AlF3-modified LiCoPO4 for an advanced cathode towards high energy lithium-ion battery

Surface-interface reaction between the electrode and electrolyte plays a key role in lithium-ion storage properties, especially for high voltage cathode such as LiCoPO₄ and Ni-riched cathode. Generally, surface modification is an effective method to improve the electrochemical performance of electrode materials. Herein, in order to revise the LiCoPO₄ cathode with desirable properties, uniform AlF₃-modified LiCoPO₄ (LiCoPO₄@AlF₃) cathode materials in nano-sized distribution are synthesized. XRD result indicates that there is no structural transformation observed after AlF₃ coating. TEM characterization and XPS analysis reveal that the surface of LiCoPO₄ particle is coated by a nano-sized uniform AlF₃ layer. Further, the electrochemical results indicate that AlF₃ layer significantly improves the cycling and rate performances of LiCoPO₄ cathode within the voltage range of 3.0–5.0 V. After a series of optimization, 4 mol% AlF₃-coated LiCoPO₄ material exhibits the best properties including an initial discharge capacity of 159 mA h g^?1 at 0.1 C with 91% capacity retention after 50 cycles, especially a discharge capacity of 90 mA h g^?1 can be obtained at 1 C rate. CV curves indicate that the polarization of cathode is reduced by AlF₃ layer and EIS curves reveal that AlF₃ layer relieves the increase of resistance to facilitate Li-ion transfer at the interface between electrode and electrolyte during the cycling process. The enhanced electrochemical performances are attributed to that the AlF₃ layer can stabilize the interface between the cathode and electrolyte, form steady SEI film and suppress the electrolyte continuous decomposition at 5 V high voltages. This feasible strategy and novel characteristics of LiCoPO₄@AlF₃ could promise the prospective applications in the stat-art of special lithium-ion battery with high energy and/or power density.     

A novel Li2TiO3–Li2CeO3 ceramic composite with excellent microwave dielectric properties for low-temperature cofired ceramic applications

A novel low-temperature sinterable (1 ? x)Li₂TiO₃-xLi₂CeO₃ (x = 0.08 ? 0.16 in molar) microwave dielectric ceramic was successfully prepared by a conventional solid-state reaction method. The X-ray diffraction and scanning electron microscopy analysis revealed the coexistence of two phases with different structures owing to their good chemical stability. Their relative content was easily adjusted to achieve near-zero temperature coefficient of the resonant frequency (τ_f) according to the mixing rule of dielectrics. The low-temperature sintering and desirable microwave dielectric properties can be simultaneously achieved by adding Li₂CeO₃ to the Li₂TiO₃ matrix owing to its low-firing characteristic and opposite-sign τ_f. The composite ceramics with x = 0.14 could be well sintered at 850 °C and exhibited excellent microwave dielectric properties of ε_r ～ 21.2, Qxf～ 59,039 GHz and τ_f ～?7.4 ppm/°C. In addition, no chemical reaction was identified between the matrix phase and Ag, suggesting that the Li₂TiO₃-Li₂CeO₃ ceramics might be promising candidates for low-temperature co-fired ceramic applications.     

The effect of AlF3 modification on the physicochemical and electrochemical properties of Li-rich layered oxide

Lithium (Li)-rich layered oxides are considered promising cathode materials for Li-ion batteries because of their favorable properties. Here, we report our recent finding in the novel oxide, aluminum fluoride (AlF₃)-modified Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ (LMNCAF), which was synthesized via a facile, cost-effective and readily scalable solid-state reaction. LMNCAF possess an F and Al co-doped core structure with a LiF nano-coating on its surface which leads to considerably enhancement in the electrochemical performance of the oxide. The initial discharge capacity (at 0.05 C) increased from 212 mA h g⁻¹ for Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ to 291 mA h g⁻¹ for LMNCAF. A much higher discharge capacity of 211 mA h g⁻¹ was obtained for LMNCAF after 99 charge/discharge cycles at 0.2 C compared with that of Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ (160 mA h g⁻¹). Our preliminary results suggest that AlF₃ modification is an effective strategy to tailor the physicochemical and electrochemical properties of Li-rich layered oxides.     

