Layered Oxide Electrodes Research Articles

Substantial oxygen loss and chemical expansion in lithium-rich layered oxides at moderate delithiation.

Delithiation of layered oxide electrodes triggers irreversible oxygen loss, one of the primary degradation modes in lithium-ion batteries. However, the delithiation-dependent mechanisms of oxygen loss remain poorly understood. Here we investigate the oxygen non-stoichiometry in Li1.18-xNi0.21Mn0.53Co0.08O2-δ electrodes as a function of Li content by using cycling protocols with long open-circuit voltage steps at varying states of charge. Surprisingly, we observe substantial oxygen loss even at moderate delithiation, corresponding to 2.5, 4.0 and 7.6 ml O2 per gram of Li1.18-xNi0.21Mn0.53Co0.08O2-δ after resting at upper capacity cut-offs of 135, 200 and 265 mAh g-1 for 100 h. Our observations suggest an intrinsic oxygen instability consistent with predictions of high oxygen activity at intermediate potentials versus Li/Li+. In addition, we observe a large chemical expansion coefficient with respect to oxygen non-stoichiometry, which is about three times greater than those of classical oxygen-deficient materials such as fluorite and perovskite oxides. Our work challenges the conventional wisdom that deep delithiation is a necessary condition for oxygen loss in layered oxide electrodes and highlights the importance of calendar ageing for investigating oxygen stability.

Surface and Grain Boundary Coating for Stabilizing LiNi0.8Mn0.1Co0.1O2 Based Electrodes.

The widespread use of high-capacity Ni-rich layered oxides such as LiNi0.8Mn0.1Co0.1O2 (NMC811), in lithium-ion batteries is hindered due to practical capacity loss and reduced working voltage during operation. Aging leads to defective NMC811 particles, affecting electrochemical performance. Surface modification offers a promising approach to improve cycle life. Here, we introduce an amorphous lithium titanate (LTO) coating via atomic layer deposition (ALD), not only covering NMC811 surfaces but also penetrating cavities and grain boundaries. As NMC811 electrodes suffer from low structural stability during charge and discharge, We combined electrochemistry, operando X-ray diffraction (XRD), and dilatometry to understand structural changes and the coating protective effects. XRD reveals significant structural evolution during delithiation for uncoated NMC811. The highly reversible phase change in coated NMC811 highlights enhanced bulk structure stability. The LTO coating retards NMC811 degradation, boosting capacity retention from 86 % to 93 % after 140 cycles. This study underscores the importance of grain boundary engineering for Ni-rich layered oxide electrode stability and the interplay of chemical and mechanical factors in battery aging.

Stabilization of P2 layered oxide electrodes in sodium-ion batteries through sodium evaporation

Sodium-ion batteries are well positioned to become, in the near future, the energy storage system for stationary applications and light electromobility. However, two main drawbacks feed their underperformance, namely the irreversible sodium consumption during solid electrolyte interphase formation and the low sodiation degree of one of the most promising cathode materials: the P2-type layered oxides. Here, we show a scalable and low-cost sodiation process based on sodium thermal evaporation. This method tackles the poor sodiation degree of P2-type sodium layered oxides, thus overcoming the first irreversible capacity as demonstrated by manufacturing and testing all solid-state Na doped-Na~1Mn0.8Fe0.1Ti0.1O2 ǀǀ PEO-based polymer electrolyte ǀǀ Na full cells. The proposed sodium physical vapor deposition method opens the door for an easily scalable and low-cost strategy to incorporate any metal deficiency in the battery materials, further pushing the battery development.

A phase inversion strategy for low-tortuosity and ultrahigh-mass-loading nickel-rich layered oxide electrodes

A phase inversion strategy for low-tortuosity and ultrahigh-mass-loading nickel-rich layered oxide electrodes

Advanced TiO2/Al2O3 Bilayer ALD Coatings for Improved Lithium-Rich Layered Oxide Electrodes.

