Cathode Performance Research Articles

Physical Mechanisms of Improved Performance of Scaffolded Zinc-Silver Battery Cathodes.

Nanostructuring can greatly improve the electrode stability of rechargeable battery systems, such as Zn-Ag. In this report, we investigate the physical mechanisms by which nanostructuring alters structural properties of nanomaterials and thereby influences the structural stability of electrodes. We specifically consider the effects of Au-based nanoscaffolds on Ag. Through density functional theory calculations, we propose that the charge transfer at the Au-Ag interface can facilitate the formation of Ag2O from Ag centers. Structural analysis of samples prepared in this work shows that Ag2O is extruded from Au-Ag material in the form of sheets. Interestingly, the length scale of such protrusions depends on the Au mole fraction that significantly alters the system's overall structural morphology. We rationalize these findings via kinetic Monte Carlo simulations of the Ag2O growth process and highlight the role of Au as a heterogeneous nucleation center.

Study on Attenuation Mechanism and Durability Improvement of Platinum-Carbon Catalysts for Proton Exchange Membrane Fuel Cells

The relationship between Pt particle size and activity and durability of Pt/C electrocatalysts on rotating disk electrodes is established and the results show that Pt/C electrocatalysts with particle size over 3.5 nm have excellent resistance to Pt particle decay and carbon corrosion. Further, the research results on the mechanism of Pt particle decay and carbon corrosion show that the Pt particle attenuation is composed of 80% Ostwald ripening and 20% particle agglomeration, and the carbon corrosion is affected by the catalytic action of Pt particles. Therefore, the above results show that regulating the Pt particle size to 3.5–4.0 nm can improve the durability of Pt/C electrocatalysts on RDE. To verify the accuracy of this conclusion and determine the optimal particle size range in practical application, single cells with 5 × 5 cm2 is assembled to evaluate the performance and durability of cathode Pt/C electrocatalysts under H2/air. The results show that cathode Pt/C electrocatalysts with particle size between 3.5 nm and 3.8 nm have high single cell performance (2.3 A cm−2@0.65 V) and durability (A loss of 15 mV@0.8 A cm−2 after 30000 cycles). These findings reveal the attenuation mechanism of Pt/C electrocatalysts and provide ideas for the development of high-durability Pt-based electrocatalysts for practical applications.

Tailoring SrFeO3 cathode with Ta and F allows high performance for proton-conducting solid oxide fuel cells

To customize the traditional SrFeO3 (SFeO) cathode for proton-conducting solid oxide fuel cells (H-SOFCs), a Ta cation and F anion co-doping approach is suggested. It has been discovered that Ta-doping can enhance the oxygen vacancy content and the protons' and oxygen's diffusion capacities, enabling improved H-SOFC performance. Ta-doping alone, however, only modestly enhances the cathode's performance, which is still below that of many newly created cathodes. The F anion co-doping is further introduced to further improve performance, resulting in the formation of the SrFe0.9Ta0.1O2.9F0.1 (SFeTOF) cathode. When SFeTOF is compared to the single Ta-doping material, its proton and oxygen diffusion properties are further improved, demonstrating the efficacy of using Ta and F co-doping for SFeO. Consequently, the fuel cell utilizing the SFeTOF cathode for H-SOFCs displays a fuel cell output of 1559 mW cm−2 at 700 °C, notably higher than the fuel cell that uses SFeO or Ta-doped SFeO cathodes. The performance is likewise impressive among the H-SOFC cathodes that are now in use. Moreover, the fuel cell utilizing the SFeTOF cathode demonstrates sufficient operational stability in operating conditions, establishing SFeTOF as a reliable and effective cathode for H-SOFCs.

