Exploring new type of synapse–like electronic devices with fusion of computing and memory is a promising strategy to fundamentally approach to intelligent machines. Herein, organic thin film ...memristors (OTFMs) are achieved, functioning as electrically programmable and erasable analog memory with continuous and nonvolatile device states. The memristive characteristics of OTFMs stem from the asymmetric electrode configuration and the cumulative charge trapping/detrapping in a polymer electret layer, which enables the state–dependent current modulation analogous to the synaptic weight change in biological synapses. OTFMs are demonstrated to successfully emulate the essential synaptic functions, including the reversible potentiation and depression, and the short‐term plasticity such as the paired‐pulse facilitation and the long‐term plasticity such as the spike–timing dependent plasticity.
Organic thin film memristors are achieved based on asymmetric electrode configuration and cumulative charge trapping/detrapping in a polymer electret layer, which function as electrically editable and preservable analog memory. Organic thin film memristors are demonstrated to be capable of emulating both short‐term and long‐term synaptic plasticity, such as the paired‐pulse facilitation and spike‐timing‐dependent plasticity.
Atomically ordered intermetallic nanoparticles are promising for catalytic applications but are difficult to produce because the high-temperature annealing required for atom ordering inevitably ...accelerates metal sintering that leads to larger crystallites. We prepared platinum intermetallics with an average particle size of <5 nanometers on porous sulfur-doped carbon supports, on which the strong interaction between platinum and sulfur suppresses metal sintering up to 1000°C. We synthesized intermetallic libraries of small nanoparticles consisting of 46 combinations of platinum with 16 other metal elements and used them to study the dependence of electrocatalytic oxygen-reduction reaction activity on alloy composition and platinum skin strain. The intermetallic libraries are highly mass efficient in proton-exchange-membrane fuel cells and could achieve high activities of 1.3 to 1.8 amperes per milligram of platinum at 0.9 volts.
Lithium sulfur batteries with high energy densities are promising next-generation energy storage systems. However, shuttling and sluggish conversion of polysulfides to solid lithium sulfides limit ...the full utilization of active materials. Physical/chemical confinement is useful for anchoring polysulfides, but not effective for utilizing the blocked intermediates. Here, we employ black phosphorus quantum dots as electrocatalysts to overcome these issues. Both the experimental and theoretical results reveal that black phosphorus quantum dots effectively adsorb and catalyze polysulfide conversion. The activity is attributed to the numerous catalytically active sites on the edges of the quantum dots. In the presence of a small amount of black phosphorus quantum dots, the porous carbon/sulfur cathodes exhibit rapid reaction kinetics and no shuttling of polysulfides, enabling a low capacity fading rate (0.027% per cycle over 1000 cycles) and high areal capacities. Our findings demonstrate application of a metal-free quantum dot catalyst for high energy rechargeable batteries.
Co-intercalation reactions make graphite as promising anodes for sodium ion batteries, however, the high redox potentials significantly lower the energy density. Herein, we investigate the factors ...that influence the co-intercalation potential of graphite and find that the tuning of the voltage as large as 0.38 V is achievable by adjusting the relative stability of ternary graphite intercalation compounds and the solvent activity in electrolytes. The feasibility of graphite anode in sodium ion batteries is confirmed in conjunction with Na
VPO
F
cathodes by using the optimal electrolyte. The sodium ion battery delivers an improved voltage of 3.1 V, a high power density of 3863 W kg
, negligible temperature dependency of energy/power densities and an extremely low capacity fading rate of 0.007% per cycle over 1000 cycles, which are among the best thus far reported for sodium ion full cells, making it a competitive choice in large-scale energy storage systems.
Calcium ion batteries (CIBs) are pursued as potentially low‐cost and safe alternatives to current Li‐ion batteries due to the high abundance of calcium element. However, the large and divalent nature ...of Ca2+ leads to strong interaction with intercalation hosts, sluggish ion diffusion kinetics and low power output. Herein, a small molecular organic anode is reported, tetracarboxylic diimide (PTCDI), involving carbonyl enolization (CO↔CO−) in aqueous electrolytes, which bypasses the diffusion difficulties in intercalation‐type electrodes and avoid capacity sacrifice for polymer organic electrodes, thus manifesting rapid and high Ca storage capacities. In an aqueous Ca‐ion cell, the PTCDI presents a reversible capacity of 112 mAh g−1, a high‐capacity retention of 80% after 1000 cycles and a high‐power capability at 5 A g−1, which rival the state‐of‐the‐art anode materials in CIBs. Experiments and simulations reveal that Ca ions are diffusing along the a axis tunnel to enolize carbonyl groups without being entrapped in the aromatic carbon layers. The feasibility of PTCDI anodes in practical CIBs is demonstrated by coupling with cost‐effective Prussian blue analogous cathodes and CaCl2 aqueous electrolyte. The appreciable Ca storage performance of small molecular crystals will spur the development of green organic CIBs.
