High Current Capacity Research Articles

Favorable Interfacial Chemomechanics Enables Stable Cycling of High-Li-Content Li–In/Sn Anodes in Sulfide Electrolyte-Based Solid-State Batteries

Solid-state batteries (SSBs) can offer a paradigm shift in battery safety and energy density. Yet, the promise hinges on the ability to integrate high-performance electrodes with state-of-the-art solid electrolytes. For example, lithium (Li) metal, the most energy-dense anode candidate, suffers from severe interfacial chemomechanical issues that lead to cell failure. Li alloys of In/Sn are attractive alternatives, but their exploration has mostly been limited to the low capacity(low Li content)and In rich Li$_x$In (x$\leq$0.5). Here, the fundamental electro-chemo-mechanical behavior of Li-In and Li-Sn alloys of varied Li stoichiometries is unravelled in sulfide electrolyte based SSBs. The intermetallic electrodes developed through a controlled synthesis and fabrication technique display impressive (electro)chemical stability with Li$_6$PS$_5$Cl as the solid electrolyte and maintain nearly perfect interfacial contact during the electrochemical Li insertion/deinsertion under an optimal stack pressure. Their intriguing variation in the Li migration barrier with composition and its influence on the observed Li cycling overpotential is revealed through combined computational and electrochemical studies. Stable interfacial chemomechanics of the alloys allow long-term dendrite free Li cycling (>1000 h) at relatively high current densities (1 mA cm$^{-2}$) and capacities (1 mAh cm$^{-2}$), as demonstrated for Li$_{13}$In$_3$ and Li$_{17}$Sn$_4$, which are more desirable from a capacity and cost consideration compared to the low Li content analogues. The presented understanding can guide the development of high-capacity Li-In/Sn alloy anodes for SSBs.

Effects of Precipitation Hardening Variables on Al–Zn–Mg-Sn Alloy as Sacrificial Anode in Seawater: Experimental and Statistical Analysis

This research investigated the effects of tin composition and heat treatment variables on the Al-Zn-Mg alloy as sacrificial anode in seawater using gravimetric technique and statistical analysis. Tin was alloyed with Al-Zn-Mg in varied proportions (0%, 0.01%, 0.05% and 0.1%) to determine the optimum anode efficiency in the marine environment. Precipitation heat treatment was performed by first subjecting the samples to solution treatment at 5380C for 2 hours and later subjected to varying hardening temperatures and times. The samples were hardened for 4, 8 and 12 hours at each of the hardening temperatures of 1300, 1600 and 1900 centigrade. The anode efficiency increases as the tin concentration increases. The experimental result of this study showed that the Al-Zn-Mg alloy with 0.1% tin gives the optimum anode efficiency. It was revealed that the Al-Zn-Mg alloy without tin composition exhibited high output current capacity when hardened at 1900C for 4 hours. Predictive model developed in this work was in consonance with experimental observation except the following; at hardening temperature of 1600C, the model recommended 12 hours as against 4 hours of laboratory experiment and at hardening temperature of 1300C it advocated 8 hours as against 12 hours.Keywords - aluminum alloy, corrosion, precipitation hardening, regression and correlation analysis, and sacrificial anode

Saccharin Anion Acts as a "Traffic Assistant" of Zn2+ to Achieve a Long-Life and Dendritic-Free Zinc Plate Anode.

Due to the great advantages of low cost, high capacity, and excellent safety, the Zn metal is a promising candidate material for rechargeable aqueous battery systems. However, its practical applications have been restricted by the uncontrollable dendrite growth and electrode side reactions (such as corrosion, passivation, and hydrogen evolution reactions) during the plating process. Herein, we reveal that the dendrite growth would expose the electrode to more highly active tips, exacerbating the passivation of the electrode and the decomposition of the electrolyte by in situ optical microscopies. We propose a low-cost, nontoxic, low-concentration (less than 1 g/L), and effective electrolyte additive, saccharin sodium, which can guide an even Zn deposition without obvious electrode side reactions in the charge/discharge process. The saccharin anion acts as a "traffic assistant" of Zn2+ and demonstrates its great potential for practical application. The assembled Zn symmetrical battery shows an excellent cycling performance at a high current density and capacity (an extremely long cycle life over 3800 h is obtained at 5 mA/cm2 and 8 mA h/cm2, and 20 mA/cm2 and 5 mA h/cm2 show a lifetime over 800 h), and the full cell (coupled to an AC electrode) presents a stable cycle life with a capacity retention of 86.4% even after 8000 cycles at 5 mA/cm2. The saccharin sodium proposed in this work is promising to solve the anode problems in advanced Zn batteries.

