Showing papers by "Min Xiao published in 2019"

Single-ion conducting artificial solid electrolyte interphase layers for dendrite-free and highly stable lithium metal anodes

Abstract: Lithium metal anodes are regarded as “Holy Grail” anode materials, due to their ultrahigh theoretical capacity, low redox potential and low density. However, native solid electrolyte interphases (SEIs) generated from reactions of lithium metals with electrolytes are unstable and easily destroyed by huge volume change during cycling, giving rise to side reactions and lithium dendrites. We designed and fabricated a single-ion conducting artificial SEI layer for high-performance lithium metal anodes. A LiBAMB-PETMP (LP) SEI layer was prepared by a thiol-ene click reaction on lithium metal, forming a three dimensional (3D) cross-linked network structure. BAMB anions are covalently bonded in this 3D cross-linked network, achieving single-ion conduction. This BAMB anion network can guide lithium ions to uniformly distribute and deposit. Its high ionic conductivity and unity lithium ion transference number can eliminate anion depletion-induced strong electric fields on the anodes to prevent the nucleation of dendrites. The LP SEI layer is both chemically and mechanically stable during cycling and protects lithium metal from corrosion by electrolytes. Stable lithium plating/stripping at an ultrahigh current density of 8.0 mA cm−2 is achieved for 992 h. The innovative strategy of single-ion conducting artificial SEI layer design is promising for application in lithium metal anodes.

Ultrastrong and Heat-Resistant Poly(ether ether ketone) Separator for Dendrite-Proof and Heat-Resistant Lithium-Ion Batteries

Abstract: Separators are a pivotal component of lithium-ion batteries (LIBs) due to their vital role in maintaining a good ionic flow and preventing internal short circuit. The separators with superior thermal stability, ultrahigh mechanical strength, and excellent electrolyte wettability are essential for ensuring the safety and energy density of LIBs. Herein, an ultrastrong poly(ether ether ketone) (PEEK) separator is fabricated via thermally induced phase separation using a binary diluent for the first time, which maintains the intrinsic outstanding properties of a PEEK resin. Computational simulation and experimental verification are performed to optimize fabrication conditions. The as-prepared PEEK separator with high porosity (70.3%) shows a tortuous and three-dimensional porous structure; furthermore, the abundant polar groups on PEEK endow the separator with excellent electrolyte wettability (contact angle of 19° and electrolyte uptake of 387%). Notably, the PEEK separator exhibits excellent thermal stabili...

A Review on Sulfonated Polymer Composite/Organic-Inorganic Hybrid Membranes to Address Methanol Barrier Issue for Methanol Fuel Cells.

Abstract: This paper focuses on a literature analysis and review of sulfonated polymer (s-Poly) composites, sulfonated organic, inorganic, and organic–inorganic hybrid membranes for polymer electrolyte membrane fuel cell (PEM) systems, particularly for methanol fuel cell applications. In this review, we focused mainly on the detailed analysis of the distinct segment of s-Poly composites/organic–inorganic hybrid membranes, the relationship between composite/organic– inorganic materials, structure, and performance. The ion exchange membrane, their size distribution and interfacial adhesion between the s-Poly composites, nanofillers, and functionalized nanofillers are also discussed. The paper emphasizes the enhancement of the s-Poly composites/organic–inorganic hybrid membrane properties such as low electronic conductivity, high proton conductivity, high mechanical properties, thermal stability, and water uptake are evaluated and compared with commercially available Nafion® membrane.

CO2 Nanoenrichment and Nanoconfinement in Cage of Imine Covalent Organic Frameworks for High-Performance CO2 Cathodes in Li-CO2 Batteries.

