Cathode Performance Research Articles

One Stone for Multiple Birds: Copolymer with Multifunctional Groups Boosts the Cycling Stability of Lithium Cobalt Oxide Cathodes at 4.5 V.

High-voltage LiCoO2 is a promising cathode material for ultrahigh-energy lithium-ion batteries, particularly in the commercialization of 5G technology. However, achieving long-term operational stability remains a significant challenge. Herein, a quaterpolymer additive with multiple functional groups is introduced to enhance the electrochemical performance of LiCoO2 cathode at 4.5 V. The capacity remains 96% after 100 cycles at room temperature and 94.4% after 50 cycles even at 45 °C. The sulfonate and ester groups of the quaterpolymer additive serve as lithium carriers, providing high voltage resistance and fast ionic conductivity with increased lithium-ion diffusion coefficients during the charge/discharge processes. The incorporation of a quaterpolymer additive also improves the dispersion properties and peel strength of the LiCoO2 cathodes. The coordination between the sulfonate groups and Li+ as well as the amine-based derivatives and Lewis acid of PF5 is expected to disrupt the Li+ solvation shell and deactivate the PF5 reactivity, therefore suppressing electrolyte decompositions. Furthermore, the superior interactions between sulfate ester (O atoms)/amide (N atoms) groups of copolymer additive and superficial cobalt atoms of LiCoO2 provide a compensating charge to Co, inhibiting the surface cobalt dissolution, irreversible oxygen redox reaction, and the detrimental LiCoO2 phase transition from O3 to H1-3. The use of a tiny amount of polymer additive presents an effective approach to stabilizing high-voltage LiCoO2, offering valuable insights for the design of high-energy battery materials.

Mitigating Crosstalk by Slurry Additive Toward 5V Cobalt-Free LiNi0.5Mn1.5O4 Cathode.

LiNi0.5Mn1.5O4 (LNMO), with its spinel symmetry, emerges as a promising cathode material for high-voltage lithium-ion batteries (LIBs). Nonetheless, the vulnerability of LNMO to interfacial degradation, particularly electrolyte breakdown during high-voltage operation, compromises its long-term cycling performance. To overcome this longstanding challenge, a slurry additive-polyester-urethane-acrylate (PEUA)-to form a multi-functional ultra-thin electrode coating, enhancing the lifespan and energy density of LIBs is introduced. Comprehensive characterizations and theoretical analyses reveal that the PEUA slurry additive effectively maintains electrode integrity, facilitates electrons and lithium ions transport, and inhibits hazardous side reactions, thus preventing the by-products from triggering cathode-electrolyte-anode interface crosstalk. Consequently, the 5V LNMO || Li cell with PEUA slurry additive maintains a high-capacity retention of 97.8%, with improved cycling stability at high-temperature and full-cell configurations. This crosstalk-mitigation strategy offers a promising avenue for extending the lifespan and electrochemical performance of high-voltage cobalt-free cathodes, advancing the practical use of high-energy density LIB technology.

Performance of the Liquid Cadmium Cathode Assembly for the Electrodeposition of U and Ce from LiCl-KCl Molten Salt

Abstract A mesh-type assembly and stirrer assembly were developed to improve the performance of liquid cadmium cathodes for the electrodeposition of U and Ce from LiCl-KCl molten salt at 773 K. The thermodynamic basis for electrodepositing U and Ce was established through the calculation of equilibrium potentials and cyclic voltammograms, while also examining the co-deposition of Li. Thereafter, U and Ce electrodeposition was performed by galvanostatic electrolysis, and the current efficiency was determined. It was found that both assemblies effectively hampered the growth of U dendrites and Ce-Cd dendritic alloys. However, the utilization of the mesh-type assembly resulted in a greater current efficiency for U, with the maximum deposited amount attaining 7.7 wt% U/Cd without causing U dendrites formation. In contrast, the current efficiency for Ce was enhanced after using the stirrer assembly due to an improved diffusion flux of Ce ions. Finally, cathode deposits were characterized by scanning electron microscopy, energy-dispersive spectroscopy, and X-ray diffraction, which revealed that disrupted fine U dendrites were randomly scattered in the Cd bulk, and that the CeCd11 dendritic alloys were also damaged, leading to an increased atomic ratio of Ce to Cd at the Cd bottom.

