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.     

Sulfur–carbon composite electrode for all-solid-state Li/S battery with Li2S–P2S5 solid electrolyte

All-solid-state Li/S batteries with Li₂S–P₂S₅ glass–ceramic electrolytes were fabricated and their electrochemical performance was examined. Sulfur–carbon composite electrodes were prepared by grinding with a mortar and milling with a planetary ball-mill apparatus. Milling of a mixture of sulfur, acetylene black and the Li₂S–P₂S₅ glass–ceramic electrolyte resulted in the amorphization of sulfur and a reduction in the particle size of the mixture. The charge–discharge properties of all-solid-state cells with the composite electrode were investigated at temperatures from −20 °C to 80 °C. The cells retained a reversible capacity higher than 850 mAh g⁻¹ for 200 cycles under 1.3 mA cm⁻² (333 mA g⁻¹) at 25 °C. The cell performance was influenced by the crystallinity of sulfur and the particle size of the electrode material, whereby improved contact among the electrode components achieved by milling contributed to enhancement of the capacity of an all-solid-state Li/S cell.     

Fabrication of Li2O-B2O3-P2O5 solid electrolyte by flame-assisted ultrasonic spray hydrolysis for thin film battery

Li₂O-B₂O₃-P₂O₅ glass soot was fabricated from aqueous precursor solution of a CH₃CO₂Li·2H₂O and BCl₃, POCl₃ by the flame-assisted ultrasonic spray hydrolysis. The aqueous precursor solution of the lithium acetates was first atomized with an ultrasonic vibrator (1.7 MHz). B₂O₃ and P₂O₅ were formed from BCl₃ and POCl₃ by oxy-hydrogen flame. Their properties were investigated by SEM, XRD, TGA-DSC and impedance analyzer. The formed particles in glass soot had spherical shape and the size of approximately 50-100 nm. XRD analysis revealed that the amorphous phase and crystalline phases were mixed in glass soot and the crystalline phases were B(OH)₃ and B₂O₃. The crystalline B(OH)₃ and B₂O₃ found in glass soot completely disappeared by heat treatment. Conductivity was measured by complex impedance method using impedance analyzer and the conductivity was 10⁻⁸ S/cm.     

Enhancement of density and ionic conductivity for garnet-type Li5La3Ta2O12 solid electrolyte by self-consolidation strategy

Garnet-type Li₅La₃Ta₂O₁₂ (LLTaO) solid electrolyte is a potential candidate component for future all-solid-state batteries due to its extraordinary stability against the reaction with molten lithium. In contrast with traditional cold isostatic pressing (CIP) method, which generally pursues ultra-high pressure, this paper tries to enhance the density and ionic conductivity of LLTaO by self-consolidation strategy without the assistance of any pressing operations. A LLTaO bulk with a relative density of 95% is obtained. SEM images reveal that the bulk sample is assembled by large dense particles in size of tens of microns indicating that the interstitial space among the particles has been dramatically minimized. Accordingly, the total ionic conductivity and the bulk ionic conductivity at 30?°C are promoted up about one order of magnitude higher to 2.63?× 10^?5 S?cm^?1 and 1.41?×?10^?4 S?cm^?1, respectively. Moreover, the lithium ionic migration network in the crystalline unit cell of LLTaO is first explored from its assembled way. A hexagon-like basic unit with tetrahedral Li1 joint sites and Li1- - Li1 edges is identified. The tetrahedral Li1 sites act as crucial junctions for the transportation of lithium ions. This work would significantly stimulate the development of LLTaO electrolyte membrane technology.     

