Anqiang Pan

Template free synthesis of LiV3O8 nanorods as a cathode material for high-rate secondary lithium batteries

A novel, template-free, low-temperature method has been developed to synthesize LiV3O8 cathode material for high-power secondary lithium (Li) batteries. The LiV3O8 prepared using this new method was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The thermal decomposition process was investigated using thermogravimetric (TG) and differential thermal analysis (DTA). LiV3O8 produced using the conventional high-temperature fabrication method also was analyzed. The electrochemical performances and the effects of synthesis temperature on our LiV3O8 and the conventionally produced LiV3O8 were compared. The LiV3O8 produced using our new method has a nanorod crystallite structure composed of uniform, well-separated particles with diameters ranging from 30 to 150 nm. The TEM work reveals the stacking defaults within the nanorod structures, which would facilitate the electron transportation during the insertion and removal process of lithium ions. It delivers specific discharge capacities of 320 mAh g−1 and 239 mAh g−1 at current densities of 100 mA g−1 and 1 A g−1, respectively. It also exhibits excellent capacity retention with only 0.23% capacity fading per cycle. This excellent electrochemical performance can be attributed to the superior structural characteristics of our material, and the results of our study demonstrate that LiV3O8 nanorod crystallites produced by this new thermal decomposition method are promising cathode materials for high-power Li batteries.

V2O5 xerogel electrodes with much enhanced lithium-ion intercalation properties with N2annealing

V2O5 xerogel films were fabricated by casting V2O5 sols onto FTO glass substrates and annealing at 300 °C for 3 hours in nitrogen and air. The films annealed in nitrogen and air possessed different grain size and crystallinity. Optical absorption measurements and electrochemical impedance analyses revealed a reduced optical bandgap and enhanced electrical conductivity of N2 annealed V2O5 film. Lithium ion intercalation measurements showed that at a charge/discharge current density of 600 mAg−1, the N2 annealed sample possessed noticeably better lithium ion storage capability. In contrast to the air annealed sample, which started with a discharge capacity of 152 mAhg−1 but after 50 cycles the capacity had decreased to a low value of only 44 mAhg−1, the N2 annealed sample started with a low value of 68 mAhg−1 but the capacity increased sharply to a high value of 158 mAhg−1 at the 24th cycle, followed by little capacity degradation in later cycles and after 50 cycles, the discharge capacity was still as high as 148 mAhg−1. Much improved lithium ion intercalation capacity and cyclic stability could be attributed to surface defects V4+ and/or V3+ and associated oxygen vacancies introduced by N2annealing as well as much less crystallized vanadium oxide.

Nanosheet-structured LiV3O8 with high capacity and excellent stability for high energy lithium batteries

Highly stable LiV3O8 with a nanosheet-structure was successfully prepared using polyethylene glycol (PEG) polymer in the precursor solution as the structure modifying agent, followed by calcination in air at 400 °C, 450 °C, 500 °C, and 550 °C. These materials provide the best electrochemical performance ever reported for LiV3O8 crystalline electrodes, with a specific discharge capacity of 260 mAh g−1 and no capacity fading over 100 cycles at 100 mA g−1. The excellent cyclic stability and high specific discharge capacity of the material are attributed to the novel nanosheets structure formed in LiV3O8. These LiV3O8 nanosheets are good candidates for cathode materials for high-energy lithium battery applications.

Nitrogen-Doped Yolk–Shell-Structured CoSe/C Dodecahedra for High-Performance Sodium Ion Batteries

In this work, nitrogen-doped, yolk-shell-structured CoSe/C mesoporous dodecahedra are successfully prepared by using cobalt-based metal-organic frameworks (ZIF-67) as sacrificial templates. The CoSe nanoparticles are in situ produced by reacting the cobalt species in the metal-organic frameworks with selenium (Se) powder, and the organic species are simultaneously converted into nitrogen-doped carbon material in an inert atmosphere at temperatures between 700 and 900 °C for 4 h. For the composite synthesized at 800 °C, the carbon framework has a relatively higher extent of graphitization, with high nitrogen content (17.65%). Furthermore, the CoSe nanoparticles, with a size of around 15 nm, are coherently confined in the mesoporous carbon framework. When evaluated as novel anode materials for sodium ion batteries, the CoSe/C composites exhibit high capacity and superior rate capability. The composite electrode delivers the specific capacities of 597.2 and 361.9 mA h g-1 at 0.2 and 16 A g-1, respectively.

