Lead recovery from spent lead acid battery paste by hydrometallurgical conversion and thermal degradation.

Spent lead paste is the main component in lead-acid batteries reaching end of life. It contains about 55% lead sulphate and 35% lead dioxide, as well as minor amounts of lead oxide. It is necessary to recycle spent lead paste with minimal pollution and low energy consumption instead of the conventional smelting method. In this study, a novel approach involving hydrometallurgical desulphurisation and thermal degradation is developed to recover lead as PbO products from spent lead acid batteries. First, the desulphurisation effects and phase compositions of products with different transforming agents were compared, and the optimum conditions using (NH4)2CO3 as a transforming agent were determined. And then, the thermal degradation processes of both precursors lead carbonate and lead dioxide were investigated to prepare α-PbO, Pb3O4, and ß-PbO products in argon and air atmospheres, respectively. Both the desulphurisation precursors and the calcination products were characterised by thermogravimetry and differential scanning calorimetry, X-ray diffraction, and scanning electron microscopy. The results showed that the lead oxide products were prepared, including α-PbO at 450°C in argon, Pb3O4 and ß-PbO at 480°C and 620°C in air, respectively.

A High Performance Polyacrylonitrile Composite Separator with Cellulose Acetate and Nano-Hydroxyapatite for Lithium-Ion Batteries.

The traditional commercial polyolefin separators suffer from high-temperature thermal shrinkage, low electrolyte wettability and other issues. In order to improve the overall performance of the separators, electrostatic spinning technology was applied to obtain PAN nanofiber separators with an average diameter of 320 nm. Then cellulose acetate (CA) resin and nano-hydroxyapatite (HAP) were introduced to fabricate the PAN/CA/HAP composite separators through the constant temperature hot pressing and dip-coating crafts. The composite separator has a good thermal stability, with no significant dimensional change after a constant temperature treatment of 200 °C for 35 min. The electrolyte uptake rate of the PAN/CA/HAP-1.0 composite separator reaches 281%, which exhibits an efficient ionic conductivity. At the same time, it also attains a tensile strength of 11.18 MPa, which meets the requirement for separator use. Button cells assembled from PAN/CA/HAP-1.0 composite separators have an excellent rate of performance (160.42 mAh·g-1 at 0.2 C) and cycle capability (157.6 mAh·g-1 after 50 cycles at 0.5 C). The results support that lithium-ion batteries assembled with PAN/CA/HAP-1.0 composite separators will exhibit higher safety stability and better electrochemical performance than that of polyolefin separators, with a very immense potential for application.

PbSe/CdSe and PbSe/CdSe/ZnSe hierarchical nanocrystals and their photoluminescence.

Multiple CdSe and ZnSe semiconductor shells were grown on PbSe semiconductor spherical cores with monolayer control. For CdSe shell coating, we found that there was little room to further increase the quantum yields of freshly-made high-quality PbSe nanocrystals that already owned very high initial values because of their good surface status; but there was great improvement for the PbSe nanocrystals with low initial quantum yields because of the poor surface status. Nonetheless, the quantum yield for the latter case could not reach the former's value. Additional ZnSe shells on PbSe/CdSe could further increase the quantum yield and protect the nanocrystals from air oxidation. The observed phenomena in the synthesis of the PbSe/CdSe and PbSe/CdSe/ZnSe core/shell structures were explained through the carrier wave function expansion and the surface polarization.

A Novel Electrospinning Polyacrylonitrile Separator with Dip-Coating of Zeolite and Phenoxy Resin for Li-ion Batteries.

