Solvation Structure and Derived Interphase Tuning for High-Voltage Ni-Rich Lithium Metal Batteries with High Safety Using Gem-Difluorinated Ionic Liquid Based Dual-Salt Electrolytes.

Stabilizing electrolytes for high-voltage lithium metal batteries (LMBs) is crucial yet challenging, as they need to ensure stability against both Li anodes and high-voltage cathodes (above 4.5 V versus Li/Li+ ), addressing issues like poor cycling and thermal runaway. Herein, a novel gem-difluorinated skeleton of ionic liquid (IL) is designed and synthesized, and its non-flammable electrolytes successfully overcome aforementioned challenges. By creatively using dual salts, fluorinated ionic liquid and dimethyl carbonate as a co-solvent, the solvation structure of Li+ ions is efficiently controlled through electrostatic and weak interactions that are well unveiled and illuminated via nuclear magnetic resonance spectra. The as-prepared electrolytes exhibit high security avoiding thermal runaway and show excellent compatibility with high-voltage cathodes. Besides, the solvation structure derives a robust and stable F-rich interphase, resulting in high reversibility and Li-dendrite prevention. LiNi0.6 Co0.2 Mn0.2 O2 /Li LMBs (4.5 V) demonstrate excellent long-term stability with a high average Coulombic efficiency (CE) of at least 99.99 % and a good capacity retention of 90.4 % over 300 cycles, even can work at a higher voltage of 4.7 V. Furthermore, the ultrahigh Ni-rich LiNi0.88 Co0.09 Mn0.03 O2 /Li system also delivers excellent electrochemical performance, highlighting the significance of fluorinated IL-based electrolyte design and enhanced interphasial chemistry in improving battery performance.

Sulfur-Containing Bent N-Heteroacenes.

A series of novel sulfur-containing bent N-heteroacenes were constructed and characterized by NMR and UV/Vis spectroscopy, cyclic voltammetry, and single-crystal X-ray diffraction. By introducing sulfur-containing groups (thio, sulfinyl, and sulfonyl) into bent azaacenes, their electronic delocalization was improved and frontier energy levels were modulated. The target products displayed tunable optical and electronic properties through altering the valence of sulfur and fused length of the azaacenes. For the first time, typical products were utilized as organic field effect transistor materials, affording promising results.

Tandem radical cyclization for the construction of 1-difluoroalkylated isoquinolines via Cu catalyzed and visible light-promoted pathways.

A Cu/B2pin2 system promoted cyclization for the synthesis of 1-difluoroalkylated isoquinolines with vinyl isocyanides and bromodifluoroacetic derivatives in moderate to good yields was reported. This method provided a mild and efficient pathway for the construction of diverse 1-difluoroalkylated isoquinolines via a proposed tandem radical cyclization process.

Molecular near-infrared triplet-triplet annihilation upconversion with eigen oxygen immunity.

Molecular triplet-triplet annihilation upconversion often experiences drastic luminescence quenching in the presence of oxygen molecules, posing a significant constraint on practical use in aerated conditions. We present an oxygen-immune near-infrared triplet-triplet annihilation upconversion system utilizing non-organometallic cyanine sensitizers (λex = 808 nm) and chemically synthesized benzo[4,5]thieno[2,3-b][1,2,5]thiadiazolo[3,4-g]quinoxaline dyes with a defined dimer structure as annihilators (λem = 650 nm). This system exhibits ultrastable upconversion under continuous laser irradiance (>480 mins) or extended storage (>7 days) in aerated solutions. Mechanistic investigations reveal rapid triplet-triplet energy transfer from sensitizer to annihilators, accompanied by remarkably low triplet oxygen quenching efficiencies ( η O 2 < 13% for the sensitizer, <3.7% for the annihilator), endowing the bicomponent triplet-triplet annihilation system with inherent oxygen immunity. Our findings unlock the direct and potent utilization of triplet-triplet annihilation upconversion systems in real-world applications, demonstrated by the extended and sensitive nanosensing of peroxynitrite radicals in the liver under in vivo nitrosative stress.

High-Safety Electrolytes with an Anion-Rich Solvation Structure Tuned by Difluorinated Cations for High-Voltage Lithium Metal Batteries.

As next-generation energy storage devices, lithium metal batteries (LMBs) must offer high safety, high-voltage resistance, and a long life span. Electrolyte engineering is a facile strategy to tailor the interfacial chemistry of LMBs. In particular, the solvation structure and derived solid electrolyte interphase (SEI) are crucial for a satisfactory battery performance. Herein, a novel middle-concentrated ionic liquid electrolyte (MCILE) with an anion-rich solvation structure tuned by difluorinated cations is demonstrated to achieve ultrahigh safety, high-voltage stability, and excellent ternary-cathode compatibility. Novel gem-difluorinated cations first synthesized for prestoring fluorine on positively charged species, not only preferentially adsorb in the inner-Helmholtz layers, but also participate in regulating the Li+ solvation structure, resulting in a robust interphase. Moreover, these weak interactions in the Li+ solvation structure including anion-solvent and ionic liquid (IL) cation-solvent pairs are first revealed, which are beneficial for promoting an anion-dominated solvation structure and the desolvation process. Benefiting from the unique anion-rich solvation structure, a stable hetero-SEI structure is obtained. The designed MCILE exhibits compatibility with Li metal anode and the high-voltage ternary cathode at high temperatures (60 °C). This work provides a new approach for regulating the solvation structure and electrode interphase chemistry of LMBs via difluorinated IL cations.

Tandem Radical Cyclization for the Construction of Difluoro-Containing Oxindoles and Quinoline-2,4-diones.

Cu-catalyzed direct difluoromethylation of activated alkenes through a difluoromethyl radical addition/cyclization to afford difluorinated oxindoles and quinoline-2,4-diones has been developed. This method provides convenient access to a variety of oxindoles and quinoline-2,4-diones under mild conditions via a proposed tandem radical cyclization process, while tolerating various functional groups well. Moreover, a facile method to construct diverse difluorinated quinoline-2,4-diones by visible-light photoredox catalysis under mild conditions was presented.

B(C6F5)3-Promoted hydrogenations of N-heterocycles with ammonia borane.

A transition-metal-free method for the B(C6F5)3-promoted hydrogenations of N-heterocycles using ammonia borane under mild reaction conditions has been developed. The reaction affords a broad range of hydrogenated products in moderate to good yields. The enantioselective versions for the corresponding products were also investigated via our approach, showing good feasibility.