A highly coking-resistant solid oxide fuel cell with a nickel doped ceria: Ce1−xNixO2−y reformation layer

A single phase mixed oxide ion-electron conducting electrochemical catalyst of Ce_1−xNi_xO_2−y is employed as an anode functional reformation layer for a coking-resistant solid oxide fuel cell (SOFC) based on oxide ion conducting electrolyte operated in methane and ethanol. The high catalytic activity of Ce_1−xNi_xO_2−y oxide for fuel reformation is demonstrated by the excellent cell performances in various fuels at relatively low temperatures (550–650 °C). The fast oxygen ions flux and formed steam at anode side are also found to be favorable for hydrocarbon reformation to promote the cell performance and long term stability. At 650 °C, maximum power densities of 415 and 271 mW cm⁻² are achieved in methane and ethanol respectively. The resistance against carbon deposition is significantly improved with stable voltage output in a long-term durability operation.     

Cu1−xPdx/CeO2-impregnated cermet anodes for direct oxidation of methane in LaGaO3-electrolyte solid oxide fuel cells

A series of ceramic-metal composite anodes containing 1.0 wt.% Cu_1−xPd_x alloys (where x = 0, 0.15, 0.25, 0.4, 0.5, 0.75 and 1.0) were prepared by impregnation of the respective metal salts and 5.0 wt.% CeO₂ into a porous La_0.4Ce_0.6O_2−σ anode skeleton. The performance of these anodes was evaluated in both dry H₂ and CH₄ in the temperature range of 700-800 °C using the 300-μm thick La_0.8Sr_0.2Ga_0.83Mg_0.17O_3−σ (LSGM) electrolyte-supported solid oxide fuel cells (SOFCs). The addition of Pd to Cu significantly increased the performance of the single cells in dry CH₄, with the cell maximum power density changed from 66 mW cm⁻² for Cu_1.0Pd_0.0 to 345 mW cm⁻² for Cu_0.0Pd_1.0 at 800 °C. In H₂, however, the performance improvement was not as significant compared to that in CH₄. In addition, carbon formation was greatly suppressed in the Cu-Pd alloy-impregnated anodes compared to that with pure Pd after exposure to dry CH₄ at 800 °C, which led to different performance stability behaviors for these cells operating with dry CH₄.     

Physical and electrochemical properties of spherical Li1+x(Ni1/3Co1/3Mn1/3)1−xO2 cathode materials

A (Ni_1/3Co_1/3Mn_1/3)CO₃ precursor with an uniform, spherical morphology was prepared by coprecipitation using a continuously stirred tank reactor method. The as-prepared spherical (Ni_1/3Co_1/3Mn_1/3)CO₃ precursor served to produce dense, spherical Li_1+x(Ni_1/3Co_1/3Mn_1/3)_1−xO₂ (0 ≤ x ≤ 0.15) cathode materials. These Li-rich cathodes were also prepared by a second synthesis route that involved the use of an M₃O₄ (M = Ni_1/3Co_1/3Mn_1/3) spinel compound, itself obtained from the carbonate (Ni_1/3Co_1/3Mn_1/3)CO₃ precursor. In both cases, the final Li_1+x(Ni_1/3Co_1/3Mn_1/3)_1−xO₂ products were highly uniform, having a narrow particle size distribution (10-μm average particle size) as a result of the homogeneity and spherical morphology of the starting mixed-metal carbonate precursor. The rate capability of the Li_1+x(Ni_1/3Co_1/3Mn_1/3)_1−xO₂ electrode materials, which was significantly improved with increased lithium content, was found to be better in the case of the denser materials made from the spinel precursor compound. This result suggests that spherical morphology, high density, and increased lithium content were key factors in enabling the high rate capabilities, and hence the power performances, of the Li-rich Li_1+x(Ni_1/3Co_1/3Mn_1/3)_1−xO₂ cathodes.     