Effect of sol composition on solid electrode/solid electrolyte interface for all-solid-state lithium ion battery

A property of interface between solid electrode and solid electrolyte is one of the most important keys to fabricate all-solid-state lithium ion battery. In this study, an influence of sol composition used for preparation of the electrode on the property of interface between electrode and electrolyte was examined. LiMn₂O₄/honeycomb Li_0.55La_0.35TiO₃ (LLT) and Li₄Mn₅O₁₂/honeycomb LLT half cells were fabricated by impregnation of mixture of active materials with various precursor sols into honeycomb holes. In the case of LiMn₂O₄ cathode, the sol composed of nitrate salt provides large contact area of LiMn₂O₄ and LLT, resulting in higher performance of the cell. Li₂MnO₃ impurity was produced at Li₄Mn₅O₁₂/LLT interface prepared by the precursor sol composed of only nitrate or acetate salts although no impurity phase was observed at the interface prepared by acetate–nitrate sol containing lithium acetate and manganese nitrate. Li₄Mn₅O₁₂/honeycomb LLT half cell prepared by the acetate–nitrate sol showed the best performance among them. It is concluded that composition of the precursor sol strongly influenced on the interface of electrode and electrolyte. The all-solid-state Li ion battery composed of LiMn₂O₄/honeycomb LLT/Li₄Mn₅O₁₂ was successfully operated and the discharge capacity was 32 μAh cm⁻².     

Relationship between glass network structure and conductivity of Li2O-B2O3-P2O5 solid electrolyte

Solid state glass electrolyte, xLi₂O-(1 − x)(yB₂O₃-(1 − y)P₂O₅) glasses were prepared with wide range of composition, i.e. x = 0.35 - 0.5 and y = 0.17 - 0.67. This material system is one of the parent compositions for chemically and electrochemically stable solid-state electrolyte applicable to thin film battery. Lithium ion conductivity of Li₂O-B₂O₃-P₂O₅ glasses was studied in the correlation to the structural variation of glass network by using FTIR and Raman spectroscopy. The measured ionic conductivity of the electrolyte at room temperature increased with x and y. The maximum conductivity of this glass system was 1.6 × 10⁻⁷ Ω⁻¹ cm⁻¹ for 0.45Li₂O-0.275B₂O₃-0.275P₂O₅ at room temperature. It was shown that the addition of P₂O₅ reduces the tendency of devitrification and increases the maximum amount of Li₂O added into glass former without devitrification. As Li₂O and B₂O₃ contents increased, the conductivity of glass electrolyte increased due to the increase of three-coordinated [BO₃] with a non-bridging oxygen (NBO).     

High lithium ion conducting Li2S–GeS2–P2S5 glass–ceramic solid electrolyte with sulfur additive for all solid-state lithium secondary batteries

Glass–ceramic Li₂S–GeS₂–P₂S₅ electrolytes were prepared by a single step ball milling (SSBM) process. Various compositions of Li_4−xGe_1−xP_xS₄ from x = 0.70 to x = 1.00 were systematically investigated. Structural analysis by X-ray diffraction (XRD) showed gradual increase of the lattice constant followed by significant phase change with increasing GeS₂. All-solid-state LiCoO₂/Li cells were tested by constant-current constant-voltage (CCCV) charge–discharge cycling at a current density of 50 μA cm⁻² between 2.5 and 4.3 V (vs. Li/Li⁺). In spite of the high conductivity of the solid-state electrolyte (SSE), LiCoO₂/Li cells showed a large irreversible reaction especially during the first charging cycle. Limitation of instability of Li₂S–GeS₂–P₂S₅ in contact with Li was solved by using double layer electrolyte configuration: Li/(Li₂S-P₂S₅/Li₂S–GeS₂–P₂S₅)/LiCoO₂. LiCoO₂ with SSEs heat-treated with elemental sulfur at elevated temperature exhibited a discharge capacity of 129 mA h g⁻¹ at the second cycle and considerably improved cycling stability.     

Mechanical and electrochemical properties of cubic and tetragonal LixLa0.557TiO3 perovskite oxide electrolytes

Solid oxide electrolytes with high Li ion conductivity and mechanical stability are vital for all solid-state lithium ion batteries. The perovskite material Li_xLa_0.557TiO₃ with various initial Li (0.303 ≤ x ≤ 0.370) is synthesized by traditional solid-state reaction. The cubic and tetragonal structures are prepared with fast and slow cooling, respectively. The results reveal that the Li ion conductivity of the cubic structure is higher. In fact, the bulk conductivity of 1.65 × 10^?3 S cm^?1 is obtained at room temperature for x = 0.350. The crystal structure is not affected by the Li₂O quantity. In addition, Young's modulus, hardness, and fracture toughness are determined with indentation method for both structures. The Young's modulus increases with increasing Li₂O. However, hardness and fracture toughness keep a relatively stable value independent of Li₂O quantity.     

