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.     

The all-solid-state battery with vanadate glass-ceramic cathode

The Ga-Ag-Li|Li₇La₃Zr_1.89Al_0.15O₁₂|(Li₂O–B₂O₃–V₂O₅ + Fe) all-solid-state electrochemical cell has been designed with a simple sintering process. The Li₇La₃Zr_1.89Al_0.15O₁₂ solid electrolyte was prepared by sol-gel method. The lithium borovanadate glass was obtained by a convenient melt quenching technique. Cycliс voltammetry has shown that the current densities of the cell at 300 °C can reach several hundreds of μA cm^?2. At this temperature, the single cell voltage is about 3.2 and 0.8 V in the charged and discharged state, correspondingly. This cell produces a current enough to make a single LED of white color working. The cell surface discharge capacity exceeds 230 μAh cm^?2.     

Enhancement of electrochemical performance in lithium-ion battery via tantalum oxide coated nickel-rich cathode materials

Nickel-rich cathode materials are increasingly being applied in commercial lithium-ion batteries to realize higher specific capacity as well as improved energy density. However, low structural stability and rapid capacity decay at high voltage and temperature hinder their rapid large-scale application. Herein, a wet chemical method followed by a post-annealing process is utilized to realize the surface coating of tantalum oxide on LiNi_0.88Mn_0.03Co_0.09O₂, and the electrochemical performance is improved. The modified LiNi_0.88Mn_0.03Co_0.09O₂ displays an initial discharge capacity of ～ 233 mAh/g at 0.1 C and 174 mAh/g at 1 C after 150 cycles in the voltage range of 3.0 V-4.4 V at 45℃, and it also exhibits an enhanced rate capability with 118 mAh/g at 5 C. The excellent performance is due to the introduction of tantalum oxide as a stable and functional layer to protect the surface of LiNi_0.88Mn_0.03Co_0.09O₂, and the surface side reactions and cation mixing are suppressed at the same time without hampering the charge transfer kinetics.     

VSe2−xSx materials as battery cathode

The properties of the solid solution VSe_2?xS_x 0 ? x_nom ? 2 have been investigated for secondary battery application. The phase VSe₂ is observed for 0 ? x_nom ? 1.2 and the phase V₅S₈ is found using RX analysis for x_nom >1.2. The amount of lithium chemically incorporated in this structure by reaction with n-butyllithium is 2 Li/vanadium for 0 ? x_nom ? 0.8 and 1.4 Li/vanadium for V₅S₈. An electrochemical technique (galvanostatic) indicates that the amount of lithium incorporated depends on the x_nom values, the grain size and the discharge rate. The best results are obtained for 0.2 ? x_nom ? 0.6 (capacity = 164?172 Ah kg^?1 and energy density = 385?465 Wh kg^?1).     

Synthesis and electrochemical characterization of olivine-type lithium iron phosphate cathode materials via different techniques

High-potential, eco-friendly LiFePO₄ cathode materials were synthesized by polyol, hydrothermal, and solid-state reaction methods. The polyol technique was carried out without any special atmosphere and postheat treatment. The synthesized samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectrometry (XPS), and charge-discharge and cyclic voltammetry tests. The LiFePO₄ prepared via polyol technique exhibits good electrochemical performance than other method samples do.

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Electrochemical properties of disordered cathode materials

Disordered and amorphous compounds sometimes show better properties as cathodes than crystalline compounds of the same material in lithium electrochemical devices. In the present work, we have considered molybdenum compounds such as MoO₃ and MoS₂ having different degrees of structural disorder which are being extensively investigated as intercalation hosts of lithium for applications in rechargeable batteries or electrochromic devices. In this connection, their potential-composition curves have been measured as thermodynamic characteristic which is very important from both fundamental and practical point of view. Considering both ionic and electronic contributions to the charge/discharge behavior, the electrochemical features are discussed from the point of view of energy diagrams. Paper presented at the 3rd Euroconference on Solid State Ionics, Teulada, Sardinia, Italy, Sept. 15–22, 1996     

Preparation and characterization of Li1.2Ni0.13Co0.13Mn0.54O2 cathode materials for lithium-ion battery