Healable Lithium Alloy Anode with Ultrahigh Capacity.

Effective recycling of spent Li metal anodes is an urgent need for energy/resource conservation and environmental protection, making Li metal batteries more affordable and sustainable. For the first time, we explore a unique sustainable healable lithium alloy anode inspired by the intrinsic healing ability of liquid metal. This lithium alloy anode can transform back to the liquid state through Li-completed extraction, and then the structure degradation generated during operation could be healed. Therefore, an ultralong cycle life of more than 1300 times can be successfully realized under harsh conditions of 5 mA h cm-2 capacitance by a process of two healing behaviors. This design improves the sustainable utilization of Li metal to a great extent, bringing about unexpected effects in the field of lithium-based anodes even at an unprecedentedly high discharge current density (up to 25 mA cm-2) and capacity (up to 50 mA h cm-2).

Design of PAMBE-based selective-area growth compliant ultra-low leakage GaN mixed-conduction vertical diodes for high-power applications * *This work was supported by the Office of Naval Research (ONR) under the ONR Award N00014-17-1-2681 (Program Manager: Lynn J Petersen).

Modern high-speed power applications require diodes with high-current capacity, larger reverse blocking voltage, lower reverse recovery transients, and lower leakage. GaN mixed-conduction vertical diodes are an attractive option for these operations. Experimentally reported GaN diodes have two major shortcomings, namely, higher leakage due to non-optimum design and conventional processing methods (e.g. ion implantation and dry etching), introducing huge leakage components. In this work, we design ultra-low leakage GaN buried p-base merged p–i–n Schottky and buried p-base merged p–i–n junction barrier controlled Schottky diodes, capable of reducing leakage current by more than five orders of magnitude by virtue of strong reduced surface field effect. Moreover, these designs are fully compliant with our earlier reported silicon nitride shadowed selective-area growth (SNS-SAG) methodology, capable of reducing the leakage by at least four orders of magnitude. In combination with SNS-SAG and highly efficient dielectric vertical sidewall edge termination scheme, these designs provide attractive options for higher performance.

Realizing high-power and high-capacity zinc/sodium metal anodes through interfacial chemistry regulation

Stable plating/stripping of metal electrodes under high power and high capacity remains a great challenge. Tailoring the deposition behavior on the substrate could partly resolve dendrites’ formation, but it usually works only under low current densities and limited capacities. Here we turn to regulate the separator’s interfacial chemistry through tin coating with decent conductivity and excellent zincophilicity. The former homogenizes the electric field distribution for smooth zinc metal on the substrate, while the latter enables the concurrent zinc deposition on the separator with a face-to-face growth. Consequently, dendrite-free zinc morphologies and superior cycling stability are achieved at simultaneous high current densities and large cycling capacities (1000 h at 5 mA/cm2 for 5 mAh/cm2 and 500 h at 10 mA/cm2 for 10 mAh/cm2). Furthermore, the concept could be readily extended to sodium metal anodes, demonstrating the interfacial chemistry regulation of separator is a promising route to circumvent the metal anode challenges.

Electromagnetic Analysis of HTS DC Cables Based on Critical State Model

High-temperature superconducting (HTS) DC cables have the advantages of low transmission loss, high current density and large transmission capacity, which have gained more and more attentions in recent years. The typical structures of HTS DC cables include unipolar and bipolar coaxial that doubles the cable's transmission capacity. Based on the critical state model, this article analyses and contrasts the critical current density distributions and degradations due to magnetic field in the HTS tapes of the unipolar and coaxial bipolar DC cables. The influences of the bipolar cables with different voltage levels are also compared. The results show that the critical current density degradations due to magnetic field are almost the same in both unipolar and coaxial bipolar structures, which are mainly caused by the self-field. For the bipolar cables, the current density distribution in the outer layer HTS tapes changes with the voltage level. To evaluate the influence of the axial magnetic field, a 3-D model of the unipolar cable is established with a helical wound pitch of the HTS tapes. The results show that the axial magnetic field is relatively low and the critical current density would not degrade if the helical angle of the HTS tapes is reasonably small.

