Charge Capacity Values Research Articles

Nanoarchitectonics of Mesoporous M2P2O7 (M = Mn(II), Co(II), and Ni(II)) and M2-xCoxP2O7 and Transformation to Their Metal Hydroxides with Decent Charge Capacity in Alkali Media.

A general synthetic method has been developed to synthesize spherical mesoporous metal pyrophosphate (m-M2P2O7) particles and to fabricate graphite rod-coated (GR-M2P2O7) electrodes, which are important as energy storage materials. The clear aqueous solution of the ingredients (namely, [M(H2O)6](NO3)2, H4P2O7, water, and P123) assembles, upon excess water evaporation, into a mesostructured M2HxP2O7(NO3)x·nH2O-P123 semisolid that is calcined to produce the spherical m-M2P2O7 (where M is Ni, Co, Mn, Ni/Co, or Mn/Co) particles, coated over GR, and calcined to fabricate the GR-M2P2O7 electrodes. The mesostructured and mesoporous materials are characterized using diffraction (XRD), spectroscopy (ATR-FTIR, XPS, and EDX), N2 adsorption-desorption, and imaging (SEM and TEM) techniques. The electrochemical/chemical investigations showed that the GR-M2P2O7 electrodes transform to β-M(OH)2 in alkali media. The spherical m-Ni2P2O7 particles transform into spherical ultrathin nanoflakes of β-Ni(OH)2. However, the m-Mn2P2O7 and m-Co2P2O7 particles transform to much thicker β-Mn(OH)2 and β-Co(OH)2 plate-like nanoparticles, respectively. The size and morphology of the β-M(OH)2 particle depend on the Ksp of the M2P2O7 and determine the charge capacity (CC) and specific capacitance (SC) of the electrodes. The β-Ni(OH)2 and β-Ni0.67Co0.33(OH)2 electrodes display high CC (129 and 170 mC/cm2, respectively) and SC (234.5 and 309 mF/cm2, respectively) values. However, these values are almost 10× smaller in β-Mn(OH)2, β-Co(OH)2, β-Mn1-xCox(OH)2, and cobalt-rich β-Ni1-xCox(OH)2 electrodes.

Exploring the intercalation chemistry and Li ion dynamics in Li4WO5: An anode material for Li-ion batteries

Electrochemical properties, Li ion dynamics and intercalation chemistry in Li4WO5 bulk material is explored in this work. X-ray diffraction and Raman spectra studies confirm the formation of Li4WO5 in orthorhombic structure. Electrochemical charge discharge studies at 0.1 C rate reveal that the discharge and charge capacity values at 2nd cycle is 364 mAh/g 286 mAh/g respectively. After 100 cycles the discharge and charge capacity values are seen to increase to 575 mAh/g and 549 mAh/g respectively with 99% Columbic efficiency. Intercalation chemistry and retention of orthorhombic structure during the electrochemical cycling with small changes in the lattice parameters in Li4WO5 is confirmed from the ex-situ XRD and Raman studies. In-situ XRD measurement during the first cycle confirms the stable structure of Li4WO5 with a small distortion in (531) plane due to the removal and insertion of Li. Irreversible redox peak and the unknown phases from the solid electrolyte interface appeared at 0.7 V during the first discharge process are probed from the addition diffraction peaks appeared in the in-situ XRD pattern. The Li ion diffusion coefficient value is calculated to be 2.96 × 10−14 cm2/s. Electrochemical impedance spectroscopy (EIS) studies showed the reduction in charge transfer resistance with increasing cycle number. Observed intercalation chemistry, high-rate performance and virtuous specific capacity in Li4WO5 indicates that it can be applied as an anode material for high performance LIB’s.

Probing Capacity Trends in MLi2Ti6O14 Lithium-Ion Battery Anodes Using Calorimetric Studies.

Due to higher packing density, lower working potential, and area specific impedance, the MLi2Ti6O14 (M = 2Na, Sr, Ba, and Pb) titanate family is a potential alternative to zero-strain Li4Ti5O12 anodes used commercially in Li-ion batteries. However, the exact lithiation mechanism in these compounds remains unclear. Despite its structural similarity, MLi2Ti6O14 behaves differently depending on charge and size of the metal ion, hosting 1.3, 2.7, 2.9, and 4.4 Li per formula unit, giving charge capacity values from 60 to 160 mAh/g in contrast to the theoretical capacity trend. However, high-temperature oxide melt solution calorimetry measurements confirm strong correlation between thermodynamic stability and the observed capacity. The main factors controlling energetics are strong acid-base interactions between basic oxides MO, Li2O and acidic TiO2, size of the cation, and compressive strain. Accordingly, the energetic stability diminishes in the order Na2Li2Ti6O14 > BaLi2Ti6O14 > SrLi2Ti6O14 > PbLi2Ti6O14. This sequence is similar to that in many other oxide systems. This work exhibits that thermodynamic systematics can serve as guidelines for the choice of composition for building better batteries.

LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O 2 with morphology optimized for novel concept of 3D Li accumulator

An array of LiNi1/3Mn1/3Co1/3O2 (NMC 111) samples with a hollow-sphere morphology enabling the use of binder-free, millimeter-thick electrodes in a battery are prepared by a combination of ball milling, hydrothermal treatment and calcination. Materials are studied by powder X-ray diffraction, nitrogen adsorption measurements, X-ray fluorescence analysis, and scanning electron microscopy. Their electrochemical performance for Li+ extraction/insertion is tested by cyclic voltammetry and galvanostatic chronopotentiometry on thin-film electrodes. Optimized materials, prepared by mechanical and thermal treatment with surface areas of 7 to 10 m2 g−1, provide charge capacity values of 141 to 156 mAh g−1. The concentration of the crystalline phase in NMC 111 materials with a hollow-sphere morphology is found to be the decisive parameter for their galvanostatic cycling stability. Hollow spheres with well-developed NMC nanocrystals and a low concentration of amorphous phase in the walls, exhibiting excellent cycling stability and charge capacity in thin-film electrodes are incorporated into a NMC/graphite 3D-battery module. This 122 Ah/451 Wh 3D-battery provides 78% of theoretical capacity and 73% of theoretical energy after 10 formatting cycles. Additionally, the battery prototype exhibits stable performance over more than 200 cycles at C/10 rate. A series of analogous 3D Li accumulators, currently assembled and tested in a pilot plant, represent the first step toward large-scale production of novel 3D Li accumulator.

Synthesis of graphene-siloxene nanosheet based layered composite materials by tuning its interface chemistry: An efficient anode with overwhelming electrochemical performances for lithium-ion batteries

Owing to its high theoretical storage capacity, two dimensional (2D) silicon nanosheets is the one among the most exciting anode material for the next generation lithium ion (Li-ion) batteries. However, deprived electrochemical properties due to the huge volume expansion resulting in rapid capacity decay, thereby hindering its commercial application aspect of silicon nanosheet based materials. The present work proposes a novel concept of synthesizing graphene-siloxene (SiG) based multi-layered structures by tuning the interface chemistries of graphene oxide and siloxene sheets derived from topochemical transformation of calcium silicide (CaSi2). Morphological characterization using Field emission scanning electron microscopic and transmission electron microscopy reveal the successful formation of few- to multi-layered SiG composite materials with intercalated/surface grafted siloxene nanosheets on the graphene layers. Owing to its hierarchical composite structure, SiG as anode delivers the first discharge and charge capacity values as high as 3880 mAhg−1 and 3016 mAhg−1 respectively measured at the current rate of 205 mAg−1. Even at high current rate (4.1 Ag-1), SiG composite materials delivers first charge capacity of 1480 mAhg−1 with good cycling performance (1040 mAhg−1) after 1000 cycles. Due to its enhanced lithium storage, cycling stability and rate capability, synthesized SiG composites could be a potential anode candidate for Li-ion batteries.

