Trifluoromethylsulfonyl Research Articles

Divalent Viologen Cation‐Based Ionogels Facilitate Reversible Intercalation of Anions in PProDOT‐Me2 for Flexible Electrochromic Displays

AbstractThe electrochromic (EC) polymer poly (3,4‐(2,2‐dimethylpropylenedioxy)thiophene) (PProDOT‐Me2) is expected to be used in flexible e‐paper displays because of its great optical modulation ability and inherent flexibility. While the EC effect is primarily determined by the anions and cations in the electrolyte, yet suffers from inorganic salt based on monovalent Li+ cations and corresponding anions, such as lithium perchlorate(LiClO4), lithium bis(trifluoromethane sulfonyl) imide (LiTFSI), and lithium trifluoromethane sulfonate (LiTRIF), which may impact the overall EC performance of the EC device caused by insufficient ion doping/de‐doping processes. Herein, the divalent viologen cation‐based ionogel (VGE) is developed to tackle the challenge. Owing to its more anions design, the doping/de‐doping process in the PProDOT‐Me2 is more sufficient, thereby enhancing the optical modulation range (ΔR = 39.4%) of PProDOT‐Me2, compared to monovalent Li+ cation‐based ionogel (ΔR = 13.3%). Meanwhile, the VGE has good interface contact with PProDOT‐Me2 and the flexible electrode, which makes the VGE‐based EC device (V‐ECD) exhibit commendable mechanical stability. To demonstrate the potential application in flexible e‐paper displays, the simple eight‐digit EC display device is assembled from seven V‐ECDs, each of which hasa high switching speed, robust cycling stability, and low operating energy consumption.

Flexoelectric Ionic Liquid-Grafted Triblock Copolymers for Energy Harvesting under Flexural Deformation.

The goal of the present article is to develop flexoelectric polyelectrolyte elastomers for energy harvesting based on a poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) dimethacrylate (PEG-b-PPG-b-PEG-DMA) triblock grafted with an ionic liquid (IL) such as allylmethylimidazolium bis(trifluoromethane sulfonyl) imide (AMIMTFSI). The IL-grafted triblock copolymer network possesses a balance of reasonably good ionic conductivity and high ion polarization during cantilever bending. Of particular importance is the achievement of high flexoelectric coefficients in some flexoelectric polyelectrolyte elastomer (FPE) compositions reaching 1368 μC/m at ambient temperature during mechanical deformation under intermittent square-wave bending mode. With the addition of a 10 wt % lithium bis(trifluoromethane sulfonyl) imide (LiTFSI) salt, the flexoelectric coefficient further improved to 1737 μC/m, which is the highest among all piezoelectric and flexoelectric materials hitherto reported, and thus it opens a new opportunity for clean energy harvesting from a vibrating natural environment.

Na<sup>+</sup> Mobility in PEO-Based Composite Solid-State Electrolytes by NMR

Charge transfer and mobility are essential for electrochemical processes in batteries, which need to be understood in detail for optimization, especially in the case of all-solid-state batteries. Wide line NMR is well-known in solid-state NMR and allows the quantification of ion mobility in ordered crystalline and amorphous structures. Temperature-dependent <sup>23</sup>Na-NMR is sensitive to ion mobility via longitudinal relaxation, but also via line analysis and transverse relaxation. As <sup>23</sup>Na is a spin 3/2 nucleus, <sup>23</sup>Na-NMR is also susceptible to electric field gradients caused by their nearest neighbor environment and, therefore, reflects not only the mobility of <sup>23</sup>Na<sup>+</sup> but also the molecular dynamics in the neighborhood, which are investigated in this paper. The named NMR methods were explored to study <sup>23</sup>Na<sup>+</sup> mobility in the solid electrolytes NaSICON (sodium (Na) Super Ionic CONductor, here Na<sub>3.4</sub>Zr<sub>2</sub>Si<sub>2.4</sub>P<sub>0.6</sub>O<sub>12</sub>), the salt NaTFSI (sodium bis(trifluoromethyl sulfonyl)imide), as well as in the polymer-based electrolytes PEO-NaSICON, PEO-NaTFSI, and PEO-NaTFSI-NaSICON.

