Showing papers on "FOIL method published in 2019"

Roll-to-roll prelithiation of Sn foil anode suppresses gassing and enables stable full-cell cycling of lithium ion batteries

Abstract: Tin foil should have outstanding volumetric capacity as a Li-ion battery anode; however, it suffers from an unacceptable initial coulombic efficiency (ICE) of 10–20%, which is much poorer than that of Si or SnO2 nanoparticles. Herein, we demonstrate that bare Sn catalyzes liquid electrolyte decomposition at intermediate voltages to generate gas bubbles and Leidenfrost gas films, which hinder lithium-ion transport and erode the solid–electrolyte interphase (SEI) layer. By metallurgically pre-alloying Li to make LixSn foil, the lower initial anode potential simultaneously suppresses gassing and promotes the formation of an adherent passivating SEI. We developed a universally applicable roll-to-roll mechanical prelithiation method and successfully prelithiated Sn foil, Al foil and Si/C anodes. The as-prepared LixSn foil exhibited an increased ICE from 20% to 94% and achieved 200 stable cycles in LiFePO4//LixSn full cells at ∼2.65 mA h cm−2. Surprisingly, the LixSn foil also exhibited excellent air-stability, and its cycling performance sustained slight loss after 12 h exposure to moist air. In addition to LiFePO4, the LixSn foil cycled well against a lithium nickel cobalt manganese oxide (NMC) cathode (4.3 V and ∼4–5 mA h cm−2). The volumetric capacity of the LixSn alloy in the LFP//LixSn pouch cell was up to ∼650 mA h cm−3, which is significantly better than that of the graphite anode on a copper collector, with a rate capability as high as 3C.

Plasma-Strengthened Lithiophilicity of Copper Oxide Nanosheet-Decorated Cu Foil for Stable Lithium Metal Anode.

Abstract: Lithium metal is the most ideal anode for next-generation lithium-ion batteries. However, the formation of lithium dendrites and the continuous consumption of electrolyte during cycling lead to a serious safety problems. Developing stable lithium metal anode with uniform lithium deposition is highly desirable. Herein, a nitrogen plasma strengthening strategy is proposed for copper oxide nanosheet-decorated Cu foil as an advanced current collector, and deep insights into the plasma regulating mechanism are elaborated. The plasma-treated electrode can maintain a high coulombic efficiency of 99.6% for 500 cycles. The symmetric cell using the lithium-plated electrode can be cycled for more than 600 h with a low-voltage hysteresis (23.1 mV), which is much better than those of electrodes without plasma treatment. It is well confirmed that this plasma-induced nitrogen doping method can provide sufficient active sites for lithium nucleation to enhance the stability of lithium deposition on copper oxide nanosheets decorated on Cu foil and improve the electrical conductivity to greatly reduce the overpotential of the lithium nucleation, which can be extended to other modified current collectors for stable lithium metal anode.

Efficient Separation of Aluminum Foil and Cathode Materials from Spent Lithium-Ion Batteries Using a Low-Temperature Molten Salt

Abstract: The effective separation of aluminum (Al) foil and cathode materials is a critical issue for the recycling of spent lithium-ion batteries (LIBs). Previous studies have shown that the strong binding...

Ultrafast growth of nanocrystalline graphene films by quenching and grain-size-dependent strength and bandgap opening.

Abstract: Nanocrystallization is a well-known strategy to dramatically tune the properties of materials; however, the grain-size effect of graphene at the nanometer scale remains unknown experimentally because of the lack of nanocrystalline samples. Here we report an ultrafast growth of graphene films within a few seconds by quenching a hot metal foil in liquid carbon source. Using Pt foil and ethanol as examples, four kinds of nanocrystalline graphene films with average grain size of ~3.6, 5.8, 8.0, and 10.3 nm are synthesized. It is found that the effect of grain boundary becomes more pronounced at the nanometer scale. In comparison with pristine graphene, the 3.6 nm-grained film retains high strength (101 GPa) and Young’s modulus (576 GPa), whereas the electrical conductivity is declined by over 100 times, showing semiconducting behavior with a bandgap of ~50 meV. This liquid-phase precursor quenching method opens possibilities for ultrafast synthesis of typical graphene materials and other two-dimensional nanocrystalline materials. Nano-crystallization is essential to tune different properties of materials. Here, the authors report a synthesis strategy that involves quenching of a hot metal foil for few seconds in liquid carbon source to form graphene films of 3.6 nm grain size, showing mechanical strength of 101 GPa and semiconducting behaviour.

