Li-rich Materials Research Articles

Performance improvement strategies of boron-doped lithium-rich layered oxide cathode materials for wide temperature condition

Herein, the boron-doped Li-rich materials are prepared by rapid nucleation-assisted solvothermal and high-temperature method. In this work, the effects of boron doping on crystal structure and cycling performances of as-prepared materials were investigated. The material characterization results show that the introduction of B reduces the TM valence, enlarges the (003) space distance, and modulates the local crystal structure, which may change the electrochemical performance of as-prepared samples. Li1.2Ni0.24Co0.08Mn0.48B0.02O2 (LLNCMBO-2) showed an increase in discharge capacity of 36.5 mAh g−1 at 0.1 C compared to the pristine sample. The LLNCMBO-2 exhibit high capacity retention of 85.50 % after 200 cycles with a voltage decay of only 254.9 mV. Additionally, the results of wide temperature testing show that the electrochemical performance of boron-doped samples improved evidently.

Manganese octahedral point-constructed oxygen defects realize highly stable lithium-rich cathode materials

Lithium-rich layered oxides (LLOs) are highly favored by researchers for their high specific capacity and low cost. However, the severe voltage and capacity degradation of the material have become the biggest obstacle to commercial application. In this work, the construction of oxygen vacancies on the surface of Li-rich cathode and SiO44- gradient doping have been used in Li-rich materials to improve its performance. The presence of oxygen defects in MnO6 octahedra stabilizes its structure and enhances the electrochemical activity of TM ions. This also serves to reduce the energy level and intensity of the unhybridized O 2p orbitals, as well as decrease the release of lattice oxygen. The "localization effect" of SiO44− on TM ions also inhibits their irreversible migration. After modification, the electrochemical performance of the material has been significantly improved. The initial Coulombic efficiency increased to 89.46 % (82.68 % for LLO), while the specific capacity discharge at 5C reached 178.8 mAh g−1 (139.2 mAh g−1 for LLO). Additionally, the capacity rate after 500 cycles at 1C was 74.1 % (54.5 % for LLO). Therefore, this work provides valuable insights for designing oxygen-deficient lithium-rich cathode materials.

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.

Unravelling the Effect of Sodium Doping on Li2MnO3 nanostructured Cathode Materials

The quest to develop affordable, high-performance electrode materials for lithium-ion batteries in electric vehicles is driving scientific innovation forward. Li2MnO3, as a prospective high-capacity (459 mAh.g-1) cathode, suffers from capacity degradation and voltage decay during the cycling process. Nanostructuring and incorporating sodium ions into lithium sites can mitigate voltage decay by limiting transition metal migration, impeding oxygen loss, and improving lithium diffusion by lowering the activation energy of Li-rich layered host materials. Herein, sodium-incorporated nonospherical structures of the form Li2-xNaxMnO3 (0 ≤ x ≤ 2), generated through the amorphisation and recrystallisation (A+R) technique show remarkable structural stability and enhanced Li-ion mobility owing to the enlarged lithium lattice upon sodium entrance. Specifically, the Li1.95Na0.05NaO3 nanosphere, displays more stable Li+/Mn4+ layers which will greatly contribute to its capacity. The microstructures associated with this configuration show well-ordered layers with high lithium kinetics and lower activation energy compared to pristine Li2MnO3. Characterisation of the x-ray diffraction (XRD) patterns revealed peak broadening along with the shifting of peaks at 2Θ~38 to the right due to the enlarged lithium layers occupied by sodium ions to facilitate lithium diffusion. Moreover, the undesired phase transformation from layered to spinel was observed at a later stage of charge for the sodium-doped systems, suggesting that the presence of sodium stabilizes the structure and minimizes the migration of manganese into lithium layers. These findings may lead to solutions for problems such as structural instability, lattice oxygen loss, and capacity decay in layered lithium oxide materials.

