Use Of Solid Electrolytes Research Articles

Scalable Synthesis and Electrochemical Study of Ceramic-Polymer Nanocomposite Solid Electrolytes for Solid-State Battery Manufacturing

Solid-state lithium batteries (SSBs) have the potential to achieve high energy and power densities due to the use of solid electrolytes (SEs) that are compatible with lithium metal or silicon-based anodes. However, fabrication of SEs with good ionic conductivity, mechanical strength, electrochemical stability, and interfacial contact with solid electrodes have been challenging. One promising approach is to combine ceramic lithium conductors that is expected to show a relatively high room-temperature Li-ion conductivity and a soft polymer matrix that facilitates mechanical integrity at the electrode-electrolyte interface during charge-discharge cycling. In this study, we report a scalable synthesis of Al0.25Li6.25La3Zr2O12 (LLZO) nanofibers and polyethylene oxide (PEO) composite SEs using roll-to-roll manufacturing. Our LLZO fibers showed 0.3 mS/cm conductivity at room temperature and the LLZO-PEO composites showed three times higher critical current density than a single PEO polymer electrolyte. Microstructural and electrochemical properties of the composite electrolytes will be discussed.

Interfacial Dynamics Study of NCM523-Based Semi-Solid-State Lithium-Ion Batteries by Electrochemical Impedance Spectroscopy.

The use of solid electrolytes (SE) in solid-state batteries holds the promise of achieving higher energy densities and enhancing safety. However, current solid-state batteries face significant interface impedance issues, mainly dealing with the effect of the evolution of the solid-solid interface on ion transport. Semi-solid-state batteries (SSB), containing a small amount of liquid electrolyte, serve as appropriate transitional products in the development process of solid-state batteries. More importantly, the clarity of the relevant interface dynamics can provide theoretical guidance for the subsequent all-solid-state batteries. Therefore, this paper investigates SSB through Electrochemical Impedance Spectroscopy (EIS), primarily employing a combination of theoretical modeling, simulation predictions, and experimental analyses to elucidate the complex electrochemical processes within these batteries. Based on detailed exploration of the complex electrochemical processes within SSB, we have discovered additional electrochemical processes beyond Li+ penetration through the solid-electrolyte interphase (SEI) film and charge transfer. We attribute the additional electrochemical reaction processes to the resistance present at the SE/SEI interface of SSB on account of numerical analysis and interface characterization. Furthermore, this interface resistance exhibits a trend of initial decrease followed by continuous increase, elucidating the attribution and numerical variations of various impedance components within the EIS. The application of EIS techniques to analyze ion transport processes in SSB serves as a suitable transition toward achieving all-solid-state batteries as well as provides guidance for subsequent interface optimization of solid-state batteries and propels their transition from laboratory experimentation to commercialization.

Advances in electrolyte–anode interface engineering of solid‐state lithium metal batteries

AbstractSolid‐state lithium metal batteries are considered to be the next generation of energy storage systems due to the high energy density brought by the use of metal lithium anode and the safety features brought by the use of solid electrolytes (SEs). Unfortunately, besides the safety features, using SEs brings issues of interfacial contact of lithium anode and electrolytes. Recently, to realize the application of solid‐state lithium metal batteries, significant achievements have been made in the interface engineering of solid‐state batteries, and various new strategies have been proposed. In this review, from the interface failure perspective of solid‐state lithium metal batteries, we summarize failure mechanisms in terms of poor physical contact, weak chemical/electrochemical stability, continuing contact degradation, and uncontrollable lithium deposition. We then focused on the latest strategies for solving interface issues, including advancing in improving the physical solid–solid contact, increasing the electrochemical/chemical stability, restraining continuing contact degradation, and controlling homogeneous lithium deposition. The ultimate and paramount future developing directions of solid‐state lithium metal battery interface engineering are proposed.

Ternary stabilization strategies for succinonitrile-based in situ polymerized electrolyte enabling high-performance solid lithium metal batteries

Solid-state lithium metal batteries with high energy density and safety have gained increasing attention due to their potential applications. However, the practical use of solid electrolytes is hindered by several challenges. These include poor compatibility at the electrode–electrolyte interface, low ionic conductivity at room temperature, and fast capacity degradation. To address these issues, here we propose ternary strategies by in-situ cross-linked plastic crystal electrolyte (in-situ PCE) based on succinonitrile (SN). Through the in-situ polymerization of SN with polyacrylonitrile/poly(vinylidene difluoride) (PAN/PVDF) nanofibers separator, excellent mechanical strength and compatibility at the electrode–electrolyte interface are achieved. The cross-linked structure of thermally polymerized ethoxylated trimethylolpropane triacrylate (ETPTA) immobilizes the SN molecule, preventing its contact with the lithium metal and inhibiting irreversible side reactions. Additionally, a LiF-rich passivation layer is employed to further protect the SN at the electrolyte-lithium metal interface. The dual protection from ETPTA and LiF offers excellent stability to lithium. Hence, the in-situ PCE exhibits high ionic conductivity (0.79 mS cm−1 at 30 °C) and wide electrochemical window (4.56 V, vs Li+/Li). The cells exhibit excellent cycling stability and high-rate performance. LiFePO4//Li cells retain 96.6 % capacity after 1000 cycles at 10C rate. This study provides valuable insights into the development of high-performance solid-state electrolytes.

