Yanping Mu

Self-assembled novel dandelion-like NiCo2O4 microspheres@nanomeshes with superior electrochemical performance for supercapacitors and lithium-ion batteries

Binary metal oxides have been regarded as potential electrode materials for supercapacitors and lithium-ion batteries, which can ameliorate and compensate the deficiency of electrochemical performance of single metal oxides, such as reversible capacitance/capacity, structural stability and electronic conductivity. In this work, we report a facile solvothermal method to synthesize hierarchical dandelion-like NiCo2O4 microspheres@nanomeshes (NCO-M@N) with a high surface area (105.2 m2 g−1), which exhibit superior pseudocapacitive performance with high specific capacitance (2184 F g−1), remarkable rate capability and excellent cycling performance (94.2% retention after 4000 cycles), meanwhile, displaying excellent energy storage properties for lithium-ion batteries, such as admirable rate performance (785 mA h g−1 at a current density of 2000 mA g−1) and an outstanding capacity retention of 88% after 100 cycles. Most importantly, when the NCO-M@N//AC asymmetric supercapacitor is prepared, it exhibits the highest energy density (45.3 W h kg−1) at a power density of 533.3 W kg−1 and good cycling stability (89% of the initial capacitance retention at 5 A g−1 over 4000 cycles), indicating its potential applications for next-generation high power supercapacitors and lithium-ion batteries. The strategy is simple but very effective, and thus it can be extended to other high-capacity metal oxide materials.

Designed synthesis of cobalt-oxide-based nanomaterials for superior electrochemical energy storage devices

Cobalt oxides, such as Co3O4 and CoO, have received increasing attention as potential anode materials for rechargeable lithium-ion batteries (LIBs) owing to their high theoretical capacity. Nanostructure engineering has been demonstrated as an effective approach to improve the electrochemical performance of electrode materials for LIBs. In this review, we summarize recent developments in the rational design and fabrication of various cobalt oxide-based nanomaterials and their lithium storage performance, including 1D nanowires/belts, 2D nanosheets, 3D hollow/hierarchical structures, hybrid nanostructures with carbon (amorphous carbon, carbon nanotubes and graphene) and mixed metal oxides. By focusing on the effects of their structure on their electrochemical performance, effective strategies for the fabrication of cobalt oxide/carbon hybrid nanostructures are highlighted. This review shows that by rational design, such cobalt-oxide-based nanomaterials are very promising as next generation LIB anodes.

Porous Iron Cobaltate Nanoneedles Array on Nickel Foam as Anode Materials for Lithium-Ion Batteries with Enhanced Electrochemical Performance

A monocrystalline and porous FeCo2O4 nanoneedles array growing directly on a nickel foam substrate was obtained by a hydrothermal technique accompanying with combustion of the one-dimensional precursor. The average length of the FeCo2O4 nanoneedles is approximately 2 μm, while the diameter of the root segment of the nanoneedle can be estimated to be around 100 nm, which gradually reduces to only several nanometers at the top. When the as-prepared porous FeCo2O4 nanoneedles array with a high surface area of 58.49 m(2) g(-1) was applied as binder-free electrode in lithium-ion batteries, it exhibited satisfactory electrochemical performance, such as outstanding reversibility (Coulombic efficiency of approximately 92-95%), high specific capacity (1962 mAh g(-1) at the current density of 100 mA g(-1)), and excellent rate performance (discharge capacity of 875 mAh g(-1) at the current density of 2000 mA g(-1)), due to the various favorable conditions. Undoubtedly, the simple but effective strategy can be expanded to other high-performance binary metal-oxide materials.

Monodisperse Sandwich-Like Coupled Quasi-Graphene Sheets Encapsulating Ni2P Nanoparticles for Enhanced Lithium-Ion Batteries

In this report, sandwiched Ni2 P nanoparticles encapsulated by graphene sheets are first synthesized by directly encapsulating functional units in graphene sheets instead of fabricating separate graphene sheets and then immobilizing the functional components onto the generated surfaces. In this strategy, we use low-cost, sustainable and environmentally friendly glucose as a carbon source and NiNH4 PO4 ⋅H2 O nanosheets as sacrificial templates. This unique structure obtained here cannot only prevent the nanoparticles from aggregation or loss but also enhance the electronic conductivity compared to the independent nanoparticles. Furthermore, the novel sandwich-like Ni2 P/C can be applied in plenty of fields, especially in electrical energy storage. In this paper, a series of electrochemical tests of the sandwich-like Ni2 P/C are carried out, which demonstrate the excellent cyclic stability and rate capacity for lithium-ion batteries.

