Bis Trifluoromethane Sulfonimide Lithium Research Articles

4.6V Moisture-Tolerant Electrolytes for Lithium-Ion Batteries.

Commercial LiPF6-based electrolytes face limitations in oxidation stability (4.2 V) and water tolerance (10 ppm). While replacing LiPF6 with lithium bis(trifluoromethane)sulfonimide (LiTFSI) improves water tolerance, it induces Al current collector corrosion above 3.7 V vs. Li/Li+. To address this, lithium cyano(trifluoromethanesulfonyl)imide (LiCTFSI) is proposed here as a non-corrosive, moisture-tolerant alternative. The 2.0 M LiCTFSI/propylene carbonate (PC)-fluoroethylene carbonate (FEC) (7:3 by volume) electrolyte enables LiNi0.8Co0.1Mn0.1O2 (NCM811) cathodes to reach 210 mAh g-1 (2.8-4.6 V) with a cycle life of 500. Full cells with NCM811||graphite (2.0 mAh cm-2) show 77.8% capacity retention after 500 cycles. Even with 2000 ppm moisture in the electrolyte, full cells maintain high cycling stability, reducing the need for costly dry rooms. The electrolyte's low freezing point and high thermal stability enable the operation from -20 °C to 60 °C, delivering 168 mAh g-1 at -20 °C and retaining 94% capacity after 100 cycles at 60 °C. In contrast, cells with commercial LiPF6 electrolyte deliver 71 mAh g-1 at -20°C and retain 52.7% after 100 cycles at 60 °C. This novel salt offers a cost-effective solution for developing robust, high-performance batteries suitable for extreme conditions.

Electrolytes from Alkoxyalkyl-substituted Imidazolium ionic liquids. Synthesis, characterization, properties and cell performance in LiFePO4 half-cells

Electrolytes based on lithium bis(trifluoromethane)sulfonimide (LiTFSI) salt and alkoxyalkyl-substituted imidazolium ionic liquids (ILs) have been studied. We have synthesized three different 1-alkoxyalkyl-3-methylimidazolium TFSI salts with different chain lengths (from 4 to 10 atoms) and with one to three oxygen atoms at position 1- of the imidazole ring. Both the neat ILs as well as the cognate lithium doped electrolytes have been structurally and physicochemically characterized and electrochemically evaluated.Thermal analyses indicate that the glass transition temperature of the electrolytes is displaced to higher temperatures than those of the corresponding neat ILs, being also higher (more positive) upon increasing the number of oxyethylene units. On the other hand, all 1 M LiTFSI doped synthesized electrolytes are thermally stable up to 300 °C.Raman spectroscopy results indicate that the fraction of TFSI anions coordinated to lithium ion decreases on increasing the number of alkoxy units. This finding implies that there is more “free” lithium ion available to link to the ethereal oxygen of the side chain of the imidazolium ring system. This fact influences the ionic conductivity of the neat ILs and their cognate electrolytes.The electrochemical properties —namely high room temperature conductivities as well as wide electrochemical stability windows— indicate that these materials are promising electrolytes for lithium-ion batteries (LIBs). Lithium half-cells using LiFePO4 (LFP) olivine have been assembled in order to assess the electrochemical performance by means of both cyclic voltammetry and galvanostatic charge/discharge tests. Overall, we have found that the electrochemical performance of these cells is better than that reported 1 M LiTFSI [Pyr14][TFSI], a common electrolyte in LIBs. The generated half-cell from the 1-alkoxyalkyl-3-methylimidazolium TFSI salts possess a high capacity up to 145 mAh∙g−1 at a current of 2C.The results reported herein show a striking relationship between structure and properties.

LiF-Rich Alloy-Doped SEI Enabling Ultra-Stable and High-Rate Li Metal Anode.

Li metal is regarded as the "Holy Grail" in the next generation of anode materials due to its high theoretical capacity and low redox potential. However, sluggish Li ions interfacial transport kinetics and uncontrollable Li dendrites growth limit practical application of the energy storage system in high-power device. Herein, separators are modified by the addition of a coating, which spontaneously grafts onto the Li anode interface for in situ lithiation. The resultant alloy possessing of strong electron-donating property promotes the decomposition of lithium bistrifluoromethane sulfonimide in the electrolyte to form a LiF-rich alloy-doped solid electrolyte interface (SEI) layer. High ionic alloy solid solution diffusivity and electric field dispersion modulation accelerate Li ions transport and uniform stripping/plating, resulting in a high-power dendrite-free Li metal anode interface. Surprisingly, the formulated SEI layer achieves an ultra-long cycle life of over 8000 h (20,000 cycles) for symmetric cells at a current density of 10 mA cm-2. It also ensures that the NCM(811)//PP@Au//Li full cell at ultra-high currents (40 C) completes the charging/discharging process in only 68 s to provide high capacity of 151 mAh g-1. The results confirm that this scalable strategy has great development potential in realizing high power dendrite-free Li metal anode.