Enhanced performance of lithium-ion battery cathodes using a composite conductive network of CNTs, GQDs, and GNRs embedded in Li₁.₂Mn₀.₅₄Ni₀.₁₃Co₀.₁₃O₂ (LMNCO)

Lithium-rich Li-ion battery cathode materials are known for their high specific capacities and working potential. However, their practical application is limited by the significant decline in discharge potential and capacity during repeated cycling. In this study, we introduce a highly conductive electrode architecture, encapsulating within carbon nanotubes (CNTs), graphene nano-ribbons (GNRs) and graphene quantum dots (GQDs) to mitigate rapid capacity fading and suppress voltage decay. Three Li1.2Mn0.54Ni0.13Co0.13O2 cathode materials were synthesized. The first sample, pristine Li-rich L1.2Mn0.54Ni0.13Co0.13O2, was synthesized using a nitrate co-precipitation method. The second cathode, GNRs-CNTs@Li1.2Mn0.54Ni0.13Co0.13O2, incorporates a mixture of carbon nanotubes and graphene nanoribbons. The third cathode, GQDs:GNRs-CNTs@Li1.2Mn0.54Ni0.13Co0.13O2), further integrates graphene quantum dots within the graphene nanoribbons and carbon nanotubes matrix. The inclusion of highly conductive GNRs-CNTs and GQDs effectively enhances the electrical conductivity of L1.2Mn0.54Ni0.13Co0.13O2, increasing the specific capacity from 246.95 to 316.94 mAhg−1. Additionally, GQDs prevent side reactions and surface phase transitions, thereby improving thermal stability.

Synergistic Enhancement of Cathode Performance through the Introduction of Oxygen Vacancies in the P2/P3 Mixed Phase.

P2-type NaxNiyMn1-yO2 cathodes have attracted attention due to their excellent stability and low cost, making them promising for sodium-ion batteries. However, their practical application is limited by a low capacity at lower voltages and severe phase transitions at higher voltage. To address these challenges, we report a material Na0.6Ni0.3Mn0.7O2-OVs (NNMO-OVs) with significantly slowed phase transitions at high voltage by introducing oxygen vacancies OVs into the P2/P3 mixed phase cathode Na0.6Ni0.3Mn0.7O2 (NNMO). Such a modification effectively broadens the Na+ diffusion pathways and enhances anionic redox reactions (ARR). As a result, an improved capacity of 173 mAh·g-1 at 1C is obtained by the desirable cathode within a voltage range of 1.5-4.3 V. Even at 10C, it exhibits a capacity of 60.1 mAh·g-1 between 2 and 4.1 V, maintaining 70.1% capacity retention after 700 cycles, showcasing impressive rate performance and cycling stability. Additionally, the P2/P3 mixed phase exhibits the presence of an OP4 intermediate phase during charging to high voltages, while the introduction of oxygen vacancies (OVs) further suppresses the P-O phase transition, maintaining only the P2-OP4 phase transition process.

Effect of Carbon Morphology and Slurry Formulation in Sulfur Cathode for Li-S Batteries

The performance of Lithium-Sulfur (Li-S) batteries is significantly influenced by material selection and manufacturing processes, with conductive carbon and slurry formulation playing crucial roles. In this study, the impact of carbon morphology and solvent/solid ratio in slurry preparation on microstructure and electrochemical performance of sulfur cathodes was investigated. Various carbon structures, such as nanotubes, sheets, and particles, were explored, and the solvent volume was adjusted to assess their effects on electrode architecture and electrochemical performance. Our findings demonstrate that the binder dissolution process and consequent electrode architecture and performance are highly influenced by both the carbon structure and slurry solvent volume. Furthermore, it was observed that, contrary to common assumption, advanced carbon structures are not necessary for enhanced capacity and durability of Li-S cathodes. Accordingly, the best cycling durability was achieved by optimizing the slurry with 300 μL/mgPVDF of NMP solvent and using Ketjen black as the conductive carbon, resulting in an initial capacity of 1029 mAh gS −1, with a retention of 830 mAh gS −1 after 500 cycles. These results, obtained at a high areal loading of 4.5 mgS cm−2, demonstrate the commercial potential of the proposed electrode formulation and processing method without reliance on advanced materials or techniques.

