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A novel kind of C-coated and Sb-doped SnO2 (ATO/C) nanocomposite is prepared by a facile hydrothermal method following with high-temperature pyrolysis. The ATO/C particles are uniform, irregular, crystalline and small sizes (∼5–8 nm). High specific BET surface area of 192.1 m2 g−1 and low charge transfer resistance of 98.9 Ω are obtained for the ATO/C. When used as the anode of lithium ion battery, the ATO/C shows an ultrahigh lithium storage capacity. It may deliver an initial discharge specific capacity of 2634.9 mAh g−1 with the Coulombic efficiency of 88.4% at 0.1 C, and the capacity increases to the highest 2847.4 mAh g−1 after 50 cycles. Even after 1000 cycles at the increased current density of 1 C, the discharge capacity of 1008.5 mAh g−1 can be preserved indicating its high cyclic stability. Besides, it has a capacity of 370.8 mAh g−1 at the higher current density of 10 C, exhibiting the robust rate property.

Vibration signals are closely linked with health conditions of rotating machines and widely used in fault diagnosis. Unfortunately, traditional vibration signal-based fault diagnosis methods are under a universal assumption that the target vibration signals for application and the available vibration signals for model training are collected from the same distribution, which is always impractical in real-world scenarios due to working condition variation. For robust fault diagnosis under variable working conditions, although some transfer learning-based methods are proposed, they mostly aim at aligning only the marginal distribution discrepancy of datasets, which is validated not sufficient in some cases. Hence, we propose a new transfer learning method called improved joint distribution adaptation (IJDA) to align both the marginal and conditional distributions of datasets more comprehensively. Meanwhile, built on it, a working condition-robust fault diagnosis method is developed, which utilizes vibration signals and is mainly composed of three parts. Firstly, a new data augmentation method is developed to generate more useful samples for imbalanced vibration signals, which innovatively uses noise to boost network performance. Secondly, sparse filtering (SF) is employed to reduce the input dimension of IJDA. Finally, IJDA is utilized to firstly extract both sharing and principal features and then diagnose the features. Experiments on vibration signal datasets of roller bearings and a gearbox and comparisons with other methods verify its effectiveness and applicability.

Protein purification is of vital importance in the food industry, drug discovery, and other related fields. Among many separation methods, polyelectrolyte (PE)-based phase separation was developed and recognized as a low-cost purification technique. In this work, spherical polyelectrolyte brushes (SPBs) with a high specific surface area were utilized to study the protein accessibility and selective protein binding on highly charged nanoparticles (NPs) as well as the selective phase separation of proteins. The correlation between charge anisotropy, protein binding, and phase separation was investigated on various protein systems including those proteins with similar isoelectric points (pI) such as bovine serum albumin (BSA) and β-lactoglobulin (BLG), proteins with similar molecular weights such as BSA and hemoglobin (HB), and even protein variants (BLG-A and -B) with a tiny difference of amino acids. The nonspecific electrostatic interaction studied by turbidimetric titrations and isothermal calorimetry titration (ITC) indicates a specific binding between proteins and SPBs arising from the charge anisotropy of proteins. An optimized output based on selective protein binding on SPBs could be correlated for efficient protein separation through tuning external conditions including pH and ionic strength. These findings, therefore, proved that phase separation based on selective protein adsorption by SPBs was an efficient alternative for protein separation compared with the traditional practice.

Biomass materials have attracted extensive attention in functional composites because of the unique microstructure, renewability and electrochemical performance. Herein, porous NiO/C composites were synthesized through a hydrothermal reaction and calcination using cellulose-rich natural cotton as carbon source. The BET specific surface area of NiO/C composites was calculated to be 314.4 m2 g−1 basing on the Brunauer–Emmett–Teller model. As the LIB anode, NiO/C composites presented a high specific capacity of 727 mA h g−1 over 150 cycles at 100 mA g−1. Increasing the current density to 2 A g−1, enabled the specific capacity of NiO/C the electrode to reach 476 mA h g−1. Obviously, the unique nanostructure and synergistic effect of NiO and carbonaceous matrix made NiO/C composites exhibit the excellent lithium storage performance. The NiO/C composites are interconnected with each other and form nanopores leading to the large specific surface area, enabling the enhancement of electrolyte diffusion and providing additional routes for ion diffusion. In addition, the hybridized carbon substrate can mitigate the volume expansion and external bending stress of NiO/C composites during the lithiation/delithiation process.

