Tuning of Composition and Morphology of LiFePO4 Cathode for Applications in All Solid-State Lithium Metal Batteries

All solid-state rechargeable lithium metal batteries (SS-LMBs) are gaining more and more importance because of their higher safety and higher energy densities in comparison to their liquid-based counterparts. In spite of this potential, their low discharge capacities and poor rate performances limit them to be used as state-of-the-art SS-LMBs. This arise due to the low intrinsic ionic and electronic transport pathways within the solid components in the cathode during the fast charge/discharge processes. Therefore, it is necessary to have a cathode with good electron conducting channels to increase the active material utilization without blocking the movement of lithium ions. Since SS-LMBs require a different morphology and composition of the cathode, we selected LiFePO4 (LFP) as a prototype and, we have systematically studied the influence of the cathode composition by varying the contents of active material LFP, conductive additives (super C65 conductive carbon black and conductive graphite), ion conducting components (PEO and LiTFSI) in order to elucidate the best ion as well as electron conduction morphology in the cathode. In addition, a comparative study on different cathode slurry preparation methods was made, wherein ball milling was found to reduce the particle size and increase the homogeneity of LFP which further aids fast Li ion transport throughout the electrode. The SEM analysis of the resulting calendered electrode shows the formation of non-porous and crack-free structures with the presence of conductive graphite throughout the electrode. As a result, the optimum LFP cathode composition with solid polymer nanocomposite electrolyte (SPNE) delivered higher initial discharge capacities of 114 mAh g-1 at 0.2C rate at 30 ᴼC and 141 mAh g-1 at 1C rate at 70 ᴼC. When the current rate was increased to 2C, the electrode still delivered high discharge capacity of 82 mAh g-1 even after 500 cycle, which indicates that the optimum cathode formulation is one of the important parameters in building high rate and long cycle performing SS-LMBs.

Synthesis of porous γ-Fe2O3 from scorodite synthesized using ultrasound irradiation and evaluation of its battery performance

The effect of 200 kHz ultrasound on scorodite synthesis at 70 °C and 3 h reaction conditions was investigated using sulfuric acidic solutions of various pH (3.0, 2.0, 1.5, 1.0, and 0.0). In contrast to the case of only O2 gas flow without ultrasound irradiation, oxidizing radicals generated by ultrasound irradiation promote Fe(II) oxidation in solution and precursor, allowing scorodite to synthesize with high crystallinity (>99%), which relates to low solubility, even in strong acid solution at pH 1.0. During synthesis, particle shape was changed to polyhedral or spindle type depending on the pH of 0.0 to 3.0. The spindle-shaped scorodite was probably formed by the decrease of precursor amount produced in initial stage of the synthesis. Furthermore, porous maghemite obtained by alkali treatment of scorodite showed initial discharge capacities of 146 mAh/g (polyhedron) and 167 mAh/g (spindle), indicating that its potential use as a cathode material for lithium-ion batteries.

Effect of Carbon Source on Synthesis of Carbon Coated Lithium Titanate

Carbon coated lithium titanate (Li4Ti5O12/C) was obtained by a facile solid state approach in inert Ar atmosphere. The composition, morphology, residual carbon content and Ti valence of the samples were systematically investigated. The carbon content of Li4Ti5O12/C should be optimized, since excess carbon in the composite leads to the reduction of Ti (IV) to form Ti (III), which results in large irreversible capacity of Li4Ti5O12/C. With an optimal carbon content of 0.68wt%, the Li4Ti5O12/C sample shows high rate capabilities and good cycling ability, delivering discharge capacities of 160.8 mAh/g at 5C. The superior high rate properties are ascribed to the specific nanostructures, which enables fast electronic and ionic transport by introducing carbon coating and decreasing the particle size of lithium titanate.

Synthesis and Performance Elucidation of Ternary O3-Na0.8Fe0.4Mn0.3Co0.2O2 Layered Positive Electrode for Sodium Ion Batteries

We report here a combination of transition metal-based ternary sodium magnate layered cathodes with the compositions of Na0.8Fe0.4Mn0.3Co0.2O2, Na0.8Fe0.4Mn0.3Ni0.2O2, Na0.8Fe0.4Mn0.3V0.2O2, Na0.8Fe0.4Mn0.3Ti0.2O2, in order to elucidate the precise metal contents for the superb performing positive electrode. Based on their stoichiometry, the transition metal combination of Na0.8Fe0.4Mn0.3Co0.2O2, O3-type crystal structure with R3m space group possess superior electrochemical behavior under the test of sodium-ion battery. When the charge-discharge capacities in the range of 2.0-4.2 V at 0.1 C are measured, it shows the comparatively higher performance of the first and second charge capacities of 162 mAhg-1, 170 mAhg-1 and discharge capacities of 157 mAhg-1, 154 mAhg-1, respectively. Moreover, it was remarkable to observe that the increasing/decreasing Co constituent substantially affects the performance and stability, but using the ternary combination in cathodes, a substantial reduction of Jahn-Teller distortion and increased biphasic characteristics were observed. The as-synthesized samples were characterized by FE-SEM, XRD, charge-discharge curve, EIS and cyclic voltammograms.

