Low temperature synthesis of LiNi0.5Mn1.5O4 spinel

Pure LiNi_0.5Mn_1.5O₄ phase was prepared by one-step solid-state reaction at 600 °C in air. TG measurement revealed that the oxygen loss occurred when the mixed precursors were heated above 700 °C. X-ray diffraction (XRD) pattern and scanning electron microscopic (SEM) image indicated that LiNi_0.5Mn_1.5O₄ has cubic spinel structure with small and homogeneous particles. Electrochemical test showed that the prepared LiNi_0.5Mn_1.5O₄ delivered up to 138 mA h g^− 1, and the capacity retained 128 mA h g^− 1 after 30 cycles.     

Improvement of cycle stability at elevated temperature and high rate for LiNi0.5−xCuxMn1.5O4 cathode material after Cu substitution

A series of Cu-substituted LiNi_0.5−xCu_xMn_1.5O₄ (x = 0, 0.03, 0.05 and 0.08) spinels have been synthesized using a sol–gel method. The results demonstrate that when x = 0.05, the sample (LiNi_0.45Cu_0.05Mn_1.5O₄) exhibits the best electrochemical performance, achieving 124.5 mAh g⁻¹ and 115.0 mAh g⁻¹ at the discharge rates of 5 C and 20 C with the capacity retention of 97.7% and 95.7% after 150 cycles, respectively. Besides, the excellent cycle stability at 55 °C has been demonstrated to retain 96.8% of the maximum attainable discharge capacity (127.3 mAh g⁻¹) at the discharge rate of 5 C after 100 cycles. These data indicate that the LiNi_0.45Cu_0.05Mn_1.5O₄ cathode material has the real potential to be used for high power and high energy lithium ion battery in electric vehicle applications.     

Li4Ti5O12/Li3SbO4/C composite anode for high rate lithium-ion batteries

Nanocrystalline Li₄Ti₅O₁₂/Li₃SbO₄/C composite-prepared by mechanical ball-milling of Li₄Ti₅O₁₂ (synthesized by aqueous combustion), Li₃SbO₄ (synthesized by solid state method) and activated carbon, has been investigated as anode in lithium-ion coin cells and compared to pristine Li₄Ti₅O₁₂. Galvanostatic charge–discharge measurements in the potential window of 0.05–2.0 V show three plateau regions corresponding to Li insertion/extraction in the composite: a large flat plateau at ~ 1.52/1.59 V, followed by a second plateau at ~ 0.75/1.1 V and a sloppy tail at ~ 0.4/0.6 V. While the plateaus at ~ 0.4/0.6 V and ~ 1.52/1.59 V correspond to Li₄Ti₅O₁₂, the other one at ~ 0.75/1.1 V corresponds to Li₃SbO₄. At a high rate of ~ 15 C, the capacity for Li₄Ti₅O₁₂/Li₃SbO₄/C composite is found to be 105 mAhg^?1 retaining ~ 78% of its initial capacity compared to only 58 mAhg^?1 (~ 27% of the initial capacity) at 14 C for pristine Li₄Ti₅O₁₂ up to 100 cycles. Thus, such composite material might find application in lithium-ion batteries requiring high rate of charge and discharge.     

X-ray absorption spectroscopy studies of the Ni ion of Li(Ni0.8Co0.15Al0.05)0.8(Ni0.5Mn0.5)0.2O2 with a core–shell structure and LiNi0.8Co0.15Al0.05O2 as cathode materials

Core–shell materials have attracted a great deal of interest since core–shell particles have superior physical and chemical properties compared to their single-component counterparts. The cathode material Li(Ni_0.8Co_0.15Al_0.05)_0.8(Ni_0.5Mn_0.5)_0.2O₂ (LNCANMO) with a core–shell structure was synthesized via a co-precipitation method and investigated as the cathode material for lithium ion batteries. The core–shell particle consisted of LiNi_0.8Co_0.15Al_0.05O₂ (LNCAO) as the core and LiNi_0.5Mn_0.5O₂ as the shell. The cycling behavior between 2.8 and 4.3 V at a current of 0.1 C-rate showed a reversible capacity of ～195 mAh g^?1 with little capacity loss after 50 cycles. Extensive assessment of the electronic structures of the LNCAO and LNCANMO cathode materials was carried out using X-ray absorption spectroscopy (XAS). XAS has been used for structure refinement on the transition metal ion of the cathode. In particular, XAS studies of electrochemical reactions have been done from the viewpoint of the transition metal ion. In this study, Ni K-edge XAS spectra of the charge and discharge processes of LNCAO and LNCANMO were investigated.     

