Coaxial carbon/metal oxide/aligned carbon nanotube arrays as high-performance anodes for lithium ion batteries

The Use of Biochar and Pyrolysed Materials to Improve Water Quality through Microcystin Sorption Separation

Harmful algal blooms have increased globally with warming of aquatic environments and increased eutrophication. Proliferation of cyanobacteria (blue-green algae) and the subsequent flux of toxic extracellular microcystins present threats to public and ecosystem health and challenges for remediation and management. Although methods exist, there is currently a need for more environmentally friendly and economically and technologically feasible sorbents. Biochar has been proposed in this regard because of its high porosity, chemical stability, and notable sorption efficiency for removing of cyanotoxins. In light of worsening cyanobacterial blooms and recent research advances, this review provides a timely assessment of microcystin removal strategies focusing on the most pertinent chemical and physical sorbent properties responsible for effective removal of various pollutants from wastewater, liquid wastes, and aqueous solutions. The pyrolysis process is then evaluated for the first time as a method for sorbent production for microcystin removal, considering the suitability and sorption efficiencies of pyrolysed materials and biochar. Inefficiencies and high costs of conventional methods can be avoided through the use of pyrolysis. The significant potential of biochar for microcystin removal is determined by feedstock type, pyrolysis conditions, and the physiochemical properties produced. This review informs future research and development of pyrolysed materials for the treatment of microcystin contaminated aquatic environments.

Plasma production of nanomaterials for energy storage: continuous gas-phase synthesis of metal oxide CNT materials via a microwave plasma

In this work we show for the first time that a continuous plasma process can synthesize materials from bulk industrial powders to produce hierarchical structures for energy storage applications. The plasma production process's unique advantages are that it is fast, inexpensive, and scalable due to its high energy density that enables low-cost precursors. The synthesized hierarchical material is comprised of iron oxide and aluminum oxide aggregate particles and carbon nanotubes grown in situ from the iron particles. New aerosol-based methods were used for the first time on a battery material to characterize aggregate and primary particle morphologies, while showing good agreement with observations from TEM measurements. As an anode for lithium ion batteries, a reversible capacity of 870 mA h g-1 based on metal oxide mass was observed and the material showed good recovery from high rate cycling. The high rate of material synthesis (∼10 s residence time) enables this plasma hierarchical material synthesis platform to be optimized as a means for energetic material production for the global energy storage material supply chain.

High-performance symmetric supercapacitors based on carbon nanotube/graphite nanofiber nanocomposites

This work reports the nanocomposites of graphitic nanofibers (GNFs) and carbon nanotubes (CNTs) as the electrode material for supercapacitors. The hybrid CNTs/GNFs was prepared via a synthesis route that involved catalytic chemical vapor deposition (CVD) method. The structure and morphology of CNTs/GNFs can be precisely controlled by adjusting the flow rates of reactant gases. The nest shape entanglement of CNTs and GNFs which could not only have high conductivity to facilitate ion transmission, but could also increase surface area for more electrolyte ions access. When assembled in a symmetric two-electrode system, the CNTs/GNFs-based supercapacitor showed a very good cycling stability of 96% after 10 000 charge/discharge cycles. Moreover, CNTs/GNFs-based symmetric device can deliver a maximum specific energy of 72.2 Wh kg⁻¹ at a power density of 686.0 W kg⁻¹. The high performance of the hybrid performance can be attributed to the wheat like GNFs which provide sufficient accessible sites for charge storage, and the CNTs skeleton which provide channels for charge transport.

MnO2-graphene nanosheets wrapped mesoporous carbon/sulfur composite for lithium-sulfur batteries

MnO2-graphene nanosheets wrapped mesoporous carbon/sulfur (MGN@MC/S) composite is successfully synthesized derived from metal-organic frameworks and investigated as cathode for lithium-ion batteries. Used as cathode, MGN@MC/S composite possesses electronic conductivity network for redox electron transfer and strong chemical bonding to lithium polysulfides, which enables low capacity loss to be achieved. MGN@MC/S cathodes exhibit high reversible capacity of 1475 mA h g-1 at 0.1 C and an ultra-low capacity fading of 0.042% per cycle at 1 C over 450 cycles.