Unique synthesis of novel octahedral micro/nano-hierarchical LiFePO4 cages as an enhanced cathode material for lithium-ion batteries

Novel monodisperse LiFePO4 cages with an octahedral micro/nano-hierarchical structure have been synthesized for the first time through a simple and controllable solvothermal approach followed by high-temperature calcination. Structural characterization is carried out using X-ray diffraction, scanning electron microscopy, Brunauer–Emmett–Teller surface area measurements, Raman spectroscopy and X-ray energy dispersive spectroscopy. As detected, our unique octahedral micro/nano-LiFePO4 cages possess numerous outstanding properties, such as single-crystalline, hierarchical structure and large specific surface areas, which significantly lead to high rate capability, excellent cycling stability and superior tap density. This special micro/nano-hierarchical structure can be extended to other lithium metal oxide composites, which would promote the development of lithium-ion batteries.

A novel monolithic three-dimensional graphene-based composite with enhanced electrochemical performance

Monolithic 3D porous graphene with a small pore size of ∼250 nm was obtained by a chemical vapor deposition method, using dealloyed nanoporous Ni as a substrate. Monolithic nanocomposites of CoO or PdCo nanoparticles decorated on the 3D porous graphene were facilely synthesized and used as an advanced anode material for lithium ion batteries or as an electrocatalyst in fuel cells, respectively. The synthesized CoO or PdCo alloy nanoparticles with narrow diameter distributions are uniformly anchored on the porous graphene inner surface. The CoO/porous graphene nanocomposite displayed a high performance in lithium ion batteries with a large reversible capacity, excellent cycling stability, and good rate performance. The PdCo/porous graphene exhibited an enhanced catalytic activity for the oxidation of ethanol compared with both Pd/porous graphene and commercial Pd/C, highlighting the importance of monolithic porous graphene in enhancing the electrochemical performance of metal and metal oxide nanoparticles.

Ultra-tiny ZnMn2O4 nanoparticles encapsulated in sandwich-like carbon nanosheets for high-performance supercapacitors

Known as an excellent energy storage material, ZnMn2O4 has a wide range of applications in supercapacitors. In this report, a special sandwich-like structure of ZnMn2O4/C has been first designed and synthesized via a simple hydrothermal method and subsequent calcinations. The designed special sandwich-like structure can benefit ion exchange and remit the probable volume changes during a mass of electrochemical reactions. Furthermore, the porous carbon nanosheets, derived from low-cost glucose, can effectively increase ion flux. Therefore, the novel sandwich-like ZnMn2O4 nanoparticles encapsulated in carbon nanosheets can undoubtedly demonstrate an exceptional electrochemical performance for SCs. In this work, the composite material with porous sandwich-like structure exhibits excellent cyclic stability for 5000 cycles (∼5% loss) and high specific capacitance of 1786 F g-1.

Fabrication of Fe‐Doped LiCoO2 Sandwich‐Like Nanocomposites as Excellent Performance Cathode Materials for Lithium‐Ion Batteries

In this article, the two-layer sandwiched graphene@LiFe0.Co0.8O2 nanoparticles (SG@LFCO) have been prepared and investigated as high-rate and long-life cathode materials for rechargeable lithium-ion batteries. The materials possess a high-surface area (267.1 m(2) g(-1)) and lots of void spaces. By combining various favorable conditions, such as Fe doping, coating graphene, and designing novel morphology, the as-prepared materials deliver a specific capacity of 115 mAh g(-1) at 10 C. At the 0.1 C cycling rate, the capacity retention of 97.2% is sustained after 250 cycles and a coulombic efficiency of around 97.6% is obtained.