High Anode Voltage Research Articles

Synergistic structure engineering and electrochemical activation modulating vanadium oxide cathode toward superior zinc-ion storage

Aqueous zinc-ion batteries (ZIBs) have emerged as competitive systems for grid-scale energy storage due to their high safety and low cost. However, the lack of suitable high-performance cathode composites limits the practical progress of ZIBs. Herein, a novel cathode material, ammonium cation-inserted and oxygen vacancy co-modulated VO2 (named NVE), was firstly synthesized through the ethylene glycol (EG) sacrificial solvent-assisted structure transformation with the ammonium vanadate (named NV) as the precursor. The sacrificial solvent promotes the structural transformation of ammonium vanadate to NH4+-intercalated vanadium oxide and enhances the number of oxygen vacancies in the resulting material. Moreover, the electrochemical activation process was performed for in-situ construction of NH4+-inserted hydrated vanadium oxide (V2O5·nH2O) material. The electrochemical activation process with high anodic voltage enables multiple electron reactions, increasing the utilization of vanadium elements and achieving high capacity. Additionally, the formed hydrogen bonds between the V-O host and inserted NH4+ ions can enhance the structural integrity, while the oxygen vacancies decrease the interaction between the V-O host and inserted Zn2+ ions to boost ion diffusion. Consequently, the resulting activated cathode demonstrates higher capacity (441 mAh/g at 0.1 A/g), superior cycling durability (85.6 % retention over 4000 cycles), and exceptional rate capability (205 mAh/g at 20 A/g). Besides, the fabricated devices based on the activated NVE cathode show decent capacity and excellent flexible stability. Furthermore, the reversible electrochemical Zn2+ storage mechanism upon battery cycling was evaluated by several kinetic measurements and in/ex-situ characterizations. This work provides novel perspectives for the fabrication of advanced cathode materials for superior aqueous ZIBs.

Optimization of Radiation Exposure when Examining Patients with Pathology of the Craniovertebral Region

The diagnostics are based on the principle of obtaining informative and high-quality images with minimal radiation exposure using radiation diagnostic methods: traditional radiography, multislice and cone-beam computed tomography.When conducting X-ray examinations, the main factors in reducing the risk of radiation exposure are the use of highly sensitive digital diagnostic image receivers, minimal exposure time, and a minimum number of images per examination. A lower current value and high anode voltage values, a minimum focal spot size, the placement of the tube as far as possible from the patient and the image receiver as close to the patient as possible, collimation of the radiation beam, and preference for a low radiation dose rate mode are also factors in reducing the risk of radiation exposure.Imaging of the craniovertebral region using cone beam computed tomography offers the opportunity to evaluate the bone structure of the region in detail, with an equal or less effective dose to the patient.

Feasibility of Multifunctional Cellulose-Based Polysalt as a Polymer Matrix for Li Metal Polymer Batteries.

Li metal secondary batteries known for their high energy and power density are the much-awaited energy storage systems owing to the high specific capacity of Li metal. However, due to the instability of Li metal with common Li-ion battery electrolytes, a combination with a polymer electrolyte seems to be an effective strategy to alleviate the safety issues of employing Li metal and provide design conformity to the system. Current trends show improvements in different aspects, such as improving ionic conductivity, single-ion conductivity, mechanical stability, and electrochemical stability. A combination of all these properties has been a bottleneck for the development of polymer electrolytes for safe and efficient operation of all solid-state batteries. Herein, a multifunctional polysalt has been synthesized from green and sustainable materials, namely, ethyl cellulose, plasticized with adiponitrile, that contributes to meeting the critical properties enabling high compatibility with Li metal and a quasi-single-ion-conducting property while simultaneously acting as a matrix/filler for efficient operation of the cells. This multifunctional polymer matrix inhibits further decomposition of nitrile-based plasticizers on Li metal anodes with the formation of a favorable Li metal anode interface, thus enabling the utilization of high-voltage stable nitrile-based plasticizers (4.2 V) to be implemented as an electrolyte component for realization of high-voltage Li metal anode polymer batteries.

