Layered Cathode Materials Research Articles

A-Site Engineering of the High-Entropy Perovskite Pr0.4La0.4Ba0.4Sr0.4Ca0.4Fe2O5+δ Cathode for Intermediate-Temperature SOFCs.

Mixed-oxygen ionic and electronic conduction is crucial for the cathode materials of solid oxide fuel cells, ensuring high efficiency and low-temperature operation. However, the electronic and oxygen ionic conductivity of traditional Fe-based layered perovskite cathode materials is low, resulting in insufficient oxygen reduction reactivity. Herein, a type of high-entropy perovskite oxide consisting of five equimolar metals, Pr0.4La0.4Ba0.4Sr0.4Ca0.4Fe2O5+δ (PLBSCF), a high-performance cobalt-free cathode derived from the PrBaFe2O5+δ (PBF), is proposed. Such A-site engineering could not only increase the oxygen vacancy concentration of PLBSCF but also give higher conductivity than PBF, thus significantly reducing the polarization impedance of the symmetric cell to only 0.052 Ω·cm2 at 750 °C. The good output performance of a single cell is also realized. The peak power density of the single cell with PLBSCF-Ce0.9Gd0.1O2-δ (GDC) as the cathode at 750 °C was 0.853 W·cm-2. Additionally, the single cell with the PLBSCF cathode exhibits a good durable performance of 100 h at 750 °C. Combining the distribution of relaxation time analysis, it can be seen that the enhancement of the oxygen reduction reaction is due to the reduction of intermediate-frequency and low-frequency resistance, indicating an improvement in the charge transfer process and adsorption/dissociation process of molecular oxygen.

An Active Strategy to Reduce Residual Alkali for High-Performance Layered Oxide Cathode Materials of Sodium-Ion Batteries.

Residual alkali is one of the biggest challenges for the commercialization of sodium-based layered transition metal oxide cathode materials since it can even inevitably appear during the production process. Herein, taking O3-type Na0.9Ni0.25Mn0.4Fe0.2Mg0.1Ti0.05O2 as an example, an active strategy is proposed to reduce residual alkali by slowing the cooling rate, which can be achieved in one-step preparation method. It is suggested that slow cooling can significantly enhance the internal uniformity of the material, facilitating the reintegration of Na+ into the bulk material during the calcination cooling phase, therefore substantially reducing residual alkali. The strategy can remarkably suppress the slurry gelation and gas evolution and enhance the structural stability. Compared to naturally cooled cathode materials, the capacity retention of the slowly cooled electrode material increases from 76.2% to 85.7% after 300 cycles at 1C. This work offers a versatile approach to the development of advanced cathode materials toward practical applications.

One-Step Realization of Layered/Spinel Heterostructures and Na Doping by Sodium Dodecyl Sulfate-Assisted Sol-Gel Method for Li-Ion Batteries.

Li-rich layered oxide cathodes have attracted extensive attention due to their high energy density. However, due to the low initial Coulombic efficiency and the capacity fading and voltage fading during cycling, its practical application is still a great challenge. Here, we report the one-step realization of layered/spinel heterostructures and Na doping by the sodium dodecyl sulfate (SDS)-assisted sol-gel method. The spinel phase provides 3D diffusion channels for Li-ions, and sodium doping changes the layered lattice constant and expands the layer spacing. Therefore, the designed Li1.15Mn0.54Ni0.13Co0.13Na0.05O2 (SDS-2) cathode possesses excellent electrochemical performance such as higher initial Coulombic efficiency and rate capacity and also alleviates voltage decay. The initial discharge-specific capacity of SDS-2 is 298.8 mAh g-1 at 0.1 C, and the discharge-specific capacity can reach 111.7 mAh g-1 at 10 C. This strategy can provide new insights into the design and synthesis of high-performance Li-rich layered oxide cathode materials.

High‐entropy configuration strategy boosts excellent rate performance of layered oxide for sodium‐ion batteries

AbstractLayered oxides are considered to be potential cathodes for sodium‐ion batteries based on high theoretical capacity and ease of synthesis. However, the complex phase transition caused by interlayer sliding in layered oxides leads to poor cycling stability, which will hinder their further application. Here, we designed a newly O3‐type layered cathode NaNi0.3Co0.2Cu0.1Mn0.2Ti0.2O2 based on high‐entropy to achieve highly reversible phase transition behavior. It reveals 132 mAh g−1 at 0.2 C within 2–4 V increasing the energy density to 408 Wh kg−1 and it shows an outstanding rate capability of 90 mAh g−1 at 80 C (84.90% capacity retention after 1,500 cycles at 80 C). In‐situ XRD shows that reasonable design of high‐entropy components in layered material can achieve the purpose of delaying the occurrence of phase transition and DFT calculations show that the introduction of Co in transition metal layers can effectively improve the rate performance of the material. This work is of great significance in guiding the design and synthesis of highly stable layered cathode materials for sodium‐ion batteries.

