Sub-micrometric LiCr0.2Ni0.4Mn1.4O4 spinel as 5 V-cathode material exhibiting huge rate capability at 25 and 55 °C

Single phase LiCr_0.2Ni_0.4Mn_1.4O₄ spinel has been synthesized by a simple sucrose assisted combustion method that yields highly crystalline homogeneous sub-micrometric samples (650 nm). The LiCr_0.2Ni_0.4Mn_1.4O₄, with capacity retention of 92% at 60 C discharge rate, shows the highest rate capability among LiNi_0.5Mn_1.5O₄-type cathodes. It delivers very high-power (34.8 kW kg^?1 at 60 C). Studies developed at 55 °C demonstrate that LiCr_0.2Ni_0.4Mn_1.4O₄ retains huge rate capability and large cycleability at high temperature.     

High performance LiNi0.5Mn1.5O4 cathode materials synthesized by a combinational annealing method

High performance LiNi_0.5Mn_1.5O₄ was prepared by a combinational annealing method. All samples were characterized by X-ray diffraction, infrared, and cell measurements. With increasing the annealing time at 600 °C, LiNi_0.5Mn_1.5O₄ showed a decreased lattice parameter and an enhanced Ni-ordering. The electrochemical property of LiNi_0.5Mn_1.5O₄ was optimized by controlling the annealing time. It was found that after annealing at 600 °C for 8 h, LiNi_0.5Mn_1.5O₄ can discharge up to 138 mA h g⁻¹ with a superior cycling performance at the rate of 5/7 C. High-rate test indicated that LiNi_0.5Mn_1.5O₄ exhibited excellent electrochemical performance when charged and discharged at 1.2 C and 2.5 C, respectively. The findings reported in this work are expected to pave the way for the practical application of LiNi_0.5Mn_1.5O₄.     

Lithium–manganese–nickel-oxide electrodes with integrated layered–spinel structures for lithium batteries

A series of lithium–manganese–nickel-oxide compositions that can be represented in three-component notation, xLi[Mn_1.5Ni_0.5]O₄ · (1 − x){Li₂MnO₃ · Li(Mn_0.5Ni_0.5)O₂}, in which a spinel component, Li[Mn_1.5Ni_0.5]O₄, and two layered components, Li₂MnO₃ and Li(Mn_0.5Ni_0.5)O₂, are structurally integrated in a highly complex manner, have been evaluated as electrodes in lithium cells for x = 1, 0.75, 0.50, 0.25 and 0. In this series of compounds, which is defined by the Li[Mn_1.5Ni_0.5]O₄–{Li₂MnO₃ · Li(Mn_0.5Ni_0.5)O₂} tie-line in the Li[Mn_1.5Ni_0.5]O₄–Li₂MnO₃–Li(Mn_0.5Ni_0.5)O₂ phase diagram, the Mn:Ni ratio in the spinel and the combined layered Li₂MnO₃ · Li(Mn_0.5Ni_0.5)O₂ components is always 3:1. Powder X-ray diffraction patterns of the end members and the electrochemical profiles of cells with these electrodes are consistent with those expected for the spinel Li[Mn_1.5Ni_0.5]O₄ (x = 1) and for ‘composite’ Li₂MnO₃ · Li(Mn_0.5Ni_0.5)O₂ layered electrode structures (x = 0). Electrodes with intermediate values of x exhibit both spinel and layered character and yield extremely high capacities, reaching more than 250 mA h/g with good cycling stability between 2.0 V and 4.95 V vs. Li° at a current rate of 0.1 mA/cm².     

Sulfone-based electrolytes for high-voltage Li-ion batteries

Sulfone-based electrolytes have been investigated as electrolytes for lithium-ion cells using high-voltage positive electrodes, such as LiMn₂O₄ and LiNi_0.5Mn_1.5O₄ spinels, and Li₄Ti₅O₁₂ spinel as negative electrode. In the presence of imide salt (LiTFSI) and ethyl methyl sulfone or tetramethyl sulfone (TMS) electrolytes, the Li₄Ti₅O₁₂/LiMn₂O₄ cell exhibited a specific capacity of 80 mAh g^?1 with an excellent capacity retention after 100 cycles. In a cell with high-voltage LiNi_0.5Mn_1.5O₄ positive electrode and 1 M LiPF₆ in TMS as electrolyte, the capacity reached 110 mAh g^?1 at the C/12 rate. When TMS was blended with ethyl methyl carbonate, the Li₄Ti₅O₁₂/LiNi_0.5Mn_1.5O₄ cell delivered an initial capacity of 80 mAh g^?1 and cycled fairly well for 1000 cycles under 2C rate. The exceptional electrochemical stability of the sulfone electrolytes and their compatibility with the Li₄Ti₅O₁₂ safer and stable anode were the main reason behind the outstanding electrochemical performance observed with high-potential spinel cathode materials. These electrolytes could be promising alternative electrolytes for high-energy density battery applications such as plug-in hybrid and electric vehicles that require a long cycle life.     

