Studies on structural and electrical properties of Mg<Subscript>0. 5+y</Subscript> (Zr<Subscript>2-y</Subscript>Fe<Subscript>y</Subscript>) <Subscript>2</Subscript> (PO<Subscript>4</Subscript>) <Subscript>3</Subscript> ceramic electrolytes

The sample of Mg_{0. 5+y} (Zr_1-y Fe_y) ₂ (PO₄) ₃ (0.0 ≤y ≤0.5) was synthesized using the sol-gel method. The structures of the samples were investigated using X-ray diffraction and Fourier transform infrared spectroscopy measurement. XRD studies showed that samples had a monoclinic structure which was iso-structured with the parent compound, Mg_0.5Zr (PO₄) ₃. The complex impedance spectroscopy was carried out in the frequency range 1–6 MHz and temperature range 303 to 773 K to study the electrical properties of the electrolytes. The substitutions of Fe³⁺ with Zr⁴⁺ in the Mg_0.5Zr (PO₄) ₃ structure was introduced as an extrainterstitial Mg²⁺ ion in the modified structured. The compound of Mg_0.5+y (Zr_1-y Fe_y)₂(PO₄)₃ with y?=?0.4 gives a maximum conductivity value of 1.25?×?10^?5 S cm^?1 at room temperature and 7.18?×?10^?5 S cm^?1 at 773 K. Charge carrier concentration, mobile ion concentration, and ion hopping rate are calculated by fitting the conductance spectra to power law variation, σ _ac (ω)?=?σ _o ? +?Aω ^α . The charge carrier concentration and mobile ion concentration increases with increase of Fe³⁺ inclusion. This implies the increase in conductivity of the compounds was due to extra interstitial Mg²⁺ ions.     

Hydrothermal synthesis of pure LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript> from nanostructured MnO<Subscript>2</Subscript> precursors for aqueous hybrid supercapacitors

Pure LiMn₂O₄ samples with high crystallinity (LMO-1# and LMO-2#) were successfully synthesized by a facile hydrothermal method using δ-MnO₂ nanoflowers and α-MnO₂ nanowires as the precursors. The as-prepared samples were analyzed by XRD, SEM, and Brunauer-Emmett-Teller (BET), and their capacitive properties were investigated by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge/discharge test. Two LiMn₂O₄ samples showed good capacitive behavior in aqueous hybrid supercapacitors. AC//LMO-1# and AC//LMO-2# delivered the initial specific capacitance of 45.4 and 40.7 F g^?1 in 1 M Li₂SO₄ electrolyte at a current density of 200 mA g^?1 in the potential range of 0～1.5 V, respectively. After 1000 cycles, the capacitance retention was 97.6% for AC//LMO-1# and 93.7% for AC//LMO-2#. Obviously, LMO-1# from δ-MnO₂ nanoflowers exhibited higher specific capacitance and better cycling performance than LMO-2#, so LMO-1# was more suitable as the positive electrode material in hybrid supercapacitors.     

Acacia gum-assisted co-precipitating synthesis of LiNi<Subscript>0.5</Subscript>Co<Subscript>0.2</Subscript>Mn<Subscript>0.3</Subscript>O<Subscript>2</Subscript> cathode material for lithium ion batteries

LiNi_0.5Co_0.2Mn_0.3O₂ particles of uniform size were prepared through carbonate co-precipitation method with acacia gum. The precursor of carbonate mixture was calcined at 800 °C, and a well-crystallized Ni-rich layered oxide was got. The phase structure and morphology were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The micro-sized particles delivered high initial discharge capacity of 164.3 mA h g^?1 at 0.5 C (1 C?=?200 mA g^?1) between 2.5 and 4.3 V with capacity retention of 87.5 % after 100 cycles. High reversible discharge capacities of 172.4 and 131.4 mA h g^?1 were obtained at current density of 0.1 and 5 C, respectively. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were performed to further study the LiNi_0.5Co_0.2Mn_0.3O₂ particles. Anyway, the excellent electrochemical performances of LiNi_0.5Co_0.2Mn_0.3O₂ sample should be attributed to the use of acacia gum.     

