Mn-rich Layered Oxides Research Articles

Redox Couple Strategy for Improving the Oxygen Redox Activity and Reversibility of Li- and Mn-Rich Cathode Materials.

The specific capacity of Li- and Mn-rich layered oxide (LMROs) cathodes can be enhanced by the oxidation of lattice oxygen at high voltages. Nevertheless, an irreversible oxygen loss emerges with cycling, which triggers interlocking surface/interface issues and results in the fast deterioration of cycling performance. Herein, we prepare a surface modified LMRO electrode by one step doctor-blade casting and introducing a benzoquinone species DBBQ redox couple. The electrochemical test shows that the DBBQ-modified electrode has a high reversible capacity (>320 mAh g-1) and excellent rate performance, while the cyclic stability has been significantly improved as well. The capacity retention reaches as high as 93.3% after 500 cycles at 1 C. Mechanism analysis shows that DBBQ can not only play a redox couple in LMROs which achieves the adsorption and reduction of surface oxygen gas but also significantly enhance anionic redox in the bulk, thus realizing extraordinary capacity.

Active–Inactive Molten Salt Synthesis of Li- and Mn-Rich Layered Oxide Single Crystals as Cathode Materials for All-Solid-State Batteries

Active–Inactive Molten Salt Synthesis of Li- and Mn-Rich Layered Oxide Single Crystals as Cathode Materials for All-Solid-State Batteries

Bridging the Gap: Scaling up Processes for the Development of Li-Rich Mn-Rich Layered Oxides

As the global demand for more powerful and long-lasting energy storage solutions continues to grow, Li-rich Mn-rich layered oxides (LMR) emerges as a promising class of next-generation cathode materials for lithium-ion batteries. The LMR material stands out due to its impressive electrochemical specific capacity, surpassing 280 mAh g–1, along with a high discharge voltage exceeding 3.5 V. It also boasts a remarkable specific energy density close to 1000 Wh kg–1, all while maintaining a relatively lower cost.Current synthesis methods often rely on batch coprecipitation reactions followed by the calcination of precipitated Mn-rich precursors. However, the inherent challenges of batch reactions, particularly in terms of reproducibility and quality, prompt the exploration of more sophisticated approaches. Moreover, the transition from benchtop experiments to large-scale production introduces a distinct set of challenges. Parameters that work seamlessly on a smaller scale may not translate as effectively when producing the material at the kilogram scale. This scaling-up process involves navigating complexities such as chemical handling risks, and challenges related to reaction heat transfer and mixing efficiency. These factors collectively underscore the difficulties in achieving precise control over critical precursor characteristics, including primary and secondary particle size, morphology, tap density, and stoichiometry.In response to these challenges, this presentation will discuss an innovative approach. High-quality Li-rich Mn-rich materials are synthesized using continuous coprecipitation, facilitated by a pre-pilot scale Taylor Vortex Reactor (TVR) at the Materials Engineering Research Facility (MERF) in Argonne National Lab (ANL). This emerging synthesis technology offers a scalable solution for the production of high-quality cathode materials. This presentation will delve into the intricacies of the synthesis process, providing valuable insights into the relationship between the characteristics of the synthesized LMR precursors and their subsequent impact on cathode performance.

Nitrogen-based redox couple regulated anionic redox to long-term cycling stability of Li and Mn-rich layered oxide cathode for Li-ion batteries

Lithium and manganese-rich layered oxides (LMROs) have attracted extensive attention and are promising cathode materials for next-generation lithium ion batteries due to their high capacities and high energy densities. However, LMRO cathode suffers from severe capacity and voltage fading originating from irreversible surface oxygen evolution. Herein, we propose a facile redox couple strategy by introducing nitroxyl radicals species to regulate the surface anionic redox reaction of LMRO cathode. Differential electrochemical mass spectroscopy, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy analyses demonstrate that during charge process, the peroxide ion O22− on the surface generated from the oxidation of lattice O2− could be reduced back to stable O2− by redox couple in time, thus avoiding oxygen evolution and structure degradation, as well as enhancing bulk oxygen redox activity. The enhanced LMRO electrode delivers a high capacity of 220.3 mAh g−1 at 1 C. An excellent cycling stability with a capacity retention of 94.4 % is achieved after 500 cycles, as well as a suppressed voltage decay with only 1.12 mV per cycle.

