High Current Density Research Articles

NiFe-based electrocatalysts toward high-current–density overall water electrolysis

NiFe-based electrocatalysts toward high-current–density overall water electrolysis

A composite anode based on intercalation and conversion mechanism for high-rate lithium-ion batteries

To increase the specific capacity and cycle stability of lithium-ion batteries at high current density, we have investigated the anode materials. Among them, black phosphorus has attracted attention because of its large theoretical specific capacity (2596 mA h/g). However, the moderate conductivity of black phosphorus itself makes it less effective. The addition of graphite to form P-C and P-O-C bonds with black phosphorus enhances the performance of the battery cell. Lithium ions are primarily stored in black phosphorus-graphite layered structural materials via an intercalation mechanism, which improves electrochemical performance at tiny current density but is inadequate for charge/discharge cycling at high current density. In addition, lithium ions also can undergo conversion mechanism with metal oxide materials (e.g. Tungsten trioxide). While this conversion mechanism enables more stable battery cycling at high current density, the specific capacity remains insufficiently high. Higher charge/discharge specific capacity and long cycle stability of lithium-ion batteries at high current density can be realized by the joint action of the two mechanisms. In this work, black phosphorus, graphite, and tungsten trioxide (BP/G/WO3) composites are prepared by ball milling method. A comprehensive series of electrochemical analyses reveals that the BP/G/WO3-532 electrode (BP, graphite, and WO3 mass ratio of 5:3:2) exhibits the most substantial enhancement in the cycling stability of lithium-ion batteries. The anode exhibits a high specific capacity of 1463.1 mA h/g at 6 A/g and presents a retention capacity of 1159.8 mA h/g after 300 charge/discharge cycles, indicating a high cycle stability and fast reaction kinetics. This result is mainly attributed to the joint action of two mechanisms of composites.

Revealing interfacial degradation of Bi2Te3-based micro thermoelectric device under current shocks

Micro thermoelectric devices (micro-TEDs) offer great potential for IoT and electronic thermal management. However, they face challenges with reliability under high current densities. This study elucidates the failure mechanisms of Bi2Te3-based micro-TEDs subjected to current shocks. Experimental results indicate that at a high current density of 1800 A/cm2, the internal resistance of micro-TEDs increased by 12.9 % to 2.034 Ω. This led to a 52.0 % decrease in maximum output power at a 20 K temperature difference, dropping to 1.53 mW. Additionally, as the frequency of ON/OFF current applied to micro-TED increases, the resistance growth rate jumped from 0.764 mΩ/h for slow power cycling to 2.328 mΩ/h for fast power cycling. This indicates that higher cycling frequencies exacerbate the degradation of the device. In-situ TEM analysis revealed that current-induced elemental diffusion and electrical stress release led to the formation of NiTe2 nanoparticles and intergranular fractures within the Bi2Te3 materials. These results indicate that interfacial degradation and subsequent grain delamination are primary causes to micro-TED failure under current shocks. These findings underscore the significance of considering electrical stress in micro-TED design to enhance reliability and performance for high-power applications.

Wired for stability: evaluating the electrical performance of a solution-processed zinc oxide-modified silver nanowire transparent electrode.

Silver nanowires (AgNWs) have gained much attention owing to their optoelectronic and mechanical properties and are therefore potential candidates to tackle intrinsic drawbacks of currently applied transparent electrodes in various (opto)electronic devices. In order for AgNWs to be justifiably considered as viable, it is necessary to address their insufficient stability by coupling them with another constituent into a nanocomposite. For this purpose, ZnO was chosen because of its low cost, solution processability and barrier properties. In this paper, a fully solution processed AgNW/ZnO TE film was investigated in order to understand the effect of ZnO coating on the electrical stability of AgNWs, including the mechanism of degradation during their exposure to high electrical current densities. The nanocomposite transparent electrode was processed with ZnO coatings to determine their effect on its optoelectronic properties and electrical stability, where the ZnO triple coated AgNW demonstrated the best combination of optoelectronic properties and stability at the highest working voltage.

