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.     

Structural and transport properties of LixNi1−y−zCoyMnzO2 cathode materials

In this work structural and transport properties of layered LiNi_1−y−zCo_yMn_zO₂ (y = 0.25, 0.35, 0.5 and z = 0.1) cathode materials are presented. In the considered group of oxides, LiNi_1−y−zCo_yMn_zO₂, there is no clear correlation between electrical conductivity and the a parameter (M-M distance in the octahedra layers). A non-monotonic modification of electrical properties of Li_xNi_0.65Co_0.25Mn_0.1O₂ cathode materials is observed upon lithium deintercalation.     

Effect of CO2 on layered Li1+zNi1−x−yCoxMyO2 (M = Al,Mn) cathode materials for lithium ion batteries

We investigated the effect of CO₂ on layered Li_1+zNi_1−x−yCo_xM_yO₂ (M = Al, Mn) cathode materials for lithium ion batteries which were prepared by solid-state reactions. Li_1+zNi_(1−x)/2Co_xMn_(1−x)/2O₂ (Ni/Mn mole ratio = 1) singularly exhibited high storage stability. On the other hand, Li_1+zNi_0.80Co_0.15Al_0.05O₂ samples were very unstable due to CO₂ absorption. XPS and XRD measurements showed the reduction of Ni³⁺ to Ni²⁺ and the formation of Li₂CO₃ for Li_1+zNi_0.80Co_0.15Al_0.05O₂ samples after CO₂ exposure. SEM images also indicated that the surfaces of CO₂-treated samples were covered with passivation films, which may contain Li₂CO₃. The relationship between CO₂-exposure time and CO₃²⁻ content suggests that there are two steps in the carbonation reactions; the first step occurs with the excess Li components, Li₂O for example, and the second with LiNi_0.80Co_0.15Al_0.05O₂ itself. It is well consistent with the fact that the discharge capacity was not decreased and the capacity retention was improved until the excess lithium is consumed and then fast deterioration occurred.     

The influence of compositional change of 0.3Li2MnO3·0.7LiMn1−xNiyCo0.1O2 (0.2 ≤ x ≤ 0.5, y = x − 0.1) cathode materials prepared by co-precipitation

Cathode materials prepared by a co-precipitation are 0.3Li₂MnO₃·0.7LiMn_1−xNi_yCo_0.1O₂ (0.2 ≤ x ≤ 0.4) cathode materials with a layered-spinel structure. In the voltage range of 2.0-4.6 V, the cathodes show more than one redox reaction peak during its cyclic voltammogram. The Li/0.3Li₂MnO₃·0.7LiMn_1−xNi_yCo_0.1O₂ (x = 0.3, y = 0.2) cell shows the initial discharge capacity of about 200 mAh g⁻¹. However, when x = 0.2 and y = 0.1, the cell exhibits a rapid decrease in discharge capacity and poor cycle life.     

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.     

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.     

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.     

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.     

Pillared layered Li1−2xCaxCoO2 cathode materials obtained by cationic exchange under hydrothermal conditions

A simple method has been employed to prepare pillared layered Li_1−2xCa_xCoO₂ cathode materials by cationic exchange under hydrothermal conditions. The synthesized materials were characterized by means of X-ray diffraction (XRD), inductively coupled plasma-atomic emission spectroscopy (ICP-AES), field emission scanning electron microscope (FE-SEM) and galvanostatic charge–discharge cycling. The XRD data of the products show that they are single phases and retain the layered α-NaFeO₂ type structure. The FE-SEM images of the materials prepared by hydrothermal method show uniform small particles, and the particle size of the materials is about 200 nm. The initial discharge specific capacities of layered LiCoO₂ and pillared layered Li_0.946Ca_0.027CoO₂ cathode materials calcined at 800 °C for 5 h within the potential range of 3.0–4.3 V (vs. Li⁺/Li) are 144.6 and 142.3 mAh g⁻¹, respectively, and both materials retain good charge–discharge cycling performance. However, with increasing upper cutoff voltage, the pillar effect of Ca²⁺ in Li_1−2xCa_xCoO₂ becomes more significant. The pillared layered Li_0.946Ca_0.027CoO₂ has a higher capacity with an initial discharge specific capacity of 177.9 and 215.8 mAh g⁻¹ within the potential range of 3.0–4.5 and 4.7 V (vs. Li⁺/Li), respectively, and retains good charge–discharge cycling performance.     