Evaluation of Electromechanical Properties in Multiple HTS Layered Conductors at 77 K

High engineering critical current density (J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">e</sub> ) is demanded in high-performance large-scale applications such as power cables, high-magnetic-field magnets, accelerators, and fusion reactors. In developing high current capacity and low vulnerability under a high magnetic field, high-temperature superconducting (HTS) rare-earth barium copper oxide coated conductors (CCs) have undergone various trials, and CC tape characteristics have ultimately been greatly improved. The Korea Electrotechnology Research Institute recently developed a “multiple HTS layers on one substrate” (MHOS) conductor that can carry high critical current, I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> , based on the number of superconducting layers deposited on one substrate. The superconducting layers in a MHOS conductor are much thicker than in a single-layered CC tape, possibly affecting the degradation behaviors of I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> under a mechanical load. To ensure the performance and reliability of MHOS conductors, it is necessary to evaluate the strain/stress response of I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> . In this study, the electromechanical properties of MHOS conductors were investigated using the uniaxial tension test method as well as the single-sided bending test at 77 K and self-field and at 0.5 T using a pair of neodymium permanent magnets.

Tests and recovery under load simulations of a novel bifilar resistive SFCL having undulated shape configuration

Power systems are becoming more interconnected and complex. The distributed generation expands and spreads across the grids, reducing the distance between the load and the generation. In addition, several substations are aging after decades of operation and their equipment struggle to sustain the ever increasing fault levels. In this context, the fault current limiter (FCL) arrived as a solution to mitigate this problem. Considering the FCL devices, the resistive superconducting FCL (R-SFCL) is the most mature technology with potential to be produced in mass scale, due to its ability to quickly change its impedance during a fault current and its high current density capacity. In this paper, a novel R-SFCL topology is presented, which has an unique design that allows a compact size and the possibility of modulated assembly. These characteristics enable setups for various voltage and current levels. One advantage of this topology is the compromise between volume and high heat exchange that can reduce the recovery time under load. One bench prototype was modeled using the thermal–electrical analogy implemented in ATPDraw, tested in two different labs. Tests were performed at faults levels of 12 kA, 5 kA and 2.7 kA for 137 V. Measured and simulated results were compared, resulting in a relative error of less than 12%. Two contributions can be highlighted: the new design of the R-SFCL and the inclusion in the convection heat exchange model curves for the heating (during the quench) and cooling (after fault), which allows to predict the recovery under load.

Layered nanocomposite separators enabling dendrite-free lithium metal anodes at ultrahigh current density and cycling capacity

Non-uniform and dendritic lithium (Li) deposition in Li metal batteries largely compromises battery performance including cycle life, capacity and safety. Various innovative approaches have been proposed to solve these issues, but stable cycling of Li metal anode at high current density and cycling capacity remains challenging. Here, we report design of layered nanocomposite separators with nacre-like microstructure by considering both the electrochemical deposition behavior and spatial distribution of Li+ ions. The separators are prepared by flow-induced alignment of Laponite@RD nanosheets along the Celgard separator surface and in situ crosslinking of the nanosheets with polyvinylalcohol. The separators enable dendrite-free lithium metal anodes at ultrahigh current density and cycling capacity simultaneously. Remarkably, stable Li metal anode with low overpotential and a long cycle life of over 2000 h is achieved by the separator even at a current density of 30 mA cm−2 and a cycling capacity of 15.0 mA h cm−2. The Li-sulfur (5.4 mg cm−2 S loading) and Li-NCM523 (8.8 mg cm−2 NCM523 loading) batteries show excellent rate performance and cycling stability. This study demonstrates the potential of polymer/clay layered nanocomposite separators for stable cycling of Li metal anodes at high current density and cycling capacity.