Minimization of the cation mixing in Li1+x(NMC)1−xO2 as cathode material

Li_1+x(Ni_1/3Mn_1/3Co_1/3)_1−xO₂ layered materials were synthesized by the co-precipitation method with different Li/M molar ratios (M = Ni + Mn + Co). Elemental titration evaluated by inductively coupled plasma spectrometry (ICP), structural properties studied by X-ray diffraction (XRD), Rietveld analysis of XRD data, scanning electron microscopy (SEM) and magnetic measurements carried out by superconducting quantum interference devices (SQUID) showed the well-defined α-NaFeO₂ structure with cationic distribution close to the nominal formula. The Li/Ni cation mixing on the 3b Wyckoff site of the interlayer space was consistent with the structural model [Li_1−yNi_y]_3b[Li_x+yNi_{(1−x)/3−y}Mn_(1−x)/3Co_(1−x)/3]_3aO₂ (x = 0.02, 0.04) and was very small. Both Rietveld refinements and magnetic measurements revealed a concentration of Ni²⁺-3b ions lower than 2%; moreover, for the optimized sample synthesized at Li/M = 1.10, only 1.43% of nickel ions were located into the Li sublattice. Electrochemical properties were investigated by galvanostatic charge-discharge cycling. Data obtained with Li_1+x(Ni_1/3Mn_1/3Co_1/3)_1−xO₂ reflected the high degree of sample optimization. An initial discharge capacity of 150 mAh g⁻¹ was delivered at 1 C-rate in the cut-off voltage of 3.0-4.3 V. More than 95% of its initial capacity was retained after 30 cycles at 1 C-rate. Finally, it is demonstrated that a cation mixing below 2% is considered as the threshold for which the electrochemical performance does not change for Li_1+x(Ni_1/3Mn_1/3Co_1/3)_1−xO₂.     

Potentiodynamic deposition of composition influenced Co1−xNix LDHs thin film electrode for redox supercapacitors

Current paper comprises the electrodeposition of nanostructured porous Co_1−xNi_x layered double hydroxide (Co_1−xNi_x LDHs) thin films on to stainless steel substrate by a potentiodynamic mode. The compositional impacts on the various properties of Co_1−xNi_x LDHs are examined via structural, morphological, surface wettability and electrochemical studies. The nanocrystalline Co_1−xNi_x LDHs thin films possess varying porous, nanoflake like morphology and superhydrophilic behavior by the composition influence. Electrochemical studies demonstrate the supercapacitive performance of Co_1−xNi_x LDHs thin film electrodes. The maximal specific capacitance for Co_1−xNi_x LDHs electrode is found to be ∼1213 F g⁻¹ for composition Co_0.66Ni_0.34 LDH in 2 M KOH electrolyte at 5 mV s⁻¹ scan rate owing specific energy of 104 Whkg⁻¹, specific power of 1.44 kW kg⁻¹ with ∼94% of coulomb efficiency and stability of electrode retained to 77% after 10,000th cycle. The high capacitance retention proposes the deposited Co_1−xNi_x LDHs thin film as promising contender for supercapacitor applications.     

Potentiostatically deposited nanostructured CoxNi1−x layered double hydroxides as electrode materials for redox-supercapacitors

Cobalt–nickel layered double hydroxides (Co_xNi_1−x LDHs) were deposited onto stainless steel electrodes by the potentiostatic deposition method at −1.0 V vs. Ag/AgCl using various molar ratios of Co(NO₃)₂ and Ni(NO₃)₂ in distilled water. Their structure and surface morphology were studied by using X-ray diffraction analysis, energy dispersive X-ray spectroscopy and scanning electron microscopy. A network of Co_xNi_1−x LDH nanosheets was obtained. The nature of the cyclic voltammetry and charge–discharge curves suggested that the Co_xNi_1−x LDHs exist in the form of solid solutions. The capacitive characteristics of the Co_xNi_1−x LDHs in 1 M KOH electrolyte showed that Co_0.72Ni_0.28 LDHs had the highest specific capacitance value, 2104 F g⁻¹, which is also the highest yet reported value for oxide materials in general.     