Designing high-performance phosphate cathode toward Ah-level Na-ion batteries

The phosphate material Na3V2(PO4)3 is one of promising cathodes for Na-ion batteries owing to its superior electrochemical reversibility. However, the high-potential V4+/V5+ redox couple (4.0 V vs. Na+/Na) in pure Na3V2(PO4)3 cathode is not activated, resulting in a limited energy density. Although conventional single-metallic substitutions can activate V4+/V5+ redox plateau, the energy density has no significant improvement due to the limited capacity of V4+/V5+ redox plateau. Here, we propose a bi-metallic (Al3+ and Fe3+) substitution strategy, which can increase the reversible capacity of V4+/V5+ couple via lowering the energy needed during desodiation process, thus realizing a remarkable improvement of energy density. Moreover, we reveal that Fe3+substitution can improve the rate performance of cathode by reducing band gap and Na-ion diffusion activation energy. As a result, the designed Na3V1.5Al0.3Fe0.2(PO4)3 cathode delivers a high energy density of 399.7 Wh kg-1 (capacity 116.2 mAh g−1, average voltage 3.44 V) and a high rate capability (91.2% capacity retention from 0.1 C to 20 C), as well as superior cycling stability (89.5% capacity retention after 8000 cycles at 10 C). In addition, we demonstrate a 0.8 Ah 18,650-type Na3V1.5Al0.3Fe0.2(PO4)3//hard carbon full cell with 92.4% capacity retention over 400 cycles at 0.5 C. This work presents the design of high-performance phosphate cathode via bi-metallic substitution, boosting the development of practical Na-ion batteries.

Preinserted Ammonium in MnO2 to Enhance Charge Storage in Dimethyl Sulfoxide Based Zinc-Ion Batteries.

Nonaqueous zinc-ion batteries (NZIBs) featuring manganese dioxide (MnO2) cathodes position themselves as viable options for large-scale energy storage systems. Herein, we demonstrate the use of ammonium cation as a preintercalant to improve the performance of the δ-MnO2 cathode in wet dimethyl sulfoxide based electrolytes. Employing in situ X-ray absorption spectroscopy, Raman spectroscopy, and synchrotron X-ray diffraction, we reveal that the integration of ammonium cations promotes the formation of NH-O-Mn networks. These networks are crucial for manipulating the distortion of the MnO6 octahedral units during discharging, thereby mitigating charge disproportionation, which is a primary limitation to MnO2's charge-storage efficiency. The modified MnO2, through this idea, displays a notable improvement in capacity (∼247 mAh/g) and can pass charge-discharge cycles up to 500 cycles with a capacity retention of 85%. These findings underscore the potential of modified MnO2 in advancing MnO2-based hosts for Zn-MnO2 batteries, marking significant progress toward next-generation energy storage solutions.

Synthesis and characterization of new naphthalene diimides (NDIs) for application in electronic devices

This paper describes the synthesis of new naphthalene diimide (NDI) derivatives obtained in good yields from the reaction between 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA) and different p-alkoxy-substituted anilines. The photophysical properties of the NDIs were investigated in solution and the solid state. UV–visible absorption spectra in 1,4-dioxane, dichloromethane, and acetonitrile showed absorption maxima at approximately 375 nm, related to symmetry and spin allowed 1π-π* electronic transitions. These compounds did not exhibit fluorescence emission in the studied solvents. Electrochemical studies have indicated that the presence of different alkyl chains significantly affects the capacity of NDIs when used as organic cathodes in Al-graphite batteries due to variations in their ability to intercalate tetrachloroaluminate. The organic cathodes incorporating NDIs with varying alkyl chain lengths exhibited distinct capacities: 123.5 mA h g⁻1 for 3a, 101.6 mA h g⁻1 for 3b, and 157.3 mA h g⁻1 for 3c, with a capacity retention of approximately 54 % after 15 charge‒discharge cycles. These findings highlight the crucial role of alkyl chain modification in optimizing the electrochemical performance of organic cathodes.

