Synthesis of Monoclinic Li[Li0.2Mn0.54Ni0.13Co0.13]O2Nanoparticles by a Layered-Template Route for High-Performance Li-Ion Batteries

Coprecipitation-Gel Synthesis and Degradation Mechanism of Octahedral Li1.2Mn0.54Ni0.13Co0.13O2 as High-Performance Cathode Materials for Lithium-Ion Batteries

The octahedral core-shell Li-rich layered cathode material of Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ can be synthesized via an ingenious coprecipitation-gel method without subsequent annealing. On the basis of detailed X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and electron energy loss spectroscopy characterizations, it is suggested that the as-prepared material consists of an octahedral morphology and a new type of core-shell structure with a spinel-layered heterostructure inside, which is the result of overgrowth of the spinel structure with {111} facets on {001} facets of the layered structure in a single orientation. The surface area of Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ crystals where the spinel phase is located possesses sufficient Li and O vacancies, resulting in the reinsertion of Li into position after the first charge and maintenance of the interface stability via the replenishment of oxygen from the bulk region. Compared to that synthesized by the traditional coprecipitation method, the Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ synthesized by the coprecipitation-gel method exhibits higher discharge capacity and Coulombic efficiency, from 73.9% and 251.5 mAh g^-1 for the spherical polycrystal material to 86.2% and 291.4 mAh g^-1.

Understanding Voltage Decay in Lithium-Rich Manganese-Based Layered Cathode Materials by Limiting Cutoff Voltage

The effect of the cutoff voltages on the working voltage decay and cyclability of the lithium-rich manganese-based layered cathode (LRMO) was investigated by electrochemical measurements, electrochemical impedance spectroscopy, ex situ X-ray diffraction, transmission electron microscopy, and energy dispersive spectroscopy line scan technologies. It was found that both lower (2.0 V) and upper (4.8 V) cutoff voltages cause severe voltage decay with cycling due to formation of the spinel phase and migration of the transition metals inside the particles. Appropriate cutoff voltage between 2.8 and 4.4 V can effectively inhibit structural variation as the electrode demonstrates 92% capacity retention and indiscernible working voltage decay over 430 cycles. The results also show that phase transformation not only on high charge voltage but also on low discharge voltage should be addressed to obtain highly stable LRMO materials.

Cobalt-doped lithium-rich cathode with superior electrochemical performance for lithium-ion batteries

Cobalt doped to modify the structure of lithium-rich cathode and obtain the material with superior electrochemical performance.

Role of propane sultone as an additive to improve the performance of a lithium-rich cathode material at a high potential

This study presents the use of 1,3-propane sultone (PS) as a protective additive for the Li-rich-NMCxLi₂MnO₃–(1 −x)LiMO₂(x≫ 1; M = Ni, Co, Mn) cathode–electrolyte interface during cathode material activation and cycling at a high potential (5 Vvs.Li).

Li(1.2)Mn(0.6)Ni(0.1)Co(0.1)O2 microspheres constructed by hierarchically arranged nanoparticles as lithium battery cathode with enhanced electrochemical performance

Novel lithium-rich layered Li(1.2)Mn(0.6)Ni(0.1)Co(0.1)O2 microspheres containing hierarchically arranged and interconnected nanostructures have been synthesized by a combination of template-free co-precipitation and solid-state methods. The in situ formed γ-MnO2 spherical template upon co-precipitation gets sacrificed during the course of solid-state fusion of cobalt, nickel and lithium precursors to produce the title compound in the form of microspheres constructed by nanoparticles as building blocks. Porous and hollow microspheres of Li(1.2)Mn(0.6)Ni(0.1)Co(0.1)O2 are formed out of the spontaneous aggregation of nanoparticles, obtained from the custom-designed synthesis protocol. The growth mechanism of Li(1.2)Mn(0.6)Ni(0.1)Co(0.1)O2 spheres could be understood in terms of the Kirkendall effect and Ostwald ripening. The nanocrystalline Li(1.2)Mn(0.6)Ni(0.1)Co(0.1)O2 compound is obtained as a solid solution consisting of rhombohedral R3[combining macron]m and monoclinic C2/m group symmetries, as evidenced by XRD, Raman spectra and HRTEM equipped with FFT and STEM. The currently synthesized Li(1.2)Mn(0.6)Ni(0.1)Co(0.1)O2 cathode exhibits an appreciable discharge capacity of 242 mA h g(-1) at a current density of 50 mA g(-1), due to the synergistic effect of the capacity obtained from the rhombohedral and monoclinic phases.