Enhancing the electrochemical performance of Ni-rich cathode through an in-situ La-doping and La4NiLiO8-coating synergistic strategy

Ni-rich layered oxides offer numerous advantages such as high discharge capacity, cost-effectiveness, and environmental friendliness, making them the mainstream cathodes for high-energy density lithium-ion batteries. However, their widespread commercialization is hindered by critical challenges in cycling performance, stemming from unstable interface and structure, particularly at elevated charge cut-off voltages. Herein, a dual-modification strategy combining La doping and La4NiLiO8 coating was proposed to synergistically enhance the surface/interface and structure stability of the LiNi0.83Co0.11Mn0.06O2 (referred to as NCM83) cathode. Unlike conventional methods, a well-designed La(OH)3 coating pretreatment was employed on the Ni0.83Co0.11Mn0.06(OH)2 precursor. This pretreatment aimed to facilitate the in-situ formation of La doping and La4NiLiO8 during the lithiation of the coated precursor, while ensuring desired uniformity of the La4NiLiO8 coating and La doping. This dual-modification strategy integrated the advantages of both La doping and La4NiLiO8 coating, demonstrating excellent capability to improve the overall performance of NCM83. The La doping, acting as a pillar, not only strengthened the layered structure of the cathode to mitigate volume changes, but also enhanced Li+ diffusion by broadening the c axis spacing. The La4NiLiO8 coating efficiently protected the cathode from H2O/CO2 attack and electrolyte erosion, while also facilitating Li+ transport owing to its favorable Li-conductive properties. Such a dual-modification strategy significantly enhanced the electrochemical performance of NCM83, as demonstrated by the excellent long-term cyclic stability, rate capability, and thermal stability at a high charge cut-off voltage of 4.5 V. This work highlighted the benefits of integrating elemental doping and surface coating, while offering a promising synthetic protocol for straightforward and effective dual-modification of various cathodes.

Enhanced elevated-temperature performance of LiMn2O4 cathodes in lithium-ion batteries via a multifunctional electrolyte additive

LiMn2O4 is a promising cathode material for lithium-ion batteries (LIBs) due to its low cost, environmental friendliness, and high voltage operation. However, its electrochemical performance deteriorates at elevated temperatures, primarily by reason of the structural degradation during cycling and proliferation of adverse reactions at the electrode/electrolyte interface. One of the main reasons is that the hydrolysis and decomposition of the LiPF6 at high temperatures produces HF, which leads to corrosion at the electrode/electrolyte interface and accelerates manganese dissolution. In this work, we report a multifunctional silane-based electrolyte additive, trimethoxyphenylsilane (TMPS), to solve these problems. Theoretical calculations and experimental results both demonstrate that TMPS can eliminate HF, stabilize PF5, and inhibit LiPF6 hydrolysis, thereby mitigating transition metal leaching. Additionally, TMPS improves the stability between cathode and electrolyte by constructing a highly stable and homogeneous cathode-electrolyte interfacial. The LiMn2O4//Li cell using the electrolyte containing 1 wt% TMPS retains 95.5 % and 83.7 % of its capacity after 500 cycles at 25 °C and 60 °C, respectively. Moreover, 18650-type cylindrical cells with this electrolyte also exhibit enhanced electrochemical performance at elevated temperatures. It demonstrates that TMPS is a promising multifunctional additive for manganese-based cathodes in LIBs.

