Li2ZrO3 based Li-ion conductors doped with halide ions & sintered in oxygen-deficient atmosphere

All-solid-state batteries have recently attracted much attention for their high energy density and safety. Li₂ZrO₃-based Li-ion conductors with high electrochemical stability have potential applications for electrolytes in all-solid-state batteries. In this work, comparative investigations of Li₂ZrO₃ and halogen doped Li₂ZrO₃ ceramics were conducted by sintering at 700 °C in air or in oxygen-deficient atmosphere which was induced by a simple setup covering with corundum crucible. The analysis of phase composition reveals that the undoped Li₂ZrO₃ ceramic sintered in air contains pure monoclinic phase, while halogen-doped Li₂ZrO₃ sintered in air and all ceramics sintered in oxygen-deficient atmosphere are simultaneously composed of monoclinic and tetragonal phases. Li₂ZrO₃ ceramic with tetragonal phases has higher conductivity (0.28 mS cm⁻¹ for undoped Li₂ZrO₃) than the pure monoclinic Li₂ZrO₃ (0.07 mS cm⁻¹), and halogen doping can further enhance the conductivity of Li₂ZrO₃ ceramics higher than 0.5 mS cm⁻¹ at room temperature.     

High Li-ion conductivity of Al-doped Li7La3Zr2O12 synthesized by solid-state reaction

Li₇La₃Zr₂O₁₂ (LLZO) has cubic garnet type structure and is a promising solid electrolyte for next-generation Li-ion batteries. In this work, Al-doped LLZO was prepared via conventional solid-state reaction. The effects of sintering temperature and Al doping content on the structure and Li-ion conductivity of LLZO were investigated. The phase composition of the products was confirmed to be cubic LLZO via XRD. The morphology and chemical composition of calcined powders were investigated with SEM, EDS, and TEM. The Li-ion conductivity was measured by AC impedance. The results indicated the optimum sintering temperature range is 800–950 °C, the appropriate molar ratio of LiOH·H₂O, La(OH)₃, ZrO₂ and Al₂O₃ is 7.7:3:2:(0.2–0.4), and the Li-ion conductivity of LLZO sintered at 900 °C with 0.3 mol of Al-doped was 2.11×10⁻⁴ S cm⁻¹ at 25 °C.     

Phase transformation and grain-boundary segregation in Al-Doped Li7La3Zr2O12 ceramics

Cubic phase garnet-type Li₇La₃Zr₂O₁₂ (LLZO) is a promising solid electrolyte for highly safe Li-ion batteries. Al-doped LLZO (Al-LLZO) has been widely studied due to the low cost of Al₂O₃. The reported ionic conductivities were variable due to the complicated Al³⁺-Li⁺ substitution and Li_xAlO_y segregation in Al-LLZO ceramics. This work prepared Li_7?3xAl_xLa₃Zr₂O₁₂ (x = 0.00~0.40) ceramics via a conventional solid-state reaction method. The AC impedance and corresponding distribution of relaxation times (DRT) were analyzed combined with phase transformation, cross-sectional microstructure evolution, and grain boundary element mapping results for these Al-LLZO ceramics to understand the various ionic transportation levels in LLZO with different Al-doping amounts. The low conductivity in low Al-doped (0.12~0.28) LLZO originates from the slow Li⁺ ion migration (1.4~0.25 μs) in the cubic-tetragonal mixed phase. On the other hand, LiAlO₂ and LaAlO₃ segregation occur at the grain boundaries of high Al-doped (0.40) LLZO, resulting in a gradual Li⁺ ion jump (6.5 μs) over grain boundaries and low ionic conductivity. The Li_6.04Al_0.32La₃Zr₂O₁₂ ceramic delivers the optimum Li⁺ ion conductivity of 1.7 × 10^?4 S cm^?1 at 25 °C.     

