Enhancing the Integral Structural and Thermal Stability of Ultrahigh-Ni Cathodes via Morphology Refinement and In Situ Interfacial Engineering

Abstract

Nickel-rich layered oxides are promising cathodes in commercial materials for lithium-ion batteries. However, the increase of the nickel content leads to the decay of cyclic performance and thermal stability. Herein, in situ surfacefluorinated W-doping LiNi 0.90 Co 0.05 Mn 0.05 O 2 cathodes enhance integral lithium-ion migration (transfer in bulk and diffusion in the interface) kinetics by synergistically solving the problems of bulk and interface structural degradation. Owing to the introduction of tungsten, the growth of primary particles is regulated toward the (003) crystal plane and with the acicular structure, which further stabilizes the bulk structure during cycling. Moreover, the LiF coating layer on the cathode/electrolyte interface physically isolates the attack of the electrolyte on the surface cathodes and accelerates the lithium-ion diffusion rate, ultimately ameliorating the interfacial dynamics and structural stability. Dual-modified LiNi 0.90 Co 0.05 Mn 0.05 O 2 exhibits superior electrochemical properties, especially more remarkable cyclic retention (88.16% vs 70.44%) after 100 cycles at 1 C and more outstanding high current rate properties (173.31 mAh•g −1 vs 135.97 mAh•g −1 ) at 5 C than the pristine one. This work emphasizes the probability of an integrated optimization strategy for Ni-rich materials, which provides an innovative idea for ameliorating (bulk and interfacial) structure degradation and promoting the diffusion of lithium ions during cycling.

Regulating the Charge Distribution of Oxygen by High-Entropy Doping to Stabilize Single-Crystal Ni-Rich Cathode Materials

“…The HE811 cathode (269.82 °C) exhibits a delayed exothermic peak compared to the single-crystal 811 cathode (261.41 °C), indicating that the strong TM–O bond elements introduced by high-entropy doping could improve the thermal stability of the material. The thermal stability of the Ni-rich cathode has always been a major obstacle in the practical application process due to highly oxidizing Ni 4+ and the release of oxygen in the delithiation state . The reduced TM–O bonding energy in cathode materials leads to a decrease in the phase transition temperature during thermal decomposition of the layered-spinel-rock salt structure, which exacerbates gas production and raises safety concerns. , The oxygen atoms with a consistent chemical coordination environment were selected for density functional theory calculations (Figure b,c).…”

Understanding the Effects of Bi Modification on the Properties of Ni‐Rich Cathodes

“…The seriously destroyed layer structure is due to the phase transition from H2 to H3, and the well-maintained layer structure in 1BiNMC is primarily attributed to the stronger TMÀ O bonds resulting from the substitution of Bi ions into Ni sites, which stabilizes the structure and inhibits the phase transition from H2 to H3 in a highly delithiated state. [15,17,43] Moreover, large number of cracks can be found on VNMC after 100 cycles while cracks are hardly observed on 1BiNMC, as shown in Figure 6g, 6h, S10c, and S10d. The obvious difference also can be attributed to the Bi 2 O 3 coating which can effectively prevent limit the corrosion and damage from electrolyte.…”

“…[14,15] Different modification strategies have been employed to improve the structure stability, like controlling the exposed facets and morphology of primary particles, optimizing the solid electrolyte interphase (SEI), and synthesizing single crystal shapes. [16][17][18] Doping and coating are the most popular modification strategies because they are significantly effective and can be simply achieved during synthesis process. [19][20][21] Zhou et al proposed that Bi 2 O 3 at surface can hinder the migration of oxygen ion vacancies and reduce the irreversible loss of oxygen and thus optimize the structure stability and improve Li + diffusion of Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 , achieving high cycle and rate capability.…”

Unveiling Morphology and Crystallinity Dynamics in NixMn1–xCO3 Cathode Precursors through Batch-Mode Coprecipitation

“…Understanding and controlling the morphology of particles produced through coprecipitation in batch mode is essential for comprehending the synthesis parameters that influence the particle morphology and characteristics. Crystallinity and the morphology/size of primaries are important parameters for cathodes and are known to influence electrochemical performance. ,− A deep, comprehensive, and fundamental understanding of synthetic mechanisms and kinetics will be helpful for further optimization and better control of the processing and more effectively fine-tuning methodologies, ensuring desired morphology and ultimately leading to enhancements in the final product’s performance and consistency. In this study, the aim is to explore the coprecipitation processes employed in synthesizing the more complex, Ni-containing carbonate cathode precursors, focusing on the evolution of crystalline structures, TM distribution, and morphological attributes during synthesis as well as the impact on particle morphology of x in Ni x Mn 1– x CO 3 .…”