High Current Cycling Research Articles

Understanding Durability of Polymer Electrolyte Membrane Water Electrolyzers

Hydrogen is positioned to play a pivotal role in the future energy landscape, bolstered by the increasing adoption of renewable energy sources. The U.S. Department of Energy (DOE) has initiated the Hydrogen earth shot, with a goal of achieving a cost target of $1 per kilogram of hydrogen within a decade. Polymer electrolyte membrane water electrolyzers (PEMWE) are at the forefront of enabling hydrogen production from renewable electricity. Yet, achieving the 80000 h operational lifetime remains a critical challenge for the commercial viability of PEMWE.1 An in-depth understanding of the conditions affecting the degradation of critical PEMWE components including the catalyst layer, membrane, and porous transport layers is crucial for achieving the durability target of PEMWE.In this study, we explore the effect of various operating conditions, such as temperature, pressure, and cycling vs. hold of voltage or current, and the membrane electrode assembly composition, including catalyst loading, membrane thickness, and incorporation of gas recombination catalyst (GRC), on degradation in PEMWE. To assess the degradation rate, our protocol involved long duration durability tests, alternating between high and low current density cycles with long holding periods and rapid cycling. Electrochemical characterization including polarization curve, electrochemical impedance spectroscopy, and cyclic voltammetry will be presented. Additionally, electron microscopy and X-ray spectroscopy analysis provides insight into changes in the catalyst layer. The second part of the study focuses on understating membrane degradation in PEMWEs. Through periodic analysis of the cathode and anode effluent water during long duration current density holds, the fluorine emission rate (FER) was estimated, a key metric for assessing membrane and ionomer loss. Preliminary investigation reveals that incorporation of GRC in the membrane reduces hydrogen crossover, thereby lowering the FER and the degradation rate. This study enhances our understanding of PEMWE degradation, offering critical data to develop accelerated stress test (AST) protocols.Acknowledgment:This research is supported by the U.S. Department of Energy (DOE) Hydrogen and Fuel Cell Technologies Office through the Hydrogen from Next-generation Electrolyzers of Water (H2NEW) consortium.Reference: Tomic, A. Z., Pivac, I., Barbir, F., Journal of Power Sources (2023) 557

Scalable Surface Micro-Texturing of LLZO Solid Electrolytes for Battery Applications

A challenge for lithium lanthanum zirconate (LLZO)-based solid-state batteries is to increase the critical current density (CCD) to enable high current cycling. A promising strategy is to modify the LLZO surface morphology to provide a larger contact area with Li metal. Examples of such modifying surface morphology include surface patterning through laser cutting [1] and roughening by shot peening [2]. However, these techniques still have challenges in scale-up and application to thin electrolyte layers. Surface patterning using a laser cutter leads to surface contamination requiring post-heat treatment in an inert atmosphere, and shot-peening has a potential risk of mechanical failure caused by impact stress, making it especially difficult to use for thin electrolytes.Here, we present an easily scalable process to prepare surface-textured thin LLZO electrolytes. The texturing process is a simple pressing of green LLZO tapes between micro-textured substrates. A variety of textures can be produced depending on the type of substrate, and texturing can be on either one side or both sides. For this work, after pressing and sintering, several micro-patterns are formed on thin LLZO (~118 μm thick). The properties of the various samples were characterized to investigate the impact of the surface texturing, and the most promising ones were selected for electrochemical testing in symmetrical lithium cells and full cells. Li symmetric cells using a coarse ridge-textured LLZO exhibit ~2.5 times increased CCD compared to planar non-textured LLZO, and a solid-state full cell shows stable cycling and improved rate performance. We believe this process offers a favorable tradeoff of processing complexity vs. structural optimization to maximize CCD.[1] Xu R, et al Adv. Mater., e2104009, 33(49), (2021)[2] Kodama M, et al J. Power Sources, 231556, 537 (2022)

Highly Effective Polyacrylonitrile-Rich Artificial Solid-Electrolyte-Interphase for Dendrite-Free Li-Metal/Solid-State Battery.