Influence of the cold sintering process and post annealing on the microstructure and Li-ion conductivity of LiTa2PO8 solid electrolyte

Recently, LiTa₂PO₈ (LTPO) has attracted interest as a potential Li-ion solid electrolyte material because of its high bulk ionic conductivity and low grain boundary ionic conductivity. However, most ceramic-based solid electrolytes are fabricated via the high-temperature sintering process (typically above 1000 °C); such temperatures can cause the evaporation of Li from the compound. To replace high-temperature sintering of ceramics, the cold sintering process (CSP) was introduced; this process enables the densification of ceramics and composites at extremely low temperatures (below 300 °C). In this work, we investigate the effect of using the CSP and post annealing on the microstructure and Li-ion conductivity of LTPO pellets. It is found that the CSP pellets have an amorphous phase between particles. This intermediate amorphous phase creates a better contact between particles and is hypothesized to lead to more Li-ion migration paths. The CSP pellet is found to have a high density and high ionic conductivity of (1.19 × 10^?5 S/cm). The pellet obtained via the CSP has Li-ion conductivity similar to that of the pellet obtained via dry pressing after it has been annealed. The CSP pellet after post annealing shows good connections between particles and a high Li-ion conductivity of 1.05 × 10^?4 S/cm, which is comparable to the conductivity of a pellet obtained via high-temperature sintering. This work provides new evidence that the CSP is a promising alternative to high-temperature sintering for fabricating ceramic solid electrolytes.     

Porous ceramics based on high-thermal-stability Al2O3–ZrO2 nanofibers for thermal insulation and sound absorption applications

Al₂O₃ fibers are promising candidates for porous ceramics, but the sudden growth of grains in the fibers above 1200 °C will limit their applications for high temperature. Herein, we reported the successful fabrication of the Al₂O₃–ZrO₂ nanofibers by electrospinning and the nanofiber-based porous ceramics by a combination of gel-casting, freeze-drying and high-temperature sintering. Results show that the addition of Zr could greatly improve the thermal stability (up to 1400 °C) of the Al₂O₃-based nanofibers, owing to the inhibition of the sudden growth of the grains in the fibers at high temperature. The Al₂O₃–ZrO₂ nanofiber-based porous ceramics after sintering at 1100–1400 °C possessed a multi-level pore structure and exhibited high thermal stability, ultra-high porosity (97.79–98.04%), ultra-low density (0.075–0.091 g/cm³) and thermal conductivity (0.0474–0.0554 W/mK), and excellent sound absorption performance with the average sound absorption coefficient of 0.598–0.770. These porous ceramics are expected to be employed in the fields of high-temperature thermal insulation and sound absorption.     

Lithium mobility along conduction channels of ceramic LiTa2PO8

In the next generation of lithium-ion batteries, the liquid electrolyte is considered to be replaced by its solid counterpart. Recently, a novel Li-ion conductor based on metal oxides emerged – LiTa₂PO₈. Due to the high value of bulk conductivity of ca. 10⁻³ S∙cm⁻¹, it is believed to be a potential candidate for application as a solid electrolyte in all-solid-state battery technology. In this work, we investigate LiTa₂PO₈ ceramics synthesized by a conventional solid-state reaction method with an excess of the lithium-containing substrate to compensate for the loss of Li⁺ during sintering. The properties of LiTa₂PO₈ ceramics were studied using X-ray diffractometry (XRD), ⁶Li and ³¹P magic angle spinning nuclear magnetic resonance spectroscopy (MAS NMR), thermogravimetry (TG), scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS), impedance spectroscopy (IS), DC potentiostatic polarization technique and density method. Referring to the experimental results, increasing of the Li⁺ content above the stoichiometric one lowers the total ionic conductivity. The reasons for the deterioration and correlations between microstructure, phase composition, and ionic conductivity are presented and discussed. The MAS NMR spectroscopy has been used to explain high bulk ionic conductivity of LiTa₂PO₈ ceramics. A maximum value of total ionic conductivity, 4.5 × 10⁻⁴ S∙cm⁻¹, was obtained at room temperature for the sample without any excess of Li⁺ source.     

