Cathode Design Research Articles

Development and standalone testing of the Air-breathing Microwave Plasma CAThode (AMPCAT)

Air-breathing electric propulsion (ABEP) refers to a spacecraft in very-low Earth orbit (VLEO) harnessing upper atmospheric air as propellant for an electric thruster. This allows the orbital altitude to be maintained via drag-compensation, removing the need for on-board propellant storage and allowing a mission lifetime which is not limited by propellant capacity. A cathode (or neutraliser) is required for the high-specific impulse electrostatic thruster designs proposed for an ABEP application. One such study is the AETHER EU H2020 project, which aims to design an ABEP system that can be tested on-ground in a VLEO-representative environment. There is therefore a need to develop a cathode for ABEP as conventional thermionic hollow cathodes are susceptible to oxygen poisoning. The Air-breathing Microwave Plasma CAThode (AMPCAT) presented here is based on a plasma electron source, using a 2.45 GHz microwave antenna directly-inserted into the plasma volume to ionise neutral air particles. This study details the cathode design and the results of iterative standalone testing, with a particular focus on: (a) the identification of a dual-mode current emission, with transition from lower- to higher-current mode with air at bias values around 70 V between the extracting anode and internal cathode surfaces, (b) a comparison of performance relative to xenon, for which the peak extracted current is 30–40% higher than air at equivalent inputs, and (c) the effect of antenna electrical isolation, using alumina shielding thicknesses in the 0.1–0.7 mm range. Standalone cathode tests demonstrate 0.8 A of stable extracted current with 0.1 mg/s mass flow rate of a 0.48O2 + 0.52N2 mixture, relative bias of 80 V and input microwave power of 70 W. To the authors’ knowledge, the demonstration of an extracted current in the 1 A order using air, without visible material degradation after several hours of operation, is a novel development in the cathode literature.

Sulfur-Assisted Surface Modification of Lithium-Rich Manganese-Based Oxide toward High Anionic Redox Reversibility.

Energy storage via anionic redox provides extra capacity for lithium-rich manganese-based oxide cathodes at high voltage but causes gradual structural collapse and irreversible capacity loss with generation of On - (0 ≤ n < 2) species upon deep oxidation. Herein, the stability and reversibility of anionic redox reactions are enhanced by a simple sulfur-assisted surface modification method, which not only modulates the material's energy band allowing feasible electron release from both bonding and antibonding bands, but also traps the escaping On - via an as-constructed SnS2- x - σ Oy coating layer and return them to the host lattice upon discharge. The regulation of anionic redox inhibits the irreversible structural transformation and parasitic reactions, maintaining the specific capacity retention of as-modified cathode up to 94% after 200 cycles at 100mA g-1 , along with outstanding voltage stability. The reported strategy incorporating energy band modulation and oxygen trapping is promising for the design and advancement of other cathodes storing energy through anion redox.

Effect of ammonium fluoride concentration on synthesis of Co3O4/CC as cathode material for zinc cobalt battery applications

Aqueous zinc ion batteries (AZIBs) have received great attention due to their simple manufacturing technology, high energy density, intrinsic safety and economic feasibility. Co3O4 is one of the ideal cathode materials for aqueous zinc-ion batteries, but many studies were concentrated on the synthesis, design and doping of cathodes. The effect of process parameters on morphology and performance were rare reported. In this paper, Co3O4/CC cathode material based on carbon cloth was prepared by different reactant concentration. The reactant concentration ratio were 2:1, 4:1, 6:1 and 8:1, respectively. The battery was possessed better performance that was assembled by Co3O4/CC material synthesized reactant concentration of 2:1. Co3O4/CC nanowire was uniform distribution, regular surface and small size on carbon cloth. The Zn-ion battery had excellent rate performance and low reaction resistance. The average discharge specific capacity is 142.6 mAh/g and capacity retention rates of 87.8% after 60 charge discharge cycles. The discharge specific capacity and capacity retention rate are significantly higher than the other three Co3O4/CC materials and the charge transfer resistance of the material is the smallest. The study optimized applicable reactant concentration of fabrication cathode Co3O4 in zinc-ion batteries.