Hierarchical Li4Ti5O12 nanosheet arrays anchoring on carbon fiber cloth as ultra-stable free-standing anode of Li-ion battery

A flexible, free-standing composite anode with Li₄Ti₅O₁₂ nanosheet arrays anchoring on plain-weaved carbon fiber cloth (LTO@CC) is prepared by a hydrothermal and post-annealing process assisted by a TiO₂ seed layer. The LTO@CC anode free from polymeric binder and conducting agent exhibited much higher lithium storage capacity and cycling stability than the conventional slurry-processed electrode using the dandelion-like Li₄Ti₅O₁₂ microspheres prepared by the same hydrothermal process. A high specific capacity of 128.8 mA h g^?1 was obtained at a current rate of 30 C (1 C = 175 mA g^?1), and almost negligible capacity loses was observed when the cell was cycled at 10, 20 and 30 C each for 100 cycles. The carbon fiber matrix contributed to Li storage at low current rate, but the LTO nanosheet arrays have played the dominant role on the excellent rate capability. The improved electrochemical performance can be attributed to the synergetic effect between the hierarchical Li₄Ti₅O₁₂ nanosheet arrays and the carbon fiber matrix, which integrated short Li⁺ diffusion length, three-dimensional conductive architecture and well preserved structural integrity during the high rate and repeated charge-discharge measurements.     

The effects of N-methyl-N-butylpyrrolidinium bis(trifluoromethylsulfonyl)imide–based electrolyte on the electrochemical performance of high capacity cathode material Li[Li0.2Mn0.54Ni0.13Co0.13]O2

The effects of ionic liquid (IL) N-methyl-N-butylpyrrolidinium bis(trifluoromethylsulfonyl)imide (Py₁₄TFSI) based electrolyte on the electrochemical performance of cathode material Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂ have been investigated. The results of thermogravimetric analysis (TGA), flammability and differential scanning calorimetry (DSC) tests indicate that Py₁₄TFSI addition enhances thermal stability of the electrolyte and reduces the safety concern of Li-ion battery. Electrochemical measurements demonstrate that the cathode material shows good electrochemical performance in Py₁₄TFSI-added electrolyte. The cathode material is able to deliver high initial discharge capacity of 250 mAh g^?1 in electrolyte with Py₁₄TFSI content up to 80% at 0.1 C. In addition, the cathode material delivers less initial irreversible capacity loss and higher initial coulombic efficiency in electrolyte with higher Py₁₄TFSI content. However, increasing Py₁₄TFSI content in the electrolyte affects rate capability of the cathode material distinctively. With 60% Py₁₄TFSI-added electrolyte, Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂ shows better cycling stability with a capacity retention of 84.4% after 150 cycles at 1.0 C than that in IL free electrolyte. The superior cycling performance of the cathode material cycled in Py₁₄TFSI-added electrolyte is mainly ascribed to the formation of stable electrode/electrolyte interfaces, based on the results of scanning electron microscopy (SEM), X-ray photoelectron spectra (XPS) and electrochemical impedance spectroscopy (EIS) investigations.     

Characterization of IT-SOFC non-symmetrical anode sintered through conventional furnace and microwave

This work investigated the mechanical and electrical properties of NiO–SDC/SDC anode sintered by two different methods: in a microwave at about 1200 °C for 1 h and in a conventional furnace at 1200 °C with a holding time of 1 h (total sintering time of 21 h). Nano-powders Sm_0.2Ce_0.8O_1.9 (SDC) and NiO were mixed using a high-energy ball mill, followed by the co-pressing technique at a compaction pressure of 400 MPa. No binder was used between the layers. The electrical behaviors of all sintered samples were studied using electrochemical impedance spectra in the frequency range of 0.01–10⁵ Hz under 97% H₂–3% H₂O, an amplitude of 10 mV, and at high temperature range of 600–800 °C. Results indicate that the non-symmetrical NiO–SDC/SDC anode achieved through microwave sintering has finer grain size and higher electrochemical performance. However, hardness and Young׳s modulus increased in the samples sintered through a conventional furnace.     

