Acrylonitrile copolymer/graphene skinned cathode for long cycle life rechargeable hybrid aqueous batteries at high-temperature

The final publication is available at Elsevier via https://dx.doi.org/10.1016/j.electacta.2018.02.098 © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/For aqueous rechargeable lithium battery (ARLB), excellent cycling stability at elevated temperature is highly desirable in its application of electric vehicles (EVs). However, most state-of-art ARLBs show poor durability under high-temperature operation. Herein, we demonstrate a facile coating approach that can construct a thin acrylonitrile copolymer (ANC)/graphene skin on the top-surface of the LiMn2O4 (LMO) cathode in a rechargeable hybrid aqueous lithium battery (ReHAB). Featuring the continuous coverage and the facile electron transport, the ANC/graphene skinned cathode shows a capacity retention of 61% after 300 cycles at 60 °C, two times larger than the battery without the skin. In the cathode, ANC helps to suppress unwanted interfacial side reactions, and graphene renders a robust ion diffusion framework. Quantitative analysis of Mn suggests that the ANC/graphene skin can greatly suppress dissolution of Mn from the LMO into the aqueous electrolyte, while maintaining the charge transfer kinetics. The polymer-based nanocomposite skin on small (1.15 mAh cell) and large (7 mAh cell) cathodes show similar electrochemical improvement, indicting good scale-up potentials

Development of advanced nanocomposite membranes using graphene nanoribbons and nanosheets for water treatment

The final publication is available at Elsevier via https://dx.doi.org/10.1016/j.memsci.2018.04.034 © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/Water-intensive industries have to comply with stringent environmental regulations and evolving regulatory frameworks requiring the development of new technologies for water recycling. Development of polymeric membranes may provide an effective solution to improve water recycling, but require finely-tuned pore size and surface chemistry for ionic and molecular sieving to be efficient. Additionally, fouling is a major challenge that limits the practical application of the membranes in water recycling in these industries. In this work, four different graphene oxide (GO) derivatives were incorporated into a polyethersulfone (PES) matrix via a non-solvent induced phase separation (NIPS) method. The GO derivatives used have different shapes (nanosheets vs nanoribbons) and different oxidation states (C/O = 1.05–8.01) with the potential to enhance water flux and suppress fouling of the membranes through controlled pore size, hydrophilicity, and surface charge. The permeation properties of the PES/GO membranes were evaluated using a water sample from the Athabasca oil sands of Alberta. The results for contact angle and streaming potential measurements indicate the formation of more hydrophilic and negatively charged PES/GO nanocomposite membranes. All graphene-based nanocomposite membranes demonstrated better water flux and rejection of organic matter compared to the unmodified PES membrane. The fouling measurement results revealed that fouling was impeded due to enhanced membrane surface properties. Longitudinally unzipped graphene oxide nanoribbons (GONR-L) at an optimum loading of 0.1 wt% (wt%) provided the maximum water flux (70 LMH at 60 psi), organic matter rejection (59%) and antifouling properties (30% improvement compared to pristine PES membrane). Flux recovery ratio experiments indicated a remarkable enhancement in the fouling resistance property of PES/GO nanocomposite membranes.Natural Sciences and Engineering Research Council of Canada [33413]Natural Resources Canada [32462]Suncor Energy IncorporatedConocoPhillipsUniversity of WaterlooDevon Canad