High densification and Li-ion conductivity of Al-free Li7-xLa3Zr2-xTaxO12 garnet solid electrolyte prepared by using ultrafine powders

Ta-doped Li₇La₃Zr₂O₁₂ (Ta-LLZO) is considered as a promising solid electrolyte due to high Li-ion conductivity and good chemical stability against electrode materials. In this work, Ta-LLZO was prepared by a conventional solid-state reaction. Ultrafine powders were obtained by ball-milling to improve the surface activity. Ta-LLZO is sintered in ZrO₂ crucibles to avoid introducing Al into the samples. The particle size distribution, phase structure, morphology, ionic conductivity, electronic conductivity, density and electrochemical performance of semi-solid battery were characterized by laser diffraction particle size analyzer, X-ray diffraction, scanning electron microscope, AC-impedance, DC polarization, Archimedes method and a battery testing system, respectively. The results show that the ball milling to reduce the particle size is an effective way to solve the problem of relatively low density and Li-ion conductivity for Al-free Li_7-xLa₃Zr_2-xTa_xO₁₂. For Al-free Li_7-xLa₃Zr_2-xTa_xO₁₂, the increase of x (0.2?≤?x?≤?0.4) promotes the grain growth and sintering densification, but the increase of x (0.4?<?x?≤?0.6) has an adverse effect. Li_6.7La₃Zr_1.7Ta_0.3O₁₂ sintered at 1180?°C for 12?h shows the relative density of 92% and the highest Li-ion conductivity of 1.03?×?10^?3 S/cm at ³0?°C with the activation energy of about 0.37?eV, while Li_6.6La₃Zr_1.6Ta_0.4O₁₂ sintered at 1180?°C for 12?h shows the highest relative density of 96% and the Li-ion conductivity of 6.68?×?10^?4 S/cm at 30?°C with the activation energy of about 0.46?eV. The electronic conductivity of Al-free Li_7-xLa₃Zr_2-xTa_xO₁₂ is 10^?9 S/cm orders of magnitude. The semi-solid battery shows the first discharge capacity of 104.6 mAh/g and 92.5% capacity retention after 20 cycles.     

Sintering,micro-structure and Li+ conductivity of Li7−xLa3Zr2−xNbxO12/MgO (x = 0.2–0.7) Li-Garnet composite ceramics

Nb-doped Li₇La₃Zr₂O₁₂ (Nb-LLZO) is one of the promising electrolyte candidates in the Li-Garnet family due to its high Li-ion conductivity. The sintered Nb-LLZO ceramics, however, often exhibit abnormal grain growth with high porosity and poor mechanical properties. For advantaged electrochemical and mechanical properties, a uniform and dense microstructure is desired. In this research, MgO has been added as a secondary phase to inhibit abnormal grain growth in Nb-LLZO. The sintering process of the Nb-LLZO/MgO composite ceramics has been studied for different Nb doping levels (0.2–0.7 pfu) at sintering conditions of 1250?°C for 1–360?min. The ceramic density, microstructure, and Li-ion conductivity are reported. The composite ceramics have shown a very fast sintering speed. At 1250?°C, the 0.4Nb-LLZO/MgO composite can be well-sintered in 1?min. For sintering at 1250?°C for 40?min, ceramic samples showing relative density of 97%, conductivity of 6?×?10^?4 S?cm^?1 at 25?°C, and activation energy of 0.40?eV are obtained.     

