Yongcheng Jin

Ultrafast lithium storage in TiO2–bronze nanowires/N-doped graphene nanocomposites

A TiO2–bronze/N-doped graphene nanocomposite (TiO2–B/NG) is prepared by a facile hydrothermal combined with hydrazine monohydrate vapor reduction method. The material exhibits macro- and meso-porosity with a high specific surface area of 163.4 m2 g−1. X-Ray photoelectron spectroscopy confirms the successful doping of nitrogen in the graphene sheets. In addition, the TiO2–B nanowires are substantially bonded to the NG sheets. Cyclic voltammetry and electrochemical impedance spectroscopy show that the N-doped graphene improves the electron and Li ion transport in the electrode which results in better electrochemical kinetics than that of the pristine TiO2–B nanowires. As a result, the charge transfer resistance of the TiO2–B/NG electrode is significantly reduced. In addition, the lithium diffusion coefficient of TiO2–B/NG increases by about five times with respect to that of pristine TiO2–B. The TiO2–B/NG composite exhibits a remarkably enhanced electrochemical performance compared to that of TiO2–B. It shows a discharge capacity of 220.7 mA h g−1 at the 10C rate with a capacity retention of 96% after 1000 cycles. In addition, it can deliver a discharge capacity of 101.6 mA h g−1 at an ultra high rate of 100C, indicating its great potential for use in high power lithium ion batteries.

Suppressed Carbon Deposition Behavior in Nickel/Yittria-Stablized Zirconia Anode with SrZr0.95Y0.05O3 − α in Dry Methane Fuel

The distribution of carbon deposition on the cross section of a nickel/yittria-stablized zirconia (Ni/YSZ) anode after an accelerated degradation test in dry methane was analyzed using a scanning electron microscope equipped with an energy dispersive X-ray. The area near the anode top surface side was favored for carbon deposition compared with that near the electrolyte side, suggesting that the electrochemically produced H 2 O and oxygen near the triple phase boundary near the anode top surface side were insufficient for carbon removal reaction. To enhance the reaction of carbon with these two species, a proton-conductor SrZr 0.95 Y 0.05 O 3―α (SZY) was used to modify the Ni/YSZ anode by the infiltration method. The Ni/YSZ anode infiltrated with SZY (Ni/YSZ―SZY) showed a unique structure in which the distribution of SZY was mainly localized near the anode top surface side. In conclusion, the modification of the Ni/YSZ anode by the addition of the proton-conductor SZY improved the operational stability of the anode in dry methane.

Good Low-Temperature Properties of Nitrogen-Enriched Porous Carbon as Sulfur Hosts for High-Performance Li–S Batteries

Despite the increased attention devoted to exploring cathode construction based on various nitrogen-enriched carbon scaffolds at room temperature, the low-temperature behaviors of Li-S cathodes have yet to be studied. Herein, we demonstrate the good low-temperature electrochemical performances of nitrogen-enriched carbon/sulfur composite cathodes. Electrochemical evaluation indicates that a reversible capacity of 368 mAh g(-1) (0.5 C) over 100 cycles is achieved at -20 °C. After returning to 25 °C, a capacity of 620 mAh g(-1) (0.5 C) is achieved over 350 cycles with a low-capacity attenuation rate (0.071% per cycle) and an initial capacity of 1151 mAh g(-1) (0.1C). This positive electrochemical property was speculated to result from the good surface chemistry of the various amine groups in the nitrogen-enriched carbon materials with enhanced polysulfide immobilization.

Effect of Proton Conductor SrCe0.95Yb0.05O3 − α on Electrochemical Characteristics of Nickel/Gadolinium-Doped Ceria Anode in Dry Methane

Ni/Gd 0.2 Ce 0.8 O 2―δ (Ni/GDC) anodes were infiltrated with various amounts of the proton conductor SrCe 0.95 Yb 0.05 O 3―α (SCYb) with the goal of improving the performance of solid oxide fuel cells. First, the electrochemical characteristics of the Ni/GDC and Ni/GDC-SCYb anodes were evaluated in humidified hydrogen (1% H 2 O) fuel and in dry methane fuel at 1173 K, and then the durability of the anodes against carbon deposition was evaluated using an accelerated degradation test. Results revealed that the maximum power density of the Ni/GDC-SCYb anode was 50% higher than that of the Ni/GDC anode, namely 0.648 W/cm 2 in humidified H 2 and 0.438 W/cm 2 in dry methane. In conclusion, the performance of Ni/GDC anodes can be improved in either humidified hydrogen fuel or dry methane fuel by infiltration with SCYb.

