Electrolyte Sheet Research Articles

Stimulating the Electrostatic Interactions in Composite Cathodes Using a Slurry-Fabricable Polar Binder for Practical All-Solid-State Batteries

In this work, poly vinylidene fluoride–chlorotrifluoroethylene (PVdF-CTFE) is introduced as a slurry-fabricable polymer binder to fabricate a stable composite cathode using the complex materials of a Li[Ni0.7Co0.1Mn0.2]O2 cathode, Li6PS5Cl electrolyte, and super C carbon, for sulfide-based all-solid-state batteries (ASSBs). The high electronegativity of fluorine in the poly(vinylidene fluoride–chlorotrifluoroethylene (PVdF-CTFE) binder creates a polarized electronic environment in the composite cathode, promoting electrostatic interactions with Li ions. Compared with that of butadiene rubber (BR), the PVdF-CTFE binder has a stronger binding energy to the complex materials in the composite cathode, which enhances the mechanical rigidity of the composite cathode with highly uniform adhesion. In addition, uniform and close contact between the complex materials in the composite cathode reduces the resistance at the interfaces, lowering the energy barrier for Li+ diffusion, and eventually creates a fast Li+ diffusion pathway in the composite cathode. Thus, the pouch-type ASSBs cell, which comprises the composite cathode with the PVdF-CTFE binder, Li6PS5Cl electrolyte sheet, and silver-carbon (Ag/C) Li-free anode delivers a high reversible capacity of 198.5 mAh g–1 at 0.1 C and long-term cycling stability over 300 cycles with a capacity retention of 74.5 % at 0.5 C at 60 °C.

Enhanced electrochemical performance of garnet Li7La3Zr2O12 electrolyte by efficient incorporation of LiCl

Garnet-type Ta-doped Li7La3Zr2O12 (LLZO) lithium-ion-conducting ceramic electrolytes has become the promising and critical candidate for developing the high-energy-density all-solid-state lithium batteries, due to the satisfied Li+ conductivity, stability against metallic lithium anode, and the feasible preparation under ambient air. Here, to further increase the lithium-ion conductivity of LLZO comparable to that of the commercial organic liquid electrolytes, lithium chloride (LiCl) is effectively introduced to synthesize the garnet-type ceramic electrolytes with the nominal composition (Li6.5La3Zr1.5Ta0.5O12)1-x–(LiCl)x (x = 0, 5mol%, 10mol%, 15mol%, 20mol%, and 25mol%) via high-temperature calcination process. The cubic structure with highly conductive performance is confirmed from X-ray diffraction measurement as well as Raman spectra analysis. Structural information is observed according to field emission scanning electron microscope equipped with energy dispersive spectrometer and density measurements. Among above investigated ceramic compositions, the prepared (Li6.5La3Zr1.5Ta0.5O12)0.85–(LiCl)0.15 ceramic electrolyte sheet sintered at 1200 °C for 12h presents the room-temperature Li-ion conductivity of 1.22 × 10−3 S·cm−1 by alternating current (AC) impedance analysis along with the corresponding activation energy of 0.262eV through Arrhenius equation calculation. The electronic conductivity measurements are also done by direct-current polarization to confirm the ionic nature for all investigated ceramics. Furthermore, the Li|(Li6.5La3Zr1.5Ta0.5O12)0.85–(LiCl)0.15 |Li symmetric batteries can possess the small interfacial resistance of 92.3 Ω cm2 and stably run for 1000 h at 0.1 mA cm−2 without a short circuit at room temperature. The hybridized lithium-sulfur battery with (Li6.5La3Zr1.5Ta0.5O12)0.85–(LiCl)0.15 electrolyte delivered excellent initial room-temperature discharge capacity of 1204mAh·g−1 and 1152 mAh·g−1 under the current density of 0.1C and 0.2C respectively, large coulombic efficiency, and great cycling stability. Moreover, the lithium-sulfur batteries also can show excellent cycling performances under different current densities and a good capacity recoverability. The above investigation results suggest that the low-melting-point LiCl incorporation in Li6.5La3Zr1.5Ta0.5O12 electrolyte is an effective measurement to synthesize the cubic and dense Li-stuff garnet ceramic sheets for the high-performance rechargeable next-generation solid-state batteries.

