Dong Xie

Facile fabrication of integrated three-dimensional C-MoSe2/reduced graphene oxide composite with enhanced performance for sodium storage

Scrupulous design and fabrication of advanced electrode materials are vital for developing high-performance sodium ion batteries. Herein, we report a facile one-step hydrothermal strategy for construction of a C-MoSe2/rGO composite with both high porosity and large surface area. Double modification of MoSe2 nanosheets is realized in this composite by introducing a reduced graphene oxide (rGO) skeleton and outer carbon protective layer. The MoSe2 nanosheets are well wrapped by a carbon layer and also strongly anchored on the interconnected rGO network. As an anode in sodium ion batteries, the designed C-MoSe2/rGO composite delivers noticeably enhanced sodium ion storage, with a high specific capacity of 445 mAh·g-1 at 200 mA·g-1 after 350 cycles, and 228 mAh·g-1 even at 4 A·g-1; these values are much better than those of C-MoSe2 nanosheets (258 mAh·g-1 at 200 mA·g-1 and 75 mAh·g-1 at 4 A·g-1). Additionally, the sodium ion storage mechanism is investigated well using ex situ X-ray diffraction and transmission electron microscopy methods. Our proposed electrode design protocol and sodium storage mechanism may pave the way for the fabrication of other high-performance metal diselenide anodes for electrochemical energy storage.

Nitrogen‐Doped Carbon Embedded MoS2 Microspheres as Advanced Anodes for Lithium‐ and Sodium‐Ion Batteries

Rational design and synthesis of advanced anode materials are extremely important for high-performance lithium-ion and sodium-ion batteries. Herein, a simple one-step hydrothermal method is developed for fabrication of N-C@MoS2 microspheres with the help of polyurethane as carbon and nitrogen sources. The MoS2 microspheres are composed of MoS2 nanoflakes, which are wrapped by an N-doped carbon layer. Owing to its unique structural features, the N-C@MoS2 microspheres exhibit greatly enhanced lithium- and sodium-storage performances including a high specific capacity, high rate capability, and excellent capacity retention. Additionally, the developed polyurethane-assisted hydrothermal method could be useful for the construction of many other high-capacity metal oxide/sulfide composite electrode materials for energy storage.

Encapsulating silicon nanoparticles into mesoporous carbon forming pomegranate-structured microspheres as a high-performance anode for lithium ion batteries

It is a research hotspot to develop advanced anodes with high capacity and good high-rate cyclability for lithium ion batteries. In this work, we develop a facile way to design and fabricate a silicon/carbon spherical composite by encapsulating Si nanoparticles into a mesoporous carbon matrix via a one-step hydrothermal method. Interestingly, the pomegranate structure is realized in the silicon/carbon (Si/C) composite spheres, in which Si nanoparticles of 50–100 nm are just like “pomegranate seeds” embedded into the mesoporous “pomegranate carbon chamber” with pores of 3–4 nm. This unique porous pomegranate structure can not only ensure good electrical conductivity for active Si, but also accommodate the huge volume change during cycles as well as facilitate the fast diffusion of Li ions. When evaluated as an anode for LIBs, the designed pomegranate-structured Si/C composite spheres deliver an excellent cycling stability of 581 mA h g−1 at a current density of 0.2 A g−1 after 100 cycles and achieve a noticeable high-rate capacity of 421 mA h g−1 even at a high current density of 1 A g−1, much better than those of the bare silicon electrode. Our developed facile synthetic strategy shows a new way for large-scale production of high-performance anodes for electrochemical energy storage.

Bi-functional Mo-doped WO3 nanowire array electrochromism-plus electrochemical energy storage

Metal-doping is considered to be an effective way for construction of advanced semiconducting metal oxides with tailored physicochemical properties. Herein, Mo-doped WO3 nanowire arrays are rationally fabricated by a sulfate-assisted hydrothermal method. Compared to the pure WO3, the optimized Mo-doped WO3 nanowire arrays exhibit improved electrochromic properties with fast switching speed (3.2s and 2.6s for coloration and bleaching, respectively), significant optical modulation (56.7% at 750nm, 83.0% at 1600nm and 48.5% at 10μm), high coloration efficiency (123.5cm(2)C(-1)) and excellent cycling stability. In addition, as a proof of concept, the Mo-doped WO3 nanowire arrays are demonstrated with electrochemical energy storage monitored by the electrochromism. This electrode design protocol can provide an alternative way for developing high-performance active materials for bi-functional electrochromic batteries.

Hybrid vertical graphene/lithium titanate–CNTs arrays for lithium ion storage with extraordinary performance

In the present study, we report a synthetic strategy for the direct fabrication of hybrid vertical graphene/lithium titanate–CNTs arrays via atomic layer deposition in combination with chemical vapor deposition. A novel array architecture was formed where active lithium titanate (Li4Ti5O12, LTO) was uniformly sandwiched by a vertical graphene backbone and an interconnected CNTs shell. The hybrid omnibearing conductive network was identified to be an extremely stable porous structure and demonstrated superior ultra-high rate capability (146 mA h g−1 at 50C and 131 mA h g−1 at 100C) with a capacity of 136 mA h g−1 at 20C after 10 000 cycles when used as an electrode in lithium ion batteries. This special electrode construction strategy is expected to provide a new route for the manufacture of electrochemical energy storage with ultra-high rate capability and ultra-stability.

