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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]

Graphical abstract Highlights • The α-Fe 2 O 3 grains were grafted onto the TiO 2 /CNFs via the vapor-solid reaction. • The TiO 2 /CNFs reserved void space to suppress the disintegration of the Fe 2 O 3. • The 3D network provide interstitial sites and enhanced pathways for Li+ and e−. Abstract α-Fe 2 O 3 grains grafted onto TiO 2 /carbon nanofibers (CNFs) for use as anode materials in lithium-ion batteries have been successfully fabricated by electrospinning and vapor-solid reaction (VSR). Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and N 2 adsorption-desorption isotherms reveal that the ultrafine α-Fe 2 O 3 nanoparticles were formed on the TiO 2 /CNFs and have uniform dispersion along the fiber direction. The VSR approach could retard nucleation, thus making TiO 2 /CNFs with small Fe 2 O 3 grains grafting (approximately 5 nm in diameter). The TiO 2 /CNFs are capable of buffering the large volume variation of α-Fe 2 O 3 during cycling and preventing electrode pulverization and aggregation, as well as providing sufficiently large interstitial space within the crystallographic structure to host Li ions. The electrochemical properties of the composite electrodes were tested by galvanostatic cycling at both constant and variable current rates. The composite delivers both good rate capability under an uprated current density of 1000 mA g−1 and especially enhanced cycle stability (∼600 mA h g−1 after 200 cycles at a current density of 1000 mA g−1). The super electrochemical performance is attributed to a synergetic effect between α-Fe 2 O 3 and TiO 2 -CNFs as well as the three- dimensional (3D) network, which contributes to greatly enhanced diffusion kinetics and structural stability for lithium-ion batteries. This VSR approach can be extended to other hierarchical metal oxide nanostructures for favorable applications in electrochemical devices. [ABSTRACT FROM AUTHOR]

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]