Solid Liquid Electrolytes Research Articles

Low‐temperature performance of Na‐ion batteries

AbstractSodium‐ion batteries (NIBs) have become an ideal alternative to lithium‐ion batteries in the field of electrochemical energy storage due to their abundant raw materials and cost‐effectiveness. With the progress of human society, the requirements for energy storage systems in extreme environments, such as deep‐sea exploration, aerospace missions, and tunnel operations, have become more stringent. The comprehensive performance of NIBs at low temperatures (LTs) has also become an important consideration. Under LT conditions, challenges such as increased viscosity of electrolyte, abnormal growth of solid electrolyte interface, and poor contact between collector and electrode materials emerge. The aforementioned issues hinder the diffusion kinetics of sodium ions (Na+) at the electrode/electrolyte interface and cause rapid degradation of battery performance. Consequently, the optimization of electrolyte composition and cathode/anode materials becomes an effective approach to improve LT performance. This review discusses the conduction behavior and limiting factors of Na+ in both solid electrodes and liquid electrolytes at LT. Furthermore, it systematically reviews the recent research progress of LT NIBs from three aspects: cathode materials, anode materials, and electrolyte components. This review aims to provide a valuable reference for developing high‐performance LT NIBs.

Development of a Fast in Situ Scanning Tunneling Microscope for Studies of Electrocatalyst Surfaces

The atomic-scale understanding of processes at the interface between solid electrodes and liquid electrolytes is of high importance for electrochemical energy storage and conversion. Electrochemical scanning tunneling microscopy (ECSTM) is a key technique for the investigation of these interfaces and as such, it has seen widespread use. However, the image acquisition in a conventional ECSTM is a rather slow process, requiring tens of seconds or minutes per image. To help understand the precise reaction mechanisms of atomic and molecular species at solid-liquid interfaces, their movement and interactions need to be resolved. For this, much higher imaging rates are necessary. High-speed STMs (video STMs) are capable of operating at rates >10 images per second, which is sufficiently fast to observe and quantitatively study a wide range of surface dynamic processes, e.g., surface diffusion and growth [1]. However, this technique has not been widely employed, mainly because of the instrumental requirements.The development of an STM for fast in situ measurements poses a set of challenges, which require a carefully planned implementation. For operation in electrochemical environment, the potentials of both STM tip and sample need to be controlled and electrochemical currents at the tip need to be kept way below the tunneling current. Fast image acquisition requires a scanner with high mechanical stability to avoid the excitation of uncontrolled tip oscillations at its resonance frequencies. Additionally, high-bandwidth measurement and control electronics and a sophisticated control software with fast scan generation and data processing capabilities are essential. No commercial system that is capable of fulfilling these requirements exists up to now. For this reason, all existing video-rate STM studies have been performed with home-built setups that employ highly specialized hardware that is not easy to reproduce.In this contribution, we present a new ECSTM developed and built in our group. The setup is based on a Nanonis SPM controller by SPECS and a custom scanner, bipotentiostat, and coarse approach control that were integrated into this system. We show example data and images to demonstrate the performance of the STM. Furthermore, we reveal the modifications employed to make it capable of video-rate imaging. These include a novel scanner design with two independent piezo stacks for slow and high-speed movements and a custom high-bandwidth preamplifier integrated into the scan head as close as possible to the tip. Fast data acquisition is realized by an FPGA-based control software, which features a user-friendly frontend and a backend with good performance even at high image acquisition rates. This software is designed to run alongside the commercial control software for the slow STM operation so that switching between the slow and fast imaging modes is as frictionless as possible. We will show preliminary test results of the early implementation of the fast imaging mode.[1] O. M. Magnussen, Chem. Eur. J. 2019, 25, 12865.