Hindering breakdown in a long discharge tube by visible spectrum light illumination

The effect of irradiation with visible spectrum light on breakdown in discharge tubes 75–80 cm long and 1.5 cm in inner diameter in rare gases at a pressure of ∼1 Torr was studied. A ramp voltage of variable slope in the range of ∼10–1–105 kV s−1 was applied to the tube anode. The tube was illuminated by radiation from fluorescent lamps operating in a continuous mode, as well as by LEDs or a laser diode operating in a pulsed mode. The breakdown voltage and the pre-breakdown ionization wave (IW) velocity were measured. Illumination led to a change in the breakdown potential. The sign of this change depended on the anode voltage rise rate dU/dt. At dU/dt > 102–103 kV s−1, the breakdown voltage decreased. A similar effect was observed earlier and was explained by the appearance of electrons in the discharge gap under the light action, as a result of which the breakdown delay time decreased. This, in turn, caused a decrease in the breakdown voltage. At dU/dt < 101–102 kV s−1, on the contrary, the breakdown potential increased; at dU/dt ∼ 0.1 kV s−1, this increase could reach 5–6 times. The dependence of the observed effect on the radiation intensity, its wavelength, and the illuminated area position on the tube surface is studied. The pre-breakdown IW behaved in an unusual way under these conditions: its velocity and the signal amplitude recorded by the capacitive probe increased when moving from the high-voltage anode to the cathode. It is assumed that the observed features are caused by the desorption of weakly bound electrons from the tube wall surface under the action of irradiation. These electrons create a current that charges the wall near the anode. Since the first stage of discharge ignition is the initial breakdown between the anode and the tube wall, the anode potential for such a breakdown should increase, which means an increase in the breakdown voltage. Additional experiments with the initiation of a preliminary IW by a pulse applied to the cathode, confirmed the existence of a charge on the wall near the anode.

Asymmetric organic-inorganic bi-functional composite solid-state electrolyte for long stable cycling of high-voltage lithium battery

Poly(ethylene oxide) (PEO)-based solid-state electrolyte is difficult to achieve high voltage and energy density due to low ionic conductivity and narrow electrochemical stabilization window. Therefore, an urgent demand exists to construct a composite solid-state electrolyte that is resistant to both Li dendrite and high-voltage cathode oxidation. Here, we design and prepare an asymmetric bi-functional composite solid-state electrolyte achieving compatibility with Li anode and high-voltage anode to extend the cycle life of batteries. The F-containing hierarchically structured polyamide acids nanofibers towards the cathode side enhance interfacial compatibility with the cathode and provide excellent oxidation resistance. The rigid two-dimensional alumina nanosheets on the anode side further improve the interfacial stability with the Li anode and effectively inhibit the growth of Li dendrites. The synergistic effect of asymmetric organic-inorganic composite solid-state electrolyte is exploited to improve the cycling stability of different cathode (LiFePO4 (LFP) and LiNi0.8Mn0.1Co0.1O2 (NMC811))/Li batteries, greatly broaden the electrochemical stability window (5.3 V) and significantly enhance lithium dendrite inhibition. Based on density functional theory, the introduction of F-containing groups reduces the highest occupied molecular orbitals of the polyamide acids and that there is a strong binding between alumina and both the PEO terminal group and TFSI−. The result suggests that the composite solid-state electrolyte enhances the stability of PEO with the high-voltage cathode and Li anode, and inhibits the movement of anions. Therefore, it is noteworthy that the excellent electrochemical stability of this composite solid-state electrolyte with the NMC811/Li electrodes ensures long cycle of more than 800 cycles.

Liquid‐State Cathode Enabling a High‐Voltage and Air‐Stable Fe‐Al Hybrid Battery

AbstractAluminum (Al) is an ideal anode material in low‐cost battery system for energy storage, with high theoretical capacities. However, the sluggish Al3+‐involved kinetics challenges the selection of common cathode materials (Al3+ intercalation or conversion). Herein, a redox‐active Fe–Cl complex serves as the liquid‐state cathode to couple with a low‐cost Al anode, which synergizes the advantages of redox flow batteries and Al rechargeable batteries. The interplay of Fe‐Cl coordinated formula and electrochemical properties are revealed for the first time. It is found that [Fe2Cl7]− molecule has a high voltage versus Al anode (1.3 V), and the novel Fe‐Al hybrid battery fulfills a capacity of 1.6 mAh cm−2 (20 Ah L−1) record high in a coin cell among Al‐based batteries. Furthermore, the energy efficiency, which is a vital parameter to evaluate the energy cost of the energy storage technology, reaches 85% (superior to most Al‐based batteries) and an average of 70% over ≈900 h cycling. Particularly, the unique air‐stable character enables normal operation of the battery assembled in ambient air. This work establishes a new application scenario for Al anode toward low‐cost large‐scale energy storage.

