Mechanically and Thermally Stable Cathode Electrolyte Interphase Enables High-temperature, High-voltage Li||LiCoO2 Batteries.

The development of high-energy-density Li||LiCoO2 batteries is severely limited by the instability of cathode electrolyte interphase (CEI) at high voltage and high temperature. Here we propose a mechanically and thermally stable CEI by electrolyte designing for achieving the exceptional performance of Li||LiCoO2 batteries at 4.6 V and 70 °C. 2,4,6-tris(3,4,5-trifluorophenyl)boroxin (TTFPB) as the additive could preferentially enter into the first shell structure of PF6 - solvation and be decomposed on LiCoO2 surface at low oxidation potential to generate a LiBx Oy -rich/LiF-rich CEI. The LiBx Oy surface layer effectively maintained the integrity of CEI and provided excellent mechanical and thermal stability while abundant LiF in CEI further improved the thermal stability and homogeneity of CEI. Such CEI drastically alleviated the crack and regeneration of CEI and irreversible phase transformation of the cathode. As expected, the Li||LiCoO2 batteries with the tailored CEI achieved 91.9 % and 74.0 % capacity retention after 200 and 150 cycles at 4.6 and 4.7 V, respectively. Moreover, such batteries also delivered an unprecedented high-temperature performance with 73.6 % capacity retention after 100 cycles at 70 °C and 4.6 V.

Constructing Highly Li+ Conductive Electrode Electrolyte Interphases for 4.6 V Li||LiCoO2 Batteries via Electrolyte Additive Engineering.

To improve voltage is considered to effectively address the energy-density question of Li||LiCoO2 batteries. However, it is restricted by the instability of electrode electrolyte interphases in carbonate electrolytes, which mainly originates from Li dendrite growth and structural instability of LiCoO2 at high voltage. Herein, an electrolyte additive strategy is proposed for constructing efficient LiNx Oy -contained cathode electrolyte interphase for 4.6 V LiCoO2 and LiF-rich solid electrolyte interphase for Li anode to enhance the stability of Li||LiCoO2 battery using 4-nitrophthalic anhydride as the additive. As expected, the Li||LiCoO2 battery can stably operate up to 4.6 V, with a high specific capacity of 216.9 mAh g-1 during the 1st cycle and a capacity retention of 167.1 mAh g-1 after 200 cycles at 0.3 C. This work provides an available strategy to realize the application of high-voltage Li||LiCoO2 battery.

Highly Oxidation-Resistant Electrolyte for 4.7†V Sodium Metal Batteries Enabled by Anion/Cation Solvation Engineering.

Sodium metal batteries (SMBs) are considered as promising battery system due to abundant Na sources. However, poor compatibility between electrolyte and cathode severely impedes its development. Herein, we proposed an anion/cation solvation strategy for realizing 4.7 V resistant SMBs electrolyte with NaClO4 and trimethoxy(pentafluorophenyl)silane (TPFS) as dual additives (DA). The ClO4 - can rapidly transfer to the cathode surface and strongly coordinate with Na+ to form stable polymer-like chains with solvents. Meanwhile, TPFS can preferentially enter into the PF6 - anion solvation sheath for reducing PF6 -solvent interaction and effectively scavenge adverse electrolyte species for protecting electrode electrolyte interphases. Thus, such electrolyte elevates the oxidative stability of carbonate electrolytes from 3.77 to 4.75 V, and enables Na||Na3 V2 (PO4 )2 O2 F (NVPF) battery with a capacity retention of 93 % and an average Coulombic efficiency (CE) of 99.6 % after 500 cycles at 4.7 V.

Formation of NaF-Rich Solid Electrolyte Interphase on Na Anode through Additive-Induced Anion-Enriched Structure of Na+ Solvation.

