Black carbon and mineral dust in snow cover across a typical city of Northeast China.

Light-absorbing impurities (LAIs), including black carbon (BC) and mineral dust (MD), in snow cover reduce snow albedo and accelerate the snow melting rate, thus influencing the regional water resources, ecological environmental security, and climate change. There is still a lack of quantitative assessments of the impacts of BC and MD on snowmelt in urban areas. This study was conducted from December 2018 to March 2019. A total of 120 snow samples were collected in Harbin, Northeast China to quantitatively assess the concentration characteristics of BC and MD in snow cover in different urban polluted areas and the impacts on snow albedo, radiative forcing, and snow melting. Average concentrations of BC and MD in snow cover in Harbin were 126,121.03 ng g-1 and 1419.6 µg g-1, respectively. Average concentrations of BC and MD in the industrial area were the highest, which were 4.06 and 3.13 times higher, respectively, than those in the suburban area. BC or MD decreased the average snow albedo by 0.3677 (58.49%) and 0.0583 (18.18%) with radiative forcing of 44.94 W m-2 and 7.58 W m-2, respectively. BC and MD in the industrial area, residential area, and suburban area decreased the average albedo by 0.449 (59.55%), 0.3758 (45.86%), and 0.2959 (37.65%), respectively. The impacts on snow melting time in Harbin were mainly attributed to BC, which advanced snow melting by 7.9 ±â€¯1.16 d, while MD advanced snow melting by 3.7 ±â€¯0.9 d. Under the combined effect of BC and MD, the industrial area, residential area, and suburban area in the city experienced advanced snow melting by 9.66 ±â€¯0.38 d, 7.97 ±â€¯0.31 d, and 6.67 ±â€¯0.65 d, respectively. The results can be used to assess the contribution of intense human disturbance to snow melting.

Influence of Binders, Carbons, and Solvents on the Stability of Phosphorus Anodes for Li-ion Batteries.

Phosphorus (P) is an abundant element that exhibits one of the highest gravimetric and volumetric capacities for Li storage, making it a potentially attractive anode material for high capacity Li-ion batteries. However, while phosphorus carbon composite anodes have been previously explored, the influence of the inactive materials on electrode cycle performance is still poorly understood. Here, we report and explain the significant impacts of polymer binder chemistry, carbon conductive additives, and an under-layer between the Al current collector and ball milled P electrodes on cell stability. We focused our study on the commonly used polyvinylidene fluoride (PVDF) and poly(acrylic acid) (PAA) binders as well as exfoliated graphite (ExG) and carbon nanotube (CNT) additives. The mechanical properties of the binders were found to change drastically because of interactions with both the slurry and electrolyte solvents, significantly effecting the electrochemical cycle stability of the electrodes. Binder adhesion was also found to be critical in achieving stable electrochemical cycling. The best anodes demonstrated ∼1400 mAh/g-P gravimetric capacity after 200 cycles at C/2 rates in Li half cells.

Infiltrated Porous Polymer Sheets as Free-Standing Flexible Lithium-Sulfur Battery Electrodes.

Free-standing, high-capacity Li2 S electrodes with capacity loadings in the range from 1.5 to 3.8 mA h cm(-2) are produced by using infiltration of active materials into porous carbonized biomass sheets. The proposed electrode design can be effectively utilized for the low-cost fabrication of flexible lithium batteries with high specific energy.

Lithium Titanate Confined in Carbon Nanopores for Asymmetric Supercapacitors.

Porous carbons suffer from low specific capacitance, while intercalation-type active materials suffer from limited rate when used in asymmetric supercapacitors. We demonstrate that nanoconfinement of intercalation-type lithium titanate (Li4Ti5O12) nanoparticles in carbon nanopores yielded nanocomposite materials that offer both high ion storage density and rapid ion transport through open and interconnected pore channels. The use of titanate increased both the gravimetric and volumetric capacity of porous carbons by more than an order of magnitude. High electrical conductivity of carbon and the small size of titanate crystals allowed the composite electrodes to achieve characteristic charge and discharge times comparable to that of the electric double-layer capacitors. The proposed composite synthesis methodology is simple, scalable, and applicable for a broad range of active intercalation materials, while the produced composite powders are compatible with commercial electrode fabrication processes.

Performance Enhancement and Side Reactions in Rechargeable Nickel-Iron Batteries with Nanostructured Electrodes.

We report for the first time a solution-based synthesis of strongly coupled nanoFe/multiwalled carbon nanotube (MWCNT) and nanoNiO/MWCNT nanocomposite materials for use as anodes and cathodes in rechargeable alkaline Ni-Fe batteries. The produced aqueous batteries demonstrate very high discharge capacities (800 mAh gFe(-1) at 200 mA g(-1) current density), which exceed that of commercial Ni-Fe cells by nearly 1 order of magnitude at comparable current densities. These cells also showed the lack of any "activation", typical in commercial batteries, where low initial capacity slowly increases during the initial 20-50 cycles. The use of a highly conductive MWCNT network allows for high-capacity utilization because of rapid and efficient electron transport to active metal nanoparticles in oxidized [such as Fe(OH)2 or Fe3O4] states. The flexible nature of MWCNTs accommodates significant volume changes taking place during phase transformation accompanying reduction-oxidation reactions in metal electrodes. At the same time, we report and discuss that high surface areas of active nanoparticles lead to multiple side reactions. Dissolution of Fe anodes leads to reprecipitation of significantly larger anode particles. Dissolution of Ni cathodes leads to precipitation of Ni metal on the anode, thus blocking transport of OH(-) anions. The electrolyte molarity and composition have a significant impact on the capacity utilization and cycling stability.

Graphene-Li2S-Carbon Nanocomposite for Lithium-Sulfur Batteries.

Lithium sulfide (Li2S) with a high theoretical specific capacity of 1166mAh g(-1) is a promising cathode material for next-generation Li-S batteries with high specific energy. However, low conductivity of Li2S and polysulfide dissolution during cycling are known to limit the rate performance and cycle life of these batteries. Here, we report on the successful development and application of a nanocomposite cathode comprising graphene covered by Li2S nanoparticles and protected from undesirable interactions with electrolytes. We used a modification of our previously reported low cost, scalable, and high-throughput solution-based method to deposit Li2S on graphene. A dropwise infiltration allowed us to keep the size of the heterogeneously nucleated Li2S particles smaller and more uniform than what we previously achieved. This, in turn, increased capacity utilization and contributed to improved rate performance and stability. The use of a highly conductive graphene backbone further increased cell rate performance. A synergetic combination of a protective layer vapor-deposited on the material during synthesis and in situ formed protective surface layer allowed us to retain ∼97% of the initial capacity of ∼1040 mAh gs(-1) at C/2 after over 700 cycles in the assembled cells. The achieved combination of high rate performance and ultrahigh stability is very promising.