Regulating electronic structure of anionic oxygen by Ti4+ doping to stabilize layered Li-rich oxide cathodes for Li-ion batteries

Abstract Layered Li-rich oxide cathodes enable to activate lattice oxygen anions redox in the charge compensation process and provide superior high specific capacity over 250 mAh g−1 due to their unique configuration, and thus attracting great attentions as promising cathode candidates for Li-ion batteries. However, how to better stabilize the bulk lattice oxygen framework and surface structure, and slow down the release of oxygen, is still major bottleneck to develop high performance Li-rich materials. Transition metal ions with outer d0 electronic configuration have distortable configuration, which can accommodate the local structure and chemical environment of the material, and then improve structural stability. Herein this work, the d0 transition metal Ti4+ is used as doping element to improve the chemical and structural stability, capacity retention and lithium ion diffusion kinetics of Li-rich material. The role of Ti in the material modification is revealed through synchrotron-based soft x-ray absorption spectroscopy, XRD, XPS and electrochemical tests. The improvement in structural stability can be attributed to that Ti doping can adjust the hybridization of O2p and TM3d to regulate the local electronic structure of both bulk lattice oxygen and surface oxygen vacancies. It is hoped that this work should shed light on the development of high-performance cathode materials for Li-ion Batteries.

Activation of Oxygen Redox by Inhibited Dynamic Phase Transition for High-Energy Li-Rich Layered Oxide Cathode

Li-rich layered oxides have garnered tremendous research interest as a promising high-energy cathode by harnessing combined cationic and anionic redox. Despite the great promise of oxygen redox, however, the distinct activity of oxygen redox in Li-rich materials has inhibited the precise understanding of the oxygen redox activation mechanism. Herein, we unravel the interplay between de/activation of oxygen redox and the phase transition behaviors of Li-rich cathodes through a comprehensive investigation of two Ru-based model Li-rich layered oxides, Li1.2Ni0.2Mn0.3Ru0.3O2 and Li1.2Ni0.2Ru0.6O2. It is corroborated by synchrotron-based X-ray absorption spectroscopy analyses that the reversible oxygen redox occurs inLi1.2Ni0.2Mn0.3Ru0.3O2 but the reaction is not triggered in Li1.2Ni0.2Ru0.6O2 despite high relevancein structure and stoichiometry. Operando X-ray diffraction elucidates that the O3-type Li1.2Ni0.2Ru0.6O2 undergoes a phase transition into the T3-type phase during charging while there is negligible structural change in O3-type Li1.2Ni0.2Mn0.3Ru0.3O2. First-principles studies reveal that the theoretical redox potential to extract Li+ from T3-type phase is significantly higher than that of O3-type Li1.2Ni0.2Ru0.6O2, inhibiting the activation of the oxygen redox.Our findings indicate the significance of the dynamic structural evolution on governing the activation of oxygen redox, thereby offering guidance for further design of Li-rich layered oxides toward the full utilization of the oxygen redox.

A Cable-Stayed Honeycomb Superstructure to Improve the Stability of Li-Rich Materials via Inhibiting Interlaminar Lattice Strain.

In layered Li-rich materials, over stoichiometric Li forms an ordered occupation of LiTM6 in transition metal (TM)layer, showing a honeycomb superstructure along [001] direction. At the atomic scale, the instability of the superstructure at high voltage is the root cause of problems such as capacity/voltage decay of Li-rich materials. Here a Li-rich material with a high Li/Ni disorder is reported, these interlayer Ni atoms locate above the honeycomb superstructure and share adjacent O coordination with honeycomb TM. These Ni─O bonds act as cable-stayed bridge to the honeycomb plane, and improve the high-voltage stability. The cable-stayed honeycomb superstructure is confirmed by in situ X-ray diffraction to have a unique cell evolution mechanism that it can alleviate interlaminar lattice strain by promoting in-plane expansion along a-axis and inhibiting c-axis stretching. Electrochemical tests also demonstrate significantly improved long cycle performance after 500 cycles (86% for Li-rich/Li half cell and 82% for Li-rich/Si-C full cell) and reduced irreversible oxygen release. This work proves the feasibility of achieving outstanding stability of lithium-rich materials through superstructure regulation and provides new insights for the development of the next-generation high-energy-density cathodes.