Lithium metal anode batteries have attracted significant attention as a promising energy storage technology, offering a high theoretical specific capacity and a low electrochemical potential. Utilizing lithium metal as the anode material can substantially increase energy density compared with conventional lithium-ion batteries. However, the practical application of lithium metal anodes has encountered notable challenges, primarily due to the formation of dendritic structures during cycling. These dendrites pose safety risks and degrade battery performance. Addressing these challenges necessitates the development of a reliable and effective protection layer for lithium metal. This study presents a cost-effective and convenient method to spontaneously produce lithium metal protective layers by creating polymeric layers by using acrylonitrile (AN). This method remarkably extends 6× of the lifetime of lithium metal anodes under high current density (1 mA/cm2) cycling conditions. While the cycle life of bare lithium metal is approximately 150 h under high current cycling conditions, AN-treated lithium metal anodes exhibit an impressive longevity of over 900 h. The AN-treated lithium metal anodes are further integrated and tested with sulfide-based Li10GeP2S12 (LGPS) solid-state electrolytes to evaluate its interfacial stability at a solid-solid interface. The formation of the polyacrylonitrile (PAN)-rich ASEI, due to AN-treatment, effectively reduces and stabilizes the cell overpotential to only one-tenth of that with the interface without treatment. This strategy paves a route to enable a highly efficient and highly stable Li/LGPS solid-state battery interface.

Developing Rapid-Charging Li-S Batteries via "Target Catalysis" of Cations and Anions Modified Electrocatalyst.

The shuttle effect and sluggish sulfur reduction reaction have resulted in significantly low efficiency and poor high current cycling stability in lithium-sulfur batteries, impeding their practical applications. To address these challenges, the introduction of Ni cations into MoS2 grown on reduced graphene oxide (MoS2/rGO) induces the formation of impurity energy levels between the conduction and valence bands of MoS2. Additionally, the introduction of anionic Se expands the interlayer spacing, enhances intrinsic conductivity, and improves ion diffusion rates. Simultaneously introducing anionic and cationic species into the MoS2/rGO causes the center of the d-band to shift upward, reducing the occupancy of electrons in antibonding orbitals. This modification leads to a rearrangement of the electronic structure of Mo, accelerating the redox reactions of lithium polysulfides. It particularly enhances the binding energy and lowers the conversion energy barrier of Li2S4. Consequently, the Li||S coin cell with the Ni-MoSSe/rGO cathode demonstrates an initial capacity of 446 mAh g-1 at 20 C, with a remarkable capacity retention of ≈96.7% after 200 cycles. Moreover, even under high sulfur loading conditions (6.45 mg cm-2) and a low electrolyte/sulfur ratio (5.4 µL mg-2), it maintains a high areal capacity of 6.42 mAh cm-2.

Compositional Engineering of Lithium Metal Anode for High-Performance Garnet-Type Solid-State Lithium Battery.

Garnet-type solid-state lithium batteries (SSLBs) possess excellent potential owing to their safety and high energy density. However, fundamental barriers are deficient cycling stability and poor rate capability. The main concern lies in generating voids at the Li|garnet interface during Li stripping, stemming from the sluggish diffusion of Li atoms inside the bulk Li metal. Herein, a composite anode (AN@Li) containing Li-Al alloy, Li3N, and LiNO2 is designed by introducing aluminum nitrate into molten Li. The lower interfacial formation energies exhibited by Li-Al alloy, Li3N, and LiNO2 with garnet solid-state electrolyte (SSE) enhance the wettability of AN@Li toward SSE. Meanwhile, it affords efficient conductive pathways that facilitate Li+ diffusion in the bulk anode (not just on the surface). Impressively, the resulting symmetric cell with AN@Li electrodes achieves high critical current density (1.95mA cm-2) and long cycle life (6000h at 0.3mA cm-2). The SSLB coupled with LiFePO4 cathode and AN@Li anode enables stable cycling for 200 cycles at a high rate of 1 C with a retention of 96% and exhibiting outstanding rate capability (145.9 mAh g-1 at 2 C). This work provides practical insights for producing high-performance lithium metal anode for advanced garnet-type SSLBs.