Structure,thermal behavior,and dielectric properties of new cesium hydrogen sulfate arsenate: Cs<Subscript>2</Subscript>(HSO<Subscript>4</Subscript>)(H<Subscript>2</Subscript>AsO<Subscript>4</Subscript>)

Synthesis and structural characterization by single-crystal X-ray diffraction method, thermal behavior, and electrical proprieties are given for a new compound with a superprotonic phase transition Cs₂(HSO₄)(H₂AsO₄). The title compound crystallizes in the monoclinic system with the P2₁/n space group. The structure contains zigzag chains of hydrogen-bonded anion tetrahedra that extend in the [010] direction. Each tetrahedron is additionally linked to a tetrahedron neighboring chain to give a planar structure with hydrogen-bonded sheets lying parallel to (10ī). The existence of O–H and (S/As)–O bonds in the structure at room temperature has been confirmed by IR and Raman spectroscopy in the frequency ranges 4000–400 cm^?1and 1200–50 cm^?1, respectively. Differential scanning calorimetry analysis of the superprotonic transition in Cs₂(HSO₄)(H₂AsO₄) showed that the transformation to high temperature phase occurs at 417 K by one-step process. Thermal decomposition of the product takes place at much higher temperatures, with an onset of approximately 534 K. The superprotonic transition was also studied by impedance and modulus spectroscopy techniques. The conductivity in the high temperature phase at 423 K is 1.58 × 10^?4 Ω^?1 cm^?1, and the activation energy for the proton transport is 0.28 eV. The conductivity relaxation parameters associated with the high disorder protonic conduction have been examined from analysis of the M”/M”_max spectrum measured in a wide temperature range. Transport properties of this material appear to be due to the proton hopping mechanism.     

Conductivity and spectroscopic studies of Li<Subscript>2</Subscript>O-V<Subscript>2</Subscript>O<Subscript>5</Subscript>-B<Subscript>2</Subscript>O<Subscript>3</Subscript> glasses

Lithium vanadium-borate glasses with the composition of 0.3Li₂O–(0.7-x)B₂O₃–xV₂O₅ (x?=?0.3, 0.325, 0.35, 0.375, 0.4, 0.425, 0.45, and 0.475) were prepared by melt-quenching method. According to differential scanning calorimetry data, vanadium oxide acts as both glass former and glass modifier, since the thermal stability of glasses decreases with an increase in V₂O₅ concentration. Fourier transform infrared spectroscopy data show that the vibrations of [VO₄] structural units occur at V₂O₅ concentration of 45 mol%. It is established that the concentration of V⁴⁺ ions increases exponentially with the growth of vanadium oxide concentration. Direct and alternative current measurements are carried out to estimate the contribution both electronic and ionic conductivities to the value of total conductivity. It is shown that the electronic conductivity is predominant in the total one. The glass having the composition of 0.3Li₂O-0.275B₂O₃-0.475V₂O₅ shows the highest electrical conductivity that has the value of 7.4?×?10^?5 S cm^?1 at room temperature.     

Synthesis and electrochemical properties of P2-Na<Subscript>2/3</Subscript>Ni<Subscript>1/3</Subscript>Mn<Subscript>2/3</Subscript>O<Subscript>2</Subscript>

The pure phase P2-Na_2/3Ni_1/3Mn_2/3O₂ was synthesized by a solid reaction process. The optimum calcination temperature was 850 °C. The as-prepared product delivered a capacity of 158 mAh g^?1 in the voltage range of 2–4.5 V, and there was a phase transition from P2 to O2 at about 4.2 V in the charge process. The P2 phase exhibited excellent intercalation behavior of Na ions. The reversible capacity is about 88.5 mAh g^?1 at 0.1 C in the voltage range of 2–4 V at room temperature. At an elevated temperature of 55 °C, it could remain as an excellent capacity retention at low current rates. The P2-Na_2/3Ni_1/3Mn_2/3O₂ is a potential cathode material for sodium-ion batteries.     

Electrochemical comparison of LiFe<Subscript>0.4</Subscript>Mn<Subscript>0.595</Subscript>Cr<Subscript>0.005</Subscript>PO<Subscript>4</Subscript>/C and LiMnPO<Subscript>4</Subscript>/C cathode materials