Effect of the crystalline layer on the electrical behaviour of 17.7Li2O·5.2ZrO2·68.1SiO2·9.0Al2O3 glass ceramic monoliths

Li₂O–ZrO₂–SiO₂–Al₂O₃ (LZSA) glass ceramic systems are usually obtained from powder technology to obtain materials with a low thermal expansion coefficient (CTE). However, in these cases, there is a high residual porosity. An alternative to reduce the porosity involves the production of monoliths. Nevertheless, there is still a lack of crystallisation kinetics and the final properties of glass ceramic monoliths are affected such as electrical properties. This study aims to evaluate the electrical behaviour as function of the crystalline layer thickness formed on the monolith surface of a 17.7Li₂O·5.2ZrO₂·68.1SiO₂·9.0Al₂O₃ (molar basis) glass ceramic LZSA composition. Monoliths thermally treated at 750, 800, and 850 °C were chosen to evaluate based on the range of the crystalline layer growth. Electrochemical impedance spectroscopy was used for the electrical characterisation of LZSA glass and the glass ceramics. The resistivity increased with increasing thermal treatment temperature due to the formation of lithium-based crystalline phases. The electrical conductivity at 25 °C of the glass ceramic thermally treated at 850 °C decreased to 1.4 × 10^?13 S cm^?1 from 8.7 × 10^?11 S cm^?1 for LZSA glass. Based on the electrical behaviour, monoliths thermally treated at 850 °C can be considered potential for dielectric industrial applications.     

Phase evolution,structure, and electrochemical performance of Al-, Ga- and Ta- substituted Li7La3Zr2O12 ceramic electrolytes by a modified wet chemical route

Garnet-type Li₇La₃Zr₂O₁₂ (LLZO) is one of the most promising solid-state electrolytes (SSEs) for advanced solid-state lithium batteries (SSLBs). In this work, Li_6.25Al_0.25La₃Zr₂O₁₂, Li_6.4Ga_0.2La₃Zr₂O₁₂, and Li_6.4La₃Zr_1.4Ta_0.6O₁₂ ceramics are prepared by a modified wet chemical route. The composition of the black mixtures derived from the precursors is ascertained. The phase evolution and structural properties from the ceramic mother powders to the final ceramic electrolytes are discussed in detail. The characteristic of cubic LLZO with the space group I-43d arises in the Li_6.4Ga_0.2La₃Zr₂O₁₂ ceramic electrolyte pellet after the secondary higher-temperature (1200 °C) sintering. The Rietveld refinement reveals the roles of Al³⁺ substitution at the Li⁺ sites and Ta⁵⁺ substitution at the Zr⁴⁺ sites to adjust crystal structure. In addition, the electrochemical performance of the ceramic pellets is also investigated. Remarkably, the Li_6.4La₃Zr_1.4Ta_0.6O₁₂ ceramic electrolyte has the most outstanding electrochemical performance, showing the high ionic conductivity of 6.88 × 10^?4 S cm^?1 (25 °C), the low activation energy of 0.42 eV and an extremely low electronic conductivity of 1.77 × 10^?8 S cm^?1 (25 °C). Overall, it is supposed that this work may help to achieve high-quality modified LLZO ceramic electrolytes, especially using the wet chemical strategy.     

Synthesis of Ga-doped Li7La3Zr2O12 solid electrolyte with high Li+ ion conductivity

Garnet-type Li₇La₃Zr₂O₁₂ (LLZO) Li⁺ ion solid electrolyte is a promising candidate for next generation high-safety solid-state batteries. Ga-doped LLZO exhibits excellent Li⁺ ion conductivity, higher than 1 × 10^?3 S cm^?1. In this research, the doping amount of Ga, the calcination temperature of Ga-LLZO primary powders, the sintering conditions and the evolution of grains are explored to demonstrate the optimum parameters to obtain a highly conductive ceramics reproducibly via conventional solid-state reaction methods under ambient air sintering atmosphere. Cubic LLZO phase is obtained for Li_6.4Ga_0.2La₃Zr₂O₁₂ powder calcined at low temperature 850 °C. In addition, ceramic pellets sintered at 1100 °C for 320 min using this powder have relative densities higher than 94% and conductivities higher than 1.2 × 10^?3 S cm^?1 at 25 °C.     