Approaching high rate All-Solid-State Lithium-Sulfur batteries via promoted sulfur conversion with nickel oxide nanoparticle electrocatalyst

All-solid-state lithium-sulfur battery (ASLSB) is deemed a promising next-generation energy storage device owing to its combination of high theoretical specific energy (2600 Wh kg−1) derived from the sulfur active material, and exceptional safety characteristics and the ability to suppress the polysulfide shuttle effect through the use of solid electrolyte (SE). However, the low electronic and ionic conductivity of sulfur, coupled with the poor solid–solid interfacial contact inherent in all-solid-state configuration, has resulted in poor electrochemical performance. Herein, NiO electrocatalyst supported on N-doped sites of super-p was synthesized and incorporated as a carbon additive in the composite cathode of the ASLSB. The direct growth of nanosized NiO electrocatalyst on the N-doped sites of super-p ensures facile electron transfer to the electrocatalyst surface, while maximizing the electrocatalyst’s surface area. As a result, the overpotential during charging and discharging of the ASLSB was significantly reduced, as assessed through galvanostatic intermittent titration technique and cyclic voltammetry, indicating enhanced redox conversion of sulfur. Furthermore, the Li6PS5Cl sulfide SE induces solid–solid conversion of sulfur, eliminating the dissolution issue of polysulfide intermediates and ensuring good cycle performance. The assembled ASLSB exhibits a high reversible capacity of 1845 mAh g−1 at 0.05C at room temperature and enhanced rate capability at high C-rates, operated at 60 °C. Even at a substantially high sulfur loading level of 6.65 mg cm−2, a maximum areal capacity of 9.48 mAh cm−2 was achieved at room temperature, highlighting the important role of electrocatalyst in realizing high performance ASLSBs.

Optimization strategy for metal lithium negative electrode interface in all-solid-state lithium batteries

Lithium metal is a perfect anode material for lithium secondary batteries because of its low redox potential and high specific capacity. In the future, solid-state lithium batteries constructed with embedded lithium anodes, solid-state electrolytes, and lithium metal anodes are anticipated to power electric cars, robots, high-end electronics, aircraft, and other relevant technological industries. However, as a result of the uneven deposition and dissolution of lithium during the charging and discharging process, a large number of dendritic dendrites form on the lithium-electrolyte contact surface and grow along the electrolyte’s direction, ultimately resulting in an internal short circuit that causes the battery to fail. Although the development of lithium dendrites can be substantially inhibited by the use of solid electrolytes with high Young’s modulus, long cycle and safety criteria are still not met. Furthermore, high interfacial resistance and interfacial interaction between lithium metal and solid electrolyte are issues brought on by the solid-solid contact between the two materials, which substantially impedes the creation and use of solid-state lithium-metal batteries. This paper first explains the growth principle of lithium dendrites. Then, the optimization strategy of the negative electrode interface is introduced. Finally, the future development trend of solid-state lithium batteries is overlooked.

Organic Modification of Silica-Based Ionogels Improves the Electrolyte/Electrode Contact and Influences Their Functional Properties