Comparison of structure and electrochemical properties for 5 V LiNi0.5Mn1.5O4 and LiNi0.4Cr0.2Mn1.4O4 cathode materials

Spinel LiNi_0.5Mn_1.5O₄ and LiMn_1.4Cr_0.2Ni_0.4O₄ cathode materials have been successfully synthesized by the sol–gel method using citric acid as a chelating agent. The structure and electrochemical performance of these as-prepared powders have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and the galvanostatic charge–discharge test in detail. XRD results show that there is a small Li _y Ni_1-y O impurity peak placed close to the (4 0 0) line of the spinel LiNi_0.5Mn_1.5O₄, and LiMn_1.4Cr_0.2Ni_0.4O₄ has high phase purity, and the powders are well crystallized. SEM indicates that LiMn_1.4Cr_0.2Ni_0.4O₄ has a slightly smaller particle size and a more regular morphological structure with narrow size distribution than those of LiNi_0.5Mn_1.5O₄. Galvanostatic charge–discharge testing indicates that the initial discharge capacities of LiMn_1.4Cr_0.2Ni_0.4O₄ and LiNi_0.5Mn_1.5O₄ cycled at 0.15 C are 129.6 and 130.2 mAh g⁻¹, respectively, and the capacity losses compared to the initial value, after 50 cycles, are 2.09% and 5.68%, respectively. LiMn_1.4Cr_0.2Ni_0.4O₄ cathode has a higher electrode coulombic efficiency than that of the LiNi_0.5Mn_1.5O₄ cathode, implying that Ni and Cr dual substitution is beneficial to the reversible intercalation and de-intercalation of Li⁺.     

High capacity Li[Li0.2Mn0.54Ni0.13Co0.13]O2–V2O5 composite cathodes with low irreversible capacity loss for lithium ion batteries

With an aim to suppress the huge irreversible capacity loss encountered in high capacity layered oxide solid solutions between Li₂MnO₃ and LiMO₂ (M = Mn, Ni, and Co), layered Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂–V₂O₅ composite cathodes with various V₂O₅ contents have been investigated. The irreversible capacity loss decreases from 68 mAh/g at 100% Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂ to 0 mAh/g around 89 wt.% Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂–11 wt.% V₂O₅ as the lithium-free V₂O₅ serves as an insertion host to accommodate the lithium ions that could not be inserted back into the layered lattice after the first charge. The Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂–V₂O₅ composite cathodes with about 10–12 wt.% V₂O₅ exhibit an attractive discharge capacity of close to 300 mAh/g with little irreversible capacity loss and good cyclability.     

Significant improved electrochemical performance of Li(Ni1/3Co1/3Mn1/3)O2 cathode on volumetric energy density and cycling stability at high rate

Li(Ni_1/3Co_1/3Mn_1/3)O₂ microspheres with a tap density of 2.41 g cm⁻³ have been synthesized for applications in high power and high energy systems, using a simple rheological phase reaction route. Cyclic voltammograms (CV) showed no shift of anodic and cathodic peaks centred at 3.81, 3.69 V for the Ni²⁺/Ni⁴⁺ couple after first cycle. The results of power pulse area specific impedance (ASI) and differential scanning calorimetry (DSC) tests showed lower power impedance and increased thermal stability of the electrode at high rate. These merits mentioned above provided significant improved capacity and rate performance for Li(Ni_1/3Co_1/3Mn_1/3)O₂ microspheres, which 159, 147 mAh g⁻¹ discharge capacity was delivered after 100 cycles between 2.5–4.6 V vs. Li at a different discharge rate of 2.5 C (500 mA g⁻¹), 5 C and a constant 0.5 C charge rate, respectively.     

Enhancing the rate capability of high capacity xLi2MnO3 · (1 − x)LiMO2 (M = Mn,Ni, Co) electrodes by Li–Ni–PO4 treatment

The rate capability of high capacity xLi₂MnO₃ · (1 ? x)LiMO₂ (M = Mn, Ni, Co) electrodes for lithium-ion batteries has been significantly enhanced by stabilizing the electrode surface by reaction with a Li–Ni–PO₄ solution, followed by a heat-treatment step. Reversible capacities of 250 mAh/g at a C/11 rate, 225 mAh/g at C/2 and 200 mAh/g at C/1 have been obtained from 0.5Li₂MnO₃ · 0.5LiNi_0.44Co_0.25Mn_0.31O₂ electrodes between 4.6 and 2.0 V. The data bode well for their implementation in batteries that meet the 40-mile range requirement for plug-in hybrid vehicles.     

