Low Ionic Resistance Research Articles

Understanding the Carbon Additive/Sulfide Solid Electrolyte Interface in Nickel-Rich Cathode Composites and Prioritizing the Corresponding Interplay between the Electrical and Ionic Conductive Networks to Enhance All-Solid-State-Battery Rate Capability.

All-solid-state lithium batteries, including sulfide electrolytes and nickel-rich layered oxide cathode materials, promise safer electrochemical energy storage with high gravimetric and volumetric densities. However, the poor electrical conductivity of the active material results in the requirement for additional conducive additives, which tend to react negatively with the sulfide electrolyte. The fundamental scientific principle uncovered through this work is simple and suggests that the electrical network benefits associated with the introduction of short-length carbons will eventually be overpowered by the increase in bulk resistance associated with their instability in the sulfide electrolyte. However, applying just the right amount of short carbon fibres minimizes degradation of the sulfide solid electrolyte and maximizes the electron movement. Therefore, we propose the application of a low-weight-percent carbon nanotubes (CNTs) coating on the nickel-rich cathode LiNi0.8Co0.1Mn0.1O2 (NCM811) along with large-aspect-ratio carbon nanofibers (CNFs) as the primary conductive additive. When only 0.3 wt % CNTs was utilized with 4.7 wt % CNFs, an initial Coulombic efficiency of 83.55% at 0.05C and a notably excellent capacity retention of 90.1% over 50 cycles at 0.5C were achieved along with a low ionic resistance. This work helps to confirm the validity of applying short carbon pathways in sulfide-electrolyte-based cathode composites and proposes their combination with a larger primary carbon additive as a solution to the ongoing all-solid-state battery rate and instability issues.

Enhancing Surface Charge Density of Graphene Oxide Membranes through Al(OH)4− Anion Incorporation for Osmotic Energy Conversion

Graphene oxide (GO) has been extensively studied for fabricating ion exchange membranes. This material is of interest due to its surface‐governed charge which, combined with the interlayer distance between the GO flakes stack, offers ion selectivity. However, obtaining high‐performing membranes with high ion selectivity and low ionic resistance remains challenging. To address this issue, Al(OH)4− anions are incorporated into graphene oxide membranes to increase their spontaneous negative surface charge. The anions are successfully formed and encapsulated through a reaction with the alumina support under alkaline conditions during the membrane fabrication. A modeling of the system proves the anchoring of the Al(OH)4− anions within the GO matrix. The incorporation of these anions significantly improves the permselectivity and reduces the ionic resistance, reaching approximately 95% and 2 Ω cm2, respectively. The GO‐modified membranes also present mono‐valent selectivity, which can boost reverse electrodialysis power densities.

High monovalent/divalent permselectivity and low ionic resistance of ionene-based anion exchange membranes in electrodialysis

This study presents an investigation on the monovalent/divalent ion permselectivity of anion exchange ionenes, a distinct class of solid polymer polyelectrolytes having cationic fixed charge groups located directly on the polymer backbone, rather than being pendant. These ionenes are commercially available as Aemion® AEMs and are based on hexamethyl-p-terphenyl poly(benzimidazolium) (HMT-PMBI). Monovalent/divalent permselectivity values of four Aemion® membranes of different thickness and ion exchange capacity were determined via electrodialysis in a mixed electrolyte system comprising chloride/sulfate anions. To fully understand the transport phenomena in these materials, ion transport properties were studied in conjunction with water uptake and ionic conductance. When the AEMs were exposed to mixed chloride/sulfate solutions, their water uptake significantly increased compared to purely chloride containing solutions, and the concentration of fixed charge groups in the AEMs consequently decreased. We find that thicker ionenes with lower IEC exhibit the highest permselectivity. The data also reveal that thinner AEMs yield a greater ionic flux loss and decreased permselectivity values, particularly in case of lower IEC AEMs. Surprisingly, despite its low water uptake and high resistance, commercial Selemion AMV possesses lower permselectivity than low IEC ionene-based Aemion® AEMs, which we explain on the basis of the highly tortuous internal morphology of low water content ionenes. Permselectivity-to-resistance ratio values are an order of magnitude higher for low IEC ionenes when compared with high IEC ionenes and Selemion AMV.

