Li-Ping Lv

Microwave-Assisted Morphology Evolution of Fe-Based Metal–Organic Frameworks and Their Derived Fe2O3 Nanostructures for Li-Ion Storage

The metal-organic-framework (MOF) approach is demonstrated as an effective strategy for the morphology evolution control of MIL-53(Fe) with assistance of microwave irradiation. Owing to the homogeneous nucleation offered by microwave irradiation and confined porosity and skeleton by MOF templates, various porous Fe2O3 nanostructures including spindle, concave octahedron, solid octahedron, yolk-shell octahedron, and nanorod with porosity control are derived by simply adjusting the irradiation time. The formation mechanism for the MOF precursors and their derived iron oxides with morphology control is investigated. The main product of the mesoporous yolk-shell octahedron-in-octahedron Fe2O3 nanostructure is also found to be a promising anode material for lithium-ion batteries due to its excellent Li-storage performance. It can deliver a reversible larger-than-theoretical capacity of 1176 mAh g-1 after 200 cycles at 100 mA g-1 and good high-rate performance (744 mAh g-1 after 500 cycles at 1 A g-1).

MOF-templated nanorice–nanosheet core–satellite iron dichalcogenides by heterogeneous sulfuration for high-performance lithium ion batteries

Metal dichalcogenides are promising electrode materials for lithium-ion batteries (LIBs) because of their large specific capacities. Their electrochemical properties are largely dependent on their composition, morphology and porosity. This paper reports a metal–organic framework (MOF) synthetic approach for achieving a nanorice–nanosheet core–satellite structure of sulfur-doped porous carbon coated FeS2 (FeS2@S-C NR-NS (MOF)). Unlike substantial morphology transformation in the sulfuration process from common Fe-based precursors, the nanorice skeleton can be inherited from the Fe-MOF precursor, while small nanosheets are formed on the exterior surface due to heterogeneous sulfuration. When evaluated as the anode material for LIBs, FeS2@S-C NR-NS (MOF) exhibits excellent cycling performances with a larger-than-theoretical reversible capacity of 1336.5 mA h g−1 after 200 cycles at 100 mA g−1 and good high-rate capability. The improved structural stability, electrical conductivity and enhanced kinetic rate of ions and electrons have been attributed to the hierarchical structure, porous characteristics, and S-doped carbon overlayer in the electrode.

Bimetal-Organic-Framework Derivation of Ball-Cactus-Like Ni-Sn-P@C-CNT as Long-Cycle Anode for Lithium Ion Battery

Metal phosphides are a new class of potential high-capacity anodes for lithium ion batteries, but their short cycle life is the critical problem to hinder its practical application. A unique ball-cactus-like microsphere of carbon coated NiP2 /Ni3 Sn4 with deep-rooted carbon nanotubes (Ni-Sn-P@C-CNT) is demonstrated in this work to solve this problem. Bimetal-organic-frameworks (BMOFs, Ni-Sn-BTC, BTC refers to 1,3,5-benzenetricarboxylic acid) are formed by a two-step uniform microwave-assisted irradiation approach and used as the precursor to grow Ni-Sn@C-CNT, Ni-Sn-P@C-CNT, yolk-shell Ni-Sn@C, and Ni-Sn-P@C. The uniform carbon overlayer is formed by the decomposition of organic ligands from MOFs and small CNTs are deeply rooted in Ni-Sn-P@C microsphere due to the in situ catalysis effect of Ni-Sn. Among these potential anode materials, the Ni-Sn-P@C-CNT is found to be a promising anode with best electrochemical properties. It exhibits a large reversible capacity of 704 mA h g-1 after 200 cycles at 100 mA g-1 and excellent high-rate cycling performance (a stable capacity of 504 mA h g-1 retained after 800 cycles at 1 A g-1 ). These good electrochemical properties are mainly ascribed to the unique 3D mesoporous structure design along with dual active components showing synergistic electrochemical activity within different voltage windows.

Functionalized Graphene Quantum Dot Modification of Yolk–Shell NiO Microspheres for Superior Lithium Storage

Yolk-shell NiO microspheres are modified by two types of functionalized graphene quantum dots (denoted as NiO/GQDs) via a facile solvothermal treatment. The modification of GQDs on the surface of NiO greatly boosts the stability of the NiO/GQD electrode during long-term cycling. Specifically, the NiO with carboxyl-functionalized GQDs (NiO/GQDsCOOH) exhibits better performances than NiO with amino-functionalized GQDs (NiO/GQDsNH2 ). It delivers a capacity of ≈1081 mAh g-1 (NiO contribution: ≈1182 mAh g-1 ) after 250 cycles at 0.1 A g-1 . In comparison, NiO/GQDsNH2 electrode holds ≈834 mAh g-1 of capacity, while the bald NiO exhibits an obvious decline in capacity with ≈396 mAh g-1 retained after cycling. Except for the yolk-shell and mesoporous merits, the superior performances of the NiO/GQD electrode are mainly ascribed to the assistance of GQDs. The GQD modification can support as a buffer alleviating the volume change, improve the electronic conductivity, and act as a reservoir for electrolytes to facilitate the transportation of Li+ . Moreover, the enrichment of carboxyl/amino groups on GQDs can further donate more active sites for the diffusion of Li+ and facilitate the electrochemical redox kinetics of the electrode, thus together leading to the superior lithium storage performance.

Ultrasmall MoC nanoparticles embedded in 3D frameworks of nitrogen-doped porous carbon as anode materials for efficient lithium storage with pseudocapacitance

Transition metal carbides are promising anode candidates for lithium ion batteries, however, their potential accomplishment still requires a rational structural design to improve their low reversible capacities, especially at high current densities and during long-term cycling. This work designs ultrasmall MoC nanoparticles with a diameter of 2–3 nm that are anchored in a three-dimensional (3D) network of nitrogen-doped porous carbon (denoted as MoC–N–C). The MoC–N–C can not only shorten the ion diffusion pathway, leading to fast transport of Li+, but also accommodate the volume expansion and adhesion of MoC nanoparticles during long-term cycling. Consequently, it displays large charge reversible capacities of 1246 mA h g−1 (300 cycles, 100 mA g−1), 813 mA h g−1 (500 cycles, 1 A g−1) and 675 mA h g−1 (500 cycles, 2 A g−1), for lithium ion batteries. In addition to mesoporous properties, large surface area, high ion/electron conductivity, and N-doped characteristics, the excellent lithium storage capability of the MoC–N–C composites, especially at high current densities and during long-term cycling can be mainly ascribed to the significant pseudocapacitance contribution (∼84% at 0.5 mV s−1) and synergistic effects between the N-doped 3D conductive network and the in situ generated ultrafine MoC nanoparticles.