Electrochemical performance and kinetics of Li1+x(Co1/3Ni1/3Mn1/3)1−xO2 cathodes and graphite anodes in low-temperature electrolytes

Lithium-ion batteries have started replacing the conventional aqueous nickel-based battery systems in space applications, such as planetary landers, rovers, orbiters and satellites. The reasons for such widespread use of these batteries are the savings in mass and volume of the power subsystems, resulting from their high gravimetric and volumetric energy densities, and their ability to operate at extreme temperatures. In our pursuit to further enhance the specific energy as well as low-temperature performance of Li-ion batteries, we have been investigating various layered lithiated metal oxides, e.g., LiCoO₂, LiNi_0.8Co_0.2 and LiNi_0.8Co_0.15Al_0.05O₂, as well as different low-temperature electrolytes, including ternary and quaternary carbonate mixtures with various co-solvents. In this paper, we report our recent studies on Li_1+x(Co_1/3Ni_1/3Mn_1/3)_1−xO₂ cathodes, combined with three different low-temperature electrolytes, i.e.: (1) 1.0 M LiPF₆ in EC:EMC (20:80), (2) 1.2 M LiPF₆ in EC:EMC (20:80) and (3) 1.2 M LiPF₆ in EC:EMC (30:70). Electrical performance characteristics were determined in laboratory glass cells at different discharge rates and different temperatures. Further, individual electrode kinetics of both Li_1+x(Co_1/3Ni_1/3Mn_1/3)_1−xO₂ cathodes and MCMB graphite anodes were determined at different temperatures, using dc micropolarization, Tafel polarization and electrochemical impedance spectroscopy (EIS). Analysis of these data has led to interesting trends relative to the effects of solvent composition and salt concentration, on the electrical performance and on the kinetics of cathode and anode.     

Biogas reforming for hydrogen production over mesoporous Ni2xCe1−xO2 catalysts

Biogas reforming for hydrogen production over mesoporous Ni_2xCe_1−xO₂ catalysts were proposed in this study. Mesoporous Ni_2xCe_1−xO₂ (x = 0.05, 0.13, 0.2) was prepared by a reverse precipitation method. The effects of nickel content were investigated in physicochemical properties and catalytic activities. All of the catalysts were reduced with 10% H₂/Ar at 600 °C before reactions, the reduced catalysts were found to be active for both dry and steam reforming of methane (CH₄:CO₂:H₂O = 3:1:2) to produce hydrogen and syngas. The studies were firstly carried out by temperature program reaction from 400 °C to 900 °C to verify the activity of temperature dependency. The long-term stability analysis was also studied at 700 °C for 24 h. Commercial catalyst (R67) was also employed for a comparative purpose.     

Electrochemical performance of La2Cu1−xCoxO4 cathode materials for intermediate-temperature SOFCs

K₂NiF₄-type structure oxides La₂Cu_1−xCo_xO₄ (x = 0.1, 0.2, 0.3) are synthesized and evaluated as cathode materials for intermediate temperature solid oxide fuel cells (IT-SOFCs). The materials are characterized by XRD, SEM and electrochemical impedance spectrum (EIS), respectively. The results show that no reaction occurs between La₂Cu_1−xCo_xO₄ electrode and Ce_0.9Gd_0.1O_1.95 (CGO) electrolyte at 1000 °C. The electrode forms good contact with the electrolyte after sintering at 800 °C for 4 h in air. The electrode properties of La₂Cu_1−xCo_xO₄ are studied under various temperatures and oxygen partial pressures. The optimum composition of La₂Cu_0.8Co_0.2O₄ results in 0.51 Ω cm² polarization resistance (R_p) at 700 °C in air. The rate limiting step for oxygen reduction reaction (ORR) is the charge transfer process. La₂Cu_0.8Co_0.2O₄ cathode exhibits the lowest overpotential of about 50 mV at a current density of 48 mA cm⁻² at 700 °C in air.     

Sm0.2(Ce1−xTix)0.8O1.9 modified Ni-yttria-stabilized zirconia anode for direct methane fuel cell

Sm_0.2(Ce_1−xTi_x)_0.8O_1.9 (SCTx, x = 0-0.29) modified Ni-yttria-stabilized zirconia (YSZ) has been fabricated and evaluated as anode in solid oxide fuel cells for direct utilization of methane fuel. It has been found that both the amount of Ti-doping and the SCTx loading level in the anode have substantial effect on the electrochemical activity for methane oxidation. Optimal anode performance for methane oxidation has been obtained for Sm_0.2(Ce_0.83Ti_0.17)_0.8O_1.9 (SCT0.17) modified Ni-YSZ anode with SCT0.17 loading of about 241 mg cm⁻² resulted from four repeated impregnation cycles. When operating on humidified methane as fuel and ambient air as oxidant at 700 °C, single cells with the configuration of SCT0.17 modified Ni-YSZ anode, YSZ electrolyte and La_0.6Sr_0.4Co_0.2Fe_0.8O₃-Sm_0.2Ce_0.8O_1.9 (LSCF-SDC) composite cathode show the polarization cell resistance of 0.63 Ω cm² under open circuit conditions and produce a peak power density of 383 mW cm⁻². It has been revealed that the coated Ti-doped SDC on Ni-YSZ anode not only effectively prevents the methane fuel from directly impacting on the Ni particles, but also enhances the kinetics of methane oxidation due to an improved oxygen storage capacity (OSC) and redox equilibrium of the anode surface, resulting in significant enhancement of the SCTx modified Ni-YSZ anode for direct methane oxidation.     

