The increasing demand for higher‐energy‐density batteries driven by advancements in electric vehicles, hybrid electric vehicles, and portable electronic devices necessitates the development of ...alternative anode materials with a specific capacity beyond that of traditional graphite anodes. Here, the state‐of‐the‐art developments made in the rational design of Si‐based electrodes and their progression toward practical application are presented. First, a comprehensive overview of fundamental electrochemistry and selected critical challenges is given, including their large volume expansion, unstable solid electrolyte interface (SEI) growth, low initial Coulombic efficiency, low areal capacity, and safety issues. Second, the principles of potential solutions including nanoarchitectured construction, surface/interface engineering, novel binder and electrolyte design, and designing the whole electrode for stability are discussed in detail. Third, applications for Si‐based anodes beyond LIBs are highlighted, specifically noting their promise in configurations of Li–S batteries and all‐solid‐state batteries. Fourth, the electrochemical reaction process, structural evolution, and degradation mechanisms are systematically investigated by advanced in situ and operando characterizations. Finally, the future trends and perspectives with an emphasis on commercialization of Si‐based electrodes are provided. Si‐based anode materials will be key in helping keep up with the demands for higher energy density in the coming decades.
The major challenges, state‐of‐the‐art developments on rational structure design strategies, surface/interface engineering, industrial anode/cathode selection, and advanced in situ/operando characterizations toward deep understanding of the working mechanism of Si‐based electrodes are reviewed. It is demonstrated that Si‐based anodes are promising candidates in configurations of lithium‐ion batteries, Li–S batteries, all‐solid‐state batteries, and beyond.
The irregular domain and lack of ordering make it challenging to design deep neural networks for point cloud processing. This paper presents a novel framework named
Point Cloud Transformer
(PCT) for ...point cloud learning. PCT is based on Transformer, which achieves huge success in natural language processing and displays great potential in image processing. It is inherently permutation invariant for processing a sequence of points, making it well-suited for point cloud learning. To better capture local context within the point cloud, we enhance input embedding with the support of farthest point sampling and nearest neighbor search. Extensive experiments demonstrate that the PCT achieves the state-of-the-art performance on shape classification, part segmentation, semantic segmentation, and normal estimation tasks.
By leveraging deep learning-based technologies, industrial artificial intelligence (IAI) has been applied to solve various industrial challenging problems in Industry 4.0. However, for privacy ...reasons, traditional centralized training may be unsuitable for sensitive data-driven industrial scenarios, such as healthcare and autopilot. Recently, federated learning has received widespread attention, since it enables participants to collaboratively learn a shared model without revealing their local data. However, studies have shown that, by exploiting the shared parameters adversaries can still compromise industrial applications such as auto-driving navigation systems, medical data in wearable devices, and industrial robots' decision making. In this article, to solve this problem, we propose an efficient and privacy-enhanced federated learning (PEFL) scheme for IAI. Compared with existing solutions, PEFL is noninteractive, and can prevent private data from being leaked even if multiple entities collude with each other. Moreover, extensive experiments with real-world data demonstrate the superiority of PEFL in terms of accuracy and efficiency.
Humans can naturally and effectively find salient regions in complex scenes. Motivated by this observation, attention mechanisms were introduced into computer vision with the aim of imitating this ...aspect of the human visual system. Such an attention mechanism can be regarded as a dynamic weight adjustment process based on features of the input image. Attention mechanisms have achieved great success in many visual tasks, including image classification, object detection, semantic segmentation, video understanding, image generation, 3D vision, multimodal tasks, and self-supervised learning. In this survey, we provide a comprehensive review of various attention mechanisms in computer vision and categorize them according to approach, such as channel attention, spatial attention, temporal attention, and branch attention; a related repository
https://github.com/MenghaoGuo/Awesome-Vision-Attentions
is dedicated to collecting related work. We also suggest future directions for attention mechanism research.
