Lithiated c-V<Subscript>2</Subscript>O<Subscript>5</Subscript> thin-film as positive electrode for rocking-chair solid-state lithium microbattery

We report for the first time the use of lithiated crystalline V₂O₅ thin films as positive electrode in all-solid-state microbatteries. Crystalline Li_xV₂O₅ films (x ≈ 0.8 and 1.5) are obtained by vacuum evaporation of metallic lithium deposited on sputtered c-V₂O₅. An all-solid-state lithium microbattery of Li_1.5V₂O₅/LiPON/Li exhibited a typical reversible capacity of 50 μAh/cm² in the potential range 3.8/2.15 V which exceeds by far the results known on all-solid-state lithium batteries using amorphous V₂O₅ films and lithiated amorphous Li_xV₂O₅ thin films as positive electrode. Hence, the present work opens the possibility of using high performance crystalline lithiated V₂O₅ thin films in rocking-chair solid-state microbatteries.     

Sub-10 nm V2O5 Crystals on Carbon Nanosheets for Advanced All-Solid-State Lithium Metal Batteries

V₂O₅, as a lithium-free cathode material, has inherent defects such as sluggish kinetics and volume change and, at the same time, requires a lithium metal anode that tends to form dendrites in liquid electrolytes. Both the lithium dendrite and the flammable electrolyte solvent bring longtime safety issues. This work introduces nonflammable inorganic–organic composite solid electrolyte to inhibit the growth of the lithium dendrite and suppress the instability caused by V₂O₅ nanometerization. However, the long-term cycling and rate performances are still insufficient even when reducing V₂O₅ size to about 50 nm. As an improvement, sub-10 nm V₂O₅/C nanosheets are designed and prepared using corn stalks as precursors through simple impregnation and calcination process. The V₂O₅/C offers a much better electrode/electrolyte contact and interface stability than bulk V₂O₅ and commercial V₂O₅ in the inorganic–organic composite solid electrolyte. The discharge capacity is 228 mAh g⁻¹ at 0.1 C after 50 cycles and ≈110 mAh g⁻¹ at 2.0 C.     

Thermochemistry of the high and ambient temperature lithium vanadium bronze phases LixV2O5

The enthalpies of formation of a series of high and low temperature phases in the ternary oxide system Li_xV₂O₅ have been determined by solution calorimetry. Samples of the former, α-Li_0.04V₂O₅, β-Li_0.30V₂O₅, β'-Li_0.48V₂O₅ and γ-LiV₂O₅, were prepared by solid state reaction at 650°C. The ambient temperature materials Li_0.1V₂O₅(I), Li_0.45V₂O₅(II) and Li_1.03V₂O₅(III) were prepared by n-butyl lithiation in hexane. The thermochemistries of the two classes of material were examined and related to structural features and to the observed behaviour of V₂O₅ as a battery cathode material in lithium cells.     

Cathodic performance of V2O5 nanowires and reduced graphene oxide composites for lithium ion batteries

In this study, vanadium pentoxide (V₂O₅) nanowires (NWs) with a diameter of 100–200 nm and a length of up to several micrometers as cathode for lithium ion batteries are synthesize using an electrospinning method. The reduced graphene oxide (rGO) and V₂O₅ NWs (GVO) composites are form by wet mixing the electrospun V₂O₅ NWs and rGO. Surface morphologies, microstructure and elemental mapping, and chemical bonding states of the composites are characterize. The initial and 60 cycles discharge capacities of GVO composite composed of 1 wt% rGO show up to 225 mAh g⁻¹ and 125 mAh g⁻¹, even higher than pure V₂O₅ NWs, when the lithium ion battery cycled between 2.0 and 4.0 V with a rate of 0.2 C, because of highly conductive rGO. The GVO composite could be promising as a high performance cathode for lithium ion batteries.     

Solid-state lithium microbatteries

Batteries of the size of microelectronic devices, less than 10 μm thick, are now being developed and built, using thin-film deposition technologies, i.e., flash-evaporation, rf-sputtering and sol-gel technique, that are compatible with integrated circuits. Their use in future micro-devices, microsensors, intergrated circuits, memories and very large-scale integration are envisaged. Advances have been made particularly in the engineering of lithium/amorphous inorganic electrolyte/layered compound cells. Physics of the solid-state microbatteries are reviewed and the latest advances presented. The adequacy and efficiency of materials is examined. New optimized lithium microbatteries including transition-metal oxides as intercalation cathodes, i.e., MoO₃, V₂O₅, and V₆O₁₃ films are presented and their advantages are discussed in detail. Paper presented at the 2nd Euroconference on Solid State Ionics, Funchal, Madeira, Portugal, 10–16 Sept. 1995.     