Hybrid Material Concepts for Thiophosphate-Based Solid-State Batteries

Solid-state batteries (SSBs) could replace conventional lithium-ion batteries due to the possibility of increasing the energy density of the cells by using lithium metal as the anode material.[1] Among the many electrolyte candidates for lithium SSBs, the lithium thiophosphates are particularly interesting due to their high ionic conductivities at room temperature (>1 mS/cm). However, the (electro)chemical stability of these solid electrolytes is limited and not fully compatible with state-of-the-art high-potential cathode active materials[2] or the lithium metal anode.[3] At the cell level, the formation of interparticle voids between the various battery components (solid electrolyte, cathode active material, anode material, additives, decomposition interphases) hinder the net transport during cycling. To address the latter electro-chemo-mechanical challenges, we are exploring hybrid material approaches, in which we combine established materials (solid electrolytes, liquid electrolytes and/or polymer additives) with state-of-the-art cathode active materials and test their electrochemical performance in solid-state battery (half-)cells. Such cycling results are complimented by detailed electrochemical transport studies in symmetrical cells using DC polarization and electrochemical impedance spectroscopy, including transmission-line modeling. ex.situ chemically-specific spectroscopic methods are used to support our hypotheses and interpretation of the electrochemical results. Taken together, we attain a better picture on the positive (or negative) role hybrid materials play in SSBs. In this talk, we will showcase two hybrid systems, namely ionic liquid/thiophosphate lithium hybrid electrolytes and conductive polymers additives in NMC-based catholyte composites for Li6PS5Cl cells. The first part of the talk we will discuss the results in which we evaluate the performance of liquid electrolyte-solid electrolyte materials against lithium metal using galvanostatic electrochemical impedance spectroscopy. In the second part, we elucidate the partial ionic and electronic transport in polymer electrolyte-Li6PS5Cl-NMC catholytes as a function of polymer content using impedance spectroscopy and its effect in the cycling performance, both the stability as well as the magnitude of the discharge capacities. These systems serve as a good starting point for the further development and incorporation of hybrid materials in SSBs.Literature: [1] W. G. Zeier and J. Janek Nature Energy, 2016, 1, 16141. [2] G.F. Dewald, S. Ohno, M.A. Kraft, R. Kroever, P. Till, N.M. Vargas-Barbosa, J. Janek, W.G. Zeier Chem. Mater. 2019, 31, 8328. [3] L. M. Riegger, R. Schlem, J. Sann, W. G. Zeier, J. Janek, Angew. Chem. Int Ed 2021, 60, 6718. Figure 1

Oxide‐Based Pseudo‐Solid‐State Hybrid Electrolyte Functionalized by Ionic Liquid for Lithium Metal Batteries

Solid‐state batteries draw attention as next‐generation batteries that can provide higher energy density and overall stability based on the inherent nonflammability of the solid electrolytes. However, solid electrolytes have a clear limitation of low ionic conductivity due to their high resistance at grain boundaries and interfaces. Herein, oxide‐type solid electrolytes and ionic liquid electrolytes are introduced to reduce the overall resistance and form a clay‐textured composite electrolyte after a hybrid process. This composite electrolyte exhibits a stable state without side reactions and 1.6 ms cm−1 of improved ionic conductivity. This material also demonstrates its high thermal and electrochemical stability by high‐temperature exposure test and the application of bipolar configuration in conventional coin cells with high voltage. Therefore, this original clay‐textured pseudo‐solid‐state hybrid electrolyte is believed to contribute to the studies related to oxide‐type solid electrolytes for advanced solid‐state batteries.

Hybrid solid electrolyte-liquid electrolyte systems for (almost) solid-state batteries: Why, how, and where to?

Combining solid electrolytes (SE) and liquid electrolytes (LE) may resolve interparticle contact issues in solid-state batteries. New challenges arise due SLEI, which needs to be better understood to minimize its effects at the cell-level.

Research Status and Optimization Methods of Zinc Ion Battery

Up against the energy shortage and aggravating environmental pollution, it is extremely urgent to develop renewable clean energy. With efficient energy storage and energy conversion, electrochemical energy storage is the key direction for the development of energy storage technology in the future. Besides, aqueous zinc ion battery has attracted researchers because of its low cost and high theoretical specific capacity. Cathode materials for aqueous zinc ion batteries are roughly divided into manganese-based compounds, vanadium-based compounds, Prussian blue analogues, etc, which usually use zinc metal as an anode. Electrolytes include solid hydrogel electrolytes and liquid ion electrolytes. However, some problems exist in cathode materials, such as elements dissolution and low discharge voltage, while anode materials have problems in zinc dendrite growth and side reactions, and water decomposition occurs in electrolytes. In recent years, researchers have devoted themselves to optimizing aqueous zinc ion batteries in different ways, so as to obtain their high performance. In this paper, the general situation of zinc ion battery is introduced at first, and then the research status is emphatically expounded from the perspectives of problems existing in cathode materials, anode materials, electrolyte, and their optimization methods, which provides references for developing high-performance aqueous zinc ion battery.