Balancing intrinsic properties of cathode materials allows high performance for protonic ceramic fuel cells

AbstractThe cathode performance significantly impacts the overall performance of protonic ceramic fuel cells (PCFCs). Many properties of the material, such as oxygen vacancies, protonation, charge carrier transport abilities, and surface oxygen reduction reaction activity, can affect cathode performance. However, which parameter has more weight is still being debated. In this work, we use Ba0.5Sr0.5Zr0.25Fe0.65X0.1O3 as a case study (X = Zn, Cu, Mn, Ni, and Co). First‐principle calculations and experimental research are used to study and compare the critical parameters that determine cathode performance. It is discovered that no dopant can improve all the properties of the material. Balancing distinct intrinsic properties is a viable and rational approach. The more balanced, the better performance. When compared to other dopants, nickel dopant is shown to be the most effective in the Ba0.5Sr0.5Zr0.25Fe0.65X0.1O3 material system, allowing a high fuel cell performances of 1862, 1450, and 1085 mW cm−2 at 700°C, 650°C, and 600°C, with a low polarization resistance of 0.041 Ω cm2 at 700°C, which is higher than the majority of cobalt‐free cathodes for PCFCs. The current study not only presents a promising cathode candidate, but more importantly, also an effective and fundamental methodology to design cathodes for PCFCs.

Hydrogen-bonded organic framework-sulfur composite for high performance lithium–sulfur batteries

With the rapid development of energy storage devices, lithium–sulfur batteries are considered as one of the promising candidates due to their high energy density (2600 Wh Kg−1) and low cost of sulfur. Despite these advantages, the application of lithium–sulfur batteries is limited by many issues, such as the shuttle effect of polysulfide and slow redox reactions. In this paper, hydrogen-bonded organic frameworks (HOFs) materials are chosen for the first time to improve the performance of sulfur cathodes by exploiting their unique properties. Thanks to the abundant hydrogen bond of HOFs materials, which can interact with lithium polysulfide, this S-HOF composite can inhibit the shuttle of polysulfide and enhance the transformation of polysulfide. As a result, the HOF-S composite has a high initial capacity of 1100 mAh g−1 at 0.1 C and 530 mAh g−1 at 1 C. In this paper, hydrogen-bonded organic frameworks (HOFs) materials are chosen for the first time to improve the performance of sulfur cathodes. In the S-HOF, abundant hydrogen bond sites can interact with lithium polysulfide to inhibit the shuttle of polysulfide and accelerate the redox conversion of polysulfide. Therefore, the S-HOF composite has higher capacity and cycle stability. The initial capacity of the S-HOF composite is 1100 mAh g–1 at 0.1 C and 530 mAh g–1 at 1 C.

Non-metal doping enhsances oxygen reduction kinetics and CO2 tolerance of SrFeO3-δ perovskite as high-performance cathodes for solid oxide fuel cells

The sluggish of the oxygen reduction reaction (ORR) kinetics and the susceptibility to CO2 interactions are major barriers to the widespread application of solid oxide fuel cells (SOFCs). In this study, a non-metal cation doping strategy was employed to enhance the ORR catalytic activity and CO2 tolerance of SrFeO3-δ cathode. SrFe1-xPxO3-δ (SFPx, x = 0, 0.05, 0.1, 0.15, 0.2) materials were synthesized by substituting phosphorus (P) for Fe in SrFeO3-δ. The doping of P facilitated the formation of oxygen vacancies in SrFeO3-δ, enhancing oxygen adsorption, dissociation, diffusion, and charge transfer processes, leading to a notable increase in ORR catalytic activity. At 800 ℃, the polarization resistance of SFP0.15 was 0.08 Ω cm2, a reduction of 42.86 % compared to undoped SrFeO3-δ. Additionally, SFP0.15 achieved a peak power density of 749.36 mW cm2, representing a 91.99 % enhancement over SrFeO3-δ. These findings suggest that non-metal cation doping is an effective approach to boost the performance of SrFeO3-δ perovskite cathode.

