Fangyu Xiong

Porous One‐Dimensional Nanomaterials: Design, Fabrication and Applications in Electrochemical Energy Storage

Electrochemical energy storage technology is of critical importance for portable electronics, transportation and large-scale energy storage systems. There is a growing demand for energy storage devices with high energy and high power densities, long-term stability, safety and low cost. To achieve these requirements, novel design structures and high performance electrode materials are needed. Porous 1D nanomaterials which combine the advantages of 1D nanoarchitectures and porous structures have had a significant impact in the field of electrochemical energy storage. This review presents an overview of porous 1D nanostructure research, from the synthesis by bottom-up and top-down approaches with rational and controllable structures, to several important electrochemical energy storage applications including lithium-ion batteries, sodium-ion batteries, lithium-sulfur batteries, lithium-oxygen batteries and supercapacitors. Highlights of porous 1D nanostructures are described throughout the review and directions for future research in the field are discussed at the end.

Three-Dimensional Crumpled Reduced Graphene Oxide/MoS2 Nanoflowers: A Stable Anode for Lithium-Ion Batteries

Recently, layered transition-metal dichalcogenides (TMDs) have gained great attention for their analogous graphite structure and high theoretical capacity. However, it has suffered from rapid capacity fading. Herein, we present the crumpled reduced graphene oxide (RGO) decorated MoS2 nanoflowers on carbon fiber cloth. The three-dimensional framework of interconnected crumpled RGO and carbon fibers provides good electronic conductivity and facile strain release during electrochemical reaction, which is in favor of the cycling stability of MoS2. The crumpled RGO decorated MoS2 nanoflowers anode exhibits high specific capacity (1225 mAh/g) and excellent cycling performance (680 mAh/g after 250 cycles). Our results demonstrate that the three-dimensional crumpled RGO/MoS2 nanoflowers anode is one of the attractive anodes for lithium-ion batteries.

Top-down fabrication of three-dimensional porous V2O5 hierarchical microplates with tunable porosity for improved lithium battery performance

Three-dimensional porous V2O5 hierarchical microplates have been fabricated by a one-step top-down strategy, and display an excellent rate capability and stable capacity of 110 mA h g−1 at 2000 mA g−1 after 100 cycles. We have demonstrated that the facile approach of a solid-phase conversion is promising for large-scale fabrication of highly porous micro/nano materials.

Three-dimensional porous V2O5 hierarchical octahedrons with adjustable pore architectures for long-life lithium batteries

Three-dimensional (3D) porous V2O5 octahedrons have been successfully fabricated via a solid-state conversion process of freshly prepared ammonium vanadium oxide (AVO) octahedrons. The formation of AVO octahedrons is a result of the selective adsorption of capping reagents and the favourable supersaturation of growth species. Subsequently, 3D porous V2O5 octahedrons were obtained by simple thermolysis of the AVO octahedrons via a calcination treatment. As cathode material for lithium batteries, the porous V2O5 octahedron cathode exhibits a capacity of 96 mA·g−1 at high rate up to 2 A·g−1 in the rang of 2.4–4 V and excellent cyclability with little capacity loss after 500 cycles, which can be ascribed to its high specific surface area and tunable pore architecture. Importantly, this facile solid-state thermal conversion strategy can be easily extended to controllably fabricate other porous metal oxide micro/nano materials with specific surface textures and morphologies.

VO2 Nanoflakes as the Cathode Material of Hybrid Magnesium–Lithium-Ion Batteries with High Energy Density

The hybrid magnesium-lithium-ion batteries (MLIBs) combining the dendrite-free deposition of the Mg anode and the fast Li intercalation cathode are better alternatives to Li-ion batteries (LIBs) in large-scale power storage systems. In this article, we reported hybrid MLIBs assembled with the VO2 cathode, dendrite-free Mg anode, and the Mg-Li dual-salt electrolyte. Satisfactorily, the VO2 cathode delivered a stable plateau at about 1.75 V, and a high specific discharge capacity of 244.4 mA h g-1. To the best of our knowledge, the VO2 cathode displays the highest energy density of 427 Wh kg-1 among reported MLIBs in coin-type batteries. In addition, an excellent rate performance and a wide operating temperature window from 0 to 55 °C have been obtained. The combination of VO2 cathode, dual-salt electrolyte, and Mg anode would pave the way for the development of high energy density, safe, and low-cost batteries.

Robust LiTi2(PO4)3 microflowers as high-rate and long-life cathodes for Mg-based hybrid-ion batteries

Novel NASICON-type carbon-coated LiTi2(PO4)3 microflowers (LTP-F/C) as a hybrid magnesium–lithium-ion battery (MLIB) cathode is presented for the first time. Benefiting from the synergistic effect of the NASICON structure, nanosheet-constructed hierarchical architecture, and uniform carbon coating of LTP-F/C, this hybrid MLIB exhibits extraordinary electrochemical performance: ultra-high cycling stability (capacity retention of 80% after 3000 cycles at 10 C) and outstanding rate capability (94 mA h g−1 at 20 C) under a high discharge voltage plateau of ∼1.71 V (vs. Mg/Mg2+). This hybrid battery system design is highly promising for large-scale energy storage applications.