Unusual three-dimensional mesoporous carbon/reduced graphene oxide (MP-C/rGO) matrix possessing graphene nanolayer pore walls built up by three to five graphene monosheets and some carbon particles with the sizes of about 5 nm located between the graphene nanolayers was prepared by facile freeze-drying and then carbonization of the poly(vinyl alcohol) and graphene oxide mixture. The mesoporous carbonaceous MP-C/rGO sample has a high specific surface area of 661.6 m2 g-1, large specific pore volume of 1.54 m3 g-1, and focused pore size distribution of 2-10 nm. About 64 wt % sulfur could be held in the pores of the MP-C/rGO matrix. As the cathode of a Li-S battery, the MP-C/rGO/S composite showed excellent electrochemical property including a high initial specific capacity of 919 mA h g-1 at 1 C with the capacity retention ratio of 63.3% and the Coulombic efficiency above 90% after 500 cycles. Meanwhile, the initial specific capacity of 602 mA h g-1 at 5 C and remaining capacity of 391 mA h g-1 after 500 cycles with an outstanding Coulombic efficiency of 97% indicate its exceptionally stable rate performance.

A novel ternary rGO/PPy/S nanocomposite possessing of a hierarchical nanostructure via incorporating the matrix of reduced graphene oxide (rGO) coated by polypyrrole (PPy) with sulphur was prepared by a facile one-pot in situ method. The chemical bonds exist between PPy and rGO through the formation of graphitic N and pyridine oxide N, and the C S, S C = S and S O chemical bonds form between rGO/PPy and S in the structure of the rGO/PPy/S material. The loading content of sulphur is 69.43 wt.% for the rGO/PPy/S sample. The rGO/PPy/S material exhibits a high performance when used as the cathode of Li-S battery. The initial and last discharge capacity arrived at 991.5 and 626.7 mAh g −1 at 1C with 400 cycles which is corresponding to the capacity retention ratio of 63.2%, indicating its very high cyclic stability. The discharge capacity of 537.4 mAh g −1 could be obtained at 5C and it maintained at 442.1 mAh g −1 after 400 cycles with the Coulombic efficiency of more than 90%, showing its excellent rate stability.

In this study, we synthesized an excellent ternary graphene-based carbon coated SnO2 (rGO/PC/SnO2) nanocomposite anode for lithium ion batteries (LIBs), in which carbon-coated SnO2 nanoparticles homogeneously grow on the surface of reduced graphene oxide (rGO) using glucose as the soft templating agent. Using glucose can limit the growth of the SnO2 particles; as a result, the size of the SnO2 particles would be relatively uniform. Moreover, the carbon coated on the surface of SnO2 particles can effectively prevent their agglomeration on the surface of rGO and limit their volume expansion during charge–discharge cycles. The porous structure of the rGO/PC/SnO2 nanocomposite can effectively accommodate the severe volume variation upon cycling and provide additional contact areas between the active material and the electrolyte. Significantly, the rGO/PC/SnO2 anode delivers an initial specific discharge capacity of 2238.2 mA h g−1 and retains 1467.8 mA h g−1 after 150 cycles at a current density of 0.1C (1C = 782 mA g−1). Even at the high specific current of 1C after 200 cycles, the reversible specific capacity is still as high as 618.3 mA h g−1. The rGO/PC/SnO2 anode exhibits excellent rate performances and possesses a reversible specific capacity of 445.9 mA h g−1 at 5C implying its good structural stability.

Co3O4 is considered a promising anode candidate for lithium ion batteries (LIBs) owing to its high theoretical capacitance. However, the electrochemical properties of bare Co3O4 for LIBs remain seriously limited by poor electronic conductivity and large volume expansion. Herein, carbon-coated porous Co3O4 polyhedrons with (220) facets are fabricated through a hydrothermal method and subsequent calcination process. The size of Co3O4 polyhedrons ranges from 70 nm to 170 nm. The continuous amorphous carbon layer is approximately 3 nm thick, and uniformly covers the surface of Co3O4. Moreover, the discharge capacity of carbon-coated porous Co3O4 anode reaches 1463 and 596 mA h g−1 at 100 and 5000 mA g−1, respectively. After 150 charge discharge cycles, the carbon-coated Co3O4 anode still exhibits a reversible capacity of 840 mA h g−1 at 1000 mA g−1. Carbon nano-coating, mixed conductive matrix, and crystalline texture design can enhance the electrochemical performance of Co3O4.

