Both experimental results and theoretical models suggest the decisive role of the filler–matrix interfaces on the dielectric, piezoelectric, pyroelectric, and electrocaloric properties of ...ferroelectric polymer nanocomposites. However, there remains a lack of direct structural evidence to support the so‐called interfacial effect in dielectric nanocomposites. Here, a chemical mapping of the interfacial coupling between the nanofiller and the polymer matrix in ferroelectric polymer nanocomposites by combining atomic force microscopy–infrared spectroscopy (AFM–IR) with first‐principles calculations and phase‐field simulations is provided. The addition of ceramic fillers into a ferroelectric polymer leads to augmentation of the local conformational disorder in the vicinity of the interface, resulting in the local stabilization of the all‐trans conformation (i.e., the polar β phase). The formation of highly polar and inhomogeneous interfacial regions, which is further enhanced with a decrease of the filler size, has been identified experimentally and verified by phase‐field simulations and density functional theory (DFT) calculations. This work offers unprecedented structural insights into the configurational disorder‐induced interfacial effect and will enable rational design and molecular engineering of the filler–matrix interfaces of electroactive polymer nanocomposites to boost their collective properties.
Using atomic force microscopy–infrared spectroscopy together with first‐principles calculations and phase field simulations, a spatial structure analysis of the filler–matrix interfaces in ferroelectric polymer nanocomposites is provided. The unprecedented insights into the interfacial coupling effect at the molecular level would enable interfacial engineering strategies to realize improved properties and unlock new functionalities of the nanocomposites.
Visualization of ion transport in electrolytes provides fundamental understandings of electrolyte dynamics and electrolyte-electrode interactions. However, this is challenging because existing ...techniques are hard to capture low ionic concentrations and fast electrolyte dynamics. Here we show that stimulated Raman scattering microscopy offers required resolutions to address a long-lasting question: how does the lithium-ion concentration correlate to uneven lithium deposition? In this study, anions are used to represent lithium ions since their concentrations should not deviate for more than 0.1 mM, even near nanoelectrodes. A three-stage lithium deposition process is uncovered, corresponding to no depletion, partial depletion, and full depletion of lithium ions. Further analysis reveals a feedback mechanism between the lithium dendrite growth and heterogeneity of local ionic concentration, which can be suppressed by artificial solid electrolyte interphase. This study shows that stimulated Raman scattering microscopy is a powerful tool for the materials and energy field.
Abstract
Polymer-ceramic piezoelectric composites, combining high piezoelectricity and mechanical flexibility, have attracted increasing interest in both academia and industry. However, their ...piezoelectric activity is largely limited by intrinsically low crystallinity and weak spontaneous polarization. Here, we propose a Ti
3
C
2
T
x
MXene anchoring method to manipulate the intermolecular interactions within the all-
trans
conformation of a polymer matrix. Employing phase-field simulation and molecular dynamics calculations, we show that OH surface terminations on the Ti
3
C
2
T
x
nanosheets offer hydrogen bonding with the fluoropolymer matrix, leading to dipole alignment and enhanced net spontaneous polarization of the polymer-ceramic composites. We then translated this interfacial bonding strategy into electrospinning to boost the piezoelectric response of samarium doped Pb (Mg
1/3
Nb
2/3
)O
3
-PbTiO
3
/polyvinylidene fluoride composite nanofibers by 160% via Ti
3
C
2
T
x
nanosheets inclusion. With excellent piezoelectric and mechanical attributes, the as-electrospun piezoelectric nanofibers can be easily integrated into the conventional shoe insoles to form a foot sensor network for all-around gait patterns monitoring, walking habits identification and Metatarsalgi prognosis. This work utilizes the interfacial coupling mechanism of intermolecular anchoring as a strategy to develop high-performance piezoelectric composites for wearable electronics.
Polymer dielectrics are highly desirable in capacitor applications due to their low cost, high breakdown strength, and unique self‐healing capability. However, existing polymer dielectrics suffer ...from either a low energy density or a high dielectric loss, thereby hindering the development of compact, efficient, and reliable power electronics. Here, a novel type of polymer dielectrics simultaneously exhibiting an extraordinarily high recoverable energy density of 35 J cm−3 and a low dielectric loss is reported. It is synthesized by grafting zwitterions onto the short side chains of a poly(4‐methyl‐1‐pentene) (PMP)‐based copolymer, which increases its dielectric constant from ≈2.2 to ≈5.2 and significantly enhances its breakdown strength from ≈700 MV m−1 to ≈1300 MV m−1 while maintaining its low dielectric loss of <0.002 and high charge–discharge efficiency of >90%. Based on a combination of the phase‐field method description of mesoscale structures, Maxwell equations, and theoretical analysis, it is demonstrated that the outstanding combination of high energy density and low dielectric loss of zwitterions‐grafted copolymers is attributed to the covalent‐bonding restricted ion polarization and the strong charge trapping by the zwitterions. This work represents a new strategy in polymer dielectrics for achieving simultaneous high energy density and low dielectric loss.
Zwitterion‐functionalized polymers are synthsized with a record‐high breakdown strength of 1300 MV m−1, energy density above 35 J cm−3, and charge–discharge efficiency of >90%, taking advantage of the covalent‐bonding‐restricted ion polarization and the charge trapping of the ion cluster phase.