Rational design of practical layered transition metal oxide cathode materials for sodium-ion batteries

Rational design of practical layered transition metal oxide cathode materials for sodium-ion batteries

Cut-off voltage influencing the voltage decay of single crystal lithium-rich manganese-based cathode materials in lithium-ion batteries

The voltage decay of Li-rich layered oxide cathode materials results in the deterioration of cycling performance and continuous energy loss, which seriously hinders their application in the high-energy–density lithium-ion battery (LIB) market. However, the origin of the voltage decay mechanism remains controversial due to the complex influences of transition metal (TM) migration, oxygen release, indistinguishable surface/bulk reactions and the easy intra/inter-crystalline cracking during cycling. We investigated the direct cause of voltage decay in micrometer-scale single-crystal Li1.2Mn0.54Ni0.13Co0.13O2 (SC-LNCM) cathode materials by regulating the cut-off voltage. The redox of TM and O2− ions can be precisely controlled by setting different voltage windows, while the cracking can be restrained, and surface/bulk structural evaluation can be monitored because of the large single crystal size. The results show that the voltage decay of SC-LNCM is related to the combined effect of cation rearrangement and oxygen release. Maintaining the discharge cutoff voltage at 3 V or the charging cutoff voltage at 4.5 V effectively mitigates the voltage decay, which provides a solution for suppressing the voltage decay of Li-rich and Mn-based layered oxide cathode materials. Our work provides significant insights into the origin of the voltage decay mechanism and an easily achievable strategy to restrain the voltage decay for Li-rich and Mn-based cathode materials.

Probing Particle-Carbon/Binder Degradation Behavior in Fatigued Layered Cathode Materials through Machine Learning Aided Diffraction Tomography.

Understanding how reaction heterogeneity impacts cathode materials during Li-ion battery (LIB) electrochemical cycling is pivotal for unraveling their electrochemical performance. Yet, experimentally verifying these reactions has proven to be a challenge. To address this, we employed scanning μ-XRD computed tomography to scrutinize Ni-rich layered LiNi0.6Co0.2Mn0.2O2 (NCM622) and Li-rich layered Li[Li0.2Ni0.2Mn0.6]O2 (LLNMO). By harnessing machine learning (ML) techniques, we scrutinized an extensive dataset of μ-XRD patterns, about 100,000 patterns per slice, to unveil the spatial distribution of crystalline structure and microstrain. Our experimental findings unequivocally reveal the distinct behavior of these materials. NCM622 exhibits structural degradation and lattice strain intricately linked to the size of secondary particles. Smaller particles and the surface of larger particles in contact with the carbon/binder matrix experience intensified structural fatigue after long-term cycling. Conversely, both the surface and bulk of LLNMO particles endure severe strain-induced structural degradation during high-voltage cycling, resulting in significant voltage decay and capacity fade. This work holds the potential to fine-tune the microstructure of advanced layered materials and manipulate composite electrode construction in order to enhance the performance of LIBs and beyond.

Probing Particle‐Carbon/Binder Degradation Behavior in Fatigued Layered Cathode Materials through Machine Learning Aided Diffraction Tomography

AbstractUnderstanding how reaction heterogeneity impacts cathode materials during Li‐ion battery (LIB) electrochemical cycling is pivotal for unraveling their electrochemical performance. Yet, experimentally verifying these reactions has proven to be a challenge. To address this, we employed scanning μ‐XRD computed tomography to scrutinize Ni‐rich layered LiNi0.6Co0.2Mn0.2O2 (NCM622) and Li‐rich layered Li[Li0.2Ni0.2Mn0.6]O2 (LLNMO). By harnessing machine learning (ML) techniques, we scrutinized an extensive dataset of μ‐XRD patterns, about 100,000 patterns per slice, to unveil the spatial distribution of crystalline structure and microstrain. Our experimental findings unequivocally reveal the distinct behavior of these materials. NCM622 exhibits structural degradation and lattice strain intricately linked to the size of secondary particles. Smaller particles and the surface of larger particles in contact with the carbon/binder matrix experience intensified structural fatigue after long‐term cycling. Conversely, both the surface and bulk of LLNMO particles endure severe strain‐induced structural degradation during high‐voltage cycling, resulting in significant voltage decay and capacity fade. This work holds the potential to fine‐tune the microstructure of advanced layered materials and manipulate composite electrode construction in order to enhance the performance of LIBs and beyond.