Perovskite-type Sr(Mn1−xNix)O3 materials and their chemical-looping oxygen transfer properties

This paper contains the results of research on chemical-looping combustion (CLC). CLC is one of the most promising combustion technologies and has the main advantage of producing a concentrated CO₂ stream, which is obtained after water condensation and without any energy penalty for CO₂ separation. The objective of this work was to study the chemical-looping reaction performance of novel perovskite-type oxygen carriers. The Sr(Mn_1−xNi_x)O₃ family was tested for its suitability as an oxygen carrier in hydrogen (syngas component) combustion for power generation. Sr(Mn_1−xNi_x)O₃ perovskite-type oxides with x = 0, 0.2, 0.5, 0.8, and 1.0 were prepared. Thermogravimetric measurements were performed to investigate the oxidation/reduction of the obtained materials. Reactivity tests were performed under isothermal conditions during multiple redox cycles using a thermogravimetric analyzer (TGA). For the reduction reaction, 3% H₂ in Ar was used, and air was used for the oxidation cycle. The effect of reaction temperature (600–800 °C) and the number of reducing/oxidizing cycles (up to 5 cycles) on the performance of the oxygen-carrier samples developed in this study were evaluated. The stability, oxygen transport capacity, and reaction rates were analyzed on the basis of thermogravimetric TG results. The Sr(Mn_1−xNi_x)O₃ oxides showed stable chemical-looping performance with rapid changes in their oxygen content (2–3 min) while maintaining their chemical properties. The cyclic redox reaction revealed that Sr(Mn_1−xNi_x)O₃ exhibits excellent structural stability and provides a continuous oxygen supply during redox reactions. Good oxygen capacity was maintained during the cycling hydrogen combustion tests. These new perovskite-type materials were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD) measurements and by surface area (BET), particle size distribution (PSD) and melting behavior analyses. The Sr(Mn_1−xNi_x)O₃ oxides exhibited high melting temperatures and small surface areas. The promising results obtained from chemical-looping combustion experiments indicate that the Sr(Mn_1−xNi_x)O₃ oxides are potentially useful oxygen carriers for chemical-looping combustion processes where hydrogen is one of the fuel components.     

Structural and transport properties of layered Li1+x(Mn1/3Co1/3Ni1/3)1−xO2 oxides prepared by a soft chemistry method

In this work structural and transport properties of layered Li_1+x(Mn_1/3Co_1/3Ni_1/3)_1−xO₂ oxides (x = 0; 0.03; 0.06) prepared by a “soft chemistry” method are presented. The excessive lithium was found to significantly improve transport properties of the materials, a corresponding linear decrease of the unit cell parameters was observed. The electrical conductivity of Li_1.03(Mn_1/3Co_1/3Ni_1/3)_0.97O₂ composition was high enough to use this material in a form of a pellet, without any additives, in lithium batteries and characterize structural and transport properties of deintercalated Li_1.03−y(Mn_1/3Co_1/3Ni_1/3)_0.97O₂ compounds. For deintercalated samples a linear increase of the lattice parameter c together with a linear decrease of the parameter a with the increasing deintercalation degree occurred, but only up to 0.4-0.5 mol of extracted lithium. Further deintercalation showed a reversal of the trend. Electrical conductivity measurements performed of Li_1.03−y(Mn_1/3Co_1/3Ni_1/3)_0.97O₂ samples (y = 0.1; 0.3; 0.5; 0.6) showed an ongoing improvement, almost two orders of magnitude, in relation to the starting composition. Additionally, OCV measurements, discharge characteristics and lithium diffusion coefficient measurements were performed for Li/Li⁺/Li_1.03−y(Mn_1/3Co_1/3Ni_1/3)_0.97O₂ cells.     