The synergistic effect of dual substitution of Al and Sb on structure and ionic conductivity of Li7La3Zr2O12 ceramic

Li₇La₃Zr₂O₁₂ (LLZO) with cubic garnet type structure is a promising solid electrolyte. In this work, Li_6.925-3xAl_xLa₃Zr_1.925Sb_0.075O₁₂ (0 ≤ x ≤ 0.1) electrolytes were prepared by conventional solid-state reaction. The influence of Sb-Al cosubstitution on the structure, microstructure and conductivity of Li₇La₃Zr₂O₁₂ were investigated by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and impedance spectroscopy. Single cubic phase has been achieved for Li_6.925-3xAl_xLa₃Zr_1.925Sb_0.075O₁₂ (x = 0–0.075). Suitable amount of Al-Sb cosubstitution accelerates densification and improves the ionic conductivity. Li_6.775Al_0.05La₃Zr_1.925Sb_0.075O₁₂ exhibits highest relative densities (96.7%) and total ionic conductivity (4.10 × 10^?4 S/cm at 30 °C).     

Li ion conduction of perovskite Li0.375Sr0.4375Ti0.25Ta0.75O3 and related compounds

In this work, perovskite-structured Li_0.375Sr_0.4375M_0.25N_0.75O₃ (M=Ti, Sn, N=Nb, Ta) solid electrolytes were synthesized by conventional solid state reaction method. Phase compositions, fractured morphologies and conductivities of these compounds were investigated by X-ray diffraction, scanning electron microscope and AC-impedance spectroscopy, respectively. X-ray diffraction analysis confirms that all of Li_0.375Sr_0.4375M_0.25N_0.75O₃ (M=Ti, Sn, N=Nb, Ta) ceramics present perovskite structure. Pure Li_0.375Sr_0.4375Ti_0.25Ta_0.75O₃ and Li_0.375Sr_0.4375Sn_0.25Ta_0.75O₃ perovskite ceramics were obtained. But impurities were detected in Li_0.375Sr_0.4375Ti_0.25Nb_0.75O₃ and Li_0.375Sr_0.4375Sn_0.25Nb_0.75O₃. Among all investigated compounds, Li_0.375Sr_0.4375Ti_0.25Ta_0.75O₃ shows the highest total ionic conductivity of 2.60 × 10^?4 S cm^?1 at room temperature and the lowest activation energy of 0.347 eV. Conductivities of Li_0.375Sr_0.4375Sn_0.25Ta_0.75O₃ and Li_0.375Sr_0.4375Sn_0.25Nb_0.75O₃ were 4.4 × 10^?5 S cm^?1 and 1.82 × 10^?6 S cm^?1, respectively. Their conductivities were much lower than Li_0.375Sr_0.4375Ti_0.25Ta_0.75O₃ and Li_0.375Sr_0.4375Ti_0.25Nb_0.75O₃.     

Effects of the surface treatment of the Al2O3 filler on the lithium electrode/solid polymer electrolyte interface properties

The lithium deposition-dissolution process in solid polymer electrolytes containing Al₂O₃ filler treated under different conditions has been investigated comparing with the ionic conduction behavior of the electrolyte. The composite electrolytes were prepared from poly(ethylene oxide) (PEO), LiBF₄ and α-Al₂O₃ filler by using a dry process, where the surface of α-Al₂O₃ was beforehand modified by a wet process. The exchange current densities, i₀, of the lithium electrode process in P(EO)₂₀LiBF₄ with and without Al₂O₃ filler were determined by a micro-polarization method. The temperature dependence of i₀ provided similar values for activation energy, ca. 25 and 70 kJ mol⁻¹ in both temperature regions above and below 60 °C, respectively. The effect of the surface treatment of the filler on the lithium electrode process gave a different tendency from that on the ionic conductivity. The Al₂O₃ surface treated by alkali solution enhanced the electrode process to the largest extent among the fillers used here, while it led to rather poor cycling stability in voltammetry. The enhanced reaction rate at the lithium electrode/solid polymer electrolyte interface has probably resulted in the improved ion dissociation by the surface groups of the Al₂O₃ filler.     