Nonstoichiometry and Li‐ion transport in lithium zirconate: The role of oxygen vacancies

Understanding Li‐ion migration mechanisms and enhancing Li‐ion transport in Li₂ZrO₃ (LZO) is important to its role as solid absorbent for reversible CO₂ capture at elevated temperatures, as ceramic breeder in nuclear reactors, and as electrode coating in high‐voltage lithium‐ion batteries (LIBs). Although defect engineering is an effective way to tune the properties of ceramics, the defect structure of LZO is largely unknown. This study reports the defect structure and electrical properties of undoped LZO and a series of cation‐doped LZOs: (i) depending on their charge states, cation dopants can control the oxygen vacancy concentration in doped LZOs; (ii) the doped LZOs with higher oxygen vacancy concentrations exhibit better Li⁺ conductivity, and consequently faster high‐temperature CO₂ absorption. In fact, the Fe (II)‐doped LZO shows the highest Li‐ion conductivity reported for LZOs, reaching 3.3 mS/cm at ~300°C that is more than 1 order of magnitude higher than that of the undoped LZO.     

Enhanced “overall” ionic conductivity in Li1+xAlxTi2−x(PO4)3 (0.3 ≤ x ≤ 0.7) ceramics prepared from sol-gel powders by spark plasma sintering

The Li_1+xAl_xTi_2?x(PO₄)₃ (LATPx) series displays the highest “bulk” reported conductivity, but a much lower “overall” contribution, that changes with the powder preparation and sintering conditions. In this work, the preparation of LATPx ceramics is discussed, by using the sol-gel technique for powders synthesis and mild spark plasma (SPS) for ceramics sintering at 800 °C. An “overall” conductivity ~ 2.10^?3 Ω^?1 cm^?1 was obtained for the x = 0.4 composition, that was the result of a high “bulk” conductivity, an optimized microstructure and almost full density, in absence of micro-cracks, with a small content of secondary phases and clean grain boundaries. Fast-ion ceramics prepared by SPS are good candidates for solid electrolytes in all solid state batteries (ASSB).     

Achieving enhanced densification and superior ionic conductivity of garnet electrolytes via a co-doping strategy coupled with pressureless sintering

Lithium garnet oxides with 6.5 mol Li, such as Li_6.5La₃Zr_1.5(Ta/Nb)_0.5O₁₂, typically crystallise in cubic structure and exhibit excellent room-temperature ionic conductivity close to 1 mS cm^?1. However, it is challenging to densify garnet oxides. In this work, we investigated how the co-doping of tantalum (Ta) and niobium (Nb) affects the densification of pressureless sintered garnet electrolytes with compositions of Li_6.5La₃Zr_1.5Ta_(0.5?x)Nb_xO₁₂, where x = 0–0.5. The highest densification (94.5% of relative density) was achieved in Li_6.5La₃Zr_1.5Ta_0.1Nb_0.4O₁₂ (TN-LLZO) when it was sintered at 1150 °C for 6 h. This TN-LLZO garnet electrolyte delivers an ionic conductivity of 1.04 × 10^?3 S cm^?1 (at 22 °C) with a low activation energy of 0.41 eV. Our findings demonstrate that the content of dopants (Ta and Nb) plays a critical role in enhancing the sintering performance of garnet ceramics at ambient pressure.     

Fast Li-ion conductor Li1+yTi2-yAly(PO4)3 modified Li1.2[Mn0.54Ni0.13Co0.13]O2 as high performance cathode material for Li-ion battery

