Lithium-rich Oxide Research Articles

Advancing the Performance of Lithium-Rich Oxides in Concert with Inherent Complexities: Domain-Selective Substitutions

Advancing the Performance of Lithium-Rich Oxides in Concert with Inherent Complexities: Domain-Selective Substitutions

Phase segregation and nanoconfined fluid O2 in a lithium-rich oxide cathode

Lithium-rich oxide cathodes lose energy density during cycling due to atomic disordering and nanoscale structural rearrangements, which are both challenging to characterize. Here we resolve the kinetics and thermodynamics of these processes in an exemplar layered Li-rich (Li1.2–xMn0.8O2) cathode using a combined approach of ab initio molecular dynamics and cluster expansion-based Monte Carlo simulations. We identify a kinetically accessible and thermodynamically favourable mechanism to form O2 molecules in the bulk, involving Mn migration and driven by interlayer oxygen dimerization. At the top of charge, the bulk structure locally phase segregates into MnO2-rich regions and Mn-deficient nanovoids, which contain O2 molecules as a nanoconfined fluid. These nanovoids are connected in a percolating network, potentially allowing long-range oxygen transport and linking bulk O2 formation to surface O2 loss. These insights highlight the importance of developing strategies to kinetically stabilize the bulk structure of Li-rich O-redox cathodes to maintain their high energy densities.

The role of PrPO4 in improving the electrochemical performance of cobalt-free Lithium-rich oxide cathode

The utilization of lithium-rich layered oxides (LLOs) materials shows promising possibilities for the innovation of high-capacity Li-ion batteries with enhanced energy density. However, their practical applications are limited by continuous voltage decay, inferior cycling stability, and poor rate capability. In this work, a novel doping strategy is proposed, where PrPO4 is introduced during the high-temperature solid-state reaction to prepare Co-free Li-rich layered oxides. It is found that other than as a dopant, PrPO4 can activate Li2MnO3 to form well-distributed Pr0.96Mn0.982O3 and Li3PO4 in LLOs particles, which availably suppresses the phase transition. The obtained material increases the initial coulombic efficiency (ICE) from 75.8% to 84.1%, and improves capacity retention from 74.6% to 90.9% compared with the pristine material. Meanwhile, the average voltage decay decreases from 2.33 mV/cycle to 1.25 mV/cycle over 200 cycles. This work provides valuable insights into the development of LLOs using rare-earth phosphate, offering valuable knowledge for further advancements in this field.

Interface Engineering via Constructing Enhanced Ligand Enables Highly Stable Li‐Rich Layered Oxide Cathode

AbstractHigh‐energy‐density and cost‐effective lithium‐rich oxides (LRO) are considered as the promising cathode materials for the next‐generation lithium‐ion batteries . Nevertheless, the elevated cut‐off voltage and the complex interface interactions have presented significant challenges that can lead to material degradation. Specifically, the inevitable release of lattice oxygen and the highly reactive interface‐driven irreversible migration of transition metal (TM) ions in LRO make the construction of a robust interface extremely important. Herein, an effective and efficient coating approach is applied to stabilize the interface structure of LRO by introducing a coordination bond between the strong ligand of polyurethane (PU) and the surface of LRO particles. This functional coating stabilizes the crystal field stabilization energies of LRO by acting as a strong ligand in spectrochemistry to form a coordination bond with Mn4+ in Li2MnO3 at high voltage. Consequently, irreversible oxygen release and TM ions migration are greatly inhibited. Overall, the LRO‐PU cathode exhibits superior electrochemical cyclability with a retention of 80.0% at 1C after 300 cycles and enhanced rate capability with a retention of 80.9% at 0.1C after rate cycles, marking a significant step toward commercial implementation.