Advanced Molecular Layer Deposition of SixZnyOz Thin Film Coatings for Improved Electrochemical Performance of NMC811

AbstractThe practical realization of Nickel‐rich layered oxide cathode materials such as LiNi0.8Mn0.1Co0.1O2 (NMC811) is hampered by several structural and interfacial instabilities over prolonged cycling. Several reports have proposed surface passivation via an artificial cathode electrolyte interphase (ACEI) as a promising method for mitigating the parasitic reactions affecting NMC811 while simultaneously improving its electrochemical performance over prolonged cycling. Herein, we report an in‐house designed (tBuMe2Si)2Zn single source precursor for developing SixZnyOz ternary CEI thin films on NMC811 via molecular layer deposition (MLD) in combination with O3 or H2O as oxidizing agent. We demonstrate that the single precursor (tBuMe2Si)2Zn avoids the need for two different precursors (Si & Zn). In‐depth spectroscopic studies reveal the mechanism of the formation of organosiloxane/zinc‐oxide composite thin film, via intermediates of unprecedented organo‐silicon‐zinc compounds. Understanding the reaction mechanism paved the path for a successful deposition of ACEI on NMC811. Rate capability studies shows the ACEI protected cathodes exhibit higher discharge capacity at 4 C than pristine NMC811. Furthermore, studies on full cells with graphite anode were conducted to evaluate the practical viability of SixZnyOz ACEI thin films on NMC811. After prolonged cycling the ACEI‐coated NMC811 full cells significantly improved the electrochemical performance than pristine NMC811 by ~12%.

Surface engineering of P2-type cathode material targeting long-cycling and high-rate sodium-ion batteries

The widespread interest in layered P2-type Mn-based cathode materials for sodium-ion batteries (SIBs) stems from their cost-effectiveness and abundant resources. However, the inferior cycle stability and mediocre rate performance impede their further development in practical applications. Herein, we devised a wet chemical precipitation method to deposit an amorphous aluminum phosphate (AlPO4, denoted as AP) protective layer onto the surface of P2-type Na0.55Ni0.1Co0.1Mn0.8O2 (NCM@AP). The resulting NCM@5AP electrode, with a 5 wt% coating, exhibits extended cycle life (capacity retention of 78.4% after 200 cycles at 100 mA g−1) and superior rate performance (98 mA h g−1 at 500 mA g−1) compared to pristine NCM. Moreover, our investigation provides comprehensive insights into the phase stability and active Na+ ion kinetics in the NCM@5AP composite electrode, shedding light on the underlying mechanisms responsible for the enhanced performance observed in the coated electrode.

New Insight into Bulk Structural Degradation of High-Voltage LiCoO2 at 4.55 V.

The aggravated mechanical and structural degradation of layered oxide cathode materials upon high-voltage charging invariably causes fast capacity fading, but the underlying degradation mechanisms remain elusive. Here we report a new type of mechanical degradation through the formation of a kink band in a Mg and Ti co-doped LiCoO2 cathode charged to 4.55 V (vs Li/Li+). The local stress accommodated by the kink band can impede crack propagation, improving the structural integrity in a highly delithiated state. Additionally, machine-learning-aided atomic-resolution imaging reveals that the formation of kink bands is often accompanied by the transformation from the O3 to O1 phase, which is energetically favorable as demonstrated by first-principles calculations. Our results provide new insights into the mechanical degradation mechanism of high-voltage LiCoO2 and the coupling between electrochemically triggered mechanical failures and structural transition, which may provide valuable guidance for enhancing the electrochemical performance of high-voltage layered oxide cathode materials for lithium-ion batteries.

Approaching Ultimate Synthesis Reaction Rate of Ni-Rich Layered Cathodes for Lithium-Ion Batteries

HighlightsA series of layered oxide cathode materials were synthesized by high-temperature shock strategy for the first time.The approaching ultimate solid reaction rate of the layered nickel-rich layered oxide LiNixCoyMnzO2 was investigated for the first time. Ultrafast average reaction rate of phase transition from Ni0.6Co0.2Mn0.2(OH)2 to Li-containing oxides is 66.7 (% s-1), that is, taking only 1.5 s.

