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At present, the second-class oil layer has become the main polymer flooding replacement layer in the Lamadian Oilfield. The second-class oil layer has low permeability, low connectivity and serious heterogeneity. The results of the polymer flooding laboratory experiments are quite different from the field flooding effect. Polysystem design provides better guidance. Based on theoretical and field data analysis, this paper adopts constant pressure injection method. After the experimental injection fluid is seepage through a 1.5m long core, the core flooding experiment is carried out, that is, the problem of excessive pressure rise in polymer flooding is controlled, so that the injection fluid is closer to the oil layer. state of the injected system. The constant pressure polymer flooding experiment was used to establish the matching relationship between the polymer system and oil layers with different permeability, which effectively guided the design of the on-site polymer injection system. At present, indoor polymer flooding core experiments generally adopt the constant speed mode, without controlling the injection pressure. However, due to the influence of permeability, connectivity and other factors, the injection pressure increases greatly, and the reservoir water absorption is difficult, which leads to a great difference between the experimental results and the field effect. In order to make the indoor core experiment closer to the actual field injection state and better guide the design of polymer flooding scheme, it is urgent to optimize and improve the experimental method.

The use of inexpensive graphite oxide (GO) as a carbon source, instead of the expensive reduced graphene oxide (rGO), is essential to prepare metal oxide/rGO composites. In this work, we investigated the in situ reaction of GO and FeCl3 to produce Fe2O3/rGO composites as anode materials for high‐energy lithium‐ion batteries (LIBs). In this reaction, iron ions combined with the oxygen‐containing functional groups of GO, which subsequently grew into Fe2O3 nanoparticles, whereas the GO transformed into rGO under hydrothermal conditions. In the composite Fe2O3−rGOx samples, intergranular gaps in the Fe2O3 sub‐micron particles evidently increased the contact between the Fe2O3 active material and the electrolyte, which improved the Li‐ion conductivity and electrochemical performance of the Fe2O3−rGOx composites. The Fe2O3−rGO2 sample showed the best cyclic performance and delivered the highest capacity of all samples. The initial discharge and charge capacities of Fe2O3−rGO2 were 1086.3 and 722.4 mAh g−1, respectively. After 100 cycles, the discharge specific capacity of Fe2O3−rGO2 was 653.2 mAh g−1 and the coulombic efficiency was 98.4 %. We found that an appropriate weight ratio and composite morphology of Fe2O3−rGOx were important in influencing the electrochemical properties of the composite anode materials for high‐energy LIBs. [ABSTRACT FROM AUTHOR]

3D nanohybrid structures with few-layered MoS2 nanosheets uniformly incorporated in the carbon substrate are prepared via using the rapid and homogeneous microwave-hydrothermal method, in which the size of the basic unit structure of MoS2/C was small. The samples were systematically investigated by X-ray diffraction, field emission scanning electron microscopy, X-Ray photoelectron spectroscopy and high-resolution transmission electron microscopy for structure and composition test. The electrochemical performances of the composites are evaluated by cyclic voltammogram, galvanostatic charge-discharge and electrochemical impedance spectroscopy. Electrochemical measurements reveal that the maximum-specific capacitance of the MoS2/C electrodes reaches up to 1003 mAh g-1 at a discharge current density 100 mA g-1. The MoS2/C hybrid composite remains 755 mAh g-1 after 50 cycles at the current of 200 mA g-1, much higher than that of the pure MoS2. The superior electrochemical performances of MoS2/C composites as Li-ion battery anodes are attributed to their enhanced available active sites for charges, decreased transmission resistance between interlayers, improved electronic conductivity as well as good mechanical stability. [ABSTRACT FROM AUTHOR]

Abstract: Three‐dimensional porous SnO2/rGO xerogels with superior cycling performance in lithium‐ion batteries (LIBs) and sodium‐ion batteries (SIBs) are fabricated through a freeze‐drying‐assisted method. SnO2 nanoparticles (5 nm in diameter) are homogeneously attached to the surface of graphene sheets without self‐aggregation. The heterostructured SnO2/rGO xerogel possesses numerous micron‐sized pores that can efficiently buffer the volumetric change of SnO2 during the charge/discharge process and provide multidimensional channels, improving the conductivity between active materials and electrolyte. The SnO2/rGO xerogel exhibits excellent electrochemical performance, both in LIBs and SIBs, owing to its particular porous structure. For LIBs, it delivers a high initial discharge capacity of 1670.5 mAh g−1 in the first cycle and remains at 1139.4 mAh g−1 after 166 cycles at a current density of 0.1 A g−1. The SnO2/rGO xerogel also delivers a high discharge capacity of 189.4 mAh g−1 without capacity loss over 266 cycles at a current density of 0.5 A g−1 for SIBs. The SnO2/rGO xerogel can be used as an electrode material in both LIBs and SIBs, and can maintain an excellent rate performance and cyclic performance, owing to the abundant porosity and high conductivity. [ABSTRACT FROM AUTHOR]