Lithium-rich cathode materials Li_1.2Ni_0.13Co_0.13Mn_0.54O₂ with (sample SF) and without (sample SP) formamide was synthesized by a spray-dry method. The crystalline structure and particle morphology of as-prepared materials were characterized by X-ray diffraction and scanning electron microscope. The specific surface area (SSA) of the Li_1.2Ni_0.13Co_0.13Mn_0.54O₂ prepared from different routes was determined by a five-point Brunauer–Emmett–Teller (BET) method using N₂ as absorbate gas. Being compared with the material synthesized without spray-drying process (sample CP), sample SP has much higher SSA. The additive formamide is helpful to form regular and solid precursor particles in spray-drying process, which results in a slightly aggregation of grains and reduction of SSA for sample SF. The electrochemical activities of the materials are closely related to their morphology and SSA. In the voltage range of 2–4.8 V at 25 °C, sample SP present a discharge capacity of 257 mAh g^?1 at 0.1 C rate and 170 mAh g^?1 at 1 C rate. The sample CP delivered only 136 mAh g^?1 when discharged at 1 C rate. The elevated specific capacity and rate capability are attributed to smaller primary particle and higher SSA. Both cycle performance and rate capability of Li_1.2Ni_0.13Co_0.13Mn_0.54O₂ were improved when formamide was used in spray-dry process. Discharge capacity of SF is 140.5 mAh g^?1 at 2 C rate, and that of SP is 132.3 mAh g^?1. Overlarge SSA of SP may provoke serious side reaction, so that its electrochemical performance was deteriorated.     

Dynamic structural form-factor of quasi-one-dimensional ferroelectrics with random impurities

We consider a one-dimensional model of displacive structural phase transitions with random temperature-type impurities. The modification to the central peak is calculated. It is shown that random-temperature impurities lead to a divergence in the central peak intensity. We find good agreement between our results and the experimental temperature dependence of the central peak.Translated from Izvestiya Vysshikh Uchebnikh Zavedenii, Fizika, No. 4, pp. 57–62, April, 1988.     

Performance of solid state protonic battery with different cathodes

To establish the fact that the performance of a solid state battery is predominantly governed by the cathode, primary electrochemical cells were fabricated using FeH(SO₄)₂-xH₂O solid electrolyte having proton transport number close to unity (prepared by chemical route) taken in conjunction with five different cathodes MnO₂, PbO₂, V₆O₁₃, I₂ and TMAI iodine complex. Amongst these, better discharge characteristics along with thermodynamic and chemical stability of the cell were offered by TMAI iodine complex based cathode. Beside these, it provided short-circuit current, capacity and energy density of the order of 5 mA 4.5 mAh and 2.67 Wh/kg respectively due to the presence of highly active iodine, which is not free in TMAI compared to the cathode made of simply I₂. Paper presented at the 2nd International Conference on Ionic Devices, Anna University, Chennai, India, Nov. 28–30, 2003.     

High-throughput theoretical design of lithium battery materials

The rapid evolution of high-throughput theoretical design schemes to discover new lithium battery materials is reviewed, including high-capacity cathodes, low-strain cathodes, anodes, solid state electrolytes, and electrolyte additives.With the development of efficient theoretical methods and inexpensive computers, high-throughput theoretical calculations have played an increasingly important role in the discovery of new materials. With the help of automatic simulation flow,many types of materials can be screened, optimized and designed from a structural database according to specific search criteria. In advanced cell technology, new materials for next generation lithium batteries are of great significance to achieve performance, and some representative criteria are: higher energy density, better safety, and faster charge/discharge speed.     

Characterization of Na-substituted LiNi1/3Co1/3Mn1/3O2 cathode materials for lithium-ion battery

Highly crystalline layered Li_1?xNa_xNi_1/3Co_1/3Mn_1/3O₂ (x?=?0, 0.001, 0.01, 0.03, 0.05) materials are synthesized by molten salts method and characterized by scanning electron microscopy, inductively coupled plasma (ICP), X-ray diffraction, Rietveld refinement, and electrochemical measurement, respectively. ICP, SEM, and EDS results show that Na ions are incorporated in LiNi_1/3Co_1/3Mn_1/3O₂. Rietveld refinement results show that suitable Na substitution leads to stable layered structure by full Na occupying in Li layer and further attributes to low cation mixing. Electrochemical studies demonstrate that the Na-substituted LiNi_1/3Co_1/3Mn_1/3O₂ shows improved rate capability and cycling performance compared to that of pure LiNi_1/3Co_1/3Mn_1/3O₂.     