A comparison of electrochemical performance between LiFe_0.4Mn_0.595Cr_0.005PO₄/C and LiMnPO₄/C cathode materials was conducted in this paper. The cathode samples were synthesized by a nano-milling-assisted solid-state process using caramel as carbon sources. The prepared samples were investigated by XRD, SEM, TEM, energy-dispersive X-ray spectroscopy (EDAX), powder conductivity test (PCT), carbon-sulfur analysis, electrochemical impedance spectroscopy (EIS), and galvanostatic charge-discharge cycling. The results showed that LiFe_0.4Mn_0.595Cr_0.005PO₄/C exhibited high specific capacity and high energy density. The initial discharge capacity of LiFe_0.4Mn_0.595Cr_0.005PO₄/C was 163.6 mAh g^?1 at 0.1C (1C = 160 mA g^?1), compared to 112.3 mAh g^?1 for LiMnPO₄/C. Moreover, the Fe/Cr-substituted sample showed good cycle stability and rate performance. The capacity retention of LiFe_0.4Mn_0.595Cr_0.005PO₄/C was 98.84 % over 100 charge-discharge cycles, while it was only 86.64 % for the pristine LiMnPO₄/C. These results indicated that Fe/Cr substitution enhanced the electronic conductivity for the prepared sample and facilitated the Li⁺ diffusion in the structure. Furthermore, LiFe_0.4Mn_0.595Cr_0.005PO₄/C composite presented high energy density (606 Wh kg^?1) and high power density (574 W kg^?1), thus suggested great potential application in lithium ion batteries (LIBs).     

Genesis,structural, and transport properties of La<Subscript>2</Subscript>Mo<Subscript>2-x</Subscript>W<Subscript>x</Subscript>O<Subscript>9</Subscript> prepared via mechanochemical activation

Fast oxide-ion conductors La₂Mo_2-xW_xO₉ (x = 0–1) have been prepared using mechanochemical activation (MA) of starting oxides in a high-power planetary ball mill. Studies of La₂Mo_2-xW_xO₉ genesis and structural properties using thermal analysis, XRD, SEM, IR, and Raman spectroscopy have revealed that MA results in the formation of an amorphous precursor, while the cubic β-phase is formed after calcination at 700–900 °C. Due to a high dispersion of powders, high-density pellets of W-LAMOX ceramics have been obtained already after sintering at 950 °C. Their electrical conductivity measured by the impedance spectroscopy depends on the W concentration being sufficiently high (up to 5.6?10^?3 S/cm at 630 °C) at temperatures below 650 °C.     

Improved electrochemical properties of YF<Subscript>3</Subscript>-coated Li<Subscript>1.2</Subscript>Mn<Subscript>0.54</Subscript>Ni<Subscript>0.13</Subscript>Co<Subscript>0.13</Subscript>O<Subscript>2</Subscript> as cathode for Li-ion batteries

Yttrium fluoride YF₃ layer with different coating contents is successfully covered on the surface of Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ via a common wet chemical approach. The XRD, SEM, TEM, and charge-discharge tests are applied to investigate the influence of YF₃ layer on the micro-structural, morphology, and electrochemical properties of Li_1.2Mn_0.54Ni_0.13Co_0.13O₂. And the electrochemical test results demonstrate that the YF₃-coated LMNCO samples exhibit the improved electrochemical properties. The 2wt.%YF₃-coated LMNCO delivers a discharge capacity of 116.6 mAh g^?1 at 5 C rate, much larger than that (95.6 mAh g^?1) of the pristine one. Besides, the electrochemical impedance spectroscopy (EIS) and cyclic voltammetric results indicate that the YF₃ coating layer can promote the optimization formation of SEI film and reversibility of the electrochemical redox.     

Phase transition and electrical investigation in lithium copper pyrophosphate compound Li<Subscript>2</Subscript>CuP<Subscript>2</Subscript>O<Subscript>7</Subscript> using impedance spectroscopy

Lithium pyrophosphate compound Li₂CuP₂O₇ has been synthesized through solid state reaction method. FTIR and XRD results, realized at room temperature, indicate respectively the dominant feature of pyrophosphate anion (P₂O₇)^4? and a pure monoclinic phase with I2/a space group. Electrical and dielectric properties have been studied using impedance spectroscopy complex over a wide temperature (576–710 K) and frequency (209 Hz–1 MHz) range. From the direct and alternative conductivities (DC and AC), electrical conduction is found to be thermally activated process. The frequency-dependent AC conductivity obeys Jonscher’s universal power law σ_AC~Aω^s. The differential scanning calorimetry spectrum discloses phase transition at 622 K.     

