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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 effect of the particle sizes of LiNi 1/3 Co 1/3 Mn 1/3 O 2 and Li 2 S–P 2 S 5 solid electrolytes (SEs) on the electrode morphology was investigated. Smaller-sized SE particles were advantageous in fabricating dense and homogeneous electrode layers with an effective lithium-ion conduction pathway and a large electrode–electrolyte interfacial contact area because of the unique mechanical properties of sulfide-based SEs. The homogeneous distribution of the SE is also effective in the suppression of cracking and fracturing of LiNi 1/3 Co 1/3 Mn 1/3 O 2 because of the favorable mechanical properties of the sulfide-based SEs. The capacity of the all-solid-state cells under high-rate operation was thus remarkably improved. [ABSTRACT FROM AUTHOR]

Abstract: Composite electrodes composed of amorphous titanium polysulfide (a-TiSx) and titanium disulfide (TiS2) were designed for application in all-solid-state batteries. The conductivity of the a-TiSx/TiS2-based working electrode was higher than that of the amorphous TiS4 (a-TiS4); the reversible capacity of the cell using a-TiSx/TiS2 electrode was higher than that of the cell using a-TiS4. Designing nanocomposite materials such as the a-TiS x /TiS2 described in this paper is an effective way to improve the performance of all-solid-state batteries. [Copyright &y& Elsevier]

(100 − x)(0.75Li2S·0.25P2S5)·xLiBH4 (0 ≤ x (mol%) ≤ 33) glass electrolytes were prepared from 75Li2S·25P2S5 (mol%) glass and LiBH4 crystal by a mechanical milling technique. The effects of the addition of LiBH4 on the structures and properties of the glass electrolytes were examined. The DSC curves of the prepared glasses with LiBH4 did not have the endothermic peak attributable to the phase transition of LiBH4 crystal. The Raman spectra of the glasses indicated that the glasses included PS4 3− and BH4 − ions. The conductivities of the glasses increased with increasing the LiBH4 content. The glass at the composition of x = 33 showed the highest lithium-ion conductivity of 1.6 × 10−3 S cm−1 at room temperature. The glass had a wide electrochemical window up to 5 V vs. Li+/Li. An all-solid-state Li/TiS2 cell using the glass as an electrolyte successfully operated as a secondary battery at 25 °C. [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]

Abstract: Electrode–electrolyte composite materials were prepared by coating a highly conductive Li2S–P2S5 solid electrolyte onto LiCoO2 electrode particles using pulsed laser deposition (PLD). Cross-sections of the composite electrode layers of the all-solid-state cells were observed using a transmission electron microscope to investigate the packing morphology of the LiCoO2 particles and the distribution of solid electrolyte in the composite electrode. All-solid-state cells based on a composite electrode composed entirely of solid-electrolyte-coated LiCoO2 were fabricated, and their performance was investigated. The coating amounts of Li2S–P2S5 solid electrolytes on LiCoO2 particles and the conductivity of the coating material were controlled to increase the capacity of the resulting all-solid-state cells. All-solid-state cells using LiCoO2 with thick solid electrolyte coatings, grown over 120min, had a capacity of 65mAhg−1, without any addition of Li2S–P2S5 solid electrolyte particles to the composite electrode. The capacity of the all-solid-state cell increased further after increasing the conductivity of the Li2S–P2S5 solid electrolyte coating by heat treatment at 200°C. Furthermore, an all-solid-state cell based on a composite electrode using both a solid electrolyte coating and added solid electrolyte particles was fabricated, and the capacity of the resulting all-solid-state cell increased to 95mAhg−1. [Copyright &y& Elsevier]