Ion Hopping: Design Principles for Strategies to Improve Ionic Conductivity for Inorganic Solid Electrolytes.

Solid electrolytes are considered as an ideal substitution of liquid electrolytes, avoiding the potential hazards of volatilization, flammability, and explosion for liquid electrolyte-based rechargeable batteries. However, there are significant performance gaps to be bridged between solid electrolytes and liquid electrolytes; one with a particular importance is the ionic conductivity which is highly dependent on the material types and structures. In this review, the general physical image of ion hopping in the crystalline structure is revisited, by highlighting two main kernels that impact ion migration: ion hopping pathways and skeletons interaction. The universal strategies to effectively improve ionic conductivity of inorganic solid electrolytes are then systematically summarized: constructing rapid diffusion pathways for mobile ions; and reducing resistance of the surrounding potential field. The scoped strategies offer an exclusive view on the working principle of ion movement regardless of the ion species, thus providing a comprehensive guidance for the future exploitation of solid electrolytes.

Anomalous interfacial dynamics of single proton charges in binary aqueous solutions.

Our understanding of the dynamics of charge transfer between solid surfaces and liquid electrolytes has been hampered by the difficulties in obtaining interface, charge, and solvent-specific information at both high spatial and temporal resolution. Here, we measure at the single charge scale the dynamics of protons at the interface between an hBN crystal and binary mixtures of water and organic amphiphilic solvents (alcohols and acetone), evidencing a marked influence of solvation on interfacial dynamics. Applying single-molecule localization microscopy to emissive crystal defects, we observe correlated activation between adjacent ionizable surface defects, mediated by the transport of single excess protons along the solid/liquid interface. Solvent content has a nontrivial effect on interfacial dynamics, leading at intermediate water fraction to an increased surface diffusivity, as well as an increased affinity of the proton charges to the solid surface. Our measurements evidence the notable role of solvation on interfacial proton charge transport.

Improving Cell Resistance and Cycle Life with Solvate/Thiophosphate Hybrid Electrolytes in Lithium Metal and Lithium Sulfur Batteries

Solid electrolytes (SEs) have become a practical option for lithium ion and lithium metal batteries due to their improved safety over commercially available ionic liquids. The most promising of the SEs are the thiophosphates whose excellent ionic conductivities at room temperature are comparable to those of the commercially-utilized ionic liquids. Hybrid solid-liquid electrolytes exhibit higher ionic conductivities than their bare solid electrolyte counterparts due to decreased grain boundary resistance, enhanced interfacial contact with electrodes, and decreased degradation at the interface.In this study, we evaluate a series of hybrid electrolytes made from a ‘solvate’ electrolyte in both Li-Li symmetric cells and in a full cell with a Li2S cathode relative to their bare Li/SE/Li counterparts. Interestingly, hybrid electrolytes made by combining HFE-modified solvates and SE exhibit all the benefits of the interlayer modified SEs, without the necessity of pellet manufacture. The solvate-integrated cathode layer is additionally beneficial for achieving high active material utilization, maintaining intimate interfacial contact, and providing buffer space for volume contraction and expansion. The hybrid Li2S cell exhibited superior cycling performance compared to the solid-state cells in terms of Li2S loading, Li2S utilization, and cycling stability. Finally, we discuss the use of hybrid and high concentration electrolytes to enable other cathode chemistries, particularly those involving conversion.

