Fe/Si multi-layer thin film anodes for lithium rechargeable thin film batteries

Fe/Si multi-layer thin films were prepared by alternate deposition using an electron-beam evaporation method. Electrochemical results through galvanostatic charge–discharge experiments are presented. It appears that the volumetric expansion of silicon during cycling can be effectively suppressed by forming a Fe layer between Si layers. The electrochemical characteristics of Fe/Si multi-layer film electrode can be controlled by the thickness, and number of stacked Si layers, and post-annealing.     

全固态薄膜锂/锂离子电池的研究进展

本文介绍了全固态薄膜锂/锂离子电池发展;对全固态薄膜锂/锂离子电池最近的研究进展进行了综述分析,并指出了今后研究的方向。     

Integrated lithium metal anode protected by composite solid electrolyte film enables stable quasi-solid-state lithium metal batteries

Lithium (Li) metal, possessing an extremely high theoretical specific capacity (3860 mAh/g) and the most negative electrode potential (−3.040 V vs. standard hydrogen electrode), is one the most favorable anode materials for future high-energy-density batteries. However, the poor cyclability and safety issues induced by extremely unstable interfaces of traditional liquid Li metal batteries have limited their practical applications. Herein, a quasi-solid battery is constructed to offer superior interfacial stability as well as excellent interfacial contact by the incorporation of Li@composite solid electrolyte integrated electrode and a limited amount of liquid electrolyte (7.5 μL/cm²). By combining the inorganic garnet Al-doped Li_6.75La₃Zr_1.75Ta_0.25O₁₂ (LLZO) with high mechanical strength and ionic conductivity and the organic ethylene-vinyl acetate copolymer (EVA) with good flexibility, the composite solid electrolyte film could provide sufficient ion channels, sustained interfacial contact and good mechanical stability at the anode side, which significantly alleviates the thermodynamic corrosion and safety problems induced by liquid electrolytes. This innovative and facile quasi-solid strategy is aimed to promote the intrinsic safety and stability of working Li metal anode, shedding light on the development of next-generation high-performance Li metal batteries.     

Alkaline composite film as a separator for rechargeable lithium batteries

We report a new type of separator film for application in rechargeable lithium and lithium-ion batteries. The films are made of mainly alkaline calcium carbonate (CaCO₃) and a small amount of polymer binder. Owing to porosity and capillarity, the composite films show excellent wettability with non-aqueous liquid electrolytes. Typically, the composite films composed of CaCO₃ and Teflon and wetted with 1 M LiPF₆ dissolved in a solvent mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) (30:70 wt%) exhibit an ionic conductivity as high as 2.5–4 mS/cm at 20 °C, in a comparable range with that (3.4 mS/cm) of the commercial Celgard membrane. In the batteries, the composite film not only serves as a physical separator but also neutralizes acidic products, such as HF formed by LiPF₆ hydrolysis, as well as those formed by solvent oxidative decomposition. A Li/LiMn₂O₄ test cell was employed to examine the electrochemical compatibility of the composite film. We observed that the composite film cell showed an improved cycling performance since the alkaline CaCO₃ neutralizes the acidic products, which otherwise promote dissolution of the electrode active materials. More importantly, the composite film cell displayed a superior performance on high-rate cycling, which was probably the result of the less resistive interface formed between the electrode and the composite film.     

Anomalous lithium ion diffusion into CeO2·TiO2 thin film by film thickness variations

CeO₂·TiO₂ thin film is considered as an excellent candidate for a passive ion storage layer due to its good electrochemical stability and comparatively great charge capacitance. When cerium-titanium oxide thin film is adopted as an ion storage layer against cathodic tungsten oxide layer, the electrochromic device shows long term durability and cyclability. Therefore, many researchers investigated the composition and crystallinity effects to the charge density. In our study, we prepared CeO₂·TiO₂ thin by sol–gel dip-coating method, varying thickness by controlling withdrawal speeds. As investigating results of cyclic voltammetry and chronocoulometry, we found that there are three regions in the film thicknesses: (1) fast lithium ion diffusion region under 100 nm, (2) slow diffusion region in the range of 100 to 150 nm, and (3) fast and great charge capacitance region over 150 nm. In region 1, lithium ions diffuse very fast and reach into indium-tin oxide (ITO) layers, and slow diffusion region follows in region 2, probably due to the remains or impurities within the film, and in region 3, lithium ion diffusion gets fast again, accompanied with charge capacitance increase with thickness.     

