, was obtained by mixing an aqueous solution of Li4SnS4 and tetrahydrofuran suspension of Li3PS4, which exhibited the highest ionic conductivity (5.9 × 10−3 S cm−1 at 25 °C) in liquid-phase synthesis. This study successfully demonstrates that water can be efficiently used to synthesize sulphide electrolytes instead of conventional organic solvents. [ABSTRACT FROM AUTHOR]

Controlling Li ion transport in glasses at atomic and molecular levels is key to realizing all‐solid‐state batteries, a promising technology for electric vehicles. In this context, Li3PS4 glass, a promising solid electrolyte candidate, exhibits dynamic coupling between the Li+ cation mobility and the PS43− anion libration, which is commonly referred to as the paddlewheel effect. In addition, it exhibits a concerted cation diffusion effect (i.e., a cation–cation interaction), which is regarded as the essence of high Li ion transport. However, the correlation between the Li+ ions within the glass structure can only be vaguely determined, due to the limited experimental information that can be obtained. Here, this study reports that the Li ions present in glasses can be classified by evaluating their valence oscillations via Bader analysis to topologically analyze the chemical bonds. It is found that three types of Li ions are present in Li3PS4 glass, and that the more mobile Li ions (i.e., the Li3‐type ions) exhibit a characteristic correlation at relatively long distances of 4.0–5.0 Å. Furthermore, reverse Monte Carlo simulations combined with deep learning potentials that reproduce X‐ray, neutron, and electron diffraction pair distribution functions showed an increase in the number of Li3‐type ions for partially crystallized glass structures with improved Li ion transport properties. Our results show order within the disorder of the Li ion distribution in the glass by a topological analysis of their valences. Thus, considering the molecular vibrations in the glass during the evaluation of the Li ion valences is expected to lead to the development of new solid electrolytes. [ABSTRACT FROM AUTHOR]

All‐solid‐state lithium‐sulfur batteries (ASSLSB), composed of sulfur cathode and lithium metal anode with high theoretical capacity, have a potentially higher energy density by weight than a typical lithium‐ion battery (LIB). However, due to insulating sulfur, a relatively large proportion of electronic (carbon) and ionic (solid electrolyte) conductors are mixed for cathode fabrication, leading to inferior practical capacity. Herein, we report a novel integrated cathode Li2S‐LiI‐MoS2 which has relatively high electronic and ionic conductivities (the order of 10−4 S cm−1) without any carbon and solid electrolyte. The ASSLSB with integrated Li2S‐LiI‐MoS2 cathode delivers a remarkably high energy density of 1020 Wh kg−1 at the cathode level at room temperature. By applying precise X‐ray diffraction, pair distribution function analysis and X‐ray computed tomography, it is found that the formation of an ionic conducting phase composed mainly of LiI during discharge is responsible for the high rate capability. Furthermore, X‐ray absorption fine structure (XAFS) has also revealed the charge compensation mechanism and ascertained the involvement of both Mo 3d and S 3p orbitals during the charging and discharging process. It is believed the strategy will pave the way for developing high practical energy density at room temperature for all‐solid‐state batteries. [ABSTRACT FROM AUTHOR]

Li2S is a promising cathode candidate for all-solid-state batteries (ASSBs) because of its high theoretical capacity and availability for coupling with a Li-free anode or an anode-less electrode. However, ionically insulating Li2S leads to excess conductive additives, low sulfur utilization and sluggish kinetics, which hinders the implementation of high energy density potential by ASSBs. Improving the intrinsic conductivity of Li2S is the key to solve this issue. In this study, PI3-doped Li2S cathodes were fabricated and the relationship between lithium vacancies and ionic conductivities was examined quantitatively by the time-of-flight (TOF) neutron diffraction. By cation–anion dual doping, the ionic conductivities of Li2S–PI3 materials were improved to 10−4 S cm−1, which is desirable for the cathode without solid electrolytes added. Upon simply mixing with carbon, the Li2S–PI3–C cathode shows a high overall cathode capacity of 541 mA h g−1 with a high S utilization of 82% at 0.05C and a capacity of 207 mA h g−1 at 1C at room temperature, realizing high energy density with good rate performance. [ABSTRACT FROM AUTHOR]