常见场致发射阴极材料的发射特性

利用三阴极加速器平台,对不锈钢、黄铜、铝、天鹅绒和石墨等几种常见场致发射材料的电流发射能力、相对启动延迟时间及其抖动进行了实验研究。实验结果表明：在二极管电压近似恒定时,不锈钢阴极启动时间延迟抖动小于8 ns,天鹅绒阴极及石墨阴极启动时间延迟抖动小于4 ns;且材料在阴极频繁工作时启动时间加快;常见金属材料中不锈钢阴极的综合性能较好;非金属材料中,天鹅绒阴极的发射能力最强,且发射延迟时间最短,但考虑到天鹅绒材料严重的出气问题,非金属材料中以石墨阴极的性能为优。     

Storage performance with different charged state of manganese spinel battery

The power battery was manufactured with the commercial LiMn₂O₄ and graphite, and its storage performances with different charged state were studied. Structure, morphology, and surface-state change of the LiMn₂O₄ before and after storage were observed by XRD, SEM, XPS, CV, and AC technique, respectively. The electrochemical performances of LiMn₂O₄ battery were tested. The result shows that the capacity recovery of LiMn₂O₄ stored at discharge state is best (99.2%). While that of full-charged state is worst (93.6%). The cyclic performance of LiMn₂O₄ battery after storage is improved. The cyclic performance of LiMn₂O₄ stored at full-charged state is best (capacity retention ratio of 89.8% after 200?cycles), while that of before storage is 83.0%. The crystal of the spinel was destroyed after storage, and the intensity of breakage is increased with charge state increasing. The amount of soluble Mn and Li-ion migration resistance (R _f) are increased with charge state increasing, and the oxygen loss is detected.     

Gunn diodes with different cathode contacts oscillation on harmonic frequencies

The studies of Gunn diodes on the basis of GaAs with different types of cathode contacts, the profile of doping, the active area length and temperature at frequencies of the second and third harmonics were carried out to obtain effective oscillation in the millimeter and submillimeter ranges.     

Comparative study of LiNi0.05Mn1.95O4 powders prepared by different materials for Li-ion battery

LiNi_0.05Mn_1.95O₄ powders were prepared by manganese tetraoxide (MTO) and electrolytic manganese dioxide (EMD). The phase identification, surface morphology, and electrochemical properties of the prepared powders were studied by X-ray diffraction, scanning electron microscopy, cyclic voltammetry, and galvanostatic charge?Cdischarge experiments. Compared to LiNi_0.05Mn_1.95O₄ powders prepared by EMD, LiNi_0.05Mn_1.95O₄ powders prepared by MTO show better crystallinity. Both powders possess a typical cubic structure with uniform particle size. The specific capacity and coulombic efficiency of LiNi_0.05Mn_1.95O₄ powders prepared by MTO are higher than the one prepared by EMD. The capacity retention of LiNi_0.05Mn_1.95O₄ powders prepared by MTO cycled 30 times at room temperature and 55?°C are 98.3% and 90.6%, respectively, which are much higher than those of 86.63% and 77.7% for the one prepared by EMD. LiNi_0.05Mn_1.95O₄ powders prepared by MTO show higher specific capacity and better cycling performance than the one prepared by EMD.     

Compatibility study of oxide and olivine cathode materials with lithium aluminum titanium phosphate

The compatibility of the solid electrolyte Li_1.5Al_0.5Ti_1.5(PO₄)₃ (LATP) with the cathode materials LiCoO₂, LiMn₂O₄, LiCoPO₄, LiFePO₄, and LiMn_0.5Fe_0.5PO₄ was investigated in a co-sintering study. Mixtures of LATP and the different cathode materials were sintered at various temperatures and subsequently analyzed by thermal analysis, X-ray diffraction, and electron microscopy. Oxide cathode materials display a rapid decomposition reaction with the electrolyte material even at temperatures as low as 500 °C, while olivine cathode materials are much more stable. The oxide cathode materials tend to decompose to lithium-free compounds, leaving lithium to form Li₃PO₄ and other metal phosphates. In contrast, the olivine cathode materials decompose to mixed phosphates, which can, in part, still be electrochemically active. Among the olivine cathode materials, LiFePO₄ demonstrated the most promising results. No secondary phases were detected by X-ray diffraction after sintering a LATP/LiFePO₄ mixture at temperatures as high as 700 °C. Electron microscopy revealed a small secondary phase probably consisting of Li₂FeTi(PO₄)₃, which is ionically conductive and should be electrochemically active as well.     