DIGITAL APPROACH TO THERMIONIC EMISSION CURRENT TO VOLTAGE CONVERSION FOR HIGH-VOLTAGE SOURCES OF ELECTRONS

The thermionic emission current is used in many vacuum devices such as evaporators, rare gas excimers, or electron beam objects for high-energy physics. The stability of the thermionic emission current is a very important requirement for the accuracy of those devices. Hence, there is a number of control systems that use a feedback signal directly proportional to the emission current in order to stabilize the thermionic emission current. Most of them use feedback from a high-voltage anode circuit to a low-voltage cathode circuit. However, there is a novel solution that uses linear cathode current distribution and processing of two cathode circuit voltage signals for converting the emission current to voltage. However, it is based on old-fashioned analog technology. This paper shows the thermionic emission current to voltage conversion method with the use of a digital control system. A digital realization of a multiplicative-additive algorithm is presented and proper work in closed-loop mode is confirmed.

High performance graphene oxide/NiAl2O4 directly grown on carbon cloth hybrid for oxygen evolution reaction

Due to the lethargic kinetics, the oxygen evolution reaction (OER) requires a high anodic voltage, restricting the efficiency as well as practical applications for electrochemical water splitting. For this purpose, metal oxides (M − O) are viewed as a potential competitor in this search because of their high redox potential. Still, their low conductivity and instability are two significant barriers that must be addressed. In this study the nanocomposite of NiAl2O4 with graphene oxide (GO) as a highly effective and long-lasting electrocatalyst for OER has been fabricated. In an alkaline (1.0 M KOH) medium, the GO/NiAl2O4 responds to a very sharp overpotential of 219 mV at a current density of 10 mA/cm2 and with a lower value of tafel slope (43 mV/dec) as compared to its counterparts. The GO/NiAl2O4 corresponds to the high stability of 18 h with retained crystal structure and morphology. For the expected prolonged OER process, we assume the active redox couple due to the presence of Ni+2/+3 metal in NiAl2O4 varies periodically. Furthermore, the synergistic effect of NiAl2O4, combined with the GO, facilitates the dynamics of O2 evolution as a final product, and are useful for further applications in future era.

Improving the electrostatic design of the Jefferson Lab 300 kV DC photogun.

The 300kV DC high voltage photogun at Jefferson Lab was redesigned to deliver electron beams with a much higher bunch charge and improved beam properties. The original design provided only a modest longitudinal electric field (Ez) at the photocathode, which limited the achievable extracted bunch charge. To reach the bunch charge goal of approximately few nC with 75ps full-width at half-maximum Gaussian laser pulse width, the existing DC high voltage photogun electrodes and anode-cathode gap were modified to increase Ez at the photocathode. In addition, the anode aperture was spatially shifted with respect to the beamline longitudinal axis to minimize the beam deflection introduced by the non-symmetric nature of the inverted insulator photogun design. We present the electrostatic design of the original photogun and the modified photogun and beam dynamics simulations that predict vastly improved performance. We also quantify the impact of the photocathode recess on beam quality, where recess describes the actual location of the photocathode inside the photogun cathode electrode relative to the intended location. A photocathode unintentionally recessed/misplaced by sub-millimeter distance can significantly impact the downstream beam size.

Dilute dual-salt electrolyte for successful passivation of in-situ deposited Li anode and permit effective cycling of high voltage anode free batteries

An investigation of the cycling stability of anode-free batteries (AFBs) using dilute dual-salt electrolytes is conducted in a mixture of ether and carbonate solvents. Using the AFB configuration, various compositions of the dual-salt electrolyte were optimized and it was found that 0.9M-LiTFSI+0.3M-LiDFOB in FEC/TTE (2:3, v/v) is the best. An in-depth investigation of the electrochemical performance of AFB was conducted in this optimized dual-salt composition in comparison to 1.2 M LiTFSI in the same solvent ratio. Accordingly, the performance of Cu||NMC cell in the dual-salt electrolyte surpassed that of the single-salt. The relative better performance of the AFB in the dual-salt electrolyte is attributed to the co-existence of dual-ion (TFSI−&DFOB−) in the electrolyte, which enhanced conductivity and introduces entirely new interphases via preferential decomposition mechanisms. The newly formed interface is stable, ionically conductive, and able to intercept parasitic side reactions between the electrolyte solvent and the deposited Li by blocking electron and solvent flow towards the deposit. As a result of the unique interfacial chemistry brought by this dual-salt system, this electrolyte supports a unique CE (98.6%) and capacity retention (63%) in 4.5V Cu||NMC cell and exhibited >27% improvement over the single salt electrolyte after 50 cycles.