Stabilizing the structure and suppressing the voltage decay of Li[Li0.2Mn0.54Co0.13Ni0.13]O2 cathode materials for Li-ion batteries via multifunctional Pr oxide surface modification

The development of Li-rich layer cathode materials has been limited by poor cycle, rate performance, phase transformation and voltage decay. To improve these properties, a facile and low-cost wet method is employed to fabricate Pr₆O₁₁ coating layer on Li[Li_0.2Mn_0.54Co_0.13Ni_0.13]O₂ nanoparticles. The 3–6 nm Pr₆O₁₁ coating layer is observed on the surface of Li[Li_0.2Mn_0.54Co_0.13Ni_0.13]O₂ by HRTEM. Interestingly, HAADF-STEM and EDS analyses show that the transition metal ions and the praseodymium ions mutually infiltrate in the Pr₆O₁₁ coating layer and Li[Li_0.2Mn_0.54Co_0.13Ni_0.13]O₂ nanoparticles during calcination. A combination of HAADF-STEM with EDS and XPS studies reveals that Pr₆O₁₁ coating layer is bridged to Li[Li_0.2Mn_0.54Co_0.13Ni_0.13]O₂ nanoparticles by the chemical bonds of transition phase Li_1.2M_XPr_1−xO₂. XRD patterns show that all samples are indexed to the layered structure α-NaFeO₂, but the lattice parameters are influenced lightly after Pr₆O₁₁ coating. HRTEM and SAED analyses elucidate that the super large Pr ions surface-doping and the Pr₆O₁₁ coating are verified to suppress the transformation of layer to spinel structure in the bulk nanoparticles after cycles. The sample coated with 3 wt% Pr₆O₁₁ exhibits wonderful electrochemical performance with the first coulomb efficiency of 85.6%, the capacity retention ratio of 97.9% after 50 cycles and the discharge capacity of 162.2 mAh g⁻¹ at 5 C. The resistant of charge transfer and the electrodes polarization are reduced by Pr₆O₁₁ coating according to EIS. Therefore, Pr₆O₁₁, which contains the super large Pr ions, plays two roles: the first one, it is coated on the Li[Li_0.2Mn_0.54Co_0.13Ni_0.13]O₂ nanoparticles to optimize the environment of the interface reaction between electrodes and electrolyte; the other one, its Pr ions surface-doping stabilizes the structure in the superficial region of Li[Li_0.2Mn_0.54Co_0.13Ni_0.13]O₂ nanoparticles and suppresses the voltage decay. The multifunctional Pr₆O₁₁ can play a significant role in accelerating development of new materials with excellent stabilization and high capacity.     

Temperature stability and high-Qf of low temperature firing Mg2SiO4–Li2TiO3 microwave dielectric ceramics

In this work, a series of low-temperature-firing (1−x)Mg₂SiO₄–xLi₂TiO₃–8 wt% LiF (x = 35–85 wt%) microwave dielectric ceramics was prepared through conventional solid state reaction. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses showed that the Li₂TiO₃ phase was transformed into cubic phase LiTiO₂ phase and secondary phase Li₂TiSiO₅. Partial substitution of Mg²⁺ ions for Ti³⁺ ions or Li⁺Ti³⁺ ions increased the cell volume of the LiTiO₂ phase. The dense microstructures were obtained in low Li₂TiO₃ content (x ≤ 65 wt%) samples sintered at 900 °C, whereas the small quantity of pores presented in high Li₂TiO₃ content (x ≥ 75 wt%) samples sintered at 900 °C and low Li₂TiO₃ content (x = 45 wt%) sintered at 850 and 950 °C. Samples at x = 45 wt% under sintering at 900 °C for 4 h showed excellent microwave dielectric properties of ε_r = 10.7, high Q × f = 237,400 GHz and near-zero τ_f = − 3.0 ppm/°C. The ceramic also exhibited excellent chemical compatibility with Ag. Thus, the fabricated material could be a possible candidate for low temperature co-fired ceramic (LTCC) applications.     

Manufacturing a high performance film of CaO-B2O3-SiO2 glass-ceramic powder with surface modification for LTCC application

The present work was oriented to develop a high-performance film for LTCC application through using a kind of silane coupling agent (SCA) to modify the CBS (CaO-B₂O₃-SiO₂) glass-ceramic powders in tape casting process. The coupling mechanism of the silane coupling agent interacting with the powders was illustrated in detail, and the optimum amount of additions was determined by the infrared transmittance and contact angle experiment. The rheological properties of suspensions, the compactness and tensile breaking strength of the green tape were texted by using a number of quantitative and qualitative instruments. Furthermore, when the green tapes sintered at 820 °C, the sintering characteristics and microwave properties of sintered body with different SCA additions was also analyzed. Based on the experimental results, it revealed that the powders modified by SCA with 1.5 wt% additions could induce the most excellent performance of film, with the density at 1.57 g/cm³ and the tensile strength at 2.57 MPa, possessing the highest density and best microwave properties of sintered body: the density of sintered body was 2.48 g/cm³, the dielectric constant and dielectric loss was ε_r = 5.93, tanδ=8 × 10^?4 at 12 Hz.     