Commercial separators (polyolefin separators) for lithium-ion batteries still have defects such as low thermostability and inferior interface compatibility, which result in serious potential safety distress and poor electrochemical performance. Zeolite/Polyacrylonitrile (Z/PAN) composite separators have been fabricated by electrospinning a polyacrylonitrile (PAN) membrane and then dip-coating it with zeolite (ZSM-5). Different from commercial separators, the Z/PAN composite separators exhibit high electrolyte uptake, excellent ionic conductivity, and prominent thermal stability. Specifically, the Z/PAN-1.5 separator exhibits the best performance, with a high electrolyte uptake of 308.1% and an excellent ionic conductivity of 2.158 mS·cm-1. The Z/PAN-1.5 separator may mechanically shrink less than 10% when held at 180 °C for 30 min, proving good thermal stability. Compared with the pristine PAN separator, the Li/separator/LiFePO4 cells with the Z/PAN-1.5 composite separator have excellent high-rate discharge capacity (102.2 mAh·g-1 at 7 C) and favorable cycling performance (144.9 mAh·g-1 at 0.5 C after 100 cycles). Obviously, the Z/PAN-1.5 separator holds great promise in furthering the safety and performance of lithium-ion batteries.

Design of A High Performance Zeolite/Polyimide Composite Separator for Lithium-Ion Batteries.

A zeolite/polyimide composite separator with a spongy-like structure was prepared by phase inversion methods based on heat-resistant polyimide (PI) polymer matrix and ZSM-5 zeolite filler, with the aim to improve the thermal stability and electrochemical properties of corresponding batteries. The separator exhibits enhanced thermal stability and no shrinkage up to 180 °C. The introduction of a certain number of ZSM-5 zeolites endows the composite separator with enhanced wettability and electrolyte uptake, better facilitating the free transport of lithium-ion. Furthermore, the composite separator shows a high ionic conductivity of 1.04 mS cm-1 at 25 °C, and a high decomposition potential of 4.7 V. Compared with the PP separator and pristine PI separator, the ZSM-5/PI composite separator based LiFePO4/Li cells have better rate capability (133 mAh g-1 at 2 C) and cycle performance (145 mAh g-1 at 0.5 C after 50 cycles). These results demonstrate that the ZSM-5/PI composite separator is promising for high-performance and high-safety lithium-ion batteries.

Fabrication of protein nanotubes using template-assisted electrostatic layer-by-layer methods.

One-dimensional protein nanostructures offer many advantages for biomedical applications. Rather than fabricate primary nanostructures with inorganic materials and then functionalize with proteins, it is desirable to develop a fabrication method to make nanostructures that are entirely protein. Fabrication of protein and polymer nanostructures is possible by layer-by-layer assembly within nanoporous templates. Typically these structures are composites of two or more materials. Few studies have demonstrated the fabrication of single component protein nanostructures using this method. In this paper, we report our effort toward the fabrication of single-component avidin nanotubes using a layer-by-layer electrostatic assembly method adapted from the literature. We investigated the use of two different template pretreatment methods to strengthen the attraction between the initial protein layer and our template. During our investigation, we revealed a significant flaw with the published works upon which our fabrication method was based which seriously compromised the legitimacy of the approach. As a result, we modified our initial method, and we are able to demonstrate the fabrication of glucose oxidase/avidin nanostructures using an electrostatic layer-by-layer assembly in conjunction with one of the template pretreatment methods we investigated.

Fabrication of free-standing Cu nanorod arrays on Cu disc by template-assisted electrodeposition.

Free-standing Cu nanorod arrays on Cu foil have been fabricated by a template-assisted method. Cu nanorods were potentiostatically deposited on mechanically polished Cu foil using anodized aluminum oxide templates as the deposition mask. Three electrolyte systems were compared, including two acid copper sulfate based solutions and one alkaline solution. The most uniform nanorods were achieved in the alkaline electrolyte. The weight gain per unit area after electrodeposition has been used as a direct measure of average length of deposited Cu nanorods. It was found that our control over the uniformity in nanorod length across the array is important in reaching the maximized aspect ratio without aggregation. Through controlling the weight change it was possible to control the aspect ratio of nanorods and to avoid aggregation of nanorods. Our capability to fabricate free-standing Cu nanorod arrays of uniform height with maximized aspect ratio on Cu foil is especially important in applying this nanostructured Cu as a current collector in Li ion batteries.