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Polymer solid-state lithium batteries (SSLB) are regarded as a promising energy storage technology to meet growing demand due to their high energy density and safety. Ion conductivity, interface stability and battery assembly process are still the main challenges to hurdle the commercialization of SSLB. As the main component of SSLB, poly(1,3-dioxolane) (PDOL)-based solid polymer electrolytes polymerized in-situ are becoming a promising candidate solid electrolyte, for their high ion conductivity at room temperature, good battery electrochemical performances, and simple assembly process. This review analyzes opportunities and challenges of PDOL electrolytes toward practical application for polymer SSLB. The focuses include exploring the polymerization mechanism of DOL, the performance of PDOL composite electrolytes, and the application of PDOL. Furthermore, we provide a perspective on future research directions that need to be emphasized for commercialization of PDOL-based electrolytes in SSLB. The exploration of these schemes facilitates a comprehensive and profound understanding of PDOL-based polymer electrolyte and provides new research ideas to boost them toward practical application in solid-state batteries.

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Earth abundant transition metal oxide (EATMO)-based bifunctional catalysts for overall water splitting are highly desirable, but their performance is far from satisfactory due to low intrinsic activities of EATMOs toward electrocatalysis of both oxygen and hydrogen evolution reactions and poor electron transfer and transport capabilities. A three-dimensional (3-D) Ni-foam-supported NiCoO2@Co3O4 nanowire-on-nanosheet heterostructured array with rich oxygen vacancies has been synthesized, showing OER activity superior to most reported catalysts and even much higher than Ru and Ir-based ones and HER activity among the highest reported for non-noble-metal-based catalysts. The excellent activities are ascribed to the highly dense, ultrathin nanowire arrays epitaxially grown on an interconnected layered nanosheet array greatly facilitating electron transfer and providing numerous electrochemically accessible active sites and the high content of oxygen vacancies on nanowires greatly promoting OER and HER. When adopted as bifunctional electrodes for overall water splitting, this heterostructure shows an overvoltage (at 10 mA cm-2) lower than most reported electrolyzers and high stability. This work not only creates a 3-D EATMO-based integrated heterostructure as a low-cost, highly efficient bifunctional catalytic electrode for water splitting, but also provides a novel strategy to use unique heteronanostructures with rich surface defects for synergistically enhancing electrocatalytic activities.

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Solid electrolytes with both interface compatibility and efficient ion transport have been an urgent technical requirement for the practical application of solid-state lithium batteries. Herein, a multifuctional poly(1,3-dioxolane) (PDOL) electrolyte combining the gradient structure from the solid state to the gel state with the Li6.4La3Zr1.4Ta0.6O12 (LLZTO) interfacial modification layer was designed, in which the "solid-to-gel" gradient structure greatly improved the electrode/electrolyte interface compatibility and ion transport, while the solid PDOL and LLZTO layers effectively improved the interface stability of the electrolyte/lithium anode and the inhibition of the lithium dendrites via their high mechanical strength and forming a stable interfacial SEI composite film. This gradient PDOL/LLZTO composite electrolyte possesses a high ionic conductivity of 2.9 × 10-4 S/cm with a wide electrochemical window up to 4.9 V vs Li/Li+. Compared with the pristine PDOL electrolyte and PDOL solid electrolyte membrane coated with a layer of LLZTO, the gradient PDOL/LLZTO composite electrolyte shows better electrode/electrolyte interfacial compatibility, lower interface impedance, and smaller polarization, resulting in enhanced rate and cycle performances. The NCM622/PDOL-LLZTO/Li battery can be stably cycled 200 times at 0.3C and 25 °C. This multifunctional gradient structure design will promote the development of high-performance solid electrolytes and is expected to be widely used in solid-state lithium batteries.

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High interface impedance, slow ion transmission, and easy growth of lithium dendrites in solid-state lithium battery are main obstacles to its development and application. Good interface combination and compatibility between electrolyte and electrodes is an important way to solve these problems. In this work, we successfully combined a high ionic conductive polymerized 1,3-dioxolane (PDOL) solid-state electrolyte and a PDOL gel-state electrolyte to form a rigid-flexible composite structural electrolyte and realized the gelation modification of solid electrolyte/electrode interface. This "PDOL SE + PDOL Gel" composite structure not only improves the electrode/electrolyte interfacial contact, reduces the interfacial impedance, but also inhibits the growth of lithium dendrites in the interface between lithium anode and electrolyte by forming an uniform Li-Zr-O and LiF composite protection layer. This composite electrolyte has high ionic conductivity of 5.96 × 10-4 S/cm and wide electrochemical stability window of 5.0 V. The Li/PDOL SE + PDOL Gel/Li cells can be cycled stably for nearly 400 h at a current density of 1.0 mA/cm2. The assembled LiCoO2/PDOL SE + PDOL Gel/Li cells can be cycled for 250 cycles at 0.5 C with a capacity retention of 80%. This PDOL solid/gel composite electrolyte shows high promising commercial application prospect due to its high security performance, excellent interfacial properties and dendrite inhibition ability.