Ring-shaped all manganese-based lithium-rich oxide cathode with high performance and stability via biomineralization method

As free from cobalt and nickel, all manganese-based lithium-rich layered oxides (AMLROs) are promising cathode materials with low cost and high theoretical energy density. This study introduced yeast as a biomineralization template to regulate the crystallization and growth of precursors at the molecular level. The mechanism of structural evolution was investigated in detail, offering a new approach to control the morphology of lithium-rich materials. The resulting AMLRO-54 exhibited a micro-nano composite ring-shaped structure with particle size around 2 μm. The unique hierarchical particles provided large flexible volume, leading to superior structural stability and high rate capability. The reversible capacity of ring-shaped AMLRO-54, without any other modifications, was 274.1 mAh·g−1 at 0.1 C. Once extra carbon material was added to improve the inferior electronic conductivity, the initial capacity of AMLRO-54 at 1 C reached 242.9 mAh·g−1 with a retention rate of 90.9 % after 300 cycles (221.0 mAh·g−1). Furthermore, this cobalt and nickel-free cathode material significantly mitigates material costs and environmental hazards, thereby promoting the development of lithium-ion batteries in the future.

Insights into Lithium-rich Oxides from Synthesis and Characterization Studies

Insights into Lithium-rich Oxides from Synthesis and Characterization Studies

Nanomaterial coating for layered lithium rich transition metal oxide cathode for lithium-ion battery

Nanomaterial coating for layered lithium rich transition metal oxide cathode for lithium-ion battery

Self-constructing a lattice-oxygen-stabilized interface in Li-rich cathodes to enable high-energy all-solid-state batteries

A lattice-oxygen-stabilized interface is formed in situ by the interaction of indium and oxidized lattice oxygen in the interface of Li2RuO3 (LRO) and Li3InCl6 (LIC), mitigating the irreversible lattice oxygen loss and stabilizing the surface structure.

Entropic Stabilization in Lithium Rich Transition Metal Oxide Cathodes

It is well known that lithium rich transition metal oxide cathodes (LRM) experience voltage fade and capacity loss over the course of cycling, and it is generally known that these are a result of the LRM materials’ general instability 1–7. However, the mechanisms behind these losses are still unknown, due in large part to the structural ambiguity and controversy associated with the LRM material structure. In this perspective we consider the role entropy plays in LRM materials’ structural stability and electrochemical properties. With this mind set we argue that due to their metastability LRM cathodes’ structure and properties are not synthesis agnostic, and therefore establishment of consistent synthetic procedures is of paramount importance. We also propose that LRM materials could be categorized as entropically stabilized oxides through exploring their configurational entropies, phase behaviors, and thermal responses. The entropic stabilization of LRM materials is also found to be consistent with the ordering behaviors of LRM cathode transitional metal layers, with this ordering presenting both compositional, thermal, and electrochemical dependencies. The impact of these behaviors on the redox and electrochemical structure and activation of LRM materials is also explored. Finally, we seek to put these findings into the context of the wider battery field. Fell, C. R. et al. Correlation Between Oxygen Vacancy, Microstrain, and Cation Distribution in Lithium-Excess Layered Oxides During the First Electrochemical Cycle. Chem. Mater. 1621–1629 (2013) doi:10.1021/cm4000119.Lu, Z., Beaulieu, L. Y., Donaberger, R. A., Thomas, C. L. & Dahn, J. R. Synthesis, Structure, and Electrochemical Behavior of Li [Ni x Li(1/2-2x/3) Mn(2/3-x/3)]O2. J. Electrochem. Soc. 149, A778–A791 (2002).Wu, Y. & Manthiram, A. High Capacity, Surface-Modified Layered Li†Li„1−x.../3Mn„2−x.../3Nix/3Cox/3‡O2 Cathodes with Low Irreversible Capacity Loss. Electrochem. Solid-State Lett. 9, A221–A224 (2006).Dupré, N., Cuisinier, M., Legall, E., War, D. & Guyomard, D. Contribution of the oxygen extracted from overlithiated layered oxides at high potential to the formation of the interphase. J. Power Sources 299, 231–240 (2015).Jarvis, K. A. et al. Formation and effect of orientation domains in layered oxide cathodes of lithium-ion batteries. Acta Mater. 108, 264–270 (2016).Jiang, M., Key, B., Meng, Y. S. & Grey, C. P. Electrochemical and Structural Study of the Layered, ‘Li-Excess’; Lithium-Ion Battery Electrode Material Li[Li 1/9 Ni 1/3 Mn 5/9 ]O 2. Chem. Mater. 21, 2733–2745 (2009).Hy, S. et al. Performance and design considerations for lithium excess layered oxide positive electrode materials for lithium ion batteries. Energy Environ. Sci. 9, 1931–1954 (2016).

