Conductivity Of Solid Electrolytes Research Articles

Stable interfaces constructed by concentrated ether electrolytes to render robust lithium metal batteries

Lithium metal batteries (LMBs) are highly considered as promising candidates for next-generation energy storage systems. However, routine electrolytes cannot tolerate the high potential at cathodes and low potential at anodes simultaneously, leading to severe interfacial reactions. Herein, a highly concentrated electrolyte (HCE) region trapped in porous carbon coating layer is adopted to form a stable and highly conductive solid electrolyte interphase (SEI) on Li metal surface. The protected Li metal anode can potentially match the high-voltage cathode in ester electrolytes. Synergistically, this ingenious design promises high-voltage-resistant interfaces at cathodes and stable SEI with abundance of inorganic components at anodes simultaneously in high-voltage LMBs. The feasibility of this interface-regulation strategy is demonstrated in Li | LiFePO4 batteries, realizing a lifespan twice as long as the routine cells, with a huge capacity retention enhancement from 46.4% to 88.7% after 100 cycles. This contribution proof-of-concepts the emerging principles on the formation and regulation of stable electrode/electrolyte interfaces in the cathode and anode simultaneously towards the next-generation high-energy–density batteries.

Effects of microwave-assisted reflux in wet-chemical synthesis of high sodium-ion conductive Na5DySi4O12

Sodium rare-earth silicate with Na5DySi4O12 components is known as a highly conductive and stable sodium ion solid electrolyte though are difficulties in obtaining a single-phase, highly conductive Na5DySi4O12 pellet because it has low conductivity impurity phases. In this study, microwave heating for aqueous solution of starting materials was performed for the formation of homogeneous precursor of Na5DySi4O12. A single-phase Na5DySi4O12 was successfully obtained from the aqueous solution heated with 2.45GHz microwave at 80 °C after calcination at 700 °C and sintering at 1050 °C. The Na5DySi4O12 showed high conductivity of 2.9 × 10−4 at 30 °C and an activation energy of 0.25 eV. The precursor particles with microwave heating were fine particles with a narrower particle size distribution than those without microwaving. The results of thermal analysis showed different thermal behaviors with and without microwaves. The crystalline phase after calcination at 700 °C was different with and without microwave. After sintering at 1050 °C with microwaves was a single-phase Na5DySi4O12, but the pellets without the microwaves heating process did not have a crystalline phase of Na5DySi4O12. These results demonstrated that microwave heating of aqueous solution affects the formation of single-phase Na5DySi4O12.

Stress Regulation on Atomic Bonding and Ionic Diffusivity: Mechanochemical Effects in Sulfide Solid Electrolytes

External pressure is widely applied to the fabrication and assembling of solid-state batteries, which can reduce grain sizes, enhance solid–solid contacts, and further increase the ionic conductivity of solid electrolytes. However, the effect of stress on the intrinsic ionic conductivity of solid electrolytes is not yet fully understood. Herein, a comprehensive first-principles investigation was performed to elucidate the effect of tensile and compressive stresses on the ionic diffusivity of a sulfide solid electrolyte prototype Li10GeP2S12 (LGPS). A reduced and increased ionic diffusivity is observed in LGPS under compressive and tensile stress, respectively. Several descriptors, including the lattice volume, the neck size, the Li vacancy formation energy, and the Li Bader charge, are proposed to reveal the evolution of the ionic diffusivity in LGPS under stress. The ionic diffusivity in LGPS exhibits a better correlation with the activation energy than the pre-exponential factor, which suggests a synergy of stress and temperature on the ionic diffusivity. A more obvious change of ionic diffusivity as the stress is expected under lower temperatures. These results afford a fundamental and deep understanding of the mechanochemical effect in solid electrolytes.

