A novel method for preparation of macroposous lithium nickel manganese oxygen as cathode material for lithium ion batteries

Dynamic Covalent Synthesis of Crystalline Porous Graphitic Frameworks

Recently, Prussian blue analogues (PBAs) have been reported to exhibit a low voltage charge/discharge behavior with high capacity (300–545 mAh/g) in lithium-ion secondary batteries (LIBs) [...]

Olivine LiFePO4/C cathode materials for lithium ion batteries were synthesized using monodisperse polystyrene (PS) nano-spheres and other carbon sources. The structure, morphology, and electrochemical performance of LiFePO4/C were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), galvanostatic charge–discharge tests, electrochemical impedance spectroscopy (EIS) measurements, and Raman spectroscopy measurements. The results demonstrated that LiFePO4/C materials have an ordered olivine-type structure with small particle sizes. Electrochemical analyses showed that the LiFePO4/C cathode material synthesized from 7 wt.% PS nano-spheres delivers an initial discharge capacity of 167 mAh g-1 (very close to the theoretical capacity of 170 mAh g-1) at 0.1 C rate cycled between 2.5 and 4.1 V with excellent capacity retention after 50 cycles. According to Raman spectroscopy and EIS analysis, this composite had a lower I D/I G, sp 3/sp 2 peak ratio, charge transfer resistance, and a higher exchange current density, indicating an improved electrochemical performance, due to the increased proportion of graphite-like carbon formed during pyrolysis of PS nano-spheres, containing functionalized aromatic groups.

In this study, LiFePO4-carbon (LFP-C) and LFP-C/reduced graphene oxide (rGO) nanocomposites were prepared by ultrasonic spray pyrolysis technique in different calcination conditions to be used as the cathode-active materials for lithium ion battery (LIB). The structure, morphology and composition of the obtained materials were analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM), high-resolution transmission electron microscopy (HR-TEM) and energy-dispersive X-ray spectroscopy (EDX). The XRD results reveal that the olivine pure phase was obtained after calcination of the LFP-C. The SEM images of the prepared materials exhibit the spherical morphology with nanometer size and also change in the morphology by applying the calcination step. The electrochemical performances of cathode-active materials were investigated by charge–discharge test, electrochemical impedance spectroscopy and cyclic voltammetry. The obtained results for LFP-C show that the electrochemical performance was improved by adding carbon precursor and calcining step; in the optimum calcination conditions; 700 °C for 3 h, the LFP-C shows good results in terms of electrochemical performance in comparison with LFP alone. The LFP-C/rGO nanocomposite exhibits the best electrochemical performance however: highest rechargeable capacity and cycle stability; discharge capacity (168 mAh/g at 0.1 C and 123.5 mAh/g at 10 C) and capacity retention of 100% after 50 cycles with maximum reversibility and lithium ion (Li+) diffusion coefficient. Schematic representation of preparation of the cathode-active materials.

Natural graphite (NG) has been attracted as a promising anode material for lithium ion batteries due to its appropriate charge/discharge profile, high reversible capacity and low cost. However, high irreversible capacity and low capacity retention at first cycle have influenced on its practical use. Although low cost is the main advantage of natural graphite, the material cost of natural graphite should be reduced further in order to be used for electric vehicles (EVs) and energy saving systems (ESS). Generally, pristine natural graphite contains various impurities such as Al, Fe, and Si. For commercial use, pristine natural graphite should be refined since the impurities would have a negative effect on both electrolyte and electrode of lithium ion batteries. The purity grade of natural graphite can be classified based on the purification process. As the requirement for high purity increases, more purification steps are needed, resulting in high manufacturing cost. Therefore, the main issue for the application of natural graphite as an anode active material is to use low-purity natural graphite with purification process as less as possible. In this regard, effect of Fe as impurity on the electrochemical performance of the low-purity natural graphite as anode active material for lithium ion batteries was investigated in this study. Natural graphite powders with 5 wt% Fe (05Fe) and 10 wt% (10Fe) were synthesized by combustion method from the raw materials of Fe(III)(NO3)3 9H2O (Alfa Aesar) and high-purity spherical natural graphite (POSCO CHEMTECH) by calcination at 500 °C in air atmosphere. The morphology of the natural graphite powders was observed by scanning electron microscopy (SEM, JSM-5900, JEOL, Japan). The particle size of each powder was measured by a dynamic light scattering method (ELS 6000 zeta potential and particle size analyzer, Otsuka Electronics, Japan). Powder X-ray diffraction (XRD, MAX-2500, RIGAKU, Japan) analysis was conducted using Cu Kα radiation with a wavelength λ = 1.5406 Å. The crystallite sizes (La and Lc) were calculated on the basis of the d002XRD lines by application of the Scherrer’s equation. The crystallinity of the natural graphite powders was investigated by Raman spectroscopy (LabRAM, Horiba Jobin-Yvon, Japan). The concentrations of impurities in the natural graphite were determined by an inductively coupled plasma atomic emission spectrophotometer (ICP-AES). A working electrode paste was fabricated from a mixture of natural graphite with a binder consisting of carboxymethylcellulose (CMC)/styrene-butadiene rubber (SBR) and carbon black (Super-p) as a conductive agent dissolved in D.I. water. The weight ratio of graphite to binder (CMC:SBR:Super-p=2:2:1) was 95:2:2:1. The prepared paste was coated onto 10㎛ Cu foil by using a doctor blade and then dried under vacuum at 120 °C for 12 h. Electrochemical performance was evaluated using CR2032 coin-type cells with a 20 μm thick Cellgard 2300 porous membrane separator and 1 M LiPF6-EC/DMC (1:1 in volume ratio) electrolyte. Lithium metal foil was used as a counter electrode. All of the samples studied in this work were treated by sphericalization and the sphericalized natural graphite maintained a spherical shape after the calcination process at 500 °C for 4 h. All the samples have both hexagonal and rhombohedral phases which are the typical structure of natural graphite. Fe2O3 peaks (JCPDS card #33-0664) were indexed at 2θ = 33.1°, 35.6°, 62.4°, and 63.9°, respectively. The most of Fe2O3particles were located on a surface of natural graphite, based on the EDX mapping and back-scattered electron (BSE) images. The irreversible capacity during the charge-discharge reactions increased with increasing the Fe content. However, the cycle retention of the 05Fe, 10Fe, and NG are comparable. Therefore, it may be possible to use unrefined natural graphite as an anode active material for lithium-ion rechargeable batteries.