The energy transition necessitates sustainable energy storage to address the mismatch between the production and consumption of renewable electricity. Sodium-ion batteries (SIBs) are a promising candidate for stationary energy storage as an alternative for lithium-ion batteries (LIBs). In spite of their lower energy density, SIBs have advantages over LIBs.1 Sodium is considerably more abundant than lithium (2.83% versus 0.01%) and, evenly distributed across the Earth, implying that SIBs may be less expensive and more sustainable than LIBs.1,2 Conventional LIBs contain flammable organic liquid electrolytes (e.g. alkyl carbonates) with limited thermal stability. Thermal runaway can therefore lead to cell ignition, causing a significant safety hazard. Non-flammable electrolytes can be based on ionic liquids, which are molten salts with flame retarding properties and negligible vapor pressures. However, the possibility of leakage and related environmental hazards remains a concern.3 This risk can be mitigated by the use of solid electrolytes. Apart from circumventing safety issues, solid electrolytes may allow a significant increase in energy density. After all, they take up less dead volume than liquid electrolytes and can allow the use of alkali metals as negative electrodes.An attractive type of solid electrolyte is the class of silica-based ionogels, owing to their high ionic conductivity, thermal stability, and broad electrochemical window.4 They comprise an ionic liquid electrolyte (ILE, a salt dissolved in ionic liquid) confined in the pores of a solid silica matrix. The silica matrix is electrochemically inactive but influences the functional properties of the resulting solid material. Ionogels based on solely silica (SiO2) as matrix tend to crack easily when subjected to pressure as the rigid Si-O-Si bonds result in high Young’s modulus materials. Furthermore, materials with high Young’s moduli cannot adapt easily to electrode surfaces, resulting in higher charge-transfer resistances (Rct) between the solid electrolyte and electrode. One way to reduce the stiffness of silica-based ionogels is to modify the silica matrix with e.g. organic groups. Ormosils® are a class of materials completely consisting of organically modified silica and show mechanical properties from glassy to rubbery depending on the amount of organic modification.5 Here, the concepts of ionogels and Ormosils® are combined to produce sodium-ion conducting organically modified ionogels. Two different phenyl-bearing silanes (phenyltrimethoxysilane, PhTMS, or diphenyldimethoxysilane, DPhDMS) are for the first time used as organic modifiers in silica-based ionogels. A non-aqueous sol-gel route with formic acid (FA) is used to synthesize the monoliths. Incorporating phenyl groups allow to reduce the Young’s modulus from 29 MPa down to 6 MPa. The charge-transfer resistances (Rct) of Na|ionogel|Na2Ti3O7 half cells, determined with electrochemical impedance spectroscopy (EIS), followed the trend of the ionogels’ Young’s modulus. Through NMR spectroscopy, pi-stacking was observed between the matrix phenyl moieties and IL imidazolium cations. Furthermore, the organic modification diminished the formation of hydrogen bonds between IL anions and matrix silanol groups. This shows that the organic modification of the matrix can have a pronounced effect on the coordination of the ILE components, which ultimately determine the solid electrolyte’s functional properties. In summary, incorporating phenyl groups in the silica matrix of ionogels improves the mechanical properties and charge transfer resistances, but impairs ionic conductivity. Acknowledgments: This research is made possible by the Research Foundation Flanders (FWO, project G053519N and 1S08921N) and the Special Research Fund (BOF) of Hasselt University (BOF20INCENT19). This work is further supported by Hasselt University and FWO Vlaanderen via the Hercules project AUHL/15/2 - GOH3816N.

Understanding the Effect of Mechanical Degradation on the Performance of Solid-State Batteries through Particle Simulations

All-solid-state batteries (ASSBs) have garnered significant interest as a promising alternative to conventional lithium-ion batteries, offering improved safety, higher energy density, longer lifespan, faster charging and wider operating temperature range. A key advantage of ASSBs is the use of solid electrolytes (SE), which eliminate the risks associated with flammable liquid electrolytes. However, the complex electrochemical behavior and multi-scale nature of ASSBs pose challenges in designing and optimizing their performance. This study employs Discrete Element Method (DEM) particle-based models to better understand degradation behavior of ASSBs by considering electrochemical reaction, mass and charge transfer, intercalation expansion and material deformationOur simulations were developed in MATLAB and were performed on a half-cell configuration comprising a SE-layer and an anode electrode. The anode electrode was composed of a particle mixture containing active material (AM) and SE. In our simulations, Si was employed as AM, which experiences substantial intercalation expansion during charge cycling 1. Our previously developed DEM model2,3 resolved elastic and plastic deformation of both AM and SE particles which become compressed due to the intercalation expansion. The simulation of intercalation was achieved by integrating the Newman electrochemical model,4 into the DEM mechanical model. Building on our earlier study5, where the Li concentration was resolved within each AM particle, this study is also accounting for the Li-ion potential within each SE particle. Interparticle conduction and diffusion were computed by determining the contact area of AM-AM and SE-SE contacts, which were affected by the compression of the electrode. The electrochemical reaction was calculated at the AM-SE interface using the Butler-Volmer equation, and in addition the influence of compressive stress on the reaction6 was included.Figure 1(a) depicts the Li concentration and Li-ion potential distribution within the half-cell during charging at different states of charge (SOC), while Figure 1(b) provides a 3D view of the distributions at a SOC of 50%. A considerable expansion of the Si anode is evident. The gradients of Li concentration and Li-ion potential signify significant mass and charge transfer resistance during the charging process. Comparing the distribution of the particles, the anode becomes more porous after the first cycle for the same value of SOC. This effect is attributed to the extensive expansion of the Si anode, leading to plastic compression of the SE layer, which becomes more compact after each cycle. The growing porosity diminishes the contact area between particles, ultimately resulting in the degradation of the half-cell's capacity. In addition to SE-layer compaction, this study aims to investigate several degradation mechanisms and their impact on the performance of ASSBs, including the development of shell voids resulting from AM-SE delamination, crack propagation through SE, and fragmentation of AM.The results of this study provide valuable insights into understanding the effect of mechanical degradation on the performance of ASSBs. By improving our understanding of these mechanisms, we can work towards enhancing the durability and lifespan of ASSBs, ultimately contributing to the development of next-generation energy storage systems. Acknowledgment This work was supported by JSPS KAKENHI Grant-in-Aid for Scientific Research on Innovative Areas, “Science on Interfacial Ion Dynamics for Solid State Ionics Devices, Computational & Data Science” (Gp-A03, grant number 19H05815); and MEXT “Program for Promoting Researches on the Supercomputer Fugaku” (Fugaku battery & Fuel Cell Project), grant number JPMXP1020200301. References M. N. Obrovac and L. Christensen, Electrochem. Solid-State Lett., 7, A93 (2004).M. So, G. Inoue, R. Hirate, K. Nunoshita, S. Ishikawa, and Y. Tsuge, J. Electrochem. Soc., 168, 030538 (2021).M. So, G. Inoue, R. Hirate, K. Nunoshita, S. Ishikawa, and Y. Tsuge, Journal of Power Sources, 508, 230344 (2021).J. Newman and K. E. Thomas-Alyea, Electrochemical Systems, 3rd edition., p. 672, Wiley-Interscience, Hoboken, N.J, (2004).M. So, S. Yano, A. Permatasari, T. D. Pham, K. Park, and G. Inoue, Journal of Power Sources, 546, 231956 (2022).G. Bucci, T. Swamy, S. Bishop, B. W. Sheldon, Y.-M. Chiang, and W. C. Carter, J. Electrochem. Soc., 164, A645 (2017). Figure 1