LiF‐Rich Alloy‐Doped SEI Enabling Ultra‐Stable and High‐Rate Li Metal Anode

AbstractLi metal is regarded as the “Holy Grail” in the next generation of anode materials due to its high theoretical capacity and low redox potential. However, sluggish Li ions interfacial transport kinetics and uncontrollable Li dendrites growth limit practical application of the energy storage system in high‐power device. Herein, separators are modified by the addition of a coating, which spontaneously grafts onto the Li anode interface for in situ lithiation. The resultant alloy possessing of strong electron‐donating property promotes the decomposition of lithium bistrifluoromethane sulfonimide in the electrolyte to form a LiF‐rich alloy‐doped solid electrolyte interface (SEI) layer. High ionic alloy solid solution diffusivity and electric field dispersion modulation accelerate Li ions transport and uniform stripping/plating, resulting in a high‐power dendrite‐free Li metal anode interface. Surprisingly, the formulated SEI layer achieves an ultra‐long cycle life of over 8000 h (20,000 cycles) for symmetric cells at a current density of 10 mA cm−2. It also ensures that the NCM(811)//PP@Au//Li full cell at ultra‐high currents (40 C) completes the charging/discharging process in only 68 s to provide high capacity of 151 mAh g−1. The results confirm that this scalable strategy has great development potential in realizing high power dendrite‐free Li metal anode.

Hydrogen-bond-driven high ionic conductivity, Li+ transfer number, and lithium-interface stability of poly(vinylidene fluoride-hexafluoropropylene)-based solid-state electrolytes

Poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP)-based solid electrolytes with wide electrochemical windows and high thermal stabilities are promising candidates for use in solid-state lithium batteries. However, the practical applications of these electrolytes are currently hindered by their low room-temperature ionic conductivity, limited Li+ transfer number, and the poor stability of the lithium/electrolyte interface. This study proposes a ‘one stone, three birds’ modification method, wherein a small amount of lithium carboxymethylcellulose (CMC-Li) containing rich hydroxyl groups is added to form abundant hydrogen bonds with numerous electronegative C–F groups in the PVDF-HFP molecular chain and lithium bistrifluoromethane sulfonimide (LiTFSI). The strong connections formed between CMC-Li and PVDF-HFP or TFSI− significantly reduced the crystallinity of PVDF-HFP, promoted the dissociation of LiTFSI, and anchored TFSI−, achieving a synchronous improvement in the ionic conductivity and Li+ transfer number. The hydrogen bonds drove the densification of the membrane surface, improving the lithium/electrolyte compatibility at the interface. The ionic conductivity of the modified electrolytes was 5.1 × 10−4 S cm−1 and the Li + transfer number was 0.72 at room temperature. A Li||Li symmetric cell demonstrated stable cycling over 1000 h at 0.2 mA cm−2, where the initial discharge capacity of an all-solid-state cell was enhanced to 165.1 mAh g−1, with steady cycling for 400 runs. Thus, this study provides a novel and effective method for promoting the practical application of solid-state electrolytes.

Add an Extra Layer to Bring Lithium‐Ions Out of Disorder for Longevity of the Solid Full Batteries

AbstractIn the current era of rapid development in the new energy vehicle industry, graphite (Gr) has gained significant attention as the primary anode material for commercial lithium‐ion batteries due to its exceptional reversibility in lithium‐ion insertion/extraction and abundant availability. In this study, a multifunctional ferroelectric Bi12TiO20@C (BIT@C) modified interlayer between Gr and polymer electrolyte (PE) is fabricated. This approach established a channel and homogeneous ion‐conducting network that facilitated lithium‐ion intercalation into Gr at the interface while suppressing erratic lithium precipitation, thereby stabilizing the structure of Gr. The uniform electric field generated by BIT intercalation enabled homogeneous intercalation/deintercalation of lithium ions, effectively preventing the structural collapse of the Gr anode. Assembled LIBs exhibited reduced polarization and enhanced electrochemical properties attributed to facile charge transfer at the interface. The results revealed that Gr│carbon‐BIT@C‐lithium bistrifluoromethane sulfonimide (LiTFSI)/silicon dioxide (SiO2)/poly allyl acetoacetate (PAAA)/poly(vinylidene fluoride‐hexafluoropropylene) (P(VDF‐HFP))/polyvinylidene fluoride (PVDF)│LiFePO4 (LFP) batteries achieved an initial discharge specific capacity of 120.4 mAh g−1 with stable performance over 1200 cycles at 2 C and room temperature (RT), maintaining a Coulombic efficiency of 99.5% after 1200 cycles. The ferroelectric‐modified interface addressed challenges associated with ion transport at the electrode‐electrolyte interface.