Ultraviolet-Assisted Printing of Flexible Solid-State Zn-Ion Battery with a Heterostructure Electrolyte.

Flexible solid-state Zn-ion batteries (ZIBs) have garnered considerable attention for next-generation power sources, but the corrosion, dendrite growth, and interfacial problems severely hinder their practical applications. Herein, a high-performance flexible solid-state ZIB with a unique heterostructure electrolyte is facilely fabricated through ultraviolet-assisted printing strategy. The solid polymer/hydrogel heterostructure matrix not only isolates water molecules and optimizes electric field distribution for dendrite-free anode, but also facilitates fast and in-depth Zn2+ transport in the cathode. The in situ ultraviolet-assisted printing creates cross-linked and well-bonded interfaces between the electrodes and the electrolyte, enabling low ionic transfer resistance and high mechanical stability. As a result, the heterostructure electrolyte based ZIB outperforms single-electrolyte based cells. It not only delivers a high capacity of 442.2 mAh g-1 with long cycling life of 900 cycles at 2 A g-1 , but also maintains stable operation under mechanical bending and high-pressure compression in a wide temperature range (-20 °C to 100 °C).

A series of crumpled ball-like metal oxide-based catalysts enabled by aerosol synthesis

Two-dimensional nano metal oxides (2D-NMOs) have attracted great concerns due to high exposure of active sites and short ion transport distance. However, 2D-NMOs with the layered structure render to restack into bulk ones, resulting in the active-sites coverage and ion-transport blockage. Here, crumpled 2D NMOs with paper-ball-like shape was proposed to avoid the restacking. Our new strategy can convert diversity of metal oxide into paper-ball-like structure with controllable composition by overcoming the fragile nature of metal oxide and limitation of growth pattern. Resultantly, as-prepared 2D NMOs demonstrated superior catalytic activity and durability in both oxygen evolution reaction (OER) and organic dye degradation reaction, owing to their high exposure of active sites and low ionic diffusion resistance.

Ion-Selective Microporous Polymer Membranes with Hydrogen-Bond and Salt-Bridge Networks for Aqueous Organic Redox Flow Batteries.

Redox flow batteries (RFBs) have great potential for long-duration grid-scale energy storage. Ion-conducting membranes are a crucial component in RFBs, allowing charge-carrying ions to transport while preventing the cross-mixing of redox couples. Commercial Nafion membranes are widely used in RFBs, but their unsatisfactory ionic and molecular selectivity, as well as high costs, limit the performance and the widespread deployment of this technology. To extend the longevity and reduce the cost of RFB systems, inexpensive ion-selective membranes that concurrently deliver low ionic resistance and high selectivity toward redox-active species are highly desired. Here, high-performance RFB membranes are fabricated from blends of carboxylate- and amidoxime-functionalized polymers of intrinsic microporosity, which exploit the beneficial properties of both polymers. The enthalpy-driven formation of cohesive interchain interactions, including hydrogen bonds and salt bridges, facilitates the microscopic miscibility of the blends, while ionizable functional groups within the sub-nanometer pores allow optimization of membrane ion-transport functions. The resulting microporous membranes demonstrate fast cation conduction with low crossover of redox-active molecular species, enabling improved power ratings and reduced capacity fade in aqueous RFBs using anthraquinone and ferrocyanide as redox couples.