High-capacity sodium (Na) anodes suffer from dendrite growth due to the high reactivity, which can be overcome through inducing a stable NaF-rich solid electrolyte interphase (SEI). Herein, we propose an additive strategy for realizing the anion-enriched structure of Na+ solvation to obtain a NaF-rich SEI. The electron-withdrawing acetyl group in 4-acetylpyridine (4-APD) increases the coordination number of PF6 - in the Na+ solvation sheath to facilitate PF6 - to decompose into NaF. Thus, the NaF-rich SEI with high mechanical stability and interfacial energy is formed to repress the growth of Na dendrites. With the 4-APD-contained electrolyte, the symmetric Na||Na cells show excellent cycling performance over 360 h at 1.0 mA cm-2 . Meanwhile, excellent stability is also achieved for Na||Na3 V2 (PO4 )2 O2 F full cells with high Coulombic efficiency (97 %) and capacity retention (91 %) after 200 cycles.

Separator-Wetted, Acid- and Water-Scavenged Electrolyte with Optimized Li-Ion Solvation to Form Dual Efficient Electrode Electrolyte Interphases via Hexa-Functional Additive.

The performance of lithium metal batteries (LMBs) is determined by many factors from the bulk electrolyte to the electrode-electrolyte interphases, which are crucially affected by electrolyte additives. Herein, the authors develop the heptafluorobutyrylimidazole (HFBMZ) as a hexa-functional additive to inhibit the dendrite growth on the surface of lithium (Li) anode, and then improve the cycling performance and rate capabilities of Li||LiNi0.6 Co0.2 Mn0.2 O2 (NCM622). The HFBMZ can remove the trace H2 O and HF from the electrolyte, reducing the by-products on the surface of solid electrolyte interphase (SEI) and inhibiting the dissolution of metal ions from NCM622. Also, the HFBMZ can enhance the wettability of the separator to promote uniform Li deposition. HFBMZ can make Li+ easy to be desolvated, resulting in the increase of Li+ flux on Li anode surface. Moreover, the HFBMZ can optimize the composition and structure of SEI. Therefore, the Li||Li symmetrical cells with 1 wt% HFBMZ-contained electrolyte can achieve stable cycling for more than 1200 h at 0.5 mA cm-2 . In addition, the capacity retention rate of the Li||NCM622 can reach 92% after 150 cycles at 100 mA g-1 .

Additive-Assisted Hydrophobic Li+ -Solvated Structure for Stabilizing Dual Electrode Electrolyte Interphases through Suppressing LiPF6 Hydrolysis.

Lithium-metal batteries have attracted much attention due to their high energy density. However, the hydrolysis of LiPF6 leads to uncontrollable Li dendrites growth and fast capacity fading. Herein, a hydrophobic Li+ -solvated structure is designed by inducing the hexafluoroisopropyl acrylate into the electrolyte system. Due to the alkene groups and non-polar perfluorocarbon (-CF2 CF2 CF3 ) chain, a hydrophobic surface around Li-ion solvated aggregates can be obtained to protect the LiPF6 against the attack from trace H2 O. Moreover, the additive could also help to form an organic solid electrolyte interphase with rich polar C-F bonds, which can capture Li ions to restrain the dendrite growth. Therefore, the Li||Li symmetric cells show a stable cycling performance up to 500 h at a current density of 1 mA cm-2 . The Li||LiNi0.6 Co0.2 Mn0.2 O2 cells show good cycling stability, exhibiting a specific capacity of 111 mAh g-1 at 1 C with a capacity retention of 74 % after 200 cycles.

Scalable and Flexible Electrospun Film for Daytime Subambient Radiative Cooling.