Electrochemical properties of 0.3Li2MnO3·0.7LiNi0.5Mn0.5O2 composite cathode powders prepared by large-scale spray pyrolysis

0.3Li₂MnO₃·0.7LiNi_0.5Mn_0.5O₂ composite cathode powders with a mixed-layer crystal structure comprising Li₂MnO₃ and LiNi_0.5Mn_0.5O₂ phases are prepared by spray pyrolysis. The composition of the cathode powders is found to be Li_1.19Ni_0.39Mn_0.61O₂ by ICP analysis. At a constant current density of 30 mA g^?1, the initial discharge capacities of the composite cathode powders post-treated at 700, 750, 800, and 850 °C are 177, 202, 215, and 212 mAh g^?1, respectively. The discharge capacity of the composite cathode powders post-treated at 800 °C decreases from 215 mAh g^?1 to 205 mAh g^?1 by the 40th cycle, in which the capacity retention is 95%. The first cycle has a low Coulombic efficiency of 75%. However, in the subsequent cycles, the Coulombic efficiency is retained at nearly 100%. The dQ/dV curves show that Mn exists as Mn⁴⁺ in the sample. The Mn⁴⁺ ions in the cathode powders become increasingly active as the cycle number increases and participate in the electrochemical reaction.     

Synthesis and electrochemical performance of Li1+xNi0.5Mn0.3Co0.2O2+δ (0 ≤ x ≤ 0.15) cathode materials for lithium-ion batteries

In this work, layered lithium-excess materials Li_1+xNi_0.5Mn_0.3Co_0.2O_2+δ (x = 0, 0.05, 0.10 and 0.15), of spherical morphology with primary nanoparticles assembled in secondary microspheres, were synthesized by a coprecipitation method. The effects of lithium content on the structure and electrochemical performance of these materials were evaluated by employing X-ray diffraction (XRD), inductive coupled plasma (ICP), scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and galvanostatic charge/discharge tests. It is found that Li_1.10Ni_0.5Mn_0.3Co_0.2O_2+δ, i.e., Li[(Ni_0.5Mn_0.3Co_0.2)_0.95Li_0.05]O₂ showed the best electrochemical performance due to the highly ordered layered structure, reduced cation mixing and the lowest charge transfer resistance. Li_1.10Ni_0.5Mn_0.3Co_0.2O_2+δ delivered a discharge capacity of 145 mA h g^?1 at 125 mA g^?1 in the cut-off voltage of 2.5–4.3 V, and had a capacity retention of 100% after 50 cycles at room temperature.     

From Bi4V2O11 to Li28Bi4V2O11 by electrochemical lithium insertion:: versatile applications in lithium batteries

The compound Bi₄V₂O₁₁ has been tested as a positive electrode in room temperature electrochemical lithium cells. When the cells are discharged down to 0.5 V the reaction of Bi₄V₂O₁₁ with 28 lithium ions develops a theoretical specific capacity of 700 A h kg⁻¹. Hence, this compound could be used as cathode in primary lithium batteries. Besides, we consider the fact that in the low voltage region (1.3–0.5 V) Li₂₈Bi₄V₂O₁₁ develops about 360 A h kg⁻¹ at 0.7 V, and, therefore, this material is proposed as a negative electrode in lithium ion batteries. The mechanism of the reaction of Bi₄V₂O₁₁ with 28 lithium ions is not yet fully understood, although some guidelines can be given.     

Synthesis and electrochemical properties of LiNi0.9Co0.1O2 cathode material for lithium secondary battery

Layered LiNi_0.9Co_0.1O₂ cathode material has been successfully synthesized with a calcination time of 0.5 h by a rheological phase reaction method. The obtained powder was characterized by X-ray diffraction (XRD), particle size and particle size distribution, scanning electronic microscope (SEM) and electrochemical measurements. The powder is confirmed to be α-NaFeO₂ structure. Cyclic voltammetry (CV) studies imply that the phase transitions from hexagonal to monoclinic exist during charge–discharge cycling. The LiNi_0.9Co_0.1O₂ cathode demonstrated a good electrochemical property with an initial discharge capacity of 193 mAh g^?1 and capacity retention of 88.6% after 15 cycles.     

