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Topic Review
Vehicle-to-Home
Vehicle-to-home (V2H) describes a bidirectional electric energy transfer interface concept that enables the onboard traction battery energy storage system of plug-in electric vehicles to supply electrical power for residential household loads through dedicated power conversion and interconnection hardware [1]. Under V2H operation modes, the electric vehicle functions as a mobile distributed energy resource that can provide backup power for domestic appliances and critical residential loads during grid outages, or support residential energy management and load shifting applications when the utility grid remains connected [2]. It defines the energy flow relationship between the electric vehicle battery system and residential premises; it is conceptually differentiated from vehicle-to-grid, whose primary objective is feeding power back to utility distribution networks at grid level rather than serving individual residential loads [3].
  • 8
  • 21 Sep 2026
Topic Review
Hard Carbon
Hard carbon is a non-graphitizable carbon material built from randomly oriented graphene-like nanodomains, curved or fullerene-like fragments, and internal closed pores, and it cannot be converted into graphite even after treatment above about 2500 °C [1]. It is obtained mainly by pyrolysis of biomass, sugars, resins, and polymers at 1000–1600 °C, and its structure is usually described by the interlayer spacing (0.36–0.40 nm, against 0.335 nm for graphite) together with the volume fraction of closed micropores [2]. For sodium-ion batteries the material serves as the negative electrode, where reversible capacities of roughly 250–350 mAh/g are commonly reported [3]. Two storage processes are distinguished in the galvanostatic curve: adsorption of sodium at defect sites and pore surfaces, which gives the sloping region, and insertion or pore filling, which is associated with the low-potential plateau near 0.1 V [4]. Because plateau capacity depends on closed-pore volume, the balance between the sloping and plateau regions is governed by precursor selection, pyrolysis temperature, and heteroatom doping rather than by any single synthesis parameter [5]. Initial Coulombic efficiency, typically 70–90%, and the contribution of sodium metal plating to the measured capacity remain debated [3][4].
  • 8
  • 22 Sep 2026
Topic Review
Organic Solar Cell
An organic solar cell is a photovoltaic device in which light is absorbed and charge is separated by molecular or polymeric semiconductors rather than by an inorganic crystal. Absorption creates a bound exciton, so a donor-acceptor interface is needed to split it; in the bulk heterojunction the two materials are cast from a common solution and interpenetrate on a scale of 10 to 20 nanometres, which sets how many excitons reach an interface before they decay [1]; in an oligothiophene-fullerene blend it is this interpenetrating structure that carries the photocurrent [2]. The morphology of the blend depends on the solvent, the drying rate and any thermal or solvent annealing, and small changes in domain purity and size can move the power conversion efficiency by several percentage points [1], the domain structure entering the optical and photovoltaic response directly [3]. Early devices used fullerene derivatives as the acceptor, and laboratory cells of that type reached efficiencies approaching 10 percent [2]. Non-fullerene acceptors, whose absorption and energy levels can be tuned independently of the donor, were introduced to raise both the current and the voltage [4]. Certified efficiencies in single junctions now exceed 19 percent where wide-bandgap donors are matched to them to keep the open-circuit voltage high [5]. Stability under illumination and in air, and the difficulty of reproducing the blend morphology outside spin coating, remain the main obstacles [3].
  • 8
  • 22 Sep 2026
Topic Review
Printed Circuit Board
A printed circuit board (PCB) is a rigid or flexible insulating substrate onto which conductive pathways, pads, and other features are patterned in order to mechanically support and electrically interconnect electronic components [1]. The conductive patterns are typically formed from copper laminated to the substrate and etched or plated to define traces, with plated-through holes or vias connecting conductive layers in multilayer constructions [2]. Components are mounted onto the board by soldering to pads that are themselves integrated into the patterned copper layer [1]. The substrate materials are commonly glass-reinforced epoxy laminates, polyimide, or other dielectric materials selected for mechanical rigidity, thermal stability, and electrical insulation [2]. A PCB is distinguished from a bare printed wiring board by the inclusion of patterned conductive features that form a defined circuit, and from a backplane by the integration of active and passive components as well as interconnects [3]. Design and manufacturing requirements for PCBs—including conductor width, spacing, dielectric thickness, and via geometry—are standardized in industry specifications [3].