The problem of lithium dendrites must be addressed for practical lithium metal all-solid-state batteries. Herein, three-dimensional morphological changes within Li3PS4 electrolyte away from the anode were observed using operando X-ray computed tomography. We revealed that the electronic conduction of decomposition and the electrolyte/void interface cause the lithium deposition within the Li3PS4. [ABSTRACT FROM AUTHOR]

Yellow needles-like single crystals of Li4P2S6 were obtained serendipitously during the preparation of Li7P3S10O. The twinned crystal structure of Li4P2S6 was determined from single-crystal X-ray diffraction data [wR(F2) = 0.069, 716 reflections, 40 variables]. Li4P2S6 crystallizes in the trigonal system, space group P 3 ‾ m 1 (N° 164), a = 10.5042(8) Å, c = 6.5837(6) Å, V = 629.11(9) Å3 and Z = 2. The lithium octahedra form a [Li4S6]8− honeycomb-like structure within which diphosphate units are located. The comparison of our crystal structure to those of P63/mcm-, P 3 ‾ 1 m -, and P321-Li4P2S6 demonstrated group-subgroup relationships and associated the disorder or order of the phosphorus atoms within the identical [Li4S6]8− 3d-frameworks to the choice of the unit cell (the subcell with a ∼ 6.07 Å vs. the supercell with a ∼ 10.5 Å). [ABSTRACT FROM AUTHOR]

Liquid-phase syntheses of sulfide materials are attractive for the mass production of solid electrolytes for all-solid-state batteries. In liquid-phase synthesis, the precursor of the solid electrolyte is obtained. The precursors are important for producing electrolytes of the same quality because they decompose into electrolytes by heat treatment. However, only a few studies have focused on the formation mechanism and structure of precursors. This study proposes a formation mechanism for Li3PS4 during liquid-phase synthesis using ethylenediamine (EDA) as a solvent and clarifies the crystal structure of Li3PS4·NH2CH2CH2NH2 (Li3PS4·EDA). Raman spectroscopy and nuclear magnetic resonance revealed that intermediate P2S62− units were generated in the EDA solution. Crystal structure analysis of Li3PS4·EDA showed that the terminal nitrogen atom of EDA coordinates with two lithium atoms. Ionic conductivity of Li3PS4·EDA was 2.8 × 10−9 S cm−1 at 25 °C. The analysis of precursors of solid electrolytes provides insight into the behavior of solvent molecules as ligands in the synthesis of sulfide electrolytes. Highlights: β-Li3PS4 is prepared using a precursor obtained from Li3PS4 and ethylenediamine. Intermediate P2S62− units are generated in the ethylenediamine solution. Tetrahedra of PS4 and LiS4 form a framework in the precursor. Ethylenediamine molecules coordinate to two lithium cations in the precursor. [ABSTRACT FROM AUTHOR]

The electrochemical window of solid electrolytes (SEs) plays a crucial role in designing active material–SE interfaces in high‐energy‐density all‐solid‐state batteries (ASSBs). However, the suitable electrochemical window for individual active materials is not yet investigated, as the electrochemical window of SEs is overestimated. In this study, the oxidation onset voltages (OOVs) of several SEs, namely those compatible with Li2S as a high‐capacity positive electrode material are determined. Results reveal that SEs with low OOVs decrease the capacity and increase the interfacial resistance of the corresponding ASSBs. The OOVs of SEs must exceed that of Li2S by more than 0.2 V to achieve high capacity, which in turn depends on SE ionic conductivity. Therefore, an Li2S positive electrode is combined with pseudobinary Li‐oxyacid salts as SEs, exhibiting high OOVs and ionic conductivities, to afford a high‐capacity (500 Wh kg−1) ASSB with high Li2S content. [ABSTRACT FROM AUTHOR]