Solid Polymer Electrolytes with Dual Anion Synergy and Twofold Reinforcement Effect for All-Solid-State Lithium Batteries.

Solid polymer electrolytes (SPEs) have emerged as a viable alternative to traditional organic liquid-based electrolytes for high energy density and safer lithium batteries. Poly(ethylene oxide) (PEO)-based SPEs are considered one of the mainstream SPE materials with excellent dissociation ability of lithium salts. However, the inferior ionic conductivity at room temperature and poor dimensional stability at high temperature limit their utilization. In this work, a semi-interpenetrating polymer network (semi-IPN) forming a precursor based on an ionic liquid (IL) monomer and linear PEO chains were introduced into an electrospun poly(acrylonitrile) (PAN) fibrous mat with subsequent thermal-initiated cross-linking. 1,4-Diazabicyclo [2.2.2] octane (DABCO) and 4-(chloromethyl) styrene were used to synthesize the styrenic-DABCO-based IL monomer with bis(trifluoromethane sulfonyl)imide (TFSI-) or bis(fluoromethane sulfonyl)imide (FSI-) as the anion, named as SDTFSI and SDFSI, respectively. Together, the FSI- and TFSI- anions demonstrate a synergistic effect in providing ion-conductive LiF and Li3N-rich inorganic SEI layer with enhanced lithium dendrite suppression ability. The twofold reinforcement effect is achieved collectively from the semi-IPN structure and the three-dimensional (3D) PAN network that help to construct highly efficient and uniform ion transport channels with excellent flexibility, further suppressing the lithium dendrite growth. The SPEs were dimensionally stable even at elevated temperatures of 150 °C. Moreover, the SPEs show an ionic conductivity of 4.4 × 10-4 S cm-1 at 25 °C and 1.81 × 10-3 S cm-1 at 55 °C and a lithium-ion transference number of 0.56. The favorable electrochemical performance of the SPEs was verified by operating LiFePO4/Li and NMC/Li cells.

Protective behavior of phosphonate-functionalized imidazolium ionic liquid and its impact on the Li-ion battery performance

The commercial lithium-ion batteries (LIBs) rely on lithium hexafluorophosphate (LiPF6), which is extremely sensitive to moisture and liable to thermal decomposition. Lithium bis (trifluoro methane sulfonyl) imide (LiTFSI), as a promising electrolyte salt, possesses high thermal stability and excellent moisture tolerance. However, LiTFSI is closely related to severe corrosion of the aluminum (Al) current collector at high voltage. Herein, phosphonate-functionalized imidazolium ionic liquid (PFIL) is developed and utilized as an electrolyte co-solvent to inhibit the oxidative dissolution of the Al current collector. PFIL can suppress Al corrosion by participating in the interface reaction and forming a stable and reliable protective film on the surface of Al foils, as confirmed by X-ray photoelectron spectroscopy. Thanks to the corrosion suppression of the Al current collector, the Li||LiNi0.8Mn0.1Co0.1O2 (NCM811) cells with PFIL-containing electrolytes exhibit better cycling performance and improved capacity retention. This work proposes an effective strategy for the advancement of high-voltage LIBs and contributes to promoting the widespread use of the sulfone imide-based lithium salts.