Doping Strategy to Improve the Electrochemical Behavior of Lithium Rich Transition Metal Oxides As Cathodes for Lithium-Ion Batteries

Lithium-rich transition metal oxides are considered a promising cathodic solutions in Li-ion batteries to meet the growing energetic demand, thanks to their high specific capacity and operational voltage [1-2]. Li-rich layered materials have a general stoichiometry Li1+xTM1-xO2, in which TM is a blend of transition metals, as Ni, Mn, Co [2]. They stand out due to their high lithium concentration and specific capacity [1-2]. The higher capacity of Lithium-Rich can be attributed to the specific anionic redox reaction in the bulk at above 4.5 V. Nevertheless, large irreversible capacity loss in the first cycle, poor rate capability, mean working potential decay upon cycling and cobalt content are still major drawbacks that are hindering commercialization. In order to make these materials up scalable to industrial production, it is important to consider the reduction of costs and the toxicity of raw materials, in particular cobalt. Cobalt reduction has been identified as major driver to improve the environmental benignity of batteries and the sustainability of the overall production-consumption-recycling lifecycle. Several efforts to reduce these problems have been made, including the development of different synthetic strategies, doping and surface modification. The most, widely explored, chemical strategy to mitigate the voltage decay and structural degradation in Lithium Rich cathodes is the doping. Elemental doping can be divided into cation and anion doping. As an example, incorporation of redox inactive metals, such as Al, Zr, Ti, has been proposed in order to stabilize the lattice as well as the partial replacement of lithium ions with other alkali cations, e.g. K and Na; or doping the oxygen anion sublattice. In this communication, we present our doping approaches. In particular, the simultaneous replacement of cobalt in the layered structure with aluminum and lithium (over-lithiation). Moreover, we present over-lithiated Co-free materials where the introduction of different amount of iron has been investigated. The characterization of these novel layered materials is reported in terms of composition, structure, morphology and electrochemical performances. These approaches can be applied as a strategy to mitigate the voltage decay and reduce the Cobalt content.[1] Ji, X. et al. Journal of Power Sources 487, (2021).[2] Zhao, S. et al. Angewandte Chemie - International Edition 60, 2208–2220 (2021).

Monitoring the State of Health (SOH) of Green Batteries (GreenBat)

Here we focus on the study of state of health monitoring of secondary batteries with advanced “green” formulations. European recycle map on battery energy storage plans to replace positive electrodes consisting of cobalt (Co) and fluorinated (F) graphite-based negative electrodes constituents with environmentally sustainable alternatives. Recently, "green formulations" was validated; in particular, recent trends suggest the use of electrodes based on silicon (Si), Co-free manganites (LiMnO2) aqueous soluble binders and fluorine-free electrolytes [1]. Our aims are to describe the health and the degradation of the cells with electrochemical techniques and to describe the chemical and morphological changes occurring during the battery cycling, through spectroscopies (Raman and IR) operating in parallel with impedance analysis. These experimental data will be integrated together in a multiblock dataset, which will constitute the basis for chemometric processing. The purpose of this chemometric modelling is to correlate SOH evolution to the chemical and physical state of the battery [1]. Here we illustrate the analysis of SOH of two different pouch cells formulation constituted by LTO (Lithium-Titanate) as anode, LFP (Lithium-Iron-Phosphate) as cathode and the LP30 electrolyte (EC:DMC 1:1 and LiPF6 1M); the second formulation is constituted by a thin film layer of commercial Li metal (purity of 99.7%) as anode, LFP as cathode and an ethers based formulation as electrolyte. After formation cycles (CC-CV), the cells have been submitted to aging tests. The different operating conditions are chosen with an Experimental Design (ED) and supported by a PCA analysis. The PCA analysis it was used to choose the operating parameters for the subsequent aging experiments. Is illustrated also the analysis of SOH of a coin cell formulation consisted by a LRLO (Lithium Rich Layer Oxide) as anode, commercial Li metal layer as cathode and LP30 additive with a ionic liquid (IL) as electrolyte. Turning to the chemometric modelling, as a starting point we verified the ability of PLS regression applied to the voltage profiles during charge cycles to estimate the SOH of a benchmark dataset by Lin et al. [1] References [1] M. Lin,D. Wu, Journal of Power Sources, 2022, 518, 230774. Figure 1

