Bang-Kun Zou

In situ catalytic formation of graphene decoration on Na3V2(PO4)3 particles for ultrafast and long-life sodium storage

Graphene-decorated Na3V2(PO4)3 (NVP@G) material is synthesized through an in situ catalytic process using the intermediate product component VOx as a catalyst and polyvinyl alcohol as the graphene source. NVP@G shows a superb rate performance and an ultralong cycle life.

Surface Surgery of the Nickel-Rich Cathode Material LiNi0.815Co0.15Al0.035O2: Toward a Complete and Ordered Surface Layered Structure and Better Electrochemical Properties

A complete and ordered layered structure on the surface of LiNi0.815Co0.15Al0.035O2 (NCA) has been achieved via a facile surface-oxidation method with Na2S2O8. The field-emission transmission electron microscopy images clearly show that preoxidation of the hydroxide precursor can eliminate the crystal defects and convert Ni(OH)2 into layered β-NiOOH, which leads to a highly ordered crystalline NCA, with its (006) planes perpendicular to the surface in the sintering process. X-ray photoelectron spectroscopy and Raman shift results demonstrate that the contents of Ni2+ and Co2+ ions are reduced with preoxidization on the surface of the hydroxide precursor. The level of Li+/Ni2+ disordering in the modified NCA determined by the peak intensity ratio I(003)/I(104) in X-ray diffraction patterns decreases. Thanks to the complete and ordered layered structure on the surface of secondary particles, lithium ions can easily intercalate/extract in the discharging-charging process, leading to greatly improved electrochemical properties.

Solvothermal synthesized LiMn1−xFexPO4@C nanopowders with excellent high rate and low temperature performances for lithium-ion batteries

Mixed-carbon coated LiMn1−xFexPO4 (x = 0, 0.2, 0.5, 1) nano-particles are synthesized by a novel solvothermal approach. All of these powders possess a uniform particle size distribution around 150 nm and a carbon coating layer of about 2 nm. The LiMn1−xFexPO4@C samples with a carbon content of 2 wt% have an optimal electrochemical performance. The average voltage platform of LiMn1−xFexPO4@C increases with the increased Mn/Fe ratio, but declines gradually during electrochemical cycling. The LiMn0.5Fe0.5PO4 sample shows a high energy density (568 W h kg−1), good cycleability (97.1%, 100 cycles) and excellent rate capability (120.2 mA h g−1, 20C) at room temperature. Simultaneously, the LiMn0.5Fe0.5PO4 and LiFePO4 samples also show excellent low temperature electrochemical performance with specific capacities of 109.4 and 138.8 mA h g−1 with average discharge voltages of 3.476 V and 3.385 V, respectively, at −12 °C. Even at −20 °C, their discharge specific capacities are 71.7 and 82.3 mA h g−1 at 3C, respectively.

A high energy density full lithium-ion cell based on specially matched coulombic efficiency

Nano-spherical Li-rich cathodes and MnxCo1−xO anodes are synthesized from as-solvothermal MnxCo1−xCO3 (x = 1, 0.8, and 0.5) precursors. Based on the half-cell studies of these materials, Li-rich 0.5Li2MnO3·0.5LiMn0.5Ni0.5O2 with a high reversible capacity of 247 mA h g−1 and binary transition metal oxide Mn0.8Co0.2O with a reversible capacity of 759 mA h g−1 are selected respectively as the optimal positive and negative electrodes to construct a full cell. Such an electrode match-up, i.e. Li-rich/Mn0.8Co0.2O full cell (“N-cell”), allows no need for pre-activation of the metal oxide anode. This “N-cell” can deliver a high reversible capacity of 205 mA h g−1 and particularly rather high volumetric energy density, which is about 31% higher than that of a Li-rich/graphite full cell (“T-cell”). The special coulombic efficiency match-up and tailored microstructures and compositions of the electrode materials are all crucial to achieve such a high energy density.

Synthesis of different CuO nanostructures by a new catalytic template method as anode materials for lithium-ion batteries

CuO powders composed of different rod-like clusters or dandelion-like nanospheres are prepared by a low-temperature thermal decomposition process of Cu(OH)2 precursors, which are obtained via a catalytic template method. A tentative mechanism is proposed to explain the formation and transformation of different Cu(OH)2 nanostructures. X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, field-emission scanning electron microscopy, transmission electron microscopy, infrared spectra analysis, Brunauer–Emmett–Teller measurements, and galvanostatic cell cycling are employed to characterize the structures and electrochemical performance of these CuO samples. The results show that these CuO samples obtained after 500 °C calcination have a stable cycling performance with a reversible capacity of over 587 mA h g−1 after 50 cycles. The dandelion-like CuO electrode shows the best rate performance with a high capacity of 511 mA h g−1 at 4C.

A novel lithium-ion battery comprising Li-rich@Cr 2 O 5 composite cathode and Li 4 Ti 5 O 12 anode with controllable coulombic efficiency

Through meticulous design, a Li-lacking Cr2O5 cathode is physically mixed with Li-rich Li1.2Ni0.13Co0.13Mn0.54O2 (LNCM) cathode to form composite cathodes LNCM@xCr2O5 (x = 0, 0.1, 0.2, 0.3, 0.35, 0.4, mass ratio) in order to make use of the excess lithium produced by the Li-rich component in the first charge-discharge process. The initial coulombic efficiency (ICE) of LNCM half-cell has been significantly increased from 75.5% (x = 0) to 108.9% (x = 0.35). A novel full-cell comprising LNCM@Cr2O5 composite cathode and Li4Ti5O12 anode has been developed. Such electrode accordance, i.e., LNCM@Cr2O5//Li4Ti5O12 (“L-cell”), shows a particularly high ICE of 97.7%. The “L-cell” can transmit an outstanding reversible capacity up to 250 mA h g−1 and has 94% capacity retention during 50 cycles. It also has superior rate capacities as high as 122 and 94 mA h g−1 at 1.25 and 2.5 A g−1 current densities, which are even better in comparison of Li-rich//graphite full-cell (“G-cell”). The high performance of “L-cell” benefiting from the well-designed coulombic efficiency accordance mechanism displays a great potential for fast charge-discharge applications in future high-energy lithium ion batteries.摘要本文将缺锂态的Cr2O5正极材料与Li1.2Ni0.13Co0.13Mn0.54O2(LNCM)富锂相正极材料进行物理混合, 形成了复合正极材料LNCM@xCr2O5(x = 0,0.1,0.2,0.3,0.35, 0.4), 从而在第一次充放电过程中达到有效利用富锂相所产生的不可逆的锂离子. 复合之后, LNCM半电池的首次库仑效率(ICE)得到显著提高, 从75.5(x = 0)提高到了108.9(x = 0.35). LNCM@Cr2O5复合正极材料和Li4Ti5O12负极材料匹配而成的新型锂离子全电池, 即LNCM@Cr2O5//Li4Ti5O12(L电池)表现出高达97.7的ICE. 不仅如此, L电池还表现出了高达250 mA h g—1的可逆容量, 并且 在循环50次之后仍具有94%的容量保持率. 此外, 在1.25和2.5 A g—1电流密度下, 它还具有高达122和94 mA h g—1的放电比容量, 远远优于LNCM//石墨全电池(G电池). L电池的高性能得益于精心设计的库仑效率匹配机制, 并且在未来高能量锂离子电池的快速充放电应用中表现出巨大的潜力.