Effect of boron-based glass additives on the ionic conductivity of Li1.3Al0.3Ti1.7(PO4)3 solid electrolyte

Li1.3Al0.3Ti1.7(PO4)3 (LATP) is a promising candidate as the solid electrolyte in energy storage devices. For practical considerations, the most common ways to ameliorate the low density and high ionic resistance of LATP are usually to use glass additives. In this work, the boron-based (B2O3, B2O3-SiO2-PbO (BSP), and B2O3-SiO2-K2O-Al2O3 (BSKA)) glass are added into LATP by solid method. As the results, the main diffraction peaks of all prepared samples maintain the NASICON-type with the R-3c space group. Meanwhile, the symmetric stretching vibrations of O-P-O bands is redshifted with the addition of boron-based glass, which plays a positive role in bulk conductivity. Additionally, the introduction of boron-based glass additives is effective to increase the grain sizes of the LATP samples. The relative density of the sample is obtained from 93.37% to 95.42%. Furthermore, the total conductivities of 1.33 × 10−4, 1.37 × 10−4, 1.97 × 10−4 S cm−1 are obtained in ceramic samples after B2O3, BSP and BSKA glass additives adding, respectively. The activation energy shows a reduction of 5.26% to 0.36 eV after BSP and BSKA glass adding. Satisfactorily, B2O3, BSP and BSKA glass have a certain influence on the conductivity, and bear a more favorable argument for the regulation of the morphology and density in the future.

Multilayered Ceramic Membrane with Ion Conducting Thin Layer Induced by Interface Reaction for Stable Hydrogen Production

AbstractConventional methods for fabricating multilayered ceramic membranes with ion conducting dense thin layers are often cumbersome, costly, and limited by poor adhesion between layers. Inspired by the architectural structure of the rooted grasses in soil, here, we report an interface‐reaction‐induced reassembly approach for the direct fabrication of Ce0.9Gd0.1O2−δ (CGO) thin layers rooted in the parent multilayered ceramic membranes by only one firing step. The CGO dense layers are very thin, and adhered strongly to the parent support layer, ensuring low ionic transport resistance and structural integrity of the multilayered membranes. When using as an oxygen permeable membrane for upgrading fossil‐fuel‐derived hydrogen, it shows very long durability in harsh conditions containing H2O, CH4, H2, CO2 and H2S. Furthermore, our approach is highly scalable and applicable to a wide variety of ion conducting thin layers, including Y0.08Zr0.92O2−δ, Ce0.9Sm0.1O2−δ and Ce0.9Pr0.1O2−δ.

Multilayered Ceramic Membrane with Ion Conducting Thin Layer Induced by Interface Reaction for Stable Hydrogen Production.

Conventional methods for fabricating multilayered ceramic membranes with ion conducting dense thin layers are often cumbersome, costly, and limited by poor adhesion between layers. Inspired by the architectural structure of the rooted grasses in soil, here, we report an interface-reaction-induced reassembly approach for the direct fabrication of Ce0.9 Gd0.1 O2-δ (CGO) thin layers rooted in the parent multilayered ceramic membranes by only one firing step. The CGO dense layers are very thin, and adhered strongly to the parent support layer, ensuring low ionic transport resistance and structural integrity of the multilayered membranes. When using as an oxygen permeable membrane for upgrading fossil-fuel-derived hydrogen, it shows very long durability in harsh conditions containing H2 O, CH4 , H2 , CO2 and H2 S. Furthermore, our approach is highly scalable and applicable to a wide variety of ion conducting thin layers, including Y0.08 Zr0.92 O2-δ , Ce0.9 Sm0.1 O2-δ and Ce0.9 Pr0.1 O2-δ .

Development and Improvement of an Electrochemical Cell for X-Ray Fluorescence and Absorption Spectroscopy