Spinel LiMn2O4 is one of the most important cathode materials but it still suffers from rapid capacity degradation during electrochemical cycling. Beside surface coating to improve the electrochemical performances, controlling the bulk morphology of LiMn2O4 (LMO) is another effective strategy. In this work, porous LiMn2O4 microspheres composed of numerous primary nanoparticles are synthesized by micro-emulsion and co-precipitation methods. The porous structure and the primary nanoparticles size of LiMn2O4 are effected by the concentration of micro-emulsion and the precursor of Mn2+. The well-established porous LiMn2O4 microspheres with abundant ionic channels and good contact with electrolyte endow the spinel a remarkable electrochemical performance. After 300 cycles, 0.50 M-LMO sample presents excellent reversible capacity of 112.8 mAh g−1 at 0.5 C rate. After 1000 cycles, 0.50 M-LMO sample presents the highest capacity of 97.9 mAh g−1 and remains 54.2 mAh g−1 at the current rate of 10 C. The porous spherical structure of cathode materials is essential to improve the rate performance due to the good contact between the active material and electrolyte. [ABSTRACT FROM AUTHOR]

A series of composites manganese oxide/carbon with one-dimensional structure are synthesized using electrospinning. The phase composition, morphology and electrochemical performance of MnO x /carbon are studied, which affected by the manganese concentration in precursor and subsequent carbonization conditions. The manufacture of MnO x /carbon is composed of two steps including thermal stabilization (at 250 °C in air) and carbonization (at 700 °C in nitrogen). The main functional groups of samples are well identified by FT-IR spectra. The sample Mn33_3h with the lowest manganese content presents the construction structure which amorphous and/or nanosized MnO x with smaller crystal size are grown and enwrapped in carbon fiber during carbonization. Mn33_3h presents the initial charge and discharge capacities of 1054.1 and 665.6 mAh g−1, and the discharge capacity at the 50th cycle remains 99.7% of that at the 2nd cycle. Beside the well rate capability at the range of current densities from 20 to 1000 mA g−1, Mn33_3h presents very good recovery ability after high rate cycling at 1000 mA g−1. The advantages of this composite structure as well as its high capacity make manganese oxide a very attractive candidate as an anode material for the next generation of rechargeable lithium ion batteries. [ABSTRACT FROM AUTHOR]

Abstract: Monoclinic Li3V2(PO4)3 can be rapidly synthesized at 750°C for 5min (MW5m) by using temperature-controlled microwave solid-state synthesis method (TCMS). The carbon-free sample MW5m presents well electrochemical properties. In the cut-off voltage 3.0–4.3, MW5m presents a charge capacity 132mAhg−1, almost equivalent to the reversible cycling of two lithium ions per Li3V2(PO4)3 formula unit (133mAhg−1), and discharge capacity 126.4mAhg−1. In the cut-off voltage 3.0–4.8V, MW5m shows an initial discharge capacity of 183.4mAhg−1, near to the theoretical discharge capacity. In the cycle performance, the capacity fade of Li3V2(PO4)3 is dependent on the cut-off voltage and the preparation method. [Copyright &y& Elsevier]

Abstract: To substitute minor Mn2+ by the transition metal ion M=Mg2+, V3+, Fe2+, Co2+, or Gd3+, LiMn0.95M0.05PO4 samples are synthesized by a solid-state reaction route. The interpretation of doping effects is complicated by the interrelations between doping microstructure and morphology, because the crystal structure would be affected by the doped elements. The lattice structure and deviation of Li–O bond lengths of the doped LiMnPO4 are refined by XRD refinement. All the samples present a couple of oxidation and reduction peaks in cyclic voltammetry, corresponding to a redox Mn3+/Mn2+ reaction coupled with the extraction/reinsertion process of Li+ in LiMnPO4 structure. During charge/discharge process, the electron flowing and Li+ cation diffusion in the various doped LiMnPO4 samples should be different thermodynamic and kinetic process. For further studying which step in thermodynamic and kinetic process would affect or control the electrochemical performance, the initial charge/discharge capacities and cycleability of doped LiMnPO4 samples are obtained under different voltage range (from 2.7 to the upper cut-off voltage 4.4, 4.6 and 4.8V, respectively) and different environment temperatures (0, 25, and 50°C). At relative higher measuring temperature, the discharge capacity of Co-doped LiMnPO4 shows 151.9mAhg−1. [Copyright &y& Elsevier]