Iron and Titanium-Based Electrode Materials for Sodium-Ion Batteries

In the past two decades, lithium-ion batteries (LIBs) have been successfully used in mobile electronic devices. With the development of hybrid electrical vehicles (HEVs), electrical vehicles (EVs), and energy storage stations, etc., of which a battery needs at least manifold amount of lithium, the cost of lithium would be further driven higher as the lithium metal reserves are limited both in amount and geographical location. Recently, sodium-ion batteries (NIBs) have been proven to be the most attracted alternative rechargeable systems for the potential large-scale production because sodium is much cheaper and more abundant in the Earth’s crust, and the potential of sodium metal is only 0.3 V higher than that of lithium. Therefore, it is urgent for us to develop NIBs to provide sufficient low-cost and safe energy storage devices for our society. Recent studies in NIBs focused on the development of electrode materials. A number of promising electrode materials, including cathodes such as α-NaFeO2-based NaMO2 (M = Fe, Co, Mn, Ni, Ti, etc.) [1, 2], polyanion-based Na3V2(PO4)3 [3], Na3MPO4CO3 [4], Na4Fe3(PO4)2(P2O7) [5], and Prussian blue [6], and anodes such as hard carbon [7], Na2Ti3O7 [8], P2-type Na2/3Co1/3Ti2/3O2 [9], and carboxylate-based materials [10] have already been explored for NIBs. The development of feasible electrode materials by an optimized composition with high capacity, long cycle life, and low cost still remains a challenging issue that warrants further investigation. Looking back to the history, iron (Fe) always has the priority being used when it comes to transition metal oxides because the elemental abundance in the Earth’s crust is of primary importance for large-scale batteries [1, 11]. In this pursuit, herein, O3-type Na[Fe1/3Ni1/3Ti1/3]O2 cathode material and orthorhombic Nax[FeTi]O4 (x = 1 and 4/3) anode materials are synthesized by a solid-state reaction method, and studied as a positive electrode and negative electrodes for NIBs, all tested in a half cell and at 20 ºC, using 1 M NaClO4 in 1:1 weight ratio of propylene carbonate (PC) and dimethyl carbonate (DEC) as electrolyte, and a glass fiber filter (GF/D, Whatman) as separator. The obtained Na[Fe1/3Ni1/3Ti1/3]O2 cathode material has an initial discharge capacity of 115 mAh g-1 under a current density of 10 mA g-1 (0.1 C) in the voltage range of 1.5-4.0 V, and shows reversible discharge capacity values of 91.3, 89.7, 79.2, 69.7, 46.2, and 30.9 mAh g-1, respectively at 0.2, 0.5, 1, 2, 5, and 10 C. The potentials reported in this work refer to the Na+/Na couple. The obtained Na4/3[FeTi]O4 anode material exhibits a first charge capacity of 119.6 mAh g-1 under a current density of 17.7 mA g-1 (0.1 C) in the voltage range of 0.01-2.5 V, and delivers reversible charge capacity values of 84.5, 73.1, 61.4, 47.5, and 36.7 mAh g-1, respectively at 0.5, 1, 2, 5, and 10 C. The even more promising thing is as-prepared orthorhombic Na[FeTi]O4 exhibits an initial charge capacity of about 181 mAh g-1 at 0.1 C, and good cycling performance as well.

Influence of cationic substitutions on the first charge and reversible capacities of lithium-rich layered oxide cathodes

The reversible capacity values of lithium-rich layered oxide cathodes depend on the length (capacity) of the plateau region during the first charge. With an aim to understand the factors that control the length of the plateau region and thereby enhance the reversible capacity, the effects of various cationic substitutions in Li1.2Mn0.6Ni0.2O2 have been investigated systematically. Specifically, substitutions of (i) M3+ = Al3+, Cr3+, Fe3+, Co3+, and Ga3+ for equal amounts of Mn4+ and Ni2+ in Li1.2Mn0.6−0.5xNi0.2−0.5xMxO2 with x = 0.06, 0.13, and 0.2, (ii) Ti4+ for Mn4+ in Li1.2Mn0.6−xTixNi0.2O2 with x = 0.025, 0.05, and 0.1, and (iii) Mg2+ for Ni2+ in Li1.2Mn0.6Ni0.2−xMgxO2 with x = 0.025, 0.05, and 0.1 have been investigated. The cationic substitutions affect the first charge capacity values both in the sloping region corresponding to the oxidation of the transition-metal ions to the 4+ state and in the plateau region corresponding to the oxidation of O2− ions to O2 and/or transition-metal ions beyond 4+, which control the reversible capacity values in subsequent cycles. While the changes in the sloping-region capacity could be readily understood by considering the redox activities of the transition-metal ions, the plateau-region capacity is found to depend sensitively on the metal–oxygen covalence, which is dictated by the relative positions of the metal:3d band with respect to the top of the O2−:2p band, and electron delocalization. For instance, an overlap of the Co3+/4+:t2g band with the top of the O2−:2p band along with a partially filled t2g band across the shared octahedral edges makes the oxygen loss from the lattice and/or oxidation beyond 4+ much more facile.