A rapid pressureless sintering strategy for LLZTO ceramic solid electrolyte sheets prepared by tape casting

Garnet-type electrolytes are regarded as one of the most promising solid-state electrolytes (SSEs) for lithium-ion batteries due to their potential advantages in terms of energy density, electrochemical stability and safety. To achieve the maximum energy density, it is necessary to ensure that the electrolyte layer is as thin as possible. Nevertheless, thin sheet SSE is more challenging to sinter than pellet due to the greater lithium volatilization from the high surface/volume ratio. Garnet-type SSE (Li6.5La3Zr1.5Ta0.5O12, LLZTO) green tape was prepared by the tape-casting technique. The effects of supporter, sintering temperature and dwell time on the relative density, microstructure and ionic conductivity of thin sheet were investigated. A ceramic SSE sheet with a thickness of 173 μm, a relative density of 97.2 %, an ionic conductivity of 2.02 × 10−4 S/cm at 25 °C and an activation energy of 0.25 eV, was achieved using a rapid pressureless sintering at 1250 °C for 25 min with a MgO supporter. This work offers insights into the practical production of LLZTO sheets.

Scalable Dry Process for Fabricating a Na Superionic Conductor-Type Solid Electrolyte Sheet.

The cost reduction and mass production of oxide-based solid electrolytes are critical for the commercialization of all-solid-state batteries. In this study, an environmentally friendly, low-cost, and high-density oxide-based Na superionic conductor-type solid electrolyte sheet was fabricated via a dry process without the use of any solvent. The polytetrafluoroethylene (PTFE), used as a binder, was transformed into thin thread-like structures via shear force, resulting in a flexible solid electrolyte sheet. The solid electrolyte powder quantity was limited to 50 wt % for fabricating a uniform green sheet via the wet process. However, when the dry process was employed for green sheet fabrication, the solid electrolyte powder quantity could be increased to values exceeding 95 wt %. Therefore, the green sheets produced by using the dry process demonstrated a higher density than those fabricated by using the wet process. The binder content and particle size affected the ionic conductivity of a solid electrolyte sheet fabricated via a dry process. The sheet obtained via the blending of 3 wt % PTFE binder with a solid electrolyte powder, finely ground using a planetary ball mill, which exhibited the highest total ionic conductivity of 1.03 mS cm-1.

Supercapacitor using polyvinyl alcohol doped ionic liquid 1‐butyl‐1‐methylpyrrolidinium hexafluorophosphate polymer electrolyte system

AbstractPolyvinyl alcohol‐based polymeric films with NaI and ionic liquid (1‐Butyl‐1‐methylpyrrolidinium hexafluorophosphate) have been developed by using the solution cast method. The produced polymer electrolyte sheets were evaluated using various methods. Electrochemical impedance spectroscopy was utilized to measure the conductivity of the polymeric films, and the ionic liquid doped films showed an increase with a maximum at 6 wt% ionic liquid with a value for conductivity of 4.545 × 10−4 S cm−1. The morphological features of the most conductive polymer were further investigated using polarized optical microscopy and x‐ray diffraction. Ionic doping causes an increase in the amorphous nature. Using Fourier transform infrared spectroscopy, an excellent complexity between PVA, salt NaI, and ionic liquid was assessed. Thermogravimetric analysis was used to inspect the polymer films' thermal stability. The highest conducting sample was used for manufacturing an electric double‐layer capacitor. The behavior of manufactured electric double‐layer capacitor has been evaluated through EIS, CV, and GCD.

Operando Nanomechanical Mapping of Amorphous Silicon Thin Film Electrodes in All-Solid-State Lithium-Ion Battery Configuration during Electrochemical Lithiation and Delithiation.