Sr1−xNa2xLi2Ti6O14 (0≤x≤1) as anode materials for rechargeable Li-ion batteries

Synthesis and electrochemical performance of cubic Co-doped Li4Ti5O12 anode material for high-performance lithium-ion batteries

The layered Li-rich Mn-based cathode materials Li[Li0.2Mn0.54Ni0.13Co0.13]O2 were prepared by using co-precipitation technique at different temperatures, and their crystal microstructure and particle morphology were observed and analyzed by XRD and SEM. The electrochemical properties of these samples were investigated by using charge-discharge tests, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV), respectively. The results indicated that all samples are of high purity. When the precursors were co-precipitated at 50 °C, their cathode materials have the most uniform and full particles and exhibit the highest initial discharge capacity (289.4 mAh/g at 0.1C), the best cycle stability (capacity retention rate of 91.2 % after 100 cycles at 0.5C), and the best rate performance. The EIS results show that the lower charge transfer resistance of 50 °C sample is responsible for its superior discharge capacity and rate performance.

Effect of Mn-doping on performance of Li 3V 2(PO 4) 3/C cathode material for lithium ion batteries

In this study, a high entropy composite coating was synthesized by oxidizing a high entropy alloy, AlCrFeCoNi, at elevated temperatures in a pure oxygen atmosphere. X-Ray diffraction (XRD) analysis revealed that the prepared material was a dual-phase composite material consisting of a spinel-structured high entropy oxide and a metallic phase with a face-centered cubic structure. The metallic phase can improve the electrical conductivity of the oxide phase, resulting in improved electrochemical performance. Scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS) analysis unveiled the compositional homogeneity of the composite material. The prepared material was utilized as an anode active material in lithium-ion batteries. Cyclic voltammetry (CV) revealed the oxidation and reduction regions, while the electrochemical impedance spectroscopy (EIS) measurements showed a decrease in the charge transfer resistance during the cycling process. A long-term rate capability test was conducted at various current densities: 100, 200, 500, 1000, and 2000 mA g−1. During this test, a notable phenomenon was observed in the regeneration process, where the capacity approached the initial discharge capacity. Remarkably, a high regeneration efficiency of 98% was achieved compared with the initial discharge capacity. This phenomenon is typically observed in composite nanomaterials. At a medium current density of 500 mA g−1, an incredible discharge capacity of 543 mAh g−1 was obtained after 1000 cycles. Based on the results, the prepared material shows great potential for use as an anode active material in lithium-ion batteries.

Lithium-ion battery is considered to be one of the most promising energy storage systems that are able to satisfy the requirements of power battery, but the current energy density, power density and safety performance for lithium-ion batteries can't meet the needs of the development of electric vehicles. As the only lithium ions supplier, the cathode materials for lithium-ion batteries greatly limit the performance of lithium-ion battery.Therefore, the development of cathode materials with a higher energy density, higher power density and better safety performance is highly desired. Owing to high theoretical capacity, low cost, and low toxicity, ternary layered transition metal oxide cathode materials are considered to be the most promising cathode materials for the next-generation lithium-ion batteries. And in order to fully release the capacities of ternary layered transition metal oxide cathode materials high voltage is necessary, but the cycle stability is not good enough when ternary layered transition metal oxide cathode materials are set with a high voltage range. What’s more, the poor storage performance is another factor that restricts the wide application in electric vehicles. This review describes several common cathode materials, highlighting the advantages and disadvantages of ternary layered transition metal oxide cathode materials and modification progress.