Electrodeposition and properties of TEMPO functionalized polythiophene thin films

The modification of an azide-functionalized regioregular polythiophene with TEMPO groups is reported. The TEMPO functionalized polymer is characterized by ESR, ATR-IR, absorption and emission spectroscopies and electrochemical methods. Partial quenching of the polymer emission by the TEMPO groups is observed. The polymer may be electrodeposited onto ITO or carbon electrodes to give thin films. Cyclic voltammetry gives specific charge capacity values of 2.3 mA h g−1 for the TEMPO functionalized polymers, and specific capacitances of 0.8 F g−1 determined by galvanostatic charge/discharge experiments. The reduced charge capacity relative to unfunctionalized polythiophene is attributed to TEMPO induced cleavage and oxidation of the conjugated backbone.

A new SiO/C anode composition for lithium-ion battery

A new anode composition comprising SiO and graphite(C) is prepared through a high-energy ball milling process. During the first cycle, the anode delivers high discharge and charge capacity values of 1556 and 693 mAh g −1, respectively. The electrode shows a reversible charge capacity value of 688 mAh g −1 at the 30th cycle with 99% Coulombic efficiency. X-ray diffraction analysis reveals that ball milling does not produce any new compound, but only causes a reduction in particle size. The irreversible and reversible capacities appear to be interdependent.

Improved anode performance of thermally treated SiO/C composite with an organic solution mixture

A pristine composite anode material comprising of silicon monoxide and graphite was prepared through ball milling process and made in the form of a slurry using a simple solution mixture consisting of propylene carbonate (PC) and acetone (AC) and then heat treated. Cycle life study of the pristine composite and heat treated organic slurry composite showed the charge capacity values as 318 and 500 mAh g −1, respectively at 100th cycle. Analysis of change of delithiation capacity with cycling and delithiation current between 0.3 and 0.6 V from cyclic voltammogram (CV) along with scanning electron microscope (SEM) and X-ray diffraction (XRD) of the electrodes/composites leads to conclude thermal processing of the organic slurry treated pristine composite converts dispersed active materials of the pristine composite into a compact structure trapped/wrapped with carbon particles (C x, x varies from 1 to 3) providing apparently a resistor like behaviour and makes the anode deliver a stable reversible capacity with cycling.

Lithium recycling behaviour of nano-phase-CuCo 2O 4 as anode for lithium-ion batteries

Nano-CuCo 2O 4 is synthesized by the low-temperature (400 °C) and cost-effective urea combustion method. X-ray diffraction (XRD), high resolution transmission electron microscopy (HR-TEM) and selected area electron diffraction (SAED) studies establish that the compound possesses a spinel structure and nano-particle morphology (particle size (10–20 nm)). A slight amount of CuO is found as an impurity. Galvanostatic cycling of CuCo 2O 4 at 60 mA g −1 in the voltage range 0.005–3.0 V versus Li metal exhibits reversible cycling performance between 2 and 50 cycles with a small capacity fading of 2 mAh g −1 per cycle. Good rate capability is also found in the range 0.04–0.94 C. Typical discharge and charge capacity values at the 20th cycle are 755(±10) mAh g −1 (∼6.9 mol of Li per mole of CuCo 2O 4) and 745(±10) mAh g −1 (∼6.8 mol of Li), respectively at a current of 60 mA g −1. The average discharge and charge potentials are ∼1.2 and ∼2.1 V, respectively. The underlying reaction mechanism is the redox reaction: Co ↔ CoO ↔ Co 3O 4 and Cu ↔ CuO aided by Li 2O, after initial reaction with Li. The galvanostatic cycling studies are complemented by cyclic voltammetry (CV), ex situ TEM and SAED. The Li-cycling behaviour of nano-CuCo 2O 4 compares well with that of iso-structural nano-Co 3O 4 as reported in the literature.

CeO 2 thin films obtained by sol–gel deposition and annealed in air or argon

Thin films of CeO 2 were prepared on SnO 2/F-coated glass plates by the sol–gel dip-coating process using CeCl 3·7H 2O as a precursor. The films were heat-treated in an air or argon atmosphere. The structural, electrochemical and optical properties of these films depend on the preparation conditions. Transmission electron microscopy (TEM) showed the films to be polycrystalline with randomly orientated crystallised domains of up to 10 nm in size. The degree of crystallinity of films heat-treated in argon is higher than that of those heat-treated in air, and therefore their charge capacity values (15.9 mC cm −2 after 100 cycles) and reversibility of the ion-storage process (0.99 after 100 cycles) are higher than for films heat-treated in air (10.5 mC cm −2 and 0.86 after 100 cycles, respectively). Both films are optically passive under Li + ion insertion and have high optical transmittance (>80%).