Conformal Li2O2 Growth and Decomposition Within 3D Lithiophilic Nanocages of Metal–Organic Frameworks for High‐Performance Li─O2 Batteries

AbstractLi─O2 batteries (LOBs) have the largest theoretical capacity among current batteries, but the irreversible growth and decomposition of Li2O2 products in positive electrodes cause dramatic degradation of their capacities over charging–discharging cycles. Herein, a metal–organic framework is reported with bipyridinic N linkers attached to graphene (bpyN‐MOF/g) as a positive electrode material to overcome the challenge. The bpyN‐MOF/g promotes conformal Li2O2 growth during discharging, while allowing Li2O2 decomposition at a low overpotential (0.487 V vs Li+/Li at 200 mA gc−1) during charging process, outperforming the Pt/C‐based electrode (0.857 V). Moreover, 3D‐tomography and density functional theory calculations consistently support the Li2O2 growth and decomposition mechanism inside bpyN‐MOF/g. Furthermore, bpyN‐MOF/g//Li LOBs achieve an exceptional discharge capacity (17 275 mAh gc−1 at 100 mA gc−1) and steady cycling for 270 cycles at 1000 mAh gc−1 under 2000 mA gc−1. Additionally, high gravimetric capacity at low mass loadings (0.27–0.44 mg cm−2) and stable cycle operation at a high areal current density (0.5 mA cm−2) open new opportunities for various practical applications.

Dahlia ball shape bimetallic phosphide-tungsten phosphide composite for anion-exchange membrane water electrolysis

Revolutionizing Water Splitting: Introducing a Breakthrough Single Heterostructure Catalyst for Highly Efficient Hydrogen and Oxygen Evolution Reactions. In this study, we present an innovative method for water splitting that introduces a remarkable single heterostructure catalyst capable of efficiently catalyzing both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Our research utilizes a highly effective hydrothermal synthesis technique to create a unique nanosphere composed of iron cobalt phosphide and tungsten phosphide (FCPWP). This FCPWP nanosphere exhibits finely tuned electronic structures and incorporates multiple active sites, resulting in significantly reduced overpotentials. When operating at current densities of 50 and 100 mA cm−2, the HER overpotentials are as low as 220 mV and 280 mV, respectively, while the OER overpotentials are only 270 mV and 350 mV. By employing the FCPWP nanosphere in a two-electrode electrolyzer configuration, we achieve exceptional results with minimal power requirements. At an operating current density of 10 mA cm−2, the electrolyzer functions at an impressively low voltage of 1.44 V, and at 1.85 V, it attains a high current density of 425 mA cm−2, showcasing an outstanding cell efficiency of 71.63% in an anion exchange membrane electrolyzer. These experimental findings are further supported by computational study. The FCPWP nanosphere emerges as an extraordinary electrocatalyst with dual-functionality for water splitting, offering great promise in the efficient production of hydrogen through electrochemical means. Our research not only introduces a fresh perspective but also paves the way for significant advancements in renewable energy technologies.

Frustrated Lewis Pair Mediated f‐p‐d Orbital Coupling: Achieving Selective Seawater Oxidation and Breaking *OH and *OOH Scaling Relationship

The development of materials for hydrogen production via seawater electrolysis at high current densities plays a crucial role in producing renewable hydrogen energy. However, during the seawater electrolysis process, the anode inevitably undergoes chloride oxidation reaction (ClOR) due to Cl‐ adsorption, making the seawater electrolysis process difficult to sustain. Inspired by the selective permeability of cell membranes, we propose a biomimetic design of frustrated Lewis pairs (FLPs) layers. Combining experimental results and molecular dynamics simulations, it has been demonstrated that cerium dioxide layers with FLPs sites can decompose water molecules, capture hydroxyl anions, and repel chloride ions simultaneously. DFT theoretical analysis indicates that the FLP sites regulate the Ce 4f‐O 2p‐Ni 3d gradient orbital coupling, providing additional oxygen non‐bonding (ONB) to stabilize the Ni‐O bond and optimize the adsorption strength of intermediates, thereby breaking the *OH and *OOH scaling relationship. Assembled anion exchange membrane electrolyzers exhibit an efficiency of 95.7% at a current density of 0.1 A cm‐2 and can stably operate for 250 hours at a current density of 0.2 A cm‐2.