Composed of electrocaloric (EC) ceramics and polymers, polymer composites with high EC performances are considered as promising candidates for next‐generation all‐solid‐state cooling devices. Their ...mass application is limited by the low EC strength, which requires very high operational voltage to induce appreciable temperature change. Here, an all‐scale hierarchical architecture is proposed and demonstrated to achieve high EC strength in poly(vinylidene fluoride‐trifluoroethylene‐chlorofluoroethylene)‐based nanocomposites. On the atomic scale, highly polarizable hierarchical interfaces are induced by incorporating BiFeO3 (BFO) nanoparticles in Ba(Zr0.21Ti0.79)O3 (BZT) nanofibers (BFO@BZT_nfs); on the microscopic scale, percolation of the interfaces further raises the polarization of the composite nanofibers; on the mesoscopic scale, orthotropic orientation of BFO@BZT_nfs leads to much enhanced breakdown strength of the nanocomposites. As a result, an ultrahigh EC strength of ≈0.22 K m MV−1 is obtained at an ultralow electric field of 75 MV m−1 in nanocomposites filled with the orthotropic composite nanofibers, which is by far the highest value achieved in polymer nanocomposites at a moderate electric field. Results of high‐angle annular dark‐field scanning transmission electron microscopy, in situ scanning Kelvin probe microscopy characterization, and phase‐field simulations all indicate that the much enhanced EC performances can be attributed to the all‐scale hierarchical structures of the nanocomposite.
An all‐scale hierarchical approach to achieving ultrahigh electrocaloric (EC) strength in flexible polymer composites is proposed and demonstrated. The enhanced EC performance is mainly attributed to the hierarchical interfaces inside the composite nanofibers. In addition, the orthotropic configuration of the BFO@BZT_nfs inside the terpolymer matrix further increases Eb of the nanocomposite and leads to substantially enhanced EC strength under a moderate electric field.
Particle-like topological structures such as skyrmions and vortices have garnered ever-increasing interests due to their rich physical insights and potential broad applications in spintronics. Here ...we discover the reversible switching between polar skyrmion bubbles and ordered vortex arrays in ferroelectric superlattices under an electric field, reminiscent of the Plateau-Raleigh instability in fluid mechanics. An electric field phase diagram is constructed, showing a wide stability window for the observed polar skyrmions. A “volcano”-like pontryagin density distribution is formed, indicating the formation of a smooth circular skyrmion. The topological charge Q at different applied field is calculated, verifying the field-driven topological transition between Q = 0 and Q = ±1 states. This study is a demonstration for the computational design of field-induced topological phase transitions, giving promise for the design of next-generation nanoelectronic devices.
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The formation and continuous growth of a solid electrolyte interphase (SEI) layer are responsible for the irreversible capacity loss of batteries in the initial and subsequent cycles, respectively. ...In this article, the electron tunneling barriers from Li metal through three insulating SEI components, namely Li2CO3, LiF and Li3PO4, are computed by density function theory (DFT) approaches. Based on electron tunneling theory, it is estimated that sufficient to block electron tunneling. It is also found that the band gap decreases under tension while the work function remains the same, and thus the tunneling barrier decreases under tension and increases under compression. A new parameter, η, characterizing the average distances between anions, is proposed to unify the variation of band gap with strain under different loading conditions into a single linear function of η. An analytical model based on the tunneling results is developed to connect the irreversible capacity loss, due to the Li ions consumed in forming these SEI component layers on the surface of negative electrodes. The agreement between the model predictions and experimental results suggests that only the initial irreversible capacity loss is due to the self-limiting electron tunneling property of the SEI.
•A new model to predict electron tunneling barriers and capacity loss was developed.•The predicted irreversible capacity loss agrees well with experiments.•2 nm of LiF or 3 nm of Li2CO3 are thick enough to block electron tunneling.•Electron tunneling barrier decreases under tension and increases under compression.
A self-triggered sampling scheme (STS) is proposed for a networked control system with consideration of data losses and communication delays. By making use of this scheme, the next sampling instant ...does not depend on online estimation of an event-triggered condition and the successive measurement of the state, and can be dynamically determined with respect to the transmitted packet, the desired control performance, and the allowable number of consecutive data losses and communication delays. Consequently, the sampling interval can be adaptively adjusted. Therefore, the communication burden can be greatly reduced and the energy efficiency can be much improved while preserving the desired H ∞ performance. An inverted pendulum and a one-area power system controlled over a wireless sensor network are given to illustrate the effectiveness of the proposed STS.
A nonlinear phase-field model, accounting for the Butler–Volmer electrochemical reaction kinetics, is developed to investigate the dendritic patterns during an electrodeposition process. Using ...lithium electrodeposition as an example, the proposed model is first verified by comparison with the Nernst equation in a 1D equilibrium system. The nonlinear electrochemical kinetics is also confirmed at non-equilibrium condition. The dendritic patterns are examined as a function of applied voltage and initial electrode surface morphology. A design map is proposed to tailor the electrode surface morphology and the applied voltage to avoid undesired dendritic patterns.
•A nonlinear phase-field model was developed for the dendritic growth.•The model accounts for the Butler–Volmer electrochemical reaction kinetics.•The model was verified by the Nernst equation.•Three different dendritic patterns were discovered.•A design map was proposed to avoid undesired dendritic patterns.
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