Solidification of a Silica-Based Solid Composite Electrolyte for Lithium-Ion Batteries Induced By UV Irradiation

The use of solid electrolytes in lithium-ion batteries (LIBs) instead of their liquid counterparts may significantly increase their energy density. Of particular interest are solid composite electrolytes (SCEs) which can be synthesized by incorporating ionic liquids (ILs, salts with a melting point lower than 100 °C) into a solid matrix. This class of SCE can have a wide electrochemical stability window and is typically non-flammable.Chen et al.1 developed an SCE with excellent ionic conductivity, consisting of a mesoporous silica monolith which encloses an IL electrolyte (solid nanocomposite electrolyte or nano-SCE). It is formed from a precursor solution which does not contain acids such as formic acid or HCl, meaning that it can be impregnated into porous electrodes without causing damage to the latter. However, its gelation process is long and variable (5-9 days), and is considerably affected by its presence within the electrode. As such, the nano-SCE has poor manufacturability and is not compatible with the continuous roll-to-roll processing typically used for LIB manufacturing. The manufacturability of the nano-SCE can be significantly improved by making its solidification process instantaneous upon subjection to an external trigger.As such, organic modification was used to produce silica-based precursor solutions capable of triggered solidification, for instance by irradiation with UV light. This solidification process takes a few minutes to complete and does not depend on pH, rendering it particularly versatile. The aging of the precursor solutions was studied with 29Si, 1H, and 13C NMR spectroscopy, which revealed that the alkoxysilane precursor molecules condensed into larger soluble structures over the course of five weeks. The aged precursor solutions remained stable over an indefinite period of time. When a photo-initiator is added to these solutions and they are irradiated with UV light, the soluble structures are linked together, resulting in the formation of silica nanoparticles which subsequently aggregate into a porous matrix which encapsulates the ionic liquid electrolyte (ILE).The adaptation does not compromise the functional properties such as ionic conductivity or electrochemical stability. As determined with Raman spectroscopy, the extent of organic modification and amount of ILE can be optimized to decrease the interaction of lithium ions with the other ions as compared to the neat ILE. The increased Li+ mobility means that the SCE can reach higher ionic conductivity (2.7 mS cm-1 at 20 °C) values than the neat ILE (2.5 mS cm-1). Anodic and cathodic linear sweep voltammetry in three-electrode cells was performed to determine that the SCEs can have an electrochemical stability window exceeding 5 V (i.e. lithium plating < 0 vs Li+/Li and electrolyte oxidation > 5.0 V vs Li+/Li). Electrochemical impedance spectroscopy further confirmed the SCE’s compatibility with lithium metal. As no acids are added to the precursor solution, a good electrode compatibility is expected. As such, the precursor solutions were impregnated into NMC622-based electrodes, solidified, and incorporated in half cells. These cells had an initial discharge capacity of 162 mAh g-1 at 0.1 C, retaining 86.8% of this capacity after 100 cycles.This work was supported by funding from the European Union’s Horizon 2020 research and innovation program for the Solidify project under grant agreement No. 875557.(1) Chen, X.; Put, B.; Sagara, A.; Gandrud, K.; Murata, M.; Steele, J. A.; Yabe, H.; Hantschel, T.; Roeffaers, M.; Tomiyama, M.; et al. Silica Gel Solid Nanocomposite Electrolytes with Interfacial Conductivity Promotion Exceeding the Bulk Li-Ion Conductivity of the Ionic Liquid Electrolyte Filler. Sci. Adv. 2020, 6 (2). https://doi.org/10.1126/sciadv.aav3400.