Abstract: All-solid-state lithium secondary batteries using LiCoO2 particles coated with amorphous Li2O–TiO2 films as an active material and Li2S–P2S5 glass-ceramics as a solid electrolyte were fabricated; the electrochemical performance of the batteries was investigated. The interfacial resistance between LiCoO2 and solid electrolyte was decreased by the coating of Li2O–TiO2 films on LiCoO2 particles. The rate capability of the batteries using the LiCoO2 coated with Li2Ti2O5 (Li2O·2TiO2) film was improved because of the decrease of the interfacial resistance of the batteries. The cycle performance of the all-solid-state batteries under a high cutoff voltage of 4.6V vs. Li was highly improved by using LiCoO2 coated with Li2Ti2O5 film. The oxide coatings are effective in suppressing the resistance increase between LiCoO2 and the solid electrolyte during cycling. The battery with the LiCoO2 coated with Li2Ti2O5 film showed a large initial discharge capacity of 130mAh/g and good capacity retention without resistance increase after 50 cycles at the current density of 0.13mA/cm2. [Copyright &y& Elsevier]

Abstract: All-solid-state lithium secondary batteries using LiCoO2 active materials coated with Li2SiO3 and SiO2 oxide films and Li2S–P2S5 solid electrolytes were fabricated and their electrochemical performance was investigated. The electrochemical performace of the all-solid-state cells at a high voltage region was highly improved by using oxide-coated LiCoO2. The oxide coatings are effective in suppressing the formation of an interfacial resistance between LiCoO2 and the solid electrolyte at a high cutoff voltage of 4.6V (vs. Li). As a result, charge–discharge capacities and cycle performance at the cutoff voltage were improved. The cell with Li2SiO3-coated LiCoO2 showed a large initial discharge capacity of 130mAhg−1 and a good capacity retention of 110mAhg−1 after 50th cycles at the cutoff voltage of 4.6V (vs. Li). [Copyright &y& Elsevier]

Highlights: [•] LiMn2O4 thin films were prepared by using the mist CVD process. [•] An aqueous solution of lithium and manganese acetates is used for the precursor solution. [•] The cell with the LiMn2O4 thin films exhibited a capacity of about 80mAh/g. [•] The cell showed good cycling performance during 10 cycles. [Copyright &y& Elsevier]

As an environmentally friendly Pb-free material, SnO–B 2 O 3 glass is considered a next-generation negative-electrode active material for all-solid-state lithium-ion batteries. Using SnB 2 O 4 (50SnO·50B 2 O 3) as a negative-electrode active material, the all-solid-state cells exhibit a high initial discharge capacity of approximately 950 mAh g−1. In this study, the microstructures of the SnB 2 O 4 glassy electrode composites are investigated to clarify the charge–discharge behavior and charge–discharge mechanisms of the SnB 2 O 4 glassy electrode composites using transmission electron microscopy (TEM). Here, ex situ TEM observations capture Sn and Li–Sn alloy nanocrystallites in the amorphous matrix. Li+ is incorporated into Sn, and Li–Sn alloy nanocrystallites are formed after initial lithiation. Further, Li+ is extracted from Li–Sn alloys to form Sn nanocrystallites after initial delithiation. In particular, Sn is lithiated and delithiated during the first cycle. However, as the cycle number increases, the capacity deteriorates. Ex situ TEM observations further reveal that Li–Sn alloys remain unchanged even after delithiation, and the crystallite size increases significantly. It is thus found that the capacity deterioration is attributed to the irreversible Li insertion/extraction between Sn and Li–Sn alloys. • SnO–B 2 O 3 glass is a next-generation negative-electrode active material. • SnO–B 2 O 3 glass is applied to all-solid-state lithium-ion batteries. • Microstructure and morphology during charge-discharge process are examined by TEM. • Ex situ TEM observations capture the formation of Sn and Li–Sn alloy crystallites. [ABSTRACT FROM AUTHOR]

