Aihua Jin

Self-assembled Fe3O4 nanoparticle clusters as high-performance anodes for lithium ion batteries via geometric confinement.

Although different kinds of metal oxide nanoparticles continue to be proposed as anode materials for lithium ion batteries (LIBs), their cycle life and power density are still not suitable for commercial applications. Metal oxide nanoparticles have a large storage capacity, but they suffer from the excessive generation of solid-electrolyte interphase (SEI) on the surface, low electrical conductivity, and mechanical degradation and pulverization resulted from severe volume expansion during cycling. Herein we present the preparation of mesoporous iron oxide nanoparticle clusters (MIONCs) by a bottom-up self-assembly approach and demonstrate that they exhibit excellent cyclic stability and rate capability derived from their three-dimensional mesoporous nanostructure. By controlling the geometric configuration, we can achieve stable interfaces between the electrolyte and active materials, resulting in SEI formation confined on the outer surface of the MIONCs.

Hybrid Cellular Nanosheets for High-Performance Lithium-Ion Battery Anodes

We report a simple synthetic method of carbon-based hybrid cellular nanosheets that exhibit outstanding electrochemical performance for many key aspects of lithium-ion battery electrodes. The nanosheets consist of close-packed cubic cavity cells partitioned by carbon walls, resembling plant leaf tissue. We loaded carbon cellular nanosheets with SnO2 nanoparticles by vapor deposition method and tested the performance of the resulting SnO2-carbon nanosheets as anode materials. The specific capacity is 914 mAh g(-1) on average with a retention of 97.0% during 300 cycles, and the reversible capacity is decreased by only 20% as the current density is increased from 200 to 3000 mA g(-1). In order to explain the excellent electrochemical performance, the hybrid cellular nanosheets were analyzed with cyclic voltammetry, in situ X-ray absorption spectroscopy, and transmission electron microscopy. We found that the high packing density, large interior surface area, and rigid carbon wall network are responsible for the high specific capacity, lithiation/delithiation reversibility, and cycling stability. Furthermore, the nanosheet structure leads to the high rate capability due to fast Li-ion diffusion in the thickness direction.

Single Source Precursor-based Solvothermal Synthesis of Heteroatom-doped Graphene and Its Energy Storage and Conversion Applications

Solvothermal processes are considered efficient approaches for the gram-scale production of graphene. Further modification of graphene by chemical doping is an important approach to tailor its properties. In this work, we successfully synthesized sulfur-doped graphene by using a solvothermal method with dimethyl sulfoxide as a precursor, which is a common laboratory reagent. Nitrogen-doped graphene was produced to demonstrate the generality of this process. These heteroatom-doped graphene materials exhibited high surface areas and high contents of heteroatoms. Furthermore, the lithium-ion storage properties and oxygen reduction reaction catalytic activity of these materials were also investigated. The success of this approach might facilitate the development of other advanced graphene-based materials with relative simplicity, scalability, and cost effectiveness for use in various potential applications.

Hollow Nanostructured Metal Silicates with Tunable Properties for Lithium Ion Battery Anodes.

Hollow nanostructured materials have attracted considerable interest as lithium ion battery electrodes because of their good electrochemical properties. In this study, we developed a general procedure for the synthesis of hollow nanostructured metal silicates via a hydrothermal process using silica nanoparticles as templates. The morphology and composition of hollow nanostructured metal silicates could be controlled by changing the metal precursor. The as-prepared hierarchical hollow nanostructures with diameters of ∼100-200 nm were composed of variously shaped primary particles such as hollow nanospheres, solid nanoparticles, and thin nanosheets. Furthermore, different primary nanoparticles could be combined to form hybrid hierarchical hollow nanostructures. When hollow nanostructured metal silicates were applied as anode materials for lithium ion batteries, all samples exhibited good cyclic stability during 300 cycles, as well as tunable electrochemical properties.

Bismuth oxide as a high capacity anode material for sodium-ion batteries

A bismuth oxide electrode, delivering high capacity, as an anode material for sodium-ion batteries was simply prepared. The electrochemical properties of bismuth oxide were studied by operando X-ray absorption near edge structure spectroscopy and ex situ X-ray diffraction methods. A bismuth oxide/carbon composite showed enhanced cycle stability at high current densities.

Facile synthesis of metal hydroxide nanoplates and their application as lithium-ion battery anodes

We report a facile approach to synthesize hexagon-shaped nanoplates of various metal (oxy)hydroxides under aqueous solutions while avoiding complex processes. This synthetic method can be generally applied to fabricate various nanoplates, including not only single-metallic (oxy)hydroxides such as Co(OH)2, MnO(OH), FeO(OH), and Mg(OH)2 but also mixed-metal (oxy)hydroxides, where each metal component is homogeneously distributed and the atomic ratio of the metal species can be easily controlled by varying the precursor ratio. Carbon-coated metal oxide nanoplates, which are prepared by coating of polydopamine followed by heat treatment, are applied as anode materials for lithium-ion batteries (LIB). Core–shell nanoplates of CoO@C, MnO@C and Fe3O4@C exhibit excellent cycle stability with a high specific capacity of ∼1000 mA h g−1. In particular, the effect of carbon shell thickness on electrochemical performance is studied using CoO@C nanoplates with different carbon shell thicknesses. CoO@C with a 6.5 nm-thick carbon coating exhibits good cycling performance and maintains a high rechargeable capacity of 997 mA h g−1 even after 100 cycles at a current density of 200 mA g−1, while CoO@C with a 1.5 nm-thick carbon shell shows a significantly decreased capacity of 315 mA h g−1 after the 100th cycle.

