Feasibility of Chemically Modified Cellulose Nanofiber Membranes as Lithium-Ion Battery Separators.

Chemical modification of cellulose is beneficial to produce highly porous lithium-ion battery (LIB) separators, but introduction of high charge density adversely affects its electrochemical stability in a LiNi1/3Mn1/3Co1/3O2 (NMC)/graphite full cell. In this study, the influence of carboxylate functional groups in 2,2,6,6-tetramethylpiperidine-1-oxyl-mediated oxidized cellulose nanofibers (TOCNs) on the electrochemical performances of the LIB separator was investigated. X-ray photoelectron spectroscopy and in operando mass spectrometry measurements were used to elucidate the cause of failure of the batteries containing TOCN separators in the presence and absence of sodium counterions in the carboxylate groups and additives. For the TOCN separator with sodium carboxylate functional groups, it seems that Na deposition is the dominant reason for poor electrochemical stability of the cell thereof. The poor performance of the protonated TOCN separator, attributed to a high amount of gas evolution, is dramatically improved by adding 2 wt % of vinylene carbonate (VC) because of suppressed gas evolution. Unveiling the failure mechanism of the TOCN separators and successively implementing the strategies to improve performance, for example, removing Na, adding VC, and adjusting cycling rates, enable a remarkable cycling performance in the NMC/graphite full cell at ≈2 C (3 mA/cm2) of a fast discharging rate. Despite the aforementioned efforts and compromises required, an increased charge density of the TOCN is beneficial to acquire a mechanically stronger separator. In conclusion, the manufacturing process of cellulose nanofibers needs to be carefully adjusted to acquire a desired separator property. To the best of our knowledge, it is first reported to perform operando gas evolution measurements to systematically investigate the electrochemical stability of nanocellulose as an LIB separator material. The results elucidate not only the challenges for extensive applications of hygroscopic biomaterials for commercial LIBs but also the practical solutions to achieve high electrochemical stability of the materials.

Application of novel bacterial consortium for biodegradation of aromatic amine 2-ABS using response surface methodology.

There is a strong need to develop purification methods for textile industrial wastewater containing toxic azo dyes. The reductive cleavage of azo dyes can be made by anaerobic bacteria, but the products of aromatic amines require an aerobic process. In this study a novel bacterial dye degrading consortium (DDC) of five isolated strains identified with 16S rRNA sequence: Proteus mirabilis (KR732288), Bacillus anthracis (KR732289), Enterobacter hormaechei (KR732290), Pseudomonas aeruginosa (KR732293) and Serratia rubidaea (KR732296) were used to aerobically decompose metabolite 2-aminobenxenesulfonic acid (2-ABS), as a model compound. The effect of three variables: temperature (28-42 °C), pH (5.0-8.0) and initial concentration of 2-ABS (5-40 ppm) was investigated in terms of degradation and chemical oxygen demand (COD) removal. Central composite design matrixand response surface methodology (RSM) were used for experimental design to evaluate theinteraction of the three process variables. The results show that up to 95% degradation and COD 90% removal are possible at optimal values of 32.4 ppm 2-ABS, pH 6.6 and a temperature of 35.7 °C. The theoretical response variables predicted by the developed RSM model was supported the experimental results. The optimized degradation of 2-ABS and COD removal were further confirmed by UV-HPLC analysis.

Fuel Cell Measurements with Cathode Catalysts of Sputtered Pt3 Y Thin Films.

Fuel cells are foreseen to have an important role in sustainable energy systems, provided that catalysts with higher activity and stability are developed. In this study, highly active sputtered thin films of platinum alloyed with yttrium (Pt3 Y) are deposited on commercial gas diffusion layers and their performance in a proton exchange membrane fuel cell is measured. After acid pretreatment, the alloy is found to have up to 2.5 times higher specific activity than pure platinum. The performance of Pt3 Y is much higher than that of pure Pt, even if all of the alloying element was leached out from parts of the thin metal film on the porous support. This indicates that an even higher performance is expected if the structure of the Pt3 Y catalyst or the support could be further improved. The results show that platinum alloyed with rare earth metals can be used as highly active cathode catalyst materials, and significantly reduce the amount of platinum needed, in real fuel cells.

Quantifying mass transport during polarization in a Li ion battery electrolyte by in situ 7Li NMR imaging.

Poor mass transport in the electrolyte of Li ion batteries causes large performance losses in high-power applications such as vehicles, and the determination of transport properties under or near operating conditions is therefore important. We demonstrate that in situ (7)Li NMR imaging in a battery electrolyte can directly capture the concentration gradients that arise when current is applied. From these, the salt diffusivity and Li(+) transport number are obtained within an electrochemical transport model. Because of the temporal, spatial, and chemical resolution it can provide, NMR imaging will be a versatile tool for evaluating electrochemical systems and methods.