Li3PS4 is the most typical solid electrolyte for all-solid-state lithium batteries. However, to date, there are few reports on Li3PS4 solid electrolyte synthesized using the solution process. Here, β-Li3PS4 solid electrolytes were prepared via liquid-phase synthesis by dissolving Li2S and P2S5 in ethylenediamine (EDA) to form a homogeneous solution of Li3PS4. Since EDA is a basic protonic solvent, it effectively suppressed the decomposition of Li3PS4. An intermediate phase consisting of Li3PS4 and EDA was formed as a precursor after drying the EDA solution at 200 °C under vacuum. After heat treatment at temperatures above 260 °C, β-Li3PS4 was crystallized from the precursor. The ionic conductivity of the prepared β-Li3PS4 was 5.0 × 10−5 S cm−1 at 25 °C and the activation energy for conduction was 35 kJ mol−1. The obtained EDA solution of Li3PS4 will be effective in forming electrolyte-electrode interfaces with the large contact areas in all-solid-state batteries. Highlights: β-Li3PS4 is prepared via liquid-phase synthesis using a ethylenediamine solution. Ethylenediamine effectively suppresses the decomposition of PS43−. The ionic conductivity of the prepared β-Li3PS4 is 5.0 × 10−5 S cm−1 at 25 °C. [ABSTRACT FROM AUTHOR]

Sulfide-based solid electrolytes (SEs) exhibiting high ionic conductivity are indispensable battery materials for next-generation all-solid-state batteries. However, sulfide-based SEs have a major drawback in their low chemical stability in air. When exposed to H2O or O2 gas, toxic H2S is generated, and their ionic conductivity considerably declines. However, their degradation mechanism caused by air exposure has not been understood yet. To clarify the degradation process, in this study, we developed a transmission electron microscope (TEM) system to evaluate the air stability of battery materials. Using a vacuum transfer double-tilt TEM holder with a gas-flow system, the in situ observation of the degradation process was conducted for a sulfide-based Li4SnS4 glass ceramic under an air-flow environment. Consequently, electron diffraction (ED) patterns and TEM images could clearly capture morphological changes and the amorphization process caused by air exposure. Moreover, based on the analysis of ED patterns, it is observed that Li4SnS4 is likely to decompose because of the reaction with H2O in air. Therefore, this airtight and air-flow TEM system should be effective in clarifying the process of the deterioration of sulfur-based SEs during exposure to air. [ABSTRACT FROM AUTHOR]

The reaction uniformity of LiCoO2 composite positive electrodes in all-solid-state cells was compared quantitatively by investigating the Raman band shifts corresponding to the state-of-charge (SOC) of LiCoO2. The quantitative SOC analysis was conducted using the Raman imaging data of composite electrodes with smaller or larger solid electrolytes. The electrodes exhibited different reaction uniformity although the cells showed similar initial charge capacities and average SOC. In the case of larger solid electrolytes, most LiCoO2 particles showed higher or lower SOC than the average SOC, and lower battery performance. The quantitative analysis of SOC in each LiCoO2 electrode demonstrated that a variable SOC outside the average SOC resulted in larger irreversible capacity and lower rate performance. The quantitative SOC analysis newly developed in the present study is a useful technique for designing composite electrodes showing higher battery performance. [ABSTRACT FROM AUTHOR]

We report a route for the synthesis of Na3SbS4–Na2WS4 superionic conductors from aqueous solution. Na3SbS4–Na2WS4 has the highest high sodium-ion conductivity (4.28 mS cm−1 at 25 °C) of reported sulfide-based solid electrolytes prepared via liquid-phase methods. The antimony in Na3SbS4 is replaced by tungsten in a higher valence state, which is charge-compensated by sodium vacancies in the form Na3−xSb1−xWxS4. Introducing sodium vacancies while maintaining the 3D conduction pathways increases the pre-exponential factor in the Arrhenius plots of ionic conduction. The development of a facile synthetic protocol, as well as the high ionic conductivity and excellent chemical stability of Na3SbS4–Na2WS4 in the presence of water, is a major step towards the realization of all-solid-state sodium batteries. [ABSTRACT FROM AUTHOR]