Surface modification is a highly effective strategy for addressing issues in lithium-rich layered oxide (LLO) cathodes, including phase transformation, particle cracking, oxygen gas release, and transition-metal ion dissolution. Existing single-/double-layer coating strategies face drawbacks such as poor component contact and complexity. Herein, we present the results of a low-temperature atomic layer deposition (ALD) process for creating a TiO2/Al2O3 bilayer on composite cathodes made of AS200 (Li1.08Ni0.34Co0.08Mn0.5O2). Electrochemical analysis demonstrates that TiO2/Al2O3-coated LLO electrodes exhibit improved discharge capacities and enhanced capacity retention compared with uncoated samples. The TAA-5/AS200 bilayer-coated electrode, in particular, demonstrates exceptional capacity retention (∼90.4%) and a specific discharge capacity of 146 mAh g-1 after 100 cycles at 1C within the voltage range of 2.2 to 4.6 V. The coated electrodes also show reduced voltage decay, lower surface film resistance, and improved interfacial charge transfer resistances, contributing to enhanced stability. The ALD-deposited TiO2/Al2O3 bilayer coatings exhibit promising potential for advancing the electrochemical performance of lithium-rich layered oxide cathodes in lithium-ion batteries.

Electrophoretic deposition of graphene oxide as a stabilizing layer on the Ni-rich layered oxide electrodes for enhancing the cycling stability of Li-ion cathodes

One of the critical challenges for layered Ni-rich cathode material is the surface degradation caused by the parasitic reaction between the cathode material and the organic electrolytes. Herein, we develop an overall electrode modification strategy to improve the cathode surface's structural stability by integrating graphene oxide (GO) coating on the surface of the cathode electrode with the assistance of the electrophoretic deposition technique (EPD). The attenuated total reflectance (ATR) and scanning electron microscope (SEM) results confirm the formation of the uniform thin GO layer on the surface of the Ni-rich cathode. The electrochemical studies such as galvanostatic charge-discharge, galvanostatic intermittent titration Technique (GITT), and incremental capacity analysis (ICA) tests show that the existence of thin layers of GO not only does not hinder the intercalation of Li+ ions but also can facilitate the charge transfer and intercalation of Li+ ions by decreasing the charge transfer resistance of the electrode. The cycling stability of the cathode coated with GO in 30 s of EPD shows better performance over 150 charge-discharge cycles and lower Rct than the pristine electrode. Our work provides a design idea for stabilizing the surface/bulk structure of advanced Ni-rich cathode for high-performance Li-ion batteries.

Tailoring the MAX phase additive for enhanced electrochemical performance of high Ni layered oxide composite electrode

The new strategy of MAX phase application in the LIB's cathode composite with high nickel content was suggested in this work. Two MAX phase candidates – TSC and TAC (Ti3SiC2 and Ti3AlC2, respectively) – with outstanding electronic conductivity were used as LiNi0.85Co0.10Mn0.05O2-cathode composite (NCM) additive in amount of 1 % by weight. Structural and morphology monitoring was conducted on each stage of NCM-modification, performed by wet route with post-heat treatment of active material (AM). We found the optimal post-heat temperature (400 °C) to prepare TSC-composite electrode with the enhanced cycling stability – its capacity retention was 96 % and 89 % after 50 cycles at room and elevated temperature of cycling test, respectively. Based on the morphology of MAX phases milled particles with flaky shape, oxidation stability evaluation and electrode resistance measurements we presented here the mechanism of MAX-phase influence on electrochemical performance of high Ni layered oxide electrode composite.

Application of sodium battery electrode in low temperature ceramic fuel cells

Layered transition metal oxides are promising high energy density electrodes for lithium/sodium batteries. Herein we study the application of commercial sodium battery electrode material MS-XN-33S-Ternary sodium nickel-ferric manganate layered oxide (NFMNa) in low temperature ceramic fuel cells (LT-CFCs). We investigate its crystal structure, microstructure, surface state, and applying it as the electrolyte functional layer for fuel cells. By using electron microscopy and surface analysis characterization techniques, it is determined that in addition to layered material NaNi0.34Fe0.33Mn0.33O2, there is also polycrystalline Na2CO3 in the NFMNa materials. NFMNa electrolyte fuel cells devices have 0.102 S cm−1 ion conductivity at 520 °C. NFMNa materials have proton conduction at 400–600 °C and no oxygen ion conduction, which is tested using hydrogen and oxygen concentration cells. BaZr0.1Ce0.7Y0.2O3-δ (BZCY) has better compatibility with electrode LiNi0.8Co0.15Al0.05O2 (NCAL) than NFMNa. Cell devices with BZCY buffer layer have better low-temperature performance, obtaining a power density of 123 mW cm−2 at 340 °C. And the NCAL (anode)-BZCY/NFMNa-NCAL (cathode) device achieve a constant current of 100 mA cm−2 for 110 h discharge output. This work contributes to the development of LT-CFCs electrolytes and a comprehensive understanding of the material properties of layered oxide electrodes in lithium/sodium batteries.