The sol-gel mixed oxide Cr0.11V2O5.16: An attractive cathodic material for secondary lithium batteries

Preliminary results of the properties of a new mixed oxide Cr_0.11V₂O_5.16 which was synthesized by a sol-gel process and may be used as cathode material for secondary lithium batteries are presented in this paper. The electrochemical properties are investigated and compared with those exhibited by the sol-gel vanadium pentoxide V₂O₅. The results are discussed with respect to the structural data available from these compounds. The presence of Cr³⁺ and additional O^2- ions in the structure notably emphasizes the attractive performances of the material both in terms of specific capacity and cycle life. In particular, a high capacity is still available even for the pure material used without addition of electronic conductor. The cyclability, as well as the behaviour at high discharge rates are found to be significantly better than for the parent oxide V₂O₅. These results are consistent with structural considerations from which less severe structural deformations are expected during lithium insertion. Paper presented at the 4th Euroconference on Solid State Ionics, Connemara, Galway, Ireland, Sept. 13–19, 1997     

非晶态锂离子导体B2O3-0.7Li2O-0.7LiCl-xAl2O3-0.1V2O5的电学性质和电子自旋共振研究

对两种非晶态B₂O₃-0.7Li₂O-0.7LiCl-xAl₂O₃-0.1V₂O₅(x=0.05和0.15),用差热分析、电导率测量、X射线衍射和电子自旋共振进行研究,发现:1)V₂O₅不仅作非晶网络形成剂,而且改变了晶化过程;2)对B₂O₃-Li_{2关键词：}     

Electrochemical and structural properties of MoO3–V2O5 nanocomposite thin film electrodes for lithium rechargeable batteries

We have investigated the electrochemical properties of V₂O₅-based thin film electrodes as a function of the amount of MoO₃ by means of X-ray diffraction (XRD), X-ray photoemission spectroscopy (XPS), and transmission electron microscopy (TEM). XRD results show that the V₂O₅-based thin film electrodes give an amorphous characteristic. XPS results reveal the formation of V₂O₅ and MoO₃ phases. TEM results show that MoO₃ dots (5–30 nm in size) are embedded in the amorphous V₂O₅ matrix. It is further shown that cells fabricated with the MoO₃–V₂O₅ nanocomposite thin film electrodes give better cycling performance than those made with the single V₂O₅ thin film electrodes. A possible explanation for the MoO₃ nano-dot dependence on the cycling performance of the V₂O₅-based thin film electrodes is described.     

Experimental routes to in situ characterization of the electronic structure and chemical composition of cathode materials for lithium ion batteries during lithium intercalation and deintercalation using photoelectron spectroscopy and related techniques

Three different experimental routes to in situ characterization of electronic structure and chemical composition of thin film cathode surfaces used in lithium ion batteries are presented. The focus is laid on changes in electronic structure and chemical composition during lithium intercalation and deintercalation studied by photoelectron spectroscopy and related techniques. At first, results are shown obtained from spontaneous intercalation into amorphous or polycrystalline V₂O₅ thin films after lithium deposition. Although this technique is simple and clean, it is nonreversible and only applicable to the first lithium intercalation cycle into the cathode only to be applied to host materials stable in the delithiated stage. For other cathode materials, as LiCoO₂, a real electrochemical setup has to be used. In our second approach, the experiments are performed in a specially designed electrochemical cell directly connected to the vacuum system. First experimental results of RF magnetron sputtered V₂O₅ and LiCoO₂ thin film cathodes are presented. In the third approach, an all solid-state microbattery cell must be prepared inside the vacuum chamber, which allows electrochemical processing and characterization by photoelectron spectroscopy in real time. We will present our status and experimental difficulties in preparing such cells.     

Synthesis of solid solutions of Mn and Bi substituted V2O5 and substitutional effect in structural and optoelectronic behavior

V₂O₅ is an attractive material with enormous technological applications such as cathode material in lithium batteries and electrochromic displays. Mn and Bi substitution in vanadium pentoxide (V₂O₅) was done by conventional solid state reaction technique with different composition. The chemical composition, structural and optical properties were investigated employing different techniques, such as XRD, SEM and UV-Vis Spectra. XRD studies exhibit the predominant (0 0 1) peak of orthorhombic phase. SEM image shows the uniformity of the material synthesized. Variable transmittance is exhibited by samples doped with different percentages of dopants. The dielectric property studies and ac conductivity measurements were carried out by Hioki LCR Hi-Tester.     