Sn‐Alloy Foil Electrode with Mechanical Prelithiation: Full‐Cell Performance up to 200 Cycles

Abstract: DOI: 10.1002/aenm.201902150 to tens of micrometers thickness), excellent electrical conductivity, and initially high density (7.28 g cm−3). But curiously, metallic foil anodes are rarely reported in the literature, except for the pure Li metal foil. Most reports about Sn↔LixSn based anode focused on nanoparticles of Sn or SnO2. In the few works on Sn foil or Sn-based thin film prepared by costly electron-beam deposition or magnetron sputtering, the performance seems not attractive. For example, 15 μm pure tin foil electrode reported by Yang et al.[3] in 2003 showed a rapid capacity decay just after ten deep cycles and then the electrode had pulverized to black mud-like materials. In addition to mechanical failure caused by pulverization, the extremely low initial Coulombic efficiency (ICE) of metallic foil anode is another tough problem. Theoretically, since the initial surface area of dense tin foil is far smaller than that of tin nanoparticles (>103× initial contact area with the electrolyte), the electrolyte decomposition is supposed to be greatly reduced and thus ICE is expected to be better.[4–6] However, the actual results are perplexing. In 2005, Hu et al.[7] had showed that ICE of Sn-Cu thin film anode prepared by electron-beam evaporation deposition was 84%, which is similar to that of nano-architectured Sn anodes,[8,9] while the ICE of annealed Sn-Cu thin film that has a more compact structure and larger grains was actually 30%, opposite to what one might have expected.[7,10,11] Similar result that the ICE of dense Sn foil is surprisingly low to 10% to 20% also was found in our previous work[12] and Figure S1 in the Supporting Information. We had explored the reason in previous work and found the low ICE is caused by the serious foil pulverization and obvious catalytic effect of Sn metal on the decomposition of electrolyte.[12] In practical full cells, to cope with the cyclable lithium loss, anode prelithiation is necessary.[13] Common prelithiation methods such as electrical shorting and chemical routes[14–17] could create excess inventory to prepare for the future loss of cyclable lithium, but the prelithiation process is usually complex and has difficulty scaling up industrially. Pure Li metal can react with Sn through direct contact. Taking advantage of this, we designed a facile mechanical prelithiation method, which does not require organic electrolyte or expensive equipment, where the reaction time is sped up by Self-supporting Sn foil is a promising high-volumetric-capacity anode for lithium ion batteries (LIBs), but it suffers from low initial Coulombic efficiency (ICE). Here, mechanical prelithiation is adopted to improve ICE, and it is found that Sn foils with coarser grains are prone to cause electrode damage. To mitigate damage and prepare thinner lithiated electrodes, 3Ag0.5Cu96.5Sn foil is used that has more refined grains (5–10 μm) instead of Sn (50–100 μm), where the abundant grain boundaries (GBs) offer more sliding systems to release stress and reduce deep fractures. Thus, the thickness of Lix3Ag0.5Cu96.5Sn can be reduced to 50 μm, compared to 100 μm LixSn. When the foils contact open air, the Sn-Li-O(H) products are more stable than Li-O(H), thus Lix3Ag0.5Cu96.5Sn shows outstanding air stability. The as-prepared 50 μm foil anode achieves stable 200 cycles in LiFePO4//Lix3Ag0.5Cu96.5Sn full cell (≈2.65 mAh cm−2) and the capacity retention is 95%. Even at 5C, the capacity of Lix3Ag0.5Cu96.5Sn is still up to ≈1.8 mAh cm−2. The cycle life of NCM523//Lix3Ag0.5Cu96.5Sn full cell exceeds that of NCM523//Li. Furthermore, 70 μm Lix3Ag0.5Cu96.5Sn is used as double-sided anode for a 3 cm × 2.8 cm pouch cell and its actual volumetric capacity density is 674 mAh cm−3 after 50 cycles.