Low‐Resistive LiCoO2/Li1.3Al0.3Ti2(PO4)3 Interface Formation by Low‐Temperature Annealing Using Aerosol Deposition

Interfacial resistance at electrode‐high Li+ conductive solid electrolytes must be reduced well to develop high‐power all‐solid‐state batteries using oxide‐based solid electrolytes (Ox‐SSBs). Herein, crystalline electrode films of LiCoO2 (LCO) are formed on a high Li+ conductive crystalline‐glass solid electrolyte sheet, Li1.3Al0.3Ti2(PO4)3 (LATP) (σ25 °C = 1 × 10−4 S cm−1), at room temperature by aerosol deposition (AD), and the effects of the annealing temperature on the interfacial resistivities (Rint) at the LCO/LATP are investigated. The Rint visibly increases by annealing over 500 °C with the growth of Co3O4 as a reactant. In contrast, Rint is reduced to ≈100 Ω cm2 by low‐temperature annealing at 250–350 °C due to superior contact through the structural rearrangement of an artificial metastable interface formed by the AD. These results are applied to bulk‐type Ox‐SSB, Li/Li7La3Zr2O12(LLZ)/LCO–LATP, and our best Ox‐SSB delivers a discharge capacity of 100 mA cm−2 at 100 °C.

In Situ Polymerization Permeated Three-Dimensional Li+-Percolated Porous Oxide Ceramic Framework Boosting All Solid-State Lithium Metal Battery.

Solid‐state lithium battery promises highly safe electrochemical energy storage. Conductivity of solid electrolyte and compatibility of electrolyte/electrode interface are two keys to dominate the electrochemical performance of all solid‐state battery. By in situ polymerizing poly(ethylene glycol) methyl ether acrylate within self‐supported three‐dimensional porous Li1.3Al0.3Ti1.7(PO4)3 framework, the as‐assembled solid‐state battery employing 4.5 V LiNi0.8Mn0.1Co0.1O2 cathode and Li metal anode demonstrates a high Coulombic efficiency exceeding 99% at room temperature. Solid‐state nuclear magnetic resonance results reveal that Li+ migrates fast along the continuous Li1.3Al0.3Ti1.7(PO4)3 phase and Li1.3Al0.3Ti1.7(PO4)3/polymer interfacial phase to generate a fantastic conductivity of 2.0 × 10−4 S cm−1 at room temperature, which is 56 times higher than that of pristine poly(ethylene glycol) methyl ether acrylate. Meanwhile, the in situ polymerized poly(ethylene glycol) methyl ether acrylate can not only integrate the loose interfacial contact but also protect Li1.3Al0.3Ti1.7(PO4)3 from being reduced by lithium metal. As a consequence of the compatible solid‐solid contact, the interfacial resistance decreases significantly by a factor of 40 times, resolving the notorious interfacial issue effectively. The integrated strategy proposed by this work can thereby guide both the preparation of highly conductive solid electrolyte and compatible interface design to boost practical high energy density all solid‐state lithium metal battery.

Black-Box Optimization for Automated Discovery.

In chemistry and materials science, researchers and engineers discover, design, and optimize chemical compounds or materials with their professional knowledge and techniques. At the highest level of abstraction, this process is formulated as black-box optimization. For instance, the trial-and-error process of synthesizing various molecules for better material properties can be regarded as optimizing a black-box function describing the relation between a chemical formula and its properties. Various black-box optimization algorithms have been developed in the machine learning and statistics communities. Recently, a number of researchers have reported successful applications of such algorithms to chemistry. They include the design of photofunctional molecules and medical drugs, optimization of thermal emission materials and high Li-ion conductive solid electrolytes, and discovery of a new phase in inorganic thin films for solar cells.There are a wide variety of algorithms available for black-box optimization, such as Bayesian optimization, reinforcement learning, and active learning. Practitioners need to select an appropriate algorithm or, in some cases, develop novel algorithms to meet their demands. It is also necessary to determine how to best combine machine learning techniques with quantum mechanics- and molecular mechanics-based simulations, and experiments. In this Account, we give an overview of recent studies regarding automated discovery, design, and optimization based on black-box optimization. The Account covers the following algorithms: Bayesian optimization to optimize the chemical or physical properties, an optimization method using a quantum annealer, best-arm identification, gray-box optimization, and reinforcement learning. In addition, we introduce active learning and boundless objective-free exploration, which may not fall into the category of black-box optimization.Data quality and quantity are key for the success of these automated discovery techniques. As laboratory automation and robotics are put forward, automated discovery algorithms would be able to match human performance at least in some domains in the near future.