Novel peapoded Li4Ti5O12 nanoparticles for high-rate and ultralong-life rechargeable lithium ion batteries at room and lower temperatures

In this paper, a novel peapod-like Li4Ti5O12-C composite architecture with high conductivity is firstly designed and synthesized to be used as anode materials for lithium-ion batteries. In the synthesis, Na2Ti3O7 nanotubes act as precursors and sacrificial templates, and glucose molecules serve as the green carbon source, thus the peapod-like Li4Ti5O12-C composite can be fabricated by a facile hydrothermal reaction and the subsequent solid-state process. Compared to the previous reports, the as-prepared samples obtained by our new strategy exhibit excellent electrochemical performances, such as outstanding rate capability (an extremely reversible capability of 148 mA h g(-1), 125 mA h g(-1) at 30 C and 90 C, respectively) as well as excellent cycling performance (about 5% capacity loss after 5000 cycles at 10 C with 152 mA h g(-1) capacity retained). The low-temperature measurements also demonstrate that the electrochemical performances of the peapod-like Li4Ti5O12-C composite are remarkably improved at various rate currents (at the low-temperature of -25 °C, a high Coulombic efficiency of about 99% can be achieved after 500 cycles at 10 C).

Nanotubular Heterostructure of Tin Dioxide/Titanium Dioxide as a Binder-Free Anode in Lithium-Ion Batteries

Titanium dioxide (TiO2 ), tin dioxide (SnO2 ), and heterostructured TiO2 /SnO2 nanotube (NT) arrays have been fabricated by template-assisted atomic-layer deposition (ALD) for use as anodes in a lithium-ion battery (LIB). TiO2 NT arrays with 8 nm thick walls showed higher capacity (≈250 mA h g(-1) after the 50th cycle at a rate of C/10) than the typical theoretical capacity of bulk TiO2 and a radically improved capacity retention property upon cycling. SnO2 NT arrays with different wall thicknesses (8, 10, 13, and 20 nm) were also fabricated and their electrochemical performances were measured. All of the SnO2 NT arrays showed substantially higher initial irreversible capacity and higher reversible capacity than those of bulk TiO2 . Thinner walls of the SnO2 NTs result in better capacity retention. Heterotubular structures of TiO2 (5 nm)/SnO2 (10 nm)/TiO2 (5 nm) were successfully fabricated, and displayed a sufficiently high capacity (≈300 mA h g(-1) after 50 cycles) with exceptionally improved cycling performance up to the 50th cycle.

Boosting properties of 3D binder-free manganese oxide anodes by preformation of a solid electrolyte interphase

Huge irreversible capacity loss prevents the successful use of metal oxide anodes in Li-ion full cells. Here, we focus on the critical prelithiation step and demonstrate the challenge of electrolyte decomposition on a pristine anode in a full cell. Both an electrochemical activation process (54 h) with Li metal and a new electrolytic process (75 min) without Li metal were used to preform complete solid electrolyte interphase (SEI) layers on 3 D binder-free MnOy -based anodes. The preformed SEI layers mitigated the electrolyte decomposition effectively and widened the working voltage for the MnOy /LiMn2 O4 full cell, which resulted in a big boost of the specific energy to 300 and 200 W h kgcathode (-1) , largely improved cycling stability, and much higher specific power (4200 W h kgtotal (-1) ) compared to conventional Li-ion batteries. Detailed characterization, such as cyclic voltammetry, scanning transmission electron microscopy, and FTIR spectroscopy, gives mechanistic insight into SEI preformation. This work provides guidance for the design of anode SEI layers and enables the application of oxides for Li-ion battery full cells.