Sulfide-based solid electrolytes with halide elements are essential components of advanced all-solid-state batteries. Argyrodite crystals are viable candidates as solid electrolytes for realizing all-solid-state batteries. However, a simple and effective route for the synthesis of these solid electrolytes is required. Herein, argyrodite Li6PS5Br superionic conductors were synthesized from a homogeneous solution by a liquid-phase technique. The Li6PS5Br solid electrolyte was prepared in a shorter synthesis time of one day using tetrahydrofuran and ethanol as compared with the solid-phase method. More importantly, of all the sulfide-based solid electrolytes prepared by liquid-phase techniques, Li6PS5Br showed the highest ionic conductivity of 3.1 mS cm−1 at 25 °C. The obtained particle size of 1 μm is suitable for application in all-solid-state cells. Moreover, coating electrode active materials with the solid electrolyte using the precursor solution led to a large contact area between the electrode and electrolyte and improved the cell performance. In addition, infiltrating a porous electrode with the precursor solution of the solid electrolyte is suitable for forming homogeneous composite electrodes to improve the cell performance. The all-solid-state cell using the Li6PS5Br fine powder with a high conductivity of 1 mS cm−1 or more exhibited a reversible capacity of 150 mA h g−1. This technique is effective for the industrial production of solid electrolytes and is applicable to all-solid-state batteries. [ABSTRACT FROM AUTHOR]

Mechanical properties such as formability and elastic moduli of solid electrolytes are important for the fabrication of all-solid-state batteries and retention of their charge–discharge capacities. In this paper, xNa2S·(100 −x)P2S5 (mol%) sulfide glass electrolytes (x = 50, 67, and 75) were prepared and their formability and elastic moduli were evaluated by an ultrasonic pulse-echo technique and a compression test under uniaxial pressing. The glasses were better densified and showed lower Young's moduli (15–19 GPa) than the Li2S–P2S5 glasses. [ABSTRACT FROM AUTHOR]

Amorphous titanium trisulfide (TiS) active materials were prepared by ball milling of an equimolar mixture of crystalline titanium disulfide (TiS) and sulfur. A high-resolution transmission electron microscope image revealed no periodic lattice fringes on the amorphous TiS. The all-solid-state lithium secondary batteries using a sulfide solid electrolyte and the amorphous TiS electrode showed high capacity of greater than 300 mAh g for 10 cycles. The amorphous TiS had a higher capacity than the mixture of crystalline TiS and S, which was used as the starting material of amorphous TiS. The X-ray diffraction patterns and the Raman spectra of the amorphous TiS electrode after the first and tenth charge-discharge measurements were similar to those before the measurement. The amorphous structure of TiS did not change greatly during the first few cycles. The all-solid-state cells with the amorphous TiS electrode showed higher initial coulombic efficiency because the amorphous TiS active material retained its structure during the initial electrochemical test. [ABSTRACT FROM AUTHOR]

Titanium sulfide thin film electrodes were prepared by the pulsed laser deposition method using a KrF excimer laser. Thin films of various compositions were prepared under several deposition conditions such as Ar gas pressure, laser fluence, and target-substrate distance. The thickness of the titanium sulfide thin film prepared under Ar gas pressure of 0.01 Pa, the pulse energy of 200 mJ/pulse, and the distance of 5 cm between the target and the substrate was ca. 400 nm. The films prepared at room temperature showed no peaks in the XRD pattern and no periodic lattice fringe in high-resolution transmission electron microscopic images, suggesting that they were amorphous. An all-solid-state cell using a TiS thin film electrode formed on a pelletized LiS-PS glass-ceramic electrolyte showed the reversible capacity of 543 mAh g, which was higher than that of a cell using a TiS film. The former solid-state cell retained higher capacity for 20 cycles at room temperature. [ABSTRACT FROM AUTHOR]