Vortex-assisted microextraction of melamine from milk samples using green short chain ionic liquid solvents coupled with high performance liquid chromatography determination

Melamine is added illegally to milk and dairy products to increase the amount of apparent protein. This organic nitrogen rich chemical compound has been of great challenge in food safety based on its adverse effect on health. Therefore, the extraction and determination of melamine from milk is necessary. Recently, ionic liquid (ILs) as solvent usage has been noticeable for low melting point, low toxicity, high thermal stability, and high extraction capabilities in a wide range of separation processes. ILs are introduced as organic–inorganic salts and green solvents in microextraction preparation. Therefore, in this study, three ionic liquids ([C6mim][NTF2], [C4mim][NTF2] and [C2mim][NTF2] ILs) were prepared and employed as an extraction solvent in dispersive liquid–liquid microextraction (DLLME) of melamine from milk samples followed by HPLC-UV. The selected ILs were designed using three types of alkyl-imidazolium (as the short organic cations) and bis (tri fluoro methyl sulfonyl) imide as anion and characterized by ATR-FTIR spectra, carbon, and hydrogen Nuclear Magnetic Resonance spectroscopy (H&C-NMR) and energy-dispersive X-ray spectroscopy (EDX). These techniques confirmed the formation of functional groups, the structure of hydrogen and carbon atoms, and various elements of ionic bond between imidazolium and bis (tri fluoro methyl sulfonyl) imide. In the next step, the effect of significant parameters, including type and volume of ILs, adsorption time, pH of the sample solution, and sample volume, were optimized. Under the optimal conditions, the limits of detection (LOD), limits of quantification (LOQ), and linearity range were obtained 63.64 µg kg−1, 210.03 µg kg−1, and 210.03–1000 µg kg−1, respectively, for as prepared [C6mim][NTF2] as the best ILs. Notably, the achieved LOQ was lower than the maximum residue level (MRL) for the melamine residue in dairy products. Eventually, the proposed method was applied to detect melamine in milk samples, and the relative recoveries were examined as 79.6–105.0 %.

Emergent Solvation Behavior in Dual Anion Electrolytes for Zinc Ion Batteries

The need for a diverse range of battery materials for an ever-growing energy storage landscape motivates the development of new chemistries with higher capacities and more stable supply chains. Zn-ion batteries (ZIB) are a particularly attractive option due to the abundance and low cost of Zn and the associated cathode materials that can be used to create a full cell. Extensive work on both aqueous and non-aqueous ZIBs has required an increasingly complex set of electrolytes – in many cases incorporating multiple solvents and/or anions to improve overall system performance. It is becoming clear that understanding and, more importantly, controlling the bulk and interfacial Zn2+ solvation structure is of paramount importance to enable improved electrolyte stability and electrode reversibility. In this work we discover the presence of emergent solvation behavior in non-aqueous Zn electrolytes containing multiple anions, where bis(trifluoromethane sulfonyl) imide (TFSI-) anions that are fully dissociated in isolation are shown to form contact ion pairs with Zn2+ when combined with more strongly coordinating halides (X = Cl-, Br-, I-). This effect is demonstrated using both X-ray absorption and Raman spectroscopies and is further supported by first-principles density functional theory calculations, all of which indicate the dominant solvation structure is Zn(TFSI)mono(X), where “mono” indicates a monodentate TFSI- coordination. These emergent solvation complexes are shown to directly impact the electrochemical response, where a significant fraction of Zn2+ complexes in Cl-containing electrolytes are electrochemically inactive at low overpotentials. Additional redox species are activated for metal deposition as the halide association strength weakens (i.e., Cl- > Br- > I-) indicating that, depending on the relative anion-cation coordination strength, apparent improvements in Coulombic efficiency can come at the cost of lower accessible charge/discharge rates. This work suggests a completely new framework for electrolyte design, where anion chemistry can be used to tune both the bulk speciation and the interfacial solvation structure, enabling profound changes to the electrochemical behavior of the system._______________________The submitted manuscript has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (“Argonne”). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357. The U.S. Government retains for itself, and others acting on its behalf, a paid-up nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan. http://energy.gov/downloads/doe-public-access-plan

Mo-MXene-filled gel polymer electrolyte for high-performance quasi-solid-state zinc metal batteries