Synthesis and electrochemical properties of LiNi0.375Co0.25Mn0.375−xCrxO2−xFx cathode materials prepared by sol–gel method

Layer-structured cathode material for lithium ion batteries LiNi_0.375Co_0.25Mn_0.375?xCr_xO_2?xF_x (0 ≤ x < 0.1) has been synthesized from sol–gel precursors. Its structure and electrochemical properties were investigated by X-ray diffraction (XRD) and a variety of electrochemical techniques. The XRD results reveal that LiNi_0.375Co_0.25Mn_0.375?xCr_xO_2?xF_x has typical hexagonal structure without impurity. The Cr–F co-doped materials show higher specific discharge capacity and improved cycling performance compared with the raw materials as x in the range of 0.00–0.06. LiNi_0.375Co_0.25Mn_0.315Cr_0.06O_1.94F_0.06 demonstrates an initial discharge capacity of 168.5 mAh g^?1 with 20th capacity retention about 93.7%. It has been confirmed that the improved cycling performance is derived from the little increase of electrochemical impedance during the cycling.     

Electrochemical properties of LiNi1−yTiyO2 and LiNi0.975M0.025O2 (M = Zn,Al, and Ti) synthesized by the solid-state reaction method

LiNi_1?yTi_yO₂ (y = 0.000, 0.012, 0.025, 0.050, 0.100, and 0.150) and LiNi_0.975M_0.025O₂ (M = Zn, Al, and Ti) were synthesized by the solid-state reaction method. The voltage vs. discharge capacity curves for y = 0.012 and y = 0.025 exhibit four distinct plateaus corresponding to phase transitions. Among LiNi_1?yTi_yO₂, LiNi_0.975Ti_0.025O₂ has the largest first discharge capacity, 154.8 mAh/g, at a rate of 0.1 C, and a relatively good cycling performance (77% at n = 10). Among LiNi_0.975M_0.025O₂ (M = Zn, Al, and Ti) samples, the LiNi_0.975Ti_0.025O₂ sample had the largest first discharge capacity. The LiNi_0.975Ti_0.025O₂ sample has sharper peaks for the ?dx/|dV| vs. V curves than the LiNi_0.975M_0.025O₂ (M = Zn and Al). The LiNi_0.975Al_0.025O₂ sample, with the first discharge capacity of 128.5 mAh/g at a rate of 0.1 C, has the best cycling performance (98% at n = 10).     

LixCo0.4Ni0.3Mn0.3O2 electrode materials: Electrochemical and structural studies

LiCo_0.4Ni_0.3Mn_0.3O₂ layered oxide in a member of the LiCo_1?2xNi_xMn_xO₂ solid solution between LiCoO₂ and LiNi_0.5Mn_0.5O₂. Compositions from this solid solution have attracted much attention and have been extensively studied as promising cathode candidates to replace the most popular LiCoO₂ cathode material used in the commercial lithium-ion batteries (LiBs). LiCo_0.4Ni_0.3Mn_0.3O₂ positive electrode material was prepared via the combustion method followed by a thermal treatment at 900 °C for 12 h. This material was characterized by a high homogeneity and a granular shape. The Rietveld refinement evidenced that the structure of this compound exhibits no Ni/Li disorder revealing that the LiCo_1?2xNi_xMn_xO₂ system presents the ideal structure for LiBs application when x < 0.4. The electrochemical performances of the LiCo_0.4Ni_0.3Mn_0.3O₂ sample were measured at different current rates in the 2.7–4.5 V potential range. Its discharge capacity reached 178, 161 and 145 mAhg^?1 at C/20, 1C and 2C, respectively. Structural changes in LiCo_0.4Ni_0.3Mn_0.3O₂ upon delithiation were studied using ex situ X-ray diffraction. A continuous solid solution with a rhombohedral symmetry was detected in the whole composition range. This structural stability during the cycling combined with the obtained electrochemical features make this material convenient for the LiBs applications.     

Synthesis and electrochemical behavior of a new layered cathode material LiCo1/2Mn1/3Ni1/6O2

A new layered type lithium nickel manganese cobalt oxide with the composition of LiCo_1/2Mn_1/3Ni_1/6O₂ was synthesized by using a layered double hydroxides (LDHs) as precursor and solid state reaction method. Phase-pure LiCo_1/2Mn_1/3Ni_1/6O₂ was obtained when the mixed precursors of NiMnCo–LDHs and LiOH·H₂O were calcined at 750 °C for 12 h. It showed discharge capacity of 180 and 148 mAh/g in the first cycle, corresponding to the discharge voltage ranges of 2.5–4.5 and 2.5–4.2 V, respectively, and still delivered 173 and 140 mAh/g after 60 cycles at room temperature, which represented favorable capacity retention upon cycling. This material was expected as a potential alternative of cathode material to be used for Li-ion secondary battery because of its good electrochemical performance and lower synthesis cost.     

