Hydrothermal synthesis of FeS2 for lithium batteries

Nanocrystalline FeS₂ cathode material of lithium cell was synthesized from cheap materials of FeSO₄, Na₂S₂O₃, and sulfur by a hydrothermal process. The scanning electron microscopy analysis showed the obtained material was nano-sized, about 500 nm. The X-ray powder diffraction analysis showed that the synthetic FeS₂ material had two phases of the crystalline structure, pyrite and marcasite. The phase of marcasite seems to have no negative effect on the electrochemical performance of the material. The synthetic FeS₂ showed a significant improvement of electrochemical performance for Li/FeS₂ cells.     

Enhanced cyclability of triple-metal-doped LiMn2O4 spinel as the cathode material for rechargeable lithium batteries

To improve the cycle performance of spinel LiMn₂O₄ as the cathode of 4-V-class lithium secondary batteries, spinel phases LiM _x Mn_2 − x O₄ (M=Li, Fe, Co; x = 0, 0.05, 0.1, 0.15) and LiFe_0.05M _y Mn_{1.95 − y} O₄ (M=Li, Al, Ni, Co; y = 0.05, 0.1) were successfully prepared using the sol–gel method. The spinel materials were characterized by powder X-ray diffraction (XRD), elemental analysis, and scanning electron microscopy. All the samples exhibited a pure cubic spinel structure without any impurities in the XRD patterns. Electrochemical studies were carried out using the Li|LiM _x Mn_2 − x O₄ (M=Li, Fe, Co; x = 0, 0.05, 0.1, 0.15) and LiFe_0.05M _y Mn_{1.95 − y} O₄ (M=Li, Al, Ni, Co; y = 0.05, 0.1) cells. These cathodes were more tolerant to repeated lithium extraction and insertion than a standard LiMn₂O₄ spinel electrode in spite of a small reduction in the initial capacity. The improvement in cycling performance is attributed to the stabilization in the spinel structure by the doped metal cations.     

Synthesis and characterization of LiMnBO3 cathode material for lithium ion batteries

LiMnBO₃ with enhanced powder density was successfully synthesized by a commercially available spray-drying process. A monoclinic-LiMnBO₃ single phase was experimentally substantiated by an X-ray diffractometer with crystallinity investigated by Rietveld refinement method (Bragg R-factor and RF-factor <10). The dense LiMnBO₃ powder prepared by the spray drying process showed spherical morphology. The electrochemical property of LiMnBO₃ was extensively investigated, positively revealing that 0.27 Li⁺ (Li_0.27MnBO₃) was stoichiometrically extracted from the host LiMnBO₃ material at first cycle.     

A novel approach to synthesize lithium ion battery spinel cathode materials

Spinel LiMn₂O₄ and LiMg_0.2Mn_1.8O₄ have been synthesized by a soft chemistry method using citric acid as the chelating agent and acryl amide as the gelling agent. This technique offers better homogeneity, preferred surface morphology, reduced heat treatment conditions, sub-micron-sized particles, and better crystallinity. The synthesized spinel materials are characterized by X-ray diffraction, scanning electron microscopy, cyclic voltammetry, and charge–discharge studies.     

Effects of binder content on manganese dissolution and electrochemical performances of spinel lithium manganese oxide cathodes for lithium ion batteries

In this study, the effects of the polyvinylidene fluoride (PVdF) binder on the Mn dissolution behavior and electrochemical performances of LiMn₂O₄ (LMO) electrodes are investigated. It is found that increasing the PVdF content (3, 5, 7, and 10 wt.%) leads to reduced Mn dissolution, and thus superior cycle performance at elevated temperature (60 °C). This can be ascribed to increased binder coverage on the LMO surface, as evidenced by X-ray photoelectron spectroscopy measurements, which acts a role as a passivation layer for Mn dissolution. The rate capability of the LMO electrode is hardly deteriorated as the PVdF content increases, despite the increasing surface coverage. Electrochemical impedance measurements reveal that the LMO electrode with higher binder loading exhibits lower electrode impedance, which is suggested to be due to enhanced electronic passage through the composite LMO electrode.     