A high current density and long cycle life iron-chromium redox flow battery electrolyte

A high current density and long cycle life iron-chromium redox flow battery electrolyte

Structural Modification Strategy for Enhancing Electrochemical Performance of Electrodes Under High Current Cycling and First Principle Computational Research for Electrode Materials

Recently, there has been significant interest in advancing lithium-ion battery technology due to its widespread use in various applications. Our research delves into this domain, focusing on enhancing the electrochemical properties of batteries through structural modification of electrode materials. Our work demonstrates the significant enhancements of electrochemical performance under high current cycling using structurally modified electrode materials . In first work, crumpled graphene oxide anode proves to be an effective strategy for enhancing its electrochemical properties, attributed to its advantageous crumpled morphology. This morphology allows for improved electrode stability and easier access for lithium ions, enabling them to interact with its larger specific surface area. In second work, we describe enhanced the drawback of reduced electrochemical performance during high-rate cycles by synthesizing multidimensional LFP-based carbon composite. The lithium ion diffusivity and electrode stability of the prepared composite are significantly improved in charging and discharging cycles by introducing graphene quantum dots alongside CNTs, exhibiting superior electrochemical properties even at high current densities. In third work, density functional theory simulation is employed for demonstrating the enhanced electrochemical properties of prepared electrodes by exploring their properties. Our research provides insights into electrode material design as an effective approach to enhancing the electrochemical properties of lithium-ion batteries.Acknowledgement:This work was supported by the National Research Foundation of Korea (NRF-2021R1A2C1008272). This work was supported by Ministry of Trade, Industry and Energy, KEIT, under the project title"International standard development of evaluation methods for nano-carbon-based high-performance supercapacitors for electric vehicles" (project # 20016144).

Polymerized Acrylonitrile Artificial SEI for Long-Life Li-Metal Battery and Enhanced Stability for Li/Li10GeP2S12 Interface

Lithium metal anode batteries have attracted significant attention as a promising energy storage technology, offering a high theoretical specific capacity and low electrochemical potential. Utilizing lithium metal as the anode material can substantially increase energy density compared to conventional lithium-ion batteries. However, the practical application of lithium metal anodes has encountered notable challenges, primarily due to the formation of dendritic structures during cycling. These dendrites pose safety risks and degrade battery performance. Addressing these challenges necessitates the development of a reliable and effective protection layer for lithium metal. This study presents a cost-effective and convenient method to produce lithium metal protective layers by creating ex-situ polymer layers using acrylonitrile (AN). This method extends the lifetime of lithium metal anodes by a remarkable factor of six under high current (1 mA/cm²) cycling conditions. While the cycle life of bare lithium metal is approximately 150 hours under high current conditions, AN-treated lithium metal anodes exhibit an impressive longevity of over 900 hours.Furthermore, with the increasing attentions on solid-state electrolytes – which address the safety concerns and energy density limitations associated with conventional liquid electrolytes in lithium-ion batteries, the interface between Li metal and solid-state electrolytes has been the major challenges. For example, Li10GeP2S12 (LGPS) stands out among these solid electrolyte materials, boasting high ionic conductivity (1 x 10⁻² S cm⁻¹). Nonetheless, the severe instability of the interface between lithium metal anodes and solid electrolytes, including dendrite formation and electrolyte degradation, hindering their practical implementation. This work also goes deeply to explore the stability and performance of Li | LGPS systems by utilizing a polymerized acrylonitrile interfacial. By elucidating the mechanisms governing the interfacial layers, this low-cost fabrication of AN-treated lithium metal holds significant potential for advancing the commercialization of future lithium-metal batteries, surpassing the capabilities of traditional lithium-ion batteries.