Cu-N Synergism Regulation to Enhance Anionic Redox Reversibility and Activity of Li- and Mn-Rich Layered Oxides Cathode.

Anionic redox chemistry enables extraordinary capacity for Li- and Mn-rich layered oxides (LMROs) cathodes. Unfortunately, irreversible surface oxygen evolution evokes the pernicious phase transition, structural deterioration, and severe electrode-electrolyte interface side reaction with element dissolution, resulting in fast capacity and voltage fading of LMROs during cycling and hindering its commercialization. Herein, a redox couple strategy is proposed by utilizing copper phthalocyanine (CuPc) to address the irreversibility of anionic redox. The Cu-N synergistic effect of CuPc could not only inhibit surface oxygen evolution by reducing the peroxide ion O2 2- back to lattice oxygen O2-, but also enhance the reaction activity and reversibility of anionic redox in bulk to achieve a higher capacity and cycling stability. Moreover, the CuPc strategy suppresses the interface side reaction and induces the forming of a uniform and robust LiF-rich cathode electrolyte, interphase (CEI) to significantly eliminate transition metal dissolution. As a result, the CuPc-enhanced LMRO cathode shows superb cycling performance with a capacity retention of 95.0% after 500 long-term cycles. This study sheds light on the great effect of N-based redox couple to regulate anionic redox behavior and promote the development of high energy density and high stability LMROs cathode.

Sb-Doped Biphasic P2/O3-Type Mn-Rich Layered Oxide Cathode Material for High-Performance Sodium-Ion Batteries.

Mn-rich P2-type layered oxide cathode materials suffer from severe capacity loss caused by detrimental phase transition and transition metal dissolution, making their implementation difficult in large-scale sodium-ion battery applications. Herein, we introduced a high-valent Sb5+ substitution, leading to a biphasic P2/O3 cathode that suppresses the P2-O2 phase transformation in the high-voltage condition attributed to the stronger Sb-O covalency that introduces extra electrons to the O atom, reducing oxygen loss from the lattices and improving structural stability, as confirmed by first-principle calculations. Besides, the enhanced Na+ diffusion kinetics and thermodynamics in the modified sample are associated with the enlarged lattice parameters. As a result, the proposed cathode delivers a discharge capacity of 142.6 mAh g-1 at 0.1C between 1.5 and 4.3 V and excellent performance at a high mass loading of 8 mg cm3 with a specific capacity of 131 mAh g-1 at 0.2C. Furthermore, it also possesses remarkable rate capability (90.3 mAh g-1 at 5C), specifying its practicality in high-energy-density sodium-ion batteries. Hence, this work provides insights into incorporating high-valent dopants for high-performance Mn-rich cathodes.

Strain-modulated Mn-rich layered oxide enables highly stable potassium-ion batteries

Mn-rich layered oxides show great promise as cathode materials for potassium-ion batteries due to their high capacity and cost-effectiveness. However, internal structural strain and irreversible phase transitions caused by Jahn-Teller distortion affect their cycling stability. Here, we present an efficient strategy to concurrently modulate the internal strain and suppress the irreversible phase transition in Mn-rich cathodes by incorporating amounts of zinc (Zn) ions into the transition metal layers. The substituted Zn serves to regulate local chemistry, thereby mitigating octahedral distortion in Mn-O bonds, relieving the strain between layers, and reducing the occurrence of P3-O3 phase transition under high voltages. These findings are supported by EXAFS, in situ X-ray diffraction, advanced transmission electron microscopy, electron tomography, and DFT simulations. The low-strain K0.5Mn0.8Co0.1Zn0.1O2 electrode exhibits a high reversible capacity retention about ∼90 % (105 mAh g−1 at 100 mA g−1), exceptional rate performance in the voltage of 1.5 ∼ 3.9 V, and a substantial capacity retention after 500 cycles. This strain-relieved approach broadens the scope of lattice engineering by addressing internal strain concerns and mitigating the strain associated with potassium (de)intercalation, thereby having potential to advance the development of stable cathodes for PIBs.