The use of X-ray spectroscopy is an essential technique for the study of any material. Our research investigated the electrochemical cell design and improvement for X-ray absorption and fluorescence spectroscopy. Our objective was to improve the design capability of the current electrochemical cell design to perform absorption and fluorescence spectroscopy at once. By changing the geometry of the receiving window on the electrochemical cell, we could accomplish both fluorescence and absorption spectroscopy functions for CHEXS experiments. Our approach was a simple, inexpensive prototype cycle that anyone could use. Using a hobbyist Computer Numerical Control (CNC) and free 3D CAD software, anyone can develop a reliable electrochemical cell using our design. The electrochemical cell was fabricated using a small computer numerical control system, which allowed a fast turnaround for our project. Our work contributed to designing an open-source electrochemical cell that CHESS or any user could use, modify and share for future projects. Scientifically, we aimed to implement the ability to do both fluorescence and absorption spectroscopy, incorporate the ability to purge the cell with a gas, decrease ionic resistance in the cell to have all the electrodes within the same cell, and avoid leaks.The development of a new electrochemical cell design was made to improve the reliability and performance of the cell for CHESS experiments. By re-arranging the positions of the working electrode (WE), counter electrode (CE), and reference electrode (RE), we accomplished low ionic resistance within the cell. In addition, creating a 45-degree angle slope on both sides of the X-ray receiving window will allow the design of the electrochemical cell to perform fluorescence and absorption spectroscopy simultaneously. Furthermore, an add-on to the top of the electrochemical cell was designed to perform gas purging of the cell successfully. Lastly, the change from an o-ring to a gasket addressed the leakage problem thoroughly.

Anode‐Free Lithium–Sulfur Cells Enabled by Rationally Tuning Lithium Polysulfide Molecules

The two major barriers of practical lithium-sulfur batteries are the poor reversibility of lithium-metal anode and sluggish kinetics of sulfur cathode. Here, we report a simple yet cogent, molecular tailoring approach for lithium polysulfides, enabling a synergistic enhancement of anode reversibility and cathode kinetics. We show that SnI4 coordinates with lithium polysulfides to form soluble complexes, resulting in a Li2 SnS3 -rich anode interphase layer. As Li2 SnS3 is stable against parasitic reactions and has a lower ionic resistance over cycling, the Li plating/stripping efficiency is greatly improved. In addition, the formation of soluble complexes between SnI4 and lithium polysulfides play a non-negligible role in suppressing the clustering behavior of lithium polysulfide molecules, resulting in a significant enhancement in sulfur conversion kinetics under lean electrolyte conditions. The synergistic improvement is validated in anode-free, lean-electrolyte pouch cells with a Li2 S cathode that displays capacity retention of 78 % after 100 cycles.

Anode‐Free Lithium–Sulfur Cells Enabled by Rationally Tuning Lithium Polysulfide Molecules

AbstractThe two major barriers of practical lithium–sulfur batteries are the poor reversibility of lithium‐metal anode and sluggish kinetics of sulfur cathode. Here, we report a simple yet cogent, molecular tailoring approach for lithium polysulfides, enabling a synergistic enhancement of anode reversibility and cathode kinetics. We show that SnI4coordinates with lithium polysulfides to form soluble complexes, resulting in a Li2SnS3‐rich anode interphase layer. As Li2SnS3is stable against parasitic reactions and has a lower ionic resistance over cycling, the Li plating/stripping efficiency is greatly improved. In addition, the formation of soluble complexes between SnI4and lithium polysulfides play a non‐negligible role in suppressing the clustering behavior of lithium polysulfide molecules, resulting in a significant enhancement in sulfur conversion kinetics under lean electrolyte conditions. The synergistic improvement is validated in anode‐free, lean‐electrolyte pouch cells with a Li2S cathode that displays capacity retention of 78 % after 100 cycles.

Highly selective porous separator with thin skin layer for alkaline water electrolysis

Advanced porous separators with thin selective skin layers to reduce the hydrogen permeation are developed for applications in alkaline water electrolysis. A thin skin layer based on crosslinked polyvinyl alcohol (cPVA) is fabricated on a porous substrate by a facile and scalable ultrasonic spray coating process. As the number of ultrasonic spraying cycles increases, the resulting separator demonstrates a decrease in the large-diameter pore fraction, an increase in the bubble-point pressure, and a reduction in the hydrogen permeability without a significant increase in the areal resistance. As a result, the optimized separator with a cPVA skin layer combines a low ionic resistance of 0.267 Ω cm2, a high bubble point pressure of 2.71 bar, and a low hydrogen permeability of 1.12 × 10−11 mol cm−2 s−1 bar−1. The electrolytic cell assembled with cPVAZ-30 achieves current densities of 861 mA cm−2 and 1890 mA cm−2 at 2.0 V and 2.6 V, respectively, in a 30 wt% KOH electrolyte solution at 80 °C.

