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Abstract Highly sensitive conductive polymer composites for piezoresistive sensing are developed by a design of the formulation variables of extrusion-based manufacturing (filler type/amount, polymer amount) and annealing (a), considering thermoplastic polyurethane (TPU) and/or olefin block copolymer (OBC) as polymer matrix and carbon black (CB) as conductive filler. With ternary composites - based on a CB type with stronger filler-matrix interactions and an appropriate OBC/TPU blend mass ratio (40/60 with CB amount of 5–10 m%; 50/50 with CB amount of 10 m%), the challenging region of both high sensitivity and static strain (maximal gauge factors (GF max) > 50 and ε max > 100%) can be realized: GF max > 104 and ε max = 20–240%. OBC binary composites with a high CB 2 amount (e.g. 15 m%) are however needed for ultrahigh static strains (ε max > 600%). Well-designed ternary composites (e.g. OBC 40 -CB/TPU 60 -7-a and OBC 30 -CB/TPU 70 -7-a) possess a large dynamic resistance change, negligible hysteresis and high stability and display strain sensor application potential. Highly CB 2 loaded binary (≥12 m%) and ternary composites (10 m%) exhibit a more obvious strain-dependent dynamic hysteretic behavior, as they switch from a dual peak to single peak pattern toward the sensing strain limit, which is interesting for self-diagnose. [ABSTRACT FROM AUTHOR]

Abstract: Here, we report some unique crystalline morphologies of poly(lactic acid) (PLA) via organic solvent-induced crystallization. It was revealed that the surface morphology of PLA can be fine tuned by simply varying the volume ratio of a mixed solvent (acetone/ethanol). By increasing the ethanol content in the mixed solvent, we observed a morphological evolution of PLA surface from spherulite to shish–kebab and bamboo-cage-like structure. It was also interesting to find that the initial surface structure of PLA plays an important role to determine the final solvent-induced crystalline morphology. This work provides a new method for manipulating PLA crystal morphology through a simple solvent-induced crystallization. [Copyright &y& Elsevier]

Flexible and stretchable piezoresistive strain sensors which can translate mechanical stimuli (strain changes) into electrical signals (resistance changes) provide a simple and feasible detection tool in the field of health/damage monitoring, human motion detection, personal healthcare, human-machine interfaces, and electronic skin. Herein a detailed overview is presented on both strategies for sensing performance improvement and progress to medium or large-scale fabrication. A broad range of matrices/substrates and incorporated nanomaterials is covered and attention is paid to the current state-of-the-art of feasible but low-cost manufacturing methods. The sensor design parameters include sensitivity (gauge factor), stretchability, linearity, hysteresis, biocompatibility, and self-healing potential. Starting from fundamental sensing mechanisms, i.e. the tunneling effect, the disconnection mechanism, and the crack propagation mechanism, examples are provided from lab to application scale. [ABSTRACT FROM AUTHOR]

To understand how the thermal conductivity (TC) of virgin commercial polymers and their composites with low graphite filler amounts can be improved, the effect of material choice, annealing and moisture content is investigated, all with feasible industrial applicability in mind focusing on injection molding. Comparison of commercial HDPE, PP, PLA, ABS, PS, and PA6 based composites under conditions minimizing the effect of the skin-core layer (measurement at half the sample thickness) allows to deduce that at 20 m% of filler, both the (overall) in- and through-plane TC can be significantly improved. The most promising results are for HDPE and PA6 (through/in-plane TC near 0.7/4.3 W·m−1K−1 for HDPE and 0.47/4.3 W·m−1K−1 for PA6 or an increase of 50/825% and 45/1200% respectively, compared to the virgin polymer). Testing with annealed and nucleated PA6 and PLA samples shows that further increasing the crystallinity has a limited effect. A variation of the average molar mass and moisture content is also almost without impact. Intriguingly, the variation of the measuring depth allows to control the relative importance of the TC of the core and skin layer. An increased measurement depth, hence, a higher core-to-skin ratio measurement specifically indicates a clear increase in the through-plane TC (e.g., factor 2). Therefore, for basic shapes, the removal of the skin layer is recommendable to increase the TC. [ABSTRACT FROM AUTHOR]

