Peixun Xiong

Metal–organic frameworks: a new promising class of materials for a high performance supercapacitor electrode

A layered structure Ni-based MOF was synthesized and, for the first time, was used as the electrode material for a supercapacitor. It exhibited large specific capacitance, high rate capability and cycling stability. Capacitances of 1127 and 668 F g−1 can be achieved at rates of 0.5 and 10 A g−1, respectively. At the same time, over 90% performance was retained after 3000 cycles. These excellent electrochemical properties may be related to the intrinsic characteristics of Ni-based MOF materials.

Zn-doped Ni-MOF material with a high supercapacitive performance

A layered structural Zn-doped Ni-MOF was synthesized and, for the first time, used as an electrode material for a supercapacitor. It exhibited large specific capacitance, high rate capability and good cycling stability. Capacitances of 1620 and 854 F g−1 can be achieved at rates of 0.25 and 10 A g−1, respectively. Simultaneously, the retention was maintained at over 91% even after 3000 cycles. These values demonstrated the best performance of all the MOF materials in supercapacitor at present. Such an excellent electrochemical property may be attributed to the intrinsic characteristics of Zn-doped Ni-MOF material including its crystal structure and morphology.

Pseudo-capacitive performance of titanate nanotubes as a supercapacitor electrode

Layered titanate H2Ti3O7 nanotubes were synthesized and firstly used as a supercapacitor electrode in a non-aqueous electrolyte. They exhibited the specific capacitances as high as 414 and 306 F g(-1) at 0.5 and 10 A g(-1), respectively, and 82% of the specific capacitance at the 10th cycle can be retained after 1000 cycles.

Facile synthesis of hierarchical MnO2 sub-microspheres composed of nanosheets and their application for supercapacitors

Hierarchical MnO2 sub-microspheres were fabricated by using a simple, green and efficient low-temperature route. These sub-microspheres were formed via the aggregation of ultrathin nanosheets with a thickness of 2–4 nm. An electrode made of hierarchical MnO2 sub-microspheres exhibited a specific capacitance of 120 F g−1 at a current density of 0.167 A g−1. For an asymmetric AC//MnO2 supercapacitor, it exhibited a superior electrochemical stability in 1 M Na2SO4 aqueous solution with 88% retention of the initial specific capacitance after 1000 cycles, and the Coulombic efficiency was above 97%, indicating good charge–discharge reversibility and electrochemical stability.

Ultrathin TiO2-B nanowires with enhanced electrochemical performance for Li-ion batteries

A facile one-step hydrothermal route was designed for preparing ultrathin TiO2-B nanowires, which were then hybridized with RGO to form a TiO2-B/RGO hybrid via an in situ approach, and both of them have a large BET surface area (231.6 m2 g−1 for TiO2-B nanowires and 256.1 m2 g−1 for the TiO2-B/RGO hybrid). It was found that the synthesized ultrathin nanowires are perpendicular to the [010] direction which is the most open channel in the TiO2-B crystal structure, demonstrating more Li-ion insertion/extraction hosts exposed to the electrolyte. Thus, the cell made of TiO2-B ultrathin nanowires exhibited large reversible lithium-ion charge–discharge capacity, excellent cycling stability and high-rate capability. When combined with RGO, the formed TiO2-B/RGO hybrid exhibited further improved Li storage performance. For instance, a capacity of 205.3 mA h g−1 was obtained at the fourth cycle and then faded slightly to 189.4 mA h g−1 after 300 cycles, demonstrating a surprising low average capacity fading of ca. 0.026% per cycle from 4th to 300th cycles.

Nanocomposite Li3V2(PO4)3/carbon as a cathode material with high rate performance and long-term cycling stability in lithium-ion batteries

In the present work, nanocomposite Li3V2(PO4)3/carbon is successfully synthesized by combining a sol–gel method and a nanocasting route, and then it is characterized by means of X-ray diffraction (XRD), thermogravimetric analysis (TG), N2 adsorption–desorption, and transmission electron microscopy (TEM). Furthermore, this nanocomposite is used as a cathode material for Li-ion intercalation and exhibits large reversible capacity, high rate performance and excellent long-term cycling stability. For instance, a large reversible capacity of 95 mA h g−1 and an average Coulombic efficiency of 99.1% can be maintained even after 3000 cycles at a high rate of 20C in the potential range of 3.0–4.3 V. Moreover, the Li3V2(PO4)3/C nanocomposite delivered a large capacity of 127 mA h g−1 at a high rate of 10C in the voltage range of 3.0–4.8 V. The super results might be attributed to the unique hierarchical architecture of the Li3V2(PO4)3/carbon nanocomposite.

Nitrogen-doped carbon coated silicon derived from a facile strategy with enhanced performance for lithium storage

Silicon-based nanostructures are receiving intense interest in lithium-ion batteries (LIBs) because they have ultrahigh lithium ion storage ability. However, the fast capacity fading induced by the considerably tremendous volume changes of Si anode during the Li-ion intercalation processes as well as the low intrinsic electric conductivity have hindered its deployment. Herein, we initially developed an effective technique to synthesize the core-shell Si/nitrogen-doped carbon (Si/N−C), composite by combining in situ interfacial polymerization and decorate with melamine, followed by carbonization. When used as anode material for LIBs, the Si/N−C composite delivered a notable reversible capacity (1084 mAh g−1 at 0.2 A g−1 for 50 cycles) and high rate capability (495 mAh g−1 at 1 A g−1).