Beneficial Effects of Oxide-Based Additives on Li-and Mn-rich Cathode Active Materials

Li- and Mn-rich layered oxides such as Li1.14(Ni0.26Co0.14Mn0.60)0.86O2 (LMR-NCM) are potential next-generation cathode active materials (CAMs) for lithium ion-batteries, promising an increased energy density at lower materials costs compared to state-of-the-art CAMs. However, its commercial viability is still inhibited by its strong gassing, poor cycling stability, and voltage fading, so various approaches such as post-treatments or additives are being investigated. Here, it will be shown that the cycling performance of LMR-NCM//graphite coin-cells is drastically improved when assembled with 300 °C dried glassfiber (GF) separators (“GF-cells”) compared to cells with Celgard (CG) separators dried at 70 °C (“CG-cells”). The origin of this phenomenon is investigated by online electrochemical mass spectrometry (OEMS), TGA-MS, water absorption, and XPS measurements. These reveal that the superior performance of the GF-cells can be ascribed to the bulk water absorption capability of the 300 °C dried glassfiber material as well as its ability to scavenge HF, whereby H2O and HF are produced by the (electro)chemical oxidation of the electrolyte and the decomposition of the LiPF6 salt. Similar performance enhancements can be observed for 300 °C dried SiO2 nanoparticles added to the LMR-NCM cathodes or for an HF/H+ scavenging electrolyte additive.

Multi-strategies interface and structure design of Li- and Mn-rich layered oxide for all-solid-state lithium batteries

Li- and Mn-rich layered oxide (LMRO) cathode materials is highly potential for next generation lithium-ion batteries as its extremely high energy density. However, the oxygen release and the interfacial side reactions against liquid electrolytes cause severe capacity fading and their practical applications are highly impeded. Herein, all-solid-state lithium-ion batteries (ASSLIBs) are demonstrated to be a promising solution towards practical application of LMROs. For the sulfide electrolyte of Li6PS5Cl, a highly compatible interface of LMRO to the electrolyte can be constructed with extra content of Li2MnO3 in LMRO, which prevents significantly side reaction between the LMRO and electrolyte. Moreover, the Li6PS5Cl electrolyte can provide S2-/SO32- redox couple to suppress the oxygen release of LMROs. Combining a further modification in composition with a few amounts of the LiNiO2, the ionic and electronic conductivities of LMRO are evidently improved, where the highly compatible interface is preserved. As results, a superiorly high capacity of 256 mAh g−1 and an energy density of 874 Wh kg−1 at 0.1 C, meanwhile the superior capacity retention as high as 87% for 1000 cycles at 0.5 C are achieved for ASSLIBs. The result is hopefully of great helpful on realizing the practical applications of LMROs in sulfide-based ASSLIBs.

Microwave-assisted synthesis of Co-free Li[Li0.2Ni0.2Mn0.6]O2 cathodes with a spinel-layered coherent structure for high-power Li-ion batteries.

Li- and Mn-rich layered oxides (LMLOs) are regarded as the most promising cathode materials for Li-ion batteries (LIBs), but they suffer from poor rate capability. Herein, a promising and practical method (i.e. a hydroxide coprecipitation method in combination with a microwave heating process) is developed to controllably synthesize cobalt-free Li[Li0.2Ni0.2Mn0.6]O2 with a layered/spinel heterostructure (LLNMO-LS). The cathode made of the LLNMO-LS delivers an excellent electrochemical performance, demonstrating a discharge capacity of 147 mA h g-1 at 10C.