Thermoeletrochemical study on LiNi<Subscript>0.8</Subscript>Co<Subscript>0.1</Subscript>Mn<Subscript>0.1</Subscript>O<Subscript>2</Subscript> with in situ modification of Li<Subscript>2</Subscript>ZrO<Subscript>3</Subscript>

To improve the electrochemical performance of Nickel-rich cathode material LiNi_0.8Co_0.1Mn_0.1O₂, an in situ coating technique with Li₂ZrO₃ is successfully applied through wet chemical method, and the thermoelectrochemical properties of the coated material at different ambient temperatures and charge-discharge rates are investigated by electrochemical-calorimetric method. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) tests demonstrate that the Li₂ZrO₃ coating decreases the electrode polarizatoin and reduces the charge transfer resistance of the material during cycling. Moreover, it is found that with the ambient temperatures and charge-discharge rates increase, the specific capacity decreases, the amount of heat increases, and the enthalpy change (ΔH) increases. The specific capacity of the cells at 30 °C are 203.8, 197.4, 184.0, and 174.5 mAh g^?1 at 0.2, 0.5, 1.0, and 2.0 C, respectively. Under the same rate (2.0 C), the amounts of heat of the cells are 381.64, 645.32, and 710.34 mJ at 30, 40, and 50 °C. These results indicate that Li₂ZrO₃ coating plays an important role to enhance the electrochemical performance of LiNi_0.8Co_0.1Mn_0.1O₂ and reveal that choosing suitable temperature and current is critical for solving battery safety problem.     

CeO<Subscript>2</Subscript> coating to improve the performance of Li[Li<Subscript>0.2</Subscript>Mn<Subscript>0.54</Subscript>Ni<Subscript>0.13</Subscript>Co<Subscript>0.13</Subscript>]O<Subscript>2</Subscript>

The Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂ coated with CeO₂ has been fabricated by an ionic interfusion method. Both the bare and the CeO₂-coated samples have a typical layered structure with R-3m and C2/m space group. The results of XRD and TEM images display that the CeO₂ coating layer on the precursor could enhance the growth of electrochemically active surface planes ((010), (110), and (100) planes) in the following ionic interfusion process. The results of galvanostatic cycling tests demonstrate that the CeO₂-coated sample has a discharge capacity of 261.81 mAh g^?1 with an increased initial Coulombic efficiency from 62.4 to 69.1% at 0.05 °C compared with that of bare sample and delivers an improved capacity retention from 71.7 to 83.4% after 100 cycles at 1 °C (1 °C?=?250 mA g^?1). The results of electrochemical performances confirm that the surface modification sample exhibits less capacity fading, lower voltage decay, and less polarization.     

Investigation of the structural and electrochemical performance of Li<Subscript>1.2</Subscript>Ni<Subscript>0.2</Subscript>Mn<Subscript>0.6</Subscript>O<Subscript>2</Subscript> with Cr doping

Cr-doped layered oxides Li[Li_0.2Ni_0.2???x Mn_0.6???x Cr_2x ]O₂ (x?=?0, 0.02, 0.04, 0.06) were synthesized by co-precipitation and high-temperature solid-state reaction. The materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (TRTEM), X-ray photoelectron spectroscopy (XPS), and electrochemical impedance spectroscopy (EIS). XRD patterns and HRTEM results indicate that the pristine and Cr-doped Li_1.2Ni_0.2Mn_0.6O₂ show the layered phase. The Li_1.2Ni_0.16Mn_0.56Cr_0.08O₂ shows the best electrochemical properties. The first discharge specific capacity of Li_1.2Ni_0.16Mn_0.56Cr_0.08O₂ is 249.6 mA h g^?1 at 0.1 C, while that of Li_1.2Ni_0.2Mn_0.6O₂ is 230.4 mA h g^?1. The capacity retaining ratio of Li_1.2Ni_0.16Mn_0.56Cr_0.08O₂ is 97.9% compared with 93.9% for Li_1.2Ni_0.2Mn_0.6O₂ after 80 cycles at 0.2 C. The discharge capacity of Li_1.2Ni_0.16Mn_0.56Cr_0.08O₂ is 126.2 mA h g^?1 at 5.0 C, while that of the pristine Li_1.2Ni_0.2Mn_0.6O₂ is about 94.5 mA h g^?1. XPS results show that the content of Mn³⁺ in the Li_1.2Ni_0.2Mn_0.6O₂ can be restrained after Cr doping during the cycling, which results in restraining formation of spinel-like structure and better midpoint voltages. The lithium-ion diffusion coefficient and electronic conductivity of Li_1.2Ni_0.2Mn_0.6O₂ are enhanced after Cr doping, which is responsible for the improved rate performance of Li_1.2Ni_0.16Mn_0.56Cr_0.08O₂.     