All-solid-state sodium batteries with sulfide-based solid electrolytes are attracting attention as next-generation energy storage systems to replace Li-ion batteries, owing to their improved safety and the abundant sodium resources. Na 3 PS 4 -based materials, which have relatively high conductivities and favorable mechanical properties, make promising Na-ion solid electrolytes for realizing all-solid-state sodium batteries. However, it is essential to establish a further simple and effective protocol for manufacturing such solid electrolytes and composite electrodes. In this study, Na 3- x PS 4- x Cl x (x = 0, 0.0625) was prepared by a liquid-phase (suspension) process from Na 2 S, P 2 S 5 , and NaCl using 1,2-dimethoxyethane as a reaction media. Na 3 PS 4 heated at 400 °C and Na 2.9375 PS 3.9375 Cl 0.0625 heated at 480 °C exhibited Na-ion conductivities of 2.6 × 10−4 and 4.3 × 10−4 S cm−1 at 25 °C, respectively. A homogenous composite electrode was prepared with TiS 2 active material and Na 3 PS 4 solid electrolyte via the simple liquid-phase process, resulting in large contact areas between electrode and electrolyte particles. The electrode obtained by liquid-phase provided an all-solid-state cell with higher reversible capacity of 161 mAh g−1 than a conventional mechanically mixed electrode. Suspension syntheses of Na 3- x PS 4- x Cl x are useful for the simple production of solid electrolytes and are highly applicable to all-solid-state sodium batteries. • Na 3- x PS 4- x Cl x (x = 0, 0.0625) electrolytes are prepared using 1,2-dimethoxyethane. • Na 3 PS 4 shows a high sodium-ion conductivity of 2.6 × 10−4 S cm−1. • Na 2.9375 PS 3.9375 Cl 0.0625 exhibits a superior conductivity of 4.3 × 10−4 S cm−1. • A TiS 2 –Na 3 PS 4 composite electrode is obtained by a simple liquid-phase process. • An all-solid-state cell using the electrode shows a high capacity of 161 mAh g−1. [ABSTRACT FROM AUTHOR]

Abstract All-solid-state cells are safe, and have high energy densities and power densities. Sulfide-based solid electrolytes (SEs) exhibit high ionic conductivities and favorable mechanical properties allowing for the facile preparation of all-solid-state cells via simple mixing and cold-pressing processes. For practical applications, it is necessary to produce SEs and all-solid-state cells more efficiently. Herein, a novel fabrication process for homogeneous composite electrodes used in all-solid-state cells was successfully demonstrated using an infiltration technique. The Li 4 Ti 5 O 12 and carbon nanotube (LTO@CNT) porous electrode was infiltrated with a precursor solution containing an argyrodite Li 6 PS 5 Br SE, and the solvent was removed by drying at 150 °C under vacuum to prepare an infiltrated SE-LTO@CNT electrode. The process without conventional mixing formed an electrochemically active interface with a large contact area and favorable conduction pathways. The all-solid-state cell with the SE-LTO@CNT electrode showed an improved capacity of 163 mAh g−1 compared to those prepared with the dry-mixed electrodes at 25 °C, and the high capacity was maintained for 500 cycles. Moreover, the cell with the SE-LTO@CNT electrode showed a reversible capacity of 100 mAh g−1 or more at 4 C-rate and 100 °C. Thus, the infiltration process is effective for the practical fabrication and application of all-solid-state cells. Highlights • Li 4 Ti 5 O 12 -CNT-Li 6 PS 5 Br electrode is prepared by an infiltration technique. • The infiltration process is effective in achieving electrode-electrolyte interface. • An all-solid-state cell with the electrode shows a high capacity of 163 mAh g−1. • The cell operates with high rate and good cycle performances at 100 °C. [ABSTRACT FROM AUTHOR]

Graphite–solid electrolyte (SE) composite anode, prepared by spark-plasma-sintering (SPS) process, was applied to all-solid-state lithium secondary batteries with lithium sulfide (Li2S) positive electrode. The electrochemical tests demonstrated that the graphite–SE/Li2S cells showed the discharge capacity of ca. 750mAh·g−1-Li2S with the average voltage of ca. 1.98V. Although the discharge capacity was lower than that of the In/Li2S cells (ca. 920mAh·g−1-Li2S), the estimated energy density was higher than that (ca. 1490 and 1220mWh·g−1-Li2S for graphite–SE/Li2S and In/Li2S cells, respectively), due mainly to its higher average voltage. The graphite–SE/Li2S cells showed improved rate capability as compared with the cells with the graphite+SE blended powder, which was attributable mainly to the reduced interfacial resistance between the graphite and SE particles caused by the SPS process. [ABSTRACT FROM AUTHOR]