High Electrochemical Stability Research Articles

Physicochemical Properties of Lithium Bis(trifluoromethanesulfonyl)imide Solutions in Sulfolane

Abstract A study is performed of the physicochemical properties (ionic conductivity, viscosity, and density in the 30–50°C range of temperatures) and the electrochemical and thermal stability of lithium bis(trifluoromethanesulfonyl)imide solutions in sulfolane in the 0.001–1.89 M range of concentrations. It is shown that lithium bis(trifluoromethanesulfonyl)imide solutions in sulfolane exhibit high electrochemical stability (5.75 V vs. Li/Li+) and moderate ionic conductivity (2.75 × 10−3 Ω−1 cm−1 at 30°C for a 1 M solution), which are comparable to the respective parameters of sulfolane solutions of lithium hexafluorophosphate. The structure and transport properties of sulfolane solutions of lithium bis(trifluoromethanesulfonyl)imide are determined by their concentrations. In dilute solutions, lithium bis(trifluoromethanesulfonyl)imide is weakly associated. The degree of electrolytic dissociation of LiN(SO2CF3)2 initially falls and then rises upon an increase in its concentration. The electrolytic dissociation of lithium bis(trifluoromethanesulfonyl)imide rises along with its concentration, due to the formation of ion triplets and more complex ion associates. The constant of association and limit equivalent conductivity of LiN(SO2CF3)2 in sulfolane rise along with temperature, due to a drop in the degree of self-association and the degradation of the solvent’s structure. A specific feature of sulfolane solutions of lithium bis(trifluoromethanesulfonyl)imide is their tendency to form stable supercooled solutions.

A promising strontium and cobalt-free Ba1-xCaxFeO3-δ air electrode for reversible protonic ceramic cells

The air electrode with strontium and cobalt elements has the elemental diffusion or delamination issue on the air electrode/electrolyte interface in reversible protonic ceramic cells (RPCCs). Hence the development of strontium and cobalt-free triple conducting (H+/O2-/e-) air electrodes with high electrochemical activity and stability is urgent. Here, we report a strontium and cobalt-free Ba0.8Ca0.2FeO3-δ (BCF82) air electrode with high catalytic activity and electrochemical stability for oxygen reduction/evolution reactions. A RPCC with the BCF82 air electrode shows a high peak power density of 1.14 W cm−2 in the fuel cell mode and a current density of 3.49 A cm−2 under 1.3 V in the electrolysis mode at 700 °C. Furthermore, the cell demonstrates suitable stability in the fuel cell, electrolysis and reversible modes at 600 °C for hundreds of hours without elemental segregation and delamination issue. This work offers an efficient approach to develop low-cost and durable air electrodes for RPCCs.

Toward Achieving a High Ionic Conducting Halide Solid Electrolyte through Low-Cost Metal (Zr and Fe) and F Substitution and Their Admirable Performance in All-Solid-State Batteries.

Recently, the halide solid electrolyte (SE) system has been widely used in lithium solid-state batteries due to their specific properties, such as the high electrochemical stability window that prevents any side reaction with the electrode/electrolyte interface. Conspicuously, the halide SE possesses very low ionic conductivity values in the range (0.2-0.5) mS cm-1. In this work, we enhance the ionic conductivity of Li3YCl6 SE by the substitution of low-cost Fe and Zr elements on the Y-site and F on the Cl site, in which the electrolyte is prepared through high-energy ball milling without a heat treatment process. The structural analysis reveals that the prepared halide SEs showed the pure phase of the Li3YCl6 tetragonal crystal structure and were free from impurity phases. In the prepared composition, the Li2.4Y0.4Zr0.6Cl6 and Li2.4Y0.4Zr0.6Cl5.85F0.15 electrolyte exhibited a higher ionic conductivity of 2.05 and 1.45 mS cm-1, respectively, than Li3YCl6 (0.26 mS cm-1). Interestingly, the Li2.4Y0.4Zr0.6Cl5.85F0.15 electrolyte possesses a better electrochemical stability window of 1.29-3.9 V than Li2.4Y0.4Zr0.6Cl6 (2.1-3.79 V). Moreover, the electrochemical results revealed that the assembled solid-state battery using Li2.4Y0.4Zr0.6Cl6 and Li2.4Y0.4Zr0.6Cl5.85F0.15 electrolyte demonstrated the higher initial Coulombic efficiency of 84.7 and 87%, respectively, than Li3YCl6 of 82.6%. We consider Li2.4Y0.4Zr0.6Cl5.85F0.15 to be an important electrolyte candidate in all-solid-state batteries.