Na 3 Zr 2 Si 2 PO 12 (NZSP) solid-state electrolyte is considered one of the most promising solid-state electrolyte because of their excellent electrochemical and thermal stability. Even though, the low conductivity of NZSP solid-state electrolytes hinders practical application. Therefore, an anions/cations co-assisting strategy is proposed by introducing the Zn2+ and F−. The influence of adding different amounts of Zn2+ and F− on the Na+ conductivity of NZSP was investigated computationally and experimentally. The Zn2+/F− co-assisting (Na 3.3 Zr 1.85 Zn 0.15 Si 2 PO 12) solid-state electrolyte exhibits the ionic conductivity of 0.722 mS cm−1 at 30 °C, and the activation energy of ∼0.237 eV. Its applicability in a solid-state battery is tested, and the assembled Na/Na 3 V 2 (PO 4) 3 (NVP) battery exhibits an outstanding electrochemical performance of 98.4% capacity retention after being cycled at 0.5 C. Moreover, DFT calculations also have been used to demonstrate the effect of doping on the crystal structure and space migration energy barrier. This research provides new ideas for improving the electrochemical properties of inorganic solid electrolytes. • A new method for anionic/cations to co-assisting improve the ionic conductivity of solid electrolytes. • The Zn2+ replaces Zr4+ to increase the conductivity of the bulk phase. • The F− can improve the sintering activity of ceramic materials to make the grains larger and denser. • The NZSP-0.15ZF solid electrolyte battery shows an ultrahigh capacity retention of 98.4% after 200 cycles. [ABSTRACT FROM AUTHOR]

Nickel‐rich (Ni≥90 %) layered cathodes are critical materials for achieving higher‐energy‐density and lower‐cost next‐generation Li‐ion batteries (LIBs). However, their bulk and interface structural instabilities significantly impair their electrochemical performance, thus hindering their widespread adoption in commercial LIBs. Exploiting Ti and Mo diffusion chemistry, we report one‐step calcination to synthesize bulk‐to‐surface modified LiNi0.9Co0.09Mo0.01O2 (NCMo90) featuring a 5 nm Li2TiO3 coating on the surface, a Mo‐rich Li+/Ni2+ superlattice at the sub‐surface, and Ti‐doping in the bulk. Such a multi‐functional structure effectively maintains its structural integrity upon cycling. As a result, such NCMo90 exhibits a high initial capacity of 221 mAh g−1 at 0.1 C, excellent rate performance (184 mAh g−1 at 5 C), and high capacity retention of 94.0 % after 500 cycles. This work opens a new avenue to developing industry‐applicable Ni‐rich cathodes for next‐generation LIBs. [ABSTRACT FROM AUTHOR]

Nickel‐rich (Ni≥90 %) layered cathodes are critical materials for achieving higher‐energy‐density and lower‐cost next‐generation Li‐ion batteries (LIBs). However, their bulk and interface structural instabilities significantly impair their electrochemical performance, thus hindering their widespread adoption in commercial LIBs. Exploiting Ti and Mo diffusion chemistry, we report one‐step calcination to synthesize bulk‐to‐surface modified LiNi0.9Co0.09Mo0.01O2 (NCMo90) featuring a 5 nm Li2TiO3 coating on the surface, a Mo‐rich Li+/Ni2+ superlattice at the sub‐surface, and Ti‐doping in the bulk. Such a multi‐functional structure effectively maintains its structural integrity upon cycling. As a result, such NCMo90 exhibits a high initial capacity of 221 mAh g−1 at 0.1 C, excellent rate performance (184 mAh g−1 at 5 C), and high capacity retention of 94.0 % after 500 cycles. This work opens a new avenue to developing industry‐applicable Ni‐rich cathodes for next‐generation LIBs. [ABSTRACT FROM AUTHOR]