Ion transport in composites of binary electrolyte and single ion conductor—A chronoamperometry study

Composite electrolytes for lithium batteries typically combine materials with very different mechanical properties and ionic transport mechanisms and the degree to which these two phases affect each other is not well understood. In this work we used numerical simulations and experiments to investigate the transport in composite electrolytes consisting of polyethylene oxide (PEO) with lithium bis-trifluoromethanesulfonimide (LiTFSI) and Li1.3Al0.3Ti1.7(PO4)3 (LATP) lithium ion conducting glass-ceramic particles. In particular we are interested in how the introduction of a single ion conductor (SIC) changes the salt concentration gradients in the polymer electrolyte (PE) under applied potential. To study this, we performed numerical simulations and chronoamperometry experiments in electrolytes with different arrangements of the SIC and PE phases, i.e. layers and particulate composites. The results show that the particulate composites have the highest concentration gradients and take the longest time to reach steady state current. The best arrangement appears to have a layer of SIC impenetrable to anions in the polymer phase within the electrolyte membrane.

In Situ Species Analysis of a Lithium-Ion Battery Electrolyte Containing LiTFSI and Propylene Carbonate.

In this study, we analyzed the species in a model electrolyte consisting of a lithium salt, lithium bis(trifluoromethane sulfone)imide (LiTFSI), and a widely used neutral solvent propylene carbonate (PC) with excess infrared (IR) spectroscopy, ab initio molecular dynamics simulations (AIMD), and quantum chemical calculations. Complexing species including the charged ones [Li+(PC)4, TFSI-, TFSI-(PC), TFSI-(PC)2, and Li(TFSI)2-] are identified in the electrolyte. Quantum chemical calculations show strong Li+···O(PC) interaction, which suggests that Li+ would transport in the mode of solvation-carriage. However, the interaction energy of each hydrogen bond in TFSI-(PC) is very weak, suggesting that TFSI- would transport in hopping mode. In addition, the concentration dependences of the relative population of the species were also derived, providing a scenario for the dissolving process of the salt in PC. These in-depth studies provide physical insights into the structural and interactive properties of the electrolyte of lithium-ion batteries.

Reprocessable, Highly Transparent Ionic Conductive Elastomers Based on β-Amino Ester Chemistry for Sensing Devices.

Ionic conductive elastomers (ICEs) exhibit a compelling combination of ionic conductivity and elastic properties, rendering them excellent candidates for stretchable electronics, particularly in applications like sensing devices. Despite their appeal, a significant challenge lies in the reprocessing of ICEs without compromising their performance. To address this issue, we propose a strategy that leverages covalent adaptable networks (CANs) for the preparation of ICEs. Specifically, β-amino ester bonds as dynamic motifs are incorporated into a poly(ethylene oxide) network containing lithium bis(trifluoromethane) sulfonimide (LiTFSI) salt. LiTFSI-containing β-amino ester networks (LBAEs) exhibit superb transparency (94%), thermal stability (>280 °C), and modest conductivity (0.00576 mS·cm-1 at 20 °C), and some LBAEs maintain operational capability across a wide temperature range (-20 to 100 °C). By regulating the lithium salt content, the mechanical properties, conductivities, and viscoelastic behaviors can be tailored. Benefiting from these features, LBAEs have been successfully applied in sensing devices for monitoring human motion (e.g., finger bending, swallowing, and clenching). Notably, even after four reprocessing cycles, LBAEs demonstrate structural integrity and maintain their operational capability. This novel approach represents a promising solution to the reprocessing challenges associated with flexible conductive devices, demonstrating the successful integration of CANs and ICEs.