Development of an innovative workflow to optimize the fast-charge capability of lithium-ion battery cells

State-of-the-art design criteria for electrodes in lithium-ion battery cells focus mostly on an increase of the energy density. Optimizing the fast-charge capability of a cell, especially with respect to lithium-plating, contradicts to these conventional design criteria and are therefore often neglected. This study presents an innovative workflow to resolve this conflict. An extensive electrode and cell characterization with respect to porosity and coating thickness is carried out to determine the corresponding electrode inner resistance, which limits the fast-charge capability of a cell. An empirical model is derived from these results, where the parameters are fitted with measurements. This model is used to determine the optimal porosity and coating thickness for a graphite-anode to obtain the lowest ionic resistance for a given volumetric capacity and thus, the lowest risk of lithium-plating. If the fast-charge capability is one of the design criteria, then it is necessary to determine the optimum porosity and coating thickness as explained in this study. Otherwise, high coating thicknesses or low porosities can lead to unnecessary high ionic resistance in the case of non-optimized settings. The innovative workflow of this study can be used as a guideline to determine the optimal parameter setting of an anode design. • Study on the effect of porosity and thickness on inner resistances of electrodes. • Ionic resistance of the anode mostly affects fast-charge capability of Li-ion cells. • Model to calculate the ionic resistance based on porosity and thickness of anode. • Optimal parameter setting for low ionic resistance at desired volumetric capacity. • Workflow to optimize the fast-charge capability of a Li-ion cell.

Engineering of electrospun polyimide separators for electrical double-layer capacitors and lithium-ion cells

Functionalised polyimide (PI) separators, with high electrolyte wettability and good thermo-dimensional stability, in combination with electrolytes provide ionic conductivities > 1 mS for electrical double-layer capacitors (EDLCs) and lithium-ion batteries (LIBs). The mechanical strength of PI separators can be further improved by a factor of 3 via the optimisation of ratio of soft and hard segments, and the introduction of 5% SiO2 nanoparticles (NPs). The electrolyte uptake capability and ionic conductivity of this copolymerized PI separator is also promoted by the addition of SiO2 NPs, favouring the high-rate performances of EDLCs and LIBs. The cyclic voltammetry (CV) curves of an EDLC with this separator show the rectangle shape of a typical capacitor, indicating the low ionic resistance of this copolymerized PI separator. For the usage in the LIBs, on the other hand, a coating of low-density polyethylene (LDPE) onto this PI-SiO2 (PI–SiO2@PE) separator enables the thermal shutdown function of a LIB without sacrificing cell performance. There is no significant change in morphology for this PI-SiO2@PE separator after the 50-cycle full cell test, indicating its promising application potential in LIBs. The study has demonstrated the ability to tailor the multi functionality of the polyimide separator to optimise it properties for specific applications.

Processing combustion synthesized Mg0.5Zr2(PO4)3 nanopowders to thin films as potential solid electrolytes

Mg0.5Zr2(PO4)3 is a promising electrolyte for Mg solid-state batteries. But it is difficult to achieve high-density thin films with phase purity. Here, we synthesized Mg0.5(1+x)FexZr2−x(PO4)3 nanopowders using liquid-feed flame spray pyrolysis and used the product to form transparent thin films via simple pressureless sintering at 1100 °C. The influence of Fe on the phase and microstructure were discussed and the bottlenecks during Mg2+ conduction pathway were calculated. The dense and high-purity Mg0.6Fe0.2Zr1.8(PO4)3 exhibited an extremely low ionic area specific resistance of 1.6 kΩ cm2 at 200 °C. This paper presents a method for preparing dense, high-purity solid electrolytes at modest sintering temperatures.