Dual CEI/SEI protection layers formed by an inducing strategy are successfully realized for optimizing the stability of electrolyte/electrode interfaces and further improving the rate performance and cycling stability of SSLMBs. [Display omitted] Designing a robust cathode electrolyte interphase (CEI) on a high-voltage cathode and stable solid electrolyte interphase (SEI) on a Li anode is the key to success in developing solid-state Li metal batteries (SSLMBs). In this work, we design an inorganic compound-intensive CEI layer and a LiF-rich gradient SEI layer in SSLMBs through the in-situ polymerization of a novel multi-functional electrolyte. The inorganic compound-intensive CEI offers excellent electrochemical compatibility with high-voltage layered cathode LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM), while the LiF-rich gradient SEI successfully suppresses Li dendrite formation and harmful interfacial parasite reactions. As a result, SSLMBs present a remarkable rate performance of 182 mAh g−1 at 1 C and a long cycling stability of 88.6% capacity retention after 300 cycles at room temperature. The fundamental insights into interface chemistry and facile strategy demonstrated in this work could assist the rapid development of SSLMBs toward remarkable performance. [ABSTRACT FROM AUTHOR]

As a novel thermoplastic elastomer, olefin block copolymers (OBCs) show a tremendous application potential in many areas. However, the practical use of OBCs is mainly restricted to the low load-bearing environments because of its poor low-strain mechanical strength and stiffness. In this work, short Kevlar fiber was introduced into OBC matrix to improve its mechanical properties. The results show that introduction of pristine Kevlar fiber only gives rise to a slight increase in tensile strength of OBC owing to the poor interfacial strength, regardless of the presence of compatibilizer maleic anhydride-grafted polypropylene (MA-g-PP). However, a largely enhanced tensile strength can be easily obtained when hydrolyzed or polydopamine-coated Kevlar fiber was incorporated into the OBC matrix using the MA-g-PP as the reactive compatibilizer. More importantly, the tensile strength can be further enhanced with the orientation of Kevlar fiber in the composites. As compared with compression molded composites with randomly orientated fibers, injection molded composites with highly oriented fibers exhibit a significantly higher tensile strength at the same composition. Moreover, it is interesting to observe that Kevlar fiber can be easily exfoliated into several microfibers during melt-mixing with OBC, but the exfoliation has no evident effect on the reinforcement effect possibly because of the poor interfacial strength between the newly-formed microfibers and the OBC matrix. Our work demonstrates that mechanical performance of short fiber reinforced elastomer composites could be significantly improved by enhancing interfacial strength and fiber orientation using a facile surface modification strategy and conventional melt-processing technology. [ABSTRACT FROM AUTHOR]

Combining both advances of electronic spin state modulation and tandem reaction mechanism, an atomic-level dual iron-copper catalyst is designed for enhanced oxygen reduction capability. Herein, the intense interaction between the iron-copper site and its coordination environment can not only controls the flow of external charge at the atomic level, but regulates the internal 3d electron configuration. These modulations can optimize the orbital interaction and pair hardness (η DA) between the acceptor and the donor, and achieves a fast tandem reaction kinetics, thereby surmounting the limitation of Scaling Relation. The as-prepared bimetal catalyst validates a high ORR activity and stability, which even exceed those of the benchmark Pt/C in pH-universal electrolytes. Meanwhile, Fe,Cu/N-C driven Zn-air batteries in alkaline and neutral electrolytes show prominent performance with peak power densities of 173.7 mW cm−2 and 86.5 mW cm−2. This work provides a useful design principle for developing or optimizing other efficient ORR catalysts. [Display omitted] • Fe,Cu/N-C to optimize orbital interaction and pair hardness during oxygen reduction. • The remarkable electrochemical performance for pH-universal oxygen reduction reaction. • Insights into regulating electronic configuration and constructing tandem reaction. [ABSTRACT FROM AUTHOR]