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Pd-based catalysts with maximized exposure of active sites, ultrafast electron transport, and cocatalyst-promoted intrinsic activity are highly desirable for the formic acid oxidation reaction (FAOR), but their fabrication presents a formidable challenge. For the first time, dynamic self-assembly of adenine has been utilized for growth of ultrasmall, highly dispersed, and clean Pd NPs on pristine graphene. The obtained nanohybrid shows remarkably enhanced FAOR catalytic activity and durability compared to Pd NPs directly grown on pristine graphene and commercial Pd/C. The activity is also among the highest for Pd-based catalysts. The excellent catalytic performance is due to well-dispersed, ultrasmall, and clean Pd NPs intimately grown on pristine graphene offering numerous electrochemically accessible active sites and preserving high intrinsic catalytic activity of Pd, great cocatalytic effect of pristine graphene enhancing CO tolerance and intrinsic activity of Pd, and robust attachment of Pd with high CO tolerance on graphene providing high durability. This study develops a facile, mild, and economical strategy to create pristine graphene supported clean Pd NPs with outstanding FAOR catalytic performance, and also sheds light on the mechanism of dynamically self-assembled adenine-mediated synthesis, which is extendable to fabricate other nanohybrids.

Asunto(s)

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Highly conductive cocatalysts with great promotion effects are critical for the development of pristine graphene supported Pt-based catalysts for the methanol oxidation reaction (MOR) in direct methanol fuel cells (DMFCs). However, identification of these cocatalysts and controlled fabrication of Pt/cocatalyst/graphene hybrids with superior catalytic performance present great challenges. For the first time, pristine graphene supported N-rich carbon (NC) has been controllably fabricated via ionic-liquid-based in situ self-assembly for in situ growth of small and uniformly dispersed Pt NP chains to improve the MOR catalytic activity. It is discovered that the NC serves simultaneously as a linker to facilitate in situ nucleation of Pt, a stabilizer to restrict its growth and aggregation, and a structure-directing agent to induce the formation of Pt NP chains. The obtained nanohybrid shows a much higher forward peak current density than commercial Pt/C and most reported noncovalently functionalized carbon (NFC) supported Pt catalysts, a lower onset potential than almost all commercial Pt/C and NFC supported Pt, and greatly enhanced durability compared to graphene supported Pt NPs and commercial Pt/C. The superior catalytic performance is ascribed to the uniformly dispersed, small-diameter, and short Pt NP chains supported on highly conductive G@NC providing high ECSA and improved CO tolerance and the NC with high content of graphitic N greatly enhancing the intrinsic activity and CO tolerance of Pt and offering numerous binding sites for robustly attaching Pt. This work not only identifies and controllably fabricates a novel cocatalyst to significantly promote the catalytic activity of pristine graphene supported Pt but provides a facile and economical strategy for the controlled synthesis of high-performance integrated catalysts for the MOR in DMFCs.

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Poor room-temperature ionic conductivity and lithium dendrite formation are the main issues of solid electrolytes. In this work, rod-shaped alumina incorporation and graphite coating were simultaneously applied to poly (propylene carbonate) (PPC)-based polymer solid electrolytes (Wang et al., 2018). The obtained alumina modified solid electrolyte membrane (Al-SE) achieves a high ionic conductivity of 3.48 × 10-4 S/cm at room temperature with a wide electrochemical window of 4.6 V. The assembled NCM622/Al-SE/Li solid-state battery exhibits initial discharge capacities of 198.2 mAh/g and 177.5 mAh/g at the current density of 0.1 C and 0.5 C, with the remaining capacities of 165.8 mAh/g and 161.3 mAh/g after 100 cycles respectively. The rod-shaped structure of Al2O3 provides fast transport channels for lithium ions and its Lewis acidity promotes the dissociation of lithium salts and release of free lithium ions. The lithiophilic Al2O3 and Graphite form intimate contact with metallic Li and create fast Li+ conductive layers of Li-Al-O layer and LiC6 layer, thus facilitating the uniform deposition of Li and inhibiting Li dendrite formation during long-term cycling. This kind of composite Al-SE is expected to provide a promising alternative for practical application in solid electrolytes.