  • 7
  • 17 Sep 2026
Topic Review
Voltage Source Converter
A voltage source converter (VSC) is a power-electronic converter that uses a DC voltage source as its energy-storage element and synthesizes an AC voltage waveform by switching the DC voltage onto the AC terminals through controlled semiconductor devices [1]. The DC side is characterized by a relatively stiff voltage, typically maintained by a capacitor, while the AC-side current is controlled by modulating the magnitude and phase of the synthesized AC voltage relative to the AC system voltage [2]. VSCs are implemented using self-commutated devices such as insulated-gate bipolar transistors, gate-turn-off thyristors, or integrated gate-commutated transistors, which permit independent control of active and reactive power exchange with the AC system [3]. The AC output is generally pulse-width-modulated, with passive filters used to attenuate switching harmonics [2]. A VSC is distinguished from a current source converter (CSC), which uses a stiff DC current source and a series inductor on the DC side, by the nature of its DC-side energy storage and by the quantity that is held constant on the DC side [1].
  • 6
  • 17 Sep 2026
Topic Review
Power Electronics
Power electronics is an engineering discipline focused on the conversion, conditioning and control of electric power by means of power semiconductor switching devices, passive energy-storage components and associated control circuitry [1]. It implements controlled mutual conversion between alternating-current and direct-current electric energy forms, as well as adjustment of voltage magnitude, current amplitude and operating frequency for power-level energy flow [2]. It targets high-energy-flow power processing applications, and is conceptually distinct from small-signal analogue electronics which are primarily designed for information signal processing and communication rather than bulk energy conversion. The field encompasses converter topologies, semiconductor device physics, control algorithms, electromagnetic design and thermal management aspects of power conversion systems [3].
  • 6
  • 21 Sep 2026
Topic Review
Single-Slope Analog-to-Digital Converter
A single-slope analog-to-digital converter (single-slope ADC) is an integrating-type ADC that converts an input analog voltage into a digital word by measuring the time required for a linear ramp waveform to cross the input voltage [1]. The conversion begins with the reset of an integrator capacitor; the integrator then generates a voltage that ramps linearly at a known constant rate while a counter is incremented by a fixed-frequency clock [2]. When the ramp voltage equals the input voltage, a comparator stops the counter, and the counter reading is proportional to the input voltage, yielding the digital output [1]. Because the conversion relies on a single ramp and a single comparison per conversion, the architecture is simple, and its differential linearity is largely determined by the linearity of the ramp generator and the stability of the clock [2]. The single-slope ADC is distinguished from the dual-slope (dual-ramp) ADC, which uses an additional de-integration interval to cancel errors due to ramp slope and component drift [2]. Its conversion time is signal-dependent and relatively long, which places it among low-speed, high-resolution ADC architectures [3].
  • 5
  • 18 Sep 2026
Topic Review
Zinc-Air Battery
A zinc-air battery is a metal-air electrochemical cell in which a zinc anode is paired with a porous air electrode that reduces atmospheric oxygen, giving a theoretical energy density on the order of 1086 Wh kg-1 and a nominal cell voltage near 1.65 V [1]. The cell is assembled in the discharged state and is normally operated with an alkaline aqueous electrolyte, so that discharge consumes zinc and oxygen and produces zincate species that precipitate as zinc oxide [2]. Two electrochemical steps limit performance: the oxygen reduction reaction on discharge and the oxygen evolution reaction on charge, both of which are slow and require bifunctional catalysts, so the same air electrode must catalyse both without being degraded by the high potentials reached during charging [2]. On the anode side, zinc dissolves and re-deposits unevenly during cycling, producing dendrites, shape change and passivation that shorten cycle life [3]. Electrically rechargeable systems, in which the air electrode operates in both directions, have been demonstrated, and alternative configurations separate the charge and discharge electrodes or replace the liquid electrolyte with a solid-state or gel membrane [4]. Measured round-trip efficiencies are typically 50–65% over tens to a few hundred cycles, and the values depend strongly on current density, depth of discharge and catalyst loading [4]. Energy densities reported for practical cells remain well below the theoretical figure because of the mass of the electrolyte, separator and current collectors [5].
