Total Mass Of Composite Research Articles

Simulation Evaluation of Power of Sampling Plans to Detect Cronobacter in Powdered Infant Formula Production

Cronobacteris a hazard in Powdered Infant Formula (PIF) products that is hard to detect due to localized and low-level contamination. We adapted a previously published sampling simulation to PIF sampling and benchmarked industry-relevant sampling plans across different numbers of grabs, total sample mass, and sampling patterns. We evaluated performance to detect published Cronobacter contamination profiles for a recalled PIF batch [42% prevalence, −1.8 ± 0.7 log(CFU/g)] and a reference, nonrecalled, PIF batch [1% prevalence, −2.4 ± 0.8 log(CFU/g)]. Simulating a range of numbers of grabs [n = 1–22,000 (representing testing every finished package)] with 300 g total composite mass showed that taking 30 or more grabs detected contamination reliably (<1% median probability to accept the recalled batch). Benchmarking representative sampling plans ([n = 30, mass grab = 10g], [n = 30, m = 25g], [n = 60, m = 25g], [n = 180, m = 25g]) showed that all plans would reject the recalled batch (<1% median probability to accept) but would rarely reject the reference batch (>50% median probability of acceptance, all plans). Overall, (i) systematic or stratified random sampling patterns are equal to or more powerful than random sampling of the same sample size and total sampled mass, and, (ii) taking more samples, even if smaller, can increase the power to detect contamination.

Organic Solvent Free Process to Fabricate High Performance Silicon/Graphite Composite Anode

Cycling stability is a key challenge for application of silicon (Si)-based composite anodes as the severe volume fluctuation of Si readily leads to fast capacity fading. The binder is a crucial component of the composite electrodes. Although only occupying a small amount of the total composite mass, the binder has major impact on the long-term electrochemical performance of Si-based anodes. In recent years, water-based binders including styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) have attracted wide research interest as eco-friendly and low-cost alternatives for the conventional poly(vinylidene difluoride) (PVDF) binder in Si anodes. In this study, Si-based composite anodes are fabricated by simple solid mixing of the active materials with subsequent addition of SBR and CMC binders. This approach bypasses the use of toxic and expansive organic solvents. The factors of binder, silicon, and graphite materials have been systematically investigated. It is found that the retained capacities of the anodes are more than 440 mAh/g after 400 cycles. These results indicate that organic solvent free process is a facile strategy for producing high performance silicon/graphite composite anodes.

Hierarchically porous carbon/red phosphorus composite for high-capacity sodium-ion battery anode

Red phosphorus has received remarkable attention as a promising anode material for sodium ion batteries (NIBs) due to its high theoretical capacity. However, its practical application has been impeded by its intrinsic low electronic conductivity and large volume variations during sodiation/desodiation process. Here, we design a composite to confine nanosized red phosphorus into the hierarchically porous carbon (HPC) walls by a vaporization-condensation strategy. The mass loading of P in the HPC/P composite is optimized to deliver a reversible specific capacity of 2,202 mAh/gp based on the mass of red P (836 mAh/gcomposite based on the total composite mass), a high capacity retention over 77% after 100 cycles, and excellent rate performance of 929 mAh/gp at 2 C. The hierarchical porous carbon serves as the conductive networks, downsize the red phosphorus to nanoscale, and provide free space to accommodate the large volume expansions. The suppressed mechanical failure of the red phosphorus also enhances the stability of solid-electrolyte interface (SEI) layer, which is confirmed by the microscopy and impedance spectroscopy after the cycling tests. Our studies provide a feasible approach for potentially viable high-capacity NIB anode.

Selenium Impregnated Monolithic Carbons as Free-Standing Cathodes for High Volumetric Energy Lithium and Sodium Metal Batteries

Energy density (energy per volume) is a key consideration for portable, automotive and stationary battery applications. We created selenium (Se) lithium and sodium metal cathodes that are monolithic and free-standing, and with record Se loading of 70 wt%. The carbon host is derived from nanocellulose, an abundant and sustainable forestry product. The composite is extremely dense (2.37 g cm-3), enabling theoretical volumetric capacity of 1120 mAh cm-3. Such architecture is fully distinct from previous Se – carbon nano or micropowders, intrinsically offering up to 2X higher energy density. For Li storage, the cathode delivered reversible capacity of 1028 mAh cm-3 (620 mAh g-1) and 82% retention over 300 cycles. For Na storage 848 mAh cm-3 (511 mAh g-1) was obtained with 98% retention after 150 cycles. The electrodes yield superb volumetric energy densities, being 1727 Wh L-1 for Li-Se and 980 Wh L-1 for Na-Se normalized by total composite mass and volume. Despite the low surface area, over 60% capacity is maintained as the current density is increased from 0.1 to 2 C (30 min charge) with Li or Na. Remarkably, the electrochemical kinetics with Li and Na are comparable, including the transition from interfacial to diffusional control.

Selenium Impregnated Monolithic Carbons as Free‐Standing Cathodes for High Volumetric Energy Lithium and Sodium Metal Batteries

AbstractEnergy density (energy per volume) is a key consideration for portable, automotive, and stationary battery applications. Selenium (Se) lithium and sodium metal cathodes are created that are monolithic and free‐standing, and with record Se loading of 70 wt%. The carbon host is derived from nanocellulose, an abundant and sustainable forestry product. The composite is extremely dense (2.37 g cm−3), enabling theoretical volumetric capacity of 1120 mA h cm−3. Such architecture is fully distinct from previous Se–carbon nano‐ or micropowders, intrinsically offering up to 2× higher energy density. For Li storage, the cathode delivers reversible capacity of 1028 mA h cm−3 (620 mA h g−1) and 82% retention over 300 cycles. For Na storage, 848 mA h cm−3 (511 mA h g−1) is obtained with 98% retention after 150 cycles. The electrodes yield superb volumetric energy densities, being 1727 W h L−1 for Li–Se and 980 W h L−1 for Na–Se normalized by total composite mass and volume. Despite the low surface area, over 60% capacity is maintained as the current density is increased from 0.1 to 2 C (30 min charge) with Li or Na. Remarkably, the electrochemical kinetics with Li and Na are comparable, including the transition from interfacial to diffusional control.

