Boosting the lithium and sodium storage performance of graphene-based composite via pore engineering and surface protection.

Transition metal oxides with high theoretical capacities are widely investigated as potential anodes for alkali-metal ion batteries. However, the intrinsic conductivity deficiency and large volume changes during cycles result in poor cycling stability and low rate capabilities. Graphene has been widely used to support metal oxide for enhanced performance, but the cycling life is limited by the aggregation/collapse of active materials on graphene surface. Herein, we significantly improve the battery performance of graphene-metal oxide composite via pore engineering and surface protection. In this architecture, the mesoporous NiFe2O4 is designed for fast ion diffusion and volume accommodation, and the outer graphene protection can further enhance the electrical conductivity and prevent the aggregation during cycle. Thus, as-prepared G@p-NiFe2O4@G composite for lithium storage delivers high capacity (1244 mA h g-1 after 300 cycles at 0.2 A g-1), excellent rate performance (563 mA h g-1 at 4 A g-1), and outstanding cycling life up to 1200 cycles at 1.5 A g-1. For sodium storage, it also displays good cycling stability and superior rate performance. Moreover, the effects of various microstructures on the battery performance, the reaction kinetics of various electrodes, and the reaction mechanism of NiFe2O4 have been systematically investigated in this work.

Shifting Oxygen Charge Towards Octahedral Metal: A Way to Promote Water Oxidation on Cobalt Spinel Oxides.

Cobalt spinel oxides are a class of promising transition metal (TM) oxides for catalyzing oxygen evolution reaction (OER). Their catalytic activity depends on the electronic structure. In a spinel oxide lattice, each oxygen anion is shared amongst its four nearest transition metal cations, of which one is located within the tetrahedral interstices and the remaining three cations are in the octahedral interstices. This work uncovered the influence of oxygen anion charge distribution on the electronic structure of the redox-active building block Co-O. The charge of oxygen anion tends to shift toward the octahedral-occupied Co instead of tetrahedral-occupied Co, which hence produces strong orbital interaction between octahedral Co and O. Thus, the OER activity can be promoted by pushing more Co into the octahedral site or shifting the oxygen charge towards the redox-active metal center in CoO6 octahedra.

Biomass-Derived Porous Carbon-Based Nanostructures for Microwave Absorption.

Currently, electromagnetic (EM) pollution poses severe complication toward the operation of electronic devices and biological systems. To this end, it is pertinent to develop novel microwave absorbers through compositional and structural design. Porous carbon (PC) materials demonstrate great potential in EM wave absorption due to their ultralow density, large surface area, and excellent dielectric loss ability. However, the large-scale production of PC materials through low-cost and simple synthetic route is a challenge. Deriving PC materials through biomass sources is a sustainable, ubiquitous, and low-cost method, which comes with many desired features, such as hierarchical texture, periodic pattern, and some unique nanoarchitecture. Using the bio-inspired microstructure to manufacture PC materials in mild condition is desirable. In this review, we summarize the EM wave absorption application of biomass-derived PC materials from optimizing structure and designing composition. The corresponding synthetic mechanisms and development prospects are discussed as well. The perspective in this field is given at the end of the article.

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.

Novel Preparation of N-Doped SnO2 Nanoparticles via Laser-Assisted Pyrolysis: Demonstration of Exceptional Lithium Storage Properties.

Laser pyrolyzed SnO2 nanoparticles with an option of nitrogen (N) doping are prepared using a cost-effective method. The electrochemical performance of N-doped samples is tested for the first time in Li-ion batteries where the sample with 3% of N-dopant exhibits optimum performance with a capacity of 522 mAh gactive material-1 that can be obtained at 10 A g-1 (6.7C).

Reserving Interior Void Space for Volume Change Accommodation: An Example of Cable-Like MWNTs@SnO2@C Composite for Superior Lithium and Sodium Storage.

Reserving interior void space in the cable-like structure of multiwalled carbon nanotubes-in-SnO2-in-carbon layer (MWNTs@SnO2@C) is reported for the first time. Such a design enables the structure performing excellent for Li and Na storage, which benefit from the good electrical conductivity of MWNTs and carbon layer as well as the reserved void space to accommodate the volume changes of SnO2.