Strengthening the interfacial stability of single-crystal LiNi0.88Co0.09Mn0.03O2 cathode with multiple-function surface modification

The instability in the structural integrity caused by interfacial issues is commonly regarded as the primary drawback of Ni-rich layered cathode materials (LiNixCoyMn1-x-yO2, where x ≥ 0.8), which must be addressed before their commercial application. Herein, a novel multiple-function surface modification strategy is proposed based on the single crystal structure to in-situ achieve the construction of a coating layer and surface doping with Ce element to enhance the structural stability of the LiNi0.88Co0.09Mn0.03O2 (NCM). Notably, the introduction of Ce-O bonding adjusts the local oxygen coordination to achieve a more stabilized structure of the oxygen framework, which inhibits the evolution of lattice oxygen and enhances conductivity. Additionally, by benefiting from the in-situ synthesized coating layer of LixCeO2, the occurrence of side reactions on the surface is effectively alleviated, resulting in a reduction in electrode polarization. Combined with comprehensive electrochemical tests, it is confirmed that the improved electrochemical performance originates from the reduction of the detrimental H2-H3 phase transition and enhanced conductivity. As expected, the modified material with 1 wt% content of Ce (NCM@Ce) exhibits a high initial discharge capacity of 196.3 mAh g−1 with a capacity retention of 79.7 % after 200 cycles, and its energy density reaches 574.3 Wh kg−1 after 200 cycles.

Highly reversible transition metal migration in superstructure-free Li-rich oxide boosting voltage stability and redox symmetry

The further practical applications of Li-rich layered oxides are impeded by voltage decay and redox asymmetry, which are closely related to the structural degradation involving irreversible transition metal migration. It has been demonstrated that the superstructure ordering in O2-type materials can effectively suppress voltage decay and redox asymmetry. Herein, we elucidate that the absence of this superstructure ordering arrangement in a Ru-based O2-type oxide can still facilitate the highly reversible transition metal migration. We certify that Ru in superstructure-free O2-type structure can unlock a quite different migration path from Mn in mostly studied cases. The highly reversible migration of Ru helps the cathode maintain the structural robustness, thus realizing terrific capacity retention with neglectable voltage decay and inhibited oxygen redox asymmetry. We untie the knot that the absence of superstructure ordering fails to enable a high-performance Li-rich layered oxide cathode material with suppressed voltage decay and redox asymmetry.

Exploring the Effect of TiO2 Coating on Na0.85Li0.12Ni0.22Mn0.66O2 Cathode Materials for Na-Ion Batteries

Layered transition metal oxides have great potential as cathode materials for sodium ion batteries, but some limitations like structural instability and poor rate performance restricts its further application. To overcome the above issues, a simultaneously modified P2-type cathode of Na0.85Li0.12Ni0.22Mn0.66O2 with 1% weight TiO2 coating (NLNMO-1%wt TiO2) based on doping and coating approaches was prepared by high-temperature solid-state reaction and liquid phase coating. This new strategy reduces the relative content of Mn3+, which suppresses the Jahn-Teller effect and enhanes the structural stability. The as-prepared cathode shows improved rate capability, with a high reversible capacity of 111.4 mAh g−1 at 1 C and a capacity retention of 94.5% after 100 cycles. At 5 C, it maintains a capacity of 87.1 mAh g−1 at 5 C with capacity retention of 81.8% after 400 cycles. Additionally, it provides a stable CEI film, reducing side reactions and electrode pulverization. which could be confirmed by scanning electron microscopy and high-resolution transmission electron microscopy. Overall, this synergistic modification strategy provides a pathway for improving the electrochemical performance of layered oxide cathode materials for sodium-ion batteries.