An in-situ structural self-optimization strategy toward Ca1-xV3O7 cathode for aqueous zinc-ion batteries with ultra-high capacity and lifespan

Exploring excellent electrode material with high structural stability and rapid ions dynamics is the key challenge for achieving high capacity and long-term cycling stability aqueous zinc-ion batteries (AZIBs). Herein, we design a layered Ca1-xV3O7 cathode via an electrochemical in-situ structural self-optimization method. Removing a large amount of calcium ions from the parent phase structure not only provides effective space for the storage of zinc ions, but also significantly improves the ions transfer dynamics. At the same time, the residual Ca ions acts as ‘pillar’ to stabilize the layered structure and effectively avoid the structural collapse phenomenon of the layered vanadium oxide cathode during cycling. As a result, the self-optimized Ca1-xV3O7 (x = 0.84) cathode exhibits a high reversible capacity of 512 mA h g−1 at 0.1 A/g and impressing long lifespan in different current density condition. Furtherly, with the aid of the in-situ characterization technology, the reversible zinc ions storage mechanism of the Ca1-xV3O7 is revealed in detail. More importantly, by adjusting the x value of Ca1-xV3O7, we provide a new microcosmic perspective on the Ca2+- Zn2+ buffering mechanism in the host of Ca1-xV3O7 by DFT calculations and experimental evidence, which provides a guideline for rational design of the high-performance layered vanadium oxide cathodes for ZIBs.

Effects of structural parameters of double-layer electrode on co-electrolysis in a solid oxide electrolysis cell

The advantages of double-layer electrode are available in the literature about single electrolysis of H2O and CO2 using solid oxide electrolysis cell (SOEC). However, for the co-electrolysis of CO2 and H2O, the influence of the structural parameters of the double-layer electrode on the co-electrolysis performance has been still unclear. In this study, a multi-scale model describing the co-electrolysis process of CO2 and H2O in SOEC is adopted. After model validation, a comparison of the performance of SOEC between a single-layer cathode and a double-layer cathode is conducted with different inlet flow rates. Moreover, parametric analyses are performed to investigate the effects of the thickness and porosity of cathode diffusion layer (CDL) and the internal composition of cathode function layer (CFL). The results show that when the CDL porosity increases from 0.45 to 0.65, the conversion ratio of H2 and CO increase by 10.17 % and 10.24 %, respectively. The optimal thickness of CDL (200 μm) for enhancing the durability of the cell and the preferable internal composition of CFL for improving the co-electrolysis performance are found within the scope of this study. This numerical analysis can provide guidance for the design of the double-layer cathode and the optimization of the co-electrolysis performance.

Unlocking the Potential of Dual-Ion Batteries: Identifying Polycyclic Aromatic Hydrocarbon Cathodes and Intercalating Salt Combinations through Machine Learning.

Dual-ion batteries (DIBs) represent a promising energy storage technology, offering a cost-effective safe solution with impressive electrochemical performance. The large combinatorial configuration space of the electrode-electrolyte leads to design challenges. We present a machine learning (ML) approach for accurately predicting the voltage and volume changes of polycyclic aromatic hydrocarbon (PAH) cathodes upon intercalation with a variety of DIB salts following different mechanisms. Gradient Boosting and XGBoost Regression models trained on the data set demonstrate exceptional performance in voltage and volume change prediction, respectively. The models are further cross-validated and utilized to predict the properties for ∼700 combinations of PAH and DIB salt intercalations, a subset of which is further validated by density functional theory. Using average voltage and volume change for all combinations of PAHs and salts, preferable combinations for high/low voltage requirements along with long-term stability are obtained. Overall, the study shows the applicability of PAHs in DIBs exhibiting good electrochemical performance with low volume change compared to graphite indicative of its potential to overcome the cycling stability issues of DIBs. This research establishes a reliable and broadly applicable ML-based workflow for efficient screening and accelerated design of advanced PAH cathodes and salts, thus driving progress in the field of DIBs.