Abstract: The Li-CO2 battery is an emerging green energy technology coupling CO2 capture and conversion. The main drawback of present Li-CO2 batteries is serious polarization and poor cycling caused by random deposition of lithium ions and big insulated Li2 CO3 formation on the cathode during discharge. Herein, covalent organic frameworks (COF) are identified as the porous catalyst in the cathode of Li-CO2 batteries for the first time. Graphene@COF is fabricated, graphene with thin and uniform imine COF loading, to enrich and confine CO2 in the nanospaces of micropores. The discharge voltage is raised by higher local CO2 concentration, which is predicted by the Nernst equation and realized by CO2 nanoenrichment. Moreover, uniform lithium ion deposition directed by the graphene@COF nanoconfined CO2 can produce smaller Li2 CO3 particles, leading to easier Li2 CO3 decomposition and thus lower charge voltage. The graphene@COF cathode with 47.5% carbon content achieves a discharge capacity of 27833 mAh g-1 at 75 mA g-1 , while retaining a low charge potential of 3.5 V at 0.5 A g-1 for 56 cycles.

Ultrahigh Li-ion conductive single-ion polymer electrolyte containing fluorinated polysulfonamide for quasi-solid-state Li-ion batteries

Abstract: With the rapid development of electronic devices and electric vehicles, the requirements for their safety issues and service stabilities have become more and more strict. Single-ion gel polymer electrolytes exhibit outstanding ion conduction, high safety, good flexibility and a lithium transference number close to unity, leading to extensive research. In this work, a flexible fluorinated polysulfonamide based single-ion polymer electrolyte (SIPE) was synthesized using lithium [(4-styrenesulfonyl)(fluorosulfonyl)imide] (LiSFSI), pentaerythritol tetrakis(3-mercaptopropionate) (PETMP) and pentaerythritol tetraacrylate (PET4A) via one-step in situ photoinitiated thiol–ene click reaction in plasticizers, with electrospun poly(vinylidene fluoride) (PVDF) as the standing membrane. The influence of plasticizer content was investigated and the optimized electrolyte exhibits ultra-high ionic conductivity (5.81 × 10−3 S cm−1 at 28 °C) and a high lithium transference number of 0.91, near to unity. This ionic conductivity is among the highest ionic conductivities exhibited by SIPEs reported to date. Its electrochemical stability window is up to 5.2 V. More importantly, Li/LiFePO4 cells using the prepared SIPE as both the electrolyte and separator displayed high reversible capacity at room temperature. It also exhibits excellent long-term stability and reliability as it maintains a capacity of 140 mA h g−1 at 0.2C rate even after 230 cycles without obvious decay at room temperature.

CO2 derived biodegradable polycarbonates: Synthesis, modification and applications

Abstract: Fixation carbon dioxide into polymer is a feasible proposal to construct high value-added biodegradable plastic. These polymers are environmentally friendly and energy-saving owing to that the raw material is waste gas and finally they decompose back into CO2. This review mainly focuses on our group work of recent advancements on CO2-based copolymers, especially for poly (propylene carbonate) (PPC). We also extensively introduce the improvements on thermal and mechanical performances of PPC by physical and chemical modifications. Meanwhile, their practical application is further discussed in detail as well to replace the conventionally non-biodegradable plastics. The commercial PPC has already been found an enormous application prospect in versatile packaging industry.

One-Pot Synthesis of Dimethyl Hexane-1,6-diyldicarbamate from CO2, Methanol, and Diamine over CeO2 Catalysts: A Route to an Isocyanate-Free Feedstock for Polyurethanes

Abstract: A new one-pot synthesis method of dimethyl hexane-1,6-diyldicarbamate (HDC), a potential intermediate compound in the synthesis of polyurethanes, from CO2, methanol, and 1,6-hexanediamine (HDA) is disclosed. The starting materials are renewable, stable, easily available, and cheap. The process was implemented in 1-methyl-2-pyrrolidinone (NMP) solvent over CeO2 catalysts. Three different CeO2 catalysts (commercial nanospheres, CeO2(c) obtained by direct calcination of (NH4)2Ce(NO3)6, and CeO2 nanorods) were tested in this reaction and their micromorphology and physical–chemical properties were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and N2 adsorption. CeO2 nanorods proved to be the most active catalytic material. The influence of different parameters on reaction outcome was studied. The yield of HDC was about 80% under optimized reaction conditions. Experiments for better understanding of reaction mechanism were also performed.

Lithium Borate Containing Bifunctional Binder To Address Both Ion Transporting and Polysulfide Trapping for High-Performance Li-S Batteries.