Improving Cell Resistance and Cycle Life with Solvate/Thiophosphate Hybrid Electrolytes in Lithium Metal and Lithium Sulfur Batteries

Solid electrolytes (SEs) have become a practical option for lithium ion and lithium metal batteries due to their improved safety over commercially available ionic liquids. The most promising of the SEs are the thiophosphates whose excellent ionic conductivities at room temperature are comparable to those of the commercially-utilized ionic liquids. Hybrid solid-liquid electrolytes exhibit higher ionic conductivities than their bare solid electrolyte counterparts due to decreased grain boundary resistance, enhanced interfacial contact with electrodes, and decreased degradation at the interface.In this study, we evaluate a series of hybrid electrolytes made from a ‘solvate’ electrolyte in both Li-Li symmetric cells and in a full cell with a Li2S cathode relative to their bare Li/SE/Li counterparts. Interestingly, hybrid electrolytes made by combining HFE-modified solvates and SE exhibit all the benefits of the interlayer modified SEs, without the necessity of pellet manufacture. The solvate-integrated cathode layer is additionally beneficial for achieving high active material utilization, maintaining intimate interfacial contact, and providing buffer space for volume contraction and expansion. X-ray tomography measurements show the presence of a buffer layer results in substantially less crack formation. The hybrid Li2S cell exhibited superior cycling performance compared to the solid-state cells in terms of Li2S loading, Li2S utilization, and cycling stability. Finally, we discuss the use of hybrid electrolytes to enable other cathode chemistries.

Rapid leakage responsive and self-healing Li-metal batteries

Considering the hyperactive nature of metallic Li and the drawbacks of traditional liquid electrolytes, solid electrolyte is now getting more attentions but confronts obstructions like low Li+ conductivity and poor interface contact. Herein, a new leakage-responsive and self-healing electrolyte (LRE) system is proposed, which consults advantages from both solid electrolytes and liquid electrolytes, including leakage forbiddance, high Li+ conductivity, wettability to electrodes and safety, etc. Moreover, the LRE electrolyte exhibits the characteristic of rapid response to air and then momentarily polymerizes so that the volatilization and oxidation of liquid electrolyte can be stopped in no time. On the other hand, LRE can not only serve as the function of conglutinate the battery injuries and improve the recyclability even batteries were physically damaged, but also contribute to form robust polymeric SEI and suppress the dendrites that helps to improve the battery stability. Significantly as an alternative to both solid electrolyte and traditional liquid electrolyte, this novel electrolyte opens up the possibility in the safe and economical application of LMBs.

Hybrid Electrolytes Composed of Lithium-Ion Conducting Solid Particles and Liquid Electrolytes for Lithium-Ion Cells

Lithium ion batteries for automotive applications such as electric vehicles (EVs) have required to enhance power density, low temperature performance, energy density and safety. Recently, all-solid-state batteries using lithium-ion conducting solid electrolytes have been extensively studied to respond to these demands. However, all-solid-state batteries using solid electrolytes have some issues. Sulfide based solid electrolytes have low chemical stability and oxide electrolytes have large resistance at interfaces between active materials and solid electrolytes.We have developed hybrid electrolytes consisting of lithium-ion conducting solid particles and a gel polymer or liquid electrolyte [1]. The cell with hybrid electrolytes exhibited a low internal resistance, particularly at low temperatures. Moreover, we proposed the mechanism for reducing of the resistance because cyclic carbonates such as PC and PF6 - anion on the surface of lithium-ion conducting solid particles enhance Li+ transference number [2].In this study, we have investigated the detail mechanism of reducing the resistance, and develop high-power lithium-ion batteries. We prepared 1Ah TiNb2O7/LiNi0.5Co0.2Mn0.3O2 pouch cells with hybrid electrolytes to reveal the effective position of lithium-ion conducting solid electrolytes. Figure 1 shows schematic illustrations of the cross-section of the hybrid electrolytes cells. In cell-A, the solid electrolytes were coated on anode. In cell-B, the solid electrolytes layer are not in contact with active materials by inserting a separator. We compared cell-A and B with cell-C without the solid electrolytes layer. Li1.2Zr1.9Ca0.1(PO4)3 (LZCP) was used as a lithium-ion conducting solid electrolytes because of its wide potential window, high chemical stability and relatively low cost of raw materials. Figure 2 and 3(a) show discharge curves of cell-A, B and C at 25℃ and -30℃. The discharge curves of cell-A, B and C showed almost the same at 25℃. On the other hand, the discharge performance of cell-A and B was significantly superior to that of cell-C at -30℃. Comparing cell-A with cell-B, the time to reach 1.5V of cell-A was longer than that of cell-B. Furthermore, typical ac-impedance spectra of the hybrid cells at -30℃ are shown in Figure 3(b). The impedance spectrum exhibits a depressed semicircle. The semicircles of cell-A and B are smaller than that of cell-C. The semicircle of cell-A is smaller than that of cell-B. The semicircle can be interpreted as resulting from the interface resistance such as the charge-transfer process on the electrodes. The interface resistance at low temperature decreased by using the hybrid electrolyte even if the solid electrolytes don’t contact the electrode, however the solid electrolytes in contact with the electrode had the effect of reducing the interface resistance. Considering the above mentioned mechanism of the increasing of Li+ transference number by hybrid electrolytes [2], it was indicated that the interface resistance decreased significantly by putting the solid electrolytes near the surface of the electrodes where the large concentration overpotential is caused during discharge at low temperature. The detail of this mechanism and the effect of reducing resistance by utilizing hybrid electrolytes will be discussed in this presentation.

