Arcangelo Celeste

Calcination strategy primarily influences the spatial distribution of residual Li containing surface species rather than bulk NMC811 structure, governing interfacial reactivity, impedance growth, and cycling stability.

This manuscript investigates the impact of solid‐state (SS), sol‐gel (SG), and solvothermal (ST) synthetic routes on high‐nickel Li‐rich layered oxide (LRLO) cathodes for lithium‐ion batteries, utilizing techniques like SEM, XRD, and electrochemical assessments. The sol‐gel (SG) method consistently produced superior materials. SG samples exhibited higher phase purity, better crystallinity, and fewer detrimental lithium carbonate surface species, as confirmed by XRD and FT‐IR. Morphologically, SG yielded smaller, more homogeneous prismatic particles, which are advantageous for electrochemical performance. These material improvements directly translated to outstanding battery performance for SG cathodes. They delivered a sustained specific capacity of approximately 200 mAh/g, significantly exceeding the ~150 mAh/g from SS and ST methods. SG also showed exceptional cycling stability, characterized by stable voltage profiles, lower fading, 99.5% Coulombic efficiency, and 80.6% capacity retention over 500 cycles. Conversely, SS and ST materials displayed lower phase purity, increased structural defects, and more surface impurities, resulting in inferior electrochemical behavior. Overall, the sol‐gel method offers critical control for optimizing LRLO functional properties for next‐generation high‐energy density lithium‐ion batteries.

Lithium‐sulfur (Li‐S) batteries deliver gravimetric energy densities considerably higher than those of conventional lithium‐ion systems while relying on low‐cost, earth‐abundant materials. Despite decades of progress, their commercialization remains hindered by intrinsic challenges such as the insulating nature of sulfur and lithium sulfide (Li ₂ S), formation and dissolution of soluble polysulfides, and instability of lithium‐metal anodes. Among these, the use of Li ₂ S as a pre‐lithiated cathode has redefined the landscape of Li─S chemistry by offering a pathway toward lithium‐free and anode‐free architectures that are compatible with the existing manufacturing infrastructure. This perspective revisits the Li ₂ S electrochemistry from a conceptual and design standpoint. The perspective emphasizes multiscale strategies for atomic‐level catalytic engineering, mesoscale electrode architectures, and electrolyte–interface control, which collectively determine Li ₂ S activation and reversibility. The perspective also examines emerging approaches that integrate Li ₂ S cathodes with graphite, silicon, and solid‐state configurations to enable safe, high‐energy, and manufacturable Li─S technologies. Finally, this perspective discusses the evolving roles of redox mediators, machine learning‐based discovery, and sustainable synthesis in bridging the gap between laboratory breakthroughs and industrial viability. Collectively, these insights frame Li ₂ S not only as an alternative, cathode, but also as a platform for reimagining Li─S electrochemistry in the post‐lithium‐metal era.

Formation during the first cycles of Li-rich layered oxide (LRLO) cathode materials consolidates the interphase and leads to structural changes that are decisive for long-term cyclability. However, the nature and effect of the changes are material-dependent and unknown for the important class of Co-free, Ni-poor LRLOs. Here, we analyze the processes during the tailored formation procedure of a typical class member, Li_1.28Ni_0.15Mn_0.57O₂, and demonstrate that it remarkably changes lattice composition and structure as a prerequisite for stable cycling. We combine electrochemistry, operando mass spectrometry, X-ray diffraction, and X-ray absorption spectroscopy with density functional theory simulations. Activation most prominently compresses the layer spacing along the c-axis and increases reversible structural breathing. The large capacity of ∼250 mAh g^–1 originates from the Ni²⁺/Ni⁴⁺ and O^2–/O^– redox couples. Electron exchange during O-redox is smeared over the entire anionic sublattice rather than localized on specific oxygen atomic sites. This redox mechanism is reversible without detrimental oxygen evolution, avoiding continued degradation common in conventional LRLOs. Sequential Ni- and O-redox during activation irreversibly distorts the coordination of the redox-inactive Mn⁴⁺ centers. This structural evolution of the MnO₆ octahedra appears to enable the superior electrochemical performance of this LRLO phase. These findings define an activation pathway for the important class of Co-free, Ni-poor LRLOs, offering potential guidance for the rational design of high-performance, more sustainable cathode materials.

This study highlights a novel perspective on the role of defectivity in governing the electrochemical performance of cobaltfree lithium-rich layered oxide (LRLO), specifically Li1.24Mn_0.62Ni_0.14O₂. By varying the solvent environment during solvothermal synthesis, using binary mixtures of water and ethanol, we demonstrate that the nature of the solvent profoundly influences defect formation within the material. These solvent-dependent defect structures emerge as the key drivers of electrochemical behavior, rather than just crystallinity or composition. Through advanced characterization techniques including synchrotron X-ray diffraction, electron diffraction, transmission electron microscopy, and positron annihilation lifetime spectroscopy, we reveal how each solvent system tailors specific microstructural and defect profiles.Despite identical nominal compositions, these variations in defectivity lead to remarkable different electrochemical performances. Our findings underscore the critical role of solvent selection in tuning defect chemistry, offering a new pathway for optimizing LRLO materials by intentionally controlling defect landscapes during synthesis.

Material characterization and investigation are the basis for improving the performance of electrochemical devices. However, many compounds with electrochemical applications are sensitive to atmospheric gases and moisture; therefore, even their characterization should be performed in a controlled atmosphere. In some cases, it is impossible to execute such investigations in a glove box, and, therefore, in the present work, an air-tight 3D printed cell was developed that preserves samples in a controlled atmosphere while allowing spectroscopic measurements in reflectance geometry. Equipped with a cheap 1 mm thick CaF₂ optical window or a more expensive 0.5 mm thick ZnS window, the cell was used for both optical photothermal infrared and Raman spectroscopy measures; imaging of the samples was also possible. The far-infrared range reflectance measurements were performed with a cell equipped with a diamond window.