Abstract: A slightly cross-linked lithium borate containing single ion-conducting polymer (LBSIP) as a bifunctional binder for lithium sulfur batteries is designed and fabricated via a one-step thiol–ene cli...

Synthesis of Polylactide Nanocomposites Using an α-Zirconium Phosphate Nanosheet-Supported Zinc Catalyst via in Situ Polymerization

Abstract: Immobilized catalysis integrates the advantages of both homogeneous and heterogeneous catalyst systems and thus has attracted high attention. Herein, we report the synthesis of a novel immobilized ...

Gold nanoparticles immobilized on single-layer α-zirconium phosphate nanosheets as a highly effective heterogeneous catalyst

Abstract: Gold nanoparticles (Au NPs) were immobilized on single-layered α-zirconium phosphate (ZrP) nanosheets as a highly efficient heterogeneous catalyst. The nanoparticles were characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), X-ray photoelectric spectroscopy (XPS), UV–Vis spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. The characterizations showed that the Au NPs with a size distribution of 2.0 ± 1.0 nm were uniformly dispersed and immobilized on single-layer ZrP nanosheets. The supported AuNPs could serve as an effective catalyst for the reduction of 4-nitrophenol by sodium borohydride (NaBH4).

High performance poly(urethane-co-amide) from CO2-based dicarbamate: an alternative to long chain polyamide

Abstract: Due to its high strength, toughness, corrosion resistance and wear resistance, long chain polyamide (LCPA) has attracted broad interest. Nevertheless, its wide application in industrial fields is still being restricted because the starting material acquisition step involving diacid and diamine remains a major obstacle. Herein, we circumvent this obstacle by developing a novel polymer with similar properties by a green and efficient copolymerization process of carbon dioxide (CO2)-based dicarbamate with diamide diol under vacuum conditions, named poly(urethane-co-amide) (PUA). The semi-crystalline PUAs with high number-weight-average molecular weights (Mn, up to 41.3 kDa) were readily obtained, and these new polymers show high thermal stability (above 300 °C). Thanks to its unique chain structure, the amide, urethane and urea groups can endow the polymer with a high density cross-linking network via hydrogen bonds and high crystallinity that can result in high strength, up to 54.0 MPa. The dynamic thermomechanical analysis (DMA) results suggest that the phase separation exists within the new polymers, endowing the PUAs with a toughness higher than that of long chain polyamides. Consequently, this work not only develops a useful new polymer like commercial polyamides with high performance as a long chain polyamide candidate, but also provides a new way of utilizating CO2.

Hierarchical NiCoP/C Hollow Nanoflowers for Enhanced Lithium Storage

Abstract: Multidimensional morphologies of double-metal phosphides prominently can enrich the patterns of electron transport and charge storage. Here, we report a facile encapsulation strategy with one acety...

Heteropolyacid Salt Catalysts for Methanol Conversion to Hydrocarbons and Dimethyl Ether: Effect of Reaction Temperature

Abstract: Phosphotungstic and silicotungstic acid salt catalysts (CuPW, CuSiW, FePW, FeSiW) were synthesized by substitution of protons with ferric and copper ions through a simple replacement reaction. The structure and thermal stability were characterized by IR, XRD and TG, and the salts showed a keggin structure and a thermal tolerance near 450 °C. Temperature programmed reactions indicated that the four catalysts showed similar trends in the change of methanol conversion, DME selectivity, and light olefins selectivity at 100–400 °C. Copper salt catalysts showed a 100% DME selectivity at temperatures ranging from 100–250 °C, while FeSiW and FePW catalysts had a 100% DME selectivity near 250 °C. Moreover, the heteropolyacid salt catalysts also produced a certain number of light olefins at the temperature ranging from 250–350 °C, and the CuSiW catalyst exhibited the highest ethylene and propylene selectivity of 44%. In the stability test evaluated at 200 °C, the catalysts showed different tendencies during the induction period and the same trends during the reduction period for the methanol conversion to DME, due to the differences in the strengths of the strong acid sites. Finally, the silicotungstic acid salt catalysts showed the longest lifetime of 120 h, much longer than the heteropolyacids. This approach provides an effective way to synthesize hydrocarbons through methanol, especially DME, at different temperatures using one catalyst.