Interface Aspects in All‐Solid‐State Li‐Based Batteries Reviewed

AbstractExtensive efforts have been made to improve the Li‐ionic conductivity of solid electrolytes (SE) for developing promising all‐solid‐state Li‐based batteries (ASSB). Recent studies suggest that minimizing the existing interface problems is even more important than maximizing the conductivity of SE. Interfaces are essential in ASSB, and their properties significantly influence the battery performance. Interface problems, arising from both physical and (electro)chemical material properties, can significantly inhibit the transport of electrons and Li‐ions in ASSB. Consequently, interface problems may result in interlayer formation, high impedances, immobilization of moveable Li‐ions, loss of active host sites available to accommodate Li‐ions, and Li‐dendrite formation, all causing significant storage capacity losses and ultimately battery failures. The characteristic differences of interfaces between liquid‐ and solid‐type Li‐based batteries are presented here. Interface types, interlayer origin, physical and chemical structures, properties, time evolution, complex interrelations between various factors, and promising interfacial tailoring approaches are reviewed. Furthermore, recent advances in the interface‐sensitive or depth‐resolved analytical tools that can provide mechanistic insights into the interlayer formation and strategies to tailor the interlayer formation, composition, and properties are discussed.

High Ionic Conductivity of Liquid-Phase-Synthesized Li3PS4 Solid Electrolyte, Comparable to That Obtained via Ball Milling

Recently, several sulfide solid electrolytes have been synthesized by liquid-phase synthesis for the commercialization of all-solid-state batteries. Unfortunately, the ionic conductivity for most of these electrolytes is unsatisfactory compared to that of solid electrolytes synthesized by conventional ball milling. This problem is attributed to different mechanisms between the liquid phase and the solid phase in reaction and formation. However, to the best of our knowledge, the effect of the solvent on the ionic conductivity of solid electrolytes has not been extensively investigated, although the identification of these properties is a key point in understanding the liquid-phase synthesis. Herein, the correlation between ionic conductivity and crystallinity originating from the solvents used has been investigated. As a result, the ionic conductivity of the electrolyte was found to be strongly dependent on polarity (δP) with low crystallinity. The highest ionic conductivity (5.09 × 10–4 S cm–1 at 25 °C) was obtained using butyl acetate, which exhibited the lowest δP. Moreover, the highest ionic conductivity of Li3PS4 produced by liquid-phase synthesis using butyl acetate was very comparable to that obtained by ball milling (5.14 × 10–4 S cm–1).

Electrolyte Design for In Situ Construction of Highly Zn2+ -Conductive Solid Electrolyte Interphase to Enable High-Performance Aqueous Zn-Ion Batteries under Practical Conditions.

Rechargeable aqueous Zn-ion batteries promise high capacity, low cost, high safety, and sustainability for large-scale energy storage. The Zn metal anode, however, suffers from the dendrite growth and side reactions that are mainly due to the absence of an appropriate solid electrolyte interphase (SEI) layer. Herein, the in situ formation of a dense, stable, and highly Zn2+ -conductive SEI layer (hopeite) in aqueous Zn chemistry is demonstrated, by introducing Zn(H2 PO4 )2 salt into the electrolyte. The hopeite SEI (≈140nm thickness) enables uniform and rapid Zn-ion transport kinetics for dendrite-free Zn deposition, and restrains the side reactions via isolating active Zn from the bulk electrolyte. Under practical testing conditions with an ultrathin Zn anode (10µm), a low negative/positive capacity ratio (≈2.3), and a lean electrolyte (9µL mAh-1 ), the Zn/V2 O5 full cell retains 94.4% of its original capacity after 500 cycles. This work provides a simple yet practical solution to high-performance aqueous battery technology via building in situ SEI layers.