Enhanced performance of solid polymer electrolytes combining poly(vinylidene fluoride-co-hexafluoropropylene), metal-organic framework and ionic liquid for advanced solid state lithium-ion batteries

The search for sustainable and high-performance materials for lithium-ion batteries is leading to significant advances in solid polymer electrolyte (SPE) technology. However, the current drawbacks of this approach prove the need for further research and development in the field. Herein, novel ternary solid polymer electrolytes have been developed using varying loads of MOF-808 metal-organic framework and [BMIM][SCN] ionic liquid (IL) incorporated in a poly(vinylidene fluoride-co-hexafluoropropylene) matrix. The solid polymer electrolytes were evaluated at morphological, structural, thermal, mechanical and electrochemical levels, and their performance in cycling battery testing was assessed. The results showed a homogeneous structure throughout all the samples and a good dispersion of the distinct components. The polymer polar phase and degree of crystallinity of the samples are increased with increasing IL content, and the thermal and mechanical properties are appropriate for battery application. The ionic conductivity of the samples reaches maximum values of 4.68 × 10−5 S‧cm−1 at room temperature, lithium transference numbers up to 0.65, and high electrochemical stability, making them well-suited for battery applications. The assembled stability after 50 cycles at C/10 with a discharge capacity value of 150 mAh‧g−1 at room temperature was tested/derived. The obtained results show the potential of this system for high performance room temperature solid polymer electrolytes.

Single Cationic Conduction Under Anion-Blocking Conditions in Sodium Ionic Liquids: Na[((FSO2)2N) x ((CF3SO2)(FSO2)N)1−x ]

There is a demand for low-melting-point molten-salt electrolytes with high thermal and electrochemical stability for the development of high-performance sodium-ion batteries. Mixing sodium bis(fluorosulfonyl)amide (NaFSA) and sodium (fluorosulfonyl)(trifluoromethylsulfonyl)amide (NaFTA) results in a large depression in their melting points. In this study, the phase behavior and Na+ transport properties of binary mixtures of NaFSA and NaFTA were investigated. The mixture of NaFSA and NaFTA with a molar ratio of 8:2 has a melting temperature (T m) of 363 K, successfully achieving an ionic liquid consisting of single cationic (Na+) salts. This mixture easily forms a super-cooled liquid. The ionic conductivity (σ) of Na[(FSA)0.8(FTA)0.2] continuously varied from above T m to below T m, obeying the Vogel–Tamman–Fulcher equation, which coincides with its super-cooling nature. The ionic conductivity and apparent Na+ transference number (t Na+) under anion-blocking conditions at T m approached 10−3 S cm−1 and 0.92, respectively.

Application of pfg NMR diffusometry to study diffusion and ionization phenomena in plasticized polymeric membranes doped with ionic liquids

Ionic liquids (ILs) are increasingly used as promising organic solvents for a variety of applications, including electrochemical processes, novel separation techniques and innovative methods of synthesis, due to their low volatility, excellent solvation properties, high ionic conductivity and electrochemical stability. Moreover, the tunable properties of ILs determined by their composition make them favorable candidates as dopants for composite and/or functional polymeric materials, e.g. in the membranes of chemical sensors. To effectively use ILs in polymeric materials and control the characteristics of the latter, one should develop a complete understanding of the properties of ILs in the polymeric phase, such as their diffusion and ionic behavior.In our previous work, we applied pulsed field gradient (PFG) NMR technique to verify the results of a chronopotentiometric method conventionally used to determine the diffusion coefficients and electrolytic properties of electrolytes in plasticized poly(vinyl chloride) (PVC) membranes of chemical sensors. The results obtained with these two independent methods were in good agreement, confirming that PEG NMR diffusometry is a viable technique for assessing the diffusion properties of species even in highly viscous polymeric media of low polarity.Here we report a comprehensive study of the transport and ionic behavior of IL 1-hexyl-3-methyl-1H-imidazolium bis[(trifluoromethyl)sulfonyl]amide ([C6Meim][NTf2]) in a poly(vinyl chloride) matrix, performed in situ by means of PFG NMR diffusometry. A number of sets of spectra for the 1H and 19F nuclei of the [C6Meim][NTf2] ionic liquid in PVC membranes doped with the plasticizer bis(2-ethylhexyl)sebacate were registered at different amplitudes of the magnetic field gradient. The mobility of both individual ions of the IL and the formed ion associates was investigated over a broad range of IL concentrations in the PVC matrix; in addition, the ionization degree and dissociation constant of [C6Meim][NTf2] were determined and their dependence on the IL content was traced.