Biomass-derived porous carbon BPC-700, incorporating micropores and small mesopores, was prepared through pyrolysis of banana peel followed by activation with KOH. A high specific BET surface area (2741 m2 g-1 ), large specific pore volume (1.23 cm3 g-1 ), and well-controlled pore size distribution (0.6-5.0 nm) were obtained and up to 65 wt % sulfur content could be loaded into the pores of the BPC-700 sample. When the resultant C/S composite, BPC-700-S65, was used as the cathode of a Li-S battery, a large initial discharge capacity (ca. 1200 mAh g-1 ) was obtained, indicating a good sulfur utilization rate. An excellent discharge capacity (590 mAh g-1 ) was also achieved for BPC-700-S65 at the high current rate of 4 C (12.72 mA cm-2 ), showing its extremely high rate capability. A reversible capacity of about 570 mAh g-1 was achieved for BPC-700-S65 after 500 cycles at 1 C (3.18 mA cm-2 ), indicating an outstanding cycling stability.

A simple strategy for the reduction of graphene oxide by annealing was used to produce 3D hierarchically interconnected porous graphene (HIPG) samples. The optimized HIPG-900 sample possessing a specific surface area of 367.4 m2 g−1 and pore volume of 1.3 cm3 g−1 contains a large amount of sulfur (65.8 wt %) and improves the utilization of sulfur when used as the cathode of Li–S batteries. A high initial specific discharge capacity of 914.1 mAh g−1 and a specific capacity of 486.0 mAh g−1 after 500 cycles was obtained for HIPG-900/S composites at 1C. A high specific capacity of 467.2 and 162.4 mAh g−1 was obtained at a high rate of 10C with a Coulombic efficiency of over 90.0 % at the 1st and 500th cycle, respectively.

Li–S batteries with a high theoretical specific capacity and energy density are poised to be one of the most promising next generation systems; however, the complex preparation process of the cathode material and low cyclic stability, particularly at high current density, have limited their practical applications. Herein, we report a facile and eco-friendly one-pot strategy for the chemical reduction of graphene oxide and recombination of sulphur as the cathode material for a Li–S battery. The optimized rGO/S-3 composite material possesses a porous morphology with pore walls made of the rGO and sulphur composite. The sulphur content is about 73.5 wt%, the particle size is about 8–15 nm, and the particles are distributed evenly on the layer of rGO, wherein the thickness of rGO is about 3–4 nm, corresponding to 8–10 monolayer graphenes. The rGO/S-3 composite electrode presents a high initial discharge capacity of 1012 and 474 mA h g−1 at 1C and 10C, respectively. The discharge capacity of 451 mA h g−1 was preserved after 1200 cycles at 1C. Even though the current density increased to 10C, a discharge capacity of 237 mA h g−1 may be obtained after 400 cycles.

The development of supercapacitors with integrated high energy–power properties coupled with long cyclic life is an urgent demand in the energy storage field. The key to the assembly of such devices is to design and fabricate novel high-performance electrode materials in conjunction with matched electrolytes. In this study, a renewable graphene-like nitrogen-doped carbon nanosheet (RGNC-NS) has been constructed by using simultaneous carbonization and auto-activation followed by ultrasonic-assisted liquid exfoliation from natural layered shrimp shells. The final RGNC-NS had an optimum integration of graphene-like nanostructures (∼5 nm thick), large specific surface area (1946 m2 g−1), and rich nitrogen doping (8.75 wt%), resulting in high conductivity (7.8 S cm−1) and good surface wettability with an electrolyte. The RGNC-NS as a supercapacitor electrode exhibited an excellent rate capability with an ultrahigh capacitance of 322 F g−1 at 0.5 A g−1 and 241 F g−1 at 100 A g−1 (75% retention), as well as a long cyclic stability of 98.3% capacitance retention after 20 000 cycles at 10 A g−1 in 6 M KOH. Moreover, the RGNC-NS in a mixed ionic liquid electrolyte displayed an integrated high energy–power density of 30 W h kg−1 energy density at 64 000 W kg−1 power density and 93.2% capacitance retention after 8000 cycles at 5 A g−1.

MnO2 has been considered as a very promising positive electrode candidate for high energy density asymmetric supercapacitors (ASCs) because of high theoretical capacitance. However, the electrochemical performance of pure MnO2 for ASCs has still been severely limited by poor electronic conductivity, volume expansion and dissolution problem. Herein, we report flower-like MnO2-carbon composite (MnO2/SHAC) as positive electrode and layered Sisal Hemp Active Carbon (SHAC) as negative electrode for high-energy ASCs. The flower-like MnO2/SHAC positive electrode comprised a number of interconnected thin nano-flakes with a length of about 50–100 nm and a thickness of about 10 nm and exhibited a large specific surface area of 189.6 m2 g−1 and good conductivity. The SHAC negative electrode showed multi-layered graphene-like structure and a high BET surface area of 1303.5 m2 g−1. Moreover, the assembled MnO2/SHAC//SHAC ASC exhibits a maximum energy density of 46.2 Wh kg−1 at 0.1 A g−1 and a maximum power density of 3679.5 W kg−1 at 6 A g−1, suggesting that MnO2/SHAC composite has promising potential for practical supercapacitors with enhanced energy.