Hydrothermal synthesis of spherical Li4Ti5O12 material for a novel durable Li4Ti5O12/LiMn2O4 full lithium ion battery

Pure spherical Li₄Ti₅O₁₂ spinel material is quickly synthesized via an efficient hydrothermal procedure. The obtained Li₄Ti₅O₁₂ particle size is about 0.5 µm. The Li₄Ti₅O₁₂ has an initial discharge capacity of 162.2 mA h g⁻¹ and capacity retention of 97.5% after 100 cycles at a rate of 0.2 C. Then, a 2.5 V and long-lasting Li-ion cell with a LiMn₂O₄ cathode and a Li₄Ti₅O₁₂ anode is developed. Electrochemical measurements of the cell indicate that the Li₄Ti₅O₁₂/LiMn₂O₄ full cell, with a weight ratio of 1.5 between cathode and anode, exhibits excellent electrochemical performance, delivering a reversible capacity of 130 mA h g⁻¹ at room temperature. The full cell also exhibits outstanding electrochemical performances at high temperature, as it has an initial discharge capacity of 109.6 mA h g⁻¹, along with a capacity retention rate of 88.9% after 100 cycles at 55 °C.     

Li2O excess (Na0.51K0.47Li0.02)(Nb0.8Ta0.2)O3 lead free piezoelectric ceramics

1 mol% Li₂O excess (Na_0.51K_0.47Li_0.02)(Nb_0.8Ta_0.2)O₃ ceramics were prepared by the conventional mixed oxide method and sintered from 950 to 1200 °C. Also, Li₂O was employed as a sintering aid for high densification and low temperature sintering process. X-ray diffraction results of 1 mol% Li₂O excess (Na_0.51K_0.47Li_0.02)(Nb_0.8Ta_0.2)O₃ lead free piezoelectric ceramics indicated that the specimens were well crystallized and have tetragonal structure. The specimens which sintered at 1050 °C showed the highest piezoelectric properties compared with others. The measured piezoelectric constant and electromechanical coupling coefficient were 231 pC/N and 38.9%, respectively. Curie temperature of (Na_0.51K_0.47Li_0.02)(Nb_0.8Ta_0.2)O₃ ceramics was 344.32, 344.4 and 344.5 °C at 1, 10 and 100 kHz, respectively.     

A novel low-firing microwave dielectric ceramic Li2ZnGe3O8 with cubic spinel structure

A Li₂ZnGe₃O₈ ceramic was investigated as a promising microwave dielectric material for low-temperature co-fired ceramics applications. Li₂ZnGe₃O₈ ceramic was prepared via the conventional solid-state method. X-ray diffraction data shows that Li₂ZnGe₃O₈ ceramic crystallized into a cubic spinel structure with a space group of P4₁32. Dense ceramic with a relative densities of 96.3% were obtained when sintered at 945 °C for 4 h and exhibited the optimum microwave properties with a relative permittivity (ε_r) of 10.3, a quality factor (Q × f) of 47,400 GHz (at 13.3 GHz), and a temperature coefficient of resonance frequency (τ_f) of −63.9 ppm/°C. The large negative τ_f of Li₂ZnGe₃O₈ ceramic could be compensated by rutile TiO₂, and 0.9Li₂ZnGe₃O₈–0.1TiO₂0·1TiO₂ ceramic sintered at 950 °C for 4 h exhibited improved microwave dielectric properties with a near-zero τ_f of −1.6 ppm/°C along with ε_r of 11.3 and a Q × f of 35,800 GHz (11.6 GHz). Moreover, Li₂ZnGe₃O₈ was found to be chemically compatible with silver electrode when sintered at 945 °C.     

Carbon-coated Li2S cathode for improving the electrochemical properties of an all-solid-state lithium-sulfur battery using Li2S-P2S5 solid electrolyte

Li₂S is coated with carbon to improve the electrical conductivity of the composite cathode in all-solid-state lithium-sulfur batteries. Carbon is applied by thermal evaporation from a polyacrylonitrile (PAN) source at 600 °C for 5 h. It is shown that the carbon coating is impurity free, and the crystallinity of Li₂S is well maintained. The electronic conductivity of Li₂S is dramatically improved from 9.21 × 10^?9 S cm^?1 to 2.39 × 10^?2 S cm^?1 upon carbon coating. An all-solid-state battery prepared with the carbon-coated Li₂S shows a high initial capacity of 585 mAh g^?1 (g of Li₂S) that increases up to 730 mAh g^?1 (g of carbon-coated Li₂S) by the 10th cycle. This high capacity is stable throughout the 25 cycles tested, with an excellent coulombic efficiency of 99%. Carbon-coated Li₂S is advantageous for all-solid-state batteries due to the increased electrical conductivity, while allowing a reduction of the total carbon content present in the composite cathode.     

