Toward a Nanoscale‐Defect‐Free Ni‐Rich Layered Oxide Cathode Through Regulated Pore Evolution for Long‐Lifespan Li Rechargeable Batteries

Abstract

Ni‐rich layered oxides are envisioned as the most promising cathode materials for next‐generation lithium‐ion batteries; however, their practical adoption is plagued by fast capacity decay originating from chemo‐mechanical degradation. The intrinsic chemical–mechanical instability, inherited from atomic‐ and nanoscale defects generated during synthesis, is not yet resolved. Here, atomic‐ and nanoscale structural evolution during solid‐state synthesis of Ni‐rich layered cathode, Li[Ni0.92Co0.03Mn0.05]O2, is investigated using combined X‐ray/neutron scattering and electron/X‐ray microscopy. The multiscale analyses demonstrate the intertwined correlation between phase transition and microstructural evolution, with atomic‐scale defects derived from the decomposition of precursors leading to the creation of intra/inter‐granular pores. The nucleation and coalescence mechanism of pore defects during the synthesis of Ni‐rich layered cathodes are quantitatively revealed. Furthermore, a modified synthetic route is proposed to effectively circumvent the formation of nanoscale defects in Ni‐rich layered cathodes by facilitating uniform synthetic reactions, resulting in superior electrochemical and microstructural stability.

Unveiling the Future of Li-Ion Batteries: Real-Time Insights into the Synthesis of Advanced Layered Cathode Materials

“…Tracking crystal structural changes within layered cathode materials synthesized using various approaches has been conducted through extensive ex situ diffraction analyses, combined with Rietveld refinements of powder diffraction patterns . The diffraction technique, a long-established method for identifying crystal structures, commonly utilizes XRD with X-rays sourced from both laboratory diffractometers and synchrotrons.…”

“…Synchrotron X-ray beams, characterized by high intensity and wide energy tunability, enable time-resolved in situ investigations that are crucial due to the nonequilibrium and complex nature of synthesis processes. , Diffraction data can be readily obtained in just a few minutes, offering comprehensive insights into phase transitions, atomic ordering, bond lengths, crystallite sizes, and microstrains throughout the synthesis process. Recent advances in laboratory X-ray diffractometers now enable the acquisition of structural information during synthesis. , However, these instruments frequently encounter data distortions due to reflection geometry, which can lead to peak shifts and a loss of peak intensity at low angles, often resulting from sample contraction or expansion at high temperatures. Moreover, these systems require longer data acquisition times, necessitating the careful design of experimental procedures.…”

“…The kinetic pathways for the synthesis of layered cathode materials vary considerably depending on metal composition (such as Ni, Mn, Co, and Al), − precursor types (like hydroxides and carbonates), , and synthetic procedures (such as heating rate, preaging steps, and cooling), ,, resulting in different intermediate phases during the early heating stage. Preferential oxidation of Co and Mn over Ni during this stage facilitates the formation of a spinel ( Fd3̅m ) phase in the synthesis of low-Ni layered cathode materials, specifically LiNi x Mn y Co 1‑ x ‑ y O 2 (where x < 0.6) and OLO, while a rock-salt ( Fm3̅m ) phase forms when x ≥ 0.6.…”

“…Several studies support this claim, indicating that using Li and TM carbonate precursors can lead to reaction heterogeneity during heating due to the formation of Li 2 CO 3 , resulting in poorer electrochemical performance . In contrast, