Traditional Liquid Electrolytes Research Articles

A novel poly(vinyl carbonate-co-butyl acrylate) quasi-solid-state electrolyte as a strong catcher for lithium polysulfide in Li–S batteries

Lithium-sulfur batteries show great potential in the field of energy storage because of their high-energy density, but the shuttle effect of lithium polysulfide has seriously hindered their practical process. Quasi-solid-state electrolyte (QPE) is considered to be a promising alternative to traditional liquid electrolyte, which can improve the safety and cycling performance of lithium-sulfur batteries. Herein, a novel poly(vinyl carbonate-co-butyl acrylate) QPE with 3D crosslinked network (PEGDA-P(VCA-co-BA)) is designed to capture lithium polysulfide through a chemical adsorption of abundant ester groups. The PEGDA-P(VCA-co-BA) QPE exhibits high ionic conductivity of 2.9 mS cm−1. In order to synergize the beneficial effect of the PEGDA-P(VCA-co-BA) QPE, the nitrogen-doped carbon nanotube film-supported sulfur/Li cells are assembled with the QPE. As-assembled lithium-sulfur batteries show high initial capacity of 1080 mAh g−1 at 0.1 C, long cycle life (capacity retention of 715 mAh g−1 after 500 cycles) and superior rate performance.

Control of Ionic Mobility via Charge Size Asymmetry in Random Ionomers.

Solid polymer electrolytes are considered a promising alternative to traditional liquid electrolytes in energy storage applications because of their good mechanical properties, and excellent thermal and chemical stability. A gap, however, still exists in understanding ion transport mechanisms and improving ion transport in solid polymer electrolytes. Therefore, it is crucial to bridge composition-structure and structure-property relationships. Here, we demonstrate that size asymmetry, λ, represented by the ratio of counterion to charged monomer size, plays a key role both in the nanostructure and in the ionic dynamics. More specifically, when the nanostructure is modified by an external electric field such that the mobility cannot be described by linear response theory, two situations arise. The ionic mobility increases as λ decreases (small counterions) in the weak electrostatics (high dielectric constant) regime, whereas in systems with strong electrostatic interactions, ionomers with higher size symmetry (λ ≈ 1) display higher ionic mobility. Moreover, ion transport is found to be dominated by the hopping of the ions and not by moving ionic clusters (also known as "vehicular" charge transport). These results serve as a guide for designing ion-containing polymers for ion transport related applications.

A Flexible Dual‐Ion Battery Based on Sodium‐Ion Quasi‐Solid‐State Electrolyte with Long Cycling Life

AbstractSodium‐based dual‐ion batteries (SDIBs) have attracted much attention for their advantages of high operating voltage, environmental friendliness, and especially low cost. However, the electrochemical performances of the reported SDIBs are still unsatisfied due to the decomposition problem of traditional liquid electrolyte under high working voltage. Development of quasi‐solid‐state electrolytes (QSSEs) with excellent electrochemical stability at high voltage is a possible means to improve their properties. In this work, a flexible SDIB based on a QSSE, consisting of poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP) three‐dimensionally cross‐linked with Al2O3 nanoparticles, which exhibits a porous 3D structure with dramatically enhanced ionic conductivity up to ≈1.3 × 10−3 S cm−1, facilitating fast ionic migration of both anions and cations, is reported. This quasi‐state SDIB exhibits a high specific capacity of 96.8 mAh g−1 at a current rate of 5 C and excellent cycling stability with a capacity retention of 97.5% after 600 cycles at 5 C, which is the best performance of the SDIBs. Moreover, excellent flexibility and a wide working temperature range (−20 to 70 °C) have been realized for this battery, suggesting its potential for high‐performance flexible energy storage applications.

Predicting Polymer Flammability Using Machine Learning Methods

Solid state batteries are a promising replacement for traditional liquid electrolyte batteries due to their superior stability and inflammability. Conventional lithium ion batteries use an organic liquid electrolyte, which is a potential hazard when it undergoes a decomposition reaction leading to an explosion. A solid, non- flammable electrolyte is a promising alternative. However, the chemical space of polymers is diverse and identifying new materials for electrolytes requires a critical screening criterion. Polymer flammability can be quantified using the limiting oxygen index (LOI), which is the minimum oxygen concentration necessary to sustain stable combustion. Polymers with an LOI greater than 21 are inflammable at room temperature and can be deemed safe for use in a battery. In this work, we predict the LOI for new polymers using a combination of data driven and machine learning methods. We have carefully curated a dataset of polymers and their associated LOI values, which are experimentally determined. A fingerprinting scheme is used to numerically represent the polymers from an atomistic to morphological length scale. We then use a gaussian progress regression model to map the polymers from their fingerprint space to their LOI. This model can then be used to rapidly predict the LOI of a polymer and its associated uncertainties. This study could rationally guide the design of solid polymer electrolytes which are thermally stable and inflammable.

Systematic Electrochemical Characterizations of Low Molecular Weight Gelator-Based Quasi-Solid Electrolytes

An electrolyte is one of the essential components in diverse electrochemical devices including lithium secondary batteries and dye-sensitized solar cells (DSSCs). Traditional liquid electrolytes having a high ion conductivity suffer from a problem of lowering the durability of the electrochemical devices because they have high flowability and volatility. Therefore, to improve the reliability of the electrochemical devices, it is preferable to replace the liquid electrolyte with a quasi-solid electrolyte. However, quasi-solid electrolytes are usually difficult to inject the devices and have a lower ion conductivity due to a higher viscosity than liquid electrolyte. In this study, we have developed a quasi-solid electrolyte which is based on a low molecular weight gelator (LMWG) with high conductivity and stability through proper physical crosslinking. In addition, the combination of various polymer materials including special functional groups with LMWG has been investigated for the optimization of the electrolyte performances. Especially, the prepared quasi-solid electrolytes have been systematically analyzed by various electrochemical methods and applied to both lithium battery and DSSC for evaluating their performances. The detailed results will be presented and discussed at the conference. This work was supported by a grant (No.2017000140002/ RE201702218) from the Environmental Industry Advancement Technology Development Project of Korea Environmental Industry & Technology funded by Korea Ministry of Environment.

Interface effects on self-forming rechargeable Li/I2-based solid state batteries

Abstract

A Microporous Gel Polymer Electrolyte for Sodium Batteries

Room-temperature sodium batteries have the potential to meet the growing worldwide demand for electrical energy storage, thanks to the widespread availability and low cost of sodium. Compared with traditional liquid electrolytes, gel polymer electrolytes (GPEs) offer higher safety and adaptability to be designed as flexible energy storage devices without sacrifice of conductivity. In this work, we have successfully synthesized furan-based hypercrosslinked microporous polymers (Fu-HCPs) by using a solvothermal method. The prepared Fu-HCPs demonstrate a high surface area ≈ 500 m2 g‒1 with a pore-size distribution of 5−15 Å. A novel porous membrane consisting of a double polymer network of microporous Fu-HCPs and macroporous poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) is fabricated via a phase-inversion technique. The corresponding polymer electrolyte is prepared by immersing the porous membrane into a sodium liquid electrolyte. The macroporous and microporous nature of the prepared polymer membrane allows for an electrolyte uptake up to 200 wt. %. The polymer electrolyte saturated with sodium liquid electrolyte exhibits high conductivities (e.g., > 10‒3 S cm−1 at 25 °C) with great electrochemical (up to 4.2 V vs Na) and mechanical stability. If the microporous polymer electrolyte is applied in a full-cell sodium-ion battery with metallic sodium as an anode and Na3V2(PO4)3 as a cathode, the cycling performance and coulombic efficiency are significantly improved relative to the cell with liquid electrolyte. The results suggest that the microporous/macroporous furan-based polymer host with immobilized-liquid electrolyte inhibit sodium dendrite growth and allow the use of a metallic sodium anode for large-scale applications.

From Ionic Liquid Fragments Towards Hybrid Nanoparticles for Solid-State Lithium Ion Technology

Secondary batteries capable of efficiently storing and delivering a large amount of electrical energy are essential elements to sustain the constantly increasing development of nomad and mobility technologies. Among the different energy storage systems, the most energetic storage systems which have flood the market are ions batteries (mainly lithium), however they suffer of one major drawback owing to overloads or short-circuits which may cause thermal runaway owing to the combustion of the liquid electrolyte. To make them safer both in use and after disposal, one possibility is to replace traditional liquid electrolyte by solid state electrolytes in the next generations of ion batteries [1]. All-solid-state batteries are capable to have longer life cycle, higher energy density and less requirements on packaging. One of key components that determines performance is solid electrolyte. In the past years many types have been investigated among which figures the types NASICON, perovskite, Argyrodite, anti-perovskite, garnet, LISICON, Li3N, sulfide and many more [2]. Nevertheless, an insufficient room-temperature ionic conductivity (10-5-10-3 σ.cm-1), lithium transport number, and poor electrode-electrolyte interface hinder the reality of these devices [3]. One other promising possibility is to use immobilized or grafted ionic liquids onto the surface of a nanometric material to ensure ion mobility [4]. These new types of hybrid materials, still modestly developed, offer mechanical strength comparable to that of solid polymer electrolytes and have been reported, by our group, to display lithium ion conductivity approaching the standards of liquid electrolytes [5]. Here we present the design of new organic/inorganic hybrid electrolytes based on nanometric zirconium and silicon dioxide and ionic liquid for ion conduction. Immobilization of the ionic liquid was realized using suitable function groups (carboxylic acid or organosilane) which formed with surface atoms a stable interaction. These new materials were carefully characterized by different techniques like FT-IR, TEM, TGA and N2-adsorption to ensure incorporation of the ionic liquid to prove the grafting and estimate the organic content of the synthesized hybrid materials. Additionally, ionic conductivity was measured by Electrochemical Impedance Spectroscopy using a specific new method specifically developed for this type of material and was completed with the determination of the electrochemical stability using cyclic voltammetry. Several parameters like material texture (particle diameter, porosity, shape…), anchoring type, molecular structure of ionic liquid fragments and surface density of the grafting were tuned to maximize ion mobility and so the conductivity. First trends linking hybrid materials structure/composition and ionic conductivity will be presented. [1] Fan, L. et al., Adv. Energy Mater., 2018, 8, 1702657. [2] Takada, K. Acta Mater., 2013, 61, 759–770. [3] Sun, C. et al., Nano Energy, 2017, 33, 363–386. [4] Lu, Y. et al., Adv. Mater., 2012, 24, 4430–4435. [5] Delacroix, S. et al., Chem. Mater., 2015, 27, 7926–7933. Fig 1. New organic/inorganic hybrid electrolytes based ionic liquids Figure 1

In Situ Generated Li2S-C Nanocomposite for High-Capacity and Long-Life All-Solid-State Lithium Sulfur Batteries with Ultrahigh Areal Mass Loading.

All-solid-state lithium-sulfur batteries (ASSLSBs) have attracted great attention due to their inherent ability to eliminate the two critical issues (polysulfide shuttle effect and safety) of traditional liquid electrolyte based Li-S batteries. However, it remains a huge challenge for ASSLSBs to achieve high areal active mass loading and high active material utilization simultaneously due to the insulating nature of sulfur and Li2S, and the large volume change during cycling. Herein, a Li2S@C nanocomposite with Li2S nanocrystals uniformly embedded in conductive carbon matrix, is in situ generated by the combustion of lithium metal with CS2. Benefiting from its unique architecture, the Li2S@C exhibits exceptional electrochemical performance as cathode for ASSLSBs, with both ultrahigh areal Li2S loading (7 mg cm-2) and 91% of Li2S utilization (corresponding to a reversible capacity of 1067 mAh g-1). Moreover, the Li2S@C also possesses outstanding rate capability and cycling stability. High reversible capacity of 644 mAh g-1 is delivered at 2 mA cm-2 even after 700 cycles. This work demonstrates that ASSLSBs with superior electrochemical performance can be realized via rational design of the cathode structure, which provides a promising prospect to the development of ASSLSBs with practical energy density surpassing that of lithium ion batteries.

Stable Conversion Chemistry‐Based Lithium Metal Batteries Enabled by Hierarchical Multifunctional Polymer Electrolytes with Near‐Single Ion Conduction

AbstractThe low Coulombic efficiency and serious safety issues resulting from uncontrollable dendrite growth have severely impeded the practical applications of lithium (Li) metal anodes. Herein we report a stable quasi‐solid‐state Li metal battery by employing a hierarchical multifunctional polymer electrolyte (HMPE). This hybrid electrolyte was fabricated via in situ copolymerizing lithium 1‐[3‐(methacryloyloxy)propylsulfonyl]‐1‐(trifluoromethanesulfonyl)imide (LiMTFSI) and pentaerythritol tetraacrylate (PETEA) monomers in traditional liquid electrolyte, which is absorbed in a poly(3,3‐dimethylacrylic acid lithium) (PDAALi)‐coated glass fiber membrane. The well‐designed HMPE simultaneously exhibits high ionic conductivity (2.24×10−3 S cm−1 at 25 °C), near‐single ion conducting behavior (Li ion transference number of 0.75), good mechanical strength and remarkable suppression for Li dendrite growth. More intriguingly, the cation permselective HMPE efficiently prevents the migration of negatively charged iodine (I) species, which provides the as‐developed Li‐I batteries with high capacity and long cycling stability.

Molecular Dynamics Simulations of Ion Transport in Poly-Ethylene Oxide

Solid polymers are becoming a promising alternative option as an electrolyte material in lithium ion batteries [1,2,3]. Solid polymer electrolytes have certain advantages over traditional electrolytes – non-flammability, good electrochemical and mechanical stability, and ability to hinder the growth of dendrites at electrode surfaces [4,5]. Poly-ethylene oxide (PEO) is one such polymer which has been considered a viable option due to its ability to solvate lithium ions and its relatively high ion conductivities. However, the bulk Li-ion conductivities even in PEO at room temperature are at least an order of magnitude less than the traditional liquid electrolytes [2,6]. In this study, we explore the influence of ion concentration and pressure on the Li-ion transport mechanism and in turn on its conductivity in PEO by performing molecular dynamics (MD) simulations of a lithium salt (lithium bis(trifluoromethane) sulfonamide (LiTFSI)) in polymer matrix of poly-ethylene oxide (PEO). We explored the influence of pressure to examine if it has any role in increasing the performance of PEO as an electrolyte. We computed parameters like diffusivity, conductivity and transference numbers that are crucial in determining the performance of PEO as a potential electrolyte for lithium ion batteries. We observe that diffusivity and conductivity decrease with increase in pressure while transference number remain almost independent. The simulation framework can be further used to explore polymers other than PEO as an electrolyte material or to test different block copolymers based on PEO. [1] F. M. Gray. Solid polymer electrolytes: fundamentals and technological applications (pp. 83-93). New York: VCH (1991). [2] D. T. Hallinan Jr., & N. P. Balsara. Polymer electrolytes. Annual review of materials research, 43, 503-525 (2013). [3] S. Mogurampelly, O. Borodin, & V. Ganesan. Computer simulations of ion transport in polymer electrolyte membranes. Annual review of chemical and biomolecular engineering, 7, 349-371 (2016). [4] F. M. Gray. Polymer electrolytes. Royal Society of Chemistry (1997). [5] K. J. Harry, D. T. Hallinan, D. Y. Parkinson, A. A. MacDowell, & N. P. Balsara. Detection of subsurface structures underneath dendrites formed on cycled lithium metal electrodes. Nature materials, 13(1), 69.4 (2014). [6] A. A. Teran, M. H. Tang, S. A. Mullin, & N. P. Balsara. Effect of molecular weight on conductivity of polymer electrolytes. Solid State Ionics, 203(1), 18-21 (2011). Figure 1

Alternative Polymers for Alternative Energy Storage Solutions: Solid Polycarbonate- and Polyester-Based Na-Ion Battery Electrolytes

As the production of current-generation energy storage technologies is being scaled up for widescale implementation in electric vehicle and large-scale grid storage, cost and sustainability are becoming more limiting factors for battery utilization than the capacity, which is already sufficient for many applications. Here, the future supply of Li has been pointed out as potentially problematic, [1] with in particular Na, with its similar size, reduction potential and chemistry, but with far greater abundancy and wider global distribution, highlighted as a natural candidate for more sustainable “beyond-Li” energy storage [2]. The notable similarities between Li and Na translate into similarities in the battery chemistries such that the research on Li-ion batteries can be used as a starting point for the development of Na-ion batteries. Unfortunately, these similarities also mean that the combination of high energy densities, high voltages and flammable organic electrolyte solvents that is cause for major safety concerns in Li-ion batteries [3] is also deeply concerning for Na-ion batteries. This can be mitigated by using solid polymer electrolytes, with negligible vapor pressure and inherent mechanical stability, in place of the traditional liquid electrolytes to improve battery safety and stability. These electrolytes are traditionally based on polyethers, in particular poly(ethylene oxide) (PEO) as the ion-solvating and -transporting host material. Unfortunately, for both Li and Na, this material shows poor ionic conductivity at room temperature because of crystallization, in combination with low cation transference numbers [4], requiring elevated temperatures in order to sustain cell cycling. There are, however, a large range of potential host materials that extends beyond the polyether paradigm and that has been surveyed for Li-based energy storage [5] but has yet to be implemented for Na-ion batteries. We have focused on materials that can coordinate to Na+ by means of carbonyl groups. Using the host material poly(trimethylene carbonate) in combination with NaTFSI, fully amorphous electrolytes were obtained that could sustain Na+ transport in Na metal cells at 60 °C [6]. Improved stability was seen with NaFSI salt, where also notably high ionic conductivities were attained at high salt concentrations, but at reduced cycling stability. Instead, at moderate salt concentrations, stable cycling over >80 cycles was seen. Finally, using a polyester–polycarbonate copolymer host material, ionic conductivities on the order of 10− 5 S cm− 1 were attained in combination with a cation transference number close to 0.5, allowing for room-temperature cycling of solid-state Na-ion full cells. Tarascon, J.-M. Chem. 2010, 2, 510-510Deng, J. et al. Energy Mater. 2018, 8, 1701428Robinson, A. L. et al. MRS Bull. 2016, 41, 188-189Qi, X. et al. ChemElectroChem 2016, 3, 1741–1745Mindemark, J. et al. Polym. Sci. 2018, 81, 114–143Mindemark, J. et al. Electrochem. Commun. 2017, 77, 58-61

Upgrading traditional liquid electrolyte via in situ gelation for future lithium metal batteries.

High-energy lithium metal batteries (LMBs) are expected to play important roles in the next-generation energy storage systems. However, the uncontrolled Li dendrite growth in liquid electrolytes still impedes LMBs from authentic commercialization. Upgrading the traditional electrolyte system from liquid to solid and quasi-solid has therefore become a key issue for prospective LMBs. From this premise, it is particularly urgent to exploit facile strategies to accomplish this goal. We report that commercialized liquid electrolyte can be easily converted into a novel quasi-solid gel polymer electrolyte (GPE) via a simple and efficient in situ gelation strategy, which, in essence, is to use LiPF6 to induce the cationic polymerization of the ether-based 1,3-dioxolane and 1,2-dimethoxyethane liquid electrolyte under ambient temperature. The newly developed GPE exhibits elevated protective effects on Li anodes and has universality for diversified cathodes including but not restricted to sulfur, olivine-type LiFePO4, and layered LiNi0.6Co0.2Mn0.2O2, revealing tremendous potential in promoting the large-scale application of future LMBs.

Prompting Mass Transfer in Solid-State Solar Cells Using Submicron Spherical Mesoporous Titanium Oxide Aggregates

Dye-sensitized solar cells (DSCs) combines benefits of low-cost, simple fabrication and competitive solar energy conversion efficiency. Recent success in the replacement of traditional iodide/tri-iodide redox mediators by noncorrosive, less light absorption cobalt (II/III) polypyridyl complexes has led to encouraging solar energy conversion efficiencies in excess of 13%, well beyond that of iodide/tri-iodide based electrolytes (ca.11%). Solvent evaporation in traditional liquid electrolyte challenges durable encapsulation of DSCs. This has driven increasing focus on alternative semi-solid-state electrolytes for practical DSC applications. Gel electrolytes have exhibited an impressive long-term stability, especially for outdoor applications where temperature of the DSC system can reach 80-85 oC under sunlight. In a solid-state gel electrolyte, the mass transport of cobalt (II/III) complexes is greatly retarded by the highly viscous gelatinous environment, which limits the dye regeneration and thus the overall efficiency of the SS-DSCs. To date, there are still very limited reports of this new type of SS-DSCs, leaving great scope for further development. Sophisticated architectural designs that leverage macro-porosity to promote ionic diffusion and meso-porosity to increase specific surface area for dye loading may also provide a viable solution to tackle the current limit in cobalt gel electrolyte based SS-DSCs, leading to a higher efficiency [1]. In this work, we establish that a simple replacement of photoanode building-blocks from standard commercial TiO2 nanoparticles (CCIC and P25) to titania nanorod aggregates (TNA) enabled remarkable improvement on ionic diffusion of cobalt (II/III) tris(2′2-bipyridine) complexes in a gel electrolyte. An overall solar energy conversion efficiency of over 7.1% and 8.0% was reached by freshly constructed and stabilized SS-DSCs using the TNA, respectively. Those correspond to efficiency enhancements up to 35% and 100% against that of the standard TiO2 nanoparticles – P25 (4.0%) and CCIC (5.9%), respectively.

Preparation and characterization of PAN-LATP composite solid-state electrolyte

Compared with the traditional liquid electrolyte, the solid polymer electrolyte can significantly improve the safety and energy density of the lithium secondary batteries, but its room temperature lithium ion conductivity is low and the mechanical properties are relatively poor. These problems limit the application of solid polymer electrolytes in lithium secondary batteries. In order to solve the above problems, PAN-LATP composite solid electrolyte (CSE) was prepared by solution casting method in polyacrylonitrile (PAN) polymer electrolyte to introduce inorganic solid-state electric Li1.3Al0.3Ti1.7(PO4)3 (LATP). The composite solid electrolyte not only has higher lithium ion conductivity, but also broadens the electrochemical stability window of the solid polymer electrolyte. When the LATP content was 15%, the CSE has the highest lithium ion conductivity, which was 2.14×10−5 S/cm at room temperature and 3.03×10−4 S/cm at 333 K. At the same time, the mechanical strength of the solid polymer electrolyte has also been improved. The results show that the solid electrolyte with good performance is expected to be used in lithium-ion batteries and other electrochemical energy storage systems.

A Dual-Salt Gel Polymer Electrolyte with 3D Cross-Linked Polymer Network for Dendrite-Free Lithium Metal Batteries.

Lithium metal batteries show great potential in energy storage because of their high energy density. Nevertheless, building a stable solid electrolyte interphase (SEI) and restraining the dendrite growth are difficult to realize with traditional liquid electrolytes. Solid and gel electrolytes are considered promising candidates to restrain the dendrites growth, while they are still limited by low ionic conductivity and incompatible interphases. Herein, a dual‐salt (LiTFSI‐LiPF6) gel polymer electrolyte (GPE) with 3D cross‐linked polymer network is designed to address these issues. By introducing a dual salt in 3D structure fabricated using an in situ polymerization method, the 3D‐GPE exhibits a high ionic conductivity (0.56 mS cm−1 at room temperature) and builds a robust and conductive SEI on the lithium metal surface. Consequently, the Li metal batteries using 3D‐GPE can markedly reduce the dendrite growth and achieve 87.93% capacity retention after cycling for 300 cycles. This work demonstrates a promising method to design electrolytes for lithium metal batteries.

Hybrid electrolytes incorporated with dandelion-like silane–Al2O3 nanoparticles for high-safety high-voltage lithium ion batteries

One of the crucial challenge for developing high safety and high voltage lithium ion batteries is to find a reliable electrolyte system. In this work, we report a kind of hybrid electrolytes, which are used for high-voltage lithium ion batteries and are expected to be able to effectively enhance the battery safety. The hybrid electrolytes are obtained by incorporating silane-Al2O3 (Al2O3-ST) into liquid electrolyte, which combines the merits of both solid electrolyte and liquid electrolyte. The Al2O3-ST nanoparticles help to increase lithium-ion transference number and to enhance battery safety, while liquid electrolyte contributes to high ionic conductivity. The cycling stability and rate capacity of LiNi0.5Mn1.5O4/Li batteries are improved by using the hybrid electrolytes. Nail-penetration tests indicate that LiNi0.6Mn0.2Co0.2O2/graphite battery with hybrid electrolyte owns obviously enhanced safety than that using traditional liquid electrolyte. This work provides new insight on electrolyte design for high-safety high-voltage lithium ion batteries.

Toward All-Solid-State Lithium Batteries: Three-Dimensional Visualization of Lithium Migration in β-Li3PS4 Ceramic Electrolyte

All-solid lithium batteries are an attractive next-generation technology that use ion-conducting solids such as β-Li3PS4 (LPS) to enable use of a lithium metal anode, which increases theoretical capacity and widens the stable voltage window over traditional lithium-ion systems. These ion-conductive solids also provide increased safety by replacing flammable liquid electrolytes. Although solid-state electrolytes are significantly more stable and dendrite-resistant than traditional liquid electrolytes, lithium anodes in all-solid systems may nevertheless grow dendrites under high stress or repeated cycling, leading to short circuits and premature battery breakdown. For this reason, we study the formation and propagation of Li metal features within solid electrolytes using synchrotron-based X-ray tomography with in-situ current-voltage cycling supported by our custom sample platform. Our results demonstrate the ability of this technique to delineate different layers of the Li/LPS/Li structure with spatial resolution approaching 1 μm. At this resolution, we are able to detect expansion of voids, especially in early stages of cycling. This expansion of voids is observed throughout the volume of the symmetric cells and visually resembles propagation of cracks resulting from interactions between the Li metal and pre-existing voids in the LPS electrolyte.

Gel Polymer Electrolytes for Electrochemical Energy Storage

AbstractWith the booming development of flexible and wearable electronics, their safety issues and operation stabilities have attracted worldwide attentions. Compared with traditional liquid electrolytes, gel polymer electrolytes (GPEs) are preferred due to their higher safety and adaptability to the design of flexible energy storage devices. This review summarizes the recent progress of GPEs with enhanced physicochemical properties and specified functionalities for the application in electrochemical energy storage. Functional GPEs that are capable to achieve unity lithium‐ion transference number and offer additional pseudocapacitance to the overall capacitance are carefully discussed. The smart GPEs with self‐protection, thermotolerant, and self‐healing abilities are particularly highlighted. To close, the future directions and remaining challenges of the GPEs for application in electrochemical energy storages are summarized to provide clues for the following development.

Promising Routes to a High Li+ Transference Number Electrolyte for Lithium Ion Batteries

The continued search for routes to improve the power and energy density of lithium ion batteries for electric vehicles and consumer electronics has resulted in significant innovation in all cell components, particularly in electrode materials design. In this Review, we highlight an often less noted route to improving energy density: increasing the Li+ transference number of the electrolyte. Turning to Newman’s original lithium ion battery models, we demonstrate that electrolytes with modestly higher Li+ transference numbers compared to traditional carbonate-based liquid electrolytes would allow higher power densities and enable faster charging (e.g., >2C), even if their conductivity was substantially lower than that of conventional electrolytes. Most current research in high transference number electrolytes (HTNEs) focuses on ceramic electrolytes, polymer electrolytes, and ionomer membranes filled with nonaqueous solvents. We highlight a number of the challenges limiting current HTNE systems and suggest a...