Effect of Fe and Co doping on electrical and thermal properties of La0.5Ce0.5Mn1−x(Fe,Co)xO3 manganites

The effect of Fe and Co doping on structural, electrical and thermal properties of half doped La_0.5Ce_0.5Mn_1−x(Fe, Co)_xO₃ is investigated. The structure of these crystallizes in to orthorhombically distorted perovskite structure. The electrical resistivity of La_0.5Ce_0.5MnO₃ exhibits metal-semiconductor transition (T_MS at ∼225 K). However, La_0.5Ce_0.5Mn_1−xTM_xO₃ (TM = Fe, Co; 0.0 ≤ x ≤ 0.1) manganites show semiconducting behavior. The thermopower measurements infer hole as charge carriers and electron–magnon as well spin wave fluctuation mechanism are effective at low temperature domain and SPC model fits the observed data at high temperature. The magnetic susceptibility measurement confirms a transition from paramagnetic to ferromagnetic phase. The observed peaks in the specific heat measurements, shifts to lower temperatures and becomes progressively broader with doping of transition metals on Mn-site. The thermal conductivity is measured in the temperature range of 10–350 K with a magnitude in between 10 and 80 mW/cm K.     

Synthesis,characterization and electrochemical studies on LiCoAsO4

LiCoAsO₄ is synthesized by solid state reaction method and its crystal structure has been refined by the Rietveld method using powder X-ray diffraction data. LiCoAsO₄ crystallizes in olivine structure with space group Pnma and orthorhombic lattice parameters are a = 10.4614(2) Å, b = 5.9970(1) Å and c = 4.8866(1) Å. Electrochemical studies reveal that in LiCoAsO₄, lithium is deintercalated and intercalated at high voltage ∼5.0 V. On the other hand, the compound can react with about 9Li on discharge to 0.05 V. A reversible capacity of ∼100 mAh/g is obtained in the voltage range 1.0–2.5 V.     

Synthesis and characterization of a new inverse spinel LiNi1/3Co1/3Mn1/3VO4 for lithium-ion batteries

An electrochemically active LiNi_1/3Co_1/3Mn_1/3VO₄ cathode material was synthesized by a citric acid:polyethylene glycol (CA:PEG) polymeric method, followed by calcination at 723 K for 5 h in air. X-ray diffraction (XRD) patterns showed the complete formation of a crystalline phase occurred when heated at 723 K. Scanning electron microscope (SEM) micrographs showed the various stages of morphology for the polymeric intermediates of the LiNi_1/3Co_1/3Mn_1/3VO₄ compound. Transmission electron microscope (TEM) imaging exposed that particle size ranged from ∼170 to 190 nm. The cells using LiNi_1/3Co_1/3Mn_1/3VO₄ as a cathode could be cycled between 2.8 and 4.9 V (vs. Li) at a current rate of 0.15C. The galvanostatic cycling study suggests that cycle stability and capacity retention were enhanced for LiNi_1/3Co_1/3Mn_1/3VO₄ prepared with a CA:PEG ratio of 3 : 1. The dQ/dV vs. voltage plots revealed the redox potentials and slower impedance growth for the synthesized LiNi_1/3Co_1/3Mn_1/3VO₄ cathode material.     

Synthesis and modification of non-stoichiometric spinel (Li1.02Mn1.90Y0.02O4−yF0.08) for lithium-ion batteries

A non-stoichiometric spinel phase (Li_1.02Mn_1.90Y_0.02O_4?yF_0.08) was synthesized using a natural polymer sol–gel method. It was characterized by X-ray diffraction. The particle size and shape of the as-prepared compounds were observed by scanning electron microscope. The new compound was coated with LiBO₂, and the effects of the LiBO₂ coating on Li_1.02Mn_1.90Y_0.02O_4?yF_0.08 spinel phase were investigated. The results showed that pure Li_1.02Mn_1.90Y_0.02O_4?yF_0.08 had good electrochemical properties, however, the non-stoichiometric spinel coated with LiBO₂ showed better electrochemical performance at both room temperature and high temperature (50 °C) than pure Li_1.02Mn_1.90Y_0.02O_4?yF_0.08. The initial discharge capacity of the LiBO₂-coated non-stoichiometric spinel was 118 mAh g^?1 at a current density of 1 mA cm^?2 over the voltage range from 3.0 to 4.4 V. The discharge capacity was about 99.2% of the initial capacity after 100 cycles at room temperature and about 95.2% after 50 cycles at high temperature (50 °C). The modification of spinel with LiBO₂ effectively improved the electrochemical properties of non-stoichiometric spinel as a cathode material.     