A disordered rock-salt Li-excess cathode material with high capacity and substantial oxygen redox activity: Li1.25Nb0.25Mn0.5O2

A disordered rocksalt Li-excess cathode material, Li_1.25Nb_0.25Mn_0.5O₂, was synthesized and investigated. It shows a large initial discharge capacity of 287 mAh g^− 1 in the first cycle, which is much higher than the theoretical capacity of 146 mAh g^− 1 based on the Mn³⁺/Mn⁴⁺ redox reaction. In situ X-ray diffraction (XRD) demonstrates that the compound remains cation-disordered during the first cycle. Electron energy loss spectroscopy (EELS) suggests that Mn and O are likely to both be redox active, resulting in the large reversible capacity. Our results show that Li_1.25Nb_0.25Mn_0.5O₂ is a promising cathode material for high capacity Li-ion batteries and that reversible oxygen redox in the bulk may be a viable way forward to increase the energy density of lithium-ion batteries.     

A hierarchical micro/nanostructured 0.5Li2MnO3·0.5LiMn0.4Ni0.3Co0.3O2 material synthesized by solvothermal route as high rate cathode of lithium ion battery

A hierarchical micro/nanostructured Li-rich layered 0.5Li₂MnO₃·0.5LiMn_0.4Ni_0.3Co_0.3O₂ (H-LMNCO) material is prepared for the first time through the development of a solvothermal method, and served as cathode of lithium ion batteries. Electrochemical tests indicate that the H-LMNCO exhibits both a high reversible capacity and an excellent rate capability. The reversible discharge capacity of the H-LMNCO has been measured as high as 300.1 mAh·g^− 1 at 0.2 C rate. When the rate is increased to 10 C, the discharge capacity could still maintain a high value of 163.3 mAh·g^− 1. The results demonstrate that the developed solvothermal route is a novel synthesis strategy of preparing high rate performance Li-rich layered cathode material for lithium ion batteries.     

Li0.93[Li0.21Co0.28Mn0.51]O2 nanoparticles for lithium battery cathode material made by cationic exchange from K-birnessite

Li_0.93[Li_0.21Co_0.28Mn _0.51]O₂ nanoparticles with an R-3m space group is hydrothermally prepared from Co_0.35Mn_0.65O₂ obtained from an ion-exchange reaction with K-birnessite K_0.32MnO₂ at 200 °C. Even at a hydrothermal reaction temperature of 150 °C, the spinel (Fd3m) phase is dominant, and a layered phase became dominant by combining an increase in the temperature to 200 °C with an increase in lithium concentration. The as-prepared cathode particle has plate-like hexagonal morphology with a size of 100 nm and thickness of 20 nm. The first discharge capacity of the cathode is 258 mAh/g with an irreversible capacity ratio of 22%, and the capacity retention after 30 cycles is 95% without developing a plateau at ∼3 V. Capacity retention of the cathode discharge is 84% at 4C rate (=1000 mA/g) and shows full capacity recovery when decreasing the C rate to 0.1 C.     

Surface and in-depth characterization of lithium-ion battery cathodes at different cycle states using confocal micro-X-ray fluorescence-X-ray absorption near edge structure analysis

The cathode material LiNi_0.5Mn_1.5O₄ for lithium-ion batteries has been studied with confocal micro-X-ray fluorescence (CMXRF) combined with X-ray absorption near edge structure (XANES) at the Mn-K edge and the Ni-K edge. This technique allows for a non-destructive, spatially resolved (x, y and z) investigation of the oxidation states of surface areas and to some extent of deeper layers of the electrode. Until now CMXRF-XANES has been applied to a limited number of applications, mainly geo-science. Here, we introduce this technique to material science applications and show its performance to study a part of a working system. A novel mesoporous LiNi_0.5Mn_1.5O₄ material was cycled (charged and discharged) to investigate the effects on the oxidation states at the cathode/electrolyte interface. With this approach the degradation of Mn^3 + to Mn^4 + only observable at the surface of the electrode could be directly shown. The spatially resolved non-destructive analysis provides knowledge helpful for further understanding of deterioration and the development of high voltage battery materials, because of its nondestructive nature it will be also suitable to monitor processes during battery cycling.     