LiNO3-Based Deep Eutectic Mixtures Comprising Organic Additives As Promising Electrolytes for Stable Li-Metal Batteries

Deep eutectic electrolytes have emerged as a novel energy storage solution, presenting distinct advantages over traditional ionic liquid electrolytes. These advantages include a high ion concentration, cost-effective, wide electrochemical window, and inherent safety.In this study LiNO3, which is valuable additive but difficult to melt in carbonate electrolytes, was used as the lithium salt for a deep eutectic solvent (DES) electrolyte. LiNO3 demonstrated its capability to form deep eutectic solutions with N-methyl acetamide (N-MAc) and Methyl carbamate (MCB) in a 1:4 molar ratio. An suitable additives was introduced to study the effect on electrochemical behaviors.Li//Cu asymmetric cells was utilized to evaluate the coulombic efficiency (CE) of lithium plating/stripping with various electrolytes. The lithium plating/stripping stability is investigated by evaluating the cycle life of Li//Li symmetric cells. The electrochemical window is determined by the Li//Pt asymmetric cells underwent linear sweep voltammetry (LSV). A commercial LiMn2O4 (LMO) is used as cathode to assemble the Li//LMO lithium-metal cells to evaluate cycle stability, rate capabilities, and AC impedance. The physical properties of the electrolytes underwent systematic analysis using Fourier Transform Infrared Spectroscopy (FT-IR), Raman spectroscopy, Differential Scanning Calorimetry (DSC), conductivity, and viscosity measurements. Post-analysis of Li//Cu asymmetric cells revealed additive-induced differences. SEM and EDS analyses unveiled elemental variations on copper foil, and X-ray Photoelectron Spectroscopy (XPS) provided surface insights.For the first system, the LiNO3 and N-MAc electrolyte exhibited an extended plating/stripping cycle life of reaching 450 hours with the addition of 10 wt% VC in Li//Li symmetrical cell. Addition VC as additive significantly improved conductivity and viscosity. Surprisingly, in Li//Cu asymmetrical cells, 5 wt% VC demonstrated better stability. The Li//Pt asymmetrical cells shows the electrolyte decomposition is occurs at 5V, which is high compared to organic electrolyte. In Li//LMO lithium-metal cells, an impressive 2000 cycles were achieved, with a remarkable 80% capacity retention in rate capabilities testing at high current density and sustained cycling up to 1000 cycles at lower current density. Raman and FT-IR analysis revealed blue shifts in characteristic peaks of C=O and N-H, indicating lithium ions from LiNO3 indeed interact with N-MAc. SEM and EDS testing confirmed that the presence or absence of VC influenced lithium-ion deposition. In the presence of VC, there was a notable increase in oxygen, nitrogen, and carbon content, imply that the enhanced lithium-ion deposition and dissolution capabilities.For the second system, the LiNO3 and MCB electrolyte system, 8 wt% FEC addition in Li//Li symmetrical cells resulted in a cycle life of only 60 hours. Li//Cu asymmetrical cells showed improved lithium-ion deposition and dissolution with FEC for 12 cycled. Li//Pt asymmetrical cells displayed a decomposition at 4.6V. Li//LMO lithium-metal cells with 5 wt% FEC exhibited stability, cycling up to 120 cycles. Raman and FT-IR analysis indicated blue shifts in the characteristic peaks of C=O and N-H stretching vibrations, signifying deep eutectic interactions between LiNO3 and MCB. Red shifts were observed in N-H bending vibrations. FEC addition improved conductivity and viscosity. SEM and EDS testing demonstrated that the presence or absence of FEC affected lithium-ion deposition. In the presence of FEC, components such as oxygen, nitrogen, carbon, and fluorine were detected, with fluorine constituting a significant 26.70%, indicating improved lithium-ion deposition and dissolution capabilities. XPS peaks corresponding to Li 1s, F 1s, and N 1s, affirming the efficacy of FEC in promoting lithium-ion deposition.In conclusion, the deep eutectic electrolyte formed by LiNO3 and N-MAc in a 1:4 molar ratio demonstrated superior stability. Additives proved effective in improving electrolyte properties without compromising coordination. Both electrolytes exhibited comparable cycle life, emphasizing their suitability for positive electrode materials like LMO. Moreover, sustained high current density in rate capabilities testing further highlighted their potential for practical applications. Figure 1