Improved electrochemical performance of surface-modified lithium-rich layered oxide electrodes with indium tin oxide (ITO) coating by magnetron sputtering

Improved electrochemical performance of surface-modified lithium-rich layered oxide electrodes with indium tin oxide (ITO) coating by magnetron sputtering

(Invited) Overview of the Ordering Phenomena in Li and Na Layered Oxide Electrode Materials

AX(M)O2 layered oxides (A = Li, Na) are considered as the best positive electrode materials either for Li ion and Na ion batteries. In most of the systems, the shape of the voltage curve shows change in slope of the curve which indicate the occurrence of structural transitions due to: (i) electronic configuration modification in the MO2 slab, (ii) change in the slab packing, (iii) alkali ion-vacancy ordering. Moreover, in AX(M,L)O2 materials a M/L ordering can occur within the (M,L)O2 slab for the pristine material.Lithium and sodium tends to be ordered in the deintercalated materials for peculiar compositions. Nevertheless, due to the larger ionic radii of Na+ vs Li+, the repulsive interaction between sodium ions are stronger for sodium, leading to many Na+/vacancy patterns in the interslab space.Moreover, transition element orderings can occur within the (L,M)O2 slab if the difference in size is significant and if the cation ratio corresponds to a specific composition (1/3, ½, 2/3...). Then an interesting behaviour is observed as the sodium/vacancy ordering in the interslab space can be st superimposed to the cation ordering.Another original situation is also observed for cations (d2 or d3) which like to form M-M bonds. In this case, the pattering of short bond and long bond in the MO2 slab is directly related to the Na+/vacancy distribution and to the M3+/M4+ ratio.

Countering Voltage Decay, Redox Sluggishness, and Calendering Incompatibility by Near‐Zero‐Strain Interphase in Lithium‐Rich, Manganese‐Based Layered Oxide Electrodes

AbstractLithium‐rich, manganese‐based layered oxides are considered one of the most valuable cathode materials for the next generation of high‐energy density lithium‐ion batteries (LIBs) for their high specific capacity and low cost. However, their practical implementation in LIBs is hindered by the rapid voltage/capacity decay on cycling and the long‐standing contradictions between redox kinetics and volumetric energy density due to their poor calendaring compatibility. Herein, a coherent near‐zero‐strain interphase is constructed on the grain boundaries of cathode secondary particles by infusing LiAlO2 material through the reactive infiltration method (RIM). Theoretical calculations, multi‐scale characterizations, and electrochemical tests show that this coherent interphase with near‐zero‐strain feature upon electrochemical (de)lithiation inhibits volume changes of the lattice and structural degradation of cathode primary particles during cycling. More importantly, the ionically conductive LiAlO2 nanolayer infiltrated in the grain boundaries of cathode secondary particles can not only promote the rapid Li+ migration and act as a barrier to protect the material from the corrosion of the electrolyte but also effectively improve the mechanical strength of the cathode secondary particles. Collectedly, the LiAlO2‐infiltrated cathode materials display superior electrochemical cyclability, enhanced rate capability, and industrial calendaring performance, marking a significant step toward commercial implementation.

Enhanced homogeneity of electrochemical reaction via low tortuosity enabling high-voltage nickel-rich layered oxide thick-electrode