Study on the electrochemical process of Li+/Na+ mixed organic dual-cation battery system

Organic materials have garnered significant attention due to abundant resources, recyclability, and ease of design. However, they are hampered in practical applications by poor conductivity and high solubility. Herein, a lithium metal battery is developed in this work, utilizing the cathode material polyanthraquinonyl sulfide (PAQS) doped with a trace of NaCl. Additionally, the ionic liquid lithium bis-trifluoromethanesulfonimide and lithium metal as the anode. Physicochemical characterizations utilizing Raman spectroscopy and X-photoelectron spectroscopy indicate that both Na+ and Li+ migrate within the cell, forming a dual-cation battery. In addition, the battery displays exceptional rate performance with a capacity of 86 mAh·g−1 at 20 C, which is more than triples the capacity without NaCl, and has excellent cycling performance. Moreover, it retains 98 % capacity after 1000 cycles at 2 C with no significant degradation. This research offers an innovative strategy for developing a high-performance double-cation battery.

A double network facilitated ion-electron conductor for thermoelectric harvesting with high energy density

As a young member of the thermoelectric (TE) family, ionic thermoelectric (i-TE) technology stands out due to its exceptionally high thermopower. However, the intermittent nature of its heat utilization results in a weak power output, thus limiting its practical application. To tackle this issue, combining i-TE with electronic thermoelectric (e-TE) materials that exhibit stable heat-to-electricity conversion capabilities presents itself as a promising solution. With this aim, we introduced interpenetrating network (IPN) structure in the fabrication process of mixed ionic-electronic TE (MIETE) materials. Specifically, we created a double network MIETE converter through the in-situ polymerization of ionic poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPS) on a loosely structured poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS)/lithium bis(trifluoromethane)sulfonimide (LiTFSI) electronic conductive framework. This subsequent construction of the inert network ensures uninterrupted electronic conductivity and boosts density for improved conductivity (σ). The innovative structural design effectively amalgamates thermodiffusion and Seebeck effects, facilitating continuous electricity generation. The resulting hybrid PEDOT:PSS/LiTFSI/PAMPS-LiCl (PLiP) hydrogels exhibit exceptional TE performance, showing a thermopower of 7.86 mV K−1 and σ of 33.3 mS cm−1. It is worth noting that the PLiP hydrogel illustrates a power generation time of over 4 h and an ultra-high energy density of 93.7 J m−2, which exceeds other TE hydrogels based on the thermodiffusion principle.

High ionic conducting lithium fluoride rich solid electrolyte interphase induced by polysulfide for carbon-based dual ion batteries

Carbon-based dual ion batteries (DIBs) promise a high working voltage, ease of production, low cost and low environmental impact, yet they suffer from poor electrochemical performances ascribed predominantly to electrolyte decomposition, consequently impacting the stability of solid electrolyte interphase (SEI) formation in the negative electrode. Herein, we report a facile pre-formation of lithium fluoride (LiF)-rich SEI derived from lithium polysulfide (LiPS) added lithium bis(trifluoromethane)sulfonimide (LiTFSI)-based electrolyte. A pre-formed lithium sulfide (Li2S) as the inner passivation layer effectively facilitates the growth of LiF on carbon anode, which greatly enhances the ionic conductivity of SEI and prevents the formation of Li dendrites. The designed electrolyte consisting of 3.4 M LiTFSI in the mixture of ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) (1:1 by vol.) with the addition of 0.1 M LiPS achieves excellent compatibility with activated carbon, delivered an initial specific capacity of 408 mAh g−1 with coulombic efficiency ∼100% at 1 A g−1 over 150 cycles. With an in-depth analysis of compositions and the distribution of decomposition products at the interface, the critical impact of Li2S on SEI formation is revealed. DIB full cells assembled using the carbon anodes with a pre-formed SEI layer delivered an initial discharge capacity of 57.2 mAh g−1 and average voltage of 4.35 V. The above-mentioned findings shed new light on SEI pre-forming technique for high-performance DIB based on the rational design of electrolytes.

Impact of self-assembled structure on ionic conductivity of an azobenzene-containing electrolyte.

The type of self-assembled structure has a significant impact on the ionic conductivity of block copolymer or liquid crystalline (LC) ion conductors. In this study, we focus on the effect of self-assembled structures on the ionic conductivity of a non-block copolymer, LC ion conductor, which is a mixture of an azobenzene monomer (NbAzo), pentaerythritol tetre(3-mercapropionate) (PETMP), and a lithium salt, lithium bis(trifluoromethane)sulfonimide (LiTFSI). The self-assembled structures and ionic conductivities of ion conductors having different doping ratios of lithium salt to monomer were examined. With the increase in the doping ratio, the self-assembled structure transforms from lamellae (LAM) to double gyroid (GYR). The effect of self-assembled structure on ionic conductivity was analyzed; it was found that the conductivity of the GYR structure was about 3.6 times that of the LAM one, indicating that obtaining the GYR structure is more effective in improving ionic conductivity.