An operando bimodal atomic force microscopy system was constructed to perform nanomechanical mapping of an amorphous Si thin film electrode deposited on a Li6.6La3Zr1.6Ta0.4O12 solid electrolyte sheet during electrochemical lithiation/delithiation. The evolution of Young's modulus maps of the Si electrode was successfully tracked as a function of apparent Li content x in lithium silicide (LixSi) simultaneously with real-time surface topography observation. At the initial stage of lithiation, the average modulus steeply decreased due to the generation of LixSi from intrinsic Si, followed by a moderate modulus reduction until the electrode capacity reached 3300 mAh g-1 (Li content x = 3.46). In the following delithiation, the gradual recovery of the average modulus of LixSi was observed up to 1467 mAh g-1 (Li content x = 1.54) at which delithiation stopped due to the significant volume change induced by phase transformation of LixSi.

Binderless Sheet-Type Oxide-Sulfide Composite Solid Electrolyte for All-Solid-State Batteries

Lithium-ion batteries have been used as energy sources not only for small electronic devices but also for high-capacity and high-energy-density applications such as electric vehicles. However, the use of flammable organic liquid electrolytes in lithium-ion batteries has raised safety concerns in various applications. Therefore, solid-state batteries using flame-retardant inorganic materials are considered a more reasonable direction for future energy sources due to their high safety and high energy density. Solid electrolytes(SEs) are divided into oxide-based, sulfide-based, and polymer-based. Each solid electrolyte has its own advantages and disadvantages. Oxide-based solid electrolytes (e.g., Li7La3Zr2O12 (LLZO), Li3xLa2/3-xTiO3 (LLTO), Li1.3Al0.3Ti1.7(PO4)3 (LATP)) are air-stable and exhibit excellent electrochemical properties over a wide potential range. However, their high interfacial resistance may limit their practical application as batteries. Sulfide-based solid electrolytes (e.g., Li6PS5X (X=Cl, Br, I), Li10GeP2S12, (100-x)Li2S-xP2S5)) have high ionic conductivity, ductile properties, low interfacial resistance, and good room temperature workability. However, they are vulnerable to atmospheric instability, which can produce toxic gases such as H2S, and are relatively electrochemically unstable with Li metal. Polymer-based solid electrolytes, such as those made from polymers like PEO, PVDF, PAN, etc. that are compounded with other solid electrolytes (oxides, sulfides, etc.), offer the advantage of being able to form solid electrolyte membranes over large areas. But they have low ionic conductivity and weak mechanical properties of the polymer itself, limiting their practical application. To apply solid-state batteries to practical high-energy density energy storage devices such as electric vehicles, high ion conductivity, electrochemical stability, high mechanical properties, and large area formation of the electrolyte layer are essential. Solid electrolytes are mainly formed in powder form, and without a polymer binder, it is limited to apply as a film for large-capacity storage devices. Here, we fabricated a freestanding sheet-type Al-LLZO oxide-based solid electrolyte that forms a 3D network without a polymer material using an electrospinning method. In addition, we prepared a oxide-sulfide composite solid electrolyte membrane by impregnating LPSCl sulfide-based solid electrolyte into the Al-LLZO solid electrolyte sheet. As a result, This process removed the polymer and improved both the ionic conductivity and mechanical properties. Furthermore, it was possible to achieve both large-area and film characteristics without the need for a polymer.

Regulating the anion disorder and synthesizing the low-cost and high-performance Li6−xPS5−xCl1+x solid electrolytes

Sulfide solid electrolytes have attracted wide attention due to their high ionic conductivity. Li6PS5Cl is one of the most promising electrolytes for all-solid-state lithium batteries with high-energy-density. It is reported that the disordered arrangement of Cl- in the aragonite structure has a significant effect on the conductivity of Li6PS5Cl. In this work, the disorder of anion sites is modestly regulated by adjusting the ratio of S and Cl in Li6−xPS5−xCl1+x electrolyte. In addition, to verify the commonality of this strategy, Li5.6PS4.6Cl1.4 is prepared using self-made Li2S, and similar results are obtained. On this basis, the density of Li5.6PS4.6Cl1.4 electrolyte sheet is improved by hot-pressing, which can successfully inhibit the growth of lithium dendrites. As expected, the ionic conductivity of the sulfide electrolyte and the electrochemical performance of the ASSLBs are greatly improved. A highest ionic conductivity of 8.2 × 10−3 S cm−1 of Li5.6PS4.6Cl1.4 is obtained at room temperature. A high capacity retention of 99.99 % is maintained for NCM811 @Li2O//Li5.6PS4.6Cl1.4//Li-In system after 400 cycles at 1 C with ultra-high cathode loading of 35.6 mg cm−2. Besides, the cost of sulfide electrolytes can be reduced as the decreased usage of Li2S. This work proposes a novel synthesis method of low-cost and high-performance Li6−xPS5−xCl1+x electrolytes.