Inhomogeneous electrochemical reactions during the charging-discharging process of high-voltage nickel-rich layered oxide cathodes play a major role in cracks formation and deteriorating cyclability. Especially in thick electrodes, the severe concentration polarization aggravates the inhomogeneity and further diminishes the cycle life. In this work, a low-tortuous thick electrode of LiNi0.7Co0.1Mn0.2O2 (NCM712) is constructed by the ice-templating strategy and the effect of low tortuosity on electrochemical performance is investigated. Low-tortuous NCM712 electrode exhibits reduced concentration polarization and fast lithium-ion transport kinetics, consequently enabling superior rate capability. Furthermore, benefiting from the effective electronic and ionic transport network in low-tortuous thick electrode, NCM712 particles present homogeneous electrochemical reaction and alleviated intragranular stress, which suppresses cation mixing and cracking formation at high voltage condition. The homogeneity of electrochemical reaction in the low-tortuous thick electrode is favorable to attain the structural integrity, the robust electrolyte interface and superior cyclability. This strategy provides a new concept to homogenize the electrochemical reaction of thick nickel-rich layered oxide electrodes by low tortuosity electrode architecture design, leading to superb electrochemical performance with high energy density.

Localized introduction of zirconium in P2 sodium layered oxide electrode for high capacity sodium-ion battery

The Na0.67[Ni0.3Mn0.5Fe0.2]1-xZrxO2 (x = 0, 0.05, 0.075 and 0.1, respectively) materials composed of eco-friendly elements was synthesized via the sol-gel method. The X-ray diffraction (XRD) patterns demonstrated that all of the samples have a typical P2-type structure. The Na0.67[Ni0.3Mn0.5Fe0.2]0.95Zr0.05O2 exhibited the smaller lattice parameter a and b (a = b in P2 type), whereas the larger parameter c. The physical characterization of the materials showed that the Zr element was present in the form of zirconia and Zr doping. The pristine P2-Na0.67Ni0.3Mn0.5Fe0.2O2 delivers excellent electrochemical performance with an initial discharge specific capacity of 235.3 mA h g−1 (corresponding to 98.4% of the theoretical capacity) at a rate of 0.1 C between 1.5 and 4.3 V. The cycle performance of Na0.67[Ni0.3Mn0.5Fe0.2]0.95Zr0.05O2 is substantially improved compared with Zr free Na0.67Ni0.3Mn0.5Fe0.2O2, delivers a retention capacity increased from 40.5% to 56.2% after 100 cycles with 207.7 mA h g−1 in the 1st cycle. Combined with system analysis including the Transmission Electron Microscopy (TEM) and electrochemical methods, the better electrochemical performance can be attributed to the phase transformation suppression and the improvement of sodium diffusion kinetics brought about by the introduction of zirconium. The favorable Na storage performance of full cell with Na0.67[Ni0.3Mn0.5Fe0.2]0.95Zr0.05O2 cathode material paves the way for high capacity sodium-ion battery.

Microwave-Assisted Rapid Synthesis of NH4V4O10 Layered Oxide: A High Energy Cathode for Aqueous Rechargeable Zinc Ion Batteries.

Aqueous rechargeable zinc ion batteries (ARZIBs) have gained wide interest in recent years as prospective high power and high energy devices to meet the ever-rising commercial needs for large-scale eco-friendly energy storage applications. The advancement in the development of electrodes, especially cathodes for ARZIB, is faced with hurdles related to the shortage of host materials that support divalent zinc storage. Even the existing materials, mostly based on transition metal compounds, have limitations of poor electrochemical stability, low specific capacity, and hence apparently low specific energies. Herein, NH4V4O10 (NHVO), a layered oxide electrode material with a uniquely mixed morphology of plate and belt-like particles is synthesized by a microwave method utilizing a short reaction time (~0.5 h) for use as a high energy cathode for ARZIB applications. The remarkable electrochemical reversibility of Zn2+/H+ intercalation in this layered electrode contributes to impressive specific capacity (417 mAh g−1 at 0.25 A g−1) and high rate performance (170 mAh g−1 at 6.4 A g−1) with almost 100% Coulombic efficiencies. Further, a very high specific energy of 306 Wh Kg−1 at a specific power of 72 W Kg−1 was achieved by the ARZIB using the present NHVO cathode. The present study thus facilitates the opportunity for developing high energy ARZIB electrodes even under short reaction time to explore potential materials for safe and sustainable green energy storage devices.