Conversion Method of Thermionic Emission Current to Voltage for High-Voltage Sources of Electrons

The stability of the electron thermionic emission current is one of the most important requirements for electron sources used, inter alia, in evaporators, production of rare gas excimers, and electron beam objects for high energy physics. In emission current control systems, a negative feedback signal, directly proportional to the emission current is transferred from the high-voltage anode circuit to the low-voltage cathode circuit. This technique, especially for high-voltage sources of electrons, requires the use of galvanic isolation. Alternatively, a method of converting the emission current to voltage in the cathode power supply circuit was proposed. It uses a linear cathode current intensity distribution and multiplicative-additive processing of two voltage signals, directly proportional to the values of cathode current intensity. The simulation results show that a relatively high conversion accuracy can be obtained for low values of the electron work function of the cathode material. The results of experimental tests of the dynamic parameters of the electron source and the steady-state Ie-V characteristic of the converter are presented. The implementation of the proposed Ie-V conversion method facilitates the design of the emission current controller, especially for high-voltage sources of electrons, because a negative feedback loop between the anode and cathode circuits is not required, all controller sub-components are at a common electrostatic potential.

Hybrid poly-ether/carbonate ester electrolyte engineering enables high oxidative stability for quasi-solid-state lithium metal batteries

Building safe and high-energy-density lithium metal batteries (LMBs) is currently being pursued to sustain our modern lifestyles. However, new electrolyte engineering is rigorously required that is capable of simultaneously providing good protection on lithium metal anode and sustaining high oxidative stability at the cathode, besides sufficient bulk conductivity and low interfacial resistance. Here, we report a novel hybrid poly-ether/carbonate ester quasi-solid-state electrolyte with high oxidative stability formed by a simple and efficient in situ polymerization of strategy, in which ring-opening polymerization of ether-based 1,3-dioxolane (DOL) and ester-based ethylene carbonate (EC)-ethylmethyl carbonate (EMC) is initiated by rare-earth triflate catalyst Sc(OTf)3 at room temperature. Such electrolyte engineering not only achieves a sufficiently high ionic conductivity of 5 × 10−4 S cm−1 but enables a high anodic voltage limit of 5 V while maintaining feasible battery manufacture technology. The hybrid poly-DOL/EC/EMC quasi-solid-state electrolyte is capable of producing a stable solid electrolyte interphase (SEI) featuring Li plating/stripping over 500 h at 0.5 mA cm−2 and decreased charge transfer resistance. The derived Li||LiFePO4 quasi-solid-state LMB, benefited from the enhanced oxidative stability of electrolyte, exhibits a notable capacity of 169 mAh g−1 at 1C with no capacity decay after 300 cycles.

Analysis and optimal design of LCC resonant converter for anode power supply in ECRH

The high-voltage anode power supply for the electron cyclotron system is proposed based on the LCC resonance circuit. The working process of the LCC resonant converter in the capacitive region is studied, and an analytical model of the capacitive LCC circuit is proposed. The analysis points out the boundary between the capacitive area and the inductive area of the converter. Aiming at the voltage drop between on-load and no-load in the open-loop of the LCC circuit, the characteristics of the capacitive LCC resonant circuit are analyzed to optimize the resonance parameters. Experimental results show that the proposed analytical model has high accuracy, and the voltage drop in the open-loop is 11.7%, which verifies the correctness of the optimized design.

Improving physical and mechanical properties of foil for anodes of high-voltage electrolytic capacitors by introducing an intermediate annealing