Functional Spiro-OMeTAD-like dopant for Li-Ion-free hole transport layer to develop stable and efficient n-i-p perovskite solar cells

Perovskite solar cells (pero-SCs) containing lithium bis(trifluoromethane)sulfonimide (LiTFSI)-doped Spiro-OMeTAD-based hole transport layers (HTLs) exhibit outstanding power conversion efficiencies (PCEs). However, the dopant LiTFSI likely causes a severe morphology change and induces ion migration, which can also corrode the underlying perovskite film, owing to its hygroscopicity and small ionic radius. In this study, we developed a Spiro-OMeTAD-like organic salt (Spiro-BD-T) with a large-size cation composed of a Spirobifluorene (Spiro) backbone and phenylpyridin-4-amine (BD) as well as an anion composed of TFSI-. The anion in Spiro-BD-T can promote the oxidation of Spiro-OMeTAD and effectively form a weakly bound Spiro-OMeTAD•+TFSI− system. Moreover, the Spiro-OMeTAD-like cation in Spiro-BD-T exhibits good miscibility with Spiro-OMeTAD, excellent hydrophobicity and does not easily migrate, which diminishes the ingress of humidity and eliminates the detrimental Li+ migration. Ultimately, the Spiro-BD-T-doped Spiro-OMeTAD HTL showed a homogeneous and pinhole-free morphology with improved composition stability. The resultant pero-SCs exhibited an excellent PCE of 24.2% with significantly promoted long-term stability.

Two-layer cathode architecture for high-energy density and high-power density solid state batteries

Solid state batteries with high-energy density and high-power density require the development of thick and energy dense cathodes. Structured cathode electrodes with a double-layer configuration were enabled using a freeze tape casting technique. A bottom dense layer was utilized to enhance the energy density whereas a top porous layer with vertically aligned walls was utilized to enhance the power density. The porous structure of the power layer was achieved by ice templating this layer on top of the densified energy layer of the cathode. This configuration was found to better utilize the active material of the cathodes and was optimized using numerical simulation and computer modeling. Cells with Li metal anode and LiNi0.6Mn0.2Co0.2O2 (NMC622) at approximately 5 and 20 mg/cm2 were cycled at 70 °C at different C-rates. Poly(ethylene oxide) (PEO) with lithium bis-trifluoromethanesulfonimide (LiTFSI) was used for the catholyte and the solid-state electrolyte. The structured cathodes exhibited more than double capacity values as well as better Coulombic efficiency compared to non-structured (single-layer) thick cathodes. Synchrotron X-ray tomography and scanning electron microscopy were used to characterize the microstructure of the cathodes.

Two-Layer Structured Cathodes for Solid State Batteries

Designing a robust cathode is one of the major objectives in R&D of lithium-ion batteries. The challenges only get amplified in case of solid state battery cells as the methods for introduction of electrolyte into the cathode structure need to be developed. Ideally, a cathode should support high energy density of a cell which implies necessity for high thickness. This requirement is not trivial to fulfil, both from the standpoint of manufacturing and from the standpoint of overcoming transport limitations in thick cathodes. In this work, inspired by the previous effort on graded porosity cathode design [1], we present a two-layer cathode based on LiNi0.6Mn0.2Co0.2O2 (NMC622). The cathode is built using a densified “energy layer” as a support for the “power layer” in which high porosity and low tortuosity is achieved by the freeze tape casting technique. The distribution of the material in the two layers is guided by numerical simulations based on actual cathode microstructure. The performance of the structured cathodes containing Poly(ethylene oxide) (PEO) with lithium bis-trifluoromethanesulfonimide (LiTFSI) was experimentally investigated in cells containing metallic lithium counter electrode. The structured cathodes showed more than double capacity values and improved Coulombic efficiency compared to uniform cathodes of the same material loading.[1] Kalnaus, S., Livingston, K., Hawley, W.B., Wang, H., Li, J., 2021, “Design and processing for high performance Li ion battery electrodes with double-layer structure J Energy Storage 44 (2021) 103582. Acknowledgments: This research at Oak Ridge National Laboratory (ORNL), managed by UT Battelle, LLC, for the U.S. Department of Energy (DOE) under contract DE-AC05-00OR22725, was sponsored by Laboratory Directed Research and Development Program at ORNL.