Structural Aspects of P2‐Type Na0.67Mn0.6Ni0.2Li0.2O2 (MNL) Stabilization by Lithium Defects as a Cathode Material for Sodium‐Ion Batteries

AbstractA known strategy for improving the properties of layered oxide electrodes in sodium‐ion batteries is the partial substitution of transition metals by Li. Herein, the role of Li as a defect and its impact on sodium storage in P2‐Na0.67Mn0.6Ni0.2Li0.2O2 is discussed. In tandem with electrochemical studies, the electronic and atomic structure are studied using solid‐state NMR, operando XRD, and density functional theory (DFT). For the as‐synthesized material, Li is located in comparable amounts within the sodium and the transition metal oxide (TMO) layers. Desodiation leads to a redistribution of Li ions within the crystal lattice. During charging, Li ions from the Na layer first migrate to the TMO layer before reversing their course at low Na contents. There is little change in the lattice parameters during charging/discharging, indicating stabilization of the P2 structure. This leads to a solid‐solution type storage mechanism (sloping voltage profile) and hence excellent cycle life with a capacity of 110 mAh g‐1 after 100 cycles. In contrast, the Li‐free compositions Na0.67Mn0.6Ni0.4O2 and Na0.67Mn0.8Ni0.2O2 show phase transitions and a stair‐case voltage profile. The capacity is found to originate from mainly Ni3+/Ni4+ and O2‐/O2‐δ redox processes by DFT, although a small contribution from Mn4+/Mn5+ to the capacity cannot be excluded.

Integrated titanium-substituted air stable O3 sodium layered oxide electrode via a complexant assisted route for high capacity sodium-ion battery

In this work, the cathode materials with and without Ti doping were synthesized by the novel sol-gel method with n-butyl titanate as the Ti source. The Ti4+ ions were atomic-level mixed in the liquid precursor to substitute in integral [Ni0.4Mn0.4Fe0.2] site, which will maintain the optimal ratio of Ni/Mn. The X-ray diffraction (XRD) refinements demonstrated that the Ti doping suppressed the impurity formation of NiO, as well as enlarged the inter slab diastance (parameter c) for improving the Na+ diffusion coefficient and conductivity. It was confirmed by XRD patterns and the Transmission Electron Microscopy (TEM) that the Na[Ni0.4Mn0.4Fe0.2]0.95Ti0.05O2 was more stable than NaNi0.4Mn0.4Fe0.2O2 in ambient atmospheres. The cycle performance of the Na[Ni0.4Mn0.4Fe0.2O2]0.95Ti0.05O2 showed the high capacity retention of 83.8% after 200 cycles at 1.0C, while the capacity retention of the bare NaNi0.4Mn0.4Fe0.2O2 was only 69.6% under the same conditions. Moreover, the Na[Ni0.4Mn0.4Fe0.2]0.95Ti0.05O2 sample exhibited excellent discharge rate-capacities of 160.7, 132.1, 125.1, 120.9, 114.7 and 99.6 mAh•g−1 at 0.1C, 0.2C, 0.5C, 1.0C, 2.0C and 5.0C, respectively (1C = 140 mA•g−1). In addition, the ex situ XRD results showed the substitution of Ti can eliminate the detrimental and irreversible multiphase transformation of the P3 to O3 phase, which was usually observed in NaNi0.4Mn0.4Fe0.2O2 during the discharge process. It is expected that the results from present work can be used for opening new insight into the contrivance and creation of applicable transition metal oxide cathode materials for high-performance.

Recent progress in the design of anionic redox in layered oxide electrodes: A mini review

Layered cathode oxides have been attractive for next-generation high-energy-density rechargeable batteries, only that they are approaching the bottleneck of limited specific capacities based on cation redox reactions. Recently, the utilization of anion redox reaction to participate in charge compensation is an important strategy to increase the upper limit of energy density, but it faces issues such as voltage hysteresis and structure decay. In this review, we discuss the anion redox chemistry and the problems faced by such materials. Subsequently, we reviewed the recent research progress from perspectives of transition metal layer design and stacking fault design, hoping to provide a guide for the design of layered oxide cathodes.

Reversible Anionic Redox Activities in Conventional LiNi1/3 Co1/3 Mn1/3 O2 Cathodes.