In the material of xLi₂MnO₃ ·(1-x) LiMO₂ (0 < x < 1), the Li₂MnO₃ component is used to stabilize the layered LiMO₂ structure. However, the electrochemical inactive Li₂MnO₃ makes Li-ion diffusion difficult, leading to a sluggish rate capability. In this work, Li_1.3Ti_1.7Al_0.3(PO₄)₃ (LTA0.3), a NASICON-type Li-ion conductor, is applied to modified Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ to overcome the above shortcoming. Additionally, the Li-ion conductivity of LiTi₂(PO₄)₃ can be improved effectively by replacing tetravalent cation Ti⁴⁺ with trivalent Al³⁺ at the optimal ratio. At 1C rate, the LR cathode with 3 wt% LTA0.3 delivers 200 mAh g^?1 after 170 cycles and maintains 140 mAh g^?1 after 500 cycles. Moreover, the modified cathode shows an enhanced rate performance of 169.7 mAh g^?1 at 5C. Enhanced cycle durability and rate capability are aroused by the 3D skeletal framework of LTA0.3, which is suitable for Li-ion diffusion. The LTA0.3 coating layer displays a robust shell which not only avoids the corrosion of electrode materials but also effectively facilitates Li-ion diffusion.     

ZrO2 and MxOy (M= La,Ce, and Nb) synergistically reinforced porous cordierite ceramics synthesized via a facile solid-state reaction

In an attempt to enhance the sintering and mechanical performance of porous cordierite ceramics (Mg₂Al₄Si₅O₁₈) as support materials for vehicle exhaust catalysts, ZrO₂ and M_xO_y (M = La, Ce, and Nb) were simultaneously introduced into cordierite sintered at 1350 °C for 4 h. Then, the reinforced function of ZrO₂ and M_xO_y on the properties of porous cordierite ceramics was systematically evaluated, especially for the sample co-doped with ZrO₂ and La₂O₃. The results displayed a distinct enhancement in mechanical and thermal performance, and the cold compressive strength increased from 72.74 to 158.59 MPa as well as thermal conductivity ranged from 1.66 to 2.01 W m^?1 K^?1, respectively. It is found that ZrO₂ facilitated activation sintering introduced via lattice distortion in cordierite and La₂O₃ accelerated the formation of cordierite and ZrSiO₄ microcrystalline through the low-temperature liquid phase. The synergic effect between ZrO₂ and La₂O₃, therefore, had a significant role in the reinforced mechanical and thermal performance of porous cordierite ceramics. This work not only offers a feasible strengthening strategy, but also expands the possibilities for building high-performance structural and functional ceramics.     

Structure and microwave dielectric properties of Li(Al1-xLix)SiO4-x ceramics

Li(Al_1-xLi_x)SiO_4-x (x = 0.005, 0.01, 0.015, and 0.02) ceramics were synthesized via a traditional solid phase reaction method with different sintering temperatures. To determine the positions occupied by Li⁺ in the lattice, the defect formation energies and total energies of various sites of LiAlSiO₄ (LAS) occupied by Li⁺ were examined, and the energy of LAS systems were calculated using density functional theory of first-principle with the CASTEP module. The results demonstrated that the Al-sites occupied by Li⁺ had the lowest formation energies and total energy, so Li ⁺ should substitute Al³⁺. The impacts of replacing Al³⁺ with Li⁺ on the bulk density, sintering properties, phase composition, microstructure, and microwave dielectric properties of Li(Al_1-xLi_x)SiO_4-x (0 = x ≤ 0.02) ceramics were thoroughly studied. With Li⁺-doping, the sintering temperature decreased from 1300 °C (x = 0) to 1175 °C (x = 0.02), while the Q × f and τ_f values of LAS ceramics significantly increased. The Li(Al_0.99Li_0.01)SiO_3.99 ceramic was fully sintered at 1250 °C for 10 h to obtain excellent microwave dielectric properties: ε_r = 3.49, Q × f = 51,358 GHz, and τ_f = ?51.48 × 10^?6 °C^?1.     