Flexible and thin sulfide-based solid electrolyte sheet with Li+-ion conductive polymer network for all-solid-state lithium-ion batteries

All-solid-state lithium batteries (ASSLBs) with solid electrolytes are promising battery systems capable of improving the safety and energy density of current lithium-ion batteries. Reducing the thickness of the solid electrolyte while preventing the short circuit between the anode and cathode is imperative to increase the energy density of ASSLBs. Sulfide-based solid electrolytes have high ionic conductivities; however, they are brittle, difficult to be processed into a thin film, and challenging to form stable interfaces with electrodes of large volume change. In this study, flexible thin-solid electrolyte sheets with Li+-ion conductive polymer network were prepared and characterized for ASSLB applications. They exhibited higher ionic conductance and superior mechanical properties than those of pristine Li6PS5X (argyrodite) pellets. The all-solid-state lithium-ion cell (graphite/LiNi0.7Co0.15Mn0.15O2) with a solid electrolyte sheet delivered a high discharge capacity of 182.5 mAh g−1 and showed good cycling stability at 0.33 C and 25 ℃, demonstrating that flexible and thin sheets are promising solid electrolytes for ASSLBs operating at room temperature.

The molding of the ceramic solid electrolyte sheet prepared by tape casting

Ceramic oxide solid-state electrolytes are more popular among researchers because of their excellent thermal stability, wide electrochemical window, excellent lithium-ion conductivity and high elastic modulus. Lithium-ion solid-state batteries with tantalum-doped Li6.4La3Zr1.4Ta0.6O12 (LLZTO) inorganic ceramic electrolytes have attracted much attention due to their extraordinary lithium-ion conductivity, incombustibility, and wide electrochemical window. Tape casting is a common method for ceramic molding, which is mainly used to prepare ceramic packaging substrate. However, the preparation process of casting slurry is tedious and time-consuming. In this study, a one-step vibration ball-milling method was proposed to prepare a non-aqueous-based casting slurry, which only took 2 hours. By optimizing the process parameters, the LLZTO solid electrolyte film prepared by tape casting had a uniform texture, and its thickness could be as thin as several microns. The perovskite-type LLZTO-independent ceramic electrolyte film with a thickness of 83 μm was prepared by tape casting. The Li+ ionic conductivity of the LLZTO solid-state electrolyte membrane is 2.0×10−5 S·cm−1. The Li-symmetric battery with all-solid-state lithium assembled using 83 μm thick LLZTO exhibited stable Li deposition and stripping properties.

Improvement of PEO-based composite solid electrolyte sheet using particle-size-controlled Ga-Rb-doped LLZO with high ion conductivity

In this study, a Li6.5Ga0.2La2.95Rb0.05Zr2O12 garnet-type solid electrolyte with high ion conductivity was prepared. The particle size was reduced to the nano size through a ball milling process, and the effect of the change in particle size on the all-solid-state batterie was investigated. As all-solid-state batteries have better stability than liquid electrolytes and serve as separators to help increase energy density, much research has been conducted recently. However, their conductivity is much lower than that of the liquid electrolyte. Therefore, an experiment was conducted on the difference in particle size to improve the ionic conductivity and energy density. Reducing the average particle size of the LLZO samples from approximately 10 to 0.6 μm using a ball milling process increased the ionic conductivity of the pellet from 1.27 × 10–3 to 1.58 × 10–3 S cm-1 at 25 °C. The ionic conductivity of the sheet decreased from 2.96 × 10–4 to 2.60 × 10–4 S cm-1 at 70 °C, but lithium transference number increased from 0.56 to 0.64. Therefore, the structural and electrochemical properties of the LLZO-bare and LLZO-ball-milled were investigated using powder X-ray diffraction analysis, field-emission scanning electron microscopy, electrochemical impedance spectroscopy, and galvanostatic measurements.