Redox reactions of oxygen have been considered critical in controlling the electrochemical properties of lithium-excessive layered-oxide electrodes. However, conventional electrode materials without overlithiation remain the most practical. Typically, cationic redox reactions are believed to dominate the electrochemical processes in conventional electrodes. Herein, we show unambiguous evidence of reversible anionic redox reactions in LiNi1/3 Co1/3 Mn1/3 O2 . The typical involvement of oxygen through hybridization with transition metals is discussed, as well as the intrinsic oxygen redox process at high potentials, which is 75 % reversible during initial cycling and 63 % retained after 10 cycles. Our results clarify the reaction mechanism at high potentials in conventional layered electrodes involving both cationic and anionic reactions and indicate the potential of utilizing reversible oxygen redox reactions in conventional layered oxides for high-capacity lithium-ion batteries.

Voltage decay and redox asymmetry mitigation by reversible cation migration in lithium-rich layered oxide electrodes.

Despite the high energy density of lithium-rich layered-oxide electrodes, their real-world implementation in batteries is hindered by the substantial voltage decay on cycling. This voltage decay is widely accepted to mainly originate from progressive structural rearrangements involving irreversible transition-metal migration. As prevention of this spontaneous cation migration has proven difficult, a paradigm shift toward management of its reversibility is needed. Herein, we demonstrate that the reversibility of the cation migration of lithium-rich nickel manganese oxides can be remarkably improved by altering the oxygen stacking sequences in the layered structure and thereby dramatically reducing the voltage decay. The preeminent intra-cycle reversibility of the cation migration is experimentally visualized, and first-principles calculations reveal that an O2-type structure restricts the movements of transition metals within the Li layer, which effectively streamlines the returning migration path of the transition metals. Furthermore, we propose that the enhanced reversibility mitigates the asymmetry of the anionic redox in conventional lithium-rich electrodes, promoting the high-potential anionic reduction, thereby reducing the subsequent voltage hysteresis. Our findings demonstrate that regulating the reversibility of the cation migration is a practical strategy to reduce voltage decay and hysteresis in lithium-rich layered materials.

Improvement of Electrochemical Stability of Layered Oxide Electrodes in Na-Ion Batteries Via Control of Chemical Composition in the Interlayer Region

Layered transition metal compounds with expanded interlayer region, stabilized by structural water, often show high initial capacities but suffer from rapid capacity decay and poor rate capability in Na-ion batteries. High-temperature annealing, accompanied by phase transformation with the formation of more dense atomic structures, has been shown to improve electrochemical stability. However, the capacity of annealed materials decreases compared to their original forms. Here, we for the first time demonstrate that low-temperature annealing (260oC under vacuum) can be used to achieve enhanced electrochemical stability of high capacity Na-preintercalated bilayered vanadium oxide (δ-NaxV2O5·nH2O) nanobelts, while preserving its open layered structure with expanded interlayer region available for insertion and diffusion of a large number of electrochemically cycled Na+ ions. The mechanism of the thermally induced interlayer water loss is discussed. The improved capacity retention exhibited by low-temperature vacuum annealed δ-NaxV2O5·nH2O nanobelts is attributed to the partial removal of the structural water from the interlayer region, formation of additional bonds within the V-O bilayers, and increased stacking order of V-O bilayers. Additionally, we will show the effect of the chemical pre-intercalation of alkali (Li+, Na+, K+) and alkali-earth (Mg2+ and Ca2+) ions in the interlayer region of the bilayered vanadium oxide on electrochemical stability in Na-ion batteries. By altering the nature of the chemically preintercalated ion, interlayer spacing of the synthesized δ-MxV2O5 (M = Li, Na, K, Mg, Ca) materials was varied between 9.62 and 13.40 Å. We show that the interlayer spacing increases with the increase of the hydrated ion radius. The ion (Li+, K+, Mg2+, Ca2+) stabilization effect was investigated in Na-ion cells, with Na-preintercalated phase, δ-NaxV2O5, serving as a reference material. Our analyses indicate that cyclability and rate performance of the δ-MxV2O5 improves with increasing interlayer spacing and decreasing the ionic radius of chemically preintercalated ion. The highest initial capacity, greatest capacity retention, and highest capacity retention at higher current rates were exhibited by Mg- and Li-stabilized δ-V2O5. Low-temperature vacuum annealing ion stabilization achieved via chemical pre-intercalation synthesis approach are proposed as efficient strategies to advance electrochemical stability of the growing family of hydrated transition metal compounds used as electrodes in beyond lithium-ion batteries.