Novel carbon channels from loofah sponge for construction of metal sulfide/carbon composites with robust electrochemical energy storage

Directional construction of highly active electrode materials plays a critical role in innovations in energy storage. One effective route to these materials is to imitate biological structures in nature. In this work, for the first time, we report the template functionability of carbon tube channels from loofah sponge. Hydrothermal MoS2 nanosheets and polymerised N-doped carbon (N-C) are rationally assembled on loofah sponge-derived carbon microtubes (LSDCM), forming ternary sandwiched composites. Due to the smart design and unique porous ternary structure, the as-prepared LSDCM/MoS2/N-C composites exhibit significantly enhanced lithium/sodium storage properties including highly reversible capacity, superior rate capability and excellent capacity retention (1058 mA h g−1 for lithium storage after 500 cycles and 534 mA h g−1 for sodium storage after 100 cycles at 0.2 A g−1). Our research not only demonstrates a novel high-quality carbon template/matrix, but also provides a new electrode design protocol for the construction of advanced metal sulfide-based electrodes for applications in electrochemical energy storage and electro-catalysis.

All-solid-state electrochromic devices based on WO 3 ‖NiO films: material developments and future applications

Electrochromism refers to the persistent and reversible change of optical properties by an applied voltage pulse. Electrochromic (EC) devices have been extensively studied because of their commercial applications in smart windows of green buildings, display devices and thermal control of equipments. In this review, a basic EC device design is presented based on useful oxides and solid-state electrolytes. We focus on the state-of-the-art research activities related to the structures of tungsten oxide (WO3) and nickel oxide (NiO), summarizing the strategies to improve their EC performances and further applications of devices.

Crystalline/amorphous tungsten oxide core/shell hierarchical structures and their synergistic effect for optical modulation

High-performance electrochromic films with large color contrast and fast switching speed are of great importance for developing advanced smart windows. In this work, crystalline/amorphous WO3 core/shell (c-WO3@a-WO3) nanowire arrays rationally are synthesized by combining hydrothermal and electrodeposition methods. The 1D c-WO3@a-WO3 core/shell hierarchical structures show a synergistic effect for the enhancement of optical modulation, especially in the infrared (IR) region. By optimizing the electrodeposition time of 400s, the core/shell array exhibits a significant optical modulation (70.3% at 750nm, 42.0% at 2000nm and 51.4% at 10μm), fast switching speed (3.5s and 4.8s), high coloration efficiency (43.2cm(2)C(-1) at 750nm) and excellent cycling performance (68.5% after 3000 cycles). The crystalline/amorphous nanostructured film can provide an alternative way for developing high-performance electrochromic materials.

Construction of Nitrogen-Doped Carbon-Coated MoSe2 Microspheres with Enhanced Performance for Lithium Storage

Exploring advanced anode materials with highly reversible capacity have gained great interests for large-scale lithium storage. A facile two-step method is developed to synthesize nitrogen-doped carbon coated MoSe2 microspheres via hydrothermal plus thermal polymerization. The MoSe2 microspheres composed of interconnected nanoflakes are homogeneously coated by a thin nitrogen-doped carbon (N-C) layer. As an anode for lithium ion batteries, the MoSe2 /N-C composite shows better reversibility, smaller polarization, and higher electrochemical reactivity as compared to the unmodified MoSe2 microspheres. The MoSe2 /N-C electrode delivers a high specific capacity of 698 mAh g-1 after 100 cycles at a current density of 100 mA g-1 and good high rate performance (471 mAh g-1 at a high current density of 2000 mA g-1 ). The improved electrochemical performance is attributed to the conductive N-C coating and hierarchical microsphere structure with fast ion/electron transfer characteristics.

Synthesis and electrochemical performance of xLiV3O8·yLi3V2(PO4)3/rGO composite cathode materials for lithium ion batteries

A series of xLiV3O8·yLi3V2(PO4)3/rGO (x : y = 2 : 1, 3 : 1, 1 : 1, 1 : 2, and 1 : 3) composites are synthesized by simple mechanical mixing of LiV3O8 and Li3V2(PO4)/rGO, which are prepared by the hydrothermal method and the sol–gel route, respectively. From scanning electron microscopy (SEM) and transmission electron microscopy (TEM) micrographs, the composites are found to be a mixture of rod-like LiV3O8 particles and flower-shaped Li3V2(PO4)/rGO. Among these composites, the 2LiV3O8·Li3V2(PO4)/rGO electrode delivers an initial discharge capacity of 197 mA h g−1 at a current density of 100 mA g−1 between 2.0 V and 4.3 V, and shows the best comprehensive electrochemical property. The diffusion coefficients of Li ions in the 2LiV3O8·Li3V2(PO4)/rGO electrode are in the range of 10−11.5 to 10−9.5 cm2 s−1 obtained using the galvanostatic intermittent titration technique (GITT).