Flooding Control by Electrochemically Reduced Graphene Oxide Additives in Silver Catalyst Layers for CO2 Electrolysis.

Electrolyte flooding in porous catalyst layers on gas diffusion electrodes (GDE) limits the stability and high-current performance of CO2 and CO electrolyzers. Here, we demonstrate the in situ electroreduction of graphene oxide (GO) to reduced graphene oxide (r-GO) within a silver catalyst layer on a carbon GDE. The r-GO introduces hydrophobicity regions in the catalyst layer that help mitigate electrolyte flooding during high current density CO2 electrolysis to CO. The flooding-resistant r-GO/Ag-coated GDE achieves a sustained Faradaic efficiency of CO at 94% for more than 8 h, compared to a rapid drop from 95% to 66% in an Ag-coated GDE without r-GO at 100 mA·cm-2. We found that GO enhances the electrochemically active surface area of the catalyst layer during CO2 electrolysis tests because the incorporation of GO increases the roughness of the catalyst layer. The in situ method of electrochemically reducing GO to r-GO provides a low-cost, practical approach that can be applied during standard spray-deposition procedures to develop flooding-resistant GDEs.

Frustrated Lewis Pair Mediated f-p-d Orbital Coupling: Achieving Selective Seawater Oxidation and Breaking *OH and *OOH Scaling Relationship.

The development of materials for hydrogen production via seawater electrolysis at high current densities plays a crucial role in producing renewable hydrogen energy. However, during the seawater electrolysis process, the anode inevitably undergoes chloride oxidation reaction (ClOR) due to Cl- adsorption, making the seawater electrolysis process difficult to sustain. Inspired by the selective permeability of cell membranes, we propose a biomimetic design of frustrated Lewis pairs (FLPs) layers. Combining experimental results and molecular dynamics simulations, it has been demonstrated that cerium dioxide layers with FLPs sites can decompose water molecules, capture hydroxyl anions, and repel chloride ions simultaneously. DFT theoretical analysis indicates that the FLP sites regulate the Ce 4f-O 2p-Ni 3d gradient orbital coupling, providing additional oxygen non-bonding (ONB) to stabilize the Ni-O bond and optimize the adsorption strength of intermediates, thereby breaking the *OH and *OOH scaling relationship. Assembled anion exchange membrane electrolyzers exhibit an efficiency of 95.7% at a current density of 0.1 A cm-2 and can stably operate for 250 hours at a current density of 0.2 A cm-2.

Electrosynthesis of Amino Acids from Biomass and Nitrate at Industrial Current Densities Using Porous PbBi Electrodes.

Electrosynthesis is a rising and attractive method for efficient amino acid production. However, industrial-grade electrosynthesis of high-value amino acids from simple carbon and nitrogen substrates is confronted with a great challenge. Herein, we design a dual-site PbBi alloy catalyst for various amino acids' electrosynthesis from keto acids and nitrate. An alanine Faradaic efficiency of 59.7% is delivered at -1.5 V vs SCE, reaching the industrial current density of 570 mA cm-2 with high catalytic durability of the porous Pb1Bi0.1 catalyst. In the tandem reaction process, nitrate is first converted to NH2OH via electrochemical reduction mainly over the Bi site. Then the obtained NH2OH integrates with the α-keto acid to form the oxime intermediate. Lastly, the Pb site facilitates the electroreduction of oxime to the final amino acids. More importantly, over 10 kinds of α-amino acids can be successfully synthesized in excellent FE and high yield at high current density, indicating the superior catalytic activity and wide universality of our strategy. In short, this work opens up a novel approach to realize the one-pot electrosynthesis of various amino acids from renewable biomass feedstocks and nitrate waste industrially.