Synthesis, Structure, and Electrochemical Performance of Bi-induced Stabilization of MnO2 Cathodes for Use in Highly Acidic Aqueous Electrolytes (pH

MnO2 cathode materials are widely studied in alkaline and neutral aqueous electrolytes. In these mediums, the MnO2 cathode shows suboptimal performance limited by dissolution and electrochemically inactive compound formation, leading to capacity fading. This study explores the enhancement of MnO2 cathode performance through Bi3+ ion doping (0, 1, 2.5, 5, and 10mol%) in a highly acidic electrolyte (pH < 2). By incorporating up to 10mol% Bi ions into the MnO2 structure, we significantly improved specific capacity and capacity retention stability. Energy-dispersive X-ray spectroscopy (EDX) analysis revealed a uniform dispersion of Bi3+ ions throughout the MnO2 cathode after electrochemical cycling, contributing to performance enhancements. X-ray photoelectron spectroscopy (XPS) results indicated that Bi3+ ion concentration from 1 to 10mol% stabilises Mn3+ within the MnO2 lattice. Also, Bi3+ ion doping promotes the formation of a 2×2 tunnel structured α-MnO2 phase. Electrochemical impedance spectroscopy results demonstrated a reduction in double-layer and overall bulk capacitance. These findings suggest that Bi3+ ion doping effectively enhances MnO2 electrochemical performance and could enhance its use in aqueous metal-ion batteries.

Cost effective reduced graphene oxide/polyaniline composite coated SSM cathode for bio-electrochemical desalination: Advancing desalination via cathodic improvement

The microbial desalination cell (MDC) has emerged as a fascinating and green desalination process. However, cathode limitation restricts its practical implementation. An efficient catalyst layer for the cathode can improve such deficiencies significantly. The study, for the first time, investigated reduced graphene oxide (rGO) and polymerized aniline (PANI) composite catalysts to improve cathodic performance in MDC. Different rGO layers were achieved on stainless steel mesh (SSM) by varying rGO concentrations, followed by fixed PANI layer deposition. The XRD, FTIR and SEM analysis confirmed the successful formation of PANI on top of rGO on SSM with the nano-fibrous structure having rGO-characteristic XRD peak at 11.7° with OH, (-C=O), (-C-O), C = C groups. The effect of rGO was optimized by fine-tuning of rGO mass deposition on SSM. The cyclic voltammetry (CV) results have verified that PANI-rGO1.0-SSM (1 mg/mL rGO deposition) was electrochemically the best-performing composite with the highest CV current (2.1 mA). Therefore, three PANI-rGO1.0-SSM composite cathodes were prepared with 15, 30, and 45 deposition cycles to apply in MDC to study the desalination and bio-electrochemical performances. The 30-deposition cycle cathode showed the best improvement among desalination rates (i.e., 40.5 % higher) and internal resistance (i.e., 96 % low) compared to the controlled cathode. Cost estimation revealed that the electro-deposition is a low-cost coating method for PANI-rGO1.0 on SSM (US $6) and is advantageous compared to the platinum coating processes. Future research should optimize rGO and PANI loading rates and coating process to achieve better cathodic improvement for PANI-rGO composite.

Drastically Promoting Rate Capability via Dual-Cations Intercalation of V2O5 Enabling Rapid Zinc-Ion Storage.

Layered vanadium pentoxide (V2O5) has drawn enormous attention as cathode material for aqueous zinc-ion batteries (AZIBs). However, the fragile open-framework and the sluggish Zn2+ migration due to the strong electrostatic interaction between Zn2+ and cathode electrode hinder the development of AZIBs. Here, an effective dual-cations intercalation strategy is employed based on synergistic effect of Mn2+ and Zn2+, which introduces guest species with robust layered construction and weak electrostatic interaction in the V2O5 bulk. Consequently, the (Mn0.13Zn0.03)V2O5 (abbreviated to MZVO) electrode exhibits a high reversible capacity of 463mA h g-1 at 0.1 A g-1, a high cycling stability (94% of capacity retention after 1000 cycles at 10 A g-1) and superior rate performance of 256 mAh g-1 at 20 A g-1. The outstanding performance of MZVO cathode is attributed to the Mn2+-induced fast migration of Zn2+ transfer and Zn2+-induced high structural stability conducted by density functional theory (DFT) calculations. The two-phase reaction mechanism of MZVO during Zn2+ (de)interaction is systematically expounded via operando XRD. This study will provide reference for the design of modified layered metal oxides in the future.