MOF-derived multifunctional filler reinforced polymer electrolyte for solid-state lithium batteries

Solid-state lithium batteries (SSLBs) have attracted great interest from researchers due to their inherent high energy density and high safety performance. In order to develop SSLBs, the following two key problems should be solved: (1) Improving the lithium ion conductivity of solid electrolyte at room temperature; and (2) improving the interface between the electrode and the electrolyte. Herein, we propose a new multifunctional filler for reinforcing polymer electrolytes. The composite solid electrolytes (CSEs) mainly contain a MOF-derived Co-doped hollow porous carbon nanocage, which absorbs Li+ containing ionic liquid (Li-ILs@HPCN), polyethylene oxide (PEO) and lithium bis(trifluoromethanesulfonyl)imide. By optimizing the composition of the CSEs, the CSEs membrane with high ionic conductivity (1.91 × 10−4 S cm−1 at 30 °C), wide electrochemical stability (5.2 V) and high mobility of lithium ion (0.5) was obtained. Even at a current density of 0.2 mA cm−2, the PILH electrolyte possesses excellent interfacial stability against Li metal in Li symmetrical batteries exceeds 1600 h. Finally, the SSLBs (LFP/PILH/Li) showed excellent cycle stability, and the capacity was maintained at 152.9 and 140.0 mA h g−1 after 150 cycles at a current density of 0.2C and 0.5C. This work proposes a completely new strategy for building high-performance SSLBs.

Reactively sputtered Ta2O5 solid electrolyte layers in all thin film electrochromic devices

The tantalum pentoxide (Ta2O5) thin films used as protonic conductive solid electrolyte layers (SELs) in all thin film electrochromic devices (ATF-ECDs) were widely investigated. The working pressure played a great role in the microstructure and proton transfer of the Ta2O5 thin films. The Ta2O5 thin films were deposited by direct current (DC) reactive magnetron sputtering at different working pressures and growth mechanism was studied. The optical properties, structural properties, chemical compositions, morphologies and protonic conductive properties of the Ta2O5 thin films were systematically investigated. Moreover, the electrochromic properties for corresponding ATF-ECDs with Ta2O5 SELs were studied as well. The ATF-ECD with a 2.0 Pa Ta2O5 SEL exhibited the best device performance with high optical modulation and fast switch speeds.

Stabilizing electrode/electrolyte interface in Li-S batteries using liquid/solid Li2S-P2S5 hybrid electrolyte

Lithium-sulfur (Li-S) batteries using hybrid electrolytes, which are composed of solid-electrolyte separator and liquid-electrolyte wetting agent, can effectively eliminate the polysulfide shuttling issue. The cycling performance of these hybrid batteries is mainly limited by the interfacial stability between the solid and liquid electrolytes. This work detailly discusses the influence of the composition on the stability of a highly ionic conductive sulfide solid electrolyte, lithium thiophosphate xLi2S·(100–x)P2S5 (70 ≤ x ≤ 75, SSEs), in hybrid Li-S batteries. It reveals that the solid electrolyte with low Li2S content favors the formation of a SEI layer containing Li3PS4 and therefore improves the interfacial stability with Li anode, while the one with high Li2S content behaves more stable with the cathode. Using 75Li2S·25P2S5 as the separator, a hybrid battery runs more than 400 cycles with a low capacity fading rate of 0.14%/cycle. This is benefited from the elimination of polysulfide shutting and especially the excellent compatibility of the sulfide solid electrolyte with both anode and cathode.