Film processing of Li6PS5Cl electrolyte using different binders and their combinations

The development of solid electrolytes has made significant progress in the last decade. Among the most promising materials, sulfide-based electrolytes show high ionic conductivities and low densities, and their precursors are abundant. For industrially relevant battery cells, sulfide electrolytes need to be processed to form thin electrolyte sheets that are either directly applied to the electrodes as coatings or prepared as stand-alone films. Thus, processing of sulfide electrolyte powders has recently drawn much attention as it seems to be one of the major challenges in realizing sulfide-based all-solid-state batteries.In this work, six different binders (NBR, HNBR, PIB, PBMA, SBS, SEBS) were selected for preparation of electrolyte films using Li6PS5Cl as a sulfidic model compound. The influence of the binders on the electrochemical performance as well as on the mechanical properties of the resulting films was investigated. In addition, binder blends were explored as a vial approach to optimize the properties of the electrolyte films. Special focus was put on elucidating the relation between the physico-chemical properties of the binder materials and the resulting electrochemical and mechanical properties of the electrolyte films.

Simulation Investigation on Thermal Characteristics of Thermal Battery Activation Process Based on COMSOL

Current thermal simulation methods are not suitable for small-size fast-activation thermal batteries, so this paper provides an improved simulation method to calculate thermal cell temperature changes using the COMSOL platform. A two-dimensional axisymmetric model of thermal batteries has been established, considering the actual heat release situation and the mobile heat source of thermal batteries. Based on it, the temperature change and electrolyte melting of thermal batteries under high-temperature conditions (50 °C) have been simulated, in which the temperature change law, thermal characteristics, and electrolyte melting characteristics have been analyzed in depth. The results show that the additional heating flakes and insulation design above and below the stack can effectively reduce heat loss. Most of the melting heat of the electrolyte flows in from the negative side. In addition, the thermal battery activation time has been calculated to be 91.2 ms at the moment when all the thermal battery electrolyte sheets begin to melt, and the absolute error was within 10% compared with the experimental results, indicating that the simulation model has high accuracy and can effectively broaden the simulation area of thermal batteries.

Synthesis of Garnet LLZO by Aliovalent Co-Doping, and Electrochemical Behavior of Composite Solid Electrolyte for All-Solid Lithium Batteries

Garnet-like Ga-M (M = Ta, Rb, Y) co-doped Li7La3Zr2O12 powders are prepared by the Taylor reaction, including Ga-LLZO, Ga-Ta LLZO, Ga-Rb LLZO, and Ga-Y LLZO. The lattice constant (12.97 Å) and large crystallite size (866 Å) of Ga-Rb LLZO powder enabled the highest ionic conductivity (2.03 × 10–3 S cm−1 at 25 °C) in the pellet form. Moreover, Ga-Rb LLZO powders are calcined in various temperature range and are utilized in composite solid electrolyte sheets consisting of Ga-Rb LLZO, polyethylene oxide, and salts. The ionic conductivity of the CSE sheets is increased in proportion to the calcination temperature in the range of 2.43 × 10−4 to 8.60 × 10−4 S cm−1 at 70 °C. The LLZO particle-size and crystallite-size requirements are differ for the cathode and CSE sheet. Three types of all-solid-state lithium batteries are designed, among which all-solid lithium batteries-3 employing Ga-Rb LLZO powder calcined at 900 °C and 1100 °C for the cathode and CSE sheet, respectively, exhibits an initial capacity of ∼139 mAh g−1 at 0.1C and 70 °C, with a capacity retention of ∼92% after 100 cycles. In particular, in terms of rate characteristics, 1C compared to 0.1C capacity shows excellent value, maintaining about 85%.