Transient Mechanism Analysis of Three-Dimensional Zinc-Nickel Single Flow Battery Based on Different Negative Electrode Structures

On the basis of the mass, momentum, charge conservation equations, in addition to coupled with the global reaction kinetic equations, a transient three-dimensional mechanistic analytical model of zinc-nickel single flow batteries (ZNBs), which comprehensively takes into account the hydrogen and oxygen evolution side reactions, the polarization distribution, as well as the structural effects of the pole lugs, is developed in this paper. After grid independence validation and experimental verification, the polarization distribution, side-reaction current density, and battery efficiency of ZNBs at high current density and multiple cycles of charging and discharging were comparatively analyzed based on this model with different anode materials of nickel sheet (NS) and porous nickel foam (NF). Subsequently, the effects of changes in negative electrode porous nickel foam thickness and porosity on battery polarization, side-reaction current density and battery efficiency were further investigated. Finally, the performance of the battery under the optimal battery state was studied. The results showed that the NF negative electrode effectively reduced the battery polarization, suppressed the battery side reactions as well as improved the battery efficiency under high current density and multiple cycles of charging and discharging, which improved the efficiency and stability of the battery.

In Situ Construction of a Hydrophobic Honeycomb-like Structured ZnMoO4 Coating Applied for Enhancing Zinc Anode Performance.

Aqueous zinc-ion batteries (AZIBs) suffer from sharp cycling deterioration due to serious interfacial side reactions and corrosion problems on the zinc anode. Herein, an efficacious approach to construct hydrophobic ZnMoO4 coatings on Zn (denoted as Zn@ZMO) is proposed to mitigate direct contact between the zinc anode and electrolyte and enhance its cycle life. The hydrophobic ZnMoO4 layer (contact angle = 128°) with a honeycomb-like structure is prepared by an in situ liquid phase deposition method. The as-prepared ZnMoO4 coating exhibits persistent corrosion protection for Zn through 30 days of immersion in a 2 M ZnSO4 electrolyte, indicating excellent stability of the ZnMoO4 layer and ensuring its available application in AZIBs. Unique microchannels in this kind of honeycomb-like structured coating favor Zn2+ ion diffusion and ease of ion transport, especially at high current cycling. Its robust surface exclusion can effectively counter other side reactions induced by water, simultaneously. As a result, the Zn@ZMO symmetrical cell shows a remarkable cycle lifespan exceeding 2700 h at 1 mA cm-2/1 mA h cm-2, surpassing that of the bare zinc cell by more than 100 folds. At a current density of 5 A g-1, the Zn@ZMO//V2O5 cell can still achieve a specific capacity of 167.0 mA h g-1 after 500 cycles with a capacity retention rate of 88%, which demonstrates its long-term cycling stability.

Self‐discharge in supercapacitors. Part I: Conway's diagnostics

AbstractSupercapacitors have emerged as drivers for the advancement of green energy technologies in energy storage systems and energy‐efficient devices. Their ability to rapidly acquire and deliver charge at high current densities and long cycle life is key. However, their high self‐discharge rates prevent their potential use in a wide range of applications, especially when utilizing commonly available activated carbon electrodes. Addressing this bottleneck is hindered by the lack of a comprehensive understanding of the self‐discharge processes. In this article, we provide a concise overview of various types of supercapacitors, followed by an exploration of self‐discharge phenomena within electrochemical systems. Recognizing the limited understanding at a molecular level, this article focuses on characterizing self‐discharge through the nature of the gradual decline in cell potential. We then survey the use of diagnostic methods in the literature to elucidate one or more controlling mechanisms operating during self‐discharge, facilitating a rational search for mitigation. We conclude by emphasizing the need for caution when interpreting controlling mechanisms solely based on cell potential measurements over time.This article is categorized under: Emerging Technologies > Energy Storage

Self‐discharge in supercapacitors. Part II: Factors influencing it and mitigation