Synthesis of O3-Na0.8Fe0.6Mn0.3O2 Positive Electrode and Its Application to Sodium Ion Batteries

Herein, we report precise variation of Fe and Mn constituent in the sodium magnate layered cathodes with the compositions of Na0.8Fe0.4Mn0.5O2, Na0.8Fe0.5Mn0.4O2, Na0.8Fe0.6Mn0.3O2, Na0.8Fe0.6Mn0.4O2, Na0.8Fe0.7Mn0.4O2, Na0.9Fe0.6Mn0.3O2 in order to attain a high performing cathode. Based on this transition metal stoichiometry, an interesting sodium magnate combination of Na0.8Fe0.6Mn0.3O2, with O3-type crystal phase, possess R3m space group along with the superior electrochemical behavior is obtained. On charge-discharge capacities in the range of 2.0-3.8 V at 0.1 C, it shows the comparatively higher performance of the first and the second charge capacity of 115 and 180 mAhg-1 and discharge capacity of 184 and 181 mAhg-1, respectively. The best sample was then compared with the closely related Na0.8Fe0.6Mn0.4O2, Na0.9Fe0.6Mn0.3O2 combination in terms of valence ratio and influence of excess sodium for the structure robustness, stability along with purity. The best sample with the composition Na0.8Fe0.6Mn0.3O2 does not show detectable impure phase while Na0.8Fe0.6Mn0.4O2 and Na0.9Fe0.6Mn0.3O2 shows a tendency of P-type (Cmca space group) behavior with 30.8% and 32.8%, respectively. The enhancement of iron constituent increases not only the performances but also the stabilization of sodium vacancy ordering and substitution of Mn with a substantial reduction of Jahn-Teller distortion, mounting biphasic characteristics and high peak intensity of 41.5 °.

Half and full cell researches of ternary MoS2/graphene/CNT aerogel compostie for enhanced lithium storage performances

Without using any templates, a ternary MoS2/graphene/carbon nanotubes (MoS2/GN/CNT) aerogel compostie is prepared by convenient hydrothermal synthesis method. The free-standing MoS2/GN/CNT aerogel can be cut directly as binder free electrodes in lithium-ion batteries. The MoS2/GN/CNT electrodes can hold as high as 695 and 579 mAh g−1 discharge capacities after 200 cycles at 200 mA g−1 in MoS2/GN/CNT//Li half cells and MoS2/GN/CNT//LiCoO2 full-cells, respectively. The strengthened electrochemical properities are owed by the thin GN/CNT layers and their jagged and wrinkled surfaces, which can enhance the composite conductivity and shorten the Li+ diffusion distance, as well as buffer the volume change of electrodes druing the charge-discharge cycles.

Preparation of carbon anode sheet precursor using raw Air Laya–Bukit Asam coal and its application for battery

Research has been carried out on manufacturing carbon electrode thin sheets used as anode for solid battery cells. The material used is raw coal carbonized at 800 and 1000oC, polyvinylidene fluoride (PVDF), and N-Dimethylacetamide (DMAC) as a solvent. Observation of crystal structure by X-rays diffraction method shows a diffraction pattern where crystallites in all product samples have an intermediate structure between graphite and amorphous known as a turbostratic structure or a random layer lattice structure. The distance between the crystallite structure’s aromatic layers (d002) is in the range 3.52-3.62 Å. Aromaticity (fa) is in the range 0.42 - 0.48 for all samples. The high value of d002 indicated that the crystallinity or level of graphitization obtained by all samples was still low. Manufacturing technique using a Doctor Blade-based tape casting method. The discharge capacities of the samples reach about 60 and 18 mAh.g-1, while their charge capacities at the first cycle are 50 and 16 mAh.g1, respectively. Cyclic voltammetry (CV) was performed using anodes resulted at 0.1 to 2.3 volt. During the forward scan, CV curves of the sample reveal a reduction current starting from around 1.2 V and exhibiting two-reduction waves, between 1.2 and 0.6 V.

Vertically Aligned Binder-Free TiO2 Nanotube Arrays Doped with Fe, S and Fe-S for Li-ion Batteries

Vertically aligned Fe, S, and Fe-S doped anatase TiO2 nanotube arrays are prepared by an electrochemical anodization process using an organic electrolyte in which lactic acid is added as an additive. In the electrolyte, highly ordered TiO2 nanotube layers with greater thickness of 12 μm, inner diameter of approx. 90 nm and outer diameter of approx. 170 nm are successfully obtained. Doping of Fe, S, and Fe-S via simple wet impregnation method substituted Ti and O sites with Fe and S, which leads to enhance the rate performance at high discharge C-rates. Discharge capacities of TiO2 tubes increased from 0.13 mAh cm−2(bare) to 0.28 mAh cm−2 for Fe-S doped TiO2 at 0.5 C after 100 cycles with exceptional capacity retention of 85 % after 100 cycles. Owing to the enhancement of thermodynamic and kinetic properties by doping of Fe-S, Li-diffusion increased resulting in remarkable discharge capacities of 0.27 mAh cm−2 and 0.16 mAh cm−2 at 10 C, and 30 C, respectively.

Multi-material integrated 3D printing of cylindrical Li-ion battery

A simple, low cost and highly efficient method of fabrication has always been the goal of manufacturing technology. In order to improve the speed of fabrication and simplify the preparation steps, this work proposes a multi-material integrated 3D printing method, aiming to obtain the desired structure from the print head in one step. As a typical example, a cylindrical Li-ion battery (LIB) with core-shell structure was integrally fabricated using this method. A multi-material print head is designed based on the structure to be printed. Special inks with the characteristics of non-Newtonian fluid for the LIB were developed. Anode, cathode, separator layer, and packaging layer were easily printed simultaneously, and the printing parameters were studied. Electrochemical performance of the printed battery was tested with the charge and discharge capacities of the printed battery up to 147 and 99 mAh g−1 at 0.1 C rate, respectively. The proposed multi-material integrated printing method greatly reduces the printing process and improves the fabrication efficiency. This system can be directly extended to fabricate other integrated devices such as supercapacitors. Based on this idea, it should also be possible to design different print heads to print other periodic structure in one step.