Assessment of perovskite-type La0.8Sr0.2ScxMn1−xO3-δ oxides as anodes for intermediate-temperature solid oxide fuel cells using hydrocarbon fuels

Composites formed by the infiltration of 40 wt% La_0.8Sr_0.2Sc_xMn_1−xO_3-δ (LSSM) oxides (x = 0.1, 0.2, 0.3) into 65% porous yttria-stabilized zirconia (YSZ) are investigated as anode materials for intermediate-temperature solid oxide fuel cells for hydrocarbon oxidation. The oxygen non-stoichiometry and electrical conductivity of each LSSM-YSZ composite are determined by coulometric titration. As the concentration of Sc increases, the composites show higher phase stability and the electrical conductivity of LSSM is significantly affected by the Sc doping, the non-stoichiometric oxygen content, and oxygen partial pressure (p(O₂)). To achieve better electrochemical performance, it is necessary to add ceria-supported palladium catalyst for operation with humidified CH₄. Anode polarization resistance increases with Sc doping due to a decrease in electrical conductivity. An electrolyte-supported cell with a LSSM-YSZ composite anode delivers peak power densities of 395 and 340 mW cm⁻² at 923 K in humidified (3% H₂O) H₂ and CH₄, respectively, at a flow rate of 20 mL min⁻¹.     

Cation ordering in the layered Li1+x(Ni0.425Mn0.425Co0.15)1 − xO2 materials (x = 0 and 0.12)

The layered Li_1+x(Ni_0.425Mn_0.425Co_0.15)_1 − xO₂ (x = 0 and 0.12) materials were prepared by a coprecipitation method. Their structure was investigated using the combination of X-ray and electron diffraction experiments. For both materials (x = 0 and 0.12), the electron diffraction patterns revealed an in-plane √3a_hex. × √3a_hex. superstructure in agreement with the ordering of the Li⁺, Ni²⁺, Ni³⁺, Mn⁴⁺ and Co³⁺ ions in the transition metal layers. The stoichiometry of these materials was not in agreement with an ideal ordering: the possible presence of point defects or of a domain microstructure was thus discussed. Electron diffraction also revealed that these ordered layers were slightly correlated along the c_hex. axis for both materials.     

Synthesis and electrochemical properties of Li[Ni0.45Co0.1Mn0.45−xZrx]O2 (x = 0, 0.02) via co-precipitation method

Li[Ni_0.45Co_0.1Mn_0.45−xZr_x]O₂ (x = 0, 0.02) was synthesized via co-precipitation method. Partial Zr doping on the host structure of Li[Ni_0.45Co_0.1Mn_0.45]O₂ was carried out to improve the electrochemical properties. The Zr-doped Li[Ni_0.45Co_0.1Mn_0.43Zr_0.02]O₂ was evaluated in terms of specific discharge capacity, cycling performance and thermal stability. The Zr-doped Li[Ni_0.45Co_0.1Mn_0.45−xZr_0.02]O₂ shows the improved cycling performance and stable thermal stability. The major exothermic reaction was delayed from 252.1 °C to 289.4 °C.     

New Nb-doped SrCo1−xNbxO3−δ perovskites performing as cathodes in solid-oxide fuel cells

