Yun Qiao

MOF-Derived Cobalt-Doped ZnO@C Composites as a High-Performance Anode Material for Lithium-Ion Batteries

Cobalt (Co)-doped MOF-5s (Co-MOF-5s) were first synthesized by a secondary growth method, followed by a heat treatment to yield Co-doped ZnO coated with carbon (CZO@C). Compared with carbon-coated ZnO (ZnO@C), the doping of Co increased the graphitization degree of the carbon on the surface of CZO@C nanoparticles and enhanced the conductivity of the material. The electrochemical properties of the materials were characterized by galvanostatic discharge/charge tests. It was found that the as-synthesized CZO@C composites enabled a reversible capacity of 725 mA h g(-1) up to the 50th cycle at a current density of 100 mA g(-1), which was higher than that of ZnO@C composites (335 mA h g(-1)).

Coral-like α-MnS composites with N-doped carbon as anode materials for high-performance lithium-ion batteries

Coral-like α-MnS composites with nitrogen-doped carbon (NC) were designed as anode materials for lithium-ion batteries. A facile two-step method was developed to synthesize the composites. Hydrothermally obtained polyvinyl pyrrolidone (PVP) capped (NH4)2Mn2(SO4)3 was used as a precursor. The α-MnS–NC composites were attained by heating the precursor at different temperatures for an appropriate time in a N2 atmosphere. The microstructure and morphology were carefully investigated by means of field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and powder X-ray diffraction (XRD). As anode materials, the α-MnS–NC composites exhibit large reversible capacity, excellent cyclic stability and high rate capability. At a current density of 500 mA g−1, the discharge capacity reaches as high as 878 mA h g−1 at the first cycle and remains at 699 mA h g−1 even after 400 cycles.

Conformal N-doped carbon on nanoporous TiO2 spheres as a high-performance anode material for lithium-ion batteries

Conformal N-doped carbon (NC) on nanoporous TiO2 spheres has been successfully synthesized via a facile solution-phase process and subsequent heat treatment. The highly conductive and uniform NC layer coated on the surface of nanoporous TiO2 spheres facilitates lithium ion diffusion and electronic transport. The resulting TiO2@NC nanohybrid not only delivers a high capacity of ∼170 mA h g−1 at a current density of 0.1 A g−1, but also exhibits excellent rate capability (∼102 mA h g−1 at a current density of 2.0 A g−1). The as-formed porous TiO2@NC electrode is promising for secondary battery applications with high power and energy densities.

Electrospun sillenite Bi12MO20 (M = Ti, Ge, Si) nanofibers: general synthesis, band structure, and photocatalytic activity.

Sillenite Bi12MO20 (M = Ti, Ge, Si) nanofibers have been fabricated through a facile electrospinning route for photocatalytic applications. Uniform Bi12MO20 (M = Ti, Ge, Si) nanofibers with diameters of 100-200 nm and lengths of up to several millimeters can be readily obtained by thermally treating the electrospun precursors. The photocatalytic activities of these nanofibers for degradation of rhodamine B (RhB) were explored under UV-visible light. The band structure and the degradation mechanisms were also discussed. The fibrous photocatalysts of Bi12TiO20, Bi12SiO20 and Bi12GeO20 exhibit different photocatalytic behaviours, which are attributed to the microstructure, band gap, and electronic structures.

First-principles and experimental study of nitrogen/sulfur co-doped carbon nanosheets as anodes for rechargeable sodium ion batteries

Heteroatom doped carbon materials have recently demonstrated an outstanding sodium storage ability and are being considered as the most promising candidate as anodes for sodium ion batteries. However, there is limited understanding of the relationship between structural and electronic properties and electrochemical storage capacity. First-principles calculations on a doped graphene cluster propose that N, S co-doping can promote the electronegativity, adsorption capacity of Na atoms and diffusion of Na+ ions on graphene sheets, especially for the sample consisting of more pyridinic-N, while excessive O atoms may alleviate these. All these features render N, S co-doped carbon as a superior anode for sodium ion batteries. Therefore, the N, S co-doped carbon nanosheets are fabricated via a simple thermal treatment method using gelatin as the carbon source and thiourea as the N and S precursor. The optimized product (mgelatin : mthiourea = 1 : 10) results in a superb cycling capacity of 300 mA h g−1 after 500 cycles, with a coulombic efficiency of ∼100%. This study provides a facile and reliable route to prepare co-doped carbon with enhanced sodium storage properties.

Hollow K0.27MnO2 Nanospheres as Cathode for High-Performance Aqueous Sodium Ion Batteries.