Electrochemical Properties of Composite Electrodes Containing Lithium-Ion Conducting Solid Particles and Liquid Electrolytes in Lithium-Ion Batteries

Lithium-ion batteries for automotive applications have required to enhance power density, low-temperature performance, life, energy density, and safety. All-solid-state batteries using lithium-ion conducting solid electrolytes have been much interest as candidates to respond to these demands. However, for practical applications, all-solid-state batteries have some problems to solve low charge-discharge performance under high rate and low temperature operations because of low ionic conductivities and large resistances of interface between the solid electrolyte and the active electrode material. We have focused on hybrid electrolytes consisting of lithium-ion conducting solid particles (LCSP) and a gel polymer electrolyte leading to a decrease of cell resistance, especially at low temperatures for LTO cells [1,2]. In this study, we have investigated effects of LCSP with liquid electrolytes in composite electrodes on electrochemical properties and electrode performance in order to develop high-power lithium-ion batteries using the solid electrolytes. NASICON-type Li-Al-Ti-P-O (LATP) particles with a particle size of submicron were used as LCSP. The composite electrodes consisted of LiNi0.5Co0.2Mn0.3O2 (NCM523) as cathode active material, carbon filler, polyvinylidene difluoride binder, and LATP particles, which were coated on aluminum foil as current corrector. Electrochemical measurements of the composite electrodes containing LCSP were performed using a three-electrode glass cell with a lithium metal foil counter electrode, a lithium metal chip reference electrode, a glass filter separator, and LiPF6-based liquid electrolytes. Figure 1 shows typical AC-impedance spectra of the composite electrodes with and without LATP particles at -20°C. The impedance spectra of both electrodes exhibited two depressed semicircles in the high- and low-frequency range, which can be interpreted as resulting from the passivating film formed on the NCM523 active material and the charge transfer process of lithium insertion, respectively. The ohmic resistances at 100 kHz such as the ionic resistance of electrolyte and the resistance of passivating film in the spectra showed no difference between the electrodes with and without LATP. On the other hand, it was noted that the charge transfer resistance of electrode with LATP was significantly smaller than that of electrode without one. Furthermore, the activation energy for the charge transfer of the electrodes with LATP is estimated into 55.7 kJ/mol, which is smaller than that of the electrode without LCSP as shown in Fig. 2. These results indicate that LCSP and liquid electrolytes in the electrodes plays an important role of reducing the charge transfer resistance rather than enhancing the lithium ion conductivity in the electrolytes. Therefore, we consider that LCSP in the electrode enhances to provide lithium ions in the liquid electrolyte to the surface of the active materials, leading to maintain high concentration of lithium ions at the surface of active material. The detail of the mechanism for reducing the charge transfer resistance by containing LCSP to the electrode will be discussed in this presentation. [1] K. Yoshima, Y. Harada and N. Takami, J. Power Sources, 302,283-290(2016). [2] N. Takami, K. Yoshima and Y. Harada, J. Electrochem. Soc., 164,A6254(2017). Figure 1

Improving Cell Resistance and Cycle Life with Solvate/Thiophosphate Hybrid Electrolytes in Lithium Batteries