Novel sulfonated poly (ether ether ketone)/rGONR@TiO2 nanohybrid membrane for proton exchange membrane fuel cells

In this research, the proton exchange membrane (PEM) composed of sulfonated poly(ether ether ketone) (SPEEK) as a matrix material and reduced graphene oxides nanoribbons (rGONR) wrapped titanium dioxide (TiO2) microspheres as filler is fabricated using the simple solution casting method. The incorporation of the of rGONR (optimized amount) wrapped TiO2 (rGONR@TiO2) nanofiller, acts as a novel self-humidifying/water trapping nanoshell and regulates the presence of (SO3−)n ionic clusters in SPEEK matrix to build a better network without losing the motion of protons. The network formation dramatically stimulated the proton transport of the SPEEK/rGONR@TiO2 (SPTC) nanohybrid PEM and improved it up to 188% (0.62 S cm−1 for SPEEK to 1.79 S cm−1 for SPTC) at 100 °C. The activation energy (Ea) and diffusion coefficient (Dσ) for SPTC membrane are found to be 9.15 kJ mol−1 and 4.92 × 10−8 m2 s−1, respectively, which is in an excellent agreement to ensure better proton conductivity and lower ionic resistance.

Fe Doped, Dense, High Phase Purity and Nano-Grained Mg0.5zr2(Po4)3 Thin Films

Mg0.5Zr2(PO4)3 is a priority electrolyte for Mg solid state batteries. However, it is difficult to achieve high density and phase purity simultaneously, especially in thin films. Here, we processed liquid-feed flame spray pyrolysis synthesized MZPFex nanopowders to make transparent films via simple pressureless sintering at 1100°C. The influence of Fe on the phase and microstructure are discussed. In particular, dense and high phase purity Mg0.6Fe0.2Zr1.8(PO4)3 exhibits extremely low ionic area specific resistance, 1.6 kΩ cm2. This paper presents an effective method to prepare dense, high phase purity solid electrolytes at modest sintering temperatures.

Novel anion exchange membrane with low ionic resistance based on chloromethylated/quaternized‐grafted polystyrene for energy efficient electromembrane processes

ABSTRACTA novel anion‐exchange membrane has been manufactured by chloromethylation and subsequent quaternization of polystyrene within a graft copolymer films based on UV‐oxidized polymethylpentene. Particular attention is given to the kinetics of chloromethylation and the influence of the reaction conditions on the properties of the anion‐exchange membranes. By means of variation of the polystyrene content and its crosslinking degree we have obtained membranes that have an ion‐exchange capacity from 1.1 to 2.9 mmole g−1, anion transport numbers between 91.0 and 95.5% and specific ionic conductivities ( ranging from 2 to 25 mS cm−1. The developed membranes due to their low thickness and high conductivities have a remarkably low surface ionic resistance of around 0.6 Ω cm2. It was calculated that the use of the developed materials will increase the efficiency of reverse electrodialysis energy production by 8–10% compared to the state of the art membranes. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 137, 48656.

Effects of flow direction on dynamic response and stability of nonhumidification PEM fuel cell

The flow directions of reactants in the anode and cathode channels have considerable impact on the dynamic responses of the nonhumidification polymer electrolyte membrane fuel cells (PEMFCs). In this study, the dynamic responses of nonhumidification PEMFCs using short-side-chain membranes are investigated with the variation in the flow direction of reactants using a three-dimensional transient simulation model. The dynamic responses of the cell voltages and local transfer currents are analyzed with the abrupt increase in the current density. Generally, the counter-flow cell exhibits a higher performance than the co-flow cell. During the load change, the co-flow cell experiences zero-power periods owing to the low cell voltage. Moreover, the counter-flow cell shows more uniform variation in the local transfer current and yields an even distribution in the overshoot compared to the co-flow cell owing to the higher membrane water content and the lower ionic resistance. However, the counter-flow cell results in a longer settling time compared to the co-flow cell owing to the large increase in the membrane water content. Overall, for the nonhumidification PEMFCs, the counter-flow cell is determined to be a preferred flow design owing to the higher performance and stability.