Recently, although vast intelligent fault diagnosis methods are proposed, their validities are mostly confirmed via balanced datasets, which cannot always hold for the class-imbalance problem prevails among datasets in real-world applications. Hence, a class imbalance-robust network is proposed for bearing fault diagnosis, which tackles class imbalance both in the feature extraction and classification stages. For feature extraction, balanced sparse filtering (BSF) is proposed, which innovatively introduces kurtosis into balancing the discriminative feature extraction capabilities of different classes. Meanwhile, the balancing matrix is also proposed in BSF to remedy the parameter updating imbalance caused by class imbalance. For feature classification, the balancing matrix is also embedded into softmax regression to enhance the balancing capability. Furthermore, extensive experiments on bearing vibration signal datasets are conducted in validity confirmation. Additionally, an interesting property of BSF is investigated, and the phenomenon that class imbalance is actually a two-edge sword is interpreted.

A N,O-codoped hierarchical porous nanocomposite consisting of binary reduced graphene oxide and pyrolytic carbon (rGO/PC) from chitosan is fabricated. The optimized rGO/PC possesses micropores with size distribution concentrated around 1.1 nm and plenty of meso/macropores. The Brunauer-Emmett-Teller specific surface area is 480.8 m

Hierarchical nanoporous N-doped carbon ZNC-1000 was prepared by facile pyrolysis of well-designed nanosized ZIF-8 precursor with optimized reaction temperature and time. It possesses large surface areas leading to sufficient exposed electrochemical active sites. Meanwhile, its moderate graphitization degree and suitable nanosized hierarchical porosity distributions would lead to the sufficient interaction between O2 and the electrocatalyst surface which would benefit the transports of electrons and the electrolyte ions for ORR. As an electrocatalyst for oxygen reduction reaction, the ZNC-1000 presents a better catalytic property than the commercial Pt/C with 6/1 mV positive shifts for onset/half-wave potentials and 1.567 mA cm−2 larger for limiting current density respectively. The stability of ZNC-1000 is also much better than that of Pt/C with negative shifts of 0/−2 mV (vs 5/31 mV) for onset/half-wave potentials and 6.0% vs 29.2% loss of limiting current density after 5000 cycles of accelerated durability test, as well as the relative current of 87.5% vs 40.2% retention after 30,000 s continuous chronoamperometric operation.

A novel kind of Pt/N-rGO hybrid possessing of low content 5.31 wt.% Pt anchored on the surface of nitrogen doped reduced graphene oxide (N-rGO) evenly was prepared. The Pt has uniformed 2.8 nm diameter and exposed (111) crystal planes; meanwhile, the N works as the bridge between Pt and rGO with the Pt-N and N-C chemical bonds in Pt/N-rGO. The Pt/N-rGO material has a very high electrocatalytic activity in oxygen reduction reaction with the mass catalytic activity more than 1.5 times of the commercial Pt/C due to the synergistic catalytic effect of both N-doped carbon matrix and Pt nanoparticles. Moreover, the Pt/N-rGO exhibits an excellent stability with hardly loss (only 0.4%) after accelerated durability tests of 5000 cycles based on the stable Pt-N-C chemical bonds in Pt/N-rGO, which can prevent the detachment, dissolution, migration and aggregation of Pt nanoparticles on the matrix during the long-term cycling.

A novel one-step hydrothermal and calcination strategy was developed to synthesize the unique 1D oriented Co3O4 crystal nanofibers with (220) facets on the carbon matrix derived from the natural, abundant and low cost wool fibers acting as both carbon precursor and template reagent. The resultant W2@Co3O4 nanocomposite exhibited very high specific capacity and favorable high-rate capability when used as anode material of lithium ion battery. The high reversible Li+ ion storage capacity of 986 mAh g−1 was obtained at 100 mA g−1 after 150 cycles, higher than the theoretical capacity of Co3O4 (890 mAh g−1). Even at the higher current density of 1 A g−1, the electrode could still deliver a remarkable discharge capacity of 720 mAh g−1 over 150 cycles.