Palladium/coconut husk biochar composite material as an effective electrocatalyst for ethanol oxidation reaction

This study utilised coconut husk biochar as an alternative sustainable carbon support for Pd-based electrocatalyst for ethanol oxidation reaction in basic medium. Coconut husk biochar (BC) was prepared via slow pyrolysis at 800 °C for 1 h at a ramp rate of 5 °C min−1. The Pd/BC catalyst was prepared via borohydride-facilitated reduction of palladium chloride solution. TEM analysis revealed good dispersion of the Pd nanoparticles on the biochar support with particle size ranging from 1.9 to 3.4 nm. Cyclic voltammetry (CV) measurements of Pd/BC in 1.0 M ethanol in 0.1 M KOH gave an on-set potential of −0.615 V (versus Ag/AgCl) with a forward peak current density of 23.87 mA cm−2, which is slightly higher than the commercial Pd/C catalyst. The Pd/BC also has a higher electrochemical stability and durability than the commercial Pd/C catalyst based on chronoamperometry studies (i.e., 44.43% versus 39.64% current retention). The synthesised coconut husk biochar–supported Pd catalyst exhibited promising results for ethanol oxidation reaction for alkaline direct ethanol fuel cell application.

Multifunctional Additive Enables a "5H" PEO Solid Electrolyte for High-Performance Lithium Metal Batteries.

The solid-state battery with a lithium metal anode is a promising candidate for next-generation batteries with improved energy density and safety. However, the current polymer electrolytes still cannot fulfill the demands of solid-state batteries. In this work, we propose a "5H" poly(ethylene oxide) (PEO) electrolyte via introducing a multifunctional additive of tris(pentafluorophenyl)borane (TPFPB) for high-performance lithium metal batteries. The addition of TPFPB improves the ionic conductivity from 6.08 × 10-5 to 1.54 × 10-4 S cm-1 via reducing the crystallinity of the PEO electrolyte and enhances the lithium-ion transference number from 0.19 to 0.53 via anion trapping due to its Lewis acid nature. Furthermore, the fluorine and boron segments from TPFPB can optimize the composition of the solid-electrolyte interphase and cathode-electrolyte interphase, providing a high electrochemical stability window over 4.6 V of the PEO electrolyte along with significantly improved interface stability. At last, TPFPB can ensure improved safety through a self-extinguishing effect. As a result, the "5H" electrolyte enables the Li/Li symmetric cells to achieve a stable cycle over 2200 h at the current density of 0.2 mA cm-2 with a capacity of 0.2 mA h cm-2; the LiFePO4/Li full cells with a high LFP loading of 8 mg cm-2 exhibits decay-free capacity of 140 mA h g-1 (99% capacity retention) after 100 cycles; and the NCM811/Li cells exhibit a high capacity of 160 mA h g-1 after 50 cycles at 0.5 C. This work presents an innovative approach to utilizing a "5H" electrolyte for high-performance solid-state lithium batteries.