Recycling of All-Solid-State Li-ion Batteries: A Case Study of the Separation of Individual Components Within a System Composed of LTO, LLZTO and NMC.

With the current global projection of over 130 million electric vehicles (EVs), there soon will be a need for battery waste management. Especially for all-solid-state lithium-ion batteries (lithium ASSBs), aspects of waste management and circular economy have not been addressed so far. Within such ASSBs, the use of solid-electrolytes like garnet-type Li6.5 La3 Zr1.5 Ta0.5 O12 (LLZTO) may shift focus on strategies to recover not only the transition metal elements but also elements like La/Zr/Ta. In this work, we present a two-step recycling approach using citric acid as the leaching agent to separate and recover the individual components of a model cell comprising of Li4 Ti5 O12 (LTO) anode, Li6.5 La3 Zr1.5 Ta0.5 O12 (LLZTO) garnet electrolyte and LiNi1/3 Mn1/3 Co1/3 O2 (NMC) cathode. We observe that by adjusting the concentration of citric acid, it was possible to separate the materials from each other without strong mixing of individual phases and also to maintain their principle performance characteristics. Thus, the process developed has a potential for upscaling and can guide towards considering separation capability of battery components in the development of lithium ASSBs.

Pressure Dependence of Solid Electrolyte Ionic Conductivity: A Particle Dynamics Study.

The search for safe, reliable, and compact high-capacity energy storage devices has led to increased interest in all-solid-state battery research. The use of solid electrolytes provides enhanced safety and durability due to their reduced flammability and increased mechanical strength compared to organic liquid electrolytes. Still, the use of solid electrolytes remains challenging. A significant issue is their generally low Li-ion conductivity, which depends on the lattice diffusion of Li ions through the solid phase, as well as on the limited contact area between the electrolyte particles. While the lattice diffusion can be addressed through the chemistry of the solid electrolyte material, the contact area is a mechanical and structural problem of packing and compression of the electrolyte particles depending on their size and shape. This work studies the effect of pressurization on the electrolyte conductivity exploring cases of low as well as high grain boundary (GB) conductivity, compared to the bulk conductivity. Scaling dependence, σ ∼ Pη, of the conductivity σ with pressure P is revealed. For an idealized electrolyte represented as spheres in hexagonal closely packed configuration, η = 2/3 and η = 1/3 have been theoretically calculated for the two cases of low and high GB conductivity, respectively. For randomly packed spheres, the equivalent exponent values were numerically estimated to be approximately 3/4 and 1/2, respectively, which are higher than the closed packed values due to the additional decrease of porosity with the increase in pressure. As demonstrated in the study, experimental measurement of η can indicate which type of bulk or GB conductivity is dominant in a particular electrolyte powder and could be used in addition to electrochemical impedance spectroscopy measurements.

An ultrafast rechargeable and high durability lithium metal battery using composite electrolyte with the three-dimensional inorganic framework by Li6.4La3Zr1.4Ta0.6O12 surface functionalization

The liquid electrolyte used in traditional lithium-ion batteries has risks of leakage, combustion and explosion. Solid electrolyte is one of the effective strategies to solve the safety problems of lithium-ion batteries. And the use of solid electrolytes makes it possible to use lithium metal as an anode to achieve higher energy densities. At present, the main factors restricting the performance improvement of all-solid-state lithium batteries are the low electrochemical performance of electrolytes and poor solid-solid interface contact. The composite electrolyte has the advantages of both inorganic materials and polymers, but its electrochemical performance is still not up to the requirements of use. In situ synthesis of LaRuO3 with perovskite structure on the surface of Li6.4La3Zr1.4Ta0.6O12(LLZTO) induces the formation of Li2Zr2O7 while introducing defects. The Li2Zr2O7 phase "welds" inorganic particles into three-dimensional(3D) inorganic framework, increasing the reaction sites between inorganic fillers and polymers. Compared with the primitive sample, the ionic conductivity of the modified electrolyte is increased by an order of magnitude at room temperature, wherein the lithium-ion conductivity of the composite electrolyte with 3% LaRuO3 is as high as 6.06 × 10−4 S cm−1. At 5C, the discharge specific capacity of LiFePO4 | [email protected] 3% LRO | Li can reach 114.6 mAh g−1; After 400 cycles, the discharge specific capacity remains at 129.6 mAh g−1. Under the same conditions, the discharge specific capacities of the unmodified samples are only 92.4 mAh g−1 and 35 mAh g−1. The high rate discharge performance of solid-state lithium metal battery supports the high torque output of motor, which improves the acceleration performance of electric vehicles or ships. The high capacity and excellent cycle performance of solid-state lithium metal battery can significantly extend the driving range and service life of electric vehicles.