Enhanced Cycling Performance of the LiNiO2 Cathode in Li-Ion Batteries Enabled by Nb-Based Surface Coating.

Lithium nickel oxide (LNO) is a promising cathode candidate in various next-generation battery technologies. To increase its stability, doping and surface coating have become key strategies. Among various elements, niobium stands out for its dual role as an effective dopant and the advantages of its oxide phases as coatings. In this study, we explore Nb-based coating of LNO, utilizing methods that minimize or eliminate solvent use. Additionally, the coated samples were treated at two different temperatures to study their effect on properties and electrochemical performance. Our results demonstrate that the coating process strongly affects the cell cyclability and further highlight the potential of Nb-based protective coatings in enhancing LNO as a cathode active material for application in high-energy-density Li-ion batteries.

Highly Stabilized Ni‐Rich Cathodes Enabled by Artificially Reversing Naturally‐Formed Interface

AbstractA significant obstacle in the manufacturing and practical application of Ni‐rich cathode materials is decreasing the manufacturing cost without sacrificing the cycling stability. Here a high‐energy, ultrahigh‐Ni, and nearly Co‐free cathode with outstanding cycling performance is proposed. This promising cathode is enabled by artificially constructing an “outside‐in” interface structure toward LiNi0.94Co0.05Mn0.01O2 (NCM94) cathodes. Combining theoretical prediction and experimental results, it is revealed that high interfacial stability is achieved by a specific surface chemistry with an outside‐in structure composed of an inner organic layer and an outer inorganic layer. Benefiting from the protection effect of the robust outside layer and the strain relieve function of the inside layer, the intrinsic challenges of interfacial reactions, transition metal (TM) dissolution, and micro‐crack propagation have been mitigated for the Ni‐rich cathode. As a result, the “outside‐in” strategy enables superior cycling stability with a 92.7% retention after 200 cycles and an excellent rate capability of 149.1 mAh g−1 at 10 C, achieved by adding only 0.5% of the production cost. This study unlocks the possibilities of achieving outstanding performance for ultrahigh Ni cathode by spending minimum cost through the facile surface chemistry method.

Electrochemical Oxidation of Biomass-Derived Wastewaters for Simultaneous H2 Production

As the world continues to search for new ways to support the growth of a sustainable energy future, biomass conversion emerges as a potential method to produce carbon-neutral biofuels and biochemicals. For example, hydrothermal liquefaction (HTL) can be used to convert biomass- and waste-derived feedstocks into bio-crudes, which then undergo catalytic upgrading with exogenous molecular hydrogen (H2) for biofuel production (gasoline, diesel, jet oil.). HTL also generates an aqueous phase (HTL-AP) that contains up to 5 wt.% of organic compounds that cannot be treated with traditional wastewater treatment technologies (e.g., anaerobic digestion). Instead, we propose to use the HTL-AP to in situ generate the H2 needed for biofuel production via the electrochemical oxidation (ECO) of HTL-AP.1 2 In this work, we evaluate how the HTL-AP composition of both organic and inorganic compounds as well as the applied potential affect the ECO activity, energy consumption, and electrode stability. Initially, our electrochemical experiments were performed in batch cells to understand the performance of anode and cathode for ECO and H2 generation in terms of onset potential, exchange current densities, and Tafel slopes. This was followed by a demonstration of ECO long-term stability in a continuous-flow electrolyzer. Our studies show that the presence of organic compounds decreases the current density at high potential region but increases at low potential region for some HTL-AP. The anode stability increased from 24 h to &gt;3,000 h by optimizing the applied potential and the source of HTL-AP. However, the cathode performance and stability remained unaffected by the HTL-AP and potential. The resulting energy requirement for COD removal (kWh/kgCOD) of the optimized system is lower than that of the traditional wastewater treatment process. Furthermore, the energy requirement for H2 production (kWh/kgH2) is found to be almost half compared to the commercial electrolyzer. References (1) Andrews, E.; Lopez-Ruiz, J. A.; Egbert, J. D.; Koh, K.; Sanyal, U.; Song, M.; Li, D.; Karkamkar, A. J.; Derewinski, M. A.; Holladay, J. Performance of base and noble metals for electrocatalytic hydrogenation of bio-oil-derived oxygenated compounds. ACS sustainable chemistry &amp; engineering 2020, 8 (11), 4407-4418. (2) Qiu, Y.; Lopez-Ruiz, J. A.; Zhu, G.; Engelhard, M. H.; Gutiérrez, O. Y.; Holladay, J. D. Electrocatalytic decarboxylation of carboxylic acids over RuO2 and Pt nanoparticles. Applied Catalysis B: Environmental 2022, 305, 121060. Figure 1