Elements gradient doping in Mn-based Li-rich layered oxides for long-life lithium-ion batteries

The cobalt-free Mn-based Li-rich layered oxide material has the advantages of low cost, high energy density, and good performance at low temperatures, and is the promising choice for energy storage batteries. However, the long-cycling stability of batteries needs to be improved. Herein, the Mn-based Li-rich cathode materials with small amounts of Li2MnO3 crystal domains and gradient doping of Al and Ti elements from the surface to the bulk have been developed to improve the structure and interface stability. Then the batteries with a high energy density of 600 Wh kg−1, excellent capacity retention of 99.7 % with low voltage decay of 0.03 mV cycle−1 after 800 cycles, and good rates performances can be achieved. Therefore, the structure and cycling stability of low voltage Mn-based Li-rich cathode materials can be significantly improved by the bulk structure design and interface regulation, and this work has paved the way for developing low-cost and high-energy Mn-based energy storage batteries with long lifetime.

Enabling Ultrastable Co-Free Li-Rich Oxides via TbF3 Treatment.

Co-free Li-rich Mn-based cathode materials (Co-free LRMOs) have become one of the most promising cathode materials in lithium-ion batteries for the next generation due to their low cost, high capacity, and environmental friendliness. Under high voltage, redox reactions involving anions can easily lead to various issues, including oxygen release, dissolution of transition metal elements (TMs), and structural collapse in these materials. The absence of the Co element further exacerbates this issue. Here, a simple one-step solid-phase reaction strategy is proposed to achieve nanoscale dual modification of the Co-free LRMOs with F and Tb doping. The dual modification has a relatively small impact on the cell parameters and Li+ diffusion ability of the LRMOs, leading to no significant improvement in its rate performance. The modified LRMOs only exhibited discharge capacities of 220.7, 200.1, 140.0, 115.5, and 90.9 mAh·g-1 at 0.1, 0.2, 1.0, 2.0, and 5.0 C, respectively. However, the modified Co-free LRMOs exhibit extremely strong structural stability and retain 95.1% of the initial capacity after 300 cycles, so far, the highest capacity retention rates among all Ni/Mn-based Li-rich materials. Mechanism studies have shown that the enhancement in structural stability of the Co-free LRMOs is attributed to the increased concentration of oxygen vacancies and Ni3+ ions through F doping. Furthermore, Tb doping not only hinders the release of O2 but also enhances the Li+ migration and electronic conductivity coefficient of the LRMOs.

Synergistic strategy of surface-induced spinel structure and F doping to improve the electrochemical performance of Li-rich cathodes

Li-rich Mn-based materials provide higher capacity than commercial NCM layered materials due to the synergistic redox effect of cations and anions. However, lattice straining and structural collapse caused by the irreversible oxygen release at high voltage range during cycling, which results in severe capacity and voltage decay. Herein, a synergistic strategy of surface-induced spinel structure and F doping is provided to improve the structural stability. The surface spinel structure helps to reduce the structural collapse caused by electrolyte corrosion on the cathode and effectively inhibits voltage decay resulted from structural evolution. The stronger Mn-F bonds are formed by F doping to inhibit migration of transition metal (TM) and induce the uniform deposition of LiF to form the thinner and more stable CEI on the cathode. Accordingly, the designed cathode (LMNO-NF) shows remarkable cycling performance with the capacity retention of 86.68 ​% and voltage retention of 96.6 ​% for 200 cycles at 1C, higher than pristine material (68.76 ​% and 85.75 ​%). Therefore, this simple dual-modification strategy of one-step synthesis is promising for solving the structural evolution and voltage decay of Li-rich Mn-based cathode materials effectively, achieving further commercialization.

Perspective on High-Stability Single-Crystal Li-Rich Cathode Materials for Li-Ion Batteries.

