Restrictions in silicon based anodes have been the subject of many researches for years. As an innovative approach, we have adopted ion assisted deposition technique to glancing angle deposition ...method and have used compositionally-graded structuring. A unique helical shaped gradient film has been produced in which the Cu/Si atomic ratio decreases from the bottom to the top of the coating. With such a unique film (high surface area) more spaces have been created promoting mechanical integrity and reaction between active materials (silicon) with lithium ions. The highly adherent film is formed as a result of ion assisted deposition process and the gradual change in Cu/Si atomic ratio diverts stress through the helices. To compare the performance of the SiCu electrode, a pure Si film is deposited in the same experimental condition. Galvanostatic test results show that although the film with pure Si helices fails after 30th cycles, the compositionally graded anode exhibits a capacity of 1228 mAh g−1 at the 100th cycles with 99.5% coulombic efficiencies when cycled at 100 mA g−1, and delivers 815 mAh g−1 when cycled with a rate of 400 mA g−1.
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•Highly adherent SiCu film is deposited by ion assisted glancing angle deposition.•Compositionally graded SiCu helical arrays is produced and characterized.•Change in Cu content along the thickness diverts the propagation of stress.•Cu rich layer at the bottom improves the adherence of the film.•Helices being like microsprings, improve the mechanical resistance of the anode.
Two nanocolumnar structured porous Cu–Sn films were produced by tuning the duration of the process using an oblique angle deposition (OAD) technique of electron beam coevaporation method. The ...structural and morphological properties of these porous Cu–Sn films are characterized using thin film X-ray diffraction, scanning electron microcopy (SEM) and atomic force microscopy (AFM). Galvanostatic half-cell electrochemical measurements were conducted in between 5 mV to 2.5 V using a Li counter electrode, demonstrating that the Cu rich Cu6Sn5 thin film having homogenously distributed nanocolumns achieved a good cycleability up to 100 cycles with a high capacity retention, whereas the Cu6Sn5 nanostructured porous thick film with inhomogeneous morphology showed only a very short cycle life (<25 cycles).The difference in the electrochemical performances of the thin and thick nanocolumnar structured porous Cu–Sn films resulting from different evaporation duration was evaluated on the basis of X-ray photoelectron spectroscopy (XPS) analysis on the cycled samples.
Nickel manganese cobalt oxide (NMCO) powders have been fabricated by hydrothermal method followed by a calcination. The present work reports for the first time in the open literature, the effects of ...ammonium fluoride (NH
4
F) amount and calcination temperature on the NMCO powder’s size and morphology. In this regard, the NMCO composite powders are designed to optimize their performances as anode materials for lithium ion batteries. The morphology, composition and structure of powders have been characterized by scanning electron microscopy, X-ray fluorescence and X-ray diffractometry, respectively. Cyclic voltammetry, galvanostatic and impedance spectroscopy tests have been employed to investigate the lithiation mechanism of the composite electrode. The results reveal that the lowest amount of NH
4
F (1.5 mmol) in the precursor solution and the lowest calcination temperature (250 °C) lead to form NMCO rods with 100 nm diameter and 3–5 µm length. This newly designed rod-shaped NMCO powder presents a high rate performance. The average discharge/charge capacities are 1224/1129, 968/939, 856/826, and 744/712 mAh g
−1
when the current load increases from 50 to 100, 200 and 400 mA g
−1
, respectively.
Graphic Abstract
Nanocolumnar composite Cu–Si films were produced as anodes using an oblique angle electron beam co-evaporation method. Two evaporation durations were used to yield different film thicknesses: thin ...(<250 ± 100 nm) and thick (>400 ± 100 nm). The structural and morphological properties of these Cu–Si films were characterized using X-ray diffraction and scanning electron microcopy. Galvanostatic half-cell electrochemical measurements were conducted over a voltage range of 50 mV–2.5 V using Li as a counter electrode and the Cu–Si films as anodes. The results demonstrated that the thin film has homogeneously distributed nanocolumns and yielded good cyclability upto 100 cycles with high capacity retention; by contrast, the thick film has an inhomogeneous porous structure and exhibited poor cyclability. The reason for the better electrochemical performance of the thin film was determined by X-ray photoelectron spectroscopy (XPS) at different states of charge. Moreover, in-situ electrodilatometric analysis during the galvanostatic test of the thin films measured the ongoing volumetric changes upon cycling.
•Well-aligned, ordered nanocolumnar CuSi thin film is formed via OAD method.•In-situ dilatometry is done to measure the expansion of the CuSi thin film anode.•Long evaporation duration leads broadening of the nanocolumns.•Homogeneous distributions of porosity and Cu enhance the cyclability of the Si.
An oblique angle electron beam co-deposition technique was used to fabricate nanostructured Sn-based thin films: Sn, Cu–Sn and Cu–Sn–C. The morphological and structural properties of the films were ...observed via scanning electron microscopy (SEM) and thin film X-ray diffraction (XRD) methods. The electrochemical (CV and EIS) and the galvanostatic test results demonstrated that the addition of Cu with or without C affected the electrochemical performance of the thin film positively since Cu and C improved both the mechanical and the electrical properties of the nanostructured Sn thin film electrode. The high cycleability and capacity retention were achieved when the nanostructured Cu–Sn–C thin film was used as an anode material since C increased the mechanical tolerance of the thin film to the volume expansion due to its grain refiner effect. Cu not only improved the electrical conductivity and the adhesion of the film to substrate but also the mechanical tolerance of the film with its ductile property.