Proton and carbon-13 chemical shifts: Comparison between theory and experiment

A series of ab initio ¹H and ¹³C NMR chemical shifts are presented for all molecules for which gas-phase experimental measurements exist. Quantitative agreement with this large set of data is achieved by the use of gauge-invariant atomic orbitals in an SCF perturbation theory approach. The effect of basis set completeness on these ¹H and ¹³C chemical shifts is also examined. The 4-31G basis set is found to provide internally consistent results and give satisfactory agreement with gas-phase experimental data. Errors within 6% for ¹H shifts and 3% for ¹³C shifts result. Increasing the basis set to the 6-31G^* level does not significantly improve the agreement. For ¹H shifts only, the 3-21G basis set is adequate. The validity of the particular computational approach employed here is further substantiated by comparison to another ab initio magnetic shielding method.     

Distribution of three ions in the thin film experiment

In the theoretical model it is assumed that a graphite disk electrode is covered by a thin film of the solution of decamethylferrocene and some supporting electrolyte in nitrobenzene and immersed in an aqueous solution of the same electrolyte. Oxidation of decamethylferrocene is accompanied by the transfer of anions of the electrolyte from water into nitrobenzene. The flux of decamethylferrocenium cations at the electrode surface and the flux of anions at the liquid/liquid interface are separated by the thickness of the film, but the electroneutrality is ensured by the migration of ionic species through the film. Theoretical concentration profiles of ionic species in the film are reported for cyclic voltammetry.     

Proton and lithium cation affinities calculated with floating orbital geometry optimization (FOGO)

The FOGO method is used to calculate proton affinities and lithium cation affinities. The molecules of primary interest in this study are the methyl-substituted amines. In addition, the lithium cation affinity of HF, H₂O, CH₃OH, H₂CO, and HCN are calculated for comparison. Geometries of all species are fully optimized with a double-zeta (DZ) basis set, including polarization on hydrogen and the first-row elements by floating orbitals. Comparison with experimental values demonstrates that structural data and proton affinities resulting from this type of ab initio calculation are of chemical accuracy. The lithium cation affinities are also reasonably well reproduced, but the small experimental differences are not within the accuracy, which can be expected from this type of calculation.     

Surface film formation on graphite negative electrodes in rechargeable lithium batteries

The choice of solvent is quite important to obtain good protecting surface film on graphite negative electrodes in rechargeable lithium batteries. A subtle difference of the molecular structure of solvent greatly affects the easiness of surface film formation. In order to understand the solvent effects and to elucidate the mechanism of surface film formation, morphology changes of the basal plane of highly oriented pyrolytic graphite were studied using electrochemical scanning tunneling microscopy (EC‐STM). In this article, our recent results of EC‐STM observation in different solvent systems are reviewed.     

Enhancement of thin film tin oxide negative electrodes for lithium batteries

Thin films of pure SnO₂, of the Sn/Li₂O layered structure, and of Sn/Li₂O were fabricated by sputtering method, while a `lithium-reacted tin oxide thin film' was assembled by the evaporation of lithium metal onto a SnO₂ thin film. Film structure and charge/discharge characteristics were compared. The lithium-reacted tin oxide thin film, the Sn/Li₂O layered structure, and the Sn/Li₂O co-sputtered thin films did not show any irreversible side reactions of forming Li₂O and metallic Sn near 0.8 V vs Li/Li⁺. The initial charge retention of the Sn/Li₂O layered structure and Sn/Li₂O co-sputtered thin films was about 50% and a similar value was found for the lithium-reacted tin oxide thin film (more than 60%). Sn/Li₂O layered structure and Sn/Li₂O co-sputtered thin films showed better cycling behavior over 500 cycles than the pure SnO₂ and lithium-reacted tin oxide thin film in the cut-off range from 1.2 to 0 V vs Li/Li⁺.     

Investigation of the structure of silk film regenerated with lithium thiocyanate solution

The Silk fibers of the mulberry (Bombyx Mori) were dissolved in a 70% lithium thiocyanate solution. Dissolved silk was regenerated by casting the films from the solution after dialyzing. The films were investigated by infrared (IR) spectroscopy and x-ray diffraction analysis. It was found that the freshly prepared film was amorphous. The transformation to the β-form could be brought about by heating, solvent induced crystallization, ultraviolet (UV) radiation, and prolonged storage. The mechanism of this transformation is discussed.     

Net-like SnS/carbon nanocomposite film anode material for lithium ion batteries

SnS particles with sizes of 5.0–6.5 nm were prepared by a facile method. Resorcinol–formaldehyde sol with addition of the as-prepared SnS nanoparticles was spin-coated on a copper foil to prepare net-like SnS/C composite thin-film electrode for lithium ion batteries after carbonization at 650 °C. The SnS/C nanocomposite thin-film electrode showed preferable first coulombic efficiency and excellent cycling stability. The discharge and charge capacities were respectively 542.3 and 531.3 mAh/g after 40 cycles. The attractive electrochemical performances were mainly ascribed to the ultra fine particle, which showed no evident aggregation in high-resolution TEM image, and the effects of 3-dimensional net-like carbon structure, which uniformly surrounded the SnS nanoparticles to guarantee the contact, acted as a buffer matrix to alleviate the volume expansion of Li–Sn alloy and provided enough paths for electrolyte to reach SnS active material during discharge–charge process.     