4d Lithium-Rich Cathode System Reinvestigated with Electron Paramagnetic Resonance: Correlation between Ionicity, Oxygen Dimers, and Molecular O2.

Layered lithium-rich (Li-rich) oxide cathodes with additional capacity contribution via oxygen redox are promising high energy density cathodes for next generation Li-ion batteries. However, the chemical states of the oxidized oxygen in charged materials are under fierce debate, including the O2- with stable electron holes, O-O dimer (O2)n- (n > 0), molecular O2, and oxygen π redox. Here, we show using electron paramagnetic resonance (EPR) spectroscopy that in the 4d Li-rich ruthenate compounds, Li2Ru0.75Sn0.25O3 and Li2Ru0.5Sn0.5O3, strong covalency between 4d transition metal and oxygen can inhibit the formation of trapped molecular O2 but not suppress the formation of O-O dimer. As the covalent bond of Ru-O weakens and the ionic bond Sn-O becomes dominant in Li2Ru0.25Sn0.75O3, (O2)- will detach from Sn4+, eventually leading to the formation of trapped molecular O2 during the deep oxygen redox. We propose two possible evolution paths of oxidized oxygen as (1) oxygen electron holes → Ru-(O2)m- (m > 1) → Ru-(O2)- or (2) oxygen electron holes → Sn-(O2)m- (m > 1) → Sn-(O2)- → O2, and the species to which they will evolve are related to which metal (O2)- bonds to and whether the ionicity dominates.

Prominent Selection Strategies for Metal Cathode Materials in Lithium-Ion Batteries

Lithium-ion batteries (LIBs) emerge as a substitute for traditional fossil fuels and become a dominating power source in portable electronics and electric vehicle markets. Recent research on improving the performance of lithium-ion batteries involves better battery lifetime, power capacity, and specific energy by the innovation of new anodes, cathodes, and nonaqueous electrolytes. However, the cathode materials are the bottleneck in the research process due to their lower capacity, which becomes the focus of development. This review presents an outlook on lithium-ion technology by introducing its basic structure and mechanism, examining four structures of LIBs, namely lithium-rich layered oxides, lithium-manganese-rich layered oxides, lithium-ion-phosphate and spinel lithium-rich oxide, as well as comparing their performances and practical use.

Oxygen redox chemistry in lithium-rich cathode materials for Li-ion batteries: Understanding from atomic structure to nano-engineering

Lithium-rich oxide compounds have been recognized as promising cathode materials for high performance Li-ion batteries, owing to their high specific capacity. However, it remains a great challenge to achieve the fully reversible anionic redox reactions to realize high capacity, high stability, and low voltage hysteresis for lithium-rich cathode materials. Therefore, it is critically important to comprehensively understand and control the anionic redox chemistry of lithium-rich cathode materials, including atomic structure design, and nano-scale materials engineering technologies. Herein, we summarize the recent research progress of lithium-rich cathode materials with a focus on redox chemistry. Particularly, we highlight the oxygen-based redox reactions in lithium-rich metal oxides, with critical views of designing next generation oxygen redox lithium cathode materials. Furthermore, we purposed the most promising strategies for improving the performances of lithium-rich cathode materials with a technology-spectrum from the atomic scale to nano-scale.