Attention mechanisms, especially self-attention, have played an increasingly important role in deep feature representation for visual tasks. Self-attention updates the feature at each position by ...computing a weighted sum of features using pair-wise affinities across all positions to capture the long-range dependency within a single sample. However, self-attention has quadratic complexity and ignores potential correlation between different samples. This article proposes a novel attention mechanism which we call external attention , based on two external, small, learnable, shared memories, which can be implemented easily by simply using two cascaded linear layers and two normalization layers; it conveniently replaces self-attention in existing popular architectures. External attention has linear complexity and implicitly considers the correlations between all data samples. We further incorporate the multi-head mechanism into external attention to provide an all-MLP architecture, external attention MLP (EAMLP), for image classification. Extensive experiments on image classification, object detection, semantic segmentation, instance segmentation, image generation, and point cloud analysis reveal that our method provides results comparable or superior to the self-attention mechanism and some of its variants, with much lower computational and memory costs.
For the currently most dominant cathode of Li(NixCoyMnz)O2(NCM, x + y + z = 1) in lithium‐ion batteries, higher nickel content brings higher energy density but is accompanied by heavier interfacial ...reactions with electrolyte and worse safety performance. Single crystal cathode materials have the advantages of fewer grain boundaries, higher density, and greatly suppressed microcracks during cycling, these benefits in turn suppress interfacial side reactions, as well as the improve volumetric energy density and safety performance. Here, a strategy of pulse high‐temperature sintering (PHTS) is reported to prepare single‐crystal Li(Ni0.9Co0.05Mn0.05)O2 (SC‐NCM90), in which an extra PHTS at 1040 °C for 1 min is added in the traditional calcination process at 750 °C, yielding well defined octahedral particles with an initial capacity of 209 mAh g−1. Compared with the counterpart NCM90 secondary spheres, the tap density of SC‐NCM90 increases by 1/3 to 2.76 g cm−3 and the microcracks are successfully suppressed, improving both the cycling performance and thermal stability. The calcination time and temperature are optimized, showing that overlong time or overhigh temperature of the PHTS treatment would result in particles with better defined octahedral shape but heavier Li/Ni intermixing and capacity loss.
A pulse high temperature sintering strategy is developed for the preparation of single crystal high nickel NCM(LiNixCoyMn1–x–yO2), without using a fluxing agent or changing the current production line. With the help of the single crystal NCM, tap density is increased by 1/3 and the internal micro‐cracks are effectively suppressed, improving cycling life and safety performance.
Podophyllotoxin is an aryltetralin lignan lactone derived from different plants of Podophyllum. It consists of five rings with four chiral centers, one trans‐lactone and one aryl ...tetrahydronaphthalene skeleton with multiple modification sites. Moreover, podophyllotoxin and its derivatives showed lots of bioactivities, including anticancer, anti‐inflammatory, antiviral, and insecticidal properties. The demand for podophyllotoxin and its derivatives is rising as a result of their high efficacy. As a continuation of our previous review (Chem. Eur. J., 2017, 23, 4467–4526), herein, total synthesis, biotransformation, structural modifications, bioactivities, and structure–activity relationships of podophyllotoxin and its derivatives from 2017 to 2022 are summarized. Meanwhile, a piece of update information on the origin of new podophyllotoxin analogues from plants from 2014 to 2022 was compiled. We hope that this review will provide a reference for future high value–added applications of podophyllotoxin and its analogues in the pharmaceutical and agricultural fields.
Podophyllotoxin is a natural product with interesting medicinal and agricultural values. Herein, new podophyllotoxin analogues with new skeletons isolated from plants are listed, as well as the total synthesis, structural modifications, biological activity and structure–activity relationships of podophyllotoxin and its derivatives. Hopefully, this review will serve as a reference for further research on podophyllotoxin and its derivatives.