Synthesis and electrochemical properties of Li1−xFe0.8Ni0.2O2–LixMnO2 (Mn/(Fe + Ni + Mn) = 0.8) material

A new type of Li_1−xFe_0.8Ni_0.2O₂–Li_xMnO₂ (Mn/(Fe + Ni + Mn) = 0.8) material was synthesized at 350 °C in air atmosphere using a solid-state reaction. The material had an XRD pattern that closely resembled that of the original Li_1−xFeO₂–Li_xMnO₂ (Mn/(Fe + Mn) = 0.8) with much reduced impurity peaks. The Li/Li_1−xFe_0.8Ni_0.2O₂–Li_xMnO₂ cell showed a high initial discharge capacity above 192 mAh g⁻¹, which was higher than that of the parent Li/Li_1−xFeO₂–Li_xMnO₂ (186 mAh g⁻¹). We expected that the increase of initial discharge capacity and the change of shape of discharge curve for the Li/Li_1−xFe_0.8Ni_0.2O₂–Li_xMnO₂ cell is the result from the redox reaction from Ni²⁺ to Ni³⁺ during charge/discharge process. This cell exhibited not only a typical voltage plateau in the 2.8 V region, but also an excellent cycle retention rate (96%) up to 45 cycles.     

Structural and electrochemical studies of Ba0.6Sr0.4Co1−yTiyO3−δ as a new cathode material for IT-SOFCs

The influence of titanium doping level in Ba_0.6Sr_0.4Co_1−yTi_yO_3−δ (BSCT) oxides on their phase structure, electrical conductivity, thermal expansion coefficient (TEC), and single-cell performance with BSCT cathodes has been investigated. The incorporation of Ti can lead to the phase transition of Ba_0.6Sr_0.4CoO_3−δ from hexagonal to cubic structure. The solid solution limitation of Ti in Ba_0.6Sr_0.4Co_1−yTi_yO_3−δ is 0.15–0.3 under 1100 °C. BSCT shows a small polaron conduction behavior and the electrical conductivity increases steadily in the testing temperature range (300–900 °C), leading to a relatively high conductivity at high temperatures. The electrical conductivity decreases with increasing Ti content. The addition of Ti deteriorates the cathode performance of BSCT slightly but decreases the TEC significantly. The TEC of BSCT is about 14 × 10⁻⁶ K⁻¹, which results in a good physical compatibility of BSCT with Gd_0.2Ce_0.8O_2−δ (GDC) electrolyte. BSCT also shows excellent thermal cyclic stability of electrical conductivity and good chemical stability with GDC. These properties make BSCT a promising cathode candidate for intermediate temperature solid oxide fuel cells (IT-SOFCs).     

An amorphous LiCo1/3Mn1/3Ni1/3O2 thin film deposited on NASICON-type electrolyte for all-solid-state Li-ion batteries

Amorphous LiCo_1/3Mn_1/3Ni_1/3O₂ thin films were deposited on the NASICON-type Li-ion conducting glass ceramics, Li_1+x+yAl_xTi_2−xSi_yP_3−yO₁₂ (LATSP), by radio frequency (RF) magnetron sputtering below 130 °C. The amorphous films were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The Li/PEO₁₈-Li(CF₃SO₂)₂N/LATSP/LiCo_1/3Mn_1/3Ni_1/3O₂/Au all-solid-state cells were fabricated to investigate the electrochemical performance of the amorphous films. It was found that the low-temperature deposited amorphous cathode film shows a high discharge voltage and a high discharge capacity of around 130 mAh g⁻¹.     