Improving the rate performance and stability of LiNi<Subscript>0.6</Subscript>Co<Subscript>0.2</Subscript>Mn<Subscript>0.2</Subscript>O<Subscript>2</Subscript> in high voltage lithium-ion battery by using fluoroethylene carbonate as electrolyte additive

Fluoroethylene carbonate (FEC) is investigated as the electrolyte additive to improve the electrochemical performance of high voltage LiNi_0.6Co_0.2Mn_0.2O₂ cathode material. Compared to LiNi_0.6Co_0.2Mn_0.2O₂/Li cells in blank electrolyte, the capacity retention of the cells with 5 wt% FEC in electrolytes after 80 times charge-discharge cycle between 3.0 and 4.5 V significantly improve from 82.0 to 89.7%. Besides, the capacity of LiNi_0.6Co_0.2Mn_0.2O₂/Li only obtains 12.6 mAh g^?1 at 5 C in base electrolyte, while the 5 wt% FEC in electrolyte can reach a high capacity of 71.3 mAh g^?1 at the same rate. The oxidative stability of the electrolyte with 5 wt% FEC is evaluated by linear sweep voltammetry and potentiostatic data. The LSV results show that the oxidation potential of the electrolytes with FEC is higher than 4.5 V vs. Li/Li⁺, while the oxidation peaks begin to appear near 4.3 V in the electrolyte without FEC. In addition, the effect of FEC on surface of LiNi_0.6Co_0.2Mn_0.2O₂ is elucidated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The analysis result indicates that FEC facilitates the formation of a more stable surface film on the LiNi_0.6Co_0.2Mn_0.2O₂ cathode. The electrochemical impedance spectroscopy (EIS) result evidences that the stable surface film could improve cathode electrolyte interfacial resistance. These results demonstrate that the FEC can apply as an additive for 4.5 V high voltage electrolyte system in LiNi_0.6Co_0.2Mn_0.2O₂/Li cells.     

Nanocrystalline Li<Subscript>2</Subscript>TiO<Subscript>3</Subscript> electrodes for supercapattery application

Nanocrystalline Li₂TiO₃ was successfully synthesized using solid-state reaction method. The microstructural and electrochemical properties of the prepared material are systematically characterized. The X-ray diffraction pattern of the prepared material exhibits predominant (002) orientation related to the monoclinic structure with C2/c space group. HRTEM images and SAED analysis reveal the well-developed nanostructured particles with average size of ～40 nm. The electrochemical properties of the prepared sample are carried out using cyclic voltammetry (CV) and chronopotentiometry (CP) using Pt//Li₂TiO₃ cell in 1 mol L^?1 Li₂SO₄ aqueous electrolyte. The Li₂TiO₃ electrode exhibits a specific discharge capacity of 122 mAh g^?1; it can be used as anode in Li battery within the potential window 0.0–1.0 V, while investigated as a supercapacitor electrode, it delivers a specific capacitance of 317 F g^?1 at a current density of 1 mA g^?1 within the potential range ?0.4 to +0.4 V. The demonstration of both anodic and supercapacitor behavior concludes that the nanocrystalline Li₂TiO₃ is a suitable electrode material for supercapattery application.     

Enhanced electrochemical performance of Cu<Subscript>2</Subscript>O-modified Li<Subscript>4</Subscript>Ti<Subscript>5</Subscript>O<Subscript>12</Subscript> anode material for lithium-ion batteries

Li₄Ti₅O₁₂/Cu₂O composite was prepared by ball milling Li₄Ti₅O₁₂ and Cu₂O with further heat treatment. The structure and electrochemical performance of the composite were investigated via X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge–discharge tests. Li₄Ti₅O₁₂/Cu₂O composite exhibited much better rate capability and capacity performance than pristine Li₄Ti₅O₁₂. The discharge capacity of the composite at 2 C rate reached up to 122.4 mAh g^?1 after 300 cycles with capacity retention of 91.3 %, which was significantly higher than that of the pristine Li₄Ti₅O₁₂ (89.6 mAh g^?1). The improvement can be ascribed to the Cu₂O modification. In addition, Cu₂O modification plays an important role in reducing the total resistance of the cell, which has been demonstrated by the electrochemical impedance spectroscopy analysis.     