Systematically evaluation of the cathodic performance of CrOBr with vacancies and partial substitutions on surface for Li metal batteries

Significant progress has been made in enhancing the kinetic and thermal stability of CrOBr. However, its full potential, especially regarding metal atom adsorption on its surface, remains largely unexplored. This study uses DFT to assess CrOBr's potential as a cathode material by evaluating its electronic structure and the interactions between metal atoms and the substrate, considering homologous substitution and vacancies. Although the investigation includes mixed cationic electrolytes (Li, Na, Mg, and Al), it primarily focuses on the behavior of Li, a common metal battery atom. Detailed calculations cover atom adsorption energy, diffusion energy barriers, band structures, density of states (DOS), and open circuit voltage (OCV) curves. The results show that Br vacancies enhance metal atom adsorption, reduce diffusion energy barriers, and maintain a high open-circuit voltage, making CrOBr a promising candidate for battery cathodes. Notably, the developed strategy for evaluating and improving CrOBr can also be applied to other electrode materials.

Chelated Metal-Organic Frameworks for Improved the Performance of High-Nickel Cathodes in Lithium-Ion Batteries.

Lithium-ion batteries have gained widespread use in various applications, including portable devices, electric vehicles, and energy storage systems. High Ni cathode, LiNixCoyMnzO2 (NCM, x ≥ 0.8, x + y + z = 1), have garnered significant attention owing to their high energy density. However, the limited lithium-ion transfer rate and transition metal cross-talk to anode pose obstacles to further improvement of electrochemical performance. To tackle these challenges, metal-organic frameworks (MOFs) with chelating agents are employed as additive materials for electrode. MOFs with chelating agents offer three key attributes: (1) Effective mitigation of transition metal cross-talk to the anode, (2) Partial desolvation of Li+ ions through MOF pores, and (3) Immobilization of anions via metal sites in the MOF. Leveraging these advantages, the chelating MOF-modified NCM cathode demonstrates reduced charge transfer resistance, both in their pristine and cycled states. In addition, they exhibit significantly improved lithium-ion diffusion coefficients after 100 cycles. These findings underscore the potential of MOFs with chelating agents as promising additive materials for enhancing the performance of LIBs.

Unlocking fast Li-ion transport in micrometer-sized Mn-based cation-disordered rocksalt cathodes

The development of cation-disordered rocksalt (DRX) cathodes has garnered worldwide attention due to their high capacity, broad chemical space and excellent structural flexibility. However, their low intrinsic Li-ion conductivity necessitates extensive particle pulverization, typically achieved through ball-milling process, which impedes large-scale production. In this work, we present a proton-exchange assisted strategy to activate the Li-ion transport in Mn-based DRX cathodes. Short-range spinel-like ordering is observed to form within the DRX matrix after the post treatment, which significantly enhances the intrinsic Li ion mobility. Notably, more than 280 mAh g−1 discharge capacity can be delivered at a slow rate from micrometer-sized particles with an overall disordered cation arrangement, which retains more than 150 mAh g−1 when cycled at a very high rate of 2000 mA g−1. Furthermore, we also demonstrate that the electrochemical performance of the post-treated cathodes can be further optimized by fine-tuning the reaction parameters.

Band structure regulation for improving the photoinduced cathodic protection performance of TiO2/ZnxIn2S3+x heterojunctions

The degree of band matching is crucial for the photoelectric conversion performance of heterojunctions. In this work, TiO2/ZnxIn2S3+x (TO/ZIS-X, X=1, 2, 3, 4) heterostructures and their electrochemical and photoelectrochemical tests were studied. According to the energy band analysis of a series of TO/ZIS-X, it is found that I-type heterojunction can be formed between TO and ZIS-1, while Z-type heterojunction would be formed between TO and ZIS-2, ZIS-3 and ZIS-4. The photoinduced potential drop associated with current density of TO/ZIS-2 in 3.5 wt% NaCl are 505.82 mV and 18.61 μA·cm−2, respectively. This result is much higher than those of homogeneous TO and single-phase ZIS-X. The desirable photoelectrochemical cathodic protection performance of the photoelectrode is owing to the loading of ZnxIn2S3+x, which broadens the light absorption threshold and improves the electrochemical activity area. Besides, the construction of Z-type heterojunction retains the photogenerated electrons/holes with strong reduction/oxidation ability, which greatly promotes the photoelectrochemical cathodic protection capability on 316 L stainless steel.