Improved the electrochemical performance between ZnO@Li1.3Al0.3Ti1.7(PO4)3 solid electrolyte and lithium metal electrode for all-solid-state lithium-ion batteries

Spherical Li1.3Al0.3Ti1.7(PO4)3 (LATP) solid electrolyte powders are first successfully synthesized by spray-drying and O2 pressure-controlled calcination processes, and then the targeted ZnO@LATP composite solid electrolytes are gained by coating 2 μm thickness of ZnO layer on the surface of the LATP powders, in which the ZnO layer effectively not only isolates the direct contact between LATP electrolyte sheet and lithium metal electrode, but also regulates the lithium deposition reaction on the surface of the electrolytes, thereby restraining the overgrowth of lithium dendrites to prolong the life span of the assembled coin cell. Specifically, the Li/ZnO@LATP@ZnO/Li symmetric cell enhances the cycle stability without obvious increment of the overpotential compared to the Li/LATP/Li cell at 0.4 mA cm−2 for 500 h, and the assembled LiCoO2/ZnO@LATP/Li coin cell can deliver excellent rate and cycling performance, in which the discharge specific capacity is still retained at 118.5 mAh g−1 after 100 cycles at 0.1 C and quickly recovers to 121.2 mAh g−1 when the current is set back to 0.1 C after cycles. Furthermore, the ZnO@LATP solid electrolyte powders after being cycled present integrally spherical shape without any remarkable crack compared with the LATP solid electrolyte powders. Therefore, the investigations may provide an effective strategy to significantly lower the probability of side reactions between LATP electrolyte and lithium metal electrode to promote the electrochemical properties of LATP-based all-solid-state lithium-ion batteries.

Fabrication of Oxide-Based All-Solid-State Batteries by a Sintering Process Based on Function Sharing of Solid Electrolytes.

Garnet-type Li7La3Zr2O12 (LLZ) has advantages of stability with Li metal and high Li+ ionic conductivity, achieving 1 × 10-3 S cm-1, but it is prone to react with electrode active materials during the sintering process. LISICON-type Li3.5Ge0.5V0.5O4 (LGVO) has the advantage of less reactivity with the electrode active material during the sintering process, but its ionic conductivity is on the order of 10-5 S cm-1. In this study, these two solid electrolytes are combined as a multilayer solid electrolyte sheet, where 2 μm thick LGVO films are coated on LLZ sheets to utilize the advantages of these two solid electrolytes. These two solid electrolytes adhere well through Ge diffusion without significant interfacial resistance. The LLZ-LGVO multilayer is combined with a LiCoO2 positive electrode and a lithium metal anode through annealing at 700 °C. The resultant all-solid-state battery can undergo repeated charge-discharge reactions for over 100 cycles at 25 or 60 °C. The LGVO coating suppresses the increases in the resistance from the solid electrolyte and interfacial resistance induced by annealing by ca. 1/40. As with sulfide-based all-solid-state batteries, function sharing of solid electrolytes will be a promising method for developing advanced oxide-based all-solid-state batteries through a sintering process.

LATP-coated NCM-811 for high-temperature operation of all-solid lithium battery

To achieve high-temperature operation of all-solid lithium batteries (ASLBs), LATP (Li1.3Al0.3Ti1.7(PO3)4) was coated on the surface of a high-nickel cathode material, NCM-811 powder (LiNi0.8Co0.1Mn0.1O2), by evaporation-induced self-assembly (EISA). Using EISA, the fine LATP precursor in ethanol was deposited on NCM-811 powder at loadings of 0.1–3 wt%, after which the precursor was dried and calcined at 750 °C. Although the X-ray diffraction (XRD) patterns of the coated samples were not significantly changed, the main peaks of NCM-811 were slightly shifted to lower angle by increasing LATP amount on NCM-811. Therefore, due to cation mixing in LATP-coated NCM-811, the lattice constant increased slightly, accompanied by a decrease in the factor c/3a. Transmission electron microscopy (TEM) showed that the thickness of the coating was 2, 5, and 8 nm for 0.5 wt%-, 1 wt%-, and 3 wt%-LATP-coated NCM-811, respectively. The LATP-coated NCM-811 samples were utilized as the active material in the composite cathode for ASLBs. The electrochemical behavior of single cells (LATP-coated NCM//composite solid electrolyte sheets//lithium metal) was evaluated at 70 °C. The cycle capacity retention was higher for the cell employing the cathode with 0.5 wt%-LATP-coated NCM-811 than for the other cells, with an initial discharge capacity of 138 mAh g−1 in the range of 3.0–4.1 V and capacity retention of 85% over 45 cycles. Moreover, the cycle retention of the cell was significantly improved compared with the electrochemical behavior of the existing ASLBs in which the cathode is prepared by simply mixing LATP powder with polyethylene oxide/salt and NCM-811 powder.