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Poor interface stability is a crucial problem hindering the electrochemical performance of solid-state lithium batteries. In this work, a novel approach for interface stability was proposed to integrate the cathode/solid electrolyte by forming an electrolyte buffer layer on the rough surface of the cathode and coating a layer of graphite on the side of the electrolyte facing the lithium anode. This hybrid structure significantly improves the integration and the interface stability of the electrode/electrolyte. The interfacial resistance was dramatically reduced, the stability of the plating/stripping of Li metal was enhanced, and the growth of lithium dendrites was also inhibited due to the formation of the LiC6 transition layer. The obtained solid-state lithium battery shows enhanced rate performance at room temperature from 0.5 to 4 C and stable cycling performance at 1 C with a retention capacity of 100 mAh g-1 after 200 cycles. This integrated electrode/electrolyte design approach is expected to be widely used to improve interfacial stability and room-temperature electrochemical performance of solid-state batteries.

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Electrodes with high conductivity and flexibility are crucial to the development of flexible lithium-ion batteries. In this study, three-dimensional (3D) LiFePO4 and Li4Ti5O12 fiber membrane materials were prepared through electrospinning and directly used as self-standing electrodes for lithium-ion batteries. The structure and morphology of the fibers, and the electrochemical performance of the electrodes and the full battery were characterized. The results show that the LiFePO4 and Li4Ti5O12 fiber membrane electrodes exhibit good rate and cycle performance. In particular, the all-fiber-based gel-state battery composed of LiFePO4 and Li4Ti5O12 fiber membrane electrodes can be charged/discharged for 800 cycles at 1C with a retention capacity of more than 100 mAh·g-1 and a coulombic efficiency close to 100%. The good electrochemical performance is attributed to the high electronic and ionic conductivity provided by the 3D network structure of the self-standing electrodes. This design and preparation method for all-fiber-based lithium-ion batteries provides a novel strategy for the development of high-performance flexible batteries.

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Treatment of high concentration organic wastewater has always been a difficult problem in the field of water purification due to its high cost, low efficiency, long processing cycle and possible second pollution. An overlapped nano-Fe2O3/TiO2@activated carbon fiber membrane composite was successfully prepared by hydrothermal loading method. Nano-rod-like TiO2 and columnar Fe2O3 polyhedrals overlapped and formed a composite coating on the surface of activated carbon fiber membrane. This composite can absorb visible light and successfully remove the high concentration Congo red pollutant (400 mg/L) in 24 h. The enhanced photocatalytic performance should be attributed to the synergistic reaction of nano-Fe2O3 and nano-TiO2, which improves the separation of photo-generated electrons and holes thus enhances the photocatalytic efficiency. This multifunctional fiber membrane is expected to be widely applied in various organic wastewater treatments.

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One-dimensional molybdenum dioxide-carbon nanofibers (MoO2-CNFs) were prepared using an electrospinning technique followed by calcination, using sol-gel precursors and polyacrylonitrile (PAN) as a processing aid. The resulting samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, Brunauer-Emmet-Teller (BET) surface area measurements, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). MoO2-CNFs with an average diameter of 425-575 nm obtained after heat treatment were used as a matrix to prepare sulfur/MoO2-CNF cathodes for lithium-sulfur (Li-S) batteries. The polysulfide adsorption and electrochemical performance tests demonstrated that MoO2-CNFs did not only act as polysulfide reservoirs to alleviate the shuttle effect, but also improve the electrochemical reaction kinetics during the charge-discharge processes. The effect of MoO2-CNF heat treatment on the cycle performance of sulfur/MoO2-CNFs electrodes was examined, and the data showed that MoO2-CNFs calcined at 850 °C delivered optimal performance with an initial capacity of 1095 mAh g-1 and 860 mAh g-1 after 50 cycles. The results demonstrated that sulfur/MoO2-CNF composites display a remarkably high lithium-ion diffusion coefficient, low interfacial resistance and much better electrochemical performance than pristine sulfur cathodes.