  • 5
  • 22 Sep 2026
Topic Review
Solid Electrolytes
Solid electrolytes are ion-conducting solids that replace the liquid salt solution in an electrochemical cell and act at the same time as the separator between the electrodes. Garnet-type oxide ceramics doped with aluminium, niobium or germanium reach conductivities of 10-4 to 10-3 S per centimetre at room temperature once they are sintered to high density [1], and substitution on the zirconium site has been reported to raise the value further [2]. Sulfide glasses and glass-ceramics conduct lithium faster, in some compositions above 10-3 S per centimetre, and being softer they can be densified by cold pressing, but they release hydrogen sulfide on contact with moisture [3]. Polymer and ceramic-polymer composite electrolytes trade conductivity for compliance and ease of processing [4]. In a cell the total resistance is rarely set by the bulk alone: grain boundaries, space-charge layers and the electrode-electrolyte interface add to it, and the contact area changes as the electrode expands and contracts during cycling, so interlayers and external pressure are used to keep the interface intact [5]. Lithium penetration along grain boundaries and pores limits the usable current density, and how to suppress it without raising the interfacial resistance is still debated [3].
  • 4
  • 22 Sep 2026
Topic Review
Anion Exchange Membrane
An anion exchange membrane is a polymer film bearing fixed cationic groups that conducts hydroxide or other anions while blocking the transport of cations and of the reactant gases. In a water electrolyser the membrane separates the two electrodes, carries the ionic current and sets the ohmic loss, so its conductivity and its stability in hot alkali largely determine how the cell performs; cationic head groups attached to an aryl-ether-free backbone resist the nucleophilic attack that degrades earlier materials [1]. Cross-linking two cationic sites into one polymer chain raises the ion content without the swelling that usually comes with it, and hence improves both conductivity and dimensional stability [2]. Carbonate formed when the cell is fed with air rather than pure oxygen lowers the conductivity, and models of the electrolyte composition quantify how large that penalty is [3]. Because reported performance depends strongly on cell hardware and test protocol, a standard test cell has been proposed for comparing membranes and catalysts [4]. The alkaline environment also widens the catalyst choice to nickel-based hydrogen evolution catalysts [5].
  • 2
  • 23 Sep 2026
Topic Review
Cyclic Stability
Cyclic stability is the ability of an electrode, a device or a material to retain its performance over repeated charge-discharge or load-unload cycles, and it is reported as the fraction of the initial capacity or property remaining after a stated number of cycles at a stated rate. In batteries the loss is rarely due to one cause: the active material may transform or dissolve, the electrode may lose electrical contact as particles move apart, and the electrolyte may be consumed in side reactions that thicken the interphase. Conversion and alloying electrodes undergo the largest volume change, and embedding the active phase in a carbon matrix is the standard way to accommodate it, iron oxide in a carbon microsphere being an early example [1]. A conductive scaffold performs the same function in a silicon electrode, where a nanowire network keeps the particles connected through repeated expansion [2], and controlling the pore structure of the electrode gives the same gain more generally [3]. In lithium-sulfur cells the loss mechanism differs, because the intermediate polysulfides dissolve and migrate, so the sulfur is encapsulated in a shell [4]. Binding it into a conductive polymer network is the alternative [5]. Reported retention figures depend strongly on the rate and the depth of discharge, so they are comparable only under matched conditions.
  • 2
  • 24 Sep 2026
Topic Review
Dielectric Permittivity
Dielectric permittivity is the quantity that relates the electric displacement in a material to the applied field, written as a complex number whose real part describes stored energy and whose imaginary part the loss. Both parts depend on frequency and temperature, so a value quoted without them means little. At microwave frequencies the measurement is usually made by placing the specimen in a resonator or a transmission line and comparing the response with and without it; microwave dielectric ceramics are commonly characterised by two complementary methods, one based on the resonant frequency and quality factor, the other on reflection [1]. Thin sheets and liquids are more conveniently handled with an open-ended coaxial probe, whose fringing field senses only the near surface and which needs careful calibration to give absolute values [2]. High-permittivity materials are hard to measure in a closed cavity because the specimen perturbs it too strongly, and an extra-cavity arrangement avoids that [3]. Predicting the effective permittivity of a mixture from its constituents and their arrangement is a separate problem, addressed by mixing rules that take the inclusion shape into account [4]. Data-driven models fitted to measured spectra now serve the same purpose for heterogeneous materials, wood included [5].