Impact of high-temperature storage on capacity fading of Ni-rich cathodes in sulfide-based all-solid-state batteries

Despite the extensive research efforts focused on enhancing the lifespan and energy density of all-solid-state batteries, the calendar aging behavior of cathodes within the all-solid-state batteries system continues to be underexplored. In this study, we elucidate the capacity fading of Ni-rich cathodes in sulfide-based all-solid-state batteries after high-temperature storage using electrochemical techniques, synchrotron X-ray-based characterization tools, and electron microscopy. High-temperature storage negatively affects the electrochemical performance of Ni-rich cathodes, limiting their charge and discharge capacities, notably charge fading. The underlying cause of capacity fading lies in interfacial side reactions between Ni-rich cathode materials and solid electrolytes. The LiNbO3 coating layer is found to be effective in preventing interfacial degradation, which virtually eliminates charge and discharge fading. These findings offer a deeper understanding of the capacity fading of Ni-rich cathodes in sulfide-based all-solid-state battery systems during high-temperature storage. Furthermore, they provide insights for achieving all-solid-state batteries with high thermal durability and energy density.

Relieving strain accumulation in ultra-high Ni cathode to achieve long cycle stability

Ni-rich cathodes with nickel content exceeding 90 % are regarded as highly promising for lithium-ion batteries (LIBs). However, the chemical-mechanical degradation caused by strain, side reactions and irreversible phase transitions will accelerate capacity fading. Especially, the mechanical degradation (cracks) caused by anisotropic strain can also accelerate chemical degradation. Herein, we effectively alleviate the anisotropic strain and the resulting cracks by Ti doping, which successfully improved the electrochemical performance of ultra-high Ni cathode. The results demonstrated that Ti doping can effectively refine the primary particles and form a tightly packed structure. Moreover, the stronger Ti-O bond incorporation into bulk efficiently stabilize lattice structure. The unique microstructure and stable lattice structure can effectively alleviate strain accumulation and chemical-mechanical degradation. Therefore, the Ti-modified cathode has the excellent electrochemical performance.

Graphene Intermediate Layer for Robust and Spectrum-Extended Cu Photocathode Activated with Cs and O.

Developing an effective method to stably enhance the quantum efficiency (QE) and extend the photoemission threshold of Cu photocathodes beyond the ultraviolet region could benefit the photoinjector for ultrafast electron source applications. The implementation of a 2D material protective layer is considered a promising approach to extending the operating lifetime of photocathodes. We propose that graphene can serve as an intermediate layer at the interface between photocathode material and low-work-function coating. The role of oxygen in the Cs/O activation process on the Cu surface is altered by the graphene interlayer. Besides, the few-layer graphene (FLG) surface could be more likely to induce the formation of Cs2O. Thus, the graphene-Cu composite photocathode can achieve an ultralow surface work function of down to 0.878 eV through Cs/O activation. The photoemission performance of the composite cathode with a FLG interlayer is significantly enhanced. The photocathode has an extended spectral response to the near-infrared region and a higher QE. At 350 nm, its QE is more than twice that of the cesiated bare Cu, reaching 0.247%. After degradation, the graphene-Cu cathode can be fully restored by reactivation, with remarkably enhanced stability. In addition, the composite cathode can be operated reliably under a poor vacuum pressure of over 4 × 10-6 Pa. This study validates a new method for incorporating 2D materials into photocathodes, offering novel approaches to explore robust and spectrum-extended photocathodes.