Solution synthesis of boron substituted LiMn2O4 spinel oxide for use in lithium rechargeable battery

An attempt has been made to synthesize LiMn₂O₄ spinel and boron substituted LiMn₂O₄ with atomic concentration of boron ranging from 0.01–0.20 and using glutaric acid as a chelating agent. The spinels have been characterized using PXRD, CV and galvanostatic charge-discharge studies. The precursor obtained from the glutaric acid assisted gel was calcined initially at 300 °C for 4 h to obtain the compound and finally at 800 °C for 4 h so as to obtain homogeneity, high degree of purity and crystallinity for better electrochemical performance. This paper suggests that glutaric acid assisted B³⁺ doped (LiB_xMn_2−xO₄) spinel was found to be as an apt candidate with good electrochemical performance for use in lithium battery.     

Electrochemical properties of stacked-nanoflake Li4Ti5O12 spinel synthesized by a polymer-pyrolysis method

Stacked-nanoflake Li₄Ti₅O₁₂ spinel was synthesized via the pyrolysis of a Li–Ti copolymeric precursor formed by in situ polymerization of LiOH and [Ti(OC₄H₉)₄] and acrylic acid. XRD and SEM characterization shows that the powders calcined at 700 °C for 3 h was well-crystallized particles with submicron diameter. Charge–discharge measurement showed the Li₄Ti₅O₁₂ electrode had displayed excellent rate capability and delivered reversible capacity of 171, 158, 148, 138 and 99 mAh g⁻¹ at rates of 0.1C, 0.5C, 1C, 2C and 4C, respectively. The test electrode also showed excellent cyclability as the capacity retains 96.1% after 60 cycles between 0.5 and 2.5 V.     

Surface cleaning effect of NCM powder and improvement of lithium ion battery on the thermal stability and life cycle employing dielectric barrier discharge technique

Mixed NCM (nikel, cobalt, and manganese) powder was treated by a reactive gas from dielectric barrier discharge (DBD) to prepare a cathode material in Lithium ion (Li-ion) battery. The DBD was mainly sustained using N₂ gas at atmospheric pressure, and NF₃, SF₆, and H₂ was fed into the discharge to create the reactive gas. Compare to the non-treated sample, impurities on the surface of the NCM powder were significantly removed in a 5 min when the reactive gas was blow into the powder and mixed properly. F atom content on the surface was increased depending on the time duration of mixing, which form a LiF layer on the surface. Desirable LiF layer suppress a heat flow effectively , resulting a decreasing of exothermic temperature inside the Li-ion battery. Additionally, the treatment of NCM powder employing DBD technique was also contributed to electrochemical performance, which was confirmed by c-rate testing.     

Li4Ti2.5Cr2.5O12 as anode material for lithium battery

Chromium-substituted Li₄Ti₅O₁₂ has been investigated as a negative electrode for future lithium batteries. It has been synthesized by a solid-state method followed by quenching leading to a micron-sized material. The minimum formation temperature of Li₄Ti_2.5Cr_2.5O₁₂ was found to be around 600 °C using thermogravimetric and differential thermal analysis. X-ray diffraction, scanning electron microscopy, cyclic voltammetry (CV), impedance spectroscopy, and charge–discharge cycling were used to evaluate the synthesized Li₄Ti_2.5Cr_2.5O₁₂. The particle size of the powder was around 2–4 μm. CV studies reveal a shift in the deintercalation potential by about 40 mV, i.e., from 1.54 V for Li₄Ti₅O₁₂ to 1.5 V for Li₄Ti_2.5Cr_2.5O₁₂. High-rate cyclability was exhibited by Li₄Ti_2.5Cr_2.5O₁₂ (up to 5  C) compared to the parent compound. The conduction mechanism of the compound was examined in terms of the dielectric constant and dissipation factor. The relaxation time has been evaluated and was found to be 0.07 ms. The mobility was found to be 5.133 × 10⁻⁶ cm² V⁻¹ s⁻¹.     

Sonochemical synthesis of LiNi0.5Mn1.5O4 and its electrochemical performance as a cathode material for 5 V Li-ion batteries

LiNi_0.5Mn_1.5O₄ was synthesized as a cathode material for Li-ion batteries by a sonochemical reaction followed by annealing, and was characterized by XRD, SEM, HRTEM and Raman spectroscopy in conjunction with electrochemical measurements. Two samples were prepared by a sonochemical process, one without using glucose (sample-S1) and another with glucose (sample-S2). An initial discharge specific capacity of 130 mA h g⁻¹ is obtained for LiNi_0.5Mn_1.5O₄ at a relatively slow rate of C/10 in galvanostatic charge–discharge cycling. The capacity retention upon 50 cycles at this rate was around 95.4% and 98.9% for sample-S1 and sample-S2, respectively, at 30 °C.     