Development of high ionic-conductive Li1.5Al0.5Ge1.5(PO4)3 glass-ceramic solid electrolyte sheet at low temperature using glass/powder composite

Development of high ionic-conductive Li1.5Al0.5Ge1.5(PO4)3 glass-ceramic solid electrolyte sheet at low temperature using glass/powder composite

Hydrolysis of Argyrodite Sulfide-Based Separator Sheets for Industrial All-Solid-State Battery Production.

Researchers have been working for many years to find new material and cell systems that can be used as potential post-lithium-ion batteries. Among these, the all-solid-state battery is considered a promising candidate, with sulfide-based materials having essential advantages over other solid electrolyte materials, particularly in terms of their high ionic conductivity. A great challenge, however, is their high reactivity in contact with water, where harmful hydrogen sulfide (H2S) is formed. Since H2S formation has implications for both worker safety and material quality, it is important to quantify its impact. For this reason, this paper examines the relationship between the product properties and the H2S formation as well as influences resulting from the production environment. Exemplary material states along the process chain of a wet coating process route are analyzed for the steps of storage, mixing, coating, drying, and densifying with Li6PS5Cl (LPSCl) as a solid electrolyte material. By determining the H2S formation rate for sulfide-based separator sheets, it is shown that the water content in the surrounding atmosphere has the highest impact, while other investigated parameters are negligibly small in comparison. Among the product properties, the geometric surface and pore surface have a great influence. These results demonstrate the need for a controlled atmosphere in the production facilities at dew points of -40 to -50 °C. At those moisture levels, occupational safety and product quality are ensured for the investigated solid electrolyte sheets of LPSCl. This study is the first to provide quantitative data from the point of view of the production environment on the formation of H2S gas when using solid sulfide electrolytes and can therefore serve as a guideline for equipment, material, and cell manufacturers.

Local Lithium-Ion Transport of a Ternary Sulfolane-Lithium Bis(trifluoromethanesulfonyl)amide-Carbonate Electrolyte: Experimental and First-Principles Molecular Dynamics Analysis toward Quasi-Solid-State Lithium-Ion Battery

The ion coordination and local ion transport of the ternary electrolyte containing sulfolane (SL), lithium bis(trifluoromethanesulfonyl)amide (LiTFSA), and a carbonate solvent were investigated by combining the electrochemical measurement and first-principles molecular dynamics (FPMD) simulation. Li(SL)3TFSA solution with the low-viscosity carbonate solvents, propylene carbonate (PC) and butylene carbonate (BC) was quasi-solidified by nanosized SiO2 and PTFE binder. Electrochemical impedance spectroscopy revealed that the quasi-solidified electrolyte sheets exhibited the Li+ transport number of 0.5, which was higher than that of Li(G4)TFSA containing PC and the conventional organic liquid electrolyte. The higher Li+ transport number contributed to an enhanced discharge capacity of the LIB at a high rate, and the LIB with Li(SL)3TFSA-PC and Li(SL)3TFSA-BC based electrolyte exhibited higher capacity retention in cycle test compared with Li(G4)TFSA-PC. The FPMD analysis revealed that a bridging coordination by SL and TFSA, where a single SL or TFSA coordinates two Li+, was observed even under coexistence with the carbonate solvent. It was also confirmed that some Li+ tend to transfer independently to the other molecules/anions via the bridging coordination, leading to the high Li+ transport number. In conclusion, the composition design of the electrolyte to keep the bridging coordination is desirable for a high Li+ transport number and superior LIB performances.