A facile in-situ coating strategy for Ni-rich cathode materials with improved electrochemical performance

LiAlSiO4-coated Li1.2Mn0.54Ni0.13Co0.13O2 cathode: Enhancing Li-ion battery performance

The lithium fast ion conductor LiAlSiO4 demonstrates exceptional lithium-ion transmission properties alongside remarkable chemical stability. Utilizing sol-gel techniques, we synthesized LiAlSiO4-coated cathode materials (LNCM@LASO) based on Li1.2Mn0.54Ni0.13Co0.13O2 to enhance their electrochemical performance. Rm space groups were identified in all materials through high-intensity diffraction peaks, indicating the presence of hexagonal layered α-NaFeO2 structures. Benefiting from the coating layer of LiAlSiO4, the conductivity and electrochemical performance of Li1.2Mn0.54Ni0.13Co0.13O2 are significantly improved. Compared with the unmodified LASO-0 sample (42.27%), the LASO-3 sample exhibits a superior initial coulomb efficiency of 66.02%. At various charge/discharge rates (0.1, 0.2, 0.5, 1, and 2 C), the LASO-3 electrode exhibits specific discharge capacities of 210.6, 189.3, 168.1, 151.8, and 125.2 mAh·g-1, correspondingly. Upon reverting the current density from 2 C to 0.1 C, the discharge capacity of the LASO-3 electrode rebounds to 206.4 mAh·g-1. After 100 cycles at 0.1 C, the LASO-3 electrode achieves a peak capacity retention rate of 88.9%. The superior conductive properties and chemical stability of the LNCM@LASO enhance the electron and ion transfer, thereby preventing electrolyte attack and boosting the electrochemical performance. This research marks a crucial step towards developing high-capacity, low-cost lithium-ion batteries with wide-ranging implications across multiple disciplines and industries.

Lithium-Ion Conductive Coatings for Nickel-Rich Cathodes for Lithium-Ion Batteries

Nickel (Ni)-rich cathodes are among the most promising cathode materials of lithium batteries, ascribed to their high-power density, cost-effectiveness, and eco-friendliness, having extensive applications from portable electronics to electric vehicles and national grids. They can boost the wide implementation of renewable energies and thereby contribute to carbon neutrality and achieving sustainable prosperity in the modern society. Nevertheless, these cathodes suffer from significant technical challenges, leading to poor cycling performance and safety risks. The underlying mechanisms are residual lithium compounds, uncontrolled lithium/nickel cation mixing, severe interface reactions, irreversible phase transition, anisotropic internal stress, and microcracking. Notably, they have become more serious with increasing Ni content and have been impeding the widespread commercial applications of Ni-rich cathodes. Various strategies have been developed to tackle these issues, such as elemental doping, adding electrolyte additives, and surface coating. Surface coating has been a facile and effective route and has been investigated widely among them. Of numerous surface coating materials, have recently emerged as highly attractive options due to their high lithium-ion conductivity. In this review, a thorough and comprehensive review of lithium-ion conductive coatings (LCCs) are made, aimed at probing their underlying mechanisms for improved cell performance and stimulating new research efforts.

Molybdenum-Doped Cobalt-Free Cathode Realizing the Electrochemical Stability by Enhanced Covalent Bonding

The doping strategy effectively enhances the capacity and cycling stability of cobalt-free nickel-rich cathodes. Understanding the intrinsic contributions of dopants is of great importance to optimize the performances of cathodes. This study investigates the correlation between the structure modification and their performances of Mo-doped LiNi0.8Mn0.2O2 (NM82) cathode. The role of doped Mo's valence state has been proved functional in both lattice structural modification and electronic state adjustment. Although the high-valence of Mo at the cathode surface inevitably reduces Ni valence for electronic neutrality and thus causes ion mixing, the original Mo valence will influence its diffusion depth. Structural analyses reveal Mo doping leads to a mixed layer on the surface, where high-valence Mo forms a slender cation mixing layer, enhancing structural stability and Li-ion transport. In addition, it is found that the high-valence dopant of Mo6+ ions partially occupies the unfilled 4d orbitals, which may strengthen the Mo─O bond through increased covalency and therefore reduce the oxygen mobility. This results in an impressive capacity retention (90.0% after 200 cycles) for Mo-NM82 cathodes with a high Mo valence state. These findings underscore the valence effect of doping on layered oxide cathode performance, offering guidance for next-generation cathode development.

Enhanced microstructure stability of LiNi0.8Co0.1Mn0.1O2 cathode with negative thermal expansion shell for long-life battery

With high specific energy density, Ni-rich layered LiNi_0.8Co_0.1Mn_0.1O₂ (NCM) material has become one promising cathode candidate for advanced lithium-ion batteries (LIBs). However, severe capacity fading induced by microstructure degradation and deteriorated interfacial Li⁺ transportation upon repeated cycling makes the commercial application of NCM cathode in dilemma. To address these issues, LiAlSiO₄ (LASO), one unique negative thermal expansion (NTE) composite with high ionic conductivity, is utilized as a coating layer to improve the electrochemical performances of NCM material. Various characterizations demonstrate that LASO modification can endow NCM cathode with significantly enhanced long-term cyclability, through reinforcing the reversibility of phase transition and restraining lattice expansion, as well as depressing microcrack generation during repeated delithiation-lithiation processes. The electrochemical results indicate that LASO-modified NCM cathode can deliver an excellent rate capability of 136 mAh g^-1 at a high current rate of 10 C (1800 mA g^-1), larger than that of the pristine cathode (118 mAh g^-1), especially higher capacity retention of 85.4% concerning the pristine NCM cathode (65.7%) over 500 cycles under 0.2 C. This work provides a feasible strategy to ameliorate the interfacial Li⁺ diffusion and suppress the microstructure degradation of NCM material during long-term cycling, which can effectively promote the practical application of Ni-rich cathode in high-performance LIBs.

Toward the efficient direct regeneration of spent cathode materials through the effect of residual sodium ions analysis

Recycling spent lithium-ion batteries is an important means for promoting sustainability within the energy industry. In this study, the effects of residual sodium on the regeneration process and the performance of spent LiNi_0.5Co_0.2Mn_0.3O₂ were explored. An appropriate amount of residual sodium was found to improve the properties of the regenerated material, with the best cycle performance and rate performance at a residual sodium of 3 mol %. The first-cycle and 100-cycle discharge capacities were 136.4 mA h g^-1 and 120 mA h g^-1, respectively, with a capacity retention rate of 87.98% after 100 cycles at a rate of 1 C. The electrochemical performance of the regenerated cathode materials was improved because sodium occupied the lithium sites in the crystal structure, providing a channel for lithium deintercalation. These results indicate that the residual sodium ions should be monitored in appropriate quantities to improve the efficiency of recycling spent lithium-ion batteries.