The results of studies of influence of intermediate and final annealing on the level of physical and mechanical properties of foil for anodes of highvoltage capacitors made of high-purity aluminum (99.99%) are presented. A comparative analytical analysis of efficiency of introduction of the intermediate annealing stage in the thermo-deformation processing mode in comparison with its absence in the scheme was performed. The starting material for the research is a strip with a thickness of 0.45 mm, obtained from hot-rolled strip with a thickness of 8 mm by cold rolling (deformation degree is 0.9437). The chemical composition of the strip corresponds to the A99 aluminum grade according to GOST 11069&ndash;2019. Content of basic impurities in the initial strip by the actual chemical composition,%: 0,0018 Si; 0.0012 Fe; 0.0020 Cu. A set of studies of physical and mechanical properties, which allowed to determine the dependence of the maximum value of specific capacity of high-voltage anode foil on the average grain size and crystallographic orientation (in this case - the maximum value of cubic texture, with allowable values of foil ultimate strength). It is shown that with an increase in the intensity of the cubic texture from 90 to 95%, the specific capacitance increases from 29 to 32 &mu;F/dm2. This is achieved through the use of intermediate annealing at 380 оC and further final annealing at 550 оC. The hereditary character of the average grain size of samples with a thickness of 0.45 mm during intermediate annealing and the grain size of the foil with a thickness of 0.100 mm after the final annealing is shown.

PNb9O25 nanofiber as a high-voltage anode material for advanced lithium ions batteries

If the operating voltage of anode materials is below 1.0 V versus Li+/Li, the side reaction between electrolyte and anode materials will occur extensively. Thus, high-voltage anode materials have aroused interest recently. In this work, we report the preparation of PNb9O25 nanofiber via a facile electrospinning method. The PNb9O25 nanofiber shows the high rate performance and excellent cycling performance when it is used as anode in lithium ions batteries. For instance, the PNb9O25 nanofiber can deliver a capacity of 233, 212.1, 193.8, and 181.4 mA h g−1 at 0.2, 1, 3, and 6C, respectively. After 1000 cycles, it can reach at 134.3 mA h g−1 with capacity retention of 70.9%. Meanwhile, the ex situ X-ray photoelectron spectroscopy technique has been adopted to investigate the evolution in valence state of each element for PNb9O25 nanofiber. In addition, the PNb9O25 nanofiber is chosen as the anode material in lithium ion full cell in this work, demonstrating the potential for practical application.

Electric field emission characteristics of a triode-structured metallic edge emitter from geometric conditions

Spindt-tip type cold electron emission has potential in various applications; however, it has a limited current capacity that prevents the emitters from being used for higher current sources, and the fabrication of the emitters is not easy. In this study, we investigate the electric field emission characteristics of a triode-structured metallic edge emitter from geometric conditions. We perform a systematic simulation based on Fowler-Nordheim theory to analyze the feasibility of using the proposed emitter. The dependences of the emission current, electron transmittance, and region of the triode mode on specific geometrical parameters, including the anode-gate vertical distance, gate-cathode vertical distance, gate-cathode horizontal distance, anode voltage, and gate voltage, are analyzed. The results show that the electric field for a narrow gate-cathode vertical distance is superior to the electric field of the gate electrode for a narrow gate-cathode horizontal distance, while the electric field for a wide gate-cathode vertical gap is more dominant than the electric field of the anode electrode for a wide gate-cathode horizontal gap. Moreover, the electron transmittance gradually increases with a low gate voltage, wide anode-gate vertical distance, and high anode voltage, and the region of the triode mode also increases with a high gate voltage, wide anode-gate vertical distance, and low anode voltage. Consequently, our results appear to be effective for an optimization in an experiment and are expected to improve present electric field emission techniques.

Simulation of the Electrostatic Distribution in the Proximity Focusing Structure of an EBCMOS

The electrostatic distribution of an electron bombarded CMOS (EBCMOS) was simulated by Ansoft Maxwell 3D software. Specifically, we studied how the electrostatic distribution was affected by the structure of a back-side bombarded CMOS (BSB-CMOS) and the anode position in electron-bombarded sensors. The simulation results reveal that the electrostatic field may cause a fault in the signal readout of the BSB-CMOS when the anode is positioned under the BSB-CMOS. In contrast, we found that the structure of an EBCMOS will aid electron focusing when the anode is positioned above the BSB-CMOS and the doping concentration of the electron multiplier layer is high. However, the high doping concentration of the electron multiplier layer will reduce the electron collection efficiency due to its rapid electron-hole recombination. We then designed a structure in which the multiplier layer has an overlying ultra-thin highly-doped layer, with an electrostatic distribution that functions to focus electrons. At the same time, this configuration can effectively prevent most of the multiplier electrons from recombining because ultra-thin highly-doped layer is much thinner than incident depth for the high-energy electron. This simulation study will provide a theoretical foundation for the fabrication of high-performance EBCMOS devices. Graphic abstract: a) EBCMOS physical model in Ansoft Maxwell 3D; b) The distribution of electrostatic distribution for BSB-CMOS with an ultra-thin heavily-doped layer. Electrostatic distribution of EBCMOS with different configurations were simulated. The results reveal that the electrostatic field may cause an erroneous readout of the BSB-CMOS if the anode is positioned under the BSB-CMOS. If the high voltage anode is positioned above the CMOS sensor, this is improved, especially when an ultrathin highly-doped multiplier layer is added to improve electron collection efficiency. This study provides a theoretical foundation for the fabrication of high performance EBCMOS devices.