Preparation and evaluation of a separator with an asymmetric structure for lithium-ion batteries

The different electrochemical characteristics stemming from the cathode and anode of lithium-ion batteries may have different effects on the surface properties of contacted separators. Herein, a series of composite separators with an asymmetric porous structure are fabricated by a one-step phase inversion method coupled with the settling of SiO2 nanoparticles due to gravity within the poly(vinylidenefluoride-co-hexafluoropylene) (PVDF-HFP) polymer matrix. The unique asymmetric porous separators are composed of a PVDF-HFP-rich layer with high porosity on the front surface, which is in contact with the air, and a SiO2-rich layer on the back surface, which is in contact with the substrate. Besides their excellent thermal stability and high safety towards fire, these asymmetric porous separators result in a high discharge capacity, enhanced cycling performance and excellent rate capability when assembled with a LiNi0.5Mn1.5O4 cathode in coin cells, indicating that the asymmetric porous composite separators could be a promising candidate to improve the performance of lithium-ion batteries.

Stable LATP/LAGP double-layer solid electrolyte prepared via a simple dry-pressing method for solid state lithium ion batteries

In this paper, a NASICON-type Li1.3Al0.3Ti1.7(PO4)3 (LATP)/Li1.3Al0.3Ge1.7(PO4)3 (LAGP) bi-layer structured solid state electrolyte was successfully prepared via a simple dry pressing and post-calcination method. By adjusting the sintering temperature for LAGP starting materials, a dense and smooth LATP/LAGP double-layer solid state electrolyte with no defects was obtained. This electrolyte sample exhibits a high electrical conductivity of 3.4 × 10−4 S cm−1 and a negligible electronic conductivity of 9.6 × 10−9 S cm−1 at room temperature. In addition, the LATP/LAGP electrolyte also shows an excellent stability in air as well as chemical stability against Li. Moreover, an assembled LiFePO4/LATP–LAGP/Li coin-type battery employing LATP/LAGP as the solid state electrolyte can be suitably charged and discharged at a current rate of 0.1C at room temperature, and its low charge–discharge capacities are mainly attributed to the high electrolyte/electrode interfacial resistance of the cell. These results suggest that the LATP/LAGP bi-layer electrolyte can be an alternative electrolyte for all-solid-state lithium-ion batteries.

Micron-sized monocrystalline LiNi1/3Co1/3Mn1/3O2 as high-volumetric-energy-density cathode for lithium-ion batteries

Low-cost layered lithium transition metal oxides delivering high capacity and moderate rate capability are considered as promising cathodes for next-generation lithium-ion batteries (LIBs). However, the low stacking and compressed density results in lower volumetric energy density of such LIBs compared with that of the first commercialized LiCoO2-based battery. Herein, for the first time, a new strategy is rationally proposed to prepare micron-sized monocrystalline LiNi1/3Co1/3Mn1/3O2via stepwise addition of lithium sources into hydroxide/oxide precursors. As anticipated, the as-prepared 4–8 μm-thick monocrystalline cathode exhibits comparable stacking/compressed density with LiCoO2 electrode, achieving ultrahigh volumetric energy density exceeding 2600 W h L−1, enhanced structural stability and high rate capability in half-cells. Moreover, in full-cell configuration, by using this monocrystalline LiNi1/3Co1/3Mn1/3O2 as the cathode and mesocarbon microbeads as the anode, higher volumetric energy density exceeding 660 W h L−1, enhanced cycling stability and high rate capability are achieved, indicating the expectant merits of the micron-sized monocrystalline cathodes. It is also confirmed that this monocrystalline cathode can mitigate side reactions occurring at the electrode/electrolyte interface and maintain the stability of layered structures upon cycling. This facile tactic provides an innovative insight into preparing high-volumetric-energy-density lithium transition metal oxide cathodes with enhanced electrochemical properties. Moreover, this approach can be readily extended to prepare other types of layered and spinel monocrystalline cathodes with improved volumetric energy density.

Low-dimensional inorganic nanofunctional materials: design, assembly, and application for chemical engineering (i)

1 Department of Chemical Engineering, Tsinghua University, Beijing 100084, China 2Department of Bio-Nano-Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China 3 IBM Albany NanoTech Research and Development Center, Albany, NY 12309, USA 4College of Civil Engineering, Guangzhou University, Guangzhou 510006, China 5 Department of Applied Chemistry, Tokyo Metropolitan University, Tokyo 00813, Japan 6Department of Chemical Engineering, Qufu Normal University, Qufu 273165, China