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A LiFePO4/C composite fiber membrane was fabricated by the electrospinning method and subsequent thermal treatment. The thermal decomposition process was analyzed by TG/DSC, the morphology, microstructure and composition were studied using SEM, TEM, XRD, Raman, respectively. The results indicated that the prepared LiFePO4/C composite fibers were composed of nanosized LiFePO4 crystals and amorphous carbon coatings, which formed a three dimensional (3D) long-range networks, greatly enhanced the electronic conductivity of LiFePO4 electrode up to 3.59× 10-2 S · cm-2. The 3D LiFePO4/C fiber membrane could be directly used as a binder-free, self-standing cathode for lithium-ion battery, and exhibited an improved capacity and rate performance. The LiFePO4/C composite electrode delivered a discharge capacity of 116 mAh·g-1, 109 mAh·g-1, 103 mAh·g-1, 91 mAh·g-1, 80 mAh·g-1 at 0.1 C, 0.5 C, 1 C, 3 C, 5 C, respectively. And a stable cycling performance was also achieved that the specific capacity could retain 75 mA·g-1 after 500 cycles at 5 C. Therefore, this LiFePO4/C composite fiber membrane was promising to be used as a cathode for power lithium ion battery.

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Improving the specific capacity and electronic conductivity of TiO2 can boost its practical application as a promising anode material for lithium ion batteries. In this work, a three-dimensional networking oxygen-deficient nano TiO2-x/carbon fibre membrane was achieved by combining the electrospinning process with a hot-press sintering method and directly used as a self-standing anode. With the synergistic effects of three-dimensional conductive networks, surface oxygen deficiency, high specific surface area and high porosity, binder-free and self-standing structure, etc., the nano TiO2-x/carbon fibre membrane electrode displays a high electrochemical reaction kinetics and a high specific capacity. The reversible capacity could be jointly generated from porous carbon, full-lithiation of TiO2 and interfacial lithium storage. At a current density of 100 mA g-1, the reversible discharge capacity can reach 464 mA h g-1. Even at 500 mA g-1, the discharge capacity still remains at 312 mA h g-1. Compared with pure carbon fibre and TiO2 powder, the TiO2-x/C fibre membrane electrode also exhibits an excellent cycle performance with a discharge capacity of 209 mA h g-1 after 700 cycles at the current density of 300 mA g-1, and the coulombic efficiency always remains at approximately 100%.

RESUMEN

The ultralong Cu@M (M = Co or Ni) nanowires (NWs) with core­shell structure were fabricated by a simple method by using the prepared Cu NWs as template. The crystal phases of Cu@M (M = Co or Ni) NWs were confirmed by X-ray diffraction (XRD). The morphology and microstructure of NWs were characterized by scanning electro microscopy (SEM) and transmission electro microscopy (TEM). Different diameters of Cu@M (M = Co or Ni) NWs varying from 120 to 550 nm with length about 10 µm were obtained via controlling the amounts of cobalt (nickel) nitrates in the reduction process. The magnetic properties of samples were measured using vibrating sample magnetometer (VSM). Results revealed that Cu NWs has a characteristic of paramagnetism after coating Co or Ni. The coercivity (H(c)) values of Cu@ Ni and Cu@Co NWs were 114.6 and 102.5 Oe, respectively. Possible formation mechanism for Cu@M (M = Co or Ni) NWs was preliminarily proposed.

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Conventional lithium-sulfur batteries suffer from severe capacity fade, which is induced by low electron conductivity and high dissolution of intermediated polysulfides. Recent studies have shown the metal (Pt, Au, Ni) as electrocatalyst of lithium polysulfides and improved the performance for lithium sulfur batteries. In this work, we present the nickel coated multi-walled carbon nanotubes (Ni-MWNTs) as additive materials for elemental sulfur positive electrodes for lithium-sulfur rechargeable batteries. Compared with MWNTs, the obtained Ni-MWNTs/sulfur composite cathode demonstrate a reversible specific capacity approaching 545 mAh after 200 cycles at a rate of 0.5C as well as improved cycling stability and excellent rate capacity. The improved electrochemical performance can be attributed to the fact the MWNTs shows a vital role on polysulfides adsorption and nickel has a catalytic effect on the redox reactions during charge­discharge process. Meanwhile, the Ni-MWNTs is a good electric conductor for sulfur cathode.