Etching Sr3Al2O6 sacrificial layer to prepare freestanding GBCO films with high critical current density

We report a method for synthesizing freestanding GdBa2Cu3O7-x thin films with high current carrying capacity. On the LaAlO3 substrate, an epitaxial water-soluble sacrificial layer of Sr3Al2O6 was grown by RF magnetron sputtering, and then a GdBa2Cu3O7-x film was deposited on the sacrificial layer. By etching the water-soluble sacrificial layer, we obtained a freestanding GdBa2Cu3O7-x film. The surface of the freestanding film is smooth and dense and its critical current density reaches 0.65 MA/cm2 at a temperature of 30 K and a zero magnetic field. The successful preparation of this freestanding GdBa2Cu3O7-x film with high critical current density makes the application of superconducting films more extensive and flexible.

Characterization of HTS Coils for Superconducting Rotating Electric Machine Applications: Challenges, Material Selection, Winding Process, and Testing

The second-generation high-temperature superconducting tapes (2G-HTS) such as the REBCO coated conductors are known for their strong mechanical properties and high current carrying capacity with low ac losses compared with first-generation HTS tapes as well as low-temperature superconductors. Therefore, they seem to be good candidates to assemble coils for superconducting rotating electric machines (SuREMs). In this article, to investigate the influence of a soft magnetic composite (SMC) material on the dc and ac HTS coil performances at cryogenic temperatures, GdBCO- and YBCO-based commercial tapes from different manufactures were used to assemble ten HTS coils in double-pancake configuration. These tapes were wound using two different core structures, i.e., fixed and movable cores, having the same circular shape but different diameters as well as materials, i.e., fiberglass and SMC. Critical currents and ac transport current losses of these coils were measured using the electrical method. To evaluate the parallel and perpendicular components of the profile of magnetic flux density for each assembled HTS coil, a finite element model has been developed using Maxwell 2D. Eventually, the performance of different coils for SuREM application was discussed.

Nanoscale Patterning of Carbon Nanotubes: Techniques, Applications, and Future.

Carbon nanotube (CNT) devices and electronics are achieving maturity and directly competing or surpassing devices that use conventional materials. CNTs have demonstrated ballistic conduction, minimal scaling effects, high current capacity, low power requirements, and excellent optical/photonic properties; making them the ideal candidate for a new material to replace conventional materials in next‐generation electronic and photonic systems. CNTs also demonstrate high stability and flexibility, allowing them to be used in flexible, printable, and/or biocompatible electronics. However, a major challenge to fully commercialize these devices is the scalable placement of CNTs into desired micro/nanopatterns and architectures to translate the superior properties of CNTs into macroscale devices. Precise and high throughput patterning becomes increasingly difficult at nanoscale resolution, but it is essential to fully realize the benefits of CNTs. The relatively long, high aspect ratio structures of CNTs must be preserved to maintain their functionalities, consequently making them more difficult to pattern than conventional materials like metals and polymers. This review comprehensively explores the recent development of innovative CNT patterning techniques with nanoscale lateral resolution. Each technique is critically analyzed and applications for the nanoscale‐resolution approaches are demonstrated. Promising techniques and the challenges ahead for future devices and applications are discussed.

Polysiloxane Cross‐Linked Mechanically Stable MXene‐Based Lithium Host for Ultrastable Lithium Metal Anodes with Ultrahigh Current Densities and Capacities

AbstractThe applications of lithium metal anode are limited by uncontrollable lithium dendrite growth and infinite volume changes during cycling. These fundamental issues are exacerbated at high cycling current densities and capacities. Herein, a mechanically stable and resilient lithium metal host is fabricated by covalently cross‐linking a highly‐conductive and lithiophilic MXene/silver nanowire scaffold through a silylation reaction between MXene nanosheets and polysiloxane. Compared with the control sample (an MXene scaffold assembled by weak van der Waals forces), the covalently cross‐linked MXene scaffold displays excellent mechanical strength and resilience, which is conducive to buffer the large internal stress fluctuations generated during rapid and deep lithium plating‐stripping and guaranteed that the integrated framework structure is maintained during long‐term charging‐discharging cycles. When used in a symmetric cell, the lithium composite anode based on the covalently cross‐linked MXene host affords an unprecedented cyclic lithium plating‐stripping stability of a record‐high 3000 h lifespan at an ultrahigh current density (20 mA cm−2) and areal capacity (10 mAh cm−2). When this composite anode is coupled with a LiNi0.5Co0.2Mn0.3O2cathode, the full cell delivers an ultrahigh rate of 10 C for up to 1000 cycles, with an average capacity decay of 0.043% per cycle and a stable Coulombic efficiency of 98.7%.