Impact of Laser Ablation Strategies on Electrochemical Performances of 3D Batteries Containing Aqueous Acid Processed Li(Ni0.6Mn0.2Co0.2)O2 Cathodes with High Mass Loading

Lithium-ion batteries are currently one of the most important energy storage devices for various applications. However, it remains a great challenge to achieve both high energy density and high-power density while reducing the production costs. Cells with three-dimensional electrodes realized by laser ablation are proven to have enhanced electrochemical performance compared to those with conventional two-dimensional electrodes, especially at fast charging/discharging. Nevertheless, laser structuring of electrodes is still limited in terms of achievable processing speed, and the upscaling of the laser structuring process is of great importance to gain a high technology readiness level. In the presented research, the impact of different laser structuring strategies on the electro-chemical performance was investigated on aqueous processed Li(Ni0.6Mn0.2Co0.2)O2 cathodes with acid addition during the slurry mixing process. Rate capability analyses of cells with laser structured aqueous processed electrodes exhibited enhanced performance with capacity increases of up to 60 mAh/g at high current density, while a 65% decrease in ionic resistance was observed for cells with laser structured electrodes. In addition, pouch cells with laser structured acid-added electrodes maintained 29–38% higher cell capacity after 500 cycles and their end-of-life was extended by a factor of about 4 in contrast to the reference cells with two-dimensional electrodes containing common organic solvent processed polyvinylidene fluoride binder.

High current density 1.2 kV-class HfO2-gated vertical GaN trench MOSFETs

High current density 1.2 kV-class HfO₂-gated vertical GaN trench MOSFETs

A critical evaluation of platinum deposition techniques for hydrogen production in microbial electrolysis cells

Despite its high cost, Pt is the usual catalyst for hydrogen production in the cathode of Microbial Electrolysis Cells (MECs). Its effectiveness depends not only on the amount deposited but also on the availability and distribution of Pt nanoparticles on the cathode surface. This work provides a comprehensive study of the effectiveness of the Pt coating with five deposition techniques: spray, electrospray, brush painting, doctor blade and sputtering. The performance of the cathodes was studied with different Pt loadings by monitoring the current intensity and H2 production in MECs. Furthermore, cathodes were characterized morphologically using scanning electron microscopy together with energy-dispersive X-ray spectroscopy to study their Pt surface distribution and composition. Sputtering was initially discarded due to Pt detachment. When using the same amount of Pt (0.50 mg Pt cm−2), the highest current density was obtained for electrospray (2.0 mA cm−2), followed by spray (1.9 mA cm−2), brush painting (1.6 mA cm−2) and doctor blade (1.2 mA cm−2). Hence, electrospray improved 20 % the results obtained by the default method of brush painting. Electrospray and spray provided better performance because of the direct deposition of Pt on the carbon fibres creating a compact Pt layer on the electrode surface. Furthermore, it was observed that the cell performance decreased significantly with decreasing amount of Pt per cm2, observing the best performance with the highest Pt load tested (0.5 mg Pt cm−2) regardless of the deposition technique.

A Self-Healing, Flowable, Yet Solid Electrolyte Suppresses Li-Metal Morphological Instabilities.

Lithium metal (Li0) solid-state batteries encounter implementation challenges due to dendrite formation, side reactions, and movement of the electrode-electrolyte interface in cycling. Notably, voids and cracks formed during battery fabrication/operation are hot spots for failure. Here, a self-healing, flowable yet solid electrolyte composed of mobile ceramic crystals embedded in a reconfigurable polymer network is reported. This electrolyte can auto-repair voids and cracks through a two-step self-healing process that occurs at a fast rate of 5.6µm h-1. A dynamical phase diagram is generated, showing the material can switch between liquid and solid forms in response to external strain rates. The flowability of the electrolyte allows it to accommodate the electrode volume change during Li0 stripping. Simultaneously, the electrolyte maintains a solid form with high tensile strength (0.28MPa), facilitating the regulation of mossy Li0 deposition. The chemistries and kinetics are studied by operando synchrotron X-ray and in situ transmission electron microscopy (TEM). Solid-state NMR reveals a dual-phase ion conduction pathway and rapid Li+ diffusion through the stable polymer-ceramic interphase. This designed electrolyte exhibits extended cycling life in Li0-Li0 cells, reaching 12000 h at 0.2mA cm-2 and 5000 h at 0.5mA cm-2. Furthermore, owing to its high critical current density of 9mA cm-2, the Li0-LiNi0.8Mn0.1Co0.1O2 (NMC811) full cell demonstrates stable cycling at 5mA cm-2 for 1100 cycles, retaining 88% of its capacity, even under near-zero stack pressure conditions.

