High Rate and Stable Li-Ion Insertion in Oxygen-Deficient LiV3O8 Nanosheets as a Cathode Material for Lithium-Ion Battery.

Low performance of cathode materials has become one of the major obstacles to the application of lithium-ion battery (LIB) in advanced portable electronic devices, hybrid electric vehicles, and electric vehicles. The present work reports a versatile oxygen-deficient LiV3O8 (D-LVO) nanosheet that was synthesized successfully via a facile oxygen-deficient hydrothermal reaction followed by thermal annealing in Ar. When used as a cathode material for LIB, the prepared D-LVO nanosheets display remarkable capacity properties at various current densities (a capacity of 335, 317, 278, 246, 209, 167, and 133 mA h g-1 at 50, 100, 200, 500, 1000, 2000, and 4000 mA g-1, respectively) and excellent lithium-ion storage stability, maintaining more than 88% of the initial reversible capacity after 200 cycles at 1000 mA g-1. The outstanding electrochemical properties are believed to arise largely from the introduction of tetravalent V (∼15% V4+) and the attendant oxygen vacancies into LiV3O8 nanosheets, leading to intrinsic electrical conductivity more than 1 order of magnitude higher and lithium-ion diffusion coefficient nearly 2 orders of magnitude higher than those of LiV3O8 without detectable V4+ (N-LVO) and thus contributing to the easy lithium-ion diffusion, rapid phase transition, and the excellent electrochemical reversibility. Furthermore, the more uniform nanostructure, as well as the larger specific surface area of D-LVO than N-LVO nanosheets may also improve the electrolyte penetration and provide more reaction sites for fast lithium-ion diffusion during the discharge/charge processes.

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.

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.

New anhydrous proton exchange membrane for intermediate temperature proton exchange membrane fuel cells.

Herein, we study the preparation and characterization of a new kind of proton exchange membrane. In the proton-conducting membrane of poly(vinylidene fluoride) (PVDF)/poly(ethylene oxide) (PEO)/dodecyl benzenesulfonic acid (DBS-H), we use PEO as "proton solvent" due to its flexible molecular chain. Moreover, the electronegativity of the O atom on PEO may be used to attract protons under anhydrous conditions. The membranes are thermally stable up to 200 °C with less than 3 % mass loss. At 150 °C, without extra humidification, the proton conductivity of 60 % PVDF/22 % PEO/18 % DBS-H membrane is approximately 10 (-3) S cm(-1).