Highly lithium-ion conductive Li2S–P2S5 thin films were prepared using pulsed laser deposition at room temperature. The ambient Ar gas pressure during deposition strongly affected the thin films' chemical compositions and local structures. The chemical composition and the local structure of the 80Li2S·20P2S5 thin film prepared under 5 Pa showed good agreement with those of the highly lithium-ion conducting 80Li2S·20P2S5 glass powder prepared by mechanical milling. The ionic conductivity at 25°C and the activation energy for conduction of the as-deposited 80Li2S·20P2S5 thin films were, 7.9 × 10−5 S/cm and 43 kJ/mol, respectively. The ionic conductivity of the 80Li2S·20P2S5 thin film was increased to 2.8 × 10−4 S/cm through heat treatment. The highly lithium-ion conducting thin-films reported in this study are promising electrolytes for developing all-solid-state lithium batteries. [ABSTRACT FROM AUTHOR]

All‐solid‐state lithium–sulfur batteries have attracted much attention because of their large capacity and long life. However, their rate capability is not sufficiently high, prompting a great demand for improvement. Herein, a sulfur‐based composite electrode is fabricated for the high‐rate operation of all‐solid‐state lithium–sulfur batteries. The electrode is made of a carbon material having a large number of "interconnected mesopores" with a diameter of 5 nm. The highly mesoporous structure is conducive to electrode reactions and the formation of conduction pathways. Consequently, the rate capability of the composite electrode is drastically improved compared with that of an electrode made of conventional conducting nanocarbon. The all‐solid‐state lithium–sulfur battery with this composite electrode shows a high capacity of 1100 mA h g−1 per sulfur after 400 cycles at a high current density of 1.3 mA cm−2 at 25 °C. These findings are expected to contribute toward the development of practical all‐solid‐state lithium–sulfur batteries. [ABSTRACT FROM AUTHOR]

All‐solid‐state batteries attract significant attention owing to their potential to realize an energy storage system with high safety and energy density. In this paper, a mechanochemical synthesis of novel amorphous positive electrode materials of the Ni‐rich LiNi1−x−yMnxCoyO2 (NMC)–Li2SO4 system suitable for oxide‐type all‐solid‐state batteries is reported. Through the mechanochemical treatment with Li2SO4, excellent formabilities of the electrode materials as those of ductile solid electrolytes are obtained. Owing to the deformability of the active material, a good electrode/electrolyte interface is provided simply by pressing at room temperature. In all‐oxide solid‐state cells using 80NMCs·20Li2SO4 (mol%) positive electrode materials, the cell capacity increases with the Ni content in the NMC. The all‐solid‐state cell using the 80NMC811·20Li2SO4 positive electrode active material exhibits a high capacity larger than 250 mAh g−1 in a voltage range of 1.6–4.8 V versus Li at 100 °C. Furthermore, bulk‐type all‐oxide solid‐state batteries (Li4Ti5O12/80NMC532·20Li2SO4 (mol%)) successfully function as secondary batteries with excellent cycle performances. [ABSTRACT FROM AUTHOR]

The charge-discharge capacity of lithium secondary batteries is dependent on how many lithium ions can be reversibly extracted from (charge) and inserted into (discharge) the electrode active materials. In contrast, large structural changes during charging/discharging are unavoidable for electrode materials with large capacities, and thus there is great demand for developing materials with reversible structures. Herein, we demonstrate a reversible rocksalt to amorphous phase transition involving anion redox in a Li2TiS3 electrode active material with NaCl-type structure. We revealed that the lithium extraction during charging involves a change in site of the sulfur atom and the formation of S−S disulfide bonds, leading to a decrease in the crystallinity. Our results show great promise for the development of long-life lithium insertion/extraction materials, because the structural change clarified here is somewhat similar to that of optical phase-change materials used in DVD-RW discs, which exhibit excellent reversibility of the transition between crystalline and amorphous phase. [ABSTRACT FROM AUTHOR]