Structure, morphology, and cathode performance of Li1−x[Ni0.5Mn1.5]O4 prepared by coprecipitation with oxalic acid

The cathode materials Li_1−x[Ni_0.5Mn_1.5]O₄ prepared by coprecipitation from acetate solution by oxalic acid and annealing at 900 °C in air had the preferred disordered Ni and Mn on the 16d octahedral sites of a spinel structure. The coprecipitation method provides better crystallinity than the phase previously obtained by quenching from the melt. Polycrystalline octahedral-shaped particles with smooth surfaces contained trace amounts of a Li_yNi_1−yO impurity that introduced some Mn(III) into the spinel phase. Half-cells cycled at 0.2 C rate between 3.5 and 4.8 V versus Li exhibited a flat voltage V ≈ 4.7 V with a small step at x ≈ 0.5 and a capacity at room temperature of 130 mAh g⁻¹ that showed no fade after 50 cycles. A small capacity fade was initiated with a cut-off voltage ≥4.9 V; a significant capacity loss between 2 and 5 C cycling rates was reversible to 134 mAh g⁻¹ on returning to 0.1 C after 50 cycles at 10 C between 3.5 and 5.0 V.     

Structural and electrochemical characterization of xLi[Li1/3Mn2/3]O2·(1 − x)Li[Ni1/3Mn1/3Co1/3]O2 (0 ≤ x ≤ 0.9) as cathode materials for lithium ion batteries

A series of cathode materials with molecular notation of xLi[Li_1/3Mn_2/3]O₂·(1 − x)Li[Ni_1/3Mn_1/3Co_1/3]O₂ (0 ≤ x ≤ 0.9) were synthesized by combination of co-precipitation and solid state calcination method. The prepared materials were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques, and their electrochemical performances were investigated. The results showed that sample 0.6Li[Li_1/3Mn_2/3]O₂·0.4Li[Ni_1/3Mn_1/3Co_1/3]O₂ (x = 0.6) delivers the highest capacity and shows good capacity-retention, which delivers a capacity ∼250 mAh g⁻¹ between 2.0 and 4.8 V at 18 mA g⁻¹.     

Synthesis and electrochemical properties of lithium non-stoichiometric Li1+x(Ni1/3Co1/3Mn1/3)O2+δ prepared by a spray drying method

Lithium non-stoichiometric Li[Li_x(Ni_1/3Co_1/3Mn_1/3)_1−x]O₂ materials (0 ≤ x ≤ 0.17) were synthesized using a spray drying method. The electrochemical properties and structural stabilities of the synthesized materials were investigated. The synthesized materials exhibited a hexagonal structure in all the x-value and the lattice parameters of the materials were gradually decreased with increasing x-value due to an increasing amount of Ni³⁺ ions for charge compensation. The capacity retention ability and rate capability of the stoichiometric Li(Ni_1/3Co_1/3Mn_1/3)O₂ material were improved by increasing x-value, the so-called overlithiation. We found that the overlithiated materials could keep more structural integrity than the stoichiometric one during electrochemical cyclings, which could be one of reasons for a better electrochemical properties of the overlithiated materials.     

Electronic structure and water splitting under visible-light irradiation of Zn and Ag co-doped In(OH)ySz photocatalysts

Zinc and silver co-doped In(OH)_yS_z with nanocubic blocks morphology were prepared by a one-step hydrothermal method and their photocatalytic activities were investigated. The as-synthesized products were characterized by transmission electron microscopy (TEM), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), inductively coupled plasma (ICP) and UV–visible spectroscopy. The electron microscope observations revealed that the particle sizes of Zn-doped In(OH)_yS_z crystals were smaller than that of the non-doped In(OH)_yS_z, which accords with BET results. While Zn–Ag co-doped In(OH)_yS_z showed the nanocubic blocks with different particle sizes. The UV–vis spectra indicate that the single Zn ions doping leads to the absorbance band shifts toward lower wavelength upon increasing the Zn doping. Consequently, the band gap of In(OH)_yS_z also increases gradually with increasing the Zn doping. In contrast, an obvious red-shift is observed for Zn–Ag co-doped In(OH)_yS_z solid solution, which mainly attributed to the transition from Ag 4d + S 3p orbitals to Zn 4s + In 5s orbitals. The sample doped with 4 mol% Ag and Zn was found to have the highest activity, which is 20 times that of the In(OH)_yS_z.     

