RESUMEN
There are plenty of issues need to be solved before the practical application of Li- and Mn-rich cathodes, including the detrimental voltage decay and mediocre rate capability, etc. Element doping can effectively solve the above problems, but cause the loss of capacity. The introduction of appropriate defects can compensate the capacity loss; however, it will lead to structural mismatch and stress accumulation. Herein, a three-in-one method that combines cation-polyanion co-doping, defect construction, and stress engineering is proposed. The co-doped Na+/SO42- can stabilize the layer framework and enhance the capacity and voltage stability. The induced defects would activate more reaction sites and promote the electrochemical performance. Meanwhile, the unique alternately distributed defect bands and crystal bands structure can alleviate the stress accumulation caused by changes of cell parameters upon cycling. Consequently, the modified sample retains a capacity of 273 mAh g-1 with a high-capacity retention of 94.1% after 100 cycles at 0.2 C, and 152 mAh g-1 after 1000 cycles at 2 C, the corresponding voltage attenuation is less than 0.907 mV per cycle.
RESUMEN
Cu2Se nanoflake arrays supported by Cu foams are synthesized by a facile hydrothermal method in this study. The Cu2Se materials are directly used as an anode for lithium ion batteries, which show superior cycle performance with significant capacity increase. Combining with previous reports and scanning electron microscope images after cycling, the capacity increase caused by the reversible growth of a polymeric film is discussed. Electrochemical impedance spectroscopy is used to test the reversible growth of the polymeric film. By analyzing the three-dimensional Nyquist plots at different potentials during the discharge/charge process, detailed electrochemical reaction information can be obtained, which can further verify the reversible formation of a polymeric film at low potential.
RESUMEN
To satisfy the increasing energy demands of portable electronics, electric vehicles, and miniaturized energy storage devices, improvements to lithium-ion batteries (LIBs) are required to provide higher energy/power densities and longer cycle lives. Group IVA element (Si, Ge, Sn)-based alloying/dealloying anodes are promising candidates for use as electrodes in next-generation LIBs owing to their extremely high gravimetric and volumetric capacities, low working voltages, and natural abundances. However, due to the violent volume changes that occur during lithium-ion insertion/extraction and the formation of an unstable solid electrolyte interface, the use of Group IVA element-based anodes in commercial LIBs is still a great challenge. Evaluating the electrochemical performance of an anode in a full-cell configuration is a key step in investigating the possible application of the active material in LIBs. In this regard, the recent progress and important approaches to overcoming and alleviating the drawbacks of Group IVA element-based anode materials are reviewed, such as the severe volume variations during cycling and the relatively brittle electrode/electrolyte interface in full-cell LIBs. Finally, perspectives and future challenges in achieving the practical application of Group IVA element-based anodes in high-energy and high-power-density LIB systems are proposed.
RESUMEN
In this study, Fe-Mn binary oxides, which harbor the strong oxidative power of manganese dioxide and the high adsorption capacity of iron oxides, were synthesized for Tl(I) removal using a concurrent chemical oxidation and precipitation method. The adsorption of Tl onto the Fe-Mn adsorbent was fast, effective, and selective, with equilibrium sorption reaching over 95% under a broad operating pH (3-12), and high ionic strength (0.1-0.5mol/L). The adsorption can be well fitted with both Langmuir and Freundlich isotherms, and the kinetics can be well described by the pseudo-second-order model. Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) spectra suggest that surface complexation, oxidation and precipitation were the main mechanisms for the removal of Tl. This study shows that the Fe-Mn binary oxides could be a promising adsorbent for Tl removal.
RESUMEN
Germanium is a highly promising anode material for lithium-ion batteries as a consequence of its large theoretical specific capacity, good electrical conductivity, and fast lithium ion diffusivity. In this work, Co3O4 nanowire array fabricated on nickel foam was designed as a nanostructured current collector for Ge anode. By limiting the voltage cutoff window in an appropriate range, the obtained Ge anode exhibits excellent lithium storage performance in half- and full-cells, which can be mainly attributed to the designed nanostructured current collector with good conductivity, enough buffering space for the volume change, and shortened ionic transport length. More importantly, the assembled Ge/LiCoO2 full-cell shows a high energy density of 475 Wh/kg and a high power density of 6587 W/kg. A high capacity of 1184 mA h g(-1) for Ge anode was maintained at a current density of 5000 mA g(-1) after 150 cycles.
RESUMEN
A Ni3S2 nanotube array has been synthesized on Ni foam using a template-free hydrothermal method. The Ni foam acts as both the reactant and support. The resulting architecture as an electrode for lithium ion batteries benefits from the unique morphology and exhibits excellent electrochemical performance with high capacity, long cycle life and superior rate capability.
RESUMEN
Carbon-wrapped Fe3O4 nanoparticle films on nickel foam were simply prepared by a hydrothermal synthesis with sucrose as a precursor of subsequent carbonization. The as-prepared samples were directly used as binder-free anodes for lithium-ion batteries which exhibited enhanced rate performance and excellent cyclability. A reversible capacity of 543 mA h g(-1) was delivered at a current density as high as 10 C after more than 2000 cycles. The superior electrochemical performance can be attributed to the formation of a thin carbon layer which constructs a 3D network structure enwrapping the nanosized Fe3O4 particles. Such an architecture can facilitate the electron transfer and accommodate the volume change of the active materials during discharge/charge cycling.
RESUMEN
We report a facile and reproducible synthesis of nanostructured Ni3S2 films by a hydrothermal route with Ni foam as the precursor reactant and substrate. The synthetic mechanism was examined by investigating the dependence of the films' crystal morphologies on the hydrothermal duration, and uniform nanostructured Ni3S2 films with a porous carpet-like morphology were synthesized on the substrates. The architectures were used as cathodes for lithium ion batteries (LIBs), and their electrochemical performances were evaluated as a function of the film thickness. The first discharge and charge capacities were 596 and 466 mA h g(-1) for the electrode with an optimal film thickness and a higher reversible capacity of 421 mA h g(-1) was obtained after 60 cycles at a current density of 50 mA g(-1). The simplicity of the synthetic methodology and the better electrochemical performance make the synthesized Ni3S2 films a promising cathode material for next-generation LIBs.
RESUMEN
Porous NiO-ZnO hybrid nanofibers were prepared by a single-nozzle electrospinning technique combined with subsequent heating treatment. The resultant nanofibers are composed of interconnected primary nanocrystals and numerous nanopores with heterostructures between NiO and ZnO. Such characteristics of the structure can lead to excellent electrochemical performances when the nanofiber was evaluated as an anode material for lithium-ion batteries. The porous NiO-ZnO nanofiber electrode delivers a high discharge capacity of 949 mA h g(-1) after 120 cycles at 0.2 A g(-1), and maintains around 707 mA h g(-1) at a current density as high as 3.2 A g(-1). Even after cycling at high rates, the electrode still retains a high discharge capacity of up to 1185 mA h g(-1) at 0.2 A g(-1).