The synergistic effect of novel piezoelectric catalysis and traditional photocatalysis can significantly enhance catalytic performance. Herein, we design novel heterojunction piezo-photocatalysts combining Co-N-C and BiFeO 3 (BFO), the yields of CO 2 reduction to CO and CH 4 with Co-N-C@BFO(1:7) catalyst are up to 1373.41 µmol/g and 169.32 µmol/g, respectively. The displacement current, energy band theory, piezoelectric effect, and in-situ DRIFTS are combined to explain the mechanism. In piezo-photocatalysis, displacement current generates time-varying electrostatic potential, which transfers electrons to the Co-N-C active site and promotes CO 2 RR. The energy band of the BFO supplier meeting the potential requirements also promotes electron transfer to the Co-N-C active site to participate in CO 2 RR. The combination of piezoelectric electric fields and visible lights promotes charge separation and improves catalytic activity. This work provides a profound understanding and a new idea for piezo-photocatalytic reduction of CO 2. [Display omitted] • The Co-N-C@BFO piezoelectric catalyst with high active site was successfully designed and prepared. • Displacement current, energy band tilt and piezoelectric effect promote the charge separation efficiency greatly. • The synergistic effect of mechanical vibration and visible light driving enables the catalyst to have good reduction performance for CO 2 RR. • The reduction pathways and intermediate species are investigated by in-situ DRIFTS. [ABSTRACT FROM AUTHOR]

• The adjacent Fe-Ni sites synergy and charges donated from carbon substrate can trigger the 3d electron configurations transition of Fe-Ni sites. • Based on molecular orbital theory, Fe sites with high spin prefer to promise bifunctional catalytic activity. • The analyses based on molecular orbital theory and DFT calculations are consistent with the experimental conclusions. • The (Fe, Ni)@N-MWCNTs deliver excellent performance and cycling stability in ZABs. The optimization of 3d electron configurations is considered a feasible approach to improve the catalytic activity of transition metal nitrogen carbon (TM–N–C) electrocatalysts. Herein, by stacking Fe-Ni dual-metal on carbon substrate to obtain (Fe, Ni)@N-MWCNTs as model objects, we reveal that Fe3+ with high spin in Fe-Ni sites which possesses 3d electron configurations suitable for both OER and ORR. Specifically, the metal sites can be effectively activated by both 3d electron configurations optimization and the charges donated from the carbon substrate, which can balance the competition between OER and ORR process, rendering the excellent bifunctional performances with a small potential difference (ΔE = 0.828 V). In addition, it further provides an excellent performance and cycling stability in aqueous zinc-air batteries. The assembled wearable flexible zinc-air batteries also provide stable cycling performance and can be worn as a wristband to light up LED lights. [ABSTRACT FROM AUTHOR]

Inclusive quantum dots hollow CN@CIZS heterojunction has been successfully prepared and for accelerating photocatalytic CO 2 reduction. It exhibits excellent photocatalytic performance. [Display omitted] • The heterojunction between hollow g-C 3 N 4 and CuInZnS QDs is successful designed, and exhibits outstanding CO 2 RR performance. • The hollow architecture affords a larger specific surface area and enhances light absorption for photocatalysis. • CuInZnS QDs can increase the adsorption and activation capacity of CO 2 on hollow g-C 3 N 4. • Optimization of the photocatalytic performance was strongly demonstrated by in-situ DRIFTS and other photochemical tests. Photocatalytic conversion of carbon dioxide (CO 2) to fuel or useful chemicals is of great significance for energy and environmental issues. Herein, we successfully prepare a hollow g-C 3 N 4 @Cu-In-Zn-S quantum dots (CN@CIZS QDs) photocatalytic heterojunction employing the method of electrostatic self-assembly. The hollow structure, multiple exciton effect of quantum dots and the discrepancy of band structure generate excellent photocatalytic performance. The yield of CO 2 photocatalytic reduction to CO and CH 4 respectively is 23.04 μmol g−1 and 13.92 μmol g−1 after simulated visible light irradiation for 6 h for hollow CN@CIZS QDs 20 wt% sample. Moreover, the results of in-situ characterization and other photochemical tests strongly demonstrate the significant optimization of the photocatalytic performance. The research offers a feasible green thought for the resource utilization of CO 2. [ABSTRACT FROM AUTHOR]

