Regulation of 3d‐Transition Metal Interlayered Disorder by Appropriate Lithium Depletion for Li‐Rich Layered Oxide with Remarkably Enhanced Initial Coulombic Efficiency and Stability

Abstract

Li‐rich materials are among the most promising cathode materials for lithium‐ion batteries thanks to their high specific capacity. However, they exhibit poor structural stability, resulting in low initial Coulombic efficiency and limited cycle stability. Herein, a long‐neglected Li‐deficient state is realized for a Co‐free lithium‐rich cathode through a facile calcination medium‐induced surface‐corrosion (CMISC) strategy for alleviating the aforementioned drawbacks. The as‐constructed Li‐deficient lithium‐rich cathode of Li1.2‐σMn0.6Ni0.2O2 (d‐LMNO) exhibits an enhanced capacity of 272 mAh g−1, improved initial efficiency of 84.5%, and cycle stability with 82.0% retention over 200 cycles. In addition, multiple in situ and ex situ investigations confirm the appropriate lithium depletion regulated 3d‐transition metal interlayered disorder, resulting in excellent structural reversibility of d‐LMNO. Also, theory simulations suggest that the crystal structure with Li‐defects has lower energy and Li‐diffusion energy barrier when the coordination interlayer 3d‐metal has more Ni closer to the diffused Li, meaning less interlayered disorder. And the migration of Li close to the vacancy is dominated by a tetrahedral site hopping path in the presence of additional vacancies around the Li vacancy, which has a low migration energy barrier. Moreover, similar results achieved in Co‐containing Li‐rich cathodes further demonstrate the universality of this simple CMISC strategy, exhibiting great potential for performance improvement and applicability.

Facile Morphology Modulation to Enhance Stability and Fast Kinetics of Anionic Redox for Li-Rich Layered Oxides Cathodes

“…In the O 1s XPS spectra (Figure 7), the main peaks located at around ∼529.5, ∼ 530.5, and ∼531.5 to 534 eV are attributed to lattice oxygen, (O 2 ) n− , and various organic products resulting from the decomposition of carbonate solvent. 37 Similar trends can be observed during the following charging process: As the voltage is charged to 4.6 V, the appearance of new peak (O 2 ) n− belongs to the characteristics of anionic redox chemistry (O 2− → (O 2 ) n− ). 37 The intensity of (O 2 ) n− increased at the 4.8 V charge state.…”

“…The mechanism of anionic redox for the three materials was further investigated to study the states of oxygen species through ex situ XPS measurements during the first charging and discharging process. In the O 1s XPS spectra (Figure ), the main peaks located at around ∼529.5, ∼ 530.5, and ∼531.5 to 534 eV are attributed to lattice oxygen, (O 2 ) n − , and various organic products resulting from the decomposition of carbonate solvent . Similar trends can be observed during the following charging process: As the voltage is charged to 4.6 V, the appearance of new peak (O 2 ) n − belongs to the characteristics of anionic redox chemistry (O 2– → (O 2 ) n − ) .…”

Semi‐Metallic Superionic Layers Suppressing Voltage Fading of Li‐Rich Layered Oxide Towards Superior‐Stable Li‐Ion Batteries

“…As depicted in Figure 2h, a stronger EPR signal is demonstrated of LRLO@LMO@LNO at g-factor 2.002, showing the presence of oxygen vacancies after modification, [12a] which altered the interaction between magnetic clusters and exhibited different EPR signal strengths. [29] This is unanimous with XPS results (Figure 2f). LRLO@LMO@LNO underwent XPS test at etching depths of 0, 3, 6 and 10 nm, as shown in Figure 2i.…”

Opportunities and Challenges of Layered Lithium-Rich Manganese-Based Cathode Materials for High Energy Density Lithium-Ion Batteries

“…At present, the migration of transition metal ions and the mixing of Li and transition metal (TM) during the first cycle are generally believed by researchers to be the main cause of capacity loss. 50 Another important factor causing capacity degradation in Li-rich manganese-based materials is the mixing of Li and TM when the voltage is higher than 4.5 V. The capacity degradation of Li-rich manganese-based materials occurs mainly in the first charge−discharge process. This process is mainly related to the irreversible deintercalation of ions.…”