Ultrathin ZnO coating layer to boost the electrochemical reaction kinetics of MnO cathode for advanced aqueous zinc-ion batteries

Although conventional carbon-based materials and metallic oxide coating on manganese oxides (MnO) cathodes have been extensively researched, there are still some issues, including low electron conductivity, sluggish ions diffusion kinetics and inferior cycling stability, that need to be addressed through material modification. In this work, a simple atomic layer deposition strategy is proposed to fabricate ZnO-coated MnO (MnO@ZnO) as cathode for aqueous zinc-ion batteries. Benefiting from the heterogenous interface between ZnO and MnO, a strong built-in electric fields generated, which accelerates the electron transport and promotes a fast reaction kinetics. Additionally, the ZnO coating layer effectively alleviate the dissolution of MnO and also boost its electrical conductivity. In contrast to the pristine MnO, MnO@ZnO exhibits enhanced specific capacity of 350 mA h g−1 at 0.1 A g−1 and excellent longterm stability. In addition, the reaction mechanism is further comprehensively verified through various ex-situ characterization analyses. This work offers a simple coating method to boost electrochemical energy storage of MnO, which is of great significance for the design of cathodes with excellent performance.

Unraveling the Coupling Effect between Cathode and Anode toward Practical Lithium-Sulfur Batteries.

The localized reaction heterogeneity of the sulfur cathode and the uneven Li deposition on the Li anode are intractable issues for lithium-sulfur (Li-S) batteries under practical operation. Despite impressive progress in separately optimizing the sulfur cathode or Li anode, a comprehensive understanding of the highly coupled relationship between the cathode and anode is still lacking. In this work, inspired by the Butler-Volmer equation, a binary descriptor (IBD ) assisting the rational structural design of sulfur cathode by simultaneously considering the mass-transport index (Imass ) and the charge-transfer index (Icharge ) is identified, and subsequently the relationship between IBD and the morphological evolution of Li anode is established. Guided by the IBD , a scalable electrode providing interpenetrated flow channels for efficient mass/charge transfer, full utilization of active sulfur, and mechanically elastic support for aggressive electrochemical reactions under practical conditions is reported. These characteristics induce a homogenous distribution of local current densities and reduced reaction heterogeneity on both sides of the cathode and anode. Impressive energy density of 318Wh kg-1 and 473Wh L-1 in an Ah-level pouch cell can be achieved by the design concept. This work offers a promising paradigm for unlocking the interaction between cathode and anode and designing high-energy practical Li-S batteries.

Optimized anode, cathode and coolant flow designs for enhanced performance of proton exchange membrane fuel cells

This study deals with various flow field designs for anode, cathode and coolant plates for optimizing the performance of proton exchange membrane fuel cell using H2 and air. In particular, the 3D models with various flow field patterns such as single parallel serpentine (anode), multi parallel (anode), multi-parallel serpentine (cathode), multi serpentine (cathode) have been evaluated for enhancing the fuel cell performance at 60 °C, with three different coolant flow designs (mirror serpentine, multi serpentine and parallel serpentine). Both the peak power and limiting current density are considered based on the parameters such as temperature distribution, pressure distribution, reactants/species distribution and the membrane water content on the active area (50 cm2) region. It is interesting to note that the coolant channel also has a significant effect in regulating the fuel cell performance at high current densities, in addition to reactant gas flow channels. The simulated single cell with Nafion (thickness: 18 μm) demonstrates a peak power density of 0.97 W cm−2 with single parallel serpentine (anode), multi parallel serpentine (cathode) and serpentine (coolant) and 0.91 W cm−2 with multi parallel (anode), multi serpentine (cathode), and parallel serpentine (coolant) flow field designs. The simulated fuel cell performance is also experimentally validated at 60 °C using H2 fuel and air as the oxidant.