Effect of compaction pressure on electrochemical performance of layered lithium-rich oxide

Lithium-rich oxide cathode material focuses the attention of many researchers due to its excellent electrochemical performance for lithium–ion batteries. Further improvement on the performance with a strong operability approach can be beneficial to its industrialization and commercialization. In this work, the effect of powder compaction pressure in sintering process on the electrochemical performance of Li[Formula: see text]Mn[Formula: see text]Ni[Formula: see text]Co[Formula: see text]O2 cathode material is investigated. Four cathode materials under different powder compaction pressure are synthesized by sol–gel method. The XRD analysis results reveal their consistency on the crystal structure. But there is a slight difference on particle size and microstructure found by SEM analysis. Electrochemical tests show that a cathode material under medium compaction pressure exhibits the best performance with a discharge capacity of 170.3 mAh⋅g[Formula: see text] at the rate of 200 mA⋅g[Formula: see text] with 89.35% retention after 100 cycles. This work reveals that the powder compaction pressure does have influence on the cycle and rate performance and this relation is not proportional and linear.

Core-shell Architecture Strategy of Improving the Electrochemical Performance of the Li-rich Layered Oxides: A Review

Lithium-ion battery (LIB) serves as power supply for suitable electronics and stationary electrical systems (storage) as a result of their outstanding combination of extraordinary densities (power and energy). The cathode constitutes an integral part of LIBs and its property determines the performance of the battery. The layered lithium-rich oxide (LLO) is unique and favourable cathode materials for LIBs as a result of its high capacity compared to conventional cathode materials such as LiNiO2 etc. However, they demonstrate several performance limitations such as low first cycle efficiency and poor cycling stability thus, limiting their practical applications. Therefore, this review discussed a core-shell architecture strategy of enhancing the electrochemical performance of the LLOs materials for LIBs.

Surface Effects of Quench Methodology on Lithium Rich Nickel Manganese Oxide Cathode Particles

Our investigation found that rapid cooling, through use of a water quench, of layered lithium rich nickel manganese oxide (LLRNMO) cathodes, post 900 °C calcination, resulted in cathode materials with significantly improved electrochemical performance and more homogenous physio-structural properties near the surfaces. Our investigation was conducted on LLRNMO from the Li[NixLi(1/3-2x/3)Mn(2/3-x/3)]O2 compositional series, where x = 0.25. Our material was prepared using a hybrid sol-gel route where the post 900 °C cooling step was varied between the two extremes, rapid quenching through water immersion (sample Wq), and slow natural oven cooling (sample Oc). Surface analysis of these samples was conducted before and after repeated galvanostatic-static constant-current potential limited (GCPL) cycling of coin cells with cathodes made of these active materials to elucidate any electrochemical effects that could arise from the physio-structural differences between the samples. Surface analysis was conducted using high resolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy (STEM), energy dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). The rapidly quenched Wq samples were found to have higher specific capacities, higher average discharge voltages, greater cycle stability, and greater voltage stability when compared to the Oc samples. This is consistent with one of our previous investigations.1 Surface studies of the samples revealed that the pristine Oc samples had evidence of phase segregation between the nickel poor bulk phase and a nickel rich surface phase. These two phases were reminiscent of a core/shell architecture. Surface analysis conducted after the course of cycling suggested that the concentration of transition metals homogenized over the course of cycling, resulting in less distinction between the surface and bulk phases, as well as the nucleation of defect phases. These behaviors of the Oc samples are in large contrast to the Wq samples’ where the surface and bulk phases were isostructural with more homogenous concentrations of transition metals. These data suggest that more rapidly quenched samples see increased stabilization of the meta-stable R-3m phase resulting in the reported superior electrochemical properties. S. Burke and J. F. Whitacre, J. Electrochem. Soc., 167, 160518 (2020). Figure 1