Electrochemical properties of Cr doped V2O5 between 3.8 V and 2.0 V

Cr_0.1V₂O_5.15 was prepared by an oxalic acid assisted sol–gel method. X-ray diffraction showed that Cr doping induced a slight expansion (ΔV/V ≈ 2.3%) in the crystal lattice of V₂O₅. The electrochemical properties of Cr_0.1V₂O_5.15 in the potential range of 3.8–2.0 V were studied by cyclic voltammetry, galvanostatic charge–discharge cycling and potentiostatic intermittent titration technique. Cyclic voltammetry showed that the irreversible phase transition of V₂O₅ during the first cycle was effectively prevented by Cr doping. This caused the good charge–discharge cycling performance of the doped material. The discharge capacities were recorded to be 200, 170 and 120 mAhg^− 1 after fifty cycles at the C/10, C/2 and 1C rates, respectively. However, ex-situ X-ray diffraction showed that the crystal structure of the material was destroyed after long-term cycling. The lithium diffusion coefficient of Cr_0.1V₂O_5.15 varied between 10^− 11 and 10^− 12 cm² s^− 1, which was larger than that of crystalline V₂O₅, and was close to those of metal doped V₂O₅ in previous reports. The improvement in lithium diffusion kinetics was regarded as an important reason for the good electrochemical performance of Cr_0.1V₂O_5.15.     

X-RAY PHOTOELECTRON SPECTROSCOPY STUDY ON ELECTROCHROMIC V2O5 THIN FILM

Nanocrystalline V₂O₅ thin films were reactively radio-frequency magnetron-sputtered under optimal deposition parameters. Their electrochemical and electrochromic characteristics were investigated by cyclic voltammetry and in-situ monochromatic transmittance measurements. Upon lithium intercalation, V₂O₅ thin films showed a double electrochromic behavior depending on the wavelength and the intercalation extent. X-ray photoelectron spectroscopy results showed that part of the V⁵⁺ in V₂O₅ was reduced to V⁴⁺ during the Li⁺ intercalation process.     

Vanadium Pentoxide‐Based Cathode Materials for Lithium‐Ion Batteries: Morphology Control,Carbon Hybridization,and Cation Doping

Vanadium pentoxide (V₂O₅) is a promising cathode material for high‐performance lithium‐ion batteries (LIBs) because of its high specific capacity, low cost, and abundant source. However, the practical application of V₂O₅ in commercial LIBs is still hindered by its intrinsic low ionic diffusion coefficient and moderate electrical conductivity. In the past decades, progressive accomplishments have been achieved that rely on the synthesis of nanostructured materials, carbon hybridization, and cation doping. Generally, fabrication of nanostructured electrode materials can effectively decrease the ion and electron transport distances while carbon hybridization and cation doping are able to significantly increase the electrical conductivity and diffusion coefficient of Li⁺. Implementation of these strategies addresses the problems that are related to the ionic and electronic conductivity of V₂O₅. Accordingly, the electrochemical performances of V₂O₅‐based cathodes are significantly improved in terms of discharge capacity, cycling stability, and rate capability. In this review, the recent advances in the synthesis of V₂O₅‐based cathode materials are highlighted that focus on the fabrication of nanostructured materials, carbon hybridization, and cation doping.     

锂硼钒酸盐玻璃的11B核磁共振研究

用¹¹B连续波核磁共振谱研究了锂硼钒酸盐玻璃的结构,测量了BO₄,BO_3s和BO_3A各结构单元的比例。实验表明,锂硼钒酸盐玻璃中N₄的最大值近似为一常数,与V₂O₅的含量无关。Li₂O被V₂O₅和B₂O₃分享。并推测V₂O< 关键词：     

Materials design and optimization for thin-film microbatteries

Considerable effort has been invested in developing thin-film solid microbatteries as possible integrated components in microelectronics. Advances have been made particularly in the engineering of lithium/amorphous inorganic electrolyte/layered compound cells fabricated using various evaporation techniques. The main features of these cells are influenced by the characteristics of the fast ionic conductor and the insertion compound layers which are discussed in detail in this work. Design and optimization of lithium-microbattery components are discussed. Different electrochemical systems using lithium borate-glass films as solid electrolytes have been fabricated and characterized. Thin-film active cathodic materials include transition-metal dichalcogenides such as TiS₂, MoS₂, non-transition-metal chalcogenides such as InSe and transition-metal oxides such as MoO₃, V₂O₅, V₆O₁₃ films. Particular attention is paid to the structural and transport properties of these materials and their behaviour in electrochemical lithium cells are presented. Thermodynamics and kinetics are studied as functions of the growth conditions of thin-film components. The physical properties are discussed in relation to the electrochemical cell behavior and battery performance. Paper presented at the 1st Euroconference on Solid State Ionics, Zakynthos, Greece, 11–18 Sept. 1994.     