The production of MXenes from the MAX phase typically requires hydrofluoric acid etching, a process with significant toxicity and severe environmental implications. Given the wide-ranging applications of MXenes, developing a large-scale, environmentally benign chemical etching process is highly desirable. The goal of this study was to establish selective electrochemical aluminum etching (E-etching) from the Mo3AlC2 MAX phase using an innovative 1-ethyl-3-methylimidazolium bis(trifluoromethyl sulfonyl)imide (EMITFSI) and zinc trifluoromethane sulfonate (Zn(OTF)2) battery electrolyte formulation. The E-etching technique effectively removes the “A” layer from the Mo3AlC2 MAX phase at 60 °C using a TFSI−-based electrolyte. This method demonstrates that the resulting MXene terminal (Tx) contains O and OH groups. Subsequently, the resulting Mo2CTx MXene was embedded into a gel polymer electrolyte (GPE) as an inorganic filler. The Mo2CTx/EMITFSI/Zn(OTF)2/poly(vinylidene fluoride-co-hexafluoropropylene) (PVHF) GPE membrane displayed excellent ionic conductivity, Zn2+ transference number, and galvanostatic Zn plating/stripping compatibility with Zn anodes. Finally, the performance of a zinc-metal battery using a belt-like CaV6O16⋅3H2O cathode was evaluated as a full-cell assembly of CaV6O16⋅3H2O//Mo2CTx/EMITFSI/Zn(OTF)2/PVHF//Zn. This assembly showcased an impressive capacity of 155 mA h g−1, excellent durability (99%), coulombic efficiency approaching 100%, and excellent self-life over 200 h.

Lithium nitrate mediated dynamic formation of solid electrolyte interphase revealed by in situ Fourier transform infrared spectroscopy

A stable solid electrolyte interphase (SEI) plays a vital role in the cyclic stability and Coulombic efficiency (CE) of high-performance lithium-sulfur (Li-S) batteries. It is recognized that the LiNO3 additive can stabilize the SEI of the lithium electrode. However, the exact mechanism of the LiNO3 additive on the SEI of the lithium electrode remains unclear. In this work, we first revealed the mediation mechanism of LiNO3 additive on the dynamic evolution of the SEI on a lithium anode surface through in situ Fourier transform infrared (FTIR) spectroscopy and ab initio molecular dynamics (AIMD) methods. The FTIR and AIMD results directly proved that LiNO3 can accelerate the reduction of lithium bis(trifluoromethyl sulfonyl)imide (LiTFSI) into small molecules rich in Li2O on lithium anode, thus forming a compact and stable SEI after immersing in the LiNO3-containing electrolyte. Moreover, the decomposition of LiTFSI and the solvent is hindered in the subsequent lithium deposition stripping process due to the stable SEI, thus leading to higher Coulombic efficiency and long-term cyclic stability. In addition, an ROSO2Li-like intermediate is also observed during the lithium deposition process while decomposing or diffusing away during the lithium stripping process, maintaining a dynamic formation/dissolution equilibrium of the SEI. This research provides a new insight into understanding the role of LiNO3 in stabilizing lithium electrode.

Irreversible phase back conversion of α‐FAPbI3 driven by lithium‐ion migration in perovskite solar cells

AbstractTypically n‐i‐p structured perovskite solar cells (PSCs) incorporate 2,2′,7,7′‐tetrakis (N,N‐di‐p‐methoxyphenyl amine)‐9,9′‐spirobifluorene (spiro‐OMeTAD) as the hole‐transporting material. Chemical doping of spiro‐OMeTAD involves a lithium bis(trifluoromethyl sulfonyl)imide dopant, causing complex side‐reactions that affect the device performance, which are not fully understood. Here, we investigate the aging‐dependent device performance of widely used formamidinium lead triiodide (FAPbI3)‐based PSCs correlated with lithium‐ion (Li+) migration. Comprehensive analyses reveal that Li+ ions migrate from spiro‐OMeTAD to perovskite, SnO2, and their interfaces to induce the phase‐back conversion of α‐FAPbI3 to δ‐FAPbI3, generation and migration of iodine defects, and de‐doping of spiro‐OMeTAD. The rapid performance drop of FAPbI3‐based PSCs, even aging under dark conditions, is attributed to a series of these processes. This study identifies the hidden side effects of Li+ ion migration in FAPbI3‐based PSCs that can guide further work to maximize the operational stability of PSCs.image

