Wangjia Tang

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.

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.

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.

Metal-Embedded Porous Graphitic Carbon Fibers Fabricated from Bamboo Sticks as a Novel Cathode for Lithium–Sulfur Batteries

Lithium-sulfur batteries (LSBs) are deemed to be among the most prospective next-generation advanced high-energy batteries. Advanced cathode materials fabricated from biological carbon are becoming more popular due to their unique properties. Inspired by the fibrous structure of bamboo, herein we put forward a smart strategy to convert bamboo sticks for barbecue into uniform bamboo carbon fibers (BCF) via a simple hydrothermal treatment proceeded in alkaline solution. Then NiCl2 is used to etch the fibers through a heat treatment to achieve Ni-embedded porous graphitic carbon fibers (PGCF/Ni) for LSBs. The designed PGCF/Ni/S electrode exhibits improved electrochemical performances including high initial capacity (1198 mAh g-1 at 0.2 C), prolonged cycling life (1030 mAh g-1 at 0.2 C after 200 cycles), and improved rate capability. The excellent properties are attributed to the synergistic effect of 3D porous graphitic carbon fibers with highly conductive Ni nanoparticles embedded.

Hierarchical MoS2/Carbon Composite Microspheres as Advanced Anodes for Lithium/Sodium-Ion Batteries

It is crucial to design advanced electrodes with large Li/Na-ion storage capacities for the development of next-generation battery systems. Herein, hierarchical MoS2 /C composite microspheres were constructed by facile template-free self-assembly sulfurization plus post-carbonization. Cross-linked MoS2 nanosheets and outer carbon layer are organically combined together to form composite microspheres with diameters of 400-500 nm. Due to enhanced electrical conductivity and good structural stability, the MoS2 /C composite microspheres exhibit substantially improved Li/Na-ion storage performance. Compared to unmodified MoS2 , MoS2 /C composite microspheres deliver higher Li/Na-ion storage capacity (Li+ : 1017 mA h g-1 at 100 mA g-1 and Na+ : 531 mA h g-1 at 100 mA g-1 ), as well as better rate capability (Li+ : 434 mA h g-1 at 1 Ag-1 and Na+ : 102 mA h g-1 at 1 Ag-1 ) and capacity retention (Li+ : 902 mA h g-1 after 200 cycles and Na+ : 342 mA h g-1 over 100 cycles). The superior Li/Na-ion storage performance is mainly attributed to the unique porous microsphere architecture with increased electrode/electrolyte interfaces and more diffusion paths for Li/Na ion insertion. Additionally, the carbon coating can not only improve the electronic conductivity, but also suppress the shuttle effect of polysulfides.

A 3D conductive network with high loading Li2S@C for high performance lithium–sulfur batteries

Construction of novel cathodes with a high loading of active material and excellent confinement effect for polysulfides is indispensable and vital for the realization of high-energy and commercially viable lithium–sulfur batteries. In this study, we demonstrated a facile strategy for the fabrication of an integrated lithium sulfide (Li2S) cathode by incorporating lithium sulfide (Li2S)/carbon black (CB) into the carbon felt (CF) with a 3D conductive network and further modifying it by an outer amorphous carbon shell (CF–CB–Li2S@C) via facile liquid solution-evaporation plus chemical vapor deposition technologies. The CF with abundant macroporous channels provides enough reaction sites to load and stabilize a high amount of active materials. The inter-connected conductive network and efficient carbon shell not only provide efficient electron transport and guarantee high active material utilization, but also form a durable protective shield for suppressing polysulfide dissolution. As a result, the CF–CB–Li2S@C cathode with a high loading of 7 mg cm−2 demonstrates an initial discharge capacity of 943.7 mA h g−1 (6.60 mA h cm−2) at 0.1C. Importantly, it still maintains a capacity of 567.5 mA h g−1 (3.97 mA h cm−2) at 1C after 200 cycles, corresponding to a low fading rate of 0.12% per cycle.

Porous carbon hosts for lithium-sulfur batteries

Lithium-sulfur batteries (LSBs) are considered to be one of the most promising alternatives to the current lithium-ion batteries (LIBs) to meet the increasing demand for energy storage owing to their high energy density, natural abundance, low cost, and environmental friendliness. Despite great success, LSBs still suffer from several problems, including undermined capacity arising from low utilization of sulfur, unsatisfactory rate performance and poor cycling life owing to the shuttle effect of polysulfides, and poor electrical conductivity of sulfur. Under such circumstances, the design/fabrication of porous carbon-sulfur composite cathodes is regarded as an effective solution to overcome the above problems. In this review, different synthetic methods of porous carbon hosts and their corresponding integration into carbon-sulfur cathodes are summarized. The pore formation mechanism of porous carbon hosts is also addressed. The pore size effect on electrochemical performance is highlighted and compared. The enhanced mechanism of the porous carbon host on the sulfur cathode is systematically reviewed and revealed. Finally, the combination of porous carbon hosts and high-profile solid-state electrolytes is demonstrated, and the challenges to realize large-scale commercial application of porous carbon-sulfur cathodes is discussed and future trends are proposed.

Hollow metallic 1T MoS2 arrays grown on carbon cloth: a freestanding electrode for sodium ion batteries

Smart design and construction of advanced electrodes are crucial for the development of new electrochemical energy storage systems. In this study, we realized hollow 1T MoS2 arrays grown on carbon cloth via a template-free solvothermal method. Hollow MoS2 arrays, with diameters of 400–500 nm, are composed of curved MoS2 nanosheets. This well-designed structure and the introduction of metallic phase MoS2 can improve electrical conductivity, shorten the electron/sodium ion diffusion, and accommodate the large volume changes during cycling. Due to these features, when employed as an anode of sodium ion batteries, the hollow 1T MoS2 array electrode delivers superior sodium ion storage properties, including enhanced cycling stability (576 mA h g−1 after 200 cycles at 200 mA g−1) and high rate capability (276 mA h g−1 at high current density of 2 A g−1). Our study may guide the synthesis of other nanostructured metal sulfide anodes for electrochemical energy applications.