Li/Ni Intermixing: The Real Origin of Lattice Oxygen Stability in Co‐Free Ni‐Rich Cathode Materials

Abstract

The Co‐free Ni‐rich layered cathode materials with excellent structural stability and low‐cost in Ni‐rich family are emerging as the promising candidates for the next generation of high‐energy density cathodes. Previously, Mn is generally regarded as the structural stabilizer in Co‐free Ni‐rich cathodes, while the role of inevitable Li/Ni intermixing is underestimated. Herein, the study reveals that the real origin of the lattice oxygen/structure stability of Co‐free Ni‐rich cathodes is dominated more by Li/Ni intermixing than the widely accepted Mn. In the Li/Ni intermixing configuration, the intermixed Ni ions can suppress the oxidation of lattice oxygen by increasing the formation energy of oxygen vacancy and reducing charge compensation. Besides, the Li vacancy formed via the delithiation of intermixed Li in transition metal layer can serve as O2 capture sites. This dual stabilization mechanism is proposed and proved to be effectively in enhancing the reversibility of lattice oxygen and the stability of material structural. This work sheds light on the mechanism of stabilizing lattice oxygen through Li/Ni intermixing, which provides new insights for designing better batteries.

Constructing a Cr-Substituted Co-Free Li-Rich Ternary Cathode with a Spinel-Layered Biphase Interface

“…Owing to the mixing of Li and TM within the LRMO crystal structure, the intensity of the (003) crystal diffraction peak decreases, while that of the (104) peak increases. The calculated I (003) / I (104) value of Cr-LRMO is 1.3415, which is lower than that of Co-LRMO at 1.4649, which signified that adequate Li–Ni intermixing can reduce the diffusion barrier of Li + ions and help in the promotion of the rate capability. , Nonetheless, the I (003) / I (104) values of the two samples are still higher than 1.2, which suggests the small degree of cation mixing and the retention of a favorable lamellar structure. Moreover, a shift of the (003) peak to a lower angle is observed; it is probably because the ionic radius of the substitutional element Cr 3+ (0.615 Å) is larger than that of Co 3+ (0.545 Å) .…”

B/Al Codoped/Coated Ultra-High Nickel Cobalt-Free Material with Excellent High Voltage/Rate Cycle Stability

“…During the electrochemical cycle, the nickel ions of the high-nickel-layered oxide cathode material migrate from the TM octahedral to the lithium layer octahedral or vacancy tetrahedral, which is an irreversible phase transition from the layered structure to the spinel/rock salt structure. The oxidation of lattice oxygen is another important driver of the decline in the structural stability of high-nickel cathode material. − Therefore, it is very necessary to calculate the energy barrier for nickel migration to the lithium layer and oxygen vacancy formation energy to study in depth the impact of B/Al modification on the crystal structure stability of the NM90 material during charge and discharge. Based on the above analyses, all calculations in this study were implemented by the DFT method with a plane-wave basis set implemented in the Vienna Ab initio Simulation Package (VASP).…”

锂离子电池无钴高镍正极的研究进展

“…由于Ni含量的提高, 高镍正极往往表现出与LNO 正极相似的性质. Song等人 [18] 研究发现, 高镍正极 LiNi 0.9 Mn 0.1 O 2 的Li/Ni混排度高达6.7%. Liu等人 [19] 在 LiNi 0.6 Mn 0.4 O 2 和LiNi 0.6 Co 0.4 O 2 上都发现有氧气的释放.…”