The selective reduction of carbon dioxide (CO 2) as the primary component of greenhouse gas, remains a significant challenge in photocatalysis. Here, we present a novel strategy of preparing highly selective and stable heterostructure photocatalysts, which simultaneously contain oxygen and nitrogen vacancies. Synergistic catalysis effect originated from Nb 2 O 5 with oxygen vacancies and nitrogen-rich vacancies of metal-free catalytic (g-C 3 N 4) substrate leads to excellent photocatalytic reduction performances. The as-prepared photocatalysts exhibit outstanding capacity of selective reduction of CO 2 with yields of CH 4 16.07 μmol g−1 and CO 0.89 μmol g−1 after 5 cycles. Furthermore, the CO 2 reduction mechanism is confirmed through density functional theory (DFT) calculation and in-situ technology in detailing. This indicates that the heterojunction surface has a lower free energy barrier for CO 2 reduction compared with the pristine sample surface. This new strategy may exploit a vital application of dual-vacancy heterostructure in environmental catalysis. The designed dual-vacancy Nb 2 O 5 @g-C 3 N 4 heterojunction forms a highly stable V 1 -C-O-V 2 configuration. The configuration boosts photocatalytic CO 2 reduction with highly selective conversion to CH 4. [Display omitted] • Rich oxygen and nitrogen vacant g-C 3 N 4 -Nb 2 O 5 heterojunction is successful designed. • Dual-vacancy structure increases the adsorption and activation capacity of CO 2 on V O,N -NBCN. • The V O,N -NBCN exhibits enhanced photocatalytic CO 2 RR with highly selective conversion to CH 4. • The active reduction pathways and intermediate species are investigated by DFT calculation and in-situ DRIFTS. [ABSTRACT FROM AUTHOR]

Abstract: Conductive network morphology and interfacial interaction play important roles in determining resistivity–strain (ρ–ε) sensing behavior of conductive polymer composites (CPCs). In this work, thermoplastic elastomer blends consisting of poly(styrene–butadiene–styrene) block polymer (SBS) and thermoplastic polyurethane (TPU) were fabricated via different melt processing procedures, which could tune the above two issues simultaneously by selectively localizing multi-walled carbon nanotubes (MWCNTs) in SBS, TPU and both in SBS and TPU, respectively. It is observed that the composite fibers with selectively localized MWCNTs show distinct different ρ–ε sensing behavior. Work of adhesion calculation suggests stronger interfacial interaction between MWCNTs and SBS, however, wetting coefficient calculation indicates slightly better wetting of MWCNTs with TPU. Because of such stronger interaction and poorer dispersion, the composite fiber with MWCNTs distributed in SBS exhibits higher ρ–ε sensitivity than its counterpart with MWCNTs distributed in TPU, and with MWCNTs distributed in both phases, the ρ–ε sensitivity lies in between. Moreover, the ρ–ε sensing behavior was fitted with a model based on tunneling theory by Simmons. It is suggested that the change in tunneling distance and the number of conductive pathways could be accelerated significantly under strong interfacial interaction. This study could offer a new pathway and provide a guideline for the preparation of high-performance CPC resistivity–strain sensors with tunable sensitivity. [Copyright &y& Elsevier]