Composite polymer electrolyte with vertically aligned garnet scaffolds for quasi solid-state lithium batteries

Structure design is of great importance for composite solid electrolytes to meet the high requirements for lithium batteries today. Herein, a novel composite polymer electrolyte with vertically aligned fast ion pathways has been constructed through the in-situ UV-induced polymerization of poly (butyl acrylate) (PBA) based gel polymer electrolyte inside the honeycomb-structure Li6.5La3Zr1.5Ta0.5012 (LLZTO) scaffolds by freeze casting. The addition of LLZTO enhances the anion adsorption through the Lewis-acid sites of the La ions and reduces the Li+ complexation by participating in the interaction of CO⋯Li+. Therefore, the interface of PBA and LLZTO scaffold serves as a continuous Li+ transport pathway and the resulting composite solid electrolyte exhibits a high ionic conductivity (5.098×10−4 S cm−1), near single-ion conducting characteristic (a transference number of 0.8) and high electrochemical stability window (5.15 V). Based on the above superior performance, the composite electrolyte promotes uniform distribution of lithium ion concentration and electrolyte potential. Thus, quasi-solid-state LiFePO4/Li cells exhibit excellent cycling performance (capacity retention of 91.7 % after 300 cycles at 0.5 C).

A Vision for LLZO Carbonate Formation: Perspectives on Surface Treatment Approaches and Characterization Techniques

AbstractLi7La3Zr2O12 garnets are among the most promising materials for solid‐state electrolytes thanks to their high electrochemical stability and ionic conductivity. However, they are unstable in air and easily undergo a Li+/H+ exchange reaction, forming a lithiophobic and poorly Li‐conducting surface layer composed of LiOH and Li2CO3 upon further reaction with CO2. Despite a simple reaction mechanism, protonation of LLZO is a complex phenomenon. The thickness and composition of the secondary phases on the surface depend on many parameters both in the LLZO properties and in the storage atmosphere. Due to this complexity, proposing a universal procedure for removing the secondary phases is not simple. However, understanding the role of different parameters and rational selection of characterization techniques makes it possible to find the optimal conditions for removing the LiOH/Li2CO3 layer and further processing each material. This work compares some of the main approaches for cleaning the LLZO surface and describes their advantages and shortcomings. Additionally, the strengths and limitations of the most common characterization techniques for analyzing the (de)protonation of LLZO (XRD, XPS, Raman, NMR, TGA) are explained to help researchers design their experiments more accurately.

Co-free and low strain cathode materials for sodium-ion batteries: Machine learning-based materials discovery

Sodium-ion batteries (SIBs) are promising alternatives to lithium-ion batteries (LIBs) owing to their cost-effectiveness and similar intercalation mechanisms. Layered transition metal oxides (LTMOs) are the promising cathode candidates for SIBs owing to their high voltages and ease of synthesis. However, O3-type LTMOs undergo structural deformation and performance degradation during de-/intercalation. Owing to the limitations of single-element compounds, doping them with various elements can enhance their stability and performance. In this study, machine learning (ML) algorithms are used to predict the structural stability of O3-type materials without phase transitions to facilitate efficient material selection. ML classification models assess the phase stability of cathodes in the pristine and desodiated states. Data sampling and feature engineering enhanced the accuracy of the pristine model from 0.886 to 0.962 and desodiated model from 0.642 to 0.954. Furthermore, a novel database in the form of NaxNi0.5MayMbzO2 (0.5 ≤ x ≤ 1, y + z = 0.5; M = transition metal) was constructed using density functional theory (DFT) calculations. Out of 1,451 LTMOs candidates, we present 128 cathode candidates that satisfy the following conditions: (1) O3 phase is maintained during dis-/charging processes, (2) average voltage ≥ 3 V, (3) theoretical capacity ≥ 200 mAh/g, and (4) -5 % ≤ volume change ≤ 5 %. Among them, 125 materials showed the possibility of stable Co-free cathodes, and 13 materials exhibited -0.5 % < volume change < 0.5 %. This study suggests optimal LTMO candidates that satisfy both the high energy density and electrochemical stability and provides a reliable battery material screening platform.