High surface area nanocrystalline hausmannite synthesized by a solvent-free route

Nanocrystalline high surface area Mn₃O₄ powder was obtained at low temperature by a solvent-free route. The precursor was a mixture of manganese (II) acetate, 3,6,9-trioxadecanoic acid (TODA) and ammonium acetate that were intimately mixed by grounding in an agate mortar. Nanocrystalline Mn₃O₄ was obtained by thermal treatment at 120 °C. Powder X-ray diffraction, selected area electron diffraction, high resolution transmission electron microscopy, and Fourier transformed infrared characterization confirmed the formation of the hausmannite phase. The as-prepared mesoporous material has high specific surface area (120 m² g^?1). The performances of tape casted Mn₃O₄ nanopowder electrodes were investigated as anode material for lithium ion batteries. High capacity values were achieved at diverse C rates. Capacity fading was found to be dependent on the upper cut off voltage, the presence of a plateau at 2.25 V vs. Li⁺/Li being detrimental for long term cyclability.     

Recent progress on nanostructured 4 V cathode materials for Li-ion batteries for mobile electronics

Mobile electronics have developed so rapidly that battery technology has hardly been able to keep pace. The increasing desire for lighter and thinner Li-ion batteries with higher capacities is a continuing and constant goal for in research. Achieving higher energy densities, which is mainly dependent on cathode materials, has become a critical issue in the development of new Li-ion batteries. In this review, we will outline the progress on nanostructured 4 V cathode materials of Li-ion batteries for mobile electronics, covering LiCoO₂, LiNi_xCo_yMn_1?x?yO₂, LiMn₂O₄, LiNi_0.5Mn_1.5O₄ and Li-rich layered oxide materials. We aim to provide some scientific insights into the development of superior cathode materials by discussing the advantages of nanostructure, surface-coating, and other key properties.     

Synthesis and luminescence properties of CaAl2O4:Mn4+ phosphor

CaAl_2−yO₄:yMn⁴⁺ (y = 0–1.6 mol%) phosphors are synthesized by a solid-state reaction method in air, and their crystal structure and luminescence property are investigated. To compare luminescence property, CaAl_3.99O₇:1%Mn⁴⁺ and SrAl_1.99O₄:1%Mn⁴⁺ phosphors are also synthesized at the same condition. Broad band excitation spectra are observed within the range 220–550 nm, and emission spectra cover from 600 to 720 nm with the strongest emission peak at ∼658 nm owing to the ²E → ⁴A₂ transition of Mn⁴⁺ ion. The influence of crystal field to luminous intensity is discussed, and the possible luminous mechanism of Mn⁴⁺ ion is explained by using energy level diagram of Mn⁴⁺ ion. CaAl_1.99O₄:1%Mn⁴⁺, CaAl_3.99O₇:1%Mn⁴⁺, and SrAl_1.99O₄:1%Mn⁴⁺ phosphors under excitation 325 nm light emit red light, and their CIE chromaticity coordinates are (0.7181, 0.2813), (0.7182, 0.2818), and (0.7198, 0.2801), respectively. These contents in the paper are helpful to develop novel and high-efficient Mn⁴⁺-doped phosphor for white LEDs.     

Solution combustion synthesis of LiMn2O4 fine powders for lithium ion batteries

In this work, fine powders of spinel-type LiMn₂O₄ as cathode materials for lithium ion batteries (LIBs) were produced by a facile solution combustion synthesis using glycine as fuel and metal nitrates as oxidizers. Single phase of LiMn₂O₄ products were successfully prepared by SCS with a subsequent calcination treatment at 600–1000 °C. The structure and morphology of the powders were studied in detail by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The electrochemical properties were characterized by galvanostatic charge–discharge cycling and cyclic voltammetry. The crystallinity, morphology, and size of the products were greatly influenced by the calcination temperature. The sample calcined at 900 °C had good crystallinity and particle sizes between 500 and 1000 nm. It showed the best performance with an initial discharge capacity of 115.6 mAh g⁻¹ and a capacity retention of 93% after 50 cycles at a 1 C rate. In comparison, the LiMn₂O₄ sample prepared by the solid-state reaction showed a lower capacity of around 80 mAh g⁻¹.