The Progress in the Electrolytes for Solid State Sodium‐Ion Battery

AbstractSodium as the closest analogue of lithium in periodic table is attracting intense interest as a potential replacement, in the hope that Na+ offers similar intercalation chemistries in electrode hosts at much lower cost. Sodium‐ion battery is an alternative choice to meet the large‐scale electrical energy storage and also able to be used to store the electricity generated by solar cells and wind turbines as a green, renewable energy source. The use of solid electrolytes to replace the organic electrolyte is an alternative to improve the safety and avoid liquid leakage. The detailed and comprehensive research progress for sodium‐ion battery solid electrolyte is summarized. The recent research reveals that the chemical composition and crystal structure of electrolytes profoundly affects the cell performance in many aspects. The room temperature ionic conductivity for solid polymer electrolytes (SPEs) is generally lower than ≈10−5 S cm−1. Gel polymer electrolyte (GPE) yields acceptable ionic conductivity as the transition between liquid electrolyte and all‐solid electrolyte. There also has groundbreaking progress of inorganic solid electrolyte chemistries exhibiting superionic Na+ conductivities. However, their interphasial chemistries are the emphasis to break through. In the future, exciting breakthroughs in solid electrolytes and interphasial chemistries should be made in those fields.

A novel garnet-type high-entropy oxide as air-stable solid electrolyte for Li-ion batteries

Li-ion batteries are considered prospective candidates for storage systems because of their high energy density and long cycling life. However, the use of organic electrolytes increases the risk of explosion and fire. Hence, all-solid-state Li-ion batteries have attracted considerable attention because the use of solid electrolytes avoids the combustion of electrolytes and explosions, and enhances the performance of batteries. Garnet-type oxides are commonly used solid electrolytes. The common Ta-doped Li7La3Zr2O12 can react easily with CO2 and H2O in air, and its ionic conductivity decays after contact with air. In this study, a novel garnet-type, high-entropy oxide, Li6.4La3Zr0.4Ta0.4Nb0.4Y0.6W0.2O12 (LLZTNYWO), is successfully synthesized as a solid electrolyte for Li-ion batteries,using a conventional solid-state method. Ta, Nb, Y, and W are used as substitutes for Zr, which significantly increase conductivity, have high stability in air, and a lower sintering temperature. LLZTNYWO achieves higher Li-ion conductivity at 1.16 × 10−4 S cm−1 compared to mono-doped Li6.6La3Zr1.6Ta0.4O12 (6.57 × 10−5 S cm−1), Li6.6La3Zr1.6Nb0.4O12 (2.19 × 10−5 S cm−1), and Li6.2La3Zr1.6W0.4O12 (1.16 × 10−4 S cm−1). Additionally, it exhibits higher ionic conductivity compared to equimolar Li5.8La3Zr0.4Ta0.4Nb0.4Y0.4W0.4O12 (1.95 × 10−5 S cm−1). The Li-ion conductivity of LLZTNYWO remains constant for 30 days in the atmosphere without decay, thereby revealing its excellent air stability. Furthermore, LLZTNYWO exhibits a remarkable electrochemical window of up to 6 V vs Li/Li+ and excellent electrochemical stability against Li metal after cycling at 0.1 mA·cm−2 for 2 h, which indicates that it is a promising solid electrolyte for Li-ion batteries.

A room-temperature high performance all-solid-state lithium-sulfur battery enabled by a cross-linked copolymer@ceramic hybrid solid electrolyte

The use of solid electrolytes (SEs) is a key strategy for enabling the intrinsically safe operation of batteries comprising lithium metal anodes as they suppress the growth of lithium dendrites. Among the different types of SEs, polymer-based hybrid electrolytes (HEs) are highly promising due to their synergetic properties from the constituent polymer matrix and inorganic filler particles. However, the lithium-ion diffusion pathway in HEs is still dominated by the polymer, especially for polyethylene oxide (PEO)-based HEs. The main limitation of PEO is the strong temperature dependence of its ionic conductivity, preventing its use at room temperature (RT). Herein, a cross-linked polymer-based HE with a high ionic conductivity of 1.1 × 10-3 S cm-1 at RT is presented. The novel cross-linked copolymer, composed of pentaerythritol tetraacrylate (PETEA), tri(ethylene glycol) divinyl ether (TEG), and lithium bis(trifluoromethanesulfonyl)-imide (LiTFSI), serves as a matrix to achieve satisfactory mechanical strength. Integrated Li7La3Zr2O12 (LLZO) particles are covalently bound to the copolymer by a prior surface modification step. To demonstrate the suitability of the developed HE for RT application in advanced battery systems, a solid-state lithium-sulfur cell is built which exhibits an initial specific capacity of 688 mA h g-1. The ability of this HE to operate at RT can be expected to boost the development of safe all-solid-state batteries for many applications.