Minimizing ion/electron pathways through ultrathin conformal holey graphene encapsulation in Li- and Mn-rich layered oxide cathodes for high-performance lithium-ion batteries

PEI/holey graphene encapsulation applied thinly and uniformly to LMR cathode surfaces enhances electrical conductivity, facilitates lithium-ion diffusion, and acts as a protective layer, demonstrating excellent electrochemical performance.

Rapid preparation of cobalt-free lithium rich cathode materials with layered structure and excellent performance via capillary microreactors

High voltage and high energy density cathode materials are the future development trend of power batteries. Li-and Mn-rich layered oxide (LMR) materials exhibit high capacity, low cost, and environmental friendliness, making them a promising cathode material for the next generation of lithium-ion batteries. In this study, a continuous-flow process for rapid co-precipitation synthesis of LMR precursor (Mn0.75Ni0.25CO3) in capillary microreactors was developed. Due to the good mixing characteristics of the microreactor (tm=54 ms), Mn0.75Ni0.25CO3 displays a complete spherical morphology and uniform elemental distribution without adding any complexing agent during the synthesis. The reaction time can be controlled within 11.78 s. The prepared Li1.2Mn0.6Ni0.2O2 (LMR) cathode exhibits excellent properties with a high initial discharge capacity of 266.52 mAh•g−1 at 0.1C and a superior capacity retention of 93.7 % after 200 cycles at 1C. This work demonstrates that microfluidic technology presents a viable and promising approach for quickly producing lithium battery cathode precursors.

Regulating Anionic Redox via Mg Substitution in Mn-Rich Layered Oxide Cathodes Enabling High Electrochemical Stability for Sodium-Ion Batteries.

With the limited resources and high cost of lithium-ion batteries (LIBs) and the ever-increasing market demands, sodium-ion batteries (SIBs) gain much interest due to their economical sustainability, and similar chemistry and manufacturing processes to LIBs. As cathodes play a vital role in determining the energy density of SIBs, Mn-based layered oxides are promising cathodes due to their low cost, environmental friendliness, and high theoretical capacity. However, the main challenge is structural instability upon cycling at high voltage. Herein, Mg is introduced into the P2-type Na0.62 Ni0.25 Mn0.75 O2 cathode to enhance electrochemical stability. By combining electrochemical testing and material characterizations, it is found that substituting 10 mol% Mg can effectively alleviate the P2-O2 phase transition, Jahn-Teller distortion, and irreversible oxygen redox. Moreover, structural integrity is greatly improved. These lead to enhanced electrochemical performances. With the optimized sample, a remarkable capacity retention of 92% in the half cell after 100 cycles and 95% in the full cell after 170 cycles can be achieved. Altogether, this work provides an alternative way to stabilize P2-type Mn-based layer oxide cathodes, which in turn, put forward the development of this material for the next-generation SIBs.

Improving the Long-term Cycle Performance of xLi2MnO3·(1-x)LiMeO2/Li4Ti5O12 Cells via Prelithiation and Electrolyte Engineering

Toward the development of high energy density and long lifetime batteries for behind-the-meter storage (BTMS) applications, Li- and Mn-rich layered oxide cathode (xLi2MnO3·(1-x)LiMeO2, Me = Ni, Mn, and etc., LMR-NM) and Li4Ti5O12 (LTO) anode system was examined. To mitigate the major degradation mechanisms at each electrode (i.e., loss of Li inventory (LLI) at the anode and transition metal dissolution and oxygen release at the cathode), two approaches were taken—prelithiating the LTO electrode and varying the electrolyte solvent compositions. The effect of prelithiation and electrolyte engineering on the long-term cycle performance of LMR-NM/LTO cells were systematically evaluated via electrochemical analyses and post-mortem characterizations. By using a prelithiated LTO anode and supplying additional Li to the system, the capacity retention of LMR-NM/LTO system was improved. The degree of enhancement was dependent on the types of electrolytes used, as their decomposition products determined the level of LLI. With increased capacity retention, however, the cathode was utilized to a greater extent, resulting in more severe loss of the cathode active material. Thus, all degradation mechanisms should be considered comprehensively when designing high performance LMR-NM/LTO cells to account for their complex interplay.