Effects of Li2CO3 addition on the microstructure and magnetic properties of low-temperature-fired NiCuZn ferrites

NiCuZn ferrites doped with 0.5 wt% Bi₂O₃ and different Li₂CO₃ contents (0–0.25 wt%) were sintered at 900 °C. The microstructure and magnetic properties of these materials were investigated. The addition of low-melting-point Li₂CO₃ led to large and uniform grains. However, excess Li₂CO₃ addition produced abnormal grains and many closed pores, thereby reducing density. Permeability initially increased and then decreased at the Li₂CO₃ content of >0.2 wt%. Maximum magnetic flux density (431.1 mT at room temperature, 339.6 mT at 100 °C) and minimum power loss were achieved at 0.2 wt% Li₂CO₃. These findings suggested the suitability of 0.2 wt% Li₂CO₃ for applications in low-temperature co-fired ceramic magnetic power components and modules.     

Synthesis and electrochemical performance of Li4Ti5O12/C composite by a starch sol assisted method

Li₄Ti₅O₁₂/C composite anode materials were synthesized by a simple starch sol assisted method using TiO₂-anatase and Li₂CO₃ as raw materials and soluble starch as carbon source. The influences of calcination temperature and starch amounts on the microstructure and electrochemical performance were systematically investigated. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and constant-current charge/discharge cycling tests. The results showed that the Li₄Ti₅O₁₂/C composite with 10 wt.% starch synthesized at 800 °C for 6 h had homogeneous particle size distribution with an average particle size of 200–300 nm and exhibited the optimal electrochemical performance with specific discharge capacities of 168.5, 160.8, 155.1 and 141.8 mAh g^? 1 at 0.2 °C, 1 °C, 2 °C and 5 °C rates, respectively, and satisfactory cycling stability. It could be attributed to the homogeneous ultrafine particles and in situ carbon coating, which enhanced the electronic conductivity and diffusion of lithium ions in the electrode.     

Microwave dielectric properties of low-temperature sinterable α-MoO3

The α-MoO₃ ceramics were prepared by uniaxial pressing and sintering of MoO₃ powder at 650 °C and their structure, microstructure, densification and sintering and microwave dielectric properties were investigated. The sintering temperature of α-MoO₃ was optimized based on the best densification and microwave dielectric properties. After sintering at 650 °C the relative permittivity was found to be 6.6 and the quality factor was 41,000 GHz at 11.3 GHz. The full-width half-maximum of the A_1g Raman mode of bulk α-MoO₃ at different sintering temperatures correlated well with the Qf values. Moreover, the sintered samples showed a temperature coefficient of the resonant frequency of ?25 ppm/°C in the temperature range from ?40 to 85 °C and they exhibited a very low coefficient of thermal expansion of ±4 ppm/°C. These microwave dielectric properties of α-MoO₃ will be of great benefit in future MoO₃ based materials and their applications.     

La2O3-coated Li1.2Mn0.54Ni0.13Co0.13O2 as cathode materials with enhanced specific capacity and cycling stability for lithium-ion batteries

Li-rich layered oxides are the most promising cathode candidate for new generation rechargeable lithium-ion batteries. In this work, La₂O₃-coated Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ cathode materials were fabricated via a combined method of sol-gel and wet chemical processes. The structural and morphological characterizations of the materials demonstrate that a thin layer of La₂O₃ is uniformly covered on the surface of Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ particles, and the coating of La₂O₃ has no obvious effect on the crystal structure of Li-rich oxide. The electrochemical performance of La₂O₃-coated Li-rich cathodes including specific capacity, cycling stability and rate capability has been significantly improved with the coating of La₂O₃. The Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ coated with 2.5 wt% La₂O₃ exhibits the highest discharge capacity, improved cycling stability and reduced charge transfer resistance, delivering a large discharge capacity of 276.9 mAh g⁻¹ in the 1st cycle and a high capacity retention of 71% (201.4 mAh g⁻¹) after 100 cycles. The optimal rate capability of the materials is observed at the coating level of 1.5 wt% La₂O₃ such that the material exhibits the highest discharge capacity of 90.2 mAh g⁻¹ at 5 C. The surface coating of La₂O₃ can effectively facilitate Li⁺ interfacial diffusion, reduce the structural change and secondary reactions between cathode materials and electrolyte during the charge-discharge process, and thus induce the great enhancement in the electrochemical properties of the Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ materials.     