A Strategy to Suppress the Electrochemo-Mechanical Degradation in Solvent-Free Electrodes for All-Solid-State Batteries

In response to the safety concerns on highly flammable liquid electrolytes in lithium-ion batteries (LIBs), the all-solid-state batteries (ASSBs) have emerged as promising alternatives for the next generation. The use of solid electrolytes with low flammability can provide resistance to fire/explosion incidents under abnormal conditions. In addition, it is expected that high power and high energy density can be achieved using high-voltage cathode materials due to the wide electrochemical window of solid electrolytes. Therefore, various solid electrolytes (polymer, inorganic, and composite solid electrolytes) were intensively studied.Among the solid electrolytes, sulfide-based inorganic solid electrolytes have attracted much attention due to their advantages. They have the highest ionic conductivity (10-2 ~ 10-3 S cm-1) at room temperature, comparable to a liquid electrolyte. Also, owing to its ductile characteristics, interfacial contact with electrode material is also good, and large-scale production is advantageous. However, there are many problems to be solved to realize ASSB with sulfide-based electrolytes. one of the main obstacles is to produce sheet-type electrodes with high active mass loading and good stability. The slurry process commonly used to manufacture sheet-type electrodes of LIBs cannot be directly applied to ASSBs because sulfide-based electrolytes exhibit high reactivity with most organic solvents. Even if the reactivity is not considered, in the slurry process, the bulk binder surrounds the electrode components and blocks the ion transfer pathway, thereby degrading the cell performance.In this regard, solvent-free processing has emerged as a novel manufacturing process to overcome these issues. It is well known that polytetrafluoroethylene (PTFE) can fibrillate under shear stress conditions. When PTFE is added to the electrode and stress is applied, the PTFE is thinly fibrillated within the electrode. These well-dispersed fibers bind electrode materials and form sheet-type electrode film without delamination. This novel process has little concern about reactivity as no solvent is added, and PTFE does not react with electrode components. Moreover, since the thinly fibrous binder is evenly spread throughout the electrode, a sheet-type electrode can be formed with a smaller amount than in the slurry process, and the ion transfer pathway in the electrode can be less blocked. However, solvent-free processing also has problems to be solved. The thinly fibrillated binder cannot provide sufficient adhesion strength between the electrode components. The insufficient adhesion strength of the binder cannot prevent the reduction in the contact area between the electrode and the electrolyte material due to volume expansion during the charge/discharge process, resulting in rapid performance degradation.In this work, we pre-treated PTFE to increase adhesion strength between electrode components and the cycling stability of the solvent-free electrode. When comparing the mechanical strength of solvent-free electrodes using the Surface and Interfacial Cut Analysis System (SAICAS) tool, electrodes with pre-treated PTFE had higher mechanical strength than electrodes with bare PTFE. Due to the higher mechanical strength, the pre-treated PTFE electrode had better cycling stability than the electrode with bare PTFE. This pre-treatment technology is expected to be a promising technology that can contribute to the realization of large-scale production and commercialization of ASSBs.

Toward Optimization of the Chemical/Electrochemical Compatibility of Halide Solid Electrolytes in All-Solid-State Batteries

All-solid-state batteries (ASSBs) that rely on the use of solid electrolytes (SEs) with high ionic conductivity are the holy grail for future battery technology, since it could enable both greater energy density and safety. However, practical application of ASSBs is still being plagued by difficulties in mastering the SE–electrode interphases. This calls for a wide exploration of electrolyte candidates, among which halide-based Li+ conductors show promise despite being not stable against Li or LixIny negative electrodes, hence the need to assemble cells with a dual SE design. In the work described herein, we studied the electrochemical/chemical compatibility of Li3InCl6 against layered oxide positive electrode (LiNi0.6Mn0.2Co0.2O2, NMC622), carbon additive, and Li6PS5Cl under both cycling and aging conditions. Combining electroanalytical and spectroscopic techniques, we provide evidence for the onset of electrochemically driven parasitic decomposition reactions between Li3InCl6 and NMC622/carbon at lower potentials (3.3 V vs LiIn/In) than theoretically predicted in the literature. Moreover, to combat chemical incompatibility between dual SEs, we propose a new strategy that consists of depositing a nanometer-thick (1 or 2 nm) surface protective layer of Li3PO4 made by atomic layer deposition between Li3InCl6 and Li6PS5Cl. Through this surface engineering process with highly conformal and pinhole-free thin films, halide-based solid-state cells showing spectacular capacity retention over 400 cycles were successfully assembled. Altogether, these findings position halide SEs as serious contenders for the development of ASSBs.