Enhanced Li storage performance of LiNi(0.5)Mn(1.5)O(4)-coated 0.4Li(2)MnO(3)·0.6LiNi(1/3)Co(1/3)Mn(1/3)O(2) cathode materials for li-ion batteries

In this study, Li-rich cathode, 0.4Li2MnO3·0.6LiNi1/3Co1/3Mn1/3O2 was synthesized by a resorcinol formaldehyde assisted sol-gel method for the first time. Then, the surface of the as-prepared Li-rich cathode was modified with different amounts of LiNi0.5Mn1.5O4 (5, 10, and 20 wt %) through a simple dip-dry approach. The structural and electrochemical characterizations revealed that the spinel LiNi0.5Mn1.5O4 coating not only can prevent electrolytes from eroding the Li-rich core but also can facilitate fast lithium ion transportation. As a result, the 20 wt % coated sample delivered an initial discharge capacity of 298.6 mAh g(-1) with a Coulombic efficiency of 84.8%, compared to 281.1 mAh g(-1) and 70.2%, respectively, for the bare sample. Particularly, the coated sample demonstrates a Li storage capacity of 170.7 mAh g(-1) and capacity retention of 94.4% after 100 cycles at a high rate of 5 C (1250 mA g(-1)), showing a prospect for practical lithium battery applications. More significantly, the synthetic method proposed in this work is facile and low-cost and possibly could be adopted for large-scale production of surface-modified cathode materials.

K(+)-doped Li(1.2)Mn(0.54)Co(0.13)Ni(0.13)O2: a novel cathode material with an enhanced cycling stability for lithium-ion batteries

Li-rich layered oxides have attracted much attention for their potential application as cathode materials in lithium ion batteries, but still suffer from inferior cycling stability and fast voltage decay during cycling. How to eliminate the detrimental spinel growth is highly challenging in this regard. Herein, in situ K(+)-doped Li1.20Mn0.54Co0.13Ni0.13O2 was successfully prepared using a potassium containing α-MnO2 as the starting material. A systematic investigation demonstrates for the first time, that the in situ potassium doping stabilizes the host layered structure by prohibiting the formation of spinel structure during cycling. This is likely due to the fact that potassium ions in the lithium layer could weaken the formation of trivacancies in lithium layer and Mn migration to form spinel structure, and that the large ionic radius of potassium could possibly aggravate steric hindrance for spinel growth. Consequently, the obtained oxides exhibited a superior cycling stability with 85% of initial capacity (315 mA h g(-1)) even after 110 cycles. The results reported in this work are fundamentally important, which could provide a vital hint for inhibiting the undesired layered-spinel intergrowth with alkali ion doping and might be extended to other classes of layered oxides for excellent cycling performance.

Enhanced electrochemical performance with surface coating by reactive magnetron sputtering on lithium-rich layered oxide electrodes

Electrode films fabricated with lithium-rich layered 0.3Li2MnO3-0.7LiNi5/21Co5/21Mn11/21O2 cathode materials have been successfully modified with ZnO coatings via a reactive magnetron sputtering (RMS) process for the first time. The morphology and chemical composition of coating films on the electrodes have been in deep investigated by transmission electron microscopy (TEM), energy dispersive spectrometry (EDS), and X-ray photoelectron spectroscopy (XPS) characterizations. The results clearly demonstrate that ZnO film coatings are ultrathin, dense, uniform, and fully covered on the electrodes. The RMS-2 min (deposition time) coated electrode exhibits much higher initial discharge capacity and coulombic efficiency with 316.0 mAh g(-1) and 89.1% than that of the pristine electrode with 283.4 mAh g(-1) and 81.7%. In addition, the discharge capacity also reaches 256.7 and 187.5 mAh g(-1) at 0.1 and 1.0 C-rate, as compared to that of 238.4 and 157.8 mAh g(-1) after 50 cycles. The improved electrochemical performances of RMS-coated electrodes are ascribed to the high-quality ZnO film coatings that reduce charge transfer resistance and effectively protect active material from electrolyte oxidation.