The application of solid polymer electrolytes (SPEs) in all‐solid‐state(ASS) batteries is hindered by lower Li+‐conductivity and narrower electrochemical window. Here, three families of ester‐based ...F‐modified SPEs of poly‐carbonate (PCE), poly‐oxalate (POE) and poly‐malonate (PME) were investigated. The Li+‐conductivity of these SPEs prepared from pentanediol are all higher than the counterparts made of butanediol, owing to the enhanced asymmetry and flexibility. Because of stronger chelating coordination with Li+, the Li+‐conductivity of PME and POE is around 10 and 5 times of PCE. The trifluoroacetyl‐units are observed more effective than −O−CH2−CF2−CF2−CH2−O− during the in situ passivation of Li‐metal. Using trifluoroacetyl terminated POE and PCE as SPE, the interfaces with Li‐metal and high‐voltage‐cathode are stabilized simultaneously, endowing stable cycling of ASS Li/LiNi0.6Co0.2Mn0.2O2 (NCM622) cells. Owing to an enol isomerization of malonate, the cycling stability of Li/PME/NCM622 is deteriorated, which is recovered with the introduce of dimethyl‐group in malonate and the suppression of enol isomerization. The coordinating capability with Li+, molecular asymmetry and existing modes of elemental F, are all critical for the molecular design of SPEs.
Three families of ester‐based solid polymer electrolytes consisting of polycarbonate, polyoxalate and polymalonate were prepared and investigated on their Li+‐conductivity and antioxidation ability. The performances of solid polymer electrolytes are affected by the coordinating capability with Li+, molecular asymmetry and existing modes of elemental F.
Trace N, N‐dimethylformamide(DMF) containing composite polymer electrolytes (CPEs) has attracted much attention owing to the dramatically increased Li+‐conductivity. But the amount of DMF is critical ...and needs to be clarified for the interfacial stability, since DMF is easily reduced by Li‐metal. Herein, the influences of DMF in poly(ethylene oxide) (PEO) and poly(vinylidene fluoride) (PVDF) based CPEs are studied on the Li+‐conductivity and interfacial stability. In PEO‐based CPEs, owing to a stronger interaction of lithium bis(trifluoromethanesulfon)imide (LiTFSI) with PEO than DMF, DMF can not be confined and be easily evaporated off. Only ≈0.25wt.% DMF is absorbed on ceramic electrolyte fillers, giving two times increased Li+‐conductivity compared with the DMF‐free counterparts and generating stable interface with Li‐metal; but over much DMF (≥2.2 wt.%) leads to serious interfacial reactions with Li‐metal. While in PVDF‐based CPEs, ≈8wt.% DMF is confined by LiTFSI owing to a stronger interaction of LiTFSI with DMF than with PVDF. Short‐term stable interface with Li‐metal can be obtained, but longer‐term cycling or higher current density leads to the gradually aggravated reactions with Li‐metal. Thanks to the high‐voltage stability of PVDF based CPEs, better cycling performance is obtained when they are used as catholytes to match high‐voltage cathodes.
In PEO‐LiTFSI electrolyte, LiTFSI shows stronger interaction with PEO than DMF, making DMF free and can be removed easily; in PVDF‐LiTFSI electrolyte, LiTFSI owns stronger interaction with DMF than PVDF, immobilizing DMF well in Li(DMF)TFSI complex. Although DMF is helpful to improve the Li+‐conductivity, it brings challenge for the stability with Li‐metal, with the exception of trace amount of DMF (0.2–0.3 wt.%) absorbed on ceramic electrolyte particles.
Solid polymer electrolytes (SPEs) with LiTFSI (lithium bis(trifluoromethane sulfonimide)) are promising candidates for solid‐state batteries, owing to their good interfacial contact with solid ...electrodes. Here, three copolymerized polyethers were prepared as SPEs, using the catalysts of SnF2 or SnF2‐LiPF6. The thermal depolymerization of these polyethers was observed at elevated temperatures, which limits their operating temperature ranges. Once the catalyst is removed, the thermal degradation temperatures of these SPEs are raised by 30–55 °C, together with improved thermal performance in cells. For SPEs, the high price of LiTFSI is an obstacle for their large‐scale application, and it's recycling is hindered by the strong interaction with polymers. By the thermal depolymerization of polyethers, LiTFSI can be easier reclaimed from above mentioned SPEs and even the commercial PEO(poly(ethylene‐oxide)) based SPE in rates of 70–80 %, providing a low‐cost strategy for the recycling of LiTFSI.
A family of F‐containing thermally depolymerizable polyethers were prepared as solid electrolytes, and with the help of the thermal degradation of polyethers, the LiTFSI was successfully reclaimed in high yields of 80 %, providing an example for the recycling of LiTFSI and benefiting the cost control of solid‐state batteries.
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