Bifunctional metallic composite catalyst cathode in heterogeneous electro-Fenton process: Classification, preparation and reactive species

The application of conventional electro-Fenton (EF) is limited by the narrow pH range and iron-containing sludge production, while the bifunctional cathodes in the heterogeneous electro-Fenton (HEF) can realize the synchronous generation and activation of H2O2, broaden the adaptable pH range and render catalyst easy to recycle, which has gained wide attention in electrochemical advanced oxidation processes (EAOPs). In this review, we summarized the classification of bifunctional metallic composite cathodes in HEF, the preparation and loading methods of catalyst on the cathode, as well as the advantages and the corresponding characterization of the bifunctional cathodes. The approaches to enhance the catalysts performance for H2O2 generation and activation and electrode stability were addressed. The origin, identification and transformation of reactive species in degradation mechanism were explored. Finally, the challenge and trend of bifunctional cathode for HEF was prospected. We hope this review can provide a useful guideline for the design and application of bifunctional cathodes in HEF.

Design of a perovskite oxide cathode for a protonic ceramic fuel cell

High catalytic activity, low-cost and stable cathode in a temperature range 550–700 °C is essential for the development of protonic ceramic fuel cells (PCFCs). Doping nickel into perovskite La0.5Sr0.5MnO3-δ(LSM) is designed as a cobalt-free cathode based on theoretical calculations and experiments. La0.5Sr0.5Mn0.9Ni0.1O3-δ (LSMNi) as cathode shows higher proton conductivity and ORR activity than the undoped LSM. The PCFCs with LSMNi exhibit low polarization resistance and high peak power density 1.1 W cm−2 at 700 °C. The density functional theory simulations indicate that doping with nickel decreases the oxygen vacancy formation energy and promotes the formation of hydroxide defects. The decrease in proton transfer energy barriers and hydration energy improves the proton conductivity. The improved performance is attributed to fast proton transfer and rapid kinetics of oxygen reduction on the surface of LSMNi. This work provides a novel approach to design cobalt-free cathode for a protonic ceramic fuel cell.

Entropy engineering design of high-performing lithiated oxide cathodes for proton-conducting solid oxide fuel cells

Entropy engineering design of high-performing lithiated oxide cathodes for proton-conducting solid oxide fuel cells

A Study on dFMEA-based Fire Risk Assessment of Lithium-ion Secondary Battery Testing Cells

In this study, Design Failure Mode and Effects Analysis (dFMEA) was performed to evaluate the fire risk of lithium-ion secondary battery testing cells used during the research and development stage. dFMEA was used for the failure risk analysis, risk assessment, and risk priority analysis of the anode, cathode, separator, electrolyte, and cell design of the testing cell. In addition, the evaluation criteria, including severity, occurrence, and detection, was reorganized into three categories and optimized for the testing cell application. Based on the failure risk analysis, a total of 11 causes of failure were identified. In particular, explosion and thermal runaway were predicted when a nickel-cobalt-manganese (NCM)-based anode material with a high nickel content was used, the separator had a high thermal contraction rate and low tensile strength characteristics, and there were errors in the electrolyte composition optimization. This cause of failure was classified as a moderate risk with a high fire risk by the risk priority analysis. Therefore, at the research and development stage, it is critical to evaluate the mutual reactivity and preliminary physical properties of battery materials and to construct safety equipment to reduce fire damage.