Lithium-Rich O2-Type Li0.66[Li0.22Ru0.78]O2 Positive Electrode Material

Increasing the energy density of lithium-ion batteries is an important step towards flexible electricity supply, which can be achieved by developing large-capacity positive electrodes. Lithium-rich oxides have been a longstanding research target because of their large capacity involving extra oxygen-redox reactions. In this work, we report the synthesis, electrochemical properties, electronic structure, and structural evolution of O2-type lithium-rich layered oxide Li1.22‒x Ru0.78O2. A robust Ru‒O layered framework without Ru migration allows for unveiling the solid-state electrochemistry of O2-type lithium-rich layered oxides with possibility of a large yet stable extra capacity for oxygen-redox reaction. Using a combination of X-ray photoelectron spectroscopy, X-ray absorption/emission spectroscopy, and in situ/ex situ X-ray diffraction, we clarified that O2-Li1.22‒x Ru0.78O2 delivers a large capacity of 200 mAh g‒1 in association with Ru5+/Ru4+ and Ru4+/Ru3+ two-electron redox reactions under a solid-solution process, but with no contribution from the extra oxygen-redox reaction.

Chemically induced delithiation and phase change of lithium rich nickel manganese oxides

In this study, Li[Ni.25Li.167Mn.583]O2 (LLRNMO) was exposed to acidic solutions of H3PO4, H2SO4, HCl, and HNO3 in an attempt to chemically motivated the phase transformation analogous to the that encountered during electrochemically-driven delithiation. Powder X-ray diffraction and electrochemical data provide evidence of delithiation similar to a low cell potential charge (sub 4.5 V), but the data were not consistent with the phase change induced by the initial high cell potential (>4.5 V) charge. Repeated full cycling revealed that acidic treatments reduced sample capacity and cell potential. XRF and SEM data suggest the effects of acid treatment are not universal and are dependent on the acid used. To the best of our knowledge, this study marks the first time that a lithium-excess cobalt-free cathode was exposed to acidic solutions for this purpose. Our results demonstrate that these chemically induced phase transformations are a poor substitute for the electrochemically induced phase transformation. The possible reasons and consequences of this are discussed.

Ordered Oxygen Vacancies in the Lithium-Rich Oxide Li4CuSbO5.5, a Triclinic Structure Type Derived from the Cubic Rocksalt Structure.

Li-rich rocksalt oxides are promising candidates as high-energy density cathode materials for next-generation Li-ion batteries because they present extremely diverse structures and compositions. Most reported materials in this family contain as many cations as anions, a characteristic of the ideal cubic closed-packed rocksalt composition. In this work, a new rocksalt-derived structure type is stabilized by selecting divalent Cu and pentavalent Sb cations to favor the formation of oxygen vacancies during synthesis. The structure and composition of the oxygen-deficient Li4CuSbO5.5□0.5 phase is characterized by combining X-ray and neutron diffraction, ICP-OES, XAS, and magnetometry measurements. The ordering of cations and oxygen vacancies is discussed in comparison with the related Li2CuO2□1 and Li5SbO5□1 phases. The electrochemical properties of this material are presented, with only 0.55 Li+ extracted upon oxidation, corresponding to a limited utilization of cationic and/or anionic redox, whereas more than 2 Li+ ions can be reversibly inserted upon reduction to 1 V vs Li+/Li, a large capacity attributed to a conversion reaction and the reduction of Cu2+ to Cu0. Control of the formation of oxygen vacancies in Li-rich rocksalt oxides by selecting appropriate cations and synthesis conditions affords a new route for tuning the electrochemical properties of cathode materials for Li-ion batteries. Furthermore, the development of material models of the required level of detail to predict phase diagrams and electrochemical properties, including oxygen release in Li-rich rocksalt oxides, still relies on the accurate prediction of crystal structures. Experimental identification of new accessible structure types stabilized by oxygen vacancies represents a valuable step forward in the development of predictive models.