Benefiting from anionic and cationic redox reactions, Li-rich materials have been regarded as next-generation cathodes to overcome the bottleneck of energy density. However, they always suffer from cracking of polycrystalline (PC) secondary particles and lattice oxygen release, resulting in severe structural deterioration and capacity decay upon cycling. Single-crystal (SC) design has been proven as an effective strategy to relieve these issues in traditional Li-rich cathodes with PC morphology. Herein, we first reviewed the main synthesis routes of SC Li-rich materials including solid-state reaction, molten salt-assisted, and hydrothermal/solvothermal methods, in which the differences in grain morphology, electrochemical behaviors, and other properties induced by various routes were analyzed and discussed. Furthermore, the distinct characteristics were compared between SC and PC cathodes from the aspects of irreversible capacity, structural stability, capacity/voltage degradation, and gas release. Besides, recent advances in layered SC Li-rich oxide cathodes were summarized in detail, where the unique structural designs and modification strategies could greatly promote their structural/electrochemical stability. At last, challenges and perspectives for the emerging SC Li-rich cathodes were proposed, which provided an exceptional opportunity to achieve high-energy-density and high-stability Li-ion/metal batteries.

Triggering cationic/anionic hybrid redox stabilizes high-temperature Li-rich cathodes materials via three-in-one strategy

Efficiently advancing lithium-ion batteries toward high energy density entails overcoming challenges in Li-rich layered oxides, including severe voltage and capacity fading, irreversible oxygen escape and compromised thermal robustness due to the uncontrollable oxygen anionic redox (OAR). Herein, a three-in-one modification strategy, aim at strengthening the reversibility of OAR and structural integrity of MnO6 octahedron, is rationally introduced on Li1.2Mn0.53Ni0.20Co0.07O2 cathode through a universal H3BO3-treatment. Through the introduction of oxygen vacancies and gradient B-doping, the energy level of unhybridized O 2p states is decreased to narrow the band energy gap with transition metal (TM) band, which triggers cationic/anionic hybrid redox at high voltage, thereby stabilizing the peroxo-like (O2)n- species and hindering irreversible oxygen escape, while the lithium borate nano-coating serves to mitigate side reactions, particularly during charging at elevated temperatures. As a result, the modulated cathode exhibits notable capacity retention of 96.3 % after 500 cycles at 1 C with limited voltage fading rate (1.73 mV per cycle) and even stable cyclic performance at high temperature (60 °C). This approach provides an effective and straightforward method to tackle the voltage decay and capacity fading of high-energy Li-rich layered cathode materials.

New exploration of water-soluble lithium polyacrylate/xanthan gum composite binder for Li-rich Mn-based cathode materials

Li-rich Mn-based oxides are considered promising cathode materials of Li-ion batteries with high specific capacity and operating voltage. However, Li-rich materials suffer from a high initial irreversible capacity loss and severe voltage attenuation during cycling. In this work, lithium polyacrylate (LiPAA) was crosslinked with xanthan gum (XG) to form a water-soluble binder for Li[Li0.2Co0.13Ni0.13Mn0.54]O2 electrode. The capacity retention was 78.3 % after 100 cycles at 0.2 C. LiPAA provided additional Li+ ions during cycling, while XG firmly bound to the surface of the active particles. Cost-effective binders provide a facile mean to improve the electrochemical performance of Li-rich cathode materials.

Performance improvement of Li-rich Mn-based materials with the submicron-sized single-crystal morphology and cationic doping

Lithium-rich manganese-based cathode materials (LRMCs) can be regarded as one of the most potential cathode materials for the next-generation high-energy Li-ion batteries due to the extra oxygen redox, which can greatly increase the actual output energy density of LRMCs. Nevertheless, the structure degradation and inevitable loss of oxygen will be triggered by the irreversible oxygen redox, which will cause a significant decline in cyclic performance and limited initial Coulombic efficiency, thus restricting their industrial applicability. Herein, the LRMCs with the submicron-sized single-crystal morphology and sodium doping are prepared by molten salt treatment with NaCl. On one hand, the submicron-sized single-crystal cathode effectively reduces the diffusion path for Li+ due to the smaller particle dimensions. On the other hand, Na+ doping expands the Li slab spacing, promoting the transport of Li+. The results show that the as-prepared material can purposefully alleviate oxygen release, improve structure stability, and increase the Li+ diffusion rate for the pristine LRMCs. Moreover, the as-prepared material in this study exhibits a higher reversible capacity of 282.8 mAh g−1 at 0.1 C and displays good cyclic performance, retaining a capacity rate of 80.9% after 200 cycles at 1 C. Therefore, this study offers a potential exploration for designing LRMCs with high energy density and excellent cyclic performance, which are achieved through building submicron-sized single-crystal morphology and introducing cationic doping.