Synthesis and electrochemical properties of dual doped spinels LiNi_xAl_yMn_(2-x-y)O_4 via facile novel chelated sol–gel method as possible cathode material for lithium rechargeable batteries

LiMn_2O_4 and LiNi_xAlyMn_(2-x-y)O_4(x= 0.50;y = 0.05-0.50) powders have been synthesized via facile solgel method using Behenic acid as active cheiating agent.The synthesized samples are subjected to physical characterizations such as thermo gravimetric analysis(TG/DTA),X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),field-emission scanning electron microscopy(FESEM),transmission electron microscopy(TEM) and electrochemical studies viz.,galvanostatic cycling properties,electrochemical impedance spectroscopy(EIS) and differential capacity curves(dQ/dE).Finger print XRD patterns of LiMn_2O_4 and LiNi_xAl_yMn_(2-x-y)O_4 fortify the high degree of crystallinity with better phase purity.FESEM images of the undoped pristine spinel illustrate uniform spherical grains surface morphology with an average particle size of 0.5 μm while Ni doped particles depict the spherical grains growth(50nm) with ice-cube surface morphology.TEM images of the spinel LiMn_2O_4 shows the uniform spherical morphology with particle size of(100 nm) while low level of Al-doping spinel(LiNio.5Alo.05Mn1.45O4) displaying cloudy particles with agglomerated particles of(50nm).The LiMn_2O_4 samples calcined at 850℃ deliver the discharge capacity of 130 mAh/g in the first cycle corresponds to 94%coiumbic efficiency with capacity fade of 1.5 mAh/g/cycle over the investigated 10 cycles.Among all four dopant compositions investigated,LiNi_(0.5)Al_(0.05)Mn_(1.45)O_4 delivers the maximum discharge capacity of 126 mAh/g during the first cycle and shows the stable cycling performance with low capacity fade of 1 mAh/g/cycle(capacity retention of 92%) over the investigated 10 cycles.Electrochemical impedance studies of spinel LiMn_2O_4 and LiNi_(0.5)Al_(0.05)Mn_(1.45)O_4 depict the high and low real polarization of 1562 and 1100 Ω.     

Enhancing the electrochemical performance of Li1.2Ni0.2Mn0.6O2 by surface modification with nickel–manganese composite oxide

Li-rich layered Li_1.2Ni_0.2Mn_0.6O₂ has been surface modified by nickel–manganese composite oxide (Ni_0.5Mn_1.5O _x ) to serve as a novel cathode material with novel layered spinel structure for lithium-ion battery. The as-prepared Li_1.2Ni_0.2Mn_0.6O₂ before and after surface modification by Ni_0.5Mn_1.5O _x as well as simply blended Li_1.2Ni_0.2Mn_0.6O₂ with spinel LiNi_0.5Mn_1.5O₄, have been characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electronic microscopy, and differential scanning calorimetry. Electrochemical studies indicate that the Ni_0.5Mn_1.5O _x surface modified Li_1.2Ni_0.2Mn_0.6O₂ with peculiar layered spinel character dramatically represented increased discharge capacity, improved cycling stability as well as excellent rate capability at high-voltage even up to 5.0 V.     

Electrochemical properties of Li(Li(1−x)/3CoxMn(2−2x)/3)O2 (0 ⩽ x ⩽ 1) solid solutions prepared by poly-vinyl alcohol (PVA) method

The whole range of solid solutions Li(Li_(1−x)/3Co_xMn_(2−2x)/3)O₂ (0 ⩽ x ⩽ 1) was firstly synthesized by an aqueous solution method using poly-vinyl alcohol as a synthetic agent to investigate their structure and electrochemical properties. X-ray diffraction results indicated that the synthesized solid solutions showed a single phase without any detectable impurity phase and have a hexagonal structure with some additional peaks caused by monoclinic distortion, especially in the solid solutions with a low Co amount. In the electrochemical examination, the solid solutions in the range between 0.2 ⩽ x ⩽ 0.9 showed higher discharge capacity and better cyclability than LiCoO₂ (x = 1) on cycling between 2.0 and 4.6 V with 100 mA g⁻¹ at 25 °C. For example, Li(Li_0.2Co_0.4Mn_0.4)O₂ (x = 0.4) exhibited a high discharge capacity of 180 mA h g⁻¹ at the 50th cycle. By synthesizing the solid solution between Li₂MnO₃ and LiCoO₂, the electrochemical properties of the end members were improved.     