Effect of MnO2 Dopant on Properties of Na+-β/β"-Al2O3 Solid Electrolyte Prepared by a Synthesizing-cum-sintering Process

In order to simplify the complexity of the conventional solid-state reaction process, Na+-β/β″-Al2O3 as a fast Na+-ionic conductive solid electrolyte was fabricated using a synthesizing-cum-sintering process combined with the double-zeta method, which is able to distribute a small amount of Li2O more homogeneously in the Na2O-Al2O3-Li2O system. Additionally, in order to enhance the ionic conductivity, MnO2 was used as a dopant to increase the Na+-ion concentration on the conduction plane in the Na+-β/β″-Al2O3 crystal structure. The relative sintered density increased with the synthesis temperature, ultimately reaching 99.7 % after synthesis at 1400 °C. The phase formation showed an overall β″-phase fraction over 90 %. The addition of MnO2 had a positive effect on the phase formation, but a negative influence on the relative density resulting from the grain growth promotion effect. The highest ionic conductivity was observed at 1.74 × 10-1 S/cm (350 °C) for the sample sintered at 1600 °C with 0.5 wt.% MnO2.

Structures and conductivities of stable and metastable Li5GaS4 solid electrolytes.

Understanding the differences in the structures and defects in the stable crystalline phase and metastable phase is important for increasing the ionic conductivities of a solid electrolyte. The metastable phase often has higher conductivity than the stable phase. In this study, metastable lithium thiogallate, Li5GaS4, was synthesized via mechanochemistry and stable Li5GaS4 was obtained by heating the metastable phase. The metastable Li5GaS4 sample was found to have an antifluorite-type crystal structure with cationic disorder, while the stable phase was found to have a monoclinic crystal structure, similar to that of another solid electrolyte, Li5AlS4. In both the structures, the Ga3+ cations were surrounded by four S2− anions in tetrahedral coordination. The conductivity of the metastable phase was determined to be 2.1 × 10−5 S cm−1 at 25 °C, which is 1000 times greater than that of the monoclinic phase. The high conductivity of the metastable phase was achieved owing to cation disorder in the crystal structure.

Single-step ball milling synthesis of highly Li+ conductive Li5.3PS4.3ClBr0.7 glass ceramic electrolyte enables low-impedance all-solid-state batteries

Single-step ball milling synthesis of a highly conductive glass ceramic solid electrolyte enables a low-impedance all-solid-state battery.

A composite solid electrolyte with an asymmetric ceramic framework for dendrite-free all-solid-state Li metal batteries

A novel CSE with an asymmetric dual-layer ceramic framework was developed to simultaneously improve the ionic conductivity of solid electrolytes and ameliorate the Li dendrite formation in ASSLMBs.

Gas-phase computational study of tetra-n-butylammonium ion conformational mobility

The energy profiles of various configurations of the tetra-n-butylammonium ion (Bu4N+) arising by changing the angle between a pair of butyl ligands, as well as by rotating of various alkyl fragments in gas phase, were calculated using DFT methods. A hypothesis about the most probable way of changing the conformations of tetra-n-butylammonium ions during the phase transitions in highly conductive solid electrolytes was proposed.

High Ionic Conductivity Achieved in Li3Y(Br3Cl3) Mixed Halide Solid Electrolyte via Promoted Diffusion Pathways and Enhanced Grain Boundary

The development of all-solid-state batteries is limited by the low ionic conductivity of solid electrolytes. Beyond sulfides and oxides, halides represent another family of solid electrolytes with ...

(Invited) Oxide-Based All-Solid-State Batteries Prepared By Aerosol Deposition

Oxide-based all-solid-state batteries (OX-SSBs) have been expected as next generation rechargeable batteries. Although various kinds of high Li+ conductive solid electrolytes have been prepared such as Li7La3Zr2O12 (LLZ), NASICON-structured Li1.3Al0.3Ti2(PO4)3 (LATP), LiTaPO4 etc, there are serious problems to develop low-resistive positive electrode/high Li+ conductive solid electrolyte interface. Because these high Li+ conductive solid electrolytes are crystallized at 800-1000 ℃, high temperature sintering is common way to combine them with conventional crystalline insertion electrode materials (LiCoO2 (LCO), LiNi1/3Co1/3Mn1/3O2 (NCM111) etc). However, both electrodes and solid electrolytes are composed of different elements with different concentrations, such high temperature sintering process frequently provide mutual diffusion region around the interface in addition to structural degradation and then seriously impede the interfacial resistance. Thus, one strategy to prevent those side reactions will be to apply low temperature sintering or densification process. We have focused on aerosol deposition, AD, a room temperature ceramic coating process. AD can realize quick speed and wide area ceramic coating and has been estimated as a cost-effective process technology for oxide-based energy conversion devices. AD make it possible to prepare electrode-solid electrolyte composite electrodes at room temperature and LiCoO2 film electrode on LiPON film. In addition, AD enables us to investigate the effects of annealing temperature on the interfacial resistances and then limiting temperature for sintering.In this presentation, our recent works on Ox-SSBs using the AD will be introduced 1) 4V- and 5V-class bulk-type Ox-SSBs, 2) effects of annealing temperature on interfacial resistivity, an example of LCO-LATP system to determine limiting temperature for sintering.