Preface

Abstract The 2023 4th International Conference on Material Chemistry and Composite Materials (MCCM 2023) took place during December 22nd to 24th, 2023 in Sanya, China. MCCM exists as an annual international academic conference which tries to meet the needs for various kinds of material chemistry and composite materials. Bearing the principle of “bringing together global wisdom in scientific innovation to promote high-quality development”, MCCM 2023 encouraged the exchange of information on research frontiers in different fields related to material chemistry and composite materials, connected the most advanced academic resources at home and abroad, and turned research results into industrial solutions. It also promoted the development of related disciplines, expanded the international scientific and academic exchange channels, enhanced scientific innovation on a global scale, and contributed to academic cooperation between China and the international community. The Conference was attended by about 100 participants and hosted 6 keynote speeches, many oral and poster presentations, as well as Questions & Answer part. The topics of the 4th MCCM cover various research fields where material chemistry and composite materials are applied, such as Surface Chemistry, New Energy Materials, Nanotechnology and Materials, Physical and Structural Properties of Materials, Multiferroic Materials and Composites, etc. According to all the attendees, the scientific program was excellent with high level of presentations and the scientific environment was fruitful, thus all of them had a great and creative time. In the keynote speech part, Professor Liguang Wang (Zhejiang University, China) shared his research on Understanding the Degradation Mechanisms in High-Energy Density Cathodes via Synchrotron X-Ray Techniques. To advance the development of the next generation of high-energy-density cathode materials, his research endeavors have systematically unraveled the intricacies of performance degradation mechanisms inherent in layered structure cathodes. This exploration leveraged a sophisticated combination of advanced synchrotron X-ray-based characterization techniques across multiple scales. His investigation has been transformative, shedding light on the intrinsic correlation between stress-strain dynamics and mechanical degradation within layered cathode materials. With rounds of dramatic researches sharing and ideas exchanging, the Conference was made filled with academic atmosphere. We would like to thank Beihang University, China for its support. We would also like to acknowledge the members of the Organizing Committee and Technical Program Committee for their preparation and suggestion on the Conference. Our gratitude also goes to the members of Journal of Physics: Conference Series for their support in publishing this paper volume. The Committee of MCCM 2023 List of Committee Member is available in this pdf.

Cycling performance of layered oxide cathode materials for sodium-ion batteries

Cycling performance of layered oxide cathode materials for sodium-ion batteries

Surface encapsulation of layered oxide cathode material with NiTiO3 for enhanced cycling stability of Na-ion batteries

Abstract In Na-ion batteries, O3-type layered oxide cathode materials encounter challenges such as particle cracking, oxygen loss, electrolyte side reactions, and multi-phase transitions during the charge/discharge process. This study focuses on surface coating with NiTiO3 achieved via secondary heat treatment using a coating precursor and the surface material. Through in-situ x-ray diffraction (XRD) and differential electrochemical mass spectrometry (DEMS), along with crystal structure characterizations of post-cycling materials, it was determined that the NiTiO3 coating layer facilitates the formation of a stable lattice structure, effectively inhibiting lattice oxygen loss and reducing side reaction with the electrolyte. This enhancement in cycling stability was evidenced by a capacity retention of approximately 74% over 300 cycles at 1 C, marking a significant 30% improvement over the initial sample. Furthermore, notable advancements in rate performance were observed. Experimental results indicate that a stable and robust surface structure substantially enhances the overall stability of the bulk phase, presenting a novel approach for designing layered oxide cathodes with higher energy density.

Polycrystalline secondary particle size regulation boosts the cycle performance of ultra-high-nickel layered oxide cathode materials

The ultra-high-nickel layered oxide cathodes of LiNixCoyMn1-x-yO2 (NCM, and x ≥ 0.9) have been considered promising candidates to meet the growing demand for high-energy-density lithium-ion batteries (LIBs) due to their high specific capacity. However, their capacity retention tends to be low in practical applications due to the instability of their structure during charge and discharge cycles. Herein, a strategy for regulating secondary particle size is put forward to alleviate the crystal volume change and suppress the H2-H3 phase transitions, ultimately stabilizing the structure against microcrack development and improving the cycle performance of the ultra-high-nickel layered oxide cathodes. The results show that LiNi0.90Co0.05Mn0.05O2 (NCM90) with a D50 of 8.6 μm (NCM90–9) exhibits the optimum electrochemical performance compared to its counterparts, which delivers a high cycling stability (91.86 % capacity retention after 200 cycles at 0.5 C) and a good rate performance (127.3 mAh·g-1 at 6 C). The superior performance of NCM90–9 is attributed to the suppression of microcracks within secondary particles and parasitic reactions with the electrolyte, which are determined by its secondary particle size. This result provides valuable guidelines for the development of ultra-high-nickel layered oxide cathodes.

Electron Beam-Induced Effects on a Ni-Rich Layered Cathode Material: A Comprehensive Investigation Using STEM and EELS

Electron Beam-Induced Effects on a Ni-Rich Layered Cathode Material: A Comprehensive Investigation Using STEM and EELS