Poly(ionic liquid) blended polyphenylene sulfone ultrafiltration membranes with enhanced surface hydrophilicity and antifouling performance

Membrane fouling is a key challenge in the process of utilizing polyphenylene sulfone(PPSU) ultrafiltration (UF) membranes. To address this issue, an amino-functionalized poly(ionic liquid), poly(1-vinyl-3-propylamine imidazolium bis(trifluoromethane sulfonyl) imide) (PIL[TFSI]), was synthesized via free radical polymerization and incorporated into the prepared UF membranes-based PPSU with nanochannels through nonsolvent induced phase separation method. 1H NMR, ATR-FTIR, XPS and EDS spectra verified the introduction of PIL[TFSI]. The AFM and SEM images showed the membrane possessed a classical asymmetrical structure, featuring a higher surface roughness and dense cortex with pits. The decreased water contact angle by the incorporation of PIL[TFSI] indicates the formation of an improved hydrophilic membrane surface. The hydrophilicity of the blended membranes was enhanced by the increasing incorporation of PIL[TFSI]. Meanwhile, the flux decreased slightly, but the selectivity improved significantly. The PIL[TFSI]/PPSU UF membrane with 5% PIL[TFSI] maintained a flux (275 L/m2 h) and a high rejection for bovine serum albumin (BSA) (>99.9%). Additionally, the blended membrane has a superior removal performance for Congo red (>99.9%) and Evans blue (>99.9%). More importantly, the PIL[TFSI]/PPSU UF membranes present excellent antifouling with an increased flux recovery rate from 60.2% to 91.1%. Furthermore, the existence of hydrogen bonds and π-π interactions between PIL[TFSI] and PPSU is conducive to the good stability and sustained hydrophilicity of blended membrane even after continuous immersion for a month.

Separation of metals from acetic acid leaching solution of spent lithium-ion batteries by ionic liquid system

Spent Li-ion batteries (LIBs) pollute the environment and endanger human health; however, they are valuable mineral resources. Here, we designed an extraction system composed of 0.4 mol/L 2-thenoyltrifluoroacetone (HTTA), 0.4 mol/L trioctylphosphine oxide (TOPO), and ionic liquid (IL) 1-Butyl-3-MethylImidazolium bis (trifluoromethyl sulfonyl) imide to recover valuable metals from spent LIBs. Under the optimum conditions (O/A = 1/1, 25 °C, reaction time 20 min, and pH = 3.65, the pH of the solution does not need to be adjusted), over 99.54% of Co, 99.85% of Mn, and 99.68% of Ni were extracted, while only 2.84% of Li were coextracted. The ultraviolet spectrum analysis showed that the spectral peaks of the stripping solution changed at 266 and 293 nm, indicating that CH3COO– participated in the extraction reaction. Following stripping with sulfuric acid, the pH of the solution was adjusted with 2.0 mol/L NaOH, and approximately 99% of the Al3+ ions were precipitated. Nickel and manganese sulphates were added to the stripping solution. The precursor was prepared using a coprecipitation method. The precursor was then mixed with lithium hydroxide and calcined at 1000 °C for 12 h to obtain LiNi1/3Co1/3Mn1/3O2.