Synthesis and characterization of Co-doped lithium manganese oxide as a cathode material for rechargeable Li-ion battery

An attempt has been made to prepare cobalt-doped lithium manganese oxide with three different concentrations by simple molten salt method to enhance the electrical property of Li₄Mn₅O₁₂. Prepared samples were examined by XRD and SEM to identify its structure and morphology. Electrical properties were identified by impedance and conductivity analysis, and it was found that the material exhibits negative temperature coefficient (NTCR) property, i.e., semi-conducting nature. Among the various concentrations, 0.5 mol of Co-doped lithium manganese oxide has shown good conductivity of 3.1 × 10^?5 S cm^?1 at 433 K.     

Synthesis and characterization of Cr8O21 as cathode material for rechargeable lithium batteries

Pure phase Cr₈O₂₁ with excellent electrochemical properties has been synthesized by sintering anhydrous chromium trioxide (CrO₃) at low temperature in flowing oxygen. Cyclic voltammetry (CV) and X-ray diffraction (XRD) characterizations indicate that the inner tetra-chromate groups of Cr₈O₂₁ are damaged and Cr₈O₂₁ is changed to another layer-structured material when lithium is inserted into the host.     

Free-standing 3D Co3O4@NF micro-flowers composed of porous ultra-long nanowires as an advanced cathode material for supercapacitor

The development of smart structured cathode materials for supercapacitors (SCs) has sparked tremendous interest. However, the appropriate design to achieve high capacitance and energy density-based cathode materials remains a major problem for energy storage systems. This article describes the effective synthesis of self-supported 3D micro-flowers composed of ultrathin nanowires array of Co₃O₄ on Ni foam (NF) using hydrothermal conditions (Co₃O₄@NF). The mesoporous Co₃O₄@NF with a high surface area, providing a rich active state for the Faraday redox reaction and increasing the diffusion rate of the electrolyte ions. The optimized Co₃O₄@NF-16h electrode exhibited supreme electrochemical performance by delivering a high specific capacitance of 1878, (1127) and 1200 (720 C g⁻¹) F g⁻¹ at 1.0 and 20 A g⁻¹, respectively. The Co₃O₄@NF electrode retained good capacitance stability of 91% over 10000 cycles at 20 A g⁻¹ with excellent rate-performance of 67% at 20 folded high current values. The obtained results for the Co₃O₄@NF electrode are presented the enhanced pseudocapacitive performance, indicating the substantial potential for high-performance supercapacitor applications.     

First principles study on Mn-doped LiFePO4 as cathode material for rechargeable lithium batteries

The electronic structure and diffusion energy barriers of Li ions in pure and Mn-doped LiFePO4 have been studied using density functional theory （DFT）. The results demonstrate clearly that Fe - O covalent bond is weaker than P- O covalent bond. Pure LiFePO4 has band gap of 0.56 eV and diffusion energy barrier of 2.57 eV for Li ions, while the dopant has small band gap of 0.25 eV and low diffusion energy barrier of 2.31 eV, which indicates that the electronic and ionic conductivity of LiFePO4 have been improved owing to doping.     

First principles study on Mn-doped LiFePO4 as cathode material for rechargeable lithium batteries

The electronic structure and diffusion energy barriers of Li ions in pure and Mn-doped LiFePO4 have been studied using density functional theory(DFT).The results demonstrate clearly that Fe-O covalent bond is weaker than P-O covalent bond.Pure LiFePO4 has band gap of 0.56 eV and diffusion energy barrier of 2.57 eV for Li ions,while the dopant has small band gap of 0.25 eV and low diffusion energy barrier of 2.31 eV,which indicates that the electronic and ionic conductivity of LiFePO4 have been improved owing to doping.     