Suppressing Corrosion of Aluminum Foils via Highly Conductive Graphene-like Carbon Coating in High-Performance Lithium-Based Batteries

Abstract: Aluminum foil is the predominant cathodic current collector in lithium-based batteries due to the high electronic conductivity, stable chemical/electrochemical properties, low density, and low cost. However, with the development of next-generation lithium batteries, Al current collectors face new challenges, such as the requirement of increased chemical stability at high voltage, long-cycle-life batteries with different electrolyte systems, as well as improved electronic conductivity and adhesion for new electrode materials. In this study, we demonstrate a novel graphene-like carbon (GLC) coating on the Al foil in lithium-based batteries. Various physical and electrochemical characterizations are conducted to reveal the electronic conductivity and electrochemical stability of the GLC-Al foil in both carbonate- and ether-based electrolytes. Full-cell tests, including Li-S batteries and high-voltage Li-ion batteries, are performed to demonstrate the significantly improved cycling and rate performance of batteries with the use of the GLC-Al foil as current collectors. The cell using the GLC-Al foil can greatly reduce the potential polarization in Li-S batteries and can obtain a reversible capacity of 750 mAh g-1 over 100 cycles at 0.5C. Even with high-sulfur-loading cathodes, the Li-S battery at 1C still maintains over 500 mAh g-1 after 100 cycles. In high-voltage Li-ion batteries, the GLC-Al foil significantly improves the high-rate performance, showing an increased retained capacity by over 100 mAh g-1 after 450 cycles at 1C compared to the bare foil. It is believed that the developed GLC-Al foil brings new opportunities to enhance the battery life of lithium-based batteries.

Ultrathin Al foils to fabricate dendrite-free Li–Al anodes

Abstract: Current research has made great progress on lithium dendrite issues by electrolyte and/or electrode engineering, but such modifications usually cause severe capacity loss due to the introduction of extra species in the cells. Herein, ultrathin aluminum foil has been employed to in situ fabricate a Li–Al alloy onto lithium metal as a protection layer. The nanoscale foil has an average thickness of only ∼160 nm and an areal mass of 0.3 mg cm−2. The composite anodes with such a protection layer exhibit significant improvement in cycling stability either in symmetrical cells or in full cells by effectively regulating the lithium plating and alloying behaviors to avoid dendritic morphologies at high plating currents and capacities. Different characterization techniques confirm uniform lithium deposition onto the Li–Al alloy surface. Meanwhile, the protection layer also serves as a buffer to alleviate volume variation during cycling. The straightforward integration of ultrathin low-cost metal foil into a lithium anode is a very competitive strategy for the practical development of lithium metal batteries.

A renewable, flexible and robust single layer nitrogen-doped graphene coating Sn foil for boosting formate production from electrocatalytic CO2 reduction

Abstract: Herein, we develop a general method to stabilize and improve the electrochemical performances of commercial bulk Sn foil by coating single layer nitrogen-doped graphene (SL-NG@Sn foil) for electroreduction of CO2 to formate. The maximum Faradaic Efficiency (FE) for formate attained by SL-NG@Sn foil is 92.0% at −1.0 V (vs. RHE) in 0.5 M KHCO3 with high formate partial current density of 21.3 mA cm−2, outperforming other reported Sn nanoparticles-based catalysts. The SL-NG@Sn foil displays good flexibility, which achieve similar performance after folding. It also possesses good renewable ability that can be recycled used after simply washing with water for three usages with FE above 90%. An interesting transformation of reaction mechanism to higher kinetic activity is observed at SL-NG@Sn foil, demonstrating the synergistic effect exists between SL-NG and Sn foil.