Formulating Local Environment of Oxygen Mitigates Voltage Hysteresis in Li-Rich Materials.

Li-rich cathode materials have emerged as one of the most prospective options for Li-ion batteries owing to their remarkable energy density (>900Wh kg-1). However, voltage hysteresis during charge and discharge process lowers the energy conversion efficiency, which hinders their application in practical devices. Herein, the fundamental reason for voltage hysteresis through investigating the O redox behavior under different (de)lithiation states is unveiled and it is successfully addressed by formulating the local environment of O2-. In Li-rich Mn-based materials, it is confirmed that there exists reaction activity of oxygen ions at low discharge voltage (<3.6V) in the presence of TM-TM-Li ordered arrangement, generating massive amount of voltage hysteresis and resulting in a decreased energy efficiency (80.95%). Moreover, in the case where Li 2b sites are numerously occupied by TM ions, the local environment of O2- evolves, the reactivity of oxygen ions at low voltage is significantly inhibited, thus giving rise to the large energy conversion efficiency (89.07%). This study reveals the structure-activity relationship between the local environment around O2- and voltage hysteresis, which provides guidance in designing next-generation high-performance cathode materials.

Enhancing reversible capacity and cycling stability of Li&lt;sub&gt;1.2&lt;/sub&gt;Ni&lt;sub&gt;0.13&lt;/sub&gt;Fe&lt;sub&gt;0.13&lt;/sub&gt;Mn&lt;sub&gt;0.54&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt; by inducing low Li/Ni misalignment through Mo doping

Li-ion batteries (LIBs) are widely used in mobile devices and electric vehicles, but the traditional layered transition metal cathode material, LiTMO&lt;sub&gt;2 &lt;/sub&gt;(TM=Ni, Co, Mn, or Al), has a low energy density that cannot satisfy the demand of commercial applications. The Li-rich Mn-based layered oxides (LRLOs) are a strong competitor to the traditional layered cathode materials for their specific capacity of more than 200 mAh/g. Due to the high energy density and low cost, Li-rich Mn-based layered oxides (LRLO) have been a promising candidate cathode for next-generation Li-ion batteries. The anionic redox reaction (ARR) in LRLO destabilizes the lattice oxygen, leading to voltage degradation and capacity loss. Although iron-substituted cobalt-free Li-rich materials can achieve less voltage decay, they suffer severe cation disorder and poor kinetics. Here, we develop a simple and feasible high-valent ion doping strategy by doping Mo into Li&lt;sub&gt;1.2&lt;/sub&gt;Ni&lt;sub&gt;0.13&lt;/sub&gt;Fe&lt;sub&gt;0.13&lt;/sub&gt;Mn&lt;sub&gt;0.54&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt;(LNFMO), which expands the Li layer spacing and provides a broader channel for Li&lt;sup&gt;+&lt;/sup&gt; transport, thereby improving the diffusion kinetics of Li&lt;sup&gt;+&lt;/sup&gt;, effectively suppressing the cation disorder, and further stabilizing the layered structure. As a result, the Mo-doped LRLO exhibits significantly enhanced electrochemical performance, with an initial reversible capacity of 209.48 mAh/g at 0.2 C, and the initial specific capacity increasing from 137.02 mAh/g to 165.15 mAh/g at 1 C. After 300 cycles, specific capacity remains 117.49 mAh/g for the Mo-doped cathode, and the voltage decay decreases from 2.09 mV/cycle to 1.66 mV/cycle. The Mo-doped LRLO is systematically characterized, and the mechanism of cycle stabilization is revealed, which provides an important reference for designing high performance Li-rich cathode.

