Linghui Yu

Recent developments in electrode materials for sodium-ion batteries

The rapid consumption of non-renewable resources has resulted in an ever-increasing problem of CO2 emissions that has motivated people for investigating the harvesting of energy from renewable alternatives (e.g. solar and wind). Efficient electrochemical energy storage devices play a crucial role in storing harvested energies in our daily lives. For example, rechargeable batteries can store energy generated by solar cells during the daytime and release it during night-time. In particular, lithium-ion batteries (LIBs) have received considerable attention ever since their early commercialization in 1990s. However, with initiatives by several governments to build large-scale energy grids to store energy for cities, problems such as the high cost and limited availability of lithium starts to become major issues. Sodium, which also belongs to Group 1 of the periodic table, has comparable electrochemical properties to Lithium, and more importantly it is considerably more accessible than lithium. Nonetheless, research into sodium-ion batteries (NIBs) is currently still in its infancy compared to LIBs, although great leaps and bounds have been made recently in terms of research and development into this technology. Here in this review, we summarize the recent advancements made, also covering the prospective materials for both the battery cathode and anode. Additionally, opinions on possible solutions through correlating trends in recent papers will be suggested.

Achieving high performance electromagnetic wave attenuation: a rational design of silica coated mesoporous iron microcubes

Silica coated mesoporous Fe (Fe@SiO2) microcubes were designed for high performance electromagnetic wave attenuation. Silica coating lowered the permittivity significantly compared to that for bare Fe cubes. Most importantly, even with the silica coating the iron particles kept their shape which ensured a mesoporous structure. The synthetic approach consists of three steps. α-Fe2O3 microcubes were first synthesized by a hydrothermal method. Then, the cubes were coated with silica. The silica coated α-Fe2O3 microcubes were finally reduced under hydrogen gas at 500 °C. The reduction of iron oxide resulted in a removal of oxygen atoms and subsequently left the empty space as pores inside the silica coated iron cubes. The silicon resin composites containing Fe@SiO2 microcubes exhibited impressive electromagnetic wave attenuation characteristics. The reflection loss value of −54 dB could be obtained at 3.2 GHz with a thickness of 4.5 mm. In addition, the mesoporous characteristic offered a low density of Fe@SiO2 mesoporous microcubes. The microcubes enabled a reflection loss of −15 dB with a film thickness as thin as 3 mm. The silica coated mesoporous iron microcubes significantly reduced the usage/thickness of silicon resin composite. They are very promising as a strong attenuation and lightweight electromagnetic wave attenuation material.

High-performance hybrid electrochemical capacitor with binder-free Nb2O5@graphene

Hybrid electrochemical capacitors (HECs) are capable of storing more energy than supercapacitors while providing more power compared to lithium-ion batteries (LIBs). The development of Li-intercalating materials is critical to organic electrolyte based HECs, which generally give larger potential output than aqueous electrolyte based HECs. This article reports on a simple binder-free Nb2O5@graphene composite that exhibited excellent HEC performance as compared with other Li intercalating electrode materials. The composite exhibited enhanced cyclability with a capacity retention of 91.2% compared to 74.4% of the pure Nb2O5 half-cell when tested at a rate of 2000 mA g−1 (10 C). The composite displayed a lower polarization effect when cycled at increasing scan rates (1–10 mV s−1). The enhanced rate capability could be ascribed to the use of a highly conductive graphene support. As a result, the HEC composed of the Nb2O5@graphene composite and activated carbon (AC) delivered a maximum energy and power density of 29 W h kg−1 and 2.9 kW kg−1. The performance is better than most reported HECs with other Li-intercalating electrode materials.

Nanocasting synthesis of Fe3O4@HTC nanocapsules and their superior electromagnetic properties

Magnetic nanocapsules with Fe3O4 nanorods as the core and hydrothermal carbon (HTC) as the shell have been synthesized using a nanocasting method. Due to the strong shape anisotropy of the nanorods, the nanocapsules exhibit a higher coercivity and increased resonance at the high frequency range. Benefiting from the improvement of dielectric loss and magnetic loss at high frequency, the Fe3O4@HTC nanocapsule composites show superior microwave attenuation properties.

Understanding Fundamentals and Reaction Mechanisms of Electrode Materials for Na-Ion Batteries

Development of efficient, affordable, and sustainable energy storage technologies has become an area of interest due to the worsening environmental issues and rising technological dependence on Li-ion batteries. Na-ion batteries (NIBs) have been receiving intensive research efforts during the last few years. Owing to their potentially low cost and relatively high energy density, NIBs are promising energy storage devices, especially for stationary applications. A fundamental understanding of electrode properties during electrochemical reactions is important for the development of low cost, high-energy density, and long shelf life NIBs. This Review aims to summarize and discuss reaction mechanisms of the major types of NIB electrode materials reported. By appreciating how the material works and the fundamental flaws it possesses, it is hoped that this Review will assist readers in coming up with innovative solutions for designing better materials for NIBs.