Stabilizing anionic redox in Mn-rich P2-type layered oxide material by Mg substitution

Anionic oxygen redox reactions provide additional reversible capacity beyond 4 V in Mn-rich layered oxide cathodes; however, the irreversible anionic redox intensifies the structural deterioration, resulting in capacity fading. This study reports a stable anionic redox in Mn-rich P2-type Na0.67Mn0.8Fe0.1Ni0.1O2 by substituting Ni via Mg in the TM layer. The similarities in size and valence state of Mg2+ and Ni2+ confirm the homogenous substitution of Mg2+ into the TM layer, maintaining the layered structure. Mg2+ ion in the TM layer provides thermodynamic phase stability and facilitates the extra charge on the O atom that aggravates the oxidation of O, mitigating irreversible oxygen redox. As a result, Na0.67Mn0.8Fe0.1Mg0.1O2 displayed better reversibility in an expanded voltage range of 1.5–4.5 V and improved rate capability compared to Na0.67Mn0.8Fe0.1Ni0.1O2. Furthermore, Mg substitution reinforces the reversibility of the P2-O2 phase transition and improves Na+ diffusion kinetics. Hence, the profound study on Mg substitution in Mn-rich P2-type layered oxide is constructive to stabilize the anionic oxygen redox.

Heat Generation during the First Activation Cycle of Li-Ion Batteries with Li- and Mn-Rich Layered Oxides Measured by Isothermal Micro-Calorimetry

Using isothermal micro-calorimetry, we investigate the heat generation of lithium- and manganese-rich layered oxides (LMR-NCMs) during the first cycle in which LMR-NCM exhibits a pronounced voltage hysteresis leading to a low energy efficiency (≈73%). In the first charge, LMR-NCM shows a unique voltage plateau at ≈4.5 V where irreversible structural rearrangements lead to an activation of the material as well as a large voltage hysteresis. We found that only a fraction of the lost electrical work (≈43%) is converted into waste heat. Thereby, the heat flow profile of the first charge is unique and shows considerable heat generation during the voltage plateau. With complementary electrochemical methods, contributions of conventional sources of heat, i.e., because of polarization and entropy, are determined. However, they do not cause the considerable generation of heat during the voltage plateau. Our results therefore suggest that the structural rearrangements during activation lead to a significant generation of heat. In window-opening experiments, we demonstrate that the activation is a gradual process and that the heat generated during the first discharge is directly linked to the extent of activation during the preceding charge. We also investigate the effect of the degree of overlithiation on the heat generated during activation.

Accumulated Lattice Strain as an Intrinsic Trigger for the First-Cycle Voltage Decay in Li-Rich 3d Layered Oxides

Li- and Mn-rich layered oxides (LMLOs) are promising cathode materials for Li-ion batteries (LIBs) owing to their high discharge capacity of above 250 mA h g-1. A high voltage plateau related to the oxidation of lattice oxygen appears upon the first charge, but it cannot be recovered during discharge, resulting in the so-called voltage decay. Disappearance of the honeycomb superstructure of the layered structure at a slow C-rate (e.g., 0.1 C) has been proposed to cause the first-cycle voltage decay. By comparing the structural evolution of Li[Li0.2Ni0.2Mn0.6]O2 (LLNMO) at various current densities, the operando synchrotron-based X-ray diffraction results show that the lattice strain in bulk LLNMO is continuously increased over cycling, resulting in the first-cycle voltage loss upon Li-ion insertion. Unlike the LLNMO, the accumulated average lattice strain of LiNi0.8Co0.1Mn0.1O2 (NCM811) and LiNi0.6Co0.2Mn0.2O2 (NCM622) from the open-circuit voltage to 4.8 V could be released on discharge. These findings help to gain a deep understanding of the voltage decay in LMLOs.