Daytime radiative cooling materials reflect solar light and dissipate heat directly to outer space without any energy consumption, and thus, have attracted much attention due to the potential applications in many fields. Recently, elaborately designed photonic crystal and metamaterials have been reported for daytime subambient radiative cooling. However, such materials and structures have the drawbacks of complex shapes, inflexibility, high cost, and limitation in scaling up. It is also extremely difficult to apply such materials to buildings, vehicles, and other objects having complex surfaces. Here, a scalable and flexible hybrid film for daytime subambient radiative cooling was fabricated by a facile electrospinning method. The hybrid film consists of poly(vinylidene fluoride)/alumina (PVDF/Al2O3) fibers with diameters of 0.5-2.5 µm. Owing to the efficient scattering by fibers and Al2O3 nanoparticles, the hybrid film exhibits an extremely high average solar reflectance of 0.97. A high average atmospheric window emittance of 0.95 is simultaneously achieved due to the molecular vibrations of PVDF and the phonon polariton resonance of Al2O3 nanoparticles. The composite film delivers an average net radiative cooling power of 82.7 W/m2, and a temperature drop of up to 4.0 °C under direct sunlight. The hybrid film exhibits remarkable radiative cooling performance under different weather conditions including sunny, cloudy, overcast, and rainy. It can be used not only for cooling buildings and vehicles but also for delaying the melting of glaciers. This work demonstrates a promising method for scale-up production of the radiative cooling film with high performance.

Roadmap on Ionic Liquid Electrolytes for Energy Storage Devices.

Ionic liquids are considered to be promising electrolyte solvents or additives for rechargeable batteries (i. e., lithium-ion batteries, sodium-ion batteries, lithium-sulfur batteries, aluminum-ion batteries, etc.) and supercapacitors. This is related with the superior physical and electrochemical properties of ionic liquids, which can influence the performance of rechargeable batteries. Therefore, it is necessary to write a roadmap on ionic liquids for rechargeable batteries. In this roadmap, some progress, critical techniques, opportunities and challenges of ionic liquid electrolytes for various batteries and supercapacitors are pointed out. Especially, properties and roles of ionic liquids should be considered in energy storage. Ionic liquids can be used as electrolyte salts, electrolyte additives, and solvents. For optimizing ionic liquid-based electrolytes for energy storage, their applications in various energy storage devices should be considered by combing native chemical/physical properties and their roles. We expect that this roadmap will give a useful guidance in directing future research in ionic liquid electrolytes for rechargeable batteries and supercapacitors.

Electrolytes for Lithium- and Sodium-Metal Batteries.

High-energy-density batteries have attracted significant attention due to the huge demand in electric transportation in future. Metal-based batteries, especially lithium metal batteries (LMBs) and sodium metal batteries (SMBs), have been hot research topics nowadays. The uncontrolled growth of metal dendrites has retarded the development of LMBs and SMBs. Various electrolytes have been explored to meet the demand of high-performance metal-based batteries, such as additives-contained electrolytes, polymer electrolytes, and solid-state electrolytes. To guide the development of electrolytes in LMBs and SMBs, we organize this roadmap to give out the status of present research and future challenges in this field. We also hope that the readers can get the knowledge and ideas from this roadmap.

Magnetic resonance imaging and photothermal conversion properties of Gd-C nanocomposites for interstitial lymphography.

Dual-functional agents for magnetic resonance imaging (MRI) guided photothermal therapy (PTT) of lymph cancer are highly desired. Signal enhancement, selectivity between lymphatic nodes/vessels and blood vessels, and photothermal conversion property are the criteria for such dual-functional agent. In the current work, we demonstrated the potential of Gd-C nanocomposites as dual-functional agents for the MRI and PTT of lymph node cancer. Gd-C nanocomposites were synthesized via a hydrothermal carbonization approach with gadolinium chloride as Gd source and citric acid (CA) as C source. The particle size of the nanocomposites ranges from 40 to 100 nm which is smaller than the intercellular space of lymphatic vessels but much larger than that of the blood vessels. The nanocomposites were successfully applied to the MRI of cervical lymph nodes of rabbits. The signal enhancement of the lymph nodes reached the maximum value of 434% at 10 min after injection, without displaying any blood vessel. The Gd-C nanocomposites also exhibited strong photothermal conversion effect. Under the illumination of an 808 nm laser, the aqueous suspension containing 1.0 wt % Gd-C nanocomposites gave a maximum temperature rise of 28.2 °C and a light utilization efficiency of 30.4%. The results indicate that Gd-C nanocomposites have significant potential in MRI guided PTT of lymph cancer.

