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Layered double hydroxides (LDHs) and metal sulfides (MSs) have been widely used as promising electrode materials for supercapacitors, and the rational architectural design of MS/LDH heterogeneous structures is critical to optimize large energy storage. Herein, a precisely designed hollow Co9S8 nanotubes@CoNi-LDH nanosheet heterostructure on Ni foam, facilely prepared by an ingenious in situ strategy in this Co9S8 nanoarray was first used as the self-sacrificing template and metal source to in situ synthesize Co-ZIF-67 polyhedron to form the Co9S8@ZIF-67 heterostructure, and then Co9S8@ZIF-67 was in situ etched successfully using Ni2+ ions to form the final Co9S8@CoNi-LDH/NF core–shell nanoarray. This in situ synthetic strategy to fabricate the heterostructure is conducive to boosting the structural stability, modifying the electric structure and regulating the interfacial charge transfer. Due to the synergistic effect and tight heterogeneous interface, Co9S8@CoNi-LDH/NF displayed an outstanding capacitance of 9.65 F cm−2 at a current density of 2 mA cm−2 and excellent capacitance retention rate of 91.7% after 5000 cycles. In addition, the ASC device assembled with AC has an extremely high energy density of 1.0 mW h cm−2 at 2 mA cm−2 and maintains 96.9% capacitance retention after 5000 cycles. This work provides a skillful strategy for the precise design and in situ synthesis of MS/LDH heterostructures with fascinating features for electrochemical energy storage applications. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) have been extensively applied in supercapacitors. Unfortunately, metal active sites in MOFs are commonly blocked and saturated by organic ligands, leading to insufficient positions available for the electrochemical reaction. To address this issue, we develop a novel strategy to design and prepare a series of hollow metal sulfide/MOF heterostructures, which simultaneously alleviate the large volume expansion, avoid slow kinetics of metal sulfides and expose more electrochemically active sites of the MOF. Consequently, the optimized Co9S8/Co-BDC MOF heterostructure presents outstanding electrochemical performance with a high areal specific capacitance of 15.84 F cm−2 at 2 mA cm−2 and a capacitance retention rate of 87.5% after 5000 charge–discharge cycles. The asymmetric supercapacitors based on the heterostructure deliver a high energy density of 0.87 mW h cm−2 and a power density of 19.84 mW cm−2, as well as long cycling stability. This study provides a new strategy for the rational design and in situ synthesis of metal sulfide/MOF heterostructures for electrochemical applications. [ABSTRACT FROM AUTHOR]

Orchard spraying robots must visually obtain citrus tree crown growth information to meet the variable growth-stage-based spraying requirements. However, the complex environments and growth characteristics of fruit trees affect the accuracy of crown segmentation. Therefore, we propose a feature-map-based squeeze-and-excitation UNet++ (MSEU) region-based convolutional neural network (R-CNN) citrus tree crown segmentation method that intakes red–green–blue-depth (RGB-D) images that are pixel aligned and visual distance-adjusted to eliminate noise. Our MSEU R-CNN achieves accurate crown segmentation using squeeze-and-excitation (SE) and UNet++. To fully fuse the feature map information, the SE block correlates image features and recalibrates their channel weights, and the UNet++ semantic segmentation branch replaces the original mask structure to maximize the interconnectivity between feature layers, achieving a near-real time detection speed of 5 fps. Its bounding box (bbox) and segmentation (seg) AP50 scores are 96.6 and 96.2%, respectively, and the bbox average recall and F1-score are 73.0 and 69.4%, which are 3.4, 2.4, 4.9, and 3.5% higher than the original model, respectively. Compared with bbox instant segmentation (BoxInst) and conditional convolutional frameworks (CondInst), the MSEU R-CNN provides better seg accuracy and speed than the previous-best Mask R-CNN. These results provide the means to accurately employ autonomous spraying robots. [ABSTRACT FROM AUTHOR]

Asymmetric supercapacitors (ASCs) are regarded as promising energy storage devices due to their excellent electrochemical properties, especially favorable power density. In this work, both the high-performance positive electrode and negative electrode materials are designed and prepared using the electrospinning technique and a metal–organic framework (MOF)-derived strategy. The obtained Bi-MOF-derived Bi2O3/C hollow nanofibers have an outstanding specific capacity (1420 F g–1 at 1 A g–1) and show an excellent cycling performance (92.21% retention after 4000 cycles) as negative electrodes, while the NiCo-MOF-derived NiCo2S4 hollow nanofibers as positive electrodes also have an excellent specific capacity (2656 F g–1 at 1 A g–1), and their capacity retention is 92.11% after 4000 charge–discharge cycles. The assembled ASC device with these two electrodes displays a high energy density of 85.38 W h kg–1 and excellent cycling performance with 80% retention after 10,000 cycles. Therefore, this work not only experimentally demonstrates MOF-derived Bi2O3/C and NiCo2S4 as fascinating candidate electrode materials for ASCs but also affords a method to rationally design and fabricate other electrode materials with unique hollow nanofiber structures for energy storage. [ABSTRACT FROM AUTHOR]

Reasonable design of electrodes with well-defined nanostructure is the central aspect in the practical application of high-performance supercapacitors. Herein, hollow tube@sheets NiCo2S4 core–shell nanoarrays are rationally constructed to the free-standing electrode by in situ growing ZIF-67 on Co-precursor nanorods array and sequentially performing anion-exchange (S2−) and cation-exchange (Ni2+). The well-defined nanostructures can shorten the ion transport path in the charging–discharging process, increase the specific surface area and electrochemical active cites, which help in improving electrochemical performance. Therefore, the unique tube@sheets NiCo2S4 core–shell nanoarrays exhibit intriguing electrochemical performance and show excellent areal capacitance of 11.3 F cm−2 (3227.94 F g−1) at a current density of 2 mA cm−2 (2 A g−1). The assembled asymmetric supercapacitor device delivers a high energy density of 0.42 mW h cm−2 at a power density of 2.1 mW cm−2 and displays outstanding cyclic stability (90.2% retention after 5000 cycles). Consequently, the well-defined nanostructure engineering strategy is beneficial for designing active electrode materials for efficient energy storage devices. [ABSTRACT FROM AUTHOR]