Improvement of cycle performance of lithium ion cell LiMn2O4/LixV2O5 with aqueous solution electrolyte by polypyrrole coating on anode

The reasons of capacity fading during cycling process of LiMn₂O₄/Li_xV₂O₅ lithium ion cell with 5 M LiNO₃ aqueous solution as electrolyte were investigated. XRD and ICP results showed that the properties of the anode have more impact on the cycle life of the cell. In an attempt to improve the cycle performance of the as-assembled cell, coating with an ionic conductive polypyrrole (PPy) on the surface of the anode was proposed via in situ polymerization method. Cycling tests revealed that the stability of the lithium ion cell with surface coated anode has been greatly improved. Moreover, the capability of the cell with coated anode was also enhanced compared with the cell with bare anode.     

Effects of particle size and electrolyte salt on the thermal stability of Li0.5CoO2

Accelerating rate calorimetry (ARC) has been used to compare the thermal stability of three Li_0.5CoO₂ materials with different particle sizes (diameters of approximately 0.8, 2, and 5 μm, respectively) when heated in 1.0 M LiPF₆ EC/DEC or 0.8 M LiBoB EC/DEC electrolytes. The thermal stability of Li_0.5CoO₂ was found to be related to its particle size. The larger the particle size, the higher the onset temperature of self-heating as measured by ARC. In the presence of sufficient reducing agent, EC/DEC solvent, Li_0.5CoO₂ can be reduced to Co₃O₄, CoO, eventually even to Co metal. The heats of reaction for each of these steps are 550, 270 and 540 J/g, respectively, measured per gram of Li_0.5CoO₂. The addition of LiPF₆ salt significantly decreases the reactivity of Li_0.5CoO₂ compared to pure EC/DEC solvent. The reactivity of Li_0.5CoO₂ is stronger in 0.8 M LiBoB EC/DEC than in LiPF₆ EC/DEC.     

Li4Ti5O12 hollow microspheres assembled by nanosheets as an anode material for high-rate lithium ion batteries

In this paper, Li₄Ti₅O₁₂ (LTO) hollow microspheres with the shell consisting of nanosheets have been synthesized via a hydrothermal route and following calcination. Because of the favorable transport properties of this hollow structure, it is the rate performance at high current densities which is exceptional. When the LTO hollow microspheres were used as the anode material in lithium ion battery, they exhibited superior rate performance and high capacity even at a very high rate (131 mAh g⁻¹ at 50 C).     

Lithium/V6O13 cells using silica nanoparticle-based composite electrolyte

The electrochemical behavior of Li/V₆O₁₃ cells is investigated at room temperature (22 °C) both in liquid electrolyte consisting of oligomeric poly(ethyleneglycol)dimethylether+lithium bis(trifluoromethylsulfonylimide) and composite electrolytes formed by blending the liquid electrolyte with silica nanoparticles (fumed silica). The addition of fumed silica yields a gel-like electrolyte that demonstrates the desirable property of suppressing lithium dendrite growth due to the rigidity and immobility of the electrolyte structure. The lithium/electrolyte interfacial resistance for composite gel electrolytes is less than that for the corresponding base-liquid electrolyte, and the charge-discharge cycle performance and electrochemical efficiency for the Li/V₆O₁₃ cell is significantly improved. The effect of fumed silica surface group on the electrochemical performance is discussed; the native hydrophilic silanol surface group appears better than fumed silica that is modified with a hydrophobic octyl surface moiety.     

Electrochemical performance of high specific capacity of lithium-ion cell LiV3O8//LiMn2O4 with LiNO3 aqueous solution electrolyte

The electrochemical performance of aqueous rechargeable lithium battery (ARLB) with LiV₃O₈ and LiMn₂O₄ in saturated LiNO₃ electrolyte is studied. The results indicate that these two electrode materials are stable in the aqueous solution and no hydrogen or oxygen produced, moreover, intercalation/de-intercalation of lithium ions occurred within the range of electrochemical stability of water. The electrochemical performance tests show that the specific capacity of LiMn₂O₄ using as the cathode of ARLB is similar to that of ordinary lithium-ion battery with organic electrolyte, which works much better than the formerly reported. In addition, the cell systems exhibit good cycling performance. Therefore, it has great potential comparing with other batteries such as lead acid batteries and alkaline manganese batteries.     