Fe-single-atom catalyst nanocages linked by bacterial cellulose-derived carbon nanofiber aerogel for Li-S batteries

Li-S battery (LSB) is promising for achieving high capacity. Still, its development is hindered by the complex redox process with sluggish kinetics and particularly the resulting lithium polysulfides (LiPS) shuttle effects. Single-atom catalysts (SACs), with their maximized atom utilization, could effectively chemisorb soluble LiPSs and expedite the sulfide conversion reaction kinetics. Here we report incorporating Fe single metal atom catalyst (Fe-SAC) in the sulfur cathode design and its electrocatalytic effects. Fe-doped ZIF-8 nanocages were introduced into a cheap biomass bacteria cellulose. A pyrolysis process converted them into an aerogel structure with Fe-SAC-functionalized N-doped carbon nanocages linked by a carbon nanofiber network (FeSA-NC@CBC), which was applied as a scaffold to fabricate freestanding and binder-free sulfur cathodes. We conducted electrochemical measurements to reveal Fe-SAC functions including lowering energy barriers for S8 reduction to liquid-phase LiPSs and further to solid-phase Li2S2/Li2S and accelerating Li2S2/Li2S nucleation and deposition, as corroborated by our theoretical calculation results. Benefiting from the synergistic effects of highly active Fe-SAC and three-dimensional conductive network, the sulfide reaction kinetics is improved, which can diminish LiPS shuttle effects and therefore improve LBS rate performance and cycling stability. Accordingly, the fabricated FeSA-NC@CBC composite cathode delivers an excellent rate capability at 2C with a reversible capacity of 840 mAh/g and a long-term cyclic stability of 800 mAh/g at 1C after 500 cycles.

Investigating the impact of variable aspect ratio cathode flow field on temperature distribution and performance in a PEM fuel cell

This study numerically investigates the effect of variable aspect ratio serpentine cathode flow field on proton exchange membrane fuel cell (PEMFC) performance and temperature distribution. By varying the proportion of two aspect ratios, 0.6 and 1, three modified cathode (MC) designs MC-1, MC-2, and MC-3, alongside a conventional cathode (CC) is considered. With 0.45 W cm−2, MC-2 exhibited 15.39% higher performance and 10.16 K lower temperature than CC. The transition region position, equal number of narrow and wider channels enhanced the current and temperature uniformity in MC-2. Furthermore, experimental results are consistent with the numerical results obtained from MC-2.

Interfacial Engineering of Ru Nanocluster-Modified TiO2 Nanotube-Assisted Regulation of Lithium Polysulfide Reactions.

The inhibition of lithium polysulfide (LiPS) diffusion and the acceleration of reaction kinetics are two major challenges for the practical application of lithium-sulfur (Li-S) batteries. Herein, through an interface engineering strategy, a multifunctional sulfur host based on Ru nanocluster-modified TiO2 nanotubes (TiO2-Ru) was designed. The TiO2-Ru interface field effect, combined with the hollow nanotube structure and the strong chemical action of TiO2, enhanced the LiPS trapping ability and inhibited the "shuttle effect". Furthermore, the high catalytic activity of Ru nanoclusters reduced the energy barrier of multistep LiPS reactions, thus speeding up the electrode kinetics. As a result, the TiO2-Ru-based composite sulfur cathode delivered excellent electrochemical performance, including an extremely low capacity loss of ∼0.015% per cycle and an increased areal capacity of ∼6.1 mAh cm-2 at 4.8 mg cm-2. This work contributes to a better sulfur cathode design from insights into morphology and phase interface engineering.

The engineering strategy in fabrication and application of high-specific-energy cathode for thermal battery

Nickel chloride is a promising material as cathode candidate for thermal battery, attributed to its superior electrochemical performance including high operating voltage and high specific energy. However, high polarization and structural collapse have emerged as major challenge hindering the practical application of NiCl2 cathode. Herein we propose an engineering strategy to construct a high-specific-energy NiCl2-based cathode with rhombohedral structure and amorphous carbon-layer skin structure. Benefited from delicate structural characteristic and improved electrochemical activity, the cathode designed remarkably elevates the plateau voltage of a single cell to 2.5 V and achieves, for the first time, a specific energy of 266.5 Wh/kg at current density of 600 mA/cm2 in the thermal battery tests. Notably, in contrast to the lab-level methods, this engineering strategy is an industrially feasible approach to manufacture NiCl2-based cathode for expanded application in thermal battery. This strategy also provides new insight into the design of high-performance cathode.

Revisiting the Role of Discharge Products in Li-CO2 Batteries.