Non-planar coil winding angle optimization for compatibility with non-insulated high-temperature superconducting magnets

The rapidly emerging technology of high-temperature superconductors (HTS) opens new opportunities for the development of non-planar non-insulated HTS magnets. This type of HTS magnet offers attractive features via its simplicity and robustness, and is well suited for modest size steady-state applications such as a mid-scale stellarator. In non-planar coil applications the HTS tape may be subject to severe hard-way bending strain ( $\epsilon _{\textrm {bend}}$ ), torsional strains ( $\epsilon _{\textrm {tor}}$ ) and magnetic field components transverse to the HTS tape plane ( $B_{\perp }$ ), all of which can limit the magnet operating space. A novel method of winding angle optimization is here presented to overcome these limitations for fixed input non-planar coil filamentary geometry. Essentially, this method: (i) calculates the peak $\epsilon _{\textrm {bend}}$ and $B_{\perp }$ for arbitrary winding angle along an input coil filamentary trajectory, (ii) defines a cost function including both and then (iii) uses tensioned splines to define a winding angle that reduces $\epsilon _{\textrm {tor}}$ and optimizes the $\epsilon _{\textrm {bend}}$ and $B_{\perp }$ cost function. As strain limits are present even without $B_{\perp }$ , this optimization is able to provide an assessment of the minimum buildable size of an arbitrary non-planar non-insulating HTS coil. This optimization finds that for standard 4 mm wide HTS tapes the minimum size coils of the existing HSX, NCSX and W7-X stellarator geometries are around 0.3–0.5 m in mean coil radius. Identifying the minimum size provides a path to specify a mid-scale stellarator capable of achieving high-field or high-temperature operation with minimal HTS tape length. For coils larger than this size, strain optimization allows use of wider (higher current capacity) HTS tapes or alternatively permitting a finite (yet tolerable) strain allows reduction of $B_{\perp }$ . Reduced $B_{\perp }$ enables a reduction of the HTS tape length required to achieve a given design magnetic field or equivalently an increase in the achievable magnetic field for fixed HTS tape length. The distinct considerations for optimizing a stellarator coilset to further ease compatibility with non-insulated HTS magnets are also discussed, highlighting relaxed curvature limits and the introduction of limits to the allowable torsion.

Research progress of electrical properties based on carbon nanotubes; interconnection

As an important part of the information revolution, integrated circuits have been developing in a short, light, and high-integration direction in recent years. According to the international semiconductor technology route, copper has encountered bottlenecks in the 22-nm technology node and it is difficult to keep up with the data throughput of processors. The increase of Cu resistivity is aggravated by the problems such as electron scattering, and the mass transfer along interface and grain boundary is one of the most urgent problems to be solved for future technology. Carbon nanotubes are expected to be the next generation of VLSI interconnects due to its large average electron mean free path at micron-scale, high thermal conductivity and current carrying capacity. In this review, we highlight the electrical properties of carbon nanotubes interconnection and interconnection between carbon nanotubes and metal and give a description of the specific processes, advantages and disadvantages of each interconnection technology. The purpose is to provide some useful information and inspiration for future research work of carbon nanotubes interconnection.