Hollow K0.27MnO2 nanospheres as cathode material were designed for aqueous sodium ion batteries (SIBs) using polystyrene (PS) as a template. The samples were systematically studied by X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. As cathode materials for aqueous SIBs, the hollow structure can effectively improve the sodium storage property. A coin cell with hollow K0.27MnO2 as cathode and NaTi2(PO4)3 as anode exhibits a specific capacity of 84.9 mA h g(-1) at 150 mA g(-1), and the capacity of 56.6 mA h g(-1) is still maintained at an extremely high current density of 600 mA g(-1). For full cell measurement at the current density of 200 mA g(-1), 83% capacity retention also can be attained after 100 cycles. The as-designed hollow K0.27MnO2 nanospheres demonstrate long cyclability and high rate capability, which grant the potential for application in advanced aqueous SIBs.

Nanostructured alkali cation incorporated δ-MnO2 cathode materials for aqueous sodium-ion batteries

Nanostructured δ-MnO2 incorporated with alkali cations (A-δ-MnO2, A = K+, Na+) has been synthesized and evaluated as a cathode material for aqueous sodium-ion batteries. It is observed that Na+ ions are easier than K+ ions to intercalate into the layered δ-MnO2 due to their smaller ion radius. The incorporation of K+ and Na+ into δ-MnO2 shows a great influence on the electrochemical performance of the layered δ-MnO2. The full cell with (K, Na)-co-incorporated δ-MnO2 (K : Na : Mn = 0.15 : 0.26 : 1) hierarchical nanospheres as the cathode and NaTi2(PO4)3 as the anode exhibits a specific capacity of 74.6 mA h g−1 at 150 mA g−1, and the capacity remains at ∼62% at a high current density of 600 mA g−1. The electrochemical cycling does not induce observable structural degradation even after 200 cycles. K-incorporated and (K, Na)-co-incorporated δ-MnO2 electrodes have superior capacity and rate capability, which can be ascribed to their hierarchical structure and adequate crystallinity.

In situ synthesis of flexible elastic N-doped carbon foam as a carbon current collector and interlayer for high-performance lithium sulfur batteries

A flexible elastic N-doped carbon foam (NCF) has been successfully synthesized in situ via direct carbonization/pyrolysis of polyurethane foam, which is a facile, cost-effective and environmentally friendly method. Due to its uniform three-dimensional connected structure, its reasonable composition with N doping and its high electronic conductivity, the NCF can function as both a three-dimensional current collector and a carbon interlayer for lithium sulfur batteries. As a typical model, cathodes consisting of NCF and CNT/S were prepared. The resulting batteries deliver a large reversible capacity of 1124 mA h g−1 at 0.5C and retain a high specific capacity of 902.8 mA h g−1 after 100 cycles, with a coulombic efficiency of 98.6% throughout the cycles. Furthermore, a discharge capacity of 691.8 mA h g−1 is still attainable when the rate is increased to 2.0C. The excellent cycling performance and rate capability are contributed to the uniform flexible elastic, conductive 3D framework and good porosity, and may have great significance for large-scale commercial applications of Li–S batteries.

Bio-inspired synthesis of ordered N/P dual-doped porous carbon and its use as anode for sodium-ion batteries.

Carbonaceous materials are one of the most promising anode materials for sodium-ion batteries, because of their abundance, stability, and safe usage. However, the practical application of carbon materials is hindered by poor specific capacity and low initial Coulombic efficiency. The design of porous structure and doping with heteroatoms are two simple and effective methods to promote the sodium storage performance. Herein, the N, P co-doped porous carbon materials are fabricated using renewable and biodegradable gelatin as carbon and nitrogen resource, phosphoric acid as phosphorus precursor and polystyrene nanospheres as a template. The product can deliver a reversible capacity of 230 mA h g-1 at a current density of 0.2 A g-1 , and even a high capacity of 113 mA h g-1 at 10 Ag-1 . The enhanced sodium storage performance is attributed to the synergistic effect of the porosity and the dual-doping of nitrogen and phosphorus.

Architecture design of nitrogen-doped 3D bubble-like porous graphene for high performance sodium ion batteries

N-Doped 3D bubble-like porous graphene was synthesized via a simple template directed method using polystyrene nanospheres as a template and low-cost industrial melamine as the nitrogen source. The as-synthesized N-3DPGX possessed a high specific surface area, uniform and controllable porous structure and high nitrogen doping content. Benefiting from these features, the as-obtained N-3DPG4 as an anode for sodium ion batteries delivered a high specific capacity of 310 mA h g−1 after 500 cycles at a current density of 0.2 A g−1, and also excellent rate capability as high as 169 mA h g−1 at 10 A g−1. This simple synthetic method, unique porous structure and outstanding electrochemical performance demonstrated that N-3DPG is a promising candidate for application in sodium ion batteries for large-scale electrochemical energy storage.