Lithium- and manganese-rich (LMR) layered oxides are promising high-energy cathodes for next-generation lithium-ion batteries, yet their commercialization has been hindered by a number of performance issues. While fluorination has been explored as a mitigating approach, results from polycrystalline-particle-based studies are inconsistent and the mechanism for improvement in some reports remains unclear. In the present study, we develop an in situ fluorination method that leads to fluorinated LMR with no apparent impurities. Using well-defined single-crystal Li_1.2Ni_0.2Mn_0.6O₂ (LNMO) as a platform, we show that a high fluorination level leads to decreased oxygen activities, reduced side reactions at high voltages, and a broadly improved cathode performance. Detailed characterization reveals a particle-level Mn³⁺ concentration gradient from the surface to the bulk of fluorinated-LNMO crystals, ascribed to the formation of a Ni-rich Li_zNi_xMn_2–xO_4–yF_y (x > 0.5) spinel phase on the surface and a “spinel-layered” coherent structure in the bulk where domains of a LiNi_0.5Mn_1.5O₄ high-voltage spinel phase are integrated into the native layered framework. This work provides fundamental understanding of the fluorination effect on LMR and key insights for future development of high-energy Mn-based cathodes with an intergrown/composite crystal structure.

$\mathrm{SrV}{\mathrm{O}}_3$ thin films with a high figure of merit for applications as transparent conductors were crystallized from amorphous layers using solid phase epitaxy (SPE). Epitaxial $\mathrm{SrV}{\mathrm{O}}_3$ films crystallized on $\mathrm{SrTi}{\mathrm{O}}_3$ using SPE exhibit room-temperature resistivities as low as $5.2\times {10}^{–5}$ and $2.5\times {10}^{–5}\mathrm{\Omega }\mathrm{cm}$, residual resistivity ratios of 2.0 and 3.8, and visible light transmission maxima of 0.89 and 0.52 for film thicknesses of 16 and 60 nm, respectively. $\mathrm{SrV}{\mathrm{O}}_3$ layers were deposited at room temperature using radiofrequency sputtering in an amorphous form and subsequently crystallized by heating in a controlled gas environment. The lattice parameters and mosaic angular width of x-ray reflections from the crystallized films are consistent with partial relaxation of the strain resulting from the epitaxial mismatch between $\mathrm{SrV}{\mathrm{O}}_3$ and $\mathrm{SrTi}{\mathrm{O}}_3$. A reflection high-energy electron diffraction study of the kinetics of SPE indicates that crystallization occurs via the thermally activated propagation of the crystalline/amorphous interface, like SPE phenomena in other perovskite oxides. Thermodynamic calculations based on density functional theory predict the temperature and oxygen partial pressure conditions required to produce the $\mathrm{SrV}{\mathrm{O}}_3$ phase and are consistent with the experiments. The separate control of deposition and crystallization conditions in SPE presents possibilities for the crystallization of transparent conductors in complex geometries and over large areas.

Cathode material with high nickel content is a promising candidate for the future generation of Li-ion batteries (LIBs). However, severe structural degradation during cycling limits its practical use, especially for electric vehicles. Herein, AlPO ₄ nanoparticles were synthesized and then coated onto the surface of a high-nickel layer-structured cathode via a dry coating method. The AlPO ₄ nanoparticles coating significantly improved the cycling stability from 69.2% to over 80% capacity retention after 140 cycles. Furthermore, the structure and chemical composition of the AlPO ₄ -coated cathode was investigated by XRD, SEM, XPS, and STEM. Compared with the non-coated cathode, we revealed a dual protective mechanism for enhanced cycling stability, where Al doping and Li ₃ PO ₄ coating play synergistic roles in protecting cathode material through long-term cycling. This work demonstrates a facile and environmentally friendly approach toward improving the performance of high-nickel LIB cathodes, which can be easily scaled up for industrial applications.