Templated Synthesis of SiO2 Nanotubes for Lithium-Ion Battery Applications: An In Situ (Scanning) Transmission Electron Microscopy Study

One of the weaknesses of silicon-based batteries is the rapid deterioration of the charge-storage capacity with increasing cycle numbers. Pure silicon anodes tend to suffer from poor cycling ability due to the pulverization of the crystal structure after repeated charge and discharge cycles. In this work, we present the synthesis of a hollow nanostructured SiO₂ material for lithium-ion anode applications to counter this drawback. To improve the understanding of the synthesis route, the crucial synthesis step of removing the ZnO template core is shown using an in situ closed gas-cell sample holder for transmission electron microscopy. A direct visual observation of the removal of the ZnO template from the SiO₂ shell is yet to be reported in the literature and is a critical step in understanding the mechanism by which these hollow nanostructures form from their core-shell precursors for future electrode material design. Using this unique technique, observation of dynamic phenomena at the individual particle scale is possible with simultaneous heating in a reactive gas environment. The electrochemical benefits of the hollow morphology are demonstrated with exceptional cycling performance, with capacity increasing with subsequent charge-discharge cycles. This demonstrates the criticality of nanostructured battery materials for the development of next-generation Li⁺-ion batteries.

A free-standing 3D porous all-ceramic cathode for high capacity, long cycle life Li-O2 batteries

The all-ceramic RuO₂@La_0.7Ca_0.3CuO₃ membrane cathode contributes to an ultra-high capacity of 21 518 mA h g^-1 over 110 cycles in Li-O₂ batteries. A simple infiltration technique is effective for obtaining a highly active supported RuO₂ catalyst, and a solvent with a high donor number should be preferentially chosen because it contributes to a much higher capacity.

A High-Surface-Area Carbon-Coated 3D Nickel Nanomesh for Li-O2 Batteries

Nanostructured electrodes show great promises for application in batteries and could improve their energy and power density. Herein, a carbon-coated 3D Ni nanomesh was used as an air cathode for non-aqueous Li-air (O₂ ) battery applications. A 3 μm thick 3D Ni nanomesh was fabricated, showing an excellent surface area/footprint area ratio (90 cm² :1 cm² ) and uniformly distributed pores, on which a conformal amorphous carbon coating was applied for the first time. This carbon-coated 3D Ni nanomesh showed an approximately 100 times larger charge-footprint capacity than that of the glassy carbon electrode. Owing to its tunable properties, a capacity higher than 6 mAh cm^-2 could be achieved for a carbon-coated 3D Ni nanomesh with a thickness of 100 μm, whereas the practical capacities of current air electrodes are in the range of 2 mAh cm^-2 .

High-Potential Metalless Nanocarbon Foam Supercapacitors Operating in Aqueous Electrolyte

Light-weight graphite foam decorated with carbon nanotubes (dia. 20-50 nm) is utilized as an effective electrode without binders, conductive additives, or metallic current collectors for supercapacitors in aqueous electrolyte. Facile nitric acid treatment renders wide operating potentials, high specific capacitances and energy densities, and long lifespan over 10 000 cycles manifested as 164.5 and 111.8 F g^-1 , 22.85 and 12.58 Wh kg^-1 , 74.6% and 95.6% capacitance retention for 2 and 1.8 V, respectively. Overcharge protection is demonstrated by repetitive cycling between 2 and 2.5 V for 2000 cycles without catastrophic structural demolition or severe capacity fading. Graphite foam without metallic strut possessing low density (≈0.4-0.45 g cm^-3 ) further reduces the total weight of the electrode. The thorough investigation of the specific capacitances and coulombic efficiencies versus potential windows and current densities provides insights into the selection of operation conditions for future practical devices.

Fe-based hybrid electrocatalysts for nonaqueous lithium-oxygen batteries

Lithium–oxygen batteries promise high energy densities, but are confronted with challenges, such as high overpotentials and sudden death during discharge–charge cycling, because the oxygen electrode is covered with the insulating discharge product, Li₂O₂. Here, we synthesized low–cost Fe–based nanocomposites via an electrical wire pulse process, as a hybrid electrocatalyst for the oxygen electrode of Li–O₂ batteries. Fe₃O₄-Fe nanohybrids–containing electrodes exhibited a high discharge capacity (13,890 mA h g_c⁻¹ at a current density of 500 mA g_c⁻¹), long cycle stability (100 cycles at a current rate of 500 mA g_c⁻¹ and fixed capacity regime of 1,000 mA h g_c⁻¹), and low overpotential (1.39 V at 40 cycles). This superior performance resulted from the good electrical conductivity of the Fe metal nanoparticles during discharge–charge cycling, which could enhance the oxygen reduction reaction and oxygen evolution reaction activities. We have demonstrated the increased electrical conductivity of the Fe₃O₄-Fe nanohybrids using electrochemical impedance spectroscopy.

Silicon Derived from Glass Bottles as Anode Materials for Lithium Ion Full Cell Batteries

Every year many tons of waste glass end up in landfills without proper recycling, which aggravates the burden of waste disposal in landfill. The conversion from un-recycled glass to favorable materials is of great significance for sustainable strategies. Recently, silicon has been an exceptional anode material towards large-scale energy storage applications, due to its extraordinary lithiation capacity of 3579 mAh g-1 at ambient temperature. Compared with other quartz sources obtained from pre-leaching processes which apply toxic acids and high energy-consuming annealing, an interconnected silicon network is directly derived from glass bottles via magnesiothermic reduction. Carbon-coated glass derived-silicon (gSi@C) electrodes demonstrate excellent electrochemical performance with a capacity of ~1420 mAh g-1 at C/2 after 400 cycles. Full cells consisting of gSi@C anodes and LiCoO2 cathodes are assembled and achieve good initial cycling stability with high energy density.

Kinetics and electrochemical evolution of binary silicon–polymer systems for lithium ion batteries

The kinetics and evolution of binary silicon–polymer systems have been systematically studied for electrochemical energy storage.