(Invited) Enhancing the Performance of Lithium-Ion Cathodes

Significant attention has recently been given to increasing the energy density of commercial LiNi1-x-yMnxCoyO2 (NMC) lithium-ion cathodes with an added constraint of greatly mitigating the use of cobalt. These two goals can be achieved in a seemingly straightforward manner by simply increasing Ni contents, and several Ni-rich compositions have found commercial success. Nonetheless, the increasing demand for lithium-ion batteries has brought about the realization that a more diverse portfolio, with respect to cathode materials, will be critical to ensure supply chain security, lower costs, and wide-spread adoption of energy storage technologies. More specifically, substantially increasing the use of earth-abundant materials is now viewed as a necessary path forward to ensure sustainability. Earth-abundant elements are attractive options in terms of sustainable technological development as they have the potential for positive impact with respect to increasing the availability of raw materials, ultimately lowering costs, and increasing accessibility of dependent technologies such as electric vehicles. Regardless of the class of cathode under consideration for a given application, a common theme among all lithium-ion cathode materials is their need for modification in order to meet the stringent demands of application. Of note, all cathode materials generally require surface stabilization to help enable acceptable performance in terms of metrics such as cycle-life and impedance. This is particularly true in the drive to develop solid-state batteries. In addition, small compositional changes in the way of bulk and surface dopants can also have a major impact on long-term performance. This presentation will discuss work ongoing at Argonne National Laboratory related to the modification of lithium-ion cathodes. Commercially relevant materials, as well as novel materials currently in development at Argonne, will be explored. Atomic layer deposition will be highlighted as a unique tool to not only enable enhanced battery cell performance, but also as an opportunity to discover new materials in the rapidly expanding market of lithium batteries.

Performance of ITER pressure gauges during deuterium operation in the large helical device

Abstract During deuterium campaigns on the heliotron large helical device (LHD), ITER pressure gauges with different cathode materials were used to measure the neutral pressure in the sub-divertor region. Throughout these campaigns, it was observed that the performance of the LaB6 cathodes was unsatisfactory, credited to the generation of neutrons impacting the gauges. Conversely, measurements taken with pressure gauges with a ZrC cathode performed well throughout the deuterium pulses. The ITER pressure gauge with the ZrC cathode could be operated with a very high electron current of 800 µA, thus improving the lower detection limit of the neutral pressure in LHD. With this design it was also possible to avoid jumps in the ion current within strong magnetic fields, improving the accuracy of the measurement from 15% uncertainty to 5%. These features allowed very precise neutral pressure measurements to be made in a fusion device with magnetic confinement. The total running time in the magnetic field was around 60 hours, less than the cathode life time of 350 hours.

Surface oxygen vacancy regulation strategy enhances the electrochemical catalytic activity of CoFe2O4 cathode for solid oxide fuel cells

Oxygen vacancies are crucial for enhancing oxygen ion transport in solid-state materials. Therefore, an approach was established to efficiently adjust the surface oxygen vacancy concentration in the solid oxide fuel cell (SOFC) cathodes. This method employs NaBH4 solution to capture lattice oxygen on the cathode surface, enabling precise control over both the surface oxygen vacancy concentration and the transition metal ion valence states in spinel CoFe2O4 (CFO) by modulating the NaBH4 treatment duration. The results indicate that CFO-10, treated with NaBH4 solution for 10 min, exhibits optimal electrochemical catalytic activity. This enhancement is primarily attributed to the improved oxygen adsorption-dissociation and charge transfer processes. At 750 °C, CFO-10 shows a polarization resistance (Rp) of 0.032Ω cm2, representing a reduction of 42.8 % compared to CFO. Additionally, CFO-10 achieves a peak power density (PPD) of 923 mW·cm−2, representing a 78.5 % increase compared to CFO. This study provides new insights for optimizing SOFC spinel oxide cathode performance and opens a promising avenue for the development of other high-performance catalytic materials.