Solid electrolytes (SEs) have become a practical option for lithium ion and lithium metal batteries due to their improved safety over commercially available ionic liquids. The most promising of the SEs are the thiophosphates whose excellent ionic conductivities at room temperature are comparable to those of the commercially-utilized ionic liquids. Hybrid solid-liquid electrolytes exhibit higher ionic conductivities than their bare solid electrolyte counterparts due to decreased grain boundary resistance, enhanced interfacial contact with electrodes, and decreased degradation at the interface. In this study, we add lithium bis(triflouromethane sulfonyl)imide (LiTFSI) and a highly fluorinated ether (HFE) solvate electrolyte to the surface of Li7P3S11 (LPS) and Li10GeP2S12 (LGPS) pellets and evaluate their overall cell resistance in Li-Li symmetric cells relative to their bare Li/SE/Li counterparts. Time-resolved electrochemical impedance spectroscopy (EIS) shows an order of magnitude lower cell resistance for the LGPS-solvate than for the bare LGPS. Cyclic voltammetry (CV) of the bare and hybrid SE cells shows an order of magnitude higher current density for the LGPS-solvate cell over the bare LGPS. Interestingly, hybrid electrolytes made by combining HFE-modified solvates and SE exhibit all the benefits of the interlayer modified SEs, without the necessity of pellet manufacture. This study suggests that solvates can be used to improve the cell resistance and current density of solid electrolytes by altering the grain boundary structures and the interphase between electrode and electrolyte.

A unified equation for modeling the dependency of conductivity with temperature in ionic systems

One of the most significant features in understanding transport dynamics in ionic conductors is the behavior of the activation energy with temperature. Several mathematical equations to fit conductivity curves, as a function of temperature for all kinds of solid compounds and liquid electrolytes have been used. These curves are generally linear functions or curves that have either positive or negative concavities or a combination of both. In order to fit these curves, three types of commonly accepted functions are available in the literature: Arrhenius function for the linear case, the VTF function for negative concavities, and polynomial and exponential functions for positive concavities. The use of one or the other leads to the formulation of a conduction model that lies behind each equation or equation set, and the interpretation of fitting constants depends on the physical system. In this work a single empirical equation fitting the three types of behavior mentioned above for different ionic systems is proposed.

A Comparative Study of Activated Carbons from Liquid to Solid Polymer Electrolytes for Electrochemical Capacitors

A systematic study on the key factors affecting the performance of electrochemical capacitor electrodes in solid electrolytes and their liquid electrolyte baselines was conducted. The study combined a test matrix of two types of activate carbons (AC) with different specific surface area, pore size and structures at various loadings in three solid and liquid electrolyte pairs. Working curves on loading vs. capacitance of these ACs in solid and corresponding liquid electrolytes revealed the correlation and interconnection of these material properties. A cross-sectional microscopic elemental analysis was used to identify and visualize the influence of these factors. When transition from liquid to solid polymer electrolytes, the infiltration of the electrolyte into the porous carbon plays a critical role in the performance of AC electrode especially at a high loading. When the precursor solution of polymer electrolyte was relatively less viscous, AC with an open structure and mesopores had similar capacitance as their liquid counterparts. A highly viscous precursor solution blocked some access of the polymer electrolytes into the bulk electrode, making infiltration less effective at high loading. This work shows an approach to project the performance of carbon electrodes in solid electrolytes and can provide directions for developing solid-state electrochemical capacitors.

Improving Cell Resistance and Cycle Life with Solvate-Coated Thiophosphate Solid Electrolytes in Lithium Batteries.

Solid electrolytes (SEs) have become a practical option for lithium ion and lithium metal batteries because of their improved safety over commercially available ionic liquids. The most promising of the SEs are the thiophosphates, whose excellent ionic conductivities at room temperature are comparable to those of commercially utilized ionic liquids. Hybrid solid-liquid electrolytes exhibit higher ionic conductivities than their bare SE counterparts because of decreased grain boundary resistance, enhanced interfacial contact with electrodes, and decreased degradation at the interface. In this study, we add lithium bis(trifluoromethane sulfonyl)imide and a highly fluorinated ether solvate electrolyte to the surface of Li7P3S11 (LPS) and Li10GeP2S12 (LGPS) pellets and evaluate their overall cell resistance in Li-Li symmetric cells relative to their bare Li/SE/Li counterparts. Time-resolved electrochemical impedance spectroscopy shows an order of magnitude lower cell resistance for LGPS-solvate than for bare LGPS. In contrast, the LPS-solvate system exhibits a higher cell resistance than bare LPS. Scanning electron microscopy and energy dispersive X-ray spectroscopy show that LGPS allows for the total permeation of the solvate into the bulk SE. Although LPS has smaller grain sizes and higher porosity, it has a higher solubility in 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE), which results in an LPS-TTE interlayer on the surface of the pellet, thereby increasing overall cell resistance. Cyclic voltammetry of the bare and hybrid SE cells shows an order of magnitude higher current density for the LGPS-solvate cell over the bare LGPS. Bare LPS shorts after two cycles, whereas the LPS-solvate cell does not short within the timeframe of the experiment (100 cycles). This study suggests that solvates can be used to improve the cell resistance and current density of SEs by altering the grain boundary structures and the interphase between electrode and electrolyte.