Broadband absorption and enhanced photothermal conversion property of octopod-like Ag@Ag2S core@shell structures with gradually varying shell thickness.

Photothermal conversion materials have promising applications in many fields and therefore they have attracted tremendous attention. However, the multi-functionalization of a single nanostructure to meet the requirements of multiple photothermal applications is still a challenge. The difficulty is that most nanostructures have specific absoprtion band and are not flexible to different demands. In the current work, we reported the synthesis and multi-band photothermal conversion of Ag@Ag2S core@shell structures with gradually varying shell thickness. We synthesized the core@shell structures through the sulfidation of Ag nanocubes by taking the advantage of their spatially different reactivity. The resulting core@shell structures show an octopod-like mopgorlogy with a Ag2S bulge sitting at each corner of the Ag nanocubes. The thickness of the Ag2S shell gradually increases from the central surface towards the corners of the structure. The synthesized core@shell structures show a broad band absorption spectrum from 300 to 1100 nm. Enhanced photothermal conversion effect is observed under the illuminations of 635, 808, and 1064 nm lasers. The results indicate that the octopod-like Ag@Ag2S core@shell structures have characteristics of multi-band photothermal conversion. The current work might provide a guidance for the design and synthesis of multifunctional photothermal conversion materials.

Optical Absorption and Photo-Thermal Conversion Properties of CuO/H2O Nanofluids.

Stable CuO/H2O nanofluids were synthesized in a wet chemical method. Optical absorption property of CuO/H2O nanofluids was investigated with hemispheric transmission spectrum in the wavelength range from 200 nm to 2500 nm. Photo-thermal conversion property of the CuO/H2O nanofluids was studied with an evaluation system equipped with an AUT-FSL semiconductor/solid state laser. The results indicate that CuO/H2O nanofluids have strong absorption in visible light region where water has little absorption. Under the irradiation of laser beam with a wavelength of 635 nm and a power of 0.015 W, the temperature of CuO/H2O nanofluids with 1.0% mass fraction increased by 5.6 °C within 40 seconds. Furthermore, the temperature elevation of CuO/H2O nanofluids was proved to increase with increasing mass fractions. On the contrast, water showed little temperature elevation under the identical conditions. The present work shows that the CuO/H2O nanofluids have high potential in the application as working fluids for solar utilization purpose.

Photo-Thermal Conversion of Copper Sulfide Hollow Structures with Different Shape and Thickness.

In the current paper, we report the synthesis of spherical and cubic copper sulfide hollow structures, as well as the influence of shape and thickness on the photo-thermal conversion of the as-synthesized products. Copper sulfide hollow structures of different thickness were synthesized base on a sacrificial template strategy using spherical and cubic Cu2O precursors as templates. Optical absorption of the as-synthesized products was investigated with UV-Vis spectrometer. Photo-thermal conversion property was studied with a lab-made evaluation system equipped with an AUT-FSL semiconductor/solid state laser. The results indicate that the as-prepared products exhibited significant absorption in visible light regions. Under the irradiation of laser beam with a wavelength at 635 nm and a power of 0.015 W, the temperature elevations of the aqueous suspensions containing 0.24% mass fraction of spherical and cubic copper sulfide hollow structures were measured to be 5 °C and 6 °C within 60 seconds, respectively. On the contrast, water showed little temperature elevation under the same conditions.

Oil sorbents with high sorption capacity, oil/water selectivity and reusability for oil spill cleanup.