熔融盐法合成锂离子电池正极材料纳米LiNiO2

采用熔融盐法,在较低的温度和较短的时间制备了符合理论化学计量比的纳米LiNiO₂.研究表明,经过空气中的低温预烧,可以使制备的纯相纳米LiNiO₂具有更加优良的结晶性能和更佳的电化学特性.添加预烧步骤前后所得最终产物的初始容量分别为151和148 mAh ·g^-1,经过100周的循环,容量衰减到55和118 mAh ·g^-1,容量保持率分别为36.4%和79.7%.原因在于预烧后再进行煅烧降低了阳离子无序度,减少了混杂 关键词： 2')" href="#">LiNiO₂ 熔融盐法 锂离子电池 电化学性能     

Molten salt synthesis of Li1 + x (Ni0.5Mn0.5)1 − xO2 as cathode material for Li-ion batteries

Li_1 + x(Ni_0.5Mn_0.5)_1 − xO₂ cathode material for Li-ion batteries has been prepared by a molten salt method using Li₂CO₃ salt. The influences of synthetic temperature and time have been intensively investigated. It is easy to obtain materials with a hexagonal α-NaFeO₂ structure except broad peaks between 20° and 25°. Nickel in Li_1 + x(Ni_0.5Mn_0.5)_1 − xO₂ is oxidized to a trivalent state while manganese maintained a tetravalent state. It is found that the discharge capacities of all samples increase with cycling. The sample prepared at 850 °C for 5 h has a discharge capacity of 130 mAh g^− 1 between 2.5 and 4.5 V versus V_Li+/Li at a specific current of 0.13 mA cm^− 2 after 50 cycles at 25 °C.     

Structural and electronic properties of the Li-ion battery cathode material LixCoSiO4

The first-principles density functional theory has been employed to study the structural and electronic properties of Li_xCoSiO₄. The lattice stability of Li_xCoSiO₄ during the lithiation–delithiation process is discussed. The changes in the electronic structures of Li_xCoSiO₄ during the deintercalation of Li ions are also probed. It is found that Li₂CoSiO₄ reacts reversibly with 1 Li⁺ at an average voltage of 4.1 V versus a lithium anode. The computational results indicate that Li₂CoSiO₄ material is a potential candidate for high-capacity cathode for advanced lithium ion batteries.     

Kinetic aspects of Li intercalation in mechano-chemically processed cathode materials for lithium ion batteries: Electrochemical characterization of ball-milled LiMn2O4

Micrometric LiMn₂O₄ particles are mechano-chemically modified by ball-milling to obtain a mixture of nano- and micro-scale particles. This mixture is tested as a potential active cathode material for rapid-charge Li ion batteries, and also as a model system for studying the detailed kinetics of Li intercalation/de-intercalation in such electrodes. Ragone plots recorded using galvanostatic measurements indicate enhanced power delivery characteristics of the ball-milled LiMn₂O₄ compared to its unprocessed counterpart. The processed material also exhibits improved resistance against electrolyte reactions and surface film formation. Due to these advantageous electrochemical attributes, the ball-milled LiMn₂O₄ serves as an adequately suited system for exploring certain fundamental aspects of Li intercalation in this material. Scan rate dependent slow scan cyclic voltammetry helps to identify the kinetic and diffusion controlled features of Li transport in mechano-chemically processed LiMn₂O₄. Electrochemical impedance spectroscopy substantiates these findings further and provides detailed kinetic parameters, including voltage dependent charge transfer resistance and diffusion coefficient of Li transport.     

Nanophase ZnV2O4 as stable and high capacity Li insertion electrode for Li-ion battery

Spinel ZnV₂O₄ nanoparticles are synthesized by a hydrothermal method and its properties are characterized using XRD, SEM, TEM, and electrochemical test. The structural and morphological characterizations show that ZnV₂O₄ sample has high purity and well crystallization with crystal size less than 20 nm. The as prepared electrode shows stable capacity over 660 mAh g⁻¹ in the voltage range of 0.01–3.0 V at 50 mA g⁻¹. The reaction mechanism with lithium ion is also investigated through ex-XRD and -TEM. It shows that the pristine ZnV₂O₄ is transformed to isostructural spinel Li_xV₂O₄ (x close to 7.6) and metal Zn phase during the first lithiation process. Then the spinel Li_xV₂O₄ seems to perform a topotactic intercalation reaction mechanism and that the in-situ formed Li_xV₂O₄ can still keep its spinel matrix while allowing more than 5.7 lithium reversibly into/out over 50 cycles.