Rechargeable lithium-carbon dioxide (Li-CO2 ) batteries are promising devices for CO2 recycling and energy storage. However, thermodynamically stable and electrically insulating discharge products (DPs) (e.g., Li2 CO3 ) deposited at cathodes require rigorous conditions for completed decomposition, resulting in large recharge polarization and poor battery reversibility. Although progresses have been achieved in cathode design and electrolyte optimization, the significance of DPs is generally underestimated. Therefore, it is necessary to revisit the role of DPs in Li-CO2 batteries to boost overall battery performance. Here, we report for the first time, a critical and systematic review of DPs in Li-CO2 batteries. We appraise fundamentals of reactions for formation and decomposition of DPs and demonstrate impacts on battery performance including, overpotential, capacity and stability, and highlight the necessity of discharge product management. We assess practical in-situ/operando technologies to characterize reaction intermediates and the corresponding DPs for mechanism investigation. Additionally, achievable control measures to boost the decomposition of DPs are evidenced to provide battery design principles and improve the battery performance. Findings from this work will deepen the understanding of electrochemistry of Li-CO2 batteries and promote practical applications. This article is protected by copyright. All rights reserved.

Azacyclic Anchor-Enabled Cohesive Graphite Electrodes for Sustainable Anion Storage.

Advanced energy-storage devices are indispensable for expanding electric mobility applications. While anion intercalation-type redox chemistry in graphite cathodes has opened the path to high-energy-density batteries, surpassing the limited energy density of conventional lithium-ion batteries , a significant challenge remains: the large volume expansion of graphite upon anion intercalation. In this study,a novel polymeric binder and cohesive graphite cathode design for dual-ion batteries (DIBs) is presented, which exhibits remarkable stability even under high voltage conditions (>5V). The innovative binder incorporates an acrylate moiety ensuring superior oxidative stability and self-healing features, along with an azide moiety, which allows for azacyclic covalent bonding with graphite and interchain crosslinking. A simple 1-h ultraviolet treatment is sufficient for binder fixation within the electrode, leading to the covalent bond formation with graphite and the creation of a robust three-dimensional network. This modification facilitates deeper and more reversible anion intercalation, leading to improved capacity, extended lifespan, and sustainable anion storage.Thebinder design, exhibiting exceptional adhesive properties and effective stress mitigation, enables the construction of ultrathick graphite cathodes. These findings provide valuable insights for the development of advanced binders, paving the way for high-performance DIBs.

Improving damage resistance of solid-state battery cathodes with block copolymers: A non-linear diffusion-mechanics study at the microscale

Minimizing interfacial failure in the composite cathode remains a crucial challenge to unravel the full potential of all solid-state batteries (ASSBs). Polymer-based ASSBs offer promising means of minimizing those damage effects due to their high ductility. However, multicomponent polymers such as block copolymers (BCPs) are needed to meet requirements for both ionic conductivity and mechanical resistance. This study aims to provide a new insight into the combined effects of block copolymer composition (soft-to-hard phase ratio) and interfacial strength on the coupled diffusion-mechanics response of an ASSB cathode, achieved by proposing a non-linear computational micromechanics approach. The approach combines a pressure-dependent diffusion process, interfacial gap-dependent diffusivity, and advanced elasto-viscoplastic constitutive model for a BCP, and it is implemented numerically within a non-linear finite element framework. Two cathode design concepts are explored here, with and without the BCP coating. Results from these case studies suggest that there is a strong interplay between the interface strength (between active particles and the BCP matrix), the BCP material composition, and the interfacial diffusivity. It is found that interfacial damage can be minimized by increasing both the interfacial strength and the amount of the soft component in the BCP system. If the diffusivity across the interface is damage-dependent, the latter is reduced when the BCP is predominantly made of the hard phase. Ultimately, a simple sensitivity analysis reveals that interfacial strength plays a vital role in minimizing interfacial damage, while the coating thickness is the least influential design parameter.