Role of site–specific doping in stabilizing high–nickel cathodes for high-performance lithium- ion -batteries

The growing demand for high-capacity and energy-dense lithium-ion batteries has driven the increase of nickel content in commercially available cathodes. However, during deep charging (delithiation), these Ni-rich cathodes experience a detrimental phase transformation and a sudden, significant decrease in lattice volume. This lattice collapse is considered the primary culprit behind the limitations in the cathode's electrochemical performance. Notably, the exact cause-and-effect relationship between the phase change and the collapse remains unclear. In the present study, the effect of the site of substitution on the performance of the LiNiO2 cathode has been investigated by adopting tungsten as a dopant. To gain deeper insights into this connection within Ni-rich LiNiO2, the contraction of the c-axis and the change in the a-axis during the delithiation have been investigated using ab initio density functional theory. Findings reveal that the free energy difference between the suspected phases in Ni-rich LiNiO2 is minimal at room temperature, facilitating the transition from the H2 to the H3 phase. This transition appears to be driven by the movement (gliding) of the NiO2 layer towards the adjacent Li layer. The findings of the present study indicate that among two different configurations due to different sites of substitution, the WLNO-2 configuration suppresses H2 –H3 phase conversion to a greater extent by hindering the gliding of the NiO2 layer toward the Li layer. Furthermore, a reduction in the collapse of the c-axis lattice during deep de-lithiation for the WLNO-2 configuration has been observed. This reduced collapse is primarily attributed to the altered charge distribution within oxygen atoms and the weakened screening effect from lithium ions.

Fluorine Doping for Improved Lithium and Manganese-Rich Layered Cathode Performance

Fluorine Doping for Improved Lithium and Manganese-Rich Layered Cathode Performance

Investigation of an Industrially Scalable Production of Sulfur‐Polyacrylonitrile Based Cathodes

AbstractSulfur‐polyacrylonitrile (SPAN) is a sulfur‐based active material for next‐generation lithium‐sulfur battery cathodes. Due to the covalent bonding between sulfur chains and the polymeric backbone, the shuttle effect degrading classical sulfur‐based cathodes can be suppressed while also achieving a high active material content in the cathode. In this paper, we investigate the processability of an industrially scalable SPAN active material with 38 wt.‐% of sulfur in a water‐based and scalable process route. The potential of the SPAN material for industrial adoption and the impact of the process route on the cell performance are discussed. We show that when processed correctly, the SPAN material delivers exceptional cycling stability and good C‐rate performance with ether‐based electrolytes. However, the performance of the SPAN cathode is influenced by the mixing characteristic. Using higher mixing intensities during the slurry preparation leads to deterioration of the electrochemical performance. This can be attributed to a decreasing carbon black percolation with increasing tip speed in combination with the kinetic limitation of sulfur cathodes during Li2S2 and Li2S oxidation.

Recycling and Reuse of Mn-Based Spinel Electrode from Spent Lithium-Ion Batteries

In this paper, we introduce an environmentally friendly approach to recycle used batteries and recover highly valuable manganese-based cathode materials. This study demonstrates the feasibility of fast plasma pyrolysis to recover LiMn2O4 electrode materials (e.g., lithium manganese oxide, LMO) and demonstrate their reuse in newly assembled Li-ion cells. The electrochemical performance of as-recycled cathodes shows an initial discharge capacity of 72 mAh/g and is stable for 100 cycles at 0.1 C. After adding 20 mole % of excess LiOH, the recycled LMO after relithiation at 660 °C can deliver an initial discharge capacity of 96 mAh/g and retain a decent discharge capacity of 88 mAh/g after 50 cycles at a 0.2 C rate. Without relithiation, the as-recycled LMO cathode after heating at 1000 °C delivers the best electrochemical cycling performance, including an initial discharge capacity of 94 mAh/g and 50th cycle capacity of 91 mAh/g at a 0.2 C rate. This study highlights a feasible approach for recycling electrode materials in spent LIBs. Recycling of lithium-ion batteries and especially electrode materials is crucial for the sustained growth of the lithium-ion battery industry and reduced environmental issues.