Improved electrochemical performance of LiNi0.5Mn1.5O4 as cathode of lithium ion battery by Co and Cr co-doping

Three samples, LiNi_0.5Mn_1.5O₄, LiNi_0.4Mn_1.4Co_0.2O₄, and LiNi_0.4Mn_1.4Cr_0.15Co_0.05O₄, were prepared by sol–gel method and characterized by powder X-ray diffraction, Fourier transformed infrared spectroscope, scanning electron microscopy, Brunauer–Emmett–Teller surface area, four-probe resistance, cyclic voltammetry, electrochemical impedance spectroscopy, and charge–discharge test. It is found that the co-doped sample LiNi_0.4Mn_1.4Cr_0.15Co_0.05O₄ exhibits an improved performance compared with the Co-doped sample LiNi_0.4Mn_1.4Co_0.2O₄ and the undoped sample LiNi_0.5Mn_1.5O₄, especially at elevated temperature. At 25 °C, the discharge capacity of LiNi_0.4Mn_1.4Cr_0.15Co_0.05O₄ is 130 mAh g^?1 at 0.1 C and 103 mAh g^?1 at 10 C. At an elevated temperature (55 °C), its 1 C discharge capacity is 136 mAh g^?1 and maintains 95.6 % of its initial capacity after 100 cycles. Compared with the reported results of LiNi_0.4Mn_1.4Co_0.2O₄ and LiNi_0.475Mn_1.475Co_0.05O₄, the co-doped sample LiNi_0.4Mn_1.4Cr_0.15Co_0.05O₄, with least content of Co, 0.05, possesses not only the high C-rate capacity but also the structural stability. The mechanism on the electrochemical performance improvement of LiNi_0.5Mn_1.5O₄ by the co-doping was discussed.     

LiMn2O4 hollow nanosphere electrode material with excellent cycling reversibility and rate capability

Lithium-rich Li_1.05Mn₂O₄ hollow nanospheres have been successfully prepared by air-calcining lithiated MnO₂ precursor at a low temperature of 550 °C, which was synthesized by chemical lithiation of hollow MnO₂ nanospheres with LiI at 70 °C for 12 h. The lithium-rich Li_1.05Mn₂O₄ hollow nanospheres exhibit an excellent cycling stability and rate capability as a cathode material for rechargeable lithium batteries: it maintains 90% of its initial capacity after 500 cycles, and keeps 70% of the reversible capacity at 0.1 C rat, even at 15 C rate.     

Lithium storage in hollow spherical ZnFe2O4 as anode materials for lithium ion batteries

Hollow microspheres composed of phase-pure ZnFe₂O₄ nanoparticles (hierarchically structured) have been prepared by hydrothermal reaction. The unique hollow spherical structure significantly increases the specific capacity and improves capacity retention of this material. The product of each phase transition during initial discharge (ZnFe₂O₄ ? Li_0.5ZnFe₂O₄ ? Li₂ZnFe₂O₄ → Li₂O + Li–Zn + Fe) and their structural reversibility are recognized by X-ray diffraction and electrochemical characterization. The products of the deeply discharged (Li–Zn alloy and Fe) and recharged materials (Fe₂O₃) were clarified based on high resolution transmission electron microscopic technique and first-principle calculations.     

High capacity and excellent cyclability of vanadium (IV) oxide in lithium battery applications

A VO₂ · 0.43H₂O powder with a flaky particle morphology was synthesized via a hydrothermal reduction method. It was characterized by scanning electron microscopy, electron energy loss spectroscopy, and thermogravimetric analysis. As an electrode material for rechargeable lithium batteries, it was used both as a cathode versus lithium anode and as an anode versus LiCoO₂, LiFePO₄ or LiNi_0.5Mn_1.5O₄ cathode. The VO₂ · 0.43H₂O electrode exhibits an extraordinary superiority with high capacity (160 mAh g^?1), high energy efficiency (95%), excellent cyclability (142.5 mAh g^?1 after 500 cycles) and rate capability (100 mAh g^?1 at 10 C-rate).     

Comments on stabilizing layered manganese oxide electrodes for Li batteries

An electrochemical study of structurally-integrated xLi₂MnO₃•(1 −x)LiMn_0.5Ni_0.5O₂ ‘composite’ materials has been undertaken to investigate the stability of electrochemically-activated electrodes at the Li₂MnO₃-rich end of the Li₂MnO₃–LiMn_0.5Ni_0.5O₂ tie-line, i.e., for 0.7 ≤ x ≤ 0.95. Excellent performance was observed for x = 0.7 in lithium half-cells; comparable to activated electrodes that have significantly lower values of x and are traditionally the preferred materials of choice. Electrodes with higher manganese content (x ≥ 0.8) showed significantly reduced performance. Implications for stabilizing low-cost, manganese-rich, layered lithium-metal-oxide electrode materials are discussed.