The effect of Mo and Sc dopants on the performance of an Sr2Fe2O6 cathode for use in proton-conducting solid oxide fuel cells

Sr2Fe2O6 was doped with Sc and Mo ions to investigate the effect of these dopants on the material properties and cathode performance. Both Sc and Mo were doped into Sr2Fe2O6 as pure phases, and the thermal expansion coefficient (TEC) increased with the Sc content of the material. A first-principles calculation at the atomic level indicated that Mo facilitated hydration, whereas Sc doping facilitated the formation of oxygen vacancies. Simulation results showed that the lowest energy barrier to O2 adsorption and dissociation was obtained by co-doping Sc and Mo into Sr2Fe2O6, facilitating the cathode reaction. The results of fuel cell tests indicated that co-doping with Sc and Mo resulted in higher fuel-cell performance for Sr2Fe2O6 than doping with Sc or Mo alone. An impedance analysis for Sr2Fe2O6 co-doped with Sc and Mo indicated a good balance between hydration and oxygen vacancy formation, as well as a low energy barrier to O2 adsorption and dissociation, which resulted in this material exhibiting the lowest polarization resistance among the tested cathodes. This study demonstrates that each dopant has unique advantages and disadvantages in terms of cathode properties, and it is necessary to strike a balance among the parameters involved to enhance the cathode performance.

Manganese‐Based Composite‐Structure Cathode Materials for Sustainable Batteries

AbstractManganese‐based cathode materials have garnered extensive interest because of their high capacity, superior energy density, and tunable crystal structures. Despite their cost‐effectiveness, challenges like Mn dissolution and gas evolution originating from the irreversible structural degradation pose risks to stability and prolonged electrochemical behaviors, ultimately constraining their practical applications and market prospects. While the material characteristics and redox mechanisms of Mn‐based cathodes are extensively investigated, a systematic iterative approach to material design that balances performance and application demands remains both necessary and urgent. Recent strategies for enhancing cathode performances emphasize the innovative introduction and customization of composite structures in Mn‐based cathode materials to address the challenges above. This review aims to provide a comprehensive understanding of composite‐structure construction methodologies and offers practical guidelines for effectively designing high‐stability Mn‐based composite‐structure cathode materials. This encompasses the classifications of composite scales, the discussions for the extent of composite‐structure construction inside and outside of the cathode grains, and an exploration of the development potential of these materials, especially for grid‐scale applications.

Entropy and Electronic Structure Modulation of a Prussian Blue Analogue Cathode with Suppressed Phase Evolution for Potassium-Ion Batteries.

Severe structural evolution and high content of [Fe(CN)6]4- defects drastically deteriorate K-ion storage performances of Prussian blue-based cathodes. Herein, a potassium manganese iron copper hexacyanoferrate (KFe2/3Mn1/6Cu1/6HCF), with suppressed anionic vacancies, eliminated band gap, and low K-ion diffusion barrier, is regarded as a cathode for potassium-ion batteries. The entropy stabilization effect and robust Cu-N bond induced by the inert Cu-ion with large electronegativity boost KFe2/3Mn1/6Cu1/6HCF to exhibit great phase state stability, thus inhibiting the structural transition of monoclinic ↔ cubic. Hence, KFe2/3Mn1/6Cu1/6HCF undergoes a zero-stress solid-solution reaction mechanism, where Fe and Mn serve as dual active sites for charge compensation. Consequently, KFe2/3Mn1/6Cu1/6HCF displays a high reversible capacity of 127.5 mAh·g-1 with an energy density of 469.2 Wh·kg-1 at 10 mA·g-1 and superior cyclic stability with a high retention of 90.7% over 100 cycles. A high-energy-density K-ion full battery is assembled, contributing an ultralong lifetime over 1000 cycles with a low-capacity fading rate of 0.038% per cycle.