Enhanced Reversible Sodium‐Ion Intercalation by Synergistic Coupling of Few‐Layered MoS2 and S‐Doped Graphene

AbstractSodium‐ion batteries (SIBs) are regarded as the best alternative to lithium‐ion batteries due to their low cost and similar Na+ insertion chemistry. It is still challenging but greatly desired to design and develop novel electrode materials with high reversible capacity, long cycling life, and good rate capability toward high‐performance SIBs. This work demonstrates an innovative design strategy and a development of few‐layered molybdenum disulfide/sulfur‐doped graphene nanosheets (MoS2/SG) composites as the SIB anode material providing a high specific capacity of 587 mA h g−1 calculated based on the total composite mass and an extremely long cycling stability over 1000 cycles at a current density of 1.0 A g−1 with a high capacity retention of ≈85%. Systematic characterizations reveal that the outstanding performance is mainly attributed to the unique and robust composite architecture where few‐layered MoS2 and S‐doped graphene are intimately bridged at the hetero‐interface through a synergistic coupling effect via the covalently doped S atoms. The design strategy and mechanism understanding at the molecular level outlined here can be readily applied to other layered transition metal oxides for SIBs anode and play a key role in contributing to the development of high‐performance SIBs.

One-dimensional porous nanofibers of Co3O4 on the carbon matrix from human hair with superior lithium ion storage performance.

One-dimensional (1D) hierarchical porous nanofibers of Co3O4 possessing of (220) facets on the carbon matrix from human hair (H2@Co3O4) with 20–30 nm in width and 3–5 μm in length are prepared by a facile solvothermal and calcination approach. The well crystallized small Co3O4 particles with the diameter of about 8–12 nm were closely aggregated together in the nanofibers. Electrochemical analyses show that the first discharge capacity of H2@Co3O4 electrode is 1368 mAh g−1 at the current density of 0.1 A g−1 based on the total mass of composite. A high reversible capacity of 916 mAh g −1 was obtained over 100 cycles at 0.1 A g−1, presenting a good cycling stability. When cycled at a high current density of 1 and 2 A g−1, the specific capacity of 659 and 573 mAh g−1 could be still achieved, respectively, indicating a superior power capability.

Electrostatic shield effect: an effective way to suppress dissolution of polysulfide anions in lithium–sulfur battery

Sulfur has a very high theoretical specific capacity of 1672 mA h g−1 when used in lithium–sulfur batteries. However, the particularly rapid capacity reduction owing to the dissolution of intermediate polysulfide anions into the electrolyte still hinders practical application. In this respect, we report a novel core–shell structured sulfur–poly(sodium p-styrenesulfonate) (S@PSS) composite cathode material with a sulfur content as high as 93 wt% for lithium–sulfur batteries, which is the highest sulfur content disclosed in the literature. Due to the effective transport of lithium cations while blocking polysulfide anions by common ion Coulombic repulsion of the negatively charged –SO3− groups in the PSS protective layer, the S@PSS composite cathode exhibits a high initial specific capacity of 1159 mA h g−1 at a 0.1 C rate, and retains a stable discharge capacity of 972 mA h g−1 after 70 cycles and 845 mA h g−1 after 120 cycles with a high Coulombic efficiency of over 99%. To our knowledge, this new methodology for lithium–sulfur cathodes has not been reported so far; the initial specific capacity is the highest value calculated based on total composite mass, which has not been disclosed in the literature.

Nanocomposites of Ni(OH)2/Reduced Graphene Oxides with Controllable Composition, Size, and Morphology: Performance Variations as Pseudocapacitor Electrodes

AbstractAlthough Ni(OH)2 is a promising electrode material for electrochemical capacitors on account of its high theoretical specific capacitance and low cost, its application has been hindered by the low measured specific capacitance and poor cycle stability often associated with low specific surface area and poor electrical conductivity. This study aims to develop an amorphous‐precursor method to anchor Ni(OH)2 nanocrystals onto conductive graphene sheets. We demonstrate the ability to control the composition, size, and morphology of Ni(OH)2 nanocrystals on graphene sheets by combination with an Ostwald ripening process, which has allowed investigation on how such factors influence their performance if used as pseudocapacitor electrodes. It was found that the specific capacitance increased and then decreased as the ratio of reduced graphene oxide (RGO) to Ni(OH)2 increased; the sample that contained 5.2 wt % of RGO achieved the highest specific capacitance of 1804.0 F g−1 (based on the total composite mass) and 1902.9 F g−1 (based on the mass of Ni(OH)2), close to the theoretical value of Ni(OH)2 (2082 F g−1). With a given ratio of RGO to Ni(OH)2, the specific capacitance decreased as the Ni(OH)2 nanocrystal size increased. However, the cycling performance increased as the stability of Ni(OH)2 in the nanocomposites increased; the highest was achieved for the most stable Ni(OH)2 hexagonal nanoplates on RGO. In all, with appropriate optimization of the parameters of the materials, a good pseudocapacitor performance was achieved for the Ni(OH)2/RGO hybrid system in terms of both the specific capacitance and the cycling stability.