  • 2
  • 24 Sep 2026
Topic Review
Stretchable Electronic
Stretchable electronics is a class of electronic devices fabricated on elastomeric or flexible substrates that can sustain large tensile strain, bending, twisting, and out-of-plane deformation without loss of electrical functionality, in contrast to conventional rigid silicon-wafer electronics that fracture under even modest mechanical strain [1]. The devices are commonly constructed using inorganic semiconductor nanomaterials—such as silicon nanoribbons, ultrathin membranes, or wavy and serpentine interconnect structures—bonded to pre-strained elastomeric substrates so that buckling and out-of-plane wrinkling accommodate the applied strain while the active material itself remains well within its elastic deformation limit [2]. Alternatively, organic field-effect transistors embedded in soft elastomeric matrices and metallic nanowire networks are used to build large-area, conformable pressure and thermal sensor arrays and electronic-skin systems that can be stretched, twisted, bent, and conformally wrapped over arbitrary three-dimensional curvilinear surfaces while maintaining stable electrical conductivity and consistent electronic device performance under repeated mechanical cycling and deformation [3].
  • 2
  • 25 Sep 2026
Topic Review
Sparse Signal Processing
Sparse signal processing is a framework for representing, acquiring, and reconstructing signals that have a sparse or compressible representation in some dictionary or transform basis, meaning that only a small fraction of the coefficients are significant while most are zero or near-zero. The central result of compressed sensing is that such signals can be reconstructed exactly from far fewer linear measurements than the Nyquist-Shannon sampling theorem requires, provided the measurement matrix satisfies the restricted isometry property and the signal is sufficiently sparse [1]. The reconstruction problem is formulated as an underdetermined linear system solved through L1-norm minimization, which promotes sparsity by penalizing the sum of absolute coefficients, or through greedy algorithms such as orthogonal matching pursuit that iteratively select the dictionary atoms most correlated with the residual. The framework applies to image processing, MRI, radar, and communication systems where the cost or bandwidth of acquiring full Nyquist-rate samples is prohibitive. The mathematical conditions for exact recovery are governed by incoherence between the measurement basis and the sparsity basis, and the number of measurements required scales logarithmically with signal dimension and linearly with sparsity level [2]. The theory unifies signal representation, sampling, and inverse problem solving under the principle that exploiting sparsity is equivalent to exploiting low-dimensional structure, and it provides deterministic recovery guarantees under random measurement ensembles [3].
  • 1
  • 24 Sep 2026
Topic Review
Microwave Dielectric Characteristics
Microwave dielectric characteristics are the set of frequency-dependent electromagnetic properties that a material exhibits when it interacts with electromagnetic fields in the microwave frequency range, typically from about one to several tens of gigahertz [1]. The three defining quantities are the relative permittivity, which governs the speed and wavelength of the signal within the material and determines device miniaturization; the dielectric loss, expressed through the quality factor Q or the product Q×f, which measures energy dissipated as heat; and the temperature coefficient of resonant frequency, which describes the thermal stability of the resonant frequency. These characteristics are determined fundamentally by the crystal structure, ionic polarizability, and lattice vibrational modes of the dielectric solid, because at microwave frequencies the polarization response is dominated by ionic displacement rather than by electronic or orientational polarization [2]. A useful material must therefore combine an appropriate permittivity, a low dielectric loss, and a near-zero temperature coefficient. The microwave dielectric characteristics constitute the physical basis for dielectric resonators, filters, and substrates in which the material's polarization and loss behavior control resonant frequency and bandwidth.
  • 1
  • 26 Sep 2026
Topic Review
Resistive Switching
Resistive switching is the reversible, non-volatile change in the electrical resistance of a thin insulating or semiconducting layer—sandwiched between two electrodes—in response to the amplitude, polarity, or duration of an applied voltage or current pulse [1]. In a typical metal–insulator–metal cell, the initially high-resistance state is converted into a low-resistance set state and subsequently restored to the high-resistance reset state, so that the device retains two distinguishable resistance levels without applied power. The underlying mechanism is redox-based: an applied field drives the drift of mobile oxygen vacancies or cations through the oxide, forming or rupturing a nanoscale conducting filament that short-circuits the insulator. The switching is therefore governed by ion migration rather than by the electronic charge storage used in conventional capacitors [2]. Because the resistance state depends on the internal distribution of mobile ionic species, the phenomenon is also described as nanoionic switching and forms the physical basis of memristive behavior, in which the conductance depends on the history of applied charge [3].
  • 1
  • 26 Sep 2026
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