Effect of LLZTO Tablet Pressing Process on Electrochemical Properties of Button Batteries

AbstractThe garnet‐type Li6.4La3Zr1.4Ta0.6O12 (LLZTO) is a widely studied solid‐state electrolytes (SSEs) due to its high ionic conductivity and electrochemical stability. However, the conventional preparation process of LLZTO electrolyte tablets has encountered several issues such as powder embedment in the mold gaps and inadequate bonding between powders, leading to fragile electrolyte tablets that are prone to cracking. In this study, the effects of LLZTO electrolyte tablet pressing process parameters, including mixed powder content, polyvinyl alcohol (PVA) content and cold pressing pressure, on the electrochemical properties of button cells were investigated. The results indicated that the produced solid‐state electrolyte tablets with high quality, low interfacial resistance and low surface passivation layer (Li2CO3) content was obtained by using 0.8 g of mixed powder content, 0.7 g of PVA content and 20Mpa pressure. The interface resistance decreased from 2927.1 Ω to 1069.7 Ω under these conditions. Additionally, the Li symmetric cell treated with adhesive exhibited stable cycling for over 400 hours at 25 °C under a current density of 0.1 mA ⋅ cm−2.

Synergistic Interface Platforms: Designing Superhydrophilic Conductive Nanoparticle‐Decorated Nanofibrous Membranes

AbstractIn today's technological landscape, advancing methods for producing conductive membranes that simplify and streamline the development of advanced interface materials is crucial. This study introduces a versatile and innovative method for fabricating superhydrophilic, conductive nanofibrous membranes based on the in situ synthesis of polypyrrole nanoparticles on poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP) electrospun fibers. The composite membranes morphologically exhibit a particle‐decorated nanofibrous configuration, with polypyrrole nanoparticles distributed along the individual fibers' surface. The nanoparticle‐nanofiber configuration shows distinctive properties; electrochemically, the electrospun mats demonstrate excellent inherent electrical conductivity, good cyclic and high electrochemical stability, and low resistance. Furthermore, the amphiphilic and superhydrophilic behavior, achieved through nanotopography, porosity and interactions between the intrinsically conductive polymer and the PVDF‐HFP fibers, enables efficient uptake of polar and nonpolar analytes. The membranes also demonstrate good in vitro cell viability of both murine and human fibroblasts. Given its efficient interaction with liquids and omnidirectional 360‐degree conductivity, this material emerges as an excellent candidate for use as a biocompatible, multifunctional interface layer. The produced nanoparticle‐nanofibrous membrane materials offer a promising platform for interface applications, featuring enhanced spatiotemporal configurations and wide‐ranging applicability.

Manipulating the ionic conductivity and interfacial compatibility of polymer-in-dual-salt electrolytes enables extended-temperature quasi-solid metal batteries

Solid polymer electrolytes (SPEs) have shown great promise in the development of lithium-metal batteries (LMBs), but SPEs’ interfacial instability and limited ionic conductivity still prevent their widespread applications. Herein, high-concentration hybrid dual-salt “polymer-in-salt” electrolytes (HDPEs) through formulation optimization were facilely prepared to simultaneously boost ionic conductivity, improve interfacial compatibility, and ensure a wide-temperature-range operation with high safety. An optimized electrolyte (HDPE-0.6) shows negligible corrosion to the aluminum current collector after manipulating the salt ratio of lithium bis(trifluoromethane)sulfonimide and lithium bis(oxalato)borate. In addition, HDPE-0.6 has excellent ionic conductivity (i.e., ∼0.536, ∼0.898, and ∼1.28 mS cm−1 at 0, 30, and 60 °C), approaching 1 mS cm−1 at room temperature. Furthermore, HDPE-0.6 exhibits a high lithium transference number of 0.6 and a high electrochemical oxidation stability potential of > 4.8 V vs. Li/Li+. Additionally, due to the formulation of high-concentration thermally stable lithium salts and the employment of flame-retardant trimethyl phosphate as the solvent, HDPE-0.6 has no safety issues. The resultant LiFePO4|HDPE-0.6|Li cell exhibits high discharge capacity, good rate capability, and excellent cycle stability at extended temperatures of 0, 30, and 60 °C. By coupling theoretical calculations and in-depth X-ray photoelectron spectroscopy, we attribute the excellent cycle stability to the formation of a stable interphase. Moreover, our formulation strategy is suitable for the Na3V2(PO4)3//Na battery when replacing the lithium salts with sodium salts (i.e., sodium bis(trifluoromethane)sulfonimide and sodium bis(oxalato)borate) to yield HDPE-0.6-Na, as demonstrated by excellent cycle stability (e.g., 98.6 % of capacity retention after 300 cycles). Our work demonstrates that the as-developed quasi-solid HDPEs are suitable for LMBs and sodium-metal batteries, and HDPEs can function normally in a wide temperature range.