Electrochemical performance of all-solid lithium ion batteries with a polyaniline film cathode

We have prepared a high-density polyaniline(PANI) paste(50 mg/m L), with similar physical properties to those of paints or pigments. The synthesis of PANI is confirmed by Fourier transform infrared(FT-IR) spectroscopy. The morphologies of PANI, doped PANI, and doped PANI paste are confirmed by scanning electron microscopy(SEM). Particles of doped PANI paste are approximately 40–50 nm in diameter, with a uniform and cubic shape. The electrochemical performances of doped PANI paste using both liquid and solid polymer electrolytes have been measured by galvanostatic charge and discharge process. The cell fabricated with doped PANI paste and the solid polymer electrolyte exhibits a discharge capacity of ～87 μAh/cm2(64.0 m Ah/g) at the second cycle and～67 μAh/cm2(50.1 m Ah/g) at the 100 th cycle.     

Nanocrystalline MnO thin film anode for lithium ion batteries with low overpotential

Nanocrystalline MnO thin film has been prepared by a pulsed laser deposition (PLD) method. The reversible lithium storage capacity of the MnO thin film electrodes at 0.125C is over 472 mAh g^?1 (3484 mAh cm^?3) and can be retained more than 90% after 25 cycles. At a rate of 6C, 55% value of the capacity at 0.125C rate can be obtained for both charge and discharge. As-prepared MnO thin film electrodes show the lowest values of overpotential for both charge and discharge among transition metal oxides. All these performances make MnO a promising high capacity anode material for Li-ion batteries.     

Effect of electric field on lithium ion in silicene channel. Computer experiment

The molecular dynamics method is used to study the drift of Li⁺ ions exposed to electric interactions in a planar channel formed by silicene sheets. The character of dynamics of the ion and also its effect on mechanical properties of silicene sheets are used to determine the optimum size of the planar channel clearance. Instability of the surface (4 × 4) structure of free bilayer silicene is demonstrated. Mobilities of Si atoms and distributions of the main stresses in silicene appearing in the course of lithium ion movement along the channel are calculated.     

Structural properties of lithium thio-germanate thin film electrolytes grown by radio frequency sputtering

In this study, lithium thio-germanate thin film electrolytes have been successfully prepared by radio frequency (RF) magnetron sputtering deposition in Ar gas atmospheres. The targets for RF sputtering were prepared by milling and pressing appropriate amounts of the melt-quenched starting materials in the nLi(2)S + GeS(2) (n = 1, 2, and 3) binary system. Approximately 1 μm thin films were grown on Ni coated Si (Ni/Si) substrates and pressed CsI pellets using 50 W power and 25 mtorr (～3.3 Pa) Ar gas pressures to prepare samples for Raman and Infrared (IR) spectroscopy, respectively. To improve the adhesion between the silicon substrate and the thin film electrolyte, a sputtered Ni layer (～120 nm) was used. The surface morphologies and thickness of the thin films were determined by field emission scanning electron microscopy (FE-SEM). The structural properties of the starting materials, target materials, and the grown thin films were examined by X-ray diffraction (XRD), Raman, and IR spectroscopy.     

Nickel foam-supported porous NiO/polyaniline film as anode for lithium ion batteries

Nickel foam-supported porous NiO film was prepared by a chemical bath deposition technique, and the NiO/polyaniline (PANI) film was obtained by depositing the PANI layer on the surface of the NiO film. The NiO film was constructed by NiO nanoflakes, and after the deposition of PANI, these nanoflakes were coated by PANI. As an anode for lithium ion batteries, the NiO/PANI film exhibits weaker polarization as compared to the NiO film. The specific capacity after 50 cycles for NiO/PANI film is 520 mAh g⁻¹ at 1 C, higher than that of NiO film (440 mAh g⁻¹). The improvement of these properties is attributed to the enhanced electrical conduction and film stability of the electrode with PANI.     

Irreversible processes during the lithium intercalation into graphite: the passive film formation

Comparative studies of three type of carbonaceous materials—the modified oxidized graphite, thermoexpanded graphite, and carbon paper—prior to and after galvanostatic cycling in 1 M LiClO₄ solution in propylene carbonate-dimethoxyethane mixture are carried out using standard porosimetry. It was shown that the mean (effective) thickness of the passive film [solid electrolyte interface (SEI)] at the electrodes of the modified oxidized graphite and thermoexpanded graphite equals a few nanometers. The comparison of porosimetric and electrochemical data shows that the passive film comprises both lithium carbonate and alkylcarbonates. Additionally, this comparison allows corroborating the concept on the formation of polymer (or oligomer) component of the passive film at least at the thermoexpanded graphite electrodes.