Microstructural and microwave dielectric properties of LZT (Li2ZnTi3O8) ceramics sintered in presence of bismuth borate glass for LTCC applications

In the present research, the Li₂ZnTi₃O₈(LZT) ceramics were synthesized throughout solid-state ceramic processing, then mixed with bismuth borate (BiBO) glass prepared based on conventional melt quenching method. Wetting behavior of BiBO glass on the LZT ceramic substrate was monitored by hot stage microscopy. Afterward, dielectric LZT ceramics containing different amounts of BiBO glass (0.25–6 wt%) were sintered at various temperatures. X-ray diffraction and electron back scatter diffraction examinations revealed the presence of two crystalline phases of Li₂ZnTi₃O₈ and Bi₂Ti₂O₇. The maximum value of relative density (above 95%) was obtained in the case of specimens contained more than 5 wt% glass. The microwave dielectric properties of the finally sintered BiBO glass containing LZT ceramics were as follows: dielectric constant (ε_r) = 21.44–25.09, quality factor (Q × f) = 10839–54708 GHz and temperature coefficient of resonant frequency (τ_f) = (? 15.58) ? (? 12.86)ppm/°C.     

Synthesis and electrochemical properties of a composite LiMn0.63Fe0.37PO4 with Li3V2(PO4)3 for lithium-ion battery cathode materials

A composite materials LiMn_0.63Fe_0.37PO₄ with Li₃V₂(PO₄)₃ can be synthesized by a sol-gel method using N,N-dimethylformamide (DMF) as a dispersing agent. The structures, characteristics of the appearance, and electrochemical properties of the composites have been studied by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), charge/discharge tests, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The composites contained LiMnPO₄/C (LMP/C), LiFePO₄/C (LFP/C), and Li₃V₂(PO₄)₃/C (LVP/C) phases with a nano-sized dispersion. The TEM images showed that the composites are crystalline with a grain size of 10–50 nm. The Mn2p, V2p, and Fe2p valence states were analyzed by X-ray photoelectron spectroscopy (XPS). The incorporation of LVP and LFP with LMP effectively enhanced the electrochemical kinetics of the LMP phase by a structural modification and shortened the lithium diffusion length in LMP. The capacity of the composite 0.79LiMn_0.63Fe_0.37PO₄·0.21Li₃V₂(PO₄)₃/C remained at 152.3 mAh g⁻¹ (94.7%) after 50 cycles at a 0.05 C rate. The composite exhibited excellent reversible capacities 159.4, 150, 140.1, 133.7 and 123.6 mAh g⁻¹ at charge-discharge rates of 0.05, 0.1, 0.2, 0.5 and 1 C, respectively.     

Texturing behaviours of (K0.47Na0.51Li0.02)(Nb0.8Ta0.2)O3 piezoelectric ceramics produced using NaNb1-xTaxO3 templates

Textured (K_0.47Na_0.51Li_0.02)(Nb_0.8Ta_0.2)O₃ (KNLNT20) piezoelectric ceramics were prepared using NaNb_1?xTa_xO₃ templates. The highest degree of grain orientation (97%) and piezoelectric constant (342 pC/N) were obtained upon adding 3 wt% of the NaNb_0.8Ta_0.2O₃ (NNT20) template and sintering at 1150 °C for 1 h. Back-scattered scanning electron micrographs of the textured KNLNT20 samples sintered at 1150 °C for 1 h indicated the presence of templates similar in size to the original ones within the cores of the textured grains. The peak value of the dielectric constant corresponding to the NNT20 core decreased after prolonged holding at 1150 °C, owing to a decrease in the size of the NNT20 core because of the interdiffusion of K, Na, and Li ions between the NNT20 core and KNLNT20 shell. This interdiffusion also decreased the piezoelectric constant, d₃₃ value of the textured KNLNT20 samples by inducing a change in the chemical composition of the shell region.