Separation of lithium and nickel using ionic liquids and tributyl phosphate

With the vigorous development of the electronics industry, the consumption of lithium continues to increase, and more lithium needs to be mined to meet the development of the industry. The content of lithium in the solution is much higher than that of minerals, but the interference of impurity ions increases the difficulty of extracting lithium ions. Therefore, we prepared an imidazole-based ionic liquid (1-butyl-3-methylImidazolium bis(trifluoromethyl sulfonyl)imide) (IL) for efficient lithium extraction from aqueous solutions by solvent extraction. Using an extraction consisting of 10% IL, 85% tributyl phosphate (TBP), and 5% dichloroethane and an organic to aqueous phase ratio (O/A) of 2/1, over 64.23% of Li were extracted, and the extraction rate after five-stage extraction could reach more than 96%. The addition of ammonium ions to the solution inhibited the extraction of Ni, and the separation coefficient between lithium and nickel approached infinity, showing a very perfect separation effect. Fourier-transform infrared spectroscopy and slope methods were used to analyze the changes that occurred during extraction, revealing possible extraction mechanisms. In addition, the LiCl solution generated during the preparation of ionic liquids was mixed with the stripping solution, and the battery-grade lithium carbonate was prepared by Na2CO3 precipitation, with a purity of 99.74%. This study provides an efficient and sustainable strategy for recovering lithium from the solution.

High-entropy Electrolyte Enables High Reversibility and Long Lifespan for Magnesium Metal Anodes.

The stable cycling of Mg-metal anodes is limited by several problems, including sluggish electrochemical kinetics and passivation at the Mg surface. In this study, we present a high-entropy electrolyte composed of lithium triflate (LiOTf) and trimethyl phosphate (TMP) co-added to magnesium bis(trifluoromethane sulfonyl)imide (Mg(TFSI)2/1,2-dimethoxyethane (DME) to significantly improve the electrochemical performance of Mg-metal anodes. The as-formed high-entropy Mg2+-2DME-OTf--Li+-DME-TMP solvation structure effectively reduced the Mg2+-DME interaction in comparison with that observed in traditional Mg(TFSI)2/DME electrolytes, thereby preventing the formation of insulating components on the Mg-metal anode and promoting its electrochemical kinetics and cycling stability. Comprehensive characterization revealed that the high-entropy solvation structure brought OTf- and TMP to the surface of the Mg-metal anode and promoted the formation of a Mg3(PO4)2-rich interfacial layer, which is beneficial for enhancing Mg2+ conductivity. Consequently, the Mg-metal anode achieved excellent reversibility with a high Coulombic efficiency of 98% and low voltage hysteresis. This study provides new insights into the design of electrolytes for Mg-metal batteries.

High‐entropy Electrolyte Enables High Reversibility and Long Lifespan for Magnesium Metal Anodes

AbstractThe stable cycling of Mg‐metal anodes is limited by several problems, including sluggish electrochemical kinetics and passivation at the Mg surface. In this study, we present a high‐entropy electrolyte composed of lithium triflate (LiOTf) and trimethyl phosphate (TMP) co‐added to magnesium bis(trifluoromethane sulfonyl)imide (Mg(TFSI)2/1,2‐dimethoxyethane (DME) to significantly improve the electrochemical performance of Mg‐metal anodes. The as‐formed high‐entropy Mg2+‐2DME‐OTf−‐Li+‐DME‐TMP solvation structure effectively reduced the Mg2+‐DME interaction in comparison with that observed in traditional Mg(TFSI)2/DME electrolytes, thereby preventing the formation of insulating components on the Mg‐metal anode and promoting its electrochemical kinetics and cycling stability. Comprehensive characterization revealed that the high‐entropy solvation structure brought OTf− and TMP to the surface of the Mg‐metal anode and promoted the formation of a Mg3(PO4)2‐rich interfacial layer, which is beneficial for enhancing Mg2+ conductivity. Consequently, the Mg‐metal anode achieved excellent reversibility with a high Coulombic efficiency of 98 % and low voltage hysteresis. This study provides new insights into the design of electrolytes for Mg‐metal batteries.