Super-stretching and high-performance ionic thermoelectric hydrogels based on carboxylated bacterial cellulose coordination for self-powered sensors

Self-powered sensors that do not require external power sources are crucial for next-generation wearable electronics. As environment-friendly ionic thermoelectric hydrogels can continuously convert the low-grade heat of human skin into electricity, they can be used in intelligent human-computer interaction applications. However, their low thermoelectric output power, cycling stability, and sensitivity limit their practical applications. This paper reports a 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidized carboxylated bacterial cellulose (TOBC) coordination double-network ionic thermoelectric hydrogel with lithium bis(trifluoromethane) sulfonimide (LiTFSI) as an ion provider for thermodiffusion, as LiTFSI exhibits excellent thermoelectric properties with a maximum power output of up to 538 nW at a temperature difference of 20 K. The interactions between the ions and the hydrogel matrix promote the selective transport of conducting ionic ions, producing a high Seebeck coefficient of 11.53 mV K−1. Hydrogen bonding within the polyacrylamide (PAAm) network and interactions within the borate ester bond within the TOBC confer excellent mechanical properties to the hydrogel such that the stress value at a tensile deformation of 3100 % is reaches 0.85 MPa. The combination of the high ionic thermovoltage and excellent mechanical properties ionic thermoelectric hydrogels provides an effective solution for the design and application of self-powered sensors based on hydrogels.

Reversible Modulation of Conductivity in Azobenzene Polyelectrolytes Using Light

Incorporating light-responsive azobenzene into polyelectrolytes couples photoinduced changes in steric interactions and polarity to ionic conductivity. The reversible isomerization of an azobenzene moiety yields a 2–7 times change in the ion conductivity (σtrans > σcis) depending on the polymer composition. These trends cannot be explained by differences in the glass-transition temperatures of the polymers. Instead, UV–vis spectroscopy reveals a bathochromic shift in the π → π* transition of cis-poly(azobenzene) upon adding lithium bis(trifluoromethane)sulfonimide (LiTFSI) salt, suggesting that coordination of the cis isomer with Li+ is responsible for its lower conductivity. In summary, azobenzene is a simple and convenient functional unit to control the conductivity of polymeric materials using light.

Phase Distribution Manipulation through Molecular Interaction Enables Efficient Quasi-2D Perovskite Light-Emitting Diodes

Quasi-two-dimensional (quasi-2D) metal halide perovskites exhibit excellent electroluminescence (EL) performance promising for display and lighting applications, which benefits from the quantum and/or dielectric confinement effects as well as the unique energy-funneling process. However, the inefficient energy transfer caused by the intricate phase distribution with different thick nanoplatelets (n-values), as well as the existence of numerous defects, could deteriorate the EL performance of the resulting perovskite light-emitting diodes (PeLEDs). Here, a multifunctional small molecule, bistrifluoromethanesulfonimide lithium (LiTFSI), was introduced to address the above issues. The strongly electronegative fluorine atoms in LiTFSI form hydrogen bonding interactions with the ammonium heads of organic spacers, which suppress the formation of perovskite ultrathin nanoplatelet phases with small n-values, thus smoothing the energy transfer process. Meanwhile, the Lewis base sulfur oxide groups are capable of effectively passivating the uncoordinated lead ion defects and then reducing nonradiative recombination loss. Eventually, a green emission quasi-2D PeLED with an external quantum efficiency of 21.0% was achieved. This work provides a facile method to boost the performance of quasi-2D PeLEDs.

Anion type-dependent confinement effect on glass transitions of solutions of LiTFSI and LiFSI

We present findings on the effect of nanometer-sized silica-based pores on the glass transition of aqueous solutions of lithium bis(trifluoromethane)sulfonimide (LiTFSI) and lithium difluorosulfimide (LiFSI), respectively. Our experimental results demonstrate a clear dependence of the confinement effect on the anion type, particularly for water-rich solutions, in which the precipitation of crystalized ice under cooling process induces the formation of freeze-concentrated phase confined between pore wall and core ice. As this liquid layer becomes thinner, the freeze-concentrated phase experiences glass transition at increasingly higher temperatures in solutions of LiTFSI. However, differently, for solutions of LiFSI and LiCl, this secondary confinement has a negligible effect on the glass transition of solutions confined wherein. These different behaviors emphasize the obvious difference in the dynamic properties’ response of LiTFSI and LiFSI solutions to spatial confinement and particularly to the presence of the hydrophilic pore wall.