Hydrogen production from ethanol steam reforming over core–shell structured NixOy–, FexOy–, and CoxOy–Pd catalysts

The present work focused on the investigation of the hydrogen generation through the ethanol steam reforming over the core–shell structured Ni_xO_y–, Fe_xO_y–, and Co_xO_y–Pd loaded Zeolite Y catalysts. The transmission electron microscopy (TEM) image of Ni_xO_y–Pd represented a very clear core–shell structure, but the other two catalysts, Co_xO_y– and Fe_xO_y–Pd, were irregular and non-uniform. The catalytic performances differed according to the added core metal and the support. The core–shell structured Co_xO_y–Pd/Zeolite Y provided a significantly higher reforming reactivity compared to the other catalysts. The H₂ production was maximized to 98% over Co_xO_y–Pd(50.0 wt%)/Zeolite Y at the conditions of reaction temperature 600 °C, CH₃CH₂OH:H₂O = 1:3, and GHSV (gas hourly space velocity) 8400 h⁻¹. In the mechanism that was suggested in this work, the cobalt component played an important role in the partial oxidation and the CO activation for acetaldehyde and CO₂ respectively, and eventually, cobalt increased the hydrogen yield and suppressed the CO generation.     

Preparation and characterization of sub-micro LiNi0.5−xMn1.5+xO4 for 5 V cathode materials synthesized by an ultrasonic-assisted co-precipitation method

Sub-micro spinel LiNi_0.5−xMn_1.5+xO₄ (x < 0.1) cathode materials powder was successfully synthesized by the ultrasonic-assisted co-precipitation (UACP) method. The structure and electrochemical performance of this as-prepared powder were characterized by powder XRD, SEM, XPS, CV and the galvanostatic charge–discharge test in detail. XRD shows that there is a small Li_yNi_1−yO impurity peak placed close to the (4 0 0) line of the spinel LiNi_0.5−xMn_1.5+xO₄, and the powders are well crystallized. XPS exhibits that the Mn oxidation state is between +3 and +4, and Ni oxidation state is +2 in LiNi_0.5−xMn_1.5+xO₄. SEM shows that the prepared powders (UACP) have the uniform and narrow size distribution which is less than 200 nm. Galvanostatic charge–discharge test indicates that the initial discharge capacities for the LiNi_0.5−xMn_1.5+xO₄ (UACP) at C/3, 1C and 2C, are 130.2, 119.0 and 110.0 mAh g⁻¹, respectively. After 100 cycles, their capacity retentions are 99.8%, 88.2%, and 73.5%, respectively. LiNi_0.5−xMn_1.5+xO₄ (UACP) at C/3 discharge rate exhibits superior capacity retention upon cycling, and it also shows well high current discharge performance. CV curve implies that LiNi_0.5−xMn_1.5+xO₄ (x < 0.1) spinel synthesized by ultrasonic-assisted co-precipitation method has both reversibility and cycle capability because of the ultrasonic-catalysis.     

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.     

High-throughput studies of Li1−xMgx/2FePO4 and LiFe1−yMgyPO4 and the effect of carbon coating

A two-dimensional sample array synthesis has been used to screen carbon-coated Li_(1−x)Mg_x/2FePO₄ and LiFe_(1−y)Mg_yPO₄ powders as potential positive electrode materials in lithium ion batteries with respect to x, y and carbon content. The synthesis route, using sucrose as a carbon source as well as a viscosity-enhancing additive, allowed introduction of the Mg dopant from solution into the sol–gel pyrolysis precursor. High-throughput XRD and cyclic voltammetry confirmed the formation of the olivine phase and percolation of the electronic conduction path at sucrose to phosphate ratios between 0.15 and 0.20. Measurements of the charge passed per discharge cycle showed that the capacity deteriorated on increasing magnesium in Li_(1−x)Mg_x/2FePO₄, but improved with increasing magnesium in LiFe_(1−y) Mg_yPO₄, especially at high scan rates. Rietveld-refined XRD results on samples of LiFe_(1−y)Mg_yPO₄ prepared by a solid-state route showed a single phase up to y = 0.1 according to progressive increases in unit cell volume with increases in y. Carbon-free samples of the same materials showed conductivity increases from 10⁻¹⁰ to 10⁻⁸ S cm⁻¹ and a decrease of activation energy from 0.62 to 0.51 eV. Galvanostatic cycling showed near theoretical capacity for y = 0.1 compared with only 80% capacity for undoped material under the same conditions.