Effect of fluoride (CoF2) based electrode material for high energy and power density asymmetric flexible supercapacitors

Herein, an asymmetric supercapacitor (ASC) device was assembled by employing the pristine CoF2 as active positive electrode material and activated carbon (AC) as negative electrode material. The CoF2 electrode exhibited an outstanding electrochemical behavior with enhanced specific capacitance (Cs) of 872 F/g at 1 A/g current density in three electrode configurations. The reversible Faradaic redox reactions in CoF2 instigate the formation of cobalt-oxyfluorides and generating the mixed valence state of Co (Co2+ and Co3+) which improves its electrical conductivity and electrochemical behaviors. Furthermore, the room temperature paramagnetic nature of CoF2 increases the gradient force of ions which could possibly increase the redox reactions at the electrolyte/electrode interface. The constructed asymmetric device structure of CoF2//AC revealed a quasi-rectangular shaped cyclic voltametric curve and symmetrical semi-triangular shaped galvanostatic charge-discharge profiles, respectively, which affirms the combined electric double layer capacitance and pseudocapacitive nature by its hybrid assembly. Hence, the constructed CoF2//AC ASC demonstrated a remarkable specific capacitance of 141 F/g, energy density of 44.06 Wh.Kg−1, and power density of 422.97 W.Kg−1 at 1 A/g with the high cell voltage of 1.5 V. The CoF2//AC ASC device retained c.a. 92 % of its initial capacitance and attained over 96 % of Coulombic efficiency after 2000 cycles of charge-discharge profiles at 1 A/g, which suggests the high electrochemical stability. This admirable electrochemical performance and the origin towards the magneto-capacitance of CoF2 could pave a new way to explore next generation high-performance supercapacitors.

Crack‐Free Single‐Crystalline LiNiO2 for High Energy Density All‐Solid‐State Batteries

AbstractSingle‐crystalline layered oxide (LiNi1‐x‐yMnxCoyO2) cathodes have been found to exhibit exceptional electrochemical properties when coupled with various inorganic solid electrolytes (ISEs) in all‐solid‐state batteries (ASSBs). Their advantages stem from the robust morphological integrity with the absence of grain boundaries and the high electrochemical oxidative stability. Here, ASSBs featuring single‐crystalline LiNiO2 (LNO) with the highest Ni content are reported, offering a high theoretical specific capacity of 275 mAh g‐1 alongside a high average discharge voltage (3.7 V vs Li+/Li). Through a careful investigation, it is demonstrated that micron‐sized single‐crystalline LNO (µSC‐LNO) composite cathodes with a halide ISE exhibit a high initial discharge capacity of 205 mAh g‐1 with an outstanding cycle performance over 200 cycles in room‐temperature ASSBs. The significance of engineering parameters is emphasized, such as particle size and specific density, in promoting a homogeneous and fast Li+ transport within the composite cathodes. Furthermore, the formation of undesirable interphase between the halide ISE in the cathode and sulfide ISE separator is elucidated, which may be a critical factor impeding long‐term cyclability of ASSBs. This work provides insights into the design of composite cathodes for high‐energy‐density ASSBs.

Status and Prospect of Two-Dimensional Materials in Electrolytes for All-Solid-State Lithium Batteries.

Replacing liquid electrolytes and separators in conventional lithium-ion batteries with solid-state electrolytes (SSEs) is an important strategy to ensure both high energy density and high safety. Searching for fast ionic conductors with high electrochemical and chemical stability has been the core of SSE research and applications over the past decades. Based on the atomic-level thickness and infinitely expandable planar structure, numerous two-dimensional materials (2DMs) have been exploited and applied to address the most critical issues of low ionic conductivity of SSEs and lithium dendrite growth in all-solid-state lithium batteries. This review introduces the research process of 2DMs in SSEs, then summarizes the mechanisms and strategies of inert and active 2DMs toward Li+ transport to improve the ionic conductivity and enhance the electrode/SSE interfacial compatibility. More importantly, the main challenges and future directions for the application of 2DMs in SSEs are considered, including the importance of exploring the relationship between the anisotropic structure of 2DMs and Li+ diffusion behavior, the exploitation of more 2DMs, and the significance of in situ characterizations in elucidating the mechanisms of Li+ transport and interfacial reactions. This review aims to provide a comprehensive understanding to facilitate the application of 2DMs in SSEs.