Na+/Vacancy Disordered P2-Na0.67Co1–xTixO2: High-Energy and High-Power Cathode Materials for Sodium Ion Batteries

Although sodium ion batteries (NIBs) have gained wide interest, their poor energy density poses a serious challenge for their practical applications. Therefore, high-energy-density cathode materials are required for NIBs to enable the utilization of a large amount of reversible Na ions. This study presents a P2-type Na0.67Co1-xTixO2 (x < 0.2) cathode with an extended potential range higher than 4.4 V to present a high specific capacity of 166 mAh g-1. A group of P2-type cathodes containing various amounts of Ti is prepared using a facile synthetic method. These cathodes show different behaviors of the Na+/vacancy ordering. Na0.67CoO2 suffers severe capacity loss at high voltages due to irreversible structure changes causing serious polarization, while the Ti-substituted cathodes have long credible cycleability as well as high energy. In particular, Na0.67Co0.90Ti0.10O2 exhibits excellent capacity retention (115 mAh g-1) even after 100 cycles, whereas Na0.67CoO2 exhibits negligible capacity retention (<10 mAh g-1) at 4.5 V cutoff conditions. Na0.67Co0.90Ti0.10O2 also exhibits outstanding rate capabilities of 108 mAh g-1 at a current density of 1000 mA g-1 (7.4 C). Increased sodium diffusion kinetics from mitigated Na+/vacancy ordering, which allows high Na+ utilization, are investigated to find in detail the mechanism of the improvement by combining systematic analyses comprising TEM, in situ XRD, and electrochemical methods.

Two-dimensional assemblies of ultrathin titanate nanosheets for lithium ion battery anodes

Ultrathin titanate nanosheets of 0.5 nm thickness were successfully synthesized from the non-hydrolytic sol–gel reaction of tetraoctadecyl orthotitanate via a heat-up method. The synthesized nanosheets were easily assembled to be layer structures by being reacted with hydroxide ions in basic solutions such as LiOH, NaOH, and KOH. The hydrophobic surface of the titanate nanosheets was also modified to be a hydrophilic surface through an assembly process. The layer structured nanosheets were employed as anode materials for lithium ion batteries to visualize fast charging and discharging effects utilizing 2D structured electrodes, and stable cycling induced the mechanically stable layered structure. The ultrathin morphology of the 2D titanate electrodes affected not only the diffusion path of Li ions but also the reaction mechanism from the insertion reaction of the crystal interior to the surface reaction. Furthermore, the electrodes of the layer structured nanosheets had superior cycling and rate performances.

Facile synthesis of nanostructured carbon nanotube/iron oxide hybrids for lithium-ion battery anodes

Nanostructured carbon nanotubes/iron oxide hybrids (CNIOHs) were synthesized by a scalable Bake-Break-Mix process which involves three simple steps. Porous rod-like iron oxide arrays were first synthesized via the decomposition of iron(II) oxalate dihydrate at 300 °C for 5 h. The prepared rod-like structures were simply a well-organized alignment of numerous iron oxide nanoparticles. Breaking these rod-shaped iron oxide arrays into well-dispersed nanoparticles was accomplished by ultrasonication. Finally, single-wall carbon nanotubes were added to the suspension during sonication which allowed the dispersed iron oxide nanoparticles to adsorb to the surface resulting in the nanostructured CNIOHs. CNIOHs were employed as anode materials and showed excellent capacity, cyclic stability and rate capability.

Solvothermal-Derived S-Doped Graphene as an Anode Material for Sodium-Ion Batteries

Abstract Sodium‐ion batteries (SIBs) have attracted enormous attention in recent years due to the high abundance and low cost of sodium. However, in contrast to lithium‐ion batteries, conventional graphite is unsuitable for SIB anodes because it is much more difficult to intercolate the larger Na ions into graphite layers. Therefore, it is critical to develop new anode materials for SIBs for practical use. Here, heteroatom‐doped graphene with high doping levels and disordered structures is prepared using a simple and economical thermal process. The solvothermal‐derived graphene shows excellent performance as an anode material for SIBs. It exhibits a high reversible capacity of 380 mAh g−1 after 300 cycles at 100 mA g−1, excellent rate performance 217 mAh g−1 at 3200 mA g−1, and superior cycling performance at 2.0 A g−1 during 1000 cycles with negligible capacity fade.