Stable composite electrolytes of PVDF modified by inorganic particles for solid-state lithium batteries

Polymer electrolytes have been attracting much attention because of their flexibility and easy follow-up processing, but their Li⁺ conductivity in lithium-metal batteries (LIBs) is unsatisfactory. Stable composite electrolytes of poly (vinylidene fluoride) (PVDF) polymer with high lithium-ion conductivity have been prepared by a trigger structural modification of Li_6.5La₃Zr_1.5Nb_0.25Ta_0.25O₁₂ (LLZNTO) garnet ceramic and TiO₂ oxide. The influences of various amounts of TiO₂ and LLZNTO on electrochemical performance were systematically examined. These composite electrolytes exhibited maximal Li⁺ conductivity of 2.89 × 10⁻⁴ S cm⁻¹, which is consistent with the value of pure ceramic electrolytes. Furthermore, it possessed the stable long-term Li cycling and the wide electrochemical window, involving repeated Li plating/stripping at 0.2 mA cm⁻² over 280 h without failure. The discharge specific capacity and Coulomb efficiency for all-solid-state LIBs assembled with these membranes delivered outstanding cycling stability with high discharge capacities (117.9 mA h g⁻¹) at 0.1 C rate and Coulomb efficiency reached 99.9% after 25 cycles. The high Li⁺ conduction capability can be ascribed function of introducing TiO₂ and LLZNTO to restrain tremendously the crystalline behavior of the polymer. Furthermore, the LLZNTO can be complex with PVDF for dehydrofluorination, and it can also offer a burst transportation route for lithium ions. This system might serve as an attractive use for polymer solid electrolytes and open up new possibilities for safe all-solid-state LIBs.     

A low-sintering temperature microwave dielectric ceramic for 5G LTCC applications with ultralow loss

In next-generation mobile and wireless communication systems, low sintering temperature and excellent dielectric properties are synergistic objectives in the application of dielectric resonators/filters. In this work, Li₂Ti_0·98Mg_0·02O_2·96F_0.04–1 wt% Nb₂O₅ (LTMN) ceramics were fabricated, and their sintering temperature was successfully lowered from 1120 °C to 750 °C by adjusting the mass ratio of B₂O₃–CuO (BC) additive. The optimum dielectric properties (ԑ_r ~ 24.44, Q × f ~ 60,574 GHz and τ_f ~ 22.8 ppm/°C) were obtained in BC-modified LTMN ceramics sintered at 790 °C. Even if their sintering temperature was lowered to 750 °C, the lowest temperature among the Li₂TiO₃-based dielectric ceramics currently used for LTCC technology, excellent dielectric properties (ԑ_r ~ 23.77, Q × f ~ 51,636 GHz) were still maintained. Additionally, no extra impurity phase was detected in BC-modified LTMN ceramics co-fired with Ag at 790 °C, indicating that BC-modified LTMN ceramics have a bright prospect in high-performance LTCC devices for 5G applications.     

Synthesis and electrochemical performance of LiVOPO4–Li3V2(PO4)3 cathode materials for lithium ion batteries

Lithium-ion batteries (LIBs) present the advantages of long cycle life, high voltage, and energy density and are widely made in the field of energy storage. LiVOPO₄ (LVOP), a cathode material used in LIBs, has a high conceptual capacity of 159 mAh g⁻¹ and high operating voltage of 3.9 V. However, its low electrical conductivity and cycle performance limit its commercial applications. According to the X-ray diffraction results, orthogonal crystal LVOP and monoclinic crystal Li₃V₂(PO₄)₃ (LVP) coexisted in the synthesised composite material. The transmission electron microscopy results also indicated that the LVOP and LVP phases coexist, which were coated by carbon layer of about 2.5 nm. The discharge of LVOP–LVP composite material initially was 143.2 mAh g⁻¹, and that after 120 cycles was 132.2 mAh g⁻¹ (at 0.1 C and 3–4.5 V). Thus, the electronic conductivity and first discharge specific capacity of the material enhanced due to the introduction of fast ion conductor LVP into LVOP. Electrochemical performance improved because the introduction of LVP led to an increase in Li⁺ pervasion channels in the original material and the acceleration of the Li⁺ transmission speed.