Calculational Clarification of the Reduction Factors Against Ionic Conductivity of Solid Electrolyte in All-Solid-State Battery

All-solid-state batteries are desired to be used especially for electric vehicles due to the expected features for rapid charging, safety, and unnecessity of battery cooling systems. In recent years, solid electrolytes with high ionic conductivity have been developed.1 However, it is known that the effective ionic conductivity in the electrode is significantly lower than that expected from the conductivity of the solid electrolytes.2,3 The conductivity reduction is possibly caused by the tortuosity of active materials as well as the resistance of the grain boundaries. In this study, the quantitative clarification of these factors has been carried out by numerical analysis.As a preliminary study, the conductivity of a simple solid electrolyte layer was investigated. The reduction of the ionic conductivity is possibly caused by the three factors shown in Fig. 1. The first factor is the tortuosity of the ion-conduction path in the layer. The tortuosity is the ratio of the path length to the layer thickness, and the presence of vacancy in the layer increases the tortuosity. The second factor is the contact area of the solid electrolyte particles. The small contact area causes the bottleneck structure of the particles which reduces the conductivity. The third factor is the contact resistance of the particles. The increase in the resistance is probably caused by the mismatch of the crystal lattice at the contact area. Since the shape of ionic conduction path governs the first and second factors, we named these factors as path resistances. The second factor can be regarded as an apparent increase in the path length. Hence, the product of the path resistances was defined as path resistance coefficient.The experimental conductivity was measured with the layer of an argyrodite-type sulfide-based solid electrolyte. The porosity was controlled by changing the confining and molding pressure and the effective ionic conductivity was obtained from the electrochemical impedance measurement. In the calculation, the ionic conductivity was evaluated only from the path resistances using the random walk method4 and the effect of the third factor was not considered. The structural information was obtained from the cross-sectional SEM images of the solid electrolyte layers with different porosities.Although the calculation excludes the third factor, i.e., contact resistance, the calculated conductivity corresponds well to the experimental values as in Fig. 2. This suggests that the contact resistance is negligible in the electrolyte layer. In addition, the first and second factors were numerically separated. At the porosity of 30%, the path resistance coefficient was calculated as 3.0 while the first tortuosity factor was 1.2. From equation 1, the second factor can be evaluated as 2.5, showing this factor is mainly responsible for the reduction of the ionic conductivity in the system.In this presentation, we will refer a model based on the concept of the path resistance described above to predict the effective ionic conductivity of the electrode layer containing active materials.AcknowledgmentsThis study was performed in SOLiD-EV project supported by NEDO (New Energy and Industrial Technology Development Organization).References Y. Kato, S. Hori, T. Saito, K. Suzuki, M. Hirayama, A. Mitsui, M. Yonemura, H. Iba, and R. Kanno, Nat. Energy, 1, 16030 (2016).T. Asano, S. Yubuchi, A. Sakuda, A. Hayashi, and M. Tatsumisago, J. Electrochem. Soc., 164, (14), A3960 (2017).D. Hlushkou, A. E. Reising, N. Kaiser, S. Spannenberger, S. Schlabach, Y. Kato, B. Roling, and U. Tallarek, J. Power Sources, 396, 363 (2018).G. Inoue and M. Kawase, J. Power Sources, 342, 476 (2017). Figure 1