The effect of drying methods on the structure and performance of LiNi0.5Co0.2Mn0.3O2 cathode material for lithium-ion batteries

Superior electrochemical capability of Li2FeSiO4/C/G composite as cathode material for Li-ion batteries

Synthesis and characterization of concentration–gradient LiNi0.6Co0.2Mn0.2O2 cathode material for lithium ion batteries

The demand of rechargeable batteries had increased significantly every year during the last decade, driven for the needs associated with technological development (portability, high performance of electronic devices and vehicles). Lithium ion battery is a device of mayor consumption, and it is designed for energy storage and conversion based on intercalation electrodes. Nowadays the efforts are directed to the improvement and replacement of current battery components: anode, cathode (LiCoO2) electrolyte, with materials that have higher efficiency in terms of energy, power, cost, reliability, life time and safety. In recent years there has been significant interest in polyanion-based active materials as safe alternatives for the traditional oxide cathodes. For example, phosphate phases such as LiFePO4 [1], Li3V2(PO4)3, [2], Li2.5V2(PO4)3, [3], LiVOPO4, [4,5] and LiVP2O7[6] have all been proposed. Therefore, the search of new cathode materials is an important task for researchers in materials science. The possibility of using sodium directly in lithium ion cells allows the study of new compositions and structures. In this research work a series of four compounds with formula Na3V2-xAlx(PO4)2F3 (x= 0, 0.02, 0.05, 0.1) were prepared, characterized and applied as cathode materials in lithium ion batteries. These materials were synthesized by sol-gel Pechini method. Aqueous solutions containing appropriate amounts of NH4VO3, NH4H2PO4 and NaF were poured into a mixture of citric acid and ethylene glycol solution. Mixture was then heat treated under reflux at 80°C until gel formation. Fresh samples were heated at 300°C under air to eliminate volatile matter. Resulting powders were grinded and formed into pellets for reaction between 300 to 650°C under nitrogen atmosphere. Thermal stability of materials was evaluated by simultaneous termogravimetric and differential analysis (TGA-DTA). Morphological and microstructural characterization were carried out with field emission scanning electron microscopy (FESEM), textural analysis by N2 physisorption with BET method; chemical composition and crystallographic parameters were determined with Induced coupled plasma – optic emission spectroscopy (ICP-OES), energy dispersive X-ray spectroscopy (EDXS) and X-ray powder diffraction (XRD); the application of materials as cathodes in lithium ion batteries was evaluated through electrochemical charge discharge experiments. Electrodes were prepared using a mixture of each synthesized materials, conductive carbon and PVDF binder. CR2032 coin cells were assembled inside a glove box under Ar atmosphere, using LiPF6electrolyte and Li° as anode. Experiments were performed using a MacPile II by Biologic. Thermal analysis of sol-gel reaction products exhibited an exothermic even between 550 and 750°C attributed to the crystallization of the fluorophosphates. Results from XRD analysis showed that Al doped Na3V2(PO4)2F3 crystalline phase was formed at 650°C for 8h. According to cell parameters Na3V2(PO4)2F3 can incorporate aluminum content up to x=0.1, without the presence of secondary phases or structural transitions. Granular morphology and small particles size of about 40 to 100 nm were observed, this can be attributed to the effect of residual carbon within samples (8% by weight) since this inhibits particle grown and also allows contact among particles, improving electrical conductivity. Materials present average porous size of about 20nm, with surface area of 30m2/g. The sample with x=0.05 of Aluminum content, presents the best textural properties. This material also presents high specific charge/discharge capacity (123/101 mAh/g at a 4.4 V vs Li cell) and good capacity retention (82%), in comparison to the material without doping (128/63 mAh/g and 49% of capacity retention). Aluminum doping of Na3V2(PO4)2F3phase permitted the stabilization of the structure related to cycling processes. These results are promising for future application of the material in lithium and sodium ion batteries. Keywords: Pechini, cathodes, phosphates, lithium ion batteries References [1] A.K. Padhi, K.S. Nanjundaswamy, C. Masquelier, J.B. Goodenough, J. Electrochem. Soc. 144 (1997) 2581. [2] M.Y. Saidi, J. Barker, H. Huang, J.L. Swoyer, G. Adamson, Electrochem. Solid-State Lett. 5 (2002) A149. [3] C. Yin, H. Grondey, P. Strobel, L.F. Nazar, Chem. Mater. 16 (2004) 1456. [4] B.M. Azmi, T. Ishihara, H. Nishiguchi, Yusaku Takita, J. Power Sources 146 (1–2) (2005). [5] J. Gaubicher, T. Le Mercier, Y. Chabre, J. Angenault, M. Quarton, J. Electrochem. Soc. 146 (1999) 4375. [6] J. Barker, R.K.B. Gover, P. Burns, A. Bryan, Electrochem. Solid-State Lett. 8 (9) (2005) 446.