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).

Improving the electrochemical performance of Li-rich manganese-based cathode materials by surface treatment with triethylamine

Li-rich manganese-based cathode material is expected to be extremely promising for next-generation lithium-ion batteries due to its high specific capacity derived from additional anion redox behavior and low cost of the main element manganese. However, the irreversible release of lattice oxygen results in poor structural stability and inferior electrochemical performances, such as low initial Coulomb efficiency, irreversible capacity decay and serious voltage decay, which limits its commercialization. Herein, a simple strategy to improve the structural stability and electrochemical performances by one-step treatment with triethylamine (TEA) at moderate temperature is reported. TEA was used as a surface treatment reagent to prepare the modified Li-rich manganese-based cathode materials with oxygen vacancies and local structural distortion on the surface. The presence of surface distortion layer and oxygen vacancies inhibits irreversible oxygen release. The result exhibits that initial Coulomb efficiency, rate performance and initial discharge specific capacities are improved. After 100 cycles at a current density of 1 C, the specific capacity of the surface-treated material is 204.3 mAh g-1 (172.6 mAh g-1 for the pristine material), with a capacity retention of 81.26%. Even at a high current density of 10 C, the discharge specific capacity of 139.4 mAh g-1 is still achieved, demonstrating the excellent electrochemical performance. This study provides a simple and effective strategy for constructing special surface structures on Li-rich manganese-based materials to achieve high performance.

Unlocking the Potential of Li-Rich Mn-Based Oxides for High-Rate Rechargeable Lithium-Ion Batteries.

Lithium-rich Mn-based oxides have gained significant attention worldwide as potential cathode materials for the next generation of high-energy density lithium-ion batteries. Nonetheless, the inferior rate capability and voltage decay issues present formidable challenges. Here, a Li-rich material equipped with quasi-three-dimensional (quasi-3D)Li-ion diffusion channels is initially synthesized by introducing twin structures with high Li-ion diffusion coefficients into the crystal and constructing a "bridge" between different Li-ion diffusion tunnels. The as-prepared material exhibits monodispersed micron-sized primary particles (MP), delivering a specific capacity of 303mAhg-1 at 0.1 C and an impressive capacity of 253mAhg-1 at 1 C. More importantly, the twin structure also serves as a "breakwater" to inhibit the migration of Mn ions and improve the overall structural stability, leading to cycling stability with 85% capacity retention at 1 Cafter 200 cycles. The proposed strategy of constructing quasi-3Dchannels in the layered Li-rich cathodes will open up new avenues for the research and development of other layered oxide cathodes, with potential applications in industry.

Rational design of high reversible capacity in Li-rich disordered rocksalt cathodes

The Li-excess rocksalt materials have opened a vast new chemical space to develop low-cost and high-energy-density cathode materials for satisfying the rising market demand of rechargeable batteries. However, those materials suffer from capacity and voltage decay on cycling due to irreversible structural rearrangement. Quantitatively characterizing reversible capacity are decisive to collaboratively improve capacity and cycling stability, but very challenging to predict for experiencing complicated redox. A “state-accumulated charge-transfer gap” model is introduced to continuously accumulate electrochemical reversibility effect during the whole redox process. This is demonstrated through rational design and preparation of several representative compositions in the cation-disordered Li-Mn-Ti-O-F chemical space. Based on electrochemical tests and first-principles studies, we found that Li1.2Mn0.6Ti0.2O1.67F0.33 with almost complete Mn4+ oxidation states and a little anionic redox in the end of charge could achieve high capacity of 330 mAh g−1 in first cycle and 225 mAh g−1 after 20 cycles, which reaches the best comprehensive electrochemical performance in reported Li-rich materials. The present study opens a new avenue to design Li-rich cathode materials with high reversible capacity.