H2V3O8 Nanowires as High-Capacity Cathode Materials for Magnesium-Based Battery

Magnesium-based batteries have received much attention as promising candidates to next-generation batteries because of high volumetric capacity, low price, and dendrite-free property of Mg metal. Herein, we reported H2V3O8 nanowire cathode with excellent electrochemical property in magnesium-based batteries. First, it shows a satisfactory magnesium storage ability with 304.2 mA h g-1 capacity at 50 mA g-1. Second, it possesses a high-voltage platform of ∼2.0 V vs Mg/Mg2+. Furthermore, when evaluated as a cathode material for magnesium-based hybrid Mg2+/Li+ battery, it exhibits a high specific capacity of 305.4 mA h g-1 at 25 mA g-1 and can be performed in a wide working temperature range (-20 to 55 °C). Notably, the insertion-type ion storage mechanism of H2V3O8 nanowires in hybrid Mg2+/Li+ batteries are investigated by ex situ X-ray diffraction and Fourier transform infrared. This research demonstrates that the H2V3O8 nanowire cathode is a potential candidate for high-performance magnesium-based batteries.

Multidimensional Synergistic Nanoarchitecture Exhibiting Highly Stable and Ultrafast Sodium‐Ion Storage

Conversion-type anodes with multielectron reactions are beneficial for achieving a high capacity in sodium-ion batteries. Enhancing the electron/ion conductivity and structural stability are two key challenges in the development of high-performance sodium storage. Herein, a novel multidimensionally assembled nanoarchitecture is presented, which consists of V2 O3 nanoparticles embedded in amorphous carbon nanotubes that are then coassembled within a reduced graphene oxide (rGO) network, this materials is denoted V2 O3 ⊂C-NTs⊂rGO. The selective insertion and multiphase conversion mechanism of V2 O3 in sodium-ion storage is systematically demonstrated for the first time. Importantly, the naturally integrated advantages of each subunit synergistically provide a robust structure and rapid electron/ion transport, as confirmed by in situ and ex situ transmission electron microscopy experiments and kinetic analysis. Benefiting from the synergistic effects, the V2 O3 ⊂C-NTs⊂rGO anode delivers an ultralong cycle life (72.3% at 5 A g-1 after 15 000 cycles) and an ultrahigh rate capability (165 mAh g-1 at 20 A g-1 , ≈30 s per charge/discharge). The synergistic design of the multidimensionally assembled nanoarchitecture produces superior advantages in energy storage.

Pseudocapacitive layered birnessite sodium manganese dioxide for high-rate non-aqueous sodium ion capacitors

Layered transition metal oxides are promising cathodes for sodium ion capacitors due to their high specific capacity. In this work, we present a layered birnessite sodium manganese dioxide (Na0.77MnO2·0.5H2O) supported by a two-dimensional conductive network (denoted as b-NMO/C) as a cathode for non-aqueous sodium ion capacitor (SIC). The interlayer crystal water and carbon networks promote the ion/electron transport kinetics and overcome the structural instability, leading to largely enhanced electrochemical performance. As a result, the as-synthesized b-NMO/C cathode delivers a capacity of 192 mA h g−1 at 0.25C and 43 mA h g−1 even at a high rate of 100C. The attained performance is compared favorably with those of state-of-the-art Mn-based cathodes for sodium ion storage. Furthermore, the assembled asymmetric SIC (b-NMO/C//graphite) exhibits the highest energy (91 W h kg−1 achieved at ∼84 W kg−1) and power (5816 W kg−1 achieved at ∼37 W h kg−1) densities within the voltage range of 0.5–3.8 V.

Vanadium-Based Cathode Materials for Rechargeable Multivalent Batteries: Challenges and Opportunities

Due to the large reserves, low cost, high security and high energy density, rechargeable multivalent batteries have attracted extensive research enthusiasm for a long time. Multivalent batteries are also supposed as the potential candidates to Li-ion batteries in portable electronic devices and large-scale energy storage units. Unfortunately, most commercial cathode materials in Li-ion batteries cannot be applied in multivalent batteries because of the intensive polarization problem of multivalent intercalated ions (Mg2+, Zn2+, Al3+). Choosing and synthesizing the appropriate cathode materials are the main issues in overcoming the intensive polarization problem. Vanadium-based materials often possess many kinds of oxidation states because of the mutable vanadium element, which can facilitate achieving local electroneutrality and relieve the polarization problem of multivalent ions. In this review, we summarize the researches about the vanadium-based cathode materials for multivalent batteries and highlight the intercalation mechanism of multivalent ions to vanadium-based materials. In addition, different kinds of optimizing strategies are extracted from the literatures. On the basis of our review, progresses and future challenges of vanadium-based cathode materials in rechargeable multivalent batteries are more explicit.Graphical Abstract