RESUMEN

Mg0.6Ni0.4O hollow nanofibers with diameter of 300-600 nm were successfully prepared by elecrospinning a precursor mixture of polyacrylonitrile (PAN)/(magnesium nitrate+ nickel nitrate), followed by calcination treatment of the electrospun polymer/inorganic composite fibers. The resulting Mg0.6Ni0.4O hollow nanofibers were characterized with X-ray diffraction, Brunauere-Emmette-Teller, FT-IR spectra and scanning electron microscopy. Mg0.6Ni0.4O hollow nanofibres were obtained after being calcined at 500 degrees C and their surface became coarse with increasing of calcination temperatures. Possible formation mechanism for Mg0.6Ni0.4O hollow nanofibers was preliminarily proposed.

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Superfine silver nanowires (Ag NWs) with diameter of 40~50 nm and length of 5~10 µm have been synthesized by the self-seeding polyol reduction process using silver nitrate as the silver source, polyvinyl pyrrolidone (PVP) as the structural directing agent, ethylene glycol (EG) as the reducing agent and AgBr as the mediator. The influence of different factors on the growth of Ag NWs was studied. The morphology and crystalline phase of Ag NWs were characterized by the field emission scanning electron microscopy (SEM) and X-ray diffraction (XRD) respectively. The results indicate that the introduction of potassium bromide (KBr) is helpful for growth of Ag NWs with a high aspect ratio, as AgBr colloids formed in the initial stage and the dissociation reaction of AgBr colloids would largely influence the delivering rate of Ag+ ions, which controls the nucleation and growth of the Ag NWs. Finally, the possible growth mechanism of Ag NWs was discussed.

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Nanocrystalline, porous, perovskite La0.8K0.2Fe0.69Mn0.3Pt0.01O3, La0.8K0.2Fe0.67Mn0.3Pt0.03O3, La0.8K0.2Fe0.65Mn0.3Pt0.05O3 catalysts were prepared by the citrate-gel process. The optimized chemical composition La0.8K0.2Fe0.67Mn0.3Pt0.03O3 has a porous structure and it shows a good activity for soot combustion, with T20, T50 and T90 being 149, 367 and 409 °C, respectively. Furthermore, the La0.8K0.2Fe0.67Mn0.3Pt0.03O3-coated honeycomb ceramic device was prepared by the citrate-gel assisted dip-coating process and it has the effect of simultaneous removal of diesel soot and nitrogen oxides at the operational temperature range of 200 to 400 °C, with a NOx maximum conversion rate of 21.2%. It seems that the perovskite structure benefits the activity of low Pt content due to higher contribution of lattice oxygen and local changes in redox reaction.

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The double-sided transparent conductive films of AgNWs/PVC/AgNWs using the silver nanowires and PVC substrate were fabricated by the dip-coating process followed by mechanical press treatment. The morphological and structural characteristics were investigated by scanning electron microscope (SEM) and atomic force microscope (AFM), the photoelectric properties and mechanical stability were measured by ultraviolet-visible spectroscopy (UV-vis) spectrophotometer, four-point probe technique, 3M sticky tape test, and cyclic bending test. The results indicate that the structure and photoelectric performances of the AgNWs films were mainly affected by the dipping and lifting speeds. At the optimized dipping speed of 50 mm/min and lifting speed of 100 mm/min, the AgNWs are evenly distributed on the surface of the PVC substrate, and the sheet resistance of AgNWs film on both sides of PVC is about 60 Ω/sq, and the optical transmittance is 84.55 % with the figure of merit value up to 35.8. The film treated with the 10 MPa pressure shows excellent adhesion and low surface roughness of 17.8 nm and maintains its conductivity with the sheet resistance change of 17 % over 10,000 cyclic bends.

RESUMEN

To obtain low sheet resistance, high optical transmittance, small open spaces in conductive networks, and enhanced adhesion of flexible transparent conductive films, a carbon nanotube (CNT)/silver nanowire (AgNW)-PET hybrid film was fabricated by mechanical pressing-transfer process at room temperature. The morphology and structure were characterized by scanning electron microscope (SEM) and atomic force microscope (AFM), the optical transmittance and sheet resistance were tested by ultraviolet-visible spectroscopy (UV-vis) spectrophotometer and four-point probe technique, and the adhesion was also measured by 3M sticky tape. The results indicate that in this hybrid nanostructure, AgNWs form the main conductive networks and CNTs as assistant conductive networks are filled in the open spaces of AgNWs networks. The sheet resistance of the hybrid films can reach approximately 20.9 to 53.9 Ω/□ with the optical transmittance of approximately 84% to 91%. The second mechanical pressing step can greatly reduce the surface roughness of the hybrid film and enhance the adhesion force between CNTs, AgNWs, and PET substrate. This process is hopeful for large-scale production of high-end flexible transparent conductive films.