Huanqiao Song

A Self‐Charging Power Unit by Integration of a Textile Triboelectric Nanogenerator and a Flexible Lithium‐Ion Battery for Wearable Electronics

A novel integrated power unit realizes both energy harvesting and energy storage by a textile triboelectric nanogenerator (TENG)-cloth and a flexible lithium-ion battery (LIB) belt, respectively. The mechanical energy of daily human motion is converted into electricity by the TENG-cloth, sustaining the energy of the LIB belt to power wearable smart electronics.

Mo-doped LiV3O8 nanorod-assembled nanosheets as a high performance cathode material for lithium ion batteries

Mo-doped LiV3O8 nanorod-assembled nanosheets were prepared by a simple hydrothermal reaction of LiOH·H2O, V2O5 and (NH4)6Mo7O24 as precursors followed by thermal annealing. X-ray diffraction results show that the intensity of the (100) peak is less than that of (11) in the Mo-doped LiV3O8 nanosheets, suggesting the inferior crystallinity of Mo-doped LiV3O8. Shifts of Raman bands to lower wavenumbers are found in the Mo-doped LiV3O8 material, which when compared with those of pure LiV3O8 indicates that Mo6+ substitutes V5+ in the LiV3O8 layer. X-ray photoelectron spectroscopy reveals that the Mo-doped LiV3O8 nanosheets calcined at 400 °C contain 25% V4+ and 3.5% oxygen vacancies, which likely compensates for the accommodation of 5% Mo6+. The Brunauer–Emmett–Teller surface area of the Mo-doped LiV3O8 nanosheets calcined at 400 °C is 24.8 m2 g−1, which is nearly double of LiV3O8 calcined at 400 °C (13.9 m2 g−1). The electrochemical and lithium ion intercalation properties of both pure and Mo-doped LiV3O8 cathode were systematically studied using cyclic voltammetry, chronopotentiometry, and electrochemical impedance spectroscopy. The Mo-doped LiV3O8 cathode shows a much higher lithium ion storage capacity, better cyclic stability, and higher rate capability than the pure LiV3O8 cathode. The maximum discharge capacity of the Mo-doped LiV3O8 (calcined at 400 °C) cathode is 269.0 mA h g−1 and retains 205.9 mA h g−1 at a current density of 300 mA g−1, which is much higher than 97.8 mA h g−1 of the LiV3O8 (also calcined at 400 °C) cathode during the 100th cycle. Note that Mo doping is found to increase the electrochemical reaction reversibility, reduce the electrochemical reaction resistance, and enhance the lithium ion diffusivity. The possible reasons for such significant enhancement in the discharge/charge capacity, cyclic stability and rate performance of the Mo-doped LiV3O8 cathode are elucidated based on the structure analysis.

Hollow-Cuboid Li3VO4/C as High-Performance Anodes for Lithium-Ion Batteries.

Li3VO4 has been demonstrated to be a promising anode material for lithium-ion batteries with a low, safe voltage and large capacity. However, its poor electronic conductivity hinders its practical application particularly at a high rate. This work reports that Li3VO4 coated with carbon was synthesized by a one-pot, two-step method with F127 ((PEO)100-(PPO)65-(PEO)100) as both template and carbon source, yielding a microcuboid structure. The resulting Li3VO4/C cuboid shows a stable capacity of 415 mAh g(-1) at 0.5 C and excellent capacity stability at high rates (e.g., 92% capacity retention after 1000 cycles at 10 C = 4 A g(-1)). The lithiation/delithiation process of Li3VO4/C was studied by ex situ X-ray diffraction and Raman spectroscopy, which confirmed that Li3VO4/C underwent a reversible intercalation reaction during discharge/charge processes. The excellent electrochemical performance is attributed largely to the unique microhollow structure. The voids inside hollow structure can not only provide more space to accommodate volume change during discharge/charge processes but also allow the lithium ions insertion and extraction from both outside and inside the hollow structure with a much larger surface area or more reaction sites and shorten the lithium ions diffusion distance, which leads to smaller overpotential and faster reaction kinetics. Carbon derived from F127 through pyrolysis coats Li3VO4 conformably and thus offers good electrical conduction. The results in this work provide convincing evidence that the significant potential of hollow-cuboid Li3VO4/C for high-power batteries.

Coherent Mn3O4-carbon nanocomposites with enhanced energy-storage capacitance

Nanostructured Mn3O4 was introduced to activated C (AC) by a novel sonochemical reaction, and the resulting nanocomposites were examined as supercapacitor electrodes. The sonication not only catalyzed the redox reaction but also promoted the diffusion of the precursors, causing the formation of coherent nanocomposites with Mn3O4 nanoparticles grown and uniformly distributed inside the mesopores of the AC. In addition, the extreme local condition in the sonochemical synthesis yielded an excessive amount of divalent manganese ions and oxygen vacancies. This novel microstructure endowed the sample with a superior performance, including a specific capacitance of 150 F/g compared with the value of 93 F/g for AC at a charge/discharge rate of 100 mA/g. A Li-ion capacitor delivered an energy density of 68 Wh/kg, compared with 41 Wh/kg for the AC capacitor at a power density of 210 W/kg.

MnO nanoparticles with cationic vacancies and discrepant crystallinity dispersed into porous carbon for Li-ion capacitors

MnO nanoparticles with cationic vacancies and discrepant crystallinity were prepared through a one-step hydrothermal synthesis followed by calcination at different temperatures. Glucose was used as both a reducing agent to introduce cationic vacancies with a content of ∼5.5% into MnO nanocrystals, and a carbon source to encapsulate MnO nanocrystals in a three dimensional porous framework. Cationic vacancies benefit phase transition in a conversion reaction, and together with a low degree of crystallinity, may also provide more void spaces for ion diffusion (3.37 × 10−13 cm2 s−1). Three dimensional porous carbon with a pore volume of 0.27 cm3 g−1 demonstrated a high electrical conductivity of 6.25 S cm−1 and offered fast pathways for charge transfer and penetration of the electrolyte. Such a synergistic structure endowed MnO with excellent electrochemical properties including a considerably enhanced capacity of 650 mA h g−1 at a current density of 1000 mA g−1. Li ion capacitors based on such a MnO anode and activated carbon cathode achieved the maximum energy density of 220 W h kg−1, and the capacitance retention was 95.3% after 3600 cycles at a rate of 5000 mA g−1.