Improved Thermal Stability of Lithium-Rich Layered Oxide by Fluorine Doping

Surface and Interfacial Modulation of Lithium-Rich Manganese Layered Oxide Cathode Materials: Progress and Challenges

Exhibiting exceptional energy density and capacity, lithium-rich manganese-based layered oxide (LLOs) cathode materials have garnered considerable attention and are emerging as strong contenders for future lithium-ion battery systems. However, the manner in which they are employed in practice is hindered by several challenges, such as voltage fading, exhibiting a low initial coulombic efficiency, and suboptimal cycling stability, mainly attributed to oxygen depletion and phase transformation phenomena. The current review primarily centers on recent progress in addressing these issues through surface and interfacial modification techniques, including surface doping, coating, and oxygen vacancy engineering. Other strategies, such as spinel phase engineering and hybrid coating layers, are also discussed as potential solutions to enhance electrochemical performance, stability, and capacity retention. Additionally, exploration advancements in electrolyte design aimed at stabilizing the LLOs/electrolyte interface, reducing side reactions, and enabling the development of a stable solid electrolyte interphase (CEI). The review concludes by highlighting ongoing challenges, particularly in improving long-term cycling stability, and proposes prospective research directions aimed at further unlocking the potential of LLOs cathode materials for practical battery applications.

Modulating Surface Architecture and Electronic Conductivity of Li-rich Manganese-Based Cathode

Li-rich manganese-based cathode (LRMC) has attracted intense attention to developing advanced lithium-ion batteries with high energy density. However, LRMC is still plagued by poor cyclic stability, undesired rate capacity, and irreversible oxygen release. To address these issues, herein, a feasible polyvinylidene fluoride (PVDF)-assisted interface modification strategy is proposed for modulating the surface architecture and electronic conductivity of LRMC by intruding the F-doped carbon coating, spinel structure, and oxygen vacancy on the LRMC, which can greatly enhance the cyclic stability and rate capacity, and restrain the oxygen release for LRMC. As a result, the modified material delivers satisfactory cyclic performance with a capacity retention of 90.22% after 200 cycles at 1 C, an enhanced rate capacity of 153.58 mAh g-1 at 5 C and 126.32 mAh g-1 at 10 C, and an elevated initial Coulombic efficiency of 85.63%. Moreover, the thermal stability, electronic conductivity, and structure stability of LRMC are also significantly improved by the PVDF-assisted interface modification strategy. Therefore, the strategy of simultaneously modulating the surface architecture and the electronic conductivity of LRMC provides a valuable idea to improve the comprehensive electrochemical performance of LRMC, which offers a promising reference for designing LRMC with high electrochemical performance.

Integrated Surface Functionalization of Li-Rich Cathode Materials for Li-Ion Batteries

As candidates for high-energy density cathodes, lithium-rich (Li-rich) layered materials have attracted wide interest for next-generation Li-ion batteries. In this work, surface functionalization of a typical Li-rich material Li_1.2Mn_0.56Ni_0.17Co_0.07O₂ is optimized by fluorine (F)-doped Li₂SnO₃ coating layer and electrochemical performances are also enhanced accordingly. The results demonstrate that F-doped Li₂SnO₃-modified material exhibits the highest capacity retention (73% after 200 cycles), with approximately 1.2, 1.4, and 1.5 times of discharge capacity for Li₂SnO₃ surface-modified, F-doped, and pristine electrodes, respectively. To reveal the fundamental enhancement mechanism, intensive surface Li⁺ diffusion kinetics, postmortem structural characteristics, and aging tests are performed for four sample systems. The results show that the integrated coating layer plays an important role in addressing interface compatibility, not only limited in stabilizing the bulk structure and suppressing side reactions, synergistically contributing to the performance enhancement for the active electrodes. These findings not only pave the way to commercial application of the Li-rich material but also shed new light on surface modification in batteries and other energy storage fields.