PTCDI is first employed as the anode for aqueous calcium‐ion batteries. The guest‐host chemical bonding and structure evolution of molecular crystals are clearly clarified by simulation and in(ex)‐situ spectroscopy characterizations. This study extends the boundary of molecular crystal systems for electrochemistry to construct high‐performance aqueous multivalent ion batteries.
Summary
The article herein briefly introduces the story of the birth of click chemistry and its evolution after that. A new angle to interpret click reactions was proposed using the ...“reactivity‐availability‐functionality” trilogy. CuAAC (Copper‐catalyzed azide‐alkyne cycloaddition), the most popular click reaction by far, was revisited along with the thiol‐ene, metal‐free AAC, SuFEx (Sulfur(VI) fluoride exchange) and the lately discovered diazotransfer process. By encountering more and more near‐perfect reactions, click chemistry is evolving and expanding on the fringe of the chemistry and different scientific disciplines, destination unknown.
In the theoretical design and analysis of the sandwich piezoelectric ultrasonic transducer, the transducer is considered to be an ideal linear system, where the dielectric, piezoelectric and ...mechanical losses are neglected. However, when the transducer is driven at high power, the losses are becoming several times higher comparing them to low signal measurements, and the transducer works in a nonlinear state. In order to predict the performance of the transducer at high power, the nonlinear parameters (complex constants) of the piezoelectric materials are introduced. The corresponding nonlinear equivalent longitudinal wave sound velocity, the nonlinear equivalent longitudinal wave number of the piezoelectric ceramics are derived. Then the nonlinear equivalent circuit (NEC) and the nonlinear resonance frequency equation of the high-power sandwich piezoelectric ultrasonic transducer that related with the losses are deduced. Then, the nonlinear finite element model (NFEM) of the transducer is constructed. The performance parameters of the transducer obtained by the NEC method and the FE method are compared with each other, and consistent results have been achieved by two methods. Finally, the contribution of various losses is obtained through theoretical calculation, simulation and experimental measurement, and the correctness of the theoretical model in this paper is verified.
In this article, a continuous terminal sliding mode control algorithm is proposed for servo motor systems. A novel full-order terminal sliding mode surface is proposed based on the bilimit ...homogeneous property, such that the sliding motion is finite-time stable independent of the system's initial condition. A new continuous terminal sliding mode control algorithm is proposed to guarantee that the system states reach the sliding surface in finite-time. Not only the robustness is guaranteed by the proposed controller but also the continuity makes the control algorithm more suitable for the servo mechanical systems. Finally, a numerical example is presented to depict the advantages of the proposed control algorithm. An application in the rotary servo system is done to validate the effectiveness of the proposed control strategy.
Anatase TiO2 is considered as one of the promising anodes for sodium‐ion batteries because of its large sodium storage capacities with potentially low cost. However, the precise reaction mechanisms ...and the interplay between surface properties and electrochemical performance are still not elucidated. Using multimethod analyses, it is herein demonstrated that the TiO2 electrode undergoes amorphization during the first sodiation and the amorphous phase exhibits pseudocapacitive sodium storage behaviors in subsequent cycles. It is also shown that the pseudocapacitive sodium storage performance is sensitive to the nature of solid electrolyte interphase (SEI) layers. For the first time, it is found that ether‐based electrolytes enable the formation of thin (≈2.5 nm) and robust SEI layers, in contrast to the thick (≈10 nm) and growing SEI from conventional carbonate‐based electrolytes. First principle calculations suggest that the higher lowest unoccupied molecular orbital energies of ether solvents/ion complexes are responsible for the difference. TiO2 electrodes in ether‐based electrolyte present an impressive capacity of 192 mAh g−1 at 0.1 A g−1 after 500 cycles, much higher than that in carbonate‐based electrolyte. This work offers the clarified picture of electrochemical sodiation mechanisms of anatase TiO2 and guides on strategies about interfacial control for high performance anodes.
A thin and robust solid electrolyte interphase formed on a TiO2 surface that is enabled by using ether electrodes is demonstrated in Na‐ion batteries. This electrolyte/electrolyte interface, which is superior to conventional carbonate electrolyte, results in largely different electrochemical performances. The fundamental origin of the difference is unveiled through the combination of intensive experimental characterizations and first principles calculations.
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