Response characteristics of all-solid-state pH sensor using Li5YSi4O12 glass

A new type of all-solid-state pH sensor was investigated for the monitoring of pH in high temperature. The all-solid-state pH sensor consists of two half-cells: indicator electrode using the Li₅YSi₄O₁₂ glass and an Ag/AgCl reference electrode coated with Nafion film. A stable Nafion film was achieved by heat treating at 100 °C for 1 h. The electromotive force (EMF) of the all-solid-state pH sensor decreased linearly with pH increase in water in accordance with the Nernst's equation. The all-solid-state pH sensor operated stably up to 80 °C. The sensitivity of the all-solid-state pH sensor against pH was high, and the EMF was also scarcely influenced by the presence of inorganic ions such as Li⁺, Na⁺ and Cl⁻. It was practically confirmed by the pH titration test that the all-solid-state pH sensor behaved similar to the commercial pH meter with the conventional glass electrode. In addition, the all-solid-state pH sensor showed same equivalence point both at high temperature and low temperature operations.     

Solid-state electrochromic devices with Nb2O5:Mo thin film and gelatin-based electrolyte

A gelatin-based electrolyte has been developed and characterized by impedance spectroscopy, X-ray diffraction, UV-vis-NIR spectroscopy and atomic force microscopy (AFM). The heat treatment temperature was found the key factor affecting its ionic conductivity that increases from 1.5 × 10⁻⁵ S/cm to 4.9 × 10⁻⁴ S/cm by heating from room temperature up to 80 °C. The temperature dependence of the ionic conductivity exhibits an Arrhenius behavior. EC-devices with the configuration K-glass/Nb₂O₅:Mo EC-layer/gelatin-based electrolyte/(CeO₂)_x(TiO₂)_1−x ion-storage (IS) layer/K-glass, have been assembled and characterized. They show a good long time cyclic stability, but the change of the optical density measured at 550 nm after 25 000 cycles was only 0.13.     

离子液体BMIMBF4对全钒液流电池正极电解液的影响

为提高全钒液流电池的能量密度和正极电解液稳定性,采用循环伏安、交流阻抗等方法,研究了1-丁基-3-甲基咪唑四氟硼酸盐（BMIMBF₄）作为正极电解液添加剂对溶液稳定性和电化学反应活性的影响,并对其机理进行了初步探讨。实验结果表明,添加BMIMBF₄后,正极电解液中五价钒离子的稳定性显著提高,电解液的电化学反应活性也有所提升。当添加量为1%时,电池的单位体积电容量比有所增加,并且能量效率有所提升。     

The preparation and characterization of Li4Ti5O12/carbon nano-tubes for lithium ion battery

Li₄Ti₅O₁₂/carbon nano-tubes (CNTs) composite was prepared by sol-gel method while Ti(OC₄H₉)₄, LiCH₃COO·2H₂O and the n-heptane containing CNTs were used as raw materials. The characters of Li₄Ti₅O₁₂/CNTs composite were determined by XRD, SEM, and TG methods. Its electrochemical properties were measured by charge-discharge cycling and impedance tests. It was found that the prepared Li₄Ti₅O₁₂/CNTs presented an excellent rate capability and capacity retention. At the charge-discharge rate of 5C and 10C, its discharge capacities were 145 and 135 mAh g⁻¹, respectively. After 500 cycles at 5C, the discharge capacity retained as 142 mAh g⁻¹. It even could be cycled at the rate of 20C. The excellent electrochemical performance of Li₄Ti₅O₁₂/CNTs electrode could be attributed to the improvement of electronic conductivity by adding conducting CNTs and the nano-size of Li₄Ti₅O₁₂ particles in the Li₄Ti₅O₁₂/CNTs composite.