Zhimin Bai

Superior sodium storage of novel VO2 nano-microspheres encapsulated into crumpled reduced graphene oxide

To uniformly encapsulate electrode materials with reduced graphene oxide (rGO) has been a considerable challenge due to the lack of appropriate synthetic methods and/or effective reaction systems. In this study, we present a one-step rapid and scalable solvothermal approach to achieve a crumpled reduced graphene oxide encapsulated VO2 material. As a demonstration of this promising configuration, for the first time, we systematically studied its Na+ storage behavior in the voltage range of 3.0 to 0.01 V (versus Na/Na+). It turned out that the as-prepared anode material exhibits high reversible capacities of 383 mA h g−1 at 0.1 A g−1 and 214 mA h g−1 at 4 A g−1, and can stably operate for as long as 2000 cycles at 4 A g−1 with a capacity fade of 0.013% per cycle, resulting from the improved electronic conductivity, structural stability, and electrode wettability. Furthermore, the formation mechanism and structural features of the desired crumpled reduced graphene oxide encapsulated VO2 material are discreetly expounded. More interestingly, a chain of cogent evidence is provided by coating on various electrode materials to confirm the scalability of this facile and rapid solvothermal synthesis method, which would open up a novel avenue to create more fascinating graphene-based functional materials for the multitudinous application domain.

Novel understanding of carbothermal reduction enhancing electronic and ionic conductivity of Li4Ti5O12 anode

Spinel Li4Ti5O12 performance highly depends on both the electronic and ionic conductivity, however, developing a low-cost strategy to improve its electronic and ionic conductivity still remains challenging. In this study, a facile cost-saving carbothermal reduction method is introduced to synthesize the microscaled spinel Li4Ti5O12 particles with the surface modification of Ti(III) using anatase–TiO2, Li2CO3, and acetylene black (AB) as precursors. Remarkably, this ingenious design can easily eliminate the influence of the residual carbon, and thus makes it possible to individually study the effect of the Ti(III) on the bulk Li4Ti5O12. To reveal the role of the Ti(III), the electronic conductivity and lithium-ion diffusion coefficient of the as-prepared materials were measured using a direct volt-ampere method, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). The results indicate that the carbothermal reduction leads to the increased electronic and ionic conductivity of the spinel Li4Ti5O12. As a result, the modified Li4Ti5O12 exhibits an enhanced cyclic stability, improved rate capability, and high Coulombic efficiency. The carbothermal reduction mechanism discreetly clarified in this study is beneficial to improving Li4Ti5O12 performance for further commercial applications.

Superior Cathode Performance of Nitrogen-Doped Graphene Frameworks for Lithium Ion Batteries

Development of alternative cathode materials is of highly desirable for sustainable and cost-efficient lithium-ion batteries (LIBs) in energy storage fields. In this study, for the first time, we report tunable nitrogen-doped graphene with active functional groups for cathode utilization of LIBs. When employed as cathode materials, the functionalized graphene frameworks with a nitrogen content of 9.26 at% retain a reversible capacity of 344 mAh g-1 after 200 cycles at a current density of 50 mA g-1. More surprisingly, when conducted at a high current density of 1 A g-1, this cathode delivers a high reversible capacity of 146 mAh g-1 after 1000 cycles. Our current research demonstrates the effective significance of nitrogen doping on enhancing cathode performance of functionalized graphene for LIBs.

Recent Advances in Layered Ti 3 C 2 T x MXene for Electrochemical Energy Storage

Ti3 C2 Tx , a typical representative among the emerging family of 2D layered transition metal carbides and/or nitrides referred to as MXenes, has exhibited multiple advantages including metallic conductivity, a plastic layer structure, small band gaps, and the hydrophilic nature of its functionalized surface. As a result, this 2D material is intensively investigated for application in the energy storage field. The composition, morphology and texture, surface chemistry, and structural configuration of Ti3 C2 Tx directly influence its electrochemical performance, e.g., the use of a well-designed 2D Ti3 C2 Tx as a rechargeable battery anode has significantly enhanced battery performance by providing more chemically active interfaces, shortened ion-diffusion lengths, and improved in-plane carrier/charge-transport kinetics. Some recent progresses of Ti3 C2 Tx MXene are achieved in energy storage. This Review summarizes recent advances in the synthesis and electrochemical energy storage applications of Ti3 C2 Tx MXene including supercapacitors, lithium-ion batteries, sodium-ion batteries, and lithium-sulfur batteries. The current opportunities and future challenges of Ti3 C2 Tx MXene are addressed for energy-storage devices. This Review seeks to provide a rational and in-depth understanding of the relation between the electrochemical performance and the nanostructural/chemical composition of Ti3 C2 Tx , which will promote the further development of 2D MXenes in energy-storage applications.

Vertically Aligned Co9S8 Nanotube Arrays onto Graphene Papers as High-Performance Flexible Electrodes for Supercapacitors

Paper-like electrodes are emerging as a new category of advanced electrodes for flexible supercapacitors (SCs). Graphene, a promising two-dimensional material with high conductivity, can be easily processed into papers. Here, we report a rational design of flexible architecture with Co9 S8 nanotube arrays (NAs) grown onto graphene paper (GP) via a facile two-step hydrothermal method. When employed as flexible free-standing electrode for SCs, the proposed architectured Co9 S8 /GPs exhibits superior electrochemical performance with ultrahigh capacitance and outstanding rate capability (469 F g-1 at 10 A g-1 ). These results demonstrate that the new nanostructured Co9 S8 /GPs can be potentially applied in high performance flexible supercapacitors.