Synthesis and Electrochemical Properties of Electrolytes Based on Phosphonium, Sulfonium and Imidazolium Ionic Liquids for Li-Ion Batteries

This work describes synthesis and characterization of three ionic liquids (IL) with imidazolium, phosphonium or sulfonium cations. These ILs were used as precursors for the preparation of electrolytes by adding various types of lithium salts. Thermal and electrochemical properties of the electrolytes were studied to assess their feasibility for usage in lithium-ion batteries (LIB). Ethylmethylimidazolium phosphonic acid ethyl ester [EtMeIm]+[EtPITE]– with added Li salts showed very low conductivities of about 0.02 mS cm–1 and a rather narrow electrochemical stability window of 4.3 V. Of all the ILs under study, this imidazolium-based IL exhibited the worst thermal properties both neat and with additional Li+ salt. Therefore, using this IL as an electrolyte for LIB is unlikely. Methyl­tributylphosphonium bis(trifluoromethyl sulfonyl) imide [P1444]+[TFSI]– with Li salts had already significantly higher conductivities of 0.4–0.6 mS cm–1 and showed a very wide electrochemical stability window of 7 V. TGA curves of [P1444]+[TFSI]– show excellent thermal stability up to 300 °C. DSC measurements showed semicrystalline behaviour of [P1444]+[TFSI]–; this unfavourable fact was overcome by the addition of Li+ salts. Potential of this IL is very high for the use in LIB. At room temperature, trimethylsulfonium bis(trifluoromethyl sulfonyl) imide [S111]+[TFSI]– is a solid crystalline material, so it was mixed with [P1444]+[TFSI]–. The resulting mixture [P1444]+[S111]+[TFSI]– achieved the highest conductivities of 0.6–1.0 mS cm–1 in comparison to other prepared ILs. The electrochemical stability is also interesting, its ESW value being 5.5 V. Thermal properties are comparable to those of [P1444]+[TFSI]–, but it does not show semicrystalline behaviour. This mixture is a promising electrolyte for LIB.
 Full text English translation is available in the on-line version.

Deep-learning-assisted theoretical insights into the compatibility of environment friendly insulation medium with metal surface of power equipment

Exploring a new generation of eco-friendly gas insulation medium to replace greenhouse gas sulphur hexafluoride (SF6) in power industry is significant for reducing the greenhouse effect and building a low-carbon environment. The gas–solid compatibility of insulation gas with various electrical equipment is also of significance before practical applications. Herein, take a promising SF6 replacing gas trifluoromethyl sulfonyl fluoride (CF3SO2F) for example, one strategy to theoretically evaluate the gas–solid compatibility between insulation gas and the typical solid surfaces of common equipment was raised. Firstly, the active site where the CF3SO2F molecule is prone to interact with other compounds was identified. Secondly, the interaction strength and charge transfer between CF3SO2F and four typical solid surfaces of equipment were studied by first-principles calculations and further analysis was conducted, with SF6 as the control group. Then, the dynamic compatibility of CF3SO2F with solid surfaces was investigated by large-scale molecular dynamics simulations with the aid of deep learning. The results indicate that CF3SO2F has excellent compatibility similar to SF6, especially in the equipment whose contact surface is Cu, CuO, and Al2O3 due to their similar outermost orbital electronic structures. Besides, the dynamic compatibility with pure Al surfaces is poor. Finally, preliminary experimental verifications indicate the validity of the strategy.

Anion Trapping and Ionic Conductivity Enhancement in PEO-Based Composite Polymer–Li7La3Zr2O12 Electrolytes: The Role of the Garnet Li Molar Content

