Critical Review of Fluorinated Electrolytes for High-Performance Lithium Metal Batteries

Lithium metal batteries (LMBs), due to their ultra-high energy density, are attracting tremendous attentions. However, their commercial application is severely impeded by poor safety and unsatisfactory cycling stability, which are induced by lithium dendrites, side reactions, and inferior anodic stability. Electrolytes, as the indispensable and necessary components in lithium metal batteries, play a crucial role in regulating the electrochemical performance of LMBs. Recently, the fluorinated electrolytes are widely investigated in high-performance LMBs. Thus, the design strategies of fluorinated electrolytes are thoroughly summarized, including fluorinated salts, fluorinated solvents, and fluorinated additives in LMBs, and insights of the fluorinated components in suppressing lithium dendrites, improving anodic stability and cycling stability. Finally, an outlook with several design strategies and challenges will be proposed for novel fluorinated electrolytes.     

A Dilute Fluorinated Phosphate Electrolyte Enables 4.9 V-Class Potassium Ion Full Batteries

Potassium ion batteries using graphite anode and high-voltage cathodes are considered to be optimizing candidates for large-scale energy storage. However, the lack of suitable electrolytes significantly hinders the development of high-voltage potassium ion batteries. Herein, a dilute (0.8 m ) fluorinated phosphate electrolyte is proposed, which exhibits extraordinary compatibility with both graphite anode and high-voltage cathodes. The phosphate solvent, tris(2,2,2-trifluoroethyl) phosphate (TFP), has weak solvating ability, which not only allows the formation of robust anion-derived solid electrolyte interphase on graphite anode but also effectively suppresses the corrosion of Al current collector at high voltage. Meanwhile, the high oxidative stability of fluorinated TFP solvent enables stable ultrahigh-voltage (4.95 V) cycling of a potassium vanadium fluorophosphate (KVPO₄F) cathode. Using TFP-based electrolyte, the 4.9 V-class potassium ion full cell based on graphite anode and KVPO₄F cathode shows rather remarkable cycling performance with a high capacity retention of 87.2% after 200 cycles. This study provides a route to develop dilute electrolytes for high-voltage potassium ion batteries, by utilizing solvents with both weak solvating ability and high oxidative stability.     

Fluorinated Phosphorene: Electrochemical Synthesis,Atomistic Fluorination,and Enhanced Stability

Phosphorene has attracted great interest due to its unique electronic and optoelectronic properties owing to its tunable direct and moderate band‐gap in association with high carrier mobility. However, its intrinsic instability in air seriously hinders its practical applications, and problems of technical complexity and in‐process degradation exist in currently proposed stabilization strategies. A facile pathway in obtaining and stabilizing phosphorene through a one‐step, ionic liquid‐assisted electrochemical exfoliation and synchronous fluorination process is reported in this study. This strategy enables fluorinated phosphorene (FP) to be discovered and large‐scale, highly selective few‐layer FP (3?6 atomic layers) to be obtained. The synthesized FP is found to exhibit unique morphological and optical characteristics. Possible atomistic fluorination configurations of FP are revealed by core‐level binding energy shift calculations in combination with spectroscopic measurements, and the results indicate that electrolyte concentration significantly modulates the fluorination configurations. Furthermore, FP is found to exhibit enhanced air stability thanks to the antioxidation and antihydration effects of the introduced fluorine adatoms, and demonstrate excellent photothermal stability during a week of air exposure. These findings pave the way toward real applications of phosphorene‐based nanophotonics.     

氟化聚乙烯醇/SiO_2超疏水薄膜的制备及性能

以亲水性高分子聚乙烯醇(PVA)为基体,二氧化硅(SiO_2)纳米颗粒为无机填料,旋涂在玻璃表面后的PVA/SiO_2再经十七氟癸基三甲氧基硅烷(C_(13)H_(13)F_(17)O_3Si,FAS)修饰,制备了具有超疏水性能的PVA/SiO_2-FAS薄膜。考察了PVA与SiO_2复合的比例及FAS修饰对膜疏水性的影响。用傅里叶变换红外光谱、X射线能谱和扫描电子显微镜分别对超疏水表面进行了结构分析和形貌表征,用接触角测量仪观察了水滴在膜表面的润湿性。结果显示,当PVA/SiO_2体积比为1∶5时,氟化PVA/SiO_2膜表面具有较好的超疏水功能,静态接触角可达151.24°,滚动角约为4°。这主要是膜表面含有低表面能氟原子及具有纳米粗糙结构共同作用的结果。     

Electrochemical deposition of polypyrrole–carbon nanotube films using steroid dispersants