Electrochemical behaviour of sputtered c-V2O5 and LiCoO2 thin films for solid state lithium microbatteries

Here are reported for the first time electrochemical data on all-solid-state lithium microbatteries using crystalline sputtered V₂O₅ thin films as cathode materials and LiPON as solid electrolyte. The stable specific capacity of 30 µAh/cm² found with a 2.4 µm thick film competes very well with the best values obtained for solid state microbatteries using amorphous films. With the challenge of decreasing the temperature of heat treatment for sputtered LiCoO₂ thin films, we show that a temperature of 500 °C combined with an optimized bias sputtering (-50 V) allows to get highly crystalline deposits, to minimize the presence of Co₃O₄ and to suppress any trace of the cubic phase. At the same time the theoretical specific capacity is reached in the 4.2 V-3 V range and a good cycling behaviour is achieved with a high capacity of 50 µAh/cm²/µm after 140 cycles at 10 µA.cm².     

Dielectric constant and microwave conductivity of the vanadium bronze Na0.33V2O5

Measurements of the dielectric constant and microwave conductivity are reported for the vanadium bronze Na_0.33V₂O₅. The dielectric constant is highly anisotropic and very large parallel to the highly conducting direction, while the conductivity is strongly dispersive. The results can be consistently interpreted by considering Na_0.33V₂O₅ as a quasi-one-dimensional conductor in which, at low temperatures, a pseudo-gap opens in the open-electron density of states due to inter-site correlations.     

d 1 Electrons in amorphous semiconducting V2O5 and MoO3 compounds. (ESR measurements)

We have performed electron spin resonance experiments on binary amorphous V₂ O₅- and MoO₃ compounds (V₂O₅-TeO₂, V₂O₅-BaO, V₂O₅-PbO, V₂O₅-GeO₂, V₂O₅-As₂O₃, MoO₃-P₂O₅, MoO₃-TeO₂) and determined the parameters of the corresponding spin Hamiltonian by 3 cm-, 1.2 cm- and 8 mm band measurements. These measurements yielded values of the contribution to the mean energy difference of thed ¹ levels between different vanadium- or molybdenum sites caused by fluctuations of the crystal field.     

Crystallization kinetics of Li2O-PbO-V2O5 glasses

Lead vanadate glasses of the system 5Li₂O−(45−x) PbO−(50+x) V₂O₅, with x=0, 5, 10, and 15 mol% have been prepared and studied by differential scanning calorimetry (DSC). The crystallization kinetics of the glasses were investigated under non-isothermal conditions applying the formal theory of transformations for heterogeneous nucleation to the experimental data obtained by DSC using continuous-heating techniques. In addition, from dependence of the glass-transition temperature (T_g) on the heating rate, the activation energy for the glass transition was derived. Similarly the activation energy of the crystallization process was determined and the crystallization mechanism was characterized. The results reveal the increase of the activation energy for glass transition which was attributed to the increase in the rigidity, the cross-link density and the packing density of these glasses. The phases into which the glass crystallizes have been identified by X-ray diffraction. Diffractograms of the transformed material indicate the presence of microcrystallites of Li_0.30V₂O₅, Li_0.67O₅V₂, LiV₆O₁₅, Li₄O₄Pb, and O₇Pb₂V₂ in a remaining amorphous matrix.     

Ultrafast synthesis of Li1 + αV3O8 gel precursors for lithium battery applications

A versatile route has been developed to synthesize the Li_1 + αV₃O₈ gel precursor 50 times faster than the standard path without heating by using H₂O₂ and V₂O₅ and lithium salts as precursors. Upon heat treatment it leads to stoechiometric Li_1.1V₃O₈ with an electrochemical behavior similar to the one observed from the standard material. The role of the pH and the nature of the counter ion on the structural type and the morphology of the condensed Li_1 + αV₃O_8,nH₂O compound have been investigated. pH close to the zero charge point (≈ 2) lead to intercalated Li_xV₂O₅,nH₂O type gels whereas at pH 4 condensation drives to hewettite like structures.