Two-dimensional hybrid nanosheets of few layered MoSe2 on reduced graphene oxide as anodes for long-cycle-life lithium-ion batteries

A rational design of two-dimensional (2D) hybrid materials between transition metal dichalcogenides (TMDs) and graphene has received great attention because of their promising applications in the energy field. Herein, we report the synthesis of novel 2D hybrid nanosheets constructed by few layered MoSe2 grown on reduced graphene oxide (rGO). As a proof-of-concept application, the 2D MoSe2/rGO nanosheets exhibit excellent electrochemical performance as anodes for lithium ion batteries, demonstrating outstanding cycling stability (up to 1000 cycles), and high-rate capability.

PVP-assisted synthesis of MoS2 nanosheets with improved lithium storage properties

An efficient and scalable strategy has been developed for the synthesis of MoS2 nanosheets employing PVP as a surfactant. The MoS2 nanosheets exhibit an enhanced lithium intercalation capacity, cyclic stability and rate capability.

Nitrogen-doped TiO2 nanospheres for advanced sodium-ion battery and sodium-ion capacitor applications

Sodium-ion batteries (NIBs) and sodium-ion capacitors (NICs) are considered to be promising energy storage systems for applications in future hybrid electric vehicles (HEVs) and electric vehicles (EVs) because of the low cost and abundance of Na. Herein, NIBs and NICs based on nitrogen-doped TiO2 (referred to as N-TiO2) nanospheres as anode materials were analyzed. The N-TiO2 nanospheres exhibited a stable capacity of 162 mA h g−1 over 1000 cycles at 1 A g−1, as well as a superior rate performance in NIBs. In NICs, the N-TiO2//AC device displayed a high energy density of ∼80.3 W h kg−1, a high power density of ∼12 500 W kg−1, and excellent long-term cycling stability for up to 6500 cycles.

Ultrathin Na1.1V3O7.9 Nanobelts with Superior Performance as Cathode Materials for Lithium-Ion Batteries

The Na1.1V3O7.9 nanobelts have been synthesized by a facile and scalable hydrothermal reaction with subsequent calcinations. The morphologies and the crystallinity of the nanobelts are largely determined by the calcination temperatures. Ultrathin nanobelts with a thickness around 20 nm can be obtained, and the TEM reveals that the nanobelts are composed of many stacked thinner belts. When evaluated as a cathode material for lithium batteries, the Na1.1V3O7.9 nanobelts exhibit high specific capacity, good rate capability, and superior long-term cyclic stability. A high specific capacity of 204 mA h g(-1) can be delivered at the current density of 100 mA g(-1). It shows excellent capacity retention of 95% after 200 cycles at the current density of 1500 mA g(-1). As demonstrated by the ex situ XRD results, the Na1.1V3O7.9 nanobelts have very good structural stability upon cycling. The superior electrochemical performances can be attributed to the ultra-thin nanobelts and the good structural stability of the Na1.1V3O7.9 nanobelts.

Metal–organic framework-templated two-dimensional hybrid bimetallic metal oxides with enhanced lithium/sodium storage capability

Two-dimensional (2D) porous hybrid bimetallic transition metal oxide (TMO) nanosheets demonstrated promising applications in the energy field due to their large surface areas, porous structure, and synergistic effects. However, the synthesis of these materials is still a big challenge. In this study, we rationally designed a facile strategy to prepare 2D porous hybrid bimetallic TMO (Co3O4/ZnO) nanosheets with novel structural and electrochemical synergistic effects. Derived from bimetallic MOF nanosheets, the porous hybrid nanosheets possess high surface areas and large pore volume. In particular, they are rich in oxygen vacancies, which provide more active sites for electrochemical reaction. Moreover, the harmonious multi-step conversion reaction between Co3O4 and ZnO was helpful for volume buffering, leading to an outstanding cyclic stability. With remarkable structural features and harmonious electrochemical behaviors, the Co3O4/ZnO hybrids exhibit excellent electrochemical performances as anodes for both lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). This study also introduces a new strategy to prepare 2D porous hybrid bimetallic TMO nanosheets, which can find wide applications in energy storage, catalysis, sensors, and information storage devices.

Synthesis of Na1.25V3O8 Nanobelts with Excellent Long-Term Stability for Rechargeable Lithium-Ion Batteries

Sodium vanadium oxide (Na1.25V3O8) nanobelts have been successfully prepared by a facile sol-gel route with subsequent calcination. The morphologies and the crystallinity of the as-prepared Na1.25V3O8 nanobelts can be easily controlled by the calcination temperatures. As cathode materials for lithium ion batteries, the Na1.25V3O8 nanobelts synthesized at 400 °C exhibit a relatively high specific discharge capacity of 225 mA h g(-1) and excellent stability at 100 mA g(-1). The nanobelt-structured electrode can retain 94% of the initial capacity even after 450 cycles at the current density of 200 mA g(-1). The good electrochemical performance is attributed to their nanosized thickness and good crystallinity. The superior electrochemical performance demonstrates the Na1.25V3O8 nanobelts are promising cathode materials for secondary lithium batteries.