Synthesis of hierarchical Na<Subscript>2</Subscript>FeP<Subscript>2</Subscript>O<Subscript>7</Subscript> spheres with high electrochemical performance via spray drying

Hierarchical Na₂FeP₂O₇ spheres with nanoparticles were successfully fabricated by a facile spray drying method. A relatively low drying temperature was introduced in order to form a carbon layer on the surface. As a cathode material for sodium-ion batteries, it delivered a reversible capacity of 84.4 mAh g^?1 at 0.1 C and showed excellent cycling and rate performance (64.7 mAh g^?1 at 5 C). Furthermore, a full sodium battery was fabricated using SP-Na₂FeP₂O₇ as the cathode and hard carbon as the anode, suffering almost no capacity loss after 400 cycles at 1 C. Due to its superior electrochemical property and the low materials cost, Na₂FeP₂O₇ is becoming a promising cathode material for large-scale energy storage systems.     

Synthesis and Optical Properties of Novel Red-Emitting PbNb<Subscript>2</Subscript>O<Subscript>6</Subscript>: Eu<Superscript>3+</Superscript> Phosphors

Undoped and PbNb₂O_6:Eu³⁺ (1.0 ≤ x ≤ 6.0 mol%) phosphors were synthesized at 1100 °C for 3.5 h by the conventional solid state reaction method. Synthesized PbNb₂O₆:Eu³⁺ phosphors were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive spectroscopy (EDS) and Photoluminescence (PL) analyses. The PL spectra showed series of excitation peaks between 350 and 430 nm due to the 4f–4f transitions of Eu³⁺. For 395.0 nm excitation, emission spectra of Eu³⁺ doped samples were observed at 591 nm (orange) and 614 nm (red) due to the ⁵D₀ → ⁷F₁ transitions and ⁵D₀ → ⁷F₂ transitions, respectively. PL analysis results also showed that the emission intensity increased by increasing Eu³⁺ ion content. No concentration quenching effect was observed. The CIE chromaticity color coordinates (x,y) of the PbNb₂O₆:Eu³⁺ phosphors were found to be in the red region of the chromaticity diagram.     

The transport and thermal properties of glassy LiPO<Subscript>3</Subscript>/crystalline Al<Subscript>2</Subscript>O<Subscript>3</Subscript> (ZrO<Subscript>2</Subscript>) composite electrolytes

Glassy LiPO₃/crystalline Al₂O₃ and glassy LiPO₃/crystalline ZrO₂ (0–12.5 vol.% of oxide fillers) composite solid electrolytes have been prepared by glass matrix softening. Their thermal and transport properties have been investigated by differential scanning calorimetry (DSC) and impedance spectroscopy methods. The addition of ZrO₂ leads to a decrease in the crystallization temperature of LiPO₃ glass. It was found that the conductivity behavior depends on the nature of the dispersed addition. In the case of the Al₂O₃ addition, the increase in the electrical conductivity is observed. The ionic conductivity of the LiPO₃/10% Al₂O₃ composite reaches 5.8 × 10^?8 S/cm at room temperature. In contrast, the conductivity in the LiPO₃/ZrO₂ composite system decreases.     

Synthesis and electrochemical performance of Li<Subscript>3</Subscript>V<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript>/C by organic solvent replacement drying method

A series of Li₃V₂(PO₄)₃/C composite cathodes have been prepared by the organic solvent replacement drying method. Five kinds of organic solvent including ethyl alcohol, butyl alcohol, 2-methoxyethanol, 1,2-propylene glycol, and ethylene glycol were used in the drying process to replace the water respectively. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), and galvanostatic charge-discharge tests were employed to analyze the crystal structure, morphology, and electrochemical properties of the as-prepared materials. The results show that the organic solvent has a great influence on the secondary particle size of the as-synthesized materials. Special emphasis is placed on the sample prepared with 1,2-propylene glycol, which has the smallest average particle size and uniform distribution, thus leading to the best high rate performance and long-term cycling stability. The electrode exhibits average specific discharge capacities of 127.6, 128.3, 127.7, 126.7, 125.5, 124.4, 121.9, and 117.0 mAh g^?1 at 0.1, 0.2, 0.5, 1, 3, 5, 10, and 20C, respectively. More encouragingly, this sample delivers an outstanding cycle life with capacity retention of up to 94.68% even after 1000 cycles at 20C. Moreover, EIS results demonstrate that this sample has the minimum resistance and the largest apparent lithium ion diffusion coefficient (1.569 × 10^?7 cm² s^?1) which can facilitate to the Li⁺ diffusion during the charge/discharge process. Our results indicate that this preparation strategy can be facile and versatile for the synthesis of other high-rate and high-capacity intercalation materials.