XLi2MnO3·(1-x)LiMeO2 and Li4Ti5O12 cell chemistry for Behind-the-Meter Storage applications

Li- and Mn-rich layered oxide material (xLi2MnO3·(1-x)LiMeO2, Me = Ni, Mn, and etc., LMR-NM) is paired with Li4Ti5O12 (LTO) in a full cell and evaluated for the Behind-the-Meter Storage (BTMS) applications. The LMR-NM/LTO full cell shows very high capacities and excellent long-term cycle life. It delivers 192 mAh g−1 after 500 cycles at C/2 and 45 °C with a capacity retention of 75 % and coulombic efficiency higher than 99.95 %. It also has impressive rate capabilities. A capacity of 220 mAh g−1 is achieved at 2C which is 88 % of the initial capacity at C/10. The high cycling temperature clearly enhances electrochemical kinetics and activates more Li2MnO3 component, which gives high capacities, low cell impedance, and better rate capabilities. Moreover, it helps to form a relatively thick cathode-electrolyte interphase (CEI) film to suppress transition metal dissolution from the cathode surface. The upper cut-off voltage (UCV) of 3.0 V keeps the structural integrity of the cathode during cycling. A higher UCV of 3.2 V accelerates structural instabilities of the cathode as well as growth of the solid-electrolyte interphase (SEI) via transition metal dissolution and deposition on the anode surface. It results in higher cell impedance, worse capacity retention and faster capacity fade.

Impacts of Mg doping on the structural properties and degradation mechanisms of a Li and Mn rich layered oxide cathode for lithium-ion batteries

The Li- and Mn-rich layered oxide cathode material class is a promising cathode material type for high energy density lithium-ion batteries. However, this cathode material type suffers from layer to spinel structural transition during electrochemical cycling, resulting in energy density losses during repeated cycling. Thus, improving structural stability is an essential key for developing this cathode material family. Elemental doping is a useful strategy to improve the structural properties of cathode materials. This work examines the influences of Mg doping on the structural characteristics and degradation mechanisms of a Li1.2Mn0.4Co0.4O2 cathode material. The results reveal that the prepared cathode materials are a composite, exhibiting phase separation of the Li2MnO3 and LiCoO2 components. Li2MnO3 and LiCoO2 domain sizes decreased as Mg content increased, altering the electrochemical mechanisms of the cathode materials. Moreover, Mg doping can retard phase transition, resulting in reduced structural degradation. Li1.2Mn0.36Mg0.04Co0.4O2 with optimal Mg doping demonstrated improved electrochemical performance. The current work provides deeper understanding about the roles of Mg doping on the structural characteristics and degradation mechanisms of Li-and Mn-rich layered oxide cathode materials, which is an insightful guideline for the future development of high energy density cathode materials for lithium-ion batteries.

Effect of Three-in-One Surface Modification of Spherical, Co-Free Li-Rich Cathode Material for Li-Ion Batteries (Li1.2Mn0.6Ni0.2O2) with Citric Acid

The electrochemical activation of Li2MnO3 domains in Li- and Mn-rich layered oxides (LRLO) is highly important, and can be tuned by surface modification of the active materials to improve their cycling performance. In this study, citric acid was employed as a combined organic acid, reducing agent, and carbon precursor in order to remove surface residues from the calcination process, implement an oxygen deficient layer on the surface of the primary LRLO particles, and cover their surface with a carbon-containing coating after a final annealing step. A broad selection of bulk and surface sensitive characterization methods was used to characterize the post-treated spherical particles, providing the evidence for successful creation of an oxygen deficient near-surface region, covered by carbon-containing deposits. Post-treated materials show enhanced electrochemical discharge capacities after progressive Li2MnO3 activation, reaching maximum capacities of 247 mAh g−1. Gassing measurements reveal the suppression of oxygen release during the first cycle, concomitant with an increased CO2 formation for the carbon-coated materials. The voltage profile analysis in combination with post-mortem characterization after 300 cycles provide insights into the aging of the treated materials, which underlines the importance of the relationship between structural changes during scalable post-treatment and the electrochemical performance of the powders.