Polypyrrole (PPR)–carbon nanotube (CNT) films were prepared by an electrodeposition method, combining PPR electropolymerization and anaphoresis of CNT. PPR polymerization experiments showed advantages of a dopant from the catechol family for the deposition of PPR films at reduced electrode potentials. The method allowed the formation of adherent films on stainless steel substrates. The amphiphilic molecules with steroid-like structures, such as carbenoxolone disodium salt, glycyrrhizic acid, ammonium salt, and sodium taurodeoxycholate, were used for dispersion and charging of CNT. The new dispersing agents showed outstanding dispersion ability. In addition to dispersing properties, electrodeposition experiments revealed film-forming properties of carbenoxolone and ability to form pure carbenoxolone or carbenoxolone–CNT films. The PPR–CNT films formed using carbenoxolone disodium salt, glycyrrhizic acid ammonium salt, and sodium taurodeoxycholate showed diverse microstructural features. The dispersion and deposition mechanisms were discussed.     

Effect of end group of amorphous perfluoro-polymer electrets on electron trapping

Charge trap in amorphous perfluoro-polymer electret is studied, focusing on electron trap site and trap energy. Low-energy inverse photoelectron spectroscopy is adopted to measure solid-state electron affinity (EA) of cyclic transparent optical polymer (CYTOP). EA of CYTOP CTL-S is discovered by compensating the unwanted charge-up effect. Negatively-charged electret materials (polyethylene, ethylene-tetra-fluoro-ethylene, poly-tetra-fluoro-ethylene, and CYTOP) are analyzed by quantum mechanical calculation. Density functional theory with long-range correction is adopted to analyze orbital energies of single molecular systems. Intramolecular distribution of trapped electron and EA are investigated. Calculated electron affinities of CYTOP polymers with different end group are qualitatively in accordance with trapped charge stability measured with thermal stimulated discharge, signifying that electron affinities obtained with the present simulation can be used as an index of amorphous polymer electret.     

碳中和目标背景下包装行业发展的对策

目的 为了应对日益恶化的全球气候变化,并实现碳中和的目标,研究低碳化技术在包装行业的应用成为当下至关重要的任务。为了推动包装行业在碳中和背景下的低碳化转型,有必要对现有的低碳化技术进行分类和梳理。方法 从碳减排和碳移除两方面对包装行业已有的低碳化技术进行了研究。综述当前可降解生物塑料和聚合物单体化学循环技术在包装中的应用,介绍了几种清洁能源以及碳捕捉、碳利用和碳储存技术的发展现状。结论 对包装行业而言,实现碳中和的目标还面临着很多挑战。包装行业在推进碳中和目标时要选取与发展适合的低碳能源和碳中和技术。     

Single‐layered retardation films with negative wavelength dispersion birefringence made from liquid‐crystalline monomers

Organic light‐emitting diode displays have a cathode composed of a layer of highly reflective metal. Reflection of external light from this layer can be suppressed with a broadband quarter‐wave plate. Although various types of quarter‐wave plate retardation films have been prepared by copolymerizing, mixing, or laminating multiple polymers, ideal wavelength dispersion has not been achieved with thin retardation films because of their relatively low birefringence and the complexity of the procedure required manufacturing them. In this study, we developed (i) new liquid‐crystalline monomers with negative wavelength dispersion birefringence that we used to obtain thin, single‐layered retardation films suitable for coating and (ii) retardation films with different molecular alignments. We found that the monomers showed high solubility and high regularity of molecular alignment, with less damage to the substrate and alignment films. We also investigated the wavelength dispersion and thermal stability of the films. We succeeded in developing retardation films that had a homeotropic alignment or a hybrid alignment with negative wavelength dispersion. These alignments can be used to obtain antireflection films with an improved viewing angle for organic light‐emitting diode displays or next‐generation thin displays.     

Selectively fluorinated analogs reveal differential olfactory reception and inactivation of green leaf volatiles in insects

The role of the alkyl terminus of green leaf volatile (GLV) molecules in olfactory reception and inactivation was examined in three diverse insect species: the beet armyworm,Spodoptera exigua (Lepidoptera); the Colorado potato beetle,Leptinotarsa decemlineata (Coleoptera); and the desert locust,Schistocerca gregaria (Orthoptera), using selectively fluorinated analogs of GLVs and electroantennograms (EAGs). When only the magnitude of the depolarization of the EAG is considered (a measure of reception), the order of effectiveness was 1-hexanol (6:OH)=(Z)-3-6:OH > 5,5,6,6,6-pentafluoro-(Z)-3-6:OH =5,5-difluoro-(Z)-3-6:OH 5,5,6,6,6-pentafluoro-6: OH. Percent recovery of the EAG (a measure of inactivation) was greater for the pentafluoro-(Z)-3-6: OH analog than for the difluoro-(Z)-3-6: OH analog. Our results show that the alkyl end of GLV molecules plays an important role not only in reception, but also inactivation processes in insect olfaction. Furthermore, specificities of these two processes may differ.Research conducted by J.C.D. while on an ARS Fellowship at IPO-DLO.