AbstractSupercapacitors have emerged as drivers for the advancement of green energy technologies in energy storage systems and energy‐efficient devices. Their ability to rapidly acquire and deliver charge at high current densities and long cycle life is key. However, their high self‐discharge rate prevents their potential use in a wide range of applications, especially when utilizing commonly available activated carbon electrodes. Addressing this bottleneck is hindered by the lack of a comprehensive understanding of the discharge process. In this review, we delve into a comprehensive review of factors (temperature, initial voltage, charging conditions, history, functional groups, pore geometry, and the impurities present) that influence self‐discharge in supercapacitors and attempts made in the literature on its mitigation (electrode, electrolyte, and separator modification).This article is categorized under: Emerging Technologies > Energy Storage

Mechanism of Ionomer Degradation as a Consequence of Defective Anode PEMFC

Defects in the various components of the membrane-electrode assembly (MEA), initially present or created during aging, are known to be responsible for the short lifetime PEMFC. Catalytic layer degradation has been identified as one of them [1]. However, the possible propagation of these defects to other components within a cell or a stack is not clear in the literature. To shed light on these phenomena, customized MEAs with a localized lack of anode active layer at two different locations -near the hydrogen inlet or outlet- were manufactured and tested with specific accelerated aging tests, combining high and low current and humidity cycles; these were specifically tailored to observe a possible propagation of the defects [2]. Local performance monitoring using a segmented cell revealed variations within the catalytic layers upstream and downstream of the defect. In order to better understand the impact of anode active layer defects on MEA components, localized physicochemical analyses were performed post mortem along the gas flow, with the main objective to identify possible degradations of the reinforced perfluorosulfonic acid (PFSA) membranes. Microscopic thickness measurements showed significant membrane thinning in the defective segments. Difference of these localized degradations between the monopolar plates rib and channel zones will be highlighted depending on the defect location i.e. at the inlet and outlet of hydrogen flow (Figure below). In the defective area, decrease of the Ion Exchange Capacity estimated by Raman analyses is pointed out for the reinforced PFSA layer. The PFSA chain degradation mechanism will be discussed, and, thus, the degradation rate will be calculated based on Raman and FTIR microscope and 19F NMR. For longer ageing time, the ionomer degradation is extended to an non-defective area. A propagation mechanism of the degradation will be proposed.[1] L, Dubau, et al. WIREs Energy and Environ. 2014, 3, pp. 540-560.[2] S, Touhami, et al. J. Power Sources. 2021, 481, pp. 228908-228917. Figure 1

Improving vertical GaN p–n diode performance with room temperature defect mitigation

Defect mitigation of electronic devices is conventionally achieved using thermal annealing. To mobilize the defects, very high temperatures are necessary. Since thermal diffusion is random in nature, the process may take a prolonged period of time. In contrast, we demonstrate a room temperature annealing technique that takes only a few seconds. The fundamental mechanism is defect mobilization by atomic scale mechanical force originating from very high current density but low duty cycle electrical pulses. The high-energy electrons lose their momentum upon collision with the defects, yet the low duty cycle suppresses any heat accumulation to keep the temperature ambient. For a 7 × 105 A cm−2 pulsed current, we report an approximately 26% reduction in specific on-resistance, a 50% increase of the rectification ratio with a lower ideality factor, and reverse leakage current for as-fabricated vertical geometry GaN p–n diodes. We characterize the microscopic defect density of the devices before and after the room temperature processing to explain the improvement in the electrical characteristics. Raman analysis reveals an improvement in the crystallinity of the GaN layer and an approximately 40% relaxation of any post-fabrication residual strain compared to the as-received sample. Cross-sectional transmission electron microscopy (TEM) images and geometric phase analysis results of high-resolution TEM images further confirm the effectiveness of the proposed room temperature annealing technique to mitigate defects in the device. No detrimental effect, such as diffusion and/or segregation of elements, is observed as a result of applying a high-density pulsed current, as confirmed by energy dispersive x-ray spectroscopy mapping.

Fluorinated Artificial Solid-Electrolyte-Interphase Layer for Long-Life Sodium Metal Batteries.