In-situ removal of thick barrier layer in nanoporous anodic alumina by constant current Re-anodization

A novel method for thick barrier layer removal of nanoporous anodic alumina (NAA) based on a constant current re-anodization (third anodization step) is reported. The barrier layer consists of an alumina layer that prevents electrical contact between the inner pore volume and the aluminium substrate. Several methods have been reported for the removal of such alumina layer. However, none of them is applicable to NAA produced under high anodization voltages, for example with phosphoric acid (H3PO4) electrolyte. Herein, NAA is obtained by two-step anodization of aluminium at a constant voltage of 195 V in a H3PO4 electrolyte. The novelty of this study consists of the combination of a reduction of the barrier layer thickness with a partial chemical etching in a H3PO4 solution followed by a constant current re-anodization step. This opens branchings in the barrier layer that permit a complete removal with a final chemical etching step in H3PO4 solution. The best condition for removing the barrier layer in the constant current re-anodization step is to fix a constant density current of 17.0 μA/cm2. We obtain self-ordered NAA substrates without barrier layer, allowing for the establishment of an electrical contact between the aluminium substrate and the interior of the nanopores. These nanoporous-back metal contact structures can be very important for applications in energy generation, energy storage and optoelectronic devices.

TiO2 Nanotubes with Nanograss Structure: The Effect of the Anodizing Voltage on the Formation Mechanism and Structure Properties

Titanium dioxide nanotubes (TiO2 NTs) with a nanograss structure were synthesized in a fluoride organic electrolyte based on ethylene glycol under a potentiostatic anodization regime. By varying the anodization voltage, significant morphological differences were obtained, and the upper NTs’ surface has a nanograss appearance caused by the thinning of top tube walls, the result of the vertical splitting mechanism of nanograss growth. The samples were characterized using techniques such as scanning electron microscopy, x-ray diffraction, UV–visible spectroscopy and Mott–Schottky (MS) analysis. The obtained results show that samples annealed at 500°C for 3 h crystallized into anatase form and displayed the apparition of rutile phase at higher anodization voltage, where the morphology was significantly improved with thicker tube walls. The MS measurement of all samples displays a n-type semiconductor nature and the flat band potential (Ufb) takes less negative values by the increasing anodization voltage. As a result, TiO2 NTs with a nanograss structure expedite electron–hole separation, therefore, providing a lower recombination rate.

High Anodic-Voltage Focusing of Charge Carriers in Silicon Enables the Etching of Regularly-Arranged Submicrometer Pores at High Density and High Aspect-Ratio.

The anodic dissolution of silicon in acidic electrolytes is a well-known technology enabling the silicon machining to be accurately controlled down to the micrometer scale in low-doped n-type silicon electrodes. Attempts to scale down this technology to the submicrometer scale has shown to be challenging, though it premises to enable the fabrication of meso and nano structures/systems that would greatly impact the fields of biosensors and nanomedicine. In this work, we report on the electrochemical etching at high anodic voltages (up to 40 V) of two-dimensional regular arrays of millions pores per square centimeter (up to 30 × 106 cm−2) with sub-micrometric diameter (down to ~860 nm), high depth (up to ~40 μm), and high aspect-ratio (up to ~45) using low-doped n-type silicon electrodes (resistivity 3–8 Ω cm). The use of high anodic voltages, which are over one order of magnitude higher than that commonly used in electrochemical etching of silicon, tremendously improves hole focusing at the pore tips during the etching and enables, in turn, the control of electrochemical etching of submicrometer-sized pores when spatial period reduces below 2 μm. A theoretical model allows experimental results to be interpreted in terms of an electric-field-enhanced focusing of holes at the tip apex of the pores at high anodic voltages, with respect to the pore base, which leads to a smaller curvature radius of the tip apex and enables, in turn, the etching of pore tips to be preferentially sustained over time and space.