Optimization of two-dimensional solid-state electrolyte–anode interface by integrating zinc into composite anode with dual-conductive phases

Solid-state electrolytes (SSEs) are a solution to safety issues related to flammable organic electrolytes for Li batteries. Insufficient contact between the anode and SSE results in high interface resistance, thus causing the batteries to exhibit high charging and discharging overpotentials. Recently, we reduced the overpotential of Li stripping and plating by introducing a high proportion of dual-conductive phases into a composite anode. The current study investigates the interface resistance and stability of a composite electrode modified with Zn and a lower proportion of dual-conductive phases. Zn-cation-adsorbed Prussian blue is synthesized as an intermediate component for a Zn-modified composite electrode (Li-FeZnNC). The Li-FeZnNC symmetric cell presents a lower interface resistance and overpotential compared with Li-FeNC (without Zn modification) and Li-symmetric cells. The Li-FeZnNC symmetric cell shows high electrochemical stability during Li stripping and plating at different current densities and high stability for 200 h. Full batteries with a Li-FeZnNC composite anode, garnet-type SSE, and LiFePO4 cathode show low charging and discharging overpotentials, a capacity of 152 mAh g−1, and high stability for 200 cycles.

Application of ionic liquids in ion-selective electrodes and reference electrodes: A review.

Ionic liquids (ILs) are organic chemical compounds that are composed only of ions, a large organic cation and a smaller inorganic or organic anion. These are salts whose melting point is lower than the boiling point of water. ILs have many interesting properties, thanks to which they find great practical applications in analytics, electrochemistry, separation techniques, catalysis and others. One of the many areas of application of ionic liquids is sensors especially electrochemical sensors including ion-selective electrodes. In this case, the properties of ILs that are particularly useful include very good electrical conductivity, high electrochemical stability, good extraction properties, hydrophobic character and compatibility with other materials, e. g. polyvinyl chloride plasticizers or carbon nanomaterials. ILs were used as components of ion-selective membranes, both polymeric ones based on PVC and membranes in carbon paste electrodes. ILs performed various functions in these membranes, including lipophilic ionic additive, ionophore/ion exchanger, plasticizer, transducer media and matrix. They were also used as a component of the intermediate layer in solid contact ISEs. The last chapter presents examples of the use of ILs in reference electrodes. This review discusses the use of ionic liquids in ion-selective electrodes (ISEs) and reference electrodes over the last ten years.

Optimisation of electrochemical performance of Sr(Fe,Sb)O3-δ air electrodes for intermediate-temperature solid oxide cells through spray-pyrolysis processing

The effects of replacing iron with cobalt and employing either Pechini or spray pyrolysis synthesis routes have been studied for the perovskite system SrFe0.9-xCoxSb0.1O3-δ (x = 0; 0.45; 0.9) to optimise sustainable air electrodes for intermediate-temperature solid oxide cells. The electrochemical performance of Pechini-prepared compositions improves with increasing cobalt content, attributable to higher electronic conductivity and oxygen-vacancy concentration, and lower processing temperature from 1300 ᵒC, for SrFe0.9Sb0.1O3-δ, to 1200 and 1100 ᵒC, for SrFe0.45Co0.45Sb0.1O3−δ and SrCo0.9Sb0.1O3−δ, respectively, with SrCo0.9Sb0.1O3-δ exhibiting an area specific resistance (ASR) of 0.084 Ω cm2 at 700 °C. The electrochemical stability of Fe-containing Pechini-based compositions is impaired, most likely due to a higher processing temperature. However, the very low processing temperature of 800 °C for spray-pyrolysed electrodes produces similar electrochemical performances for Co-containing and Co-free compositions (ASR≈ 0.065 Ω cm2 at 700 °C for SrFe0.9Sb0.1O3-δ) and high electrochemical stability with practically unaltered electrode polarisation resistance on thermal cycling.