A sorbent for oil spill cleanup was prepared through a novel strategy by treating polyurethane sponges with silica sol and gasoline successively. The oil sorption capacity, oil/water selectivity, reusability and sorption mechanism of prepared sorbent were studied. The results showed that the prepared sorbent exhibited high sorption capacity and excellent oil/water selectivity. 1g of the prepared sorbent could adsorb more than 100 g of motor oil, while it only picks up less than 0.1 g of water from an oil-water interface under both static and dynamic conditions. More than 70% of the sorption capacity remained after 15 successive sorption-squeezing cycles, which suggests an extraordinary high reusability. The prepared sorbent is a better alternative of the commercial polypropylene sorbent which are being used nowadays.

Thermal properties of carbon black aqueous nanofluids for solar absorption.

In this article, carbon black nanofluids were prepared by dispersing the pretreated carbon black powder into distilled water. The size and morphology of the nanoparticles were explored. The photothermal properties, optical properties, rheological behaviors, and thermal conductivities of the nanofluids were also investigated. The results showed that the nanofluids of high-volume fraction had better photothermal properties. Both carbon black powder and nanofluids had good absorption in the whole wavelength ranging from 200 to 2,500 nm. The nanofluids exhibited a shear thinning behavior. The shear viscosity increased with the increasing volume fraction and decreased with the increasing temperature at the same shear rate. The thermal conductivity of carbon black nanofluids increased with the increase of volume fraction and temperature. Carbon black nanofluids had good absorption ability of solar energy and can effectively enhance the solar absorption efficiency.

Preparation and thermal conductivity of CuO nanofluid via a wet chemical method.

In this article, a wet chemical method was developed to prepare stable CuO nanofluids. The influences of synthesis parameters, such as kinds and amounts of copper salts, reaction time, were studied. The thermal conductivities of CuO nanofluids were also investigated. The results showed that different copper salts resulted in different particle morphology. The concentration of copper acetate and reaction time affected the size and shape of clusters of primary nanoparticles. Nanofluids with different microstructures could be obtained by changing the synthesis parameters. The thermal conductivities of CuO nanofluids increased with the increase of particle loading.

Evaluation of electrospun polyvinyl chloride/polystyrene fibers as sorbent materials for oil spill cleanup.

A novel, high-capacity oil sorbent consisting of polyvinyl chloride (PVC)/polystyrene (PS) fiber was prepared by an electrospinning process. The sorption capacity, oil/water selectivity, and sorption mechanism of the PVC/PS sorbent were studied. The results showed that the sorption capacities of the PVC/PS sorbent for motor oil, peanut oil, diesel, and ethylene glycol were 146, 119, 38, and 81 g/g, respectively. It was about 5-9 times that of a commercial polypropylene (PP) sorbent. The PVC/PS sorbent also had excellent oil/water selectivity (about 1000 times) and high buoyancy in the cleanup of oil over water. The SEM analysis indicated that voids among fibers were the key for the high capacity. The electrospun PVC/PS sorbent is a better alternative to the widely used PP sorbent for oil spill cleanup.

Novel synthesis of bismuth tungstate hollow nanospheres in water-ethanol mixed solvent.

Bi(2)WO(6) hollow nanospheres were prepared in a sacrificial templates approach by converting the reaction medium from aqueous solution to a mixed solvent of water and ethanol.

Fast synthesis, formation mechanism, and control of shell thickness of CuS hollow spheres.

CuS hollow spheres were quickly synthesized under mild conditions with spherical aggregates of Cu(2)O nanoparticles as sacrificial templates. The mechanism involved in the synthesis process has been studied using transmission electron microscopy, high-resolution transmission electron microscopy, scanning electron microscopy, X-ray diffraction, thermal gravimetry, and Fourier transform infrared spectra. The results show that the formation of loose aggregates of Cu(2)O nanoparticles is the key to the fast synthesis of hollow spheres at low temperature. The thickness of the shell can be controlled easily by adjusting the aggregation degree of the Cu(2)O nanoparticles.