The high-temperature cubic phase of SrCoO_3−δ is a promising cathode material for solid oxide fuel cells (SOFC) due to its high electrical conductivity and oxygen permeation flux. However, this phase is not stable below 900 °C where a 3C-cubic to 2H-hexagonal phase transition takes place when the sample is slowly cooled down. In this work we have stabilized a 3C-tetragonal P4/mmm structure for SrCo_1−xNb_xO_3−δ with x = 0.05. We have followed the strategy consisting of introducing a highly-charged cation at the Co sublattice, in order to avoid the stabilization of the unwanted 2H structure containing face-sharing octahedra. The characterization of this oxide included X-ray (XRD) and neutron powder diffraction (NPD) experiments. SrCo_0.95Nb_0.05O_3−δ adopts a tetragonal superstructure of perovskite with a = a₀, c = 2a₀ (a₀ ≈ 3.9 Å) defined in the P4/mmm space group containing two inequivalent Co positions. Flattened and elongated (Co,Nb)O₆ octahedra alternate along the c axis sharing corners in a three-dimensional array (3C-like structure). In the test cell, the electrodes were supported on a 300-μm-thick pellet of the electrolyte La_0.8Sr_0.2Ga_0.83Mg_0.17O_3−δ (LSGM). The test cells gave a maximum power density of 0.4 and 0.6 W/cm² for temperatures of 800 and 850 °C, respectively, with pure H₂ as fuel and air as oxidant. The good performance of this material as a cathode is related to its mixed electronic-ionic conduction (MIEC) properties, which can be correlated to the investigated structural features: the Co³⁺/Co⁴⁺ redox energy at the top of the O-2p bands accounts for the excellent electronic conductivity, which is favored by the corner-linked perovskite network. The considerable number of oxygen vacancies, with the oxygen atoms showing high displacement factors suggests a significant ionic mobility.     

(Ni0.75Fe0.25-xMgO)/YSZ anode for direct methane solid-oxide fuel cells

(Ni_0.75Fe_0.25-xMgO)/YSZ samples—with a varying weight percentage x (0, 5%, 10%) of MgO with respect to Ni_0.75Fe_0.25—were prepared and studied as anodes for intermediate temperature solid oxide fuel cells (SOFCs) operated on humidified methane (3% H₂O). Among the cells with different anode compositions, it was found that the cell with the (Ni_0.75Fe_0.25-5%MgO)/YSZ anode showed the highest power density, giving 648 mW cm⁻² at 800 °C. The cells with MgO-doped anodes were able to operate stably for 20 h under a current density of 0.53 A cm⁻² at 700 °C without observed degradation, while the cells without MgO degraded rapidly. The mechanisms responsible for the superior performance and duration of the (Ni_0.75Fe_0.25-5%MgO)/YSZ anode were analyzed.     

Hydrogen storage properties of the pseudo binary laves phase (Sc1−xZrx)(Co1−yNiy)2 system

The (Sc_1−xZr_x)(Co_1−yNi_y)₂-H_z system has been studied using both experimental techniques and ab initio calculations. The material was synthesised through high temperature synthesis and characterised using powder XRD. Hydrogen absorption and desorption was studied in-situ using synchrotron radiation. Maximal storage capacity increased when Co replaced Ni and substitution of Sc for Zr increased the equilibrium pressure. Density functional based calculations reproduce the experimental trends in terms of cell parameters both for the non-hydrogenated systems as well as for the hydrogenated systems, and helped to quantitatively understand the observed hydrogen uptake properties.     

Synthesis and characterization of LiNi0.6Mn0.4−xCoxO2 as cathode materials for Li-ion batteries

LiNi_0.6Co_xMn_0.4−xO₂ (x = 0.05, 0.10, 0.15, 0.2) cathode materials are prepared, and their structural and electrochemical properties are investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), differential scanning calorimetric (DSC) and charge–discharge test. The results show that well-ordering layered LiNi_0.6Co_xMn_0.4−xO₂ (x = 0.05, 0.10, 0.15, 0.2) cathode materials are successfully prepared in air at 850 °C. The increase of the Co content in LiNi_0.6Mn_0.4−xCo_xO₂ leads to the acceleration of the grain growth, the increase of the initial discharge capacity and the deterioration of the cycling performance of LiNi_0.6Mn_0.4−xCo_xO₂. It also leads to the enhancement of the ratio Ni³⁺/Ni²⁺ in LiNi_0.6Co_xMn_0.4−xO₂, which is approved by the XPS analysis, resulting in the increase of the phase transition during cycling. This is speculated to be main reason for the deteriotion of the cycling performance. All synthesized LiNi_0.6Co_xMn_0.4−xO₂ samples charged at 4.3 V show exothermic peaks with an onset temperature of larger than 255 °C, and give out less than 400 J g⁻¹ of total heat flow associated with the peaks in DSC analysis profile, exhibiting better thermal stability. LiNi_0.6Co_0.05Mn_0.35O₂ with low Co content and good thermal stability presents a capacity of 156.6 mAh g⁻¹ and 98.5% of initial capacity retention after 50 cycles, showing to be a promising cathode materials for Li-ion batteries.