In this work, well-aligned and ordered NiSi nano columnar arrays were fabricated using an ion assisted oblique angle deposition technique based on electron beam co-evaporation. It was demonstrated ...that these NiSi nano columnar arrays were promising high-capacity anode material for next generation lithium-ion batteries. Nano-structured Si films were also deposited and evaluated as anode material under the same experimental conditions for comparison. It was found that the dopant of about 9% wt. Ni in Si nano columns helped to improve the electrical conductivity and the electrochemical performance of the material. The electrochemical characterization showed that the well-aligned nano-columnar porous NiSi thin film delivered a very high reversible capacity (~1100mAhg−1) with almost no capacity fade for up to 100 cycles.
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•Ni and Si atoms were co-evaporated to form composite thin film.•Composite nano-columns were deposited on Cu substrate via OAD method.•High surface area, porosities and Ni presence improve the Si anode performance.•The reaction of the Ni–Si nano-sized particles with Li+ is highly reversible.
Sustaining a sound structure in Si-based anodes is extremely challenging because of the high volumetric expansion that occurs upon cycling. To maintain capacity retention during the cycling, there is ...a need for new designs that rely on engineering-specific hierarchical geometries and/or optimized composite compositions such that at least one of the multiple elements serves as buffer and/or electron conductive pathway in the electrodes. Here, we report an innovative design in which alternate layers of atomic structures involving multiple elements form a new anode material for lithium-ion batteries.
In this work, a superlattice-structured film containing Si, Mo, and Cu is fabricated by a simple and scalable magnetron sputtering process for the first time. With the help of the formation of a continuous and repetitive superlattice along the film thickness, a homogeneous stress-strain distribution is attained. In our superlattice thin film, the Si atoms are distributed along the film thickness within the alternate Mo–Cu layers, which act as inactive-conductive layers and as a backbone web to handle the volume expansion of active Si while restricting electrochemical agglomeration. This nano-functional superlattice approach enables harnessing the high energy density of Si while maintaining its structural stability. As a result, the electrode exhibits high energy density and capacity retention even at high cycling rates. The possible use of the film in a full cell is also evaluated using LiMn1.5Ni0.5O4 cathodes. The full cell maintained a stable capacity of about 900 mAh ganode−1 (~93 mA gcathode−1) over 150 cycles at the ~600 mA g−1 rate.
The remarkable performance of this nanostructured, multifunctional superlattice film is found to be promising for applications that require high energy, long calendar life, and excellent abuse tolerance, such as electric vehicle batteries.
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•A superlattice-structured amorphous film (Si, Mo, and Cu) is made using a scalable magnetron sputtering process for 1st time.•The Mo-Cu layer acts as an inactive-conductive layer and as a backbone to handle the volume expansion of active Si.•The electrode exhibits high specific capacity and capacity retention even at high cycling rates.
Although convolutional neural networks (CNNs) achieve high diagnostic accuracy for detecting Alzheimer's disease (AD) dementia based on magnetic resonance imaging (MRI) scans, they are not yet ...applied in clinical routine. One important reason for this is a lack of model comprehensibility. Recently developed visualization methods for deriving CNN relevance maps may help to fill this gap as they allow the visualization of key input image features that drive the decision of the model. We investigated whether models with higher accuracy also rely more on discriminative brain regions predefined by prior knowledge.
We trained a CNN for the detection of AD in N = 663 T1-weighted MRI scans of patients with dementia and amnestic mild cognitive impairment (MCI) and verified the accuracy of the models via cross-validation and in three independent samples including in total N = 1655 cases. We evaluated the association of relevance scores and hippocampus volume to validate the clinical utility of this approach. To improve model comprehensibility, we implemented an interactive visualization of 3D CNN relevance maps, thereby allowing intuitive model inspection.
Across the three independent datasets, group separation showed high accuracy for AD dementia versus controls (AUC ≥ 0.91) and moderate accuracy for amnestic MCI versus controls (AUC ≈ 0.74). Relevance maps indicated that hippocampal atrophy was considered the most informative factor for AD detection, with additional contributions from atrophy in other cortical and subcortical regions. Relevance scores within the hippocampus were highly correlated with hippocampal volumes (Pearson's r ≈ -0.86, p < 0.001).
The relevance maps highlighted atrophy in regions that we had hypothesized a priori. This strengthens the comprehensibility of the CNN models, which were trained in a purely data-driven manner based on the scans and diagnosis labels. The high hippocampus relevance scores as well as the high performance achieved in independent samples support the validity of the CNN models in the detection of AD-related MRI abnormalities. The presented data-driven and hypothesis-free CNN modeling approach might provide a useful tool to automatically derive discriminative features for complex diagnostic tasks where clear clinical criteria are still missing, for instance for the differential diagnosis between various types of dementia.
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