Co-Ni Cyanide Bi-Metal Catalysts: Copolymerization of Carbon Dioxide with Propylene Oxide and Chain Transfer Agents

Abstract: Synthesis of copolymers from carbon dioxide (CO2) and epoxides is an important research direction as such processes utilize the abundant greenhouse gas and deliver useful products. Specifically, cooligomers of CO2 and propylene oxide (PO) with a non-alternating structure can be used for polyurethane preparation. They are synthesized by employing Zn-Co cyanide catalysts. The application of alternative metal cyanide complexes is interesting from scientific and practical points of view. The purpose of this work was to study the copolymerization of CO2 and PO in the presence of Co-Ni cyanide catalysts and chain transfer agents (CTAs) in order to obtain low molecular weight products. Three Co-Ni catalysts with different contents of complexing agents were synthesized, characterized by several analytical methods and applied for this reaction. The complex without complexing agents was chosen for detailed investigation. 1,6-Hexanediol proved to be a more preferred CTA than poly(propylene glycol) and adipic acid. An oligo(ethercarbonate) (Mn = 2560, PDI = 2.5, CO2 = 20 mol.%) capped with OH groups was synthesized with relatively high productivity (1320 gPO+CO2/gcat in 24 h) and characterized by matrix-assisted laser desorption/ionization (MALDI) MS and NMR methods. The main chain transfer routes during the cooligomerization were suggested on the basis of the research results.

Low-Carbon and Nanosheathed ZnCo2O4 Spheroids with Porous Architecture for Boosted Lithium Storage Properties

Abstract: Multielectronic reaction electrode materials for high energy density lithium-ion batteries (LIBs) are severely hindered by their inherent sluggish kinetics and large volume variations, leading to rapid capacity fade. Here, a simple method is developed to construct low-carbon and nanosheathed ZnCo2O4 porous spheroids (ZCO@C-5). In this micro/nanostructure, an ultrathin amorphous carbon layer (~2 nm in thickness) is distributed all over the primary nanosized ZCO particles (~20 nm in diameter), which finally self-assembles into porous core (ZCO)-shell(carbon) micron spheroids. The nanoencapsulation and macro/mesoporous architecture can not only provide facile electrolyte penetration and rapid ion/electron transfer but also better alleviate volumetric expansion effect to avoid pulverization of ZCO@C-5 spheroids during repeat charge/discharge processes. As expected, the three-dimensional porous ZCO@C-5 composites exhibit high reversible capacity of 1240 mAh g−1 cycle at 500 mA g−1, as well as excellent long-term cycling stability and rate capability. The low-carbon and nanoencapsulation strategy in this study is simple and effective, exhibiting great potential for high-performance LIBs.

A novel thermoplastic elastomer from double CO2-Route oligomers

Abstract: As carbon dioxide (CO2) is an inexpensive, abundant, sustainable and green carbonyl resource, its utilization to produce value-added chemicals and polymeric materials has attracted much more attention. In this work, a novel CO2 route polyurea (PUa) was synthesized. The chemical composition, molecular structure, and aggregation structure of polyurea has been confirmed by 1H-NMR, HMBC-NMR, DSC, TG, MALDI-TOF MS and POM. The result from POM shows that polyurea gives out a spherulitic morphology, exhibited a typical black cross pattern formed by many concentric circles with different light and shade. Moreover, shape memory polymers of polyurea-multiblock-poly(propylene carbonate) (PUa-mb-PPCs) with a Mn nearly 4.72 × 104 Da and a polydispersity index (PDI) of 1.51–1.64 were synthesized by chain extension of the polyurea with CO2 derived poly(propylene carbonate) diols (PPC-OH). The PUa-mb-PPCs possess high strength and elasticity because the crystallinity formed by polyurea and amorphous region from PPC. Notably, excellent shape memory effect (SME) is observed in shape thermomechanical testing. The present work provides a simple and renewable process for the synthesis of CO2-copolymer with multiblock structure, opening a new route for preparation of functional polymeric materials from carbon dioxide conversion.