Construction of composite lithium with high adhesion work and fast ionic conductivity by black phosphorus for solid-state lithium batteries

Li6.4La3Zr1.4Ta0.6O12 (LLZTO) based solid-state lithium metal batteries (SSLMBs) have a broad application prospect because of the nonflammable nature as well as the high energy density. However, the loose contact and the contact degradation of Li/LLZTO in the stripping process result in the serious lithium dendrites growth. Herein, these issues are addressed by a composite lithium anode (CLA), which is prepared through the reaction between black phosphorus and molten lithium. In comparison to pure lithium, a higher adhesion work (722.67 mJ m−2) and Li+ diffusion coefficient (2.45×10−12 cm2 s−1) are achieved for CLA, thus assuring the intimate interfacial contact of CLA/LLZTO interface during the lithium stripping process. As a result, a small interfacial resistance of 3.7 Ω cm2, a high critical current density of 1.5 mA cm−2, and extra-long cycle life of 8200 h at 0.3 mA cm−2 are achieved for CLA symmetric cell at 25 ºC. More importantly, the full cell coupled with high mass loading LiFePO4 cathode (10.6 mg cm−2) still shows a large discharge capacity of 156.3 mAh g−1 and cycles stably at 25 ºC. This work provides an alternative approach to develop the long lifespan and high capacity of SSLMBs.

A Versatile InF3 Substituted Argyrodite Sulfide Electrolyte Toward Ultrathin Films for All‐Solid‐State Lithium Batteries

AbstractAll‐solid‐state lithium batteries (ASSLBs) incorporating sulfide solid electrolytes capture great attention due to their intrinsic safety features and high energy density. Nevertheless, the implementation of sulfide solid electrolytes faces significant challenges, including moisture sensitivity, narrow intrinsic electrochemical windows, and excessively thick solid electrolyte layers. Here, the substitution of In for P and F for Cl in argyrodite sulfide Li5.7PS4.7Cl1.3 is presented. With appropriate elemental substitutions, the Li symmetric cells exhibit a high critical current density value of 2.5 mA cm−2 and deliver prolonged plating/stripping over 1000 h at 1 mA cm−2 and 25 °C. Further, the Li5.82P0.94In0.06S4.7Cl1.12F0.18 displays high chemical stability toward organic solvents, which is further demonstrated by the density functional theory (DFT) calculations. Using polyisobutylene as a binder, a uniform sulfide film (35 µm) is prepared by slurry casting and hot pressing process, delivering a high ionic conductivity of 1.4 mS cm−1 at 25 °C. Coupled with FeS2 and LiCoO2 cathode, the all‐solid‐state lithium metal cell exhibits a long cycling life and excellent rate performance. This study provides a design strategy and reveals the importance of high‐performance sulfide SEs in the scalable production of sulfide film.

Enhanced carbon host with N-reinforced S-sites to catalyze rapid iodine conversion kinetics for Zn-I2 battery

Aqueous zinc-iodine (Zn-I2) battery is a promising energy storage system in the establishment of a low-carbon, clean society, but they are limited by unsatisfied reversible capacity and poor cycle life. Ultimately, this is due to the poor iodine conversion kinetics and the shuttle effect of the intermediate polyiodide. Herein, a N-reinforced S-site carbon host (labeled as NS-YP80F) is designed to resolve these issues. DFT calculation shows that the electrochemical activity of the NS-YP80F with abundant S-site can be further enhanced by introducing N-atom at the original S-site. The synergistic effect of N-reinforced S-site carbon host cannot only enhance the adsorption of polyiodide to avoid the shuttle effect, but also induce the smooth conversion of iodine through enhanced catalytic mechanism. Consequently, the Zn-I2 battery with NS-YP80F@I2 cathode shows high reversible capacity (127 mAh g−1 at 1C) and stable cycling lifespan (15,000 cycles) with a high current density of 50 C. This strategy achieved a breakthrough in the electrochemical activity of the heteroatom doping carbon hosts, and provided a simple and effective solution for optimizing the performance of Zn-I2 battery.

Silver Nanowire Aerogel Support Promotes Stable Hydrogen Evolution Reaction at High Current Density.