5V Solid-State Lithium Batteries Using Garnet-Based Electrolytes and LiNi0.5Mn1.5O4 Spinel Cathode Composite

There is an ever increasing demand to increase the gravimetric and volumetric energy density of Lithium batteries as well as enhancing their safety cycle life and lower safety. Solid-State batteries (SSB) enjoy a great attention nowadays due to their potential to meet all those requirements and power the EV revolution. The use of solid electrolytes (SE) in commercial batteries has been solely limited to polymer electrolytes based on poly(ethylene oxide), PEO, coupled with LiFePO4 (LFP) that are limited by the oxidative stability of PEO to < 3.6 V and the low potential of LFP at 3.4 V. The commercial cells are cycled at high temperature (45 ⁰C) to overcome the modest ambient ionic conductivity of the SE and under a stack pressure and a cathode composite to overcome the high interfacial resistances of the solid-solid interfaces. A cathode composite is made of conventional cathode components with a "catholyte" added to the formulation. The catholyte is made of an optimized amount of an ionic conductor that is mostly derived from the solid electrolyte formulation. Very recent studies by our research group (1) and others (2) have shown that higher voltage cells can be made by using garnet or perovskite-based ceramic/polymer composites and LiNi0.5Mn0.3Co0.2O2 (NMC532) or LiNi0.6Mn0.2Co0.2O2 (NMC 622) layered cathodes reaching 4.2 V and can operate for few cycles. Herein, we extend the work in order to further increase the voltage of the SSB cells by using LiNi0.5Mn1.5O4 (LNMO) spinel cathode with its high potential of 4.7 V. The Tantalum-doped Lithium Lanthanum Zirconate, Li6.4La3Zr1.4Ta0.6O12 (Ta-doped LLZO, LLZTO), of the garnet family of solid electrolytes has been selected as a SE due to their high ambient ionic conductivity, wide electrochemical stability window and good chemical stability against Li metal. PEO and other compatible polymers have been used to formulate composite SEs in thin films and their properties were studied and compared with LLZTO pellets. Cells have been made using composite cathode formulations composed of LNMO cathode as an active material, carbon black, conventional and novel binders and a SE-based and proprietary catholyte coupled with the SE films or pellets and thick/thin Li films. The short-term cycling performance of the cells assembled with selected SEs and composite cathodes along with other electrochemical results will be presented.

Combining Organic Plastic Salts with a Bicontinuous Electrospun PVDF-HFP/Li7La3Zr2O12 Membrane: LiF-Rich Solid-Electrolyte Interphase Enabling Stable Solid-State Lithium Metal Batteries.

Solid-state electrolytes can guarantee the safe operation of high-energy density lithium metal batteries (LMBs). However, major challenges still persist with LMBs due to the use of solid electrolytes, that is, poor ionic conductivity and poor compatibility at the electrolyte/electrode interface, which reduces the operational stability of solid-state LMBs. Herein, a novel fiber-network-reinforced composite polymer electrolyte (CPE) was designed by combining an organic plastic salt (OPS) with a bicontinuous electrospun polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP)/Li7La3Zr2O12 (LLZO) membrane. The presence of LLZO in the composite helps to promote the dissociation of FSI- from OPSs. Subsequently, the dissociated FSI- is then involved in the formation of a LiF-rich solid electrolyte interphase (SEI) layer on the lithium anode via a reductive decomposition reaction, which was affirmed by theoretical calculations and experimental results. Due to the LiF-rich SEI layer, the Li/Li symmetric cell was able to demonstrate a long cyclic life of over 2600 h at a current density of 0.1 mA cm-2. More importantly, the as-prepared CPE achieved a high ionic conductivity of 2.8 × 10-4 S cm-1 at 25 °C, and the Li/LiFePO4 cell based on the CPE exhibited a high discharge capacity and 83.3% capacity retention after 500 cycles at 1.0 C. Thus, the strategy proposed in this work can inspire the future development of highly conductive solid electrolytes and compatible interface designs toward high-energy density solid-state LMBs.

Theory of soft solid electrolytes: Overall properties of composite electrolytes, effect of deformation and microstructural design for enhanced ionic conductivity

Re-chargeable batteries are an important element in the solution to the future of portable energy storage. In that context, electrolytes play a critical role in the adjudication of a battery’s capacity, efficiency and operation. In most current embodiments of rechargeable batteries, including the widely researched lithium-ion system, electrolytes are liquid. That said, the use of solid electrolytes in lieu of their liquid counterparts is being increasingly explored. Solid electrolytes offer increased stability and improved safety and (specifically polymers) are also ideal candidates in the context of stretchable and flexible electronics. Unfortunately, most solid polymer electrolytes possess ionic conductivity that is orders of magnitude lower than typical liquid electrolytes. In this work, we explore the possibility of microstructure design to enhance the effective ionic conductivity of composite polymer electrolytes. We develop a theoretical framework, grounded in thermodynamics and principles of continuum mechanics, to model the coupled deformation, electrostatics and diffusion in heterogeneous electrolytes. Guided by numerical thought experiments, we establish a homogenization procedure that significantly reduces the complexity of the original non-linear problem and derive general analytical expressions for the effective behavior of electrolytes and closed-form solutions for specific microstructures. Using insights from our model, in addition to proposing suggestions for improving the ionic conductivity of solid electrolytes, we are also able to explain several perplexing experimental observations and address questions such as: (i) Why do some experiments show a dramatic improvement in the ionic conductivity of nanoparticle-impregnated polymers while others yield a decrease? (ii) What is the effect of deformation on ionic conductivity?