The successful development of all-solid-state batteries will provide solutions for many problems facing current Li-ion batteries, such as high flammability, limited energy density, poor cyclability and low cation transference number. In this quest, the development of high-performance solid-state electrolytes is critical. Composite polymer electrolytes (CPE), comprising ion-conducting (active) inorganic fillers and polymer matrices, have emerged as a promising strategy to yield better conductivity, interfacial stability, and mechanical strength than their single-phase counterparts. Recent experiments indicate that active garnet fillers may enhance the ionic conductivity of CPEs by inducing anion trapping onto their surface. Moreover, substitutions that modify the lithium molar content within the filler were shown to impact this enhancement. However, the molecular underpinning behind this phenomenon is poorly understood, hindering the development of strategies to exploit it optimally. In this study, we use an enhanced hybrid Monte Carlo technique in combination with extensive molecular dynamics simulations to bridge this gap. By focusing on the archetypal CPE formed by Ga-doped Li7–3xGaxLa3Zr2O12 (Gax-LLZO) embedded within a poly(ethylene oxide) (PEO) and lithium bis(trifluoromethane sulfonyl) imide (LiTFSI) polymer matrix, we describe how the dynamic electrostatic trapping of anions leads to overall conductivity enhancement by increasing the lithium transference number and tracer diffusivity in the polymer phase. The extent of this enhancement can be fine-tuned by modulating the Li molar content of LLZO through the doping of Ga. We predict an optimal Li molar content of 5.95, which is lower than the optimal 6.50 reported in the literature for single LLZO.

Molecular coordination-doping engineering enables adjustable ion transport channel based on MOFs-derived UIOLiTF-LLZTO ionic conductor

The inferior ionic conductivity of composite polymer electrolytes (CPEs) caused by grain boundary impedance is one of the critical issues. Adjustable ion transport channels at the molecular level can improve ionic conductivity and lithium-ion transference number. Herein, UIO-66-NSO2CF3Li-Li6.4La3Zr1.4Ta0.6O12 (UIOLiTF-LLZTO) ionic conductor derived from metal-organic frameworks (MOFs) was designed by a covalent grafted strategy of trifluoromethylsulfonyl (TF) group on UIOLiTF and a doping process of LLZTO, showing two new lithium-ion transfer channels driven by molecular coordination-doping engineering. The first channel along UIOLiTF-UIOLiTF was constructed due to the existence of the TF group on UIOLiTF. The second channel along UIOLiTF-LLZTO was constructed due to the direct nanometer contact interface between the opened channel of UIOLiTF and LLZTO. Then TF group acts as “claws” to capture and transfer lithium-ion along the different channels, facilitating improving ionic conductivity and reducing grain boundary impedance. Benefiting from the molecular coordination-doping engineering, UIOLiTF-LLZTO exhibits high ionic conductivity of 9.86 × 10–4 S cm–1, a large lithium-ion transference number of 0.79, and a wide electrochemical window of 5.35 V. Meanwhile, all-solid-state Li|UIOLiTF-LLZTO|LiFePO4 batteries show a high specific capacity of 164.5 mAh g–1 and 155.6 mAh g–1 at 0.2 C and 0.5 C, respectively. Therefore, UIOLiTF-LLZTO demonstrates the way towards the development of MOFs-based CPEs for all-solid-state lithium batteries with high performance.

High-Throughput Screening of Gas Sensor Materials for Decomposition Products of Eco-Friendly Insulation Medium by Machine Learning.

Nowadays, trifluoromethyl sulfonyl fluoride (CF3SO2F) has shown great potential to replace SF6 as an eco-friendly insulation medium in the power industry. In this work, an effective and low-cost design strategy toward ideal gas sensors for the decomposed gas products of CF3SO2F was proposed. The strategy achieved high-throughput screening from a large candidate space based on first-principle calculation and machine learning (ML). The candidate space is made up of different transition metal-embedded graphic carbon nitrides (TM/g-C3N4) owing to their high surface area and subtle electronic structure. Four main noteworthy decomposition gases of CF3SO2F, namely, CF4, SO2, SO2F2, and HF, as well as their initial stable structure on TM/g-C3N4 were determined. The best-performing ML model was established and implemented to predict the interaction strength between gas products and TM/g-C3N4, thus determining the promising gas-sensing materials for target gases with the requirements of interaction strength, recovery time, sensitivity, and selectivity. Further analysis guarantees their stability and reveals the origin of excellent properties as a gas sensor. The high-throughput strategy opens a new avenue of rational and low-cost design principles of desirable gas-sensing materials in an interdisciplinary view.