Surface structure evolution of cathode materials for Li-ion batteries

Lithium ion batteries are important electrochemical energy storage devices for consumer electronics and the most promising candidates for electrical/hybrid vehicles. The surface chemistry influences the performance of the batteries significantly. In this short review, the evolution of the surface structure of the cathode materials at different states of the pristine, storage and electrochemical reactions are summarized. The main methods for the surface modification are also introduced.     

Electrical behaviour of LSGM–LSM composite cathode materials

Composite cathode materials were prepared by mixing La_0.83Sr_0.17Ga_0.83Mg_0.17O_2.83 (LSGM) and La_0.8Sr_0.2MnO₃ (LSM) powders fired at 1300 °C. Several compositions were set up containing 1, 5, 25, 50, 75 wt.% of LSM. Their microstructure and electrical behaviour were investigated by XRPD, SEM/EDS and EIS. In composites containing 50 and 75 wt.% of LSM, the electronic contribution to conductivity is predominant, then there is only a single point at the low frequency end of the Nyquist plot. On the contrary, in the composites with up to 25 wt.% of LSM, there is a significant amount of ionic transport, then the IS spectra show complex features: at least three different arcs can be devised and their interpretation depends upon temperature. LSGM bulk and grain boundary conductivity, as well as interface polarization between the ionic (LSGM) and electronic (LSM) phases can be separated at temperatures below 600 °C; total LSGM contribution, i.e. bulk plus grain boundary, LSGM–LSM interface and electrode polarizations are attributed above 600 °C.     

Investigation of thin film all-solid-state lithium ion battery materials

All-solid-state thin film batteries are feasible by employing Al as anode and LiPON as electrolyte which are subsequently deposited by sputtering. The lithium ion conductivity of ∼ 10⁻⁶ S/cm for the thin film LiPON is in agreement with data reported for bulk material. The high voltage cathode Li₂CoMn₃O₈ could be prepared by forming the compound by the combustion method andsubsequent e-beam evaporation of this material with the addition of 20 wt.-% LiNO₃ at an oxygen partial pressure of 10⁻⁵ mbar. The thin film cells could be operated between 3 and 5 V vs. Al, LiAl. The chemical diffusion coefficient was found to be in the range from 10⁻¹³ to 10⁻¹² cm²/s at room temperature by employing the GIT-technique for the composition x of Li_2-xCoMn₃O₈ in the range from 0.1 to 1.6. Impedance studies of the complete battery system revealed a charge transfer resistance of 290 Θ, a double layer capacity of ∼ 45–70 μF for an electrode area of 6.7 cm² and a rate determining chemical diffusion coefficient in the range from 10⁻¹² to 10⁻¹¹ cm²/s. Paper presented at the 9th EuroConference on Ionics, Ixia, Rhodes, Greece, Sept. 15–21, 2002.     

Sulfur composite cathode materials: comparative characterization of polyacrylonitrile precursor

The electrochemical behavior of the sulfur composite cathode material for rechargeable lithium batteries and the characteristic of the polyacrylonitrile precursor were investigated. The samples of different polyacrylonitrile precursors were characterized by thermogravimetric analysis, nuclear magnetic response, Fourier transform infrared spectrometer, and differential scanning calorimetry. The electrochemical performance of the sulfur composite cathode material made from the polyacrylonitrile precursor was also tested. The analysis showed that the molecular weight distribution and the impurity of the polyacrylonitrile precursor affected the electrochemical performance of the sulfur composite cathode material made from the precursor. The polyacrylonitrile precursor with the narrower distribution of the molecular weight and the higher structural purity of the polyacrylonitrile precursor led the better electrochemical performance of the sulfur composite cathode material made from the precursor.