The stability of electrocatalysts during the hydrogen evolution reaction (HER) is vital for efficient production of hydrogen energy. Herein, we demonstrate that silver nanowire aerogel-based support (AABS) could facilitate the construction of HER catalysts with extraordinary long-term stability. A full nanostructure catalyst of nickel phosphide based formed on AABS (Ni2P-Ni5P4@AABS) was prepared to achieve an overpotential of 687 mV (without iR compensation) for HER at the current density of 1 A cm-2 in 0.5 M H2SO4. Excitingly, the stable HER performance was kept for 42 days during the long-term stability (i-t) test at high current density (0.5-1 A cm-2). The excellent HER performance of the Ni2P-Ni5P4@AABS catalyst is attributed to rapid electron transport pathways, numerous more accessible active sites, and support induced enhanced catalytic activity. The support effect was highlighted by a proposed phenomenological two-channel model for electron transport, which provides fresh insights into the design strategy for energy storage and delivery.

In‐Situ Constructing a Mixed‐Conductive Interfacial Protective Layer for Ultra‐Stable Lithium Metal Anodes

Lithium metal batteries are the most promising next‐generation energy storage technologies due to their high energy density. However, their practical application is impeded by serious interfacial side reactions and uncontrolled dendrite growth of lithium metal anode. Herein, copper 2,4,5‐trifluorophenylacetate is designed and explored to stabilize lithium metal anode by in‐situ constructing a dense and mixed‐conductive interfacial protective layer. The formed passivated layer not only significantly inhibits interfacial side reactions by avoiding direct contact between lithium metal anode and electrolyte but also effectively suppresses lithium dendrite growth due to the unique inorganic‐rich compositions and mixed‐conductive properties. As a result, the copper 2,4,5‐trifluorophenylacetate‐treated lithium metal anodes show greatly improved cycle stability under both high current density and high areal deposition capacity. Notably, the assembled liquid symmetrical cells with copper 2,4,5‐trifluorophenylacetate‐treated lithium metal anodes can stably work for more than 3000, 5000, and 4800 h at 1.0 mA cm−2–1.0 mAh cm−2, 2.0 mA cm−2–5.0 mAh cm−2, and 10 mA cm−2–5.0 mAh cm−2, respectively. Furthermore, the assembled liquid full cell with a high LiFePO4 loading (~16.9 mg cm−2) shows a significantly enhanced cycle life of 250 cycles with stable Coulombic efficiencies (>99.1%). Moreover, the assembled all‐solid‐state lithium metal battery with a high LiNi0.6Co0.2Mn0.2O2 loading (~5.0 mg cm−2) also exhibits improved cycle stability. These findings underline that the copper 2,4,5‐trifluorophenylacetate‐treated lithium metal anodes show great promise for high‐performance lithium metal batteries.

Fluorine-doped carbon dots decorated on iron-cobalt selenide nanosheets as superior electrocatalysts for oxygen evolution in seawater

Developing oxygen evolution reaction (OER) catalysts that can efficiently and stably operate at high current densities in seawater electrolysis is urgently demanded but challenging. In this study, selenium-vacancies-rich iron-cobalt selenide nanosheets (FeCoSe-VSe) decorated with fluorine-doped carbon dots (FCDs) are rationally designed and prepared on nickel foams (NF) through the successive processes of hydrothermal treatment and selenization. Benefiting from the large accessible surface area and abundant active sites provided by FCDs and selenium vacancy defects, as well as the coupled interface between FCDs and FeCoSe-VSe that optimizes the oxygen adsorption energy and accelerates the kinetic process, the FCDs/FeCoSe-VSe/NF composite exhibits excellent OER catalytic activities with a low overpotential of 258 mV at a current density of 200 mA cm−2 in 1 M KOH and a small Tafel slope of 34.7 mV dec–1. In the electrolytes of simulated and natural seawater, the overpotentials of the FCDs/FeCoSe-VSe/NF electrode are slightly higher, measured to be 264 and 297 mV, respectively. More profoundly, the introduction of FCDs enhances the corrosion resistance of the catalyst in alkaline electrolytes, ensuring the long-term stability. This work offers a guidance to improve the electrochemical performances of catalysts for high-efficiency seawater oxidation.