Towards a high-performance garnet-based solid-state Li metal battery: A perspective on recent advances

Garnet-based solid-state Li metal batteries have been widely considered one of the most promising next-generation energy storage systems. However, the performance of these batteries is plagued by various limitations caused by the solid-state electrolyte (SSE). The poor wetting of lithium on the garnet surface diminishes the contact between the anode and electrolyte, leading to extremely high anode interfacial resistance. Similarly, the point-to-point contact between the cathode and electrolyte leads to high impedance on the cathode side. Moreover, although the SSE serves a firm barrier separating the anode and cathode, lithium dendrites can still grow through, causing a short circuit. Finally, the solid/solid interface cannot be well maintained under cycling at high current density and capacity. Recently, remarkable progress has been achieved in garnet electrolyte to resolve these problems towards the aim of a high-performance solid-state Li metal battery. In this perspective, we highlight various recent advances in the field of garnet-based solid-state battery, including improving the anode/electrolyte interface, lithium dendrite detection, reducing cathode impedance, and electrolyte architecture design.

Scalable Synthesis of LiF‐rich 3D Architected Li Metal Anode via Direct Lithium‐Fluoropolymer Pyrolysis to Enable Fast Li Cycling

Lithium metal anode holds an important position in fast‐charging batteries. But lithium dendrite issues tend to exacerbate at high currents. LiF can be considered as an effective way to improve the Li metal surface electrochemical stability to achieve high power and high energy. However, most of reported work are relying on in situ formation of a 2D LiF on Li metal in liquid electrolyte, which limits the scalability and plated Li quantity. Here, we address this challenge and report a scalable synthesis of LiF‐rich 3D architected Li metal anode via a direct pyrolysis of molten lithium and fluoropolymer to enable fast Li charging with high current density (20 mA cm−2) and high areal capacity (20 mAh cm−2). The 3D structure is synthesized by the pyrolysis of fluoropolymer with Li metal and results show high similarity to the pristine electrolyte‐derived solid‐electrolyte‐interphase (SEI). This concept using pyrolysis of fluoropolymer with Li‐containing active materials could be also extended to modify Li metal oxide cathode (e.g., LiNi0.5Mn1.5O4) for mixed conductive interphase and engineer Li solid ion conductors (e.g., Li garnet‐type oxides) for interface stabilization and framework design.

Effect of Pressure on Lithium Metal Deposition and Stripping against Sulfide-Based Solid Electrolytes.

Fundamental challenges for lithium metal anode cycling against solid electrolytes (SEs) at high current densities and high areal capacities include lithium dendrite penetration during Li deposition and void formation during Li stripping. These two dynamic processes have a distinct dependency on the external pressure. The majority of research to date on Li cycling behaviors adopt symmetric cell (Li/SE/Li) configurations, where the stack pressure and the failure associated with the deposition and the stripping processes cannot be delineated. In this work, we investigate the effect of external pressure on the deposition and the stripping of Li metal anodes separately against a sulfide-based SE by employing asymmetric cell configurations. We show that (1) for Li striping, the pressure required is positively correlated with stripping current densities; (2) for Li deposition, higher pressure leads to lower maximum allowed current densities, defined as the current densities beyond which dendrite penetration occurs. The apparent opposing requirement for external pressure of Li deposition and Li stripping elucidates why the methodology of Li metal cycling in symmetric cell configurations is fundamentally flawed and highlights the importance of refined pressure regulation in all-solid-state Li metal batteries.

Structure and Mechanical Properties of Bimetal Nb/Cu Rods for Production of Nb3Sn Superconductors

To construct magnetic systems in modern high-energy physics projects, such as creation of the Future Circular Collider (FCC) and modernization of the Large Hadron Collider (HL-LHC), Nb3Sn superconductors with a high level of electrophysical properties, above all being a high current carrying capacity, are requisite. Such multifilament Nb3Sn superconductors are obtained by the technique of internal feeding of tin (IFT), consisting in deformation of a composite including high-purity niobium, copper, and tin to make a wire smaller less than 1 mm in diameter. The presence of such components as tin-based alloys or pure tin with Tm = 232°C in the composite wire composition precludes the possibility of Nb recrystallization annealing, which imposes strict requirements on the Nb mechanical properties, which determine the Nb capability for plastic deformation. In the study, the influence of the design and conditions of creating bimetal Nb/Cu rods on the grain structure of niobium and the state of the boundary between it and a copper sheath is discussed. The mechanical properties of rods at different steps of their fabrication are investigated. The results will be applied in development of the technological conditions of manufacture of Nb3Sn superconductors by the IFT technique.