Sodium metal batteries have garnered significant attention due to their high theoretical specific capacity, cost effectiveness, and abundant availability. However, the propensity for dendritic sodium formation, stemming from the highly reactive nature of the sodium metal surface, poses safety concerns, and the uncontrollable formation of the solid-electrolyte interphase (SEI) leads to large cell impedance and battery failures. In this study, we present a novel approach where we have successfully developed a stable fluorinated artificial SEI layer on the sodium metal surface by employing various weight percentages of tin fluoride in a dimethyl carbonate solution, utilizing a convenient, cost-effective, and single-step method. The resulting fluoride-rich protective layer effectively stabilized the Na metal surfaces and significantly enhanced cycling stability. The engineered artificial SEI layer demonstrated an enhanced lifetime of Na metal symmetric cells of over 3.5 times, over 700 h at the current density of 0.25 mA/cm2, in cycling performance compared to the untreated sodium, which is attributed to the suppression of dendrite formation and the reduction of undesired SEI formation during high-current cycling.

Effect of Zr4+ doping on the electrochemical properties of Na3MnTi(PO4)3/C cathode materials

Effect of Zr4+ doping on the electrochemical properties of Na3MnTi(PO4)3/C cathode materials

Modification of carbon felt electrode by MnO@C from metal-organic framework for vanadium flow battery

Modification of carbon felt electrode by MnO@C from metal-organic framework for vanadium flow battery

Robust Artificial Interlayer with High Ionic Conductivity and Mechanical Strength toward Long‐Life Na‐Metal Batteries

Sodium metal, benefiting from its high theoretical capacity and natural abundance, is regarded as a promising anode for sodium‐metal batteries (SMBs). Unfortunately, the uncontrollable sodium dendrites formation caused from the sluggish ion‐transport kinetics and fragile solid electrolyte interphase (SEI) interlayer induces a low Coulombic efficiency and poor cycling stability. Constructing an artificial SEI interlayer with high ionic conductivity, stability, and mechanical toughness is an effective strategy for Na‐metal anode, yet it still presents major challenge for high current density and long cycling life. Herein, an artificial SEI interlayer composed of Na–Sn alloy, Sn, and Na2Te (denoted as NST) is designed via in‐situ conversion/alloying reaction of tin telluride (SnTe) with Na. Such artificial interlayer possesses rapid Na+‐transport kinetics and high Young's modulus (5.3 GPa), benefitting to even Na plating/stripping and suppressing Na dendrite growth. Owing to these merits, the symmetrical Na/NST cell presents an ultralong cycle life span over 1390 h with a small voltage hysteresis at 1 mA cm−2 with 1 mAh cm−2. And the Na3V2(PO4)3 (NVP)||Na/NST full cell exhibits a prolonged life of 1000 cycles with a high‐capacity retention of 88% at 5C. Herein, a promising strategy is provided to construct a high‐performance artificial interlayer for SMBs.

Growth of mesoporous carbon supported (bimetallic) phosphides derived from Prussian blue for supercapacitors

In the context of supercapacitor energy storage, maintaining high cycle stability while enhancing energy density and coulomb efficiency is crucial. In this investigation, NiCo Prussian blue analogue (PBA) electrode materials were synthesized using the coprecipitation method, and subsequently modified via sulfurization and phosphating to obtain oxides (PBAO), sulfides (PBAS) and phosphides (PBAP) derived from Prussian blue cubes. The microphysical structure of PBA was engineered to enhance conductivity and electrochemical performance, with an in-depth exploration of the effects of sulfurization and phosphating. Additionally, mesoporous carbon (SAC) was doped into the previously prepared PBA, leading to the successful preparation of [email protected] electrode material with exceptional electrochemical performance. By utilizing electrochemical testing and various characterization techniques, the underlying sources of the observed performance differences were analyzed both experimentally and through electrochemical mechanisms. Furthermore, the addition of 0.01 M potassium ferricyanide to the 3 M KOH electrolyte significantly improved the coulomb efficiency of the material under the condition of high current density and long cycle time. Finally, an asymmetric supercapacitor (ASC) was constructed using industrial activated carbon as the negative electrode with the prepared [email protected] electrode material, and its electrochemical performance was evaluated to explore the practical application potential and prospects of this material.