The Role and Control of Residual Bulk Oxygen in the Catalytic Growth of 2D Materials

Abstract: We systematically study the effects of residual oxygen in the bulk of Cu foil catalysts on the chemical vapor deposition (CVD) of graphene. While oxidation is widely used to remove impurities in me...

Hexagonal Boron Nitride Nanosheets Grown via Chemical Vapor Deposition for Silver Protection

Abstract: In this study, hexagonal boron nitride nanosheets (h-BNNS) have been grown on polycrystalline silver substrates via chemical vapor deposition (CVD) using ammonia borane as a precursor. The h-BNNS are of few-atomic-layer thickness and form continuous coverage over the whole Ag substrate. The atomically thin coating poses negligible interference to the reflectivity in the UV–visible range. The nanosheet coating also proves very effective in protecting Ag foil chemically. In contrast to bare Ag foil, the coated foil displayed only minor decolorization under high concentration of H2S. The study indicates that h-BNNS can be a promising protective coating for Ag based items such as jewelry or mirrors used in astronomical telescopes.

Flexible high-efficiency CZTSSe solar cells on stainless steel substrates

Abstract: Stainless steel (SS) foil is made of abundant materials and is a durable and flexible substrate, but the efficiency of a solar cell on SS foil deteriorates via the diffusion of impurities from the SS substrate into a Cu2ZnSn(S,Se)4 (CZTSSe) absorber layer. In this work, the properties of the diffusion barrier for CZTSSe solar cells is investigated by X-ray diffraction (XRD), secondary ion mass spectrometry (SIMS), and scanning electron microscopy (SEM). The industrially relevant oxide materials ZnO and SiO2 are used as diffusion barriers against impurities. The formation of a ZnSe reaction with Se degrades the barrier properties of the ZnO barrier layer. As a result, ZnO fails to act as a diffusion barrier, and Fe is observed in the absorber layer. On the other hand, the intrinsic diffusion barrier properties of SiO2 are superior to those of ZnO, and SiO2 is a stable diffusion barrier even after selenization. Therefore, SiO2 was applied to flexible solar cells, and a power conversion efficiency of 10.30%, the highest efficiency for CZTSSe on SS foil, was obtained.

Energy extraction properties of a flapping wing with an arc-deformable airfoil

Abstract: The active synchronous deformation in the arc length of an airfoil employed in a flapping wing can improve its energy extraction efficiency. The present study seeks to understand the underlying physics of this energy extraction by conducting transient numerical simulations of a novel arc-deformable flapping foil design based on dynamic mesh technology and a relative heaving motion reference system. The influence of the flapping frequency and the pitching amplitude on the energy extraction efficiency of the flapping foil modeled under a constant arc length is investigated. The effects of the deformation magnitude β and the position of the deformation center on the energy extraction efficiency are also examined at a constant flapping frequency and pitching amplitude. The results show that active synchronous arc deformation can greatly improve the energy extraction efficiency of a flapping foil compared to the efficiency of a conventional non-deformable flapping foil design. In addition, the results provide sets of optimal flapping frequencies and pitching amplitudes for the deformable flapping foil design with fixed deformation parameters and the non-deformable foil design that obtains the highest energy extraction efficiencies. A single high efficiency zone is obtained for the deformable foil design at a relatively high flapping frequency. In contrast, relatively high efficiency zones are obtained for the non-deformable foil design at both a relatively low flapping frequency and a high flapping frequency. The energy extraction efficiency of the deformable flapping foil first increases with increasing β up to a maximum value of β = 0.25 and then decreases with a further increase in β. The energy extraction efficiency of the deformable flapping foil is also demonstrated to increase as the deformation center moves from the leading edge of the foil to the trailing edge, attaining a maximum value when the deformation center coincides with the center of the pitching axis, and then decreases.