Solid-Liquid Electrolyte as a Nanoion Modulator for Dendrite-Free Lithium Anodes.

Rechargeable lithium (Li) metal batteries are considered the most promising of Li-based energy storage technologies. However, tree-like dendrite produced by irregular Li+ electrodeposition restricts it wide applications. Herein, based on a cation-microphase-regulation strategy, we create solid-liquid electrolytes (SLEs) by absorbing commercial liquid electrolytes into polyethylene glycol (PEG) engineered nanoporous Al2O3 ceramic membranes. By means of molecular dynamics simulations and comprehensive experiments, we show that Li ions are regulated and promoted in the two microphases, the channel phase and nonchannel phase, respectively. The channel phase can achieve homogeneous Li+ flux distribution by multiple mechanisms, including its uniform array of nanochannels and ability to suppress lateral dendrite growth by its high modulus. In the nonchannel phase, PEG chains swollen by electrolyte facilitate desolvation and fast conduction of Li+. As a result, the studied SLEs exhibit high ionic conductivity, low interfacial resistance, and the unique ability to stabilize deposition at the Li anode. By means of galvanostatic cycling studies in symmetric Li cells and Li/Li4Ti5O12 cells, we further show that the materials open a path to Li metal batteries with excellent cycling performance.

Studies of electrochemical interfaces by TOF neutron reflectometry at the IBR-2 reactor

The operation performance of electrochemical energy conversion and storage systems such as supercapacitors and batteries depends on the processes occurring at the electrochemical interfaces, where charge separation and chemical reactions occur. Here, we report about the tests of the neutron reflectometry cells specially designed for operando studies of structural changes at the electrochemical interfaces between solid electrodes and liquid electrolytes. The cells are compatible with anhydrous electrolytes with organic solvents, which are employed today in all lithium ion batteries and most supercapacitors. The sensitivity of neutron reflectometry applied at the time-of-flight (TOF) reflectometer at the pulsed reactor IBR-2 is discussed regarding the effect of solid electrolyte interphase (SEI) formation on metal electrode surface.

Development of ionic liquid and lithium salt immobilized MCM-41 quasi solid-liquid electrolytes for lithium batteries

Li-ion conducting quasi solid-liquid electrolytes (QS-LEs) containing ionic liquid EMIMTFSI, lithium salt LiTFSI and ordered mesoporous MCM-41 (Mobil Composition of Matter no. 41) have been synthesized and characterized by N2-sorption, SEM, TEM, DSC, TGA, and complex impedance spectroscopy techniques. The results show that the synthesized QS-LE has good thermal stability (∼360°C; onset temperature) and a wide electrochemical window ∼5.23V. The ionic conductivity is increases with increasing the amount of Li-IL (LIL) solution and attains a value of ∼6.37×10−4Scm−1 at 30°C and 1.60×10−3Scm−1 at 70°C for QS-LE containing high amount of LIL solution. The high ionic conductivity is attributed to the enormous adsorption of LIL solution on the external surface and in the ordered mesopores channels of the MCM-41. A high total ionic transference number (∼0.99) and cationic transference number (tLi+∼0.35) for QS-LE containing high amount of LIL solution have also been obtained. Furthermore, the QS-LE displays outstanding electrochemical properties (specific capacity ∼153mAhg−1 at C/10 rate; and good high rate capability ∼100mAhg−1 and 83mAhg−1 at 1C and 2C rate respectively) and battery performance with LiFePO4 cathodes.