Doped Graphene Nanoribbons: Synthesis, Characterization and Application

Graphene nanoribbons (GNRs), narrow elongated strips of graphene with ultra-high aspect ratios and abundant edges, have recently become a harbinger of novel carbon nanomaterials due to their versatile properties, particularly if synthesized by unzipping of multiwalled carbon nanotubes (MWCNTs). GNRs have been investigated for the fabrication of polymer nanocomposites, and for use in batteries, supercapacitors and fuel cells owing to the high available surface area and active edge sites, high mechanical strength and electrical conductivity, and the scalability of the synthesis. They could also find applications for peptide mediated drug delivery in biomedicine, and as intrinsically fluorescent nanoparticles in nanotoxicology studies. In this dissertation, MWCNTs with different geometrical characteristics and chemical functionalities have been synthesized, and attempted to unzip via chemical and electrochemical oxidation methods. Upon successful unzipping, some of the carbon atoms in the sp2 network of the product graphene oxide nanoribbons (GONRs) have been substituted by a variety of heteroatoms of approximately the same radius, such as nitrogen, boron and sulfur. Microstructural features, structural defects, crystallinity, thermal stability, and elements and their functional groups have been studied using a wide range of characterization techniques. Finally, doped GNRs nanomaterials have been used as carbon-based electrocatalysts for oxygen reduction reaction (ORR) in alkaline and acidic electrolytes. The results have shown that bamboo structured MWCNTs have been unzipped through helical and dendritic mechanisms, which are substantially different from the longitudinal unzipping of open channel MWCNTs. The resultant GNRs nanomaterials with a multifaceted structure and active edge sites have competed with the current state-of-the-art platinum-based electrocatalysts in all of the key ORR properties: onset potential, exchange current density, four electron pathway selectivity, kinetic current density, stability and methanol tolerance. Such GNRs would have potential applications in the cathodes of metal-air batteries, and alkaline and proton-exchange membrane fuel-cells

Boron/Nitrogen Co-Doped Helically Unzipped Multiwalled Carbon Nanotubes as Efficient Electrocatalyst for Oxygen Reduction

Bamboo structured nitrogen doped multiwalled carbon nanotubes have been helically unzipped, and nitrogen doped graphene oxide nanoribbons (CN_<i>x</i>-GONRs) with a multifaceted microstructure have been obtained. CN_<i>x</i>-GONRs have then been codoped with nitrogen and boron by simultaneous thermal annealing in ammonia and boron oxide atmospheres, respectively. The effects of the codoping time and temperature on the concentration of the dopants and their functional groups have been extensively investigated. X-ray photoelectron spectroscopy results indicate that pyridinic and BC₃ are the main nitrogen and boron functional groups, respectively, in the codoped samples. The oxygen reduction reaction (ORR) properties of the samples have been measured in an alkaline electrolyte and compared with the state-of-the-art Pt/C (20%) electrocatalyst. The results show that the nitrogen/boron codoped graphene nanoribbons with helically unzipped structures (CN_<i>x</i>/CB_<i>x</i>-GNRs) can compete with the Pt/C (20%) electrocatalyst in all of the key ORR properties: onset potential, exchange current density, four electron pathway selectivity, kinetic current density, and stability. The development of such graphene nanoribbon-based electrocatalyst could be a harbinger of precious metal-free carbon-based nanomaterials for ORR applications

Hierarchical Design in LiMn2O4 Particles for Advanced Hybrid Aqueous Batteries

Recently, tremendous research has been done on fast-charged Li-ion batteries for use in vehicles. If the Li-ion cathode could be fully charged at 10 C or in 6 min, this charging time would be the same magnitude as the filling period of the hydrogen-fuelcell vehicles or the diesel-filling time on trucks. This current obstacle is solved in this work at an industrial level, using a completely green method without the need for any extra chemical product. We focus on the gentle exfoliating secondary particles of the commercial LiMn2O4 to deliver mixtures of submicron size secondary and primary particles without severe amorphization of the crystalline surface. The products are characterized by XRD and SEM. The electrochemical activity of this submicron LiMn2O4 is evaluated as the cathode in a 5 A.h scale rechargeable hybrid aqueous battery (i.e., 20,000 times higher than a typical laboratory coin cell). High capacity values of 124.1 mA h g(-1) after 100 cycles under 0.2 C and 89.3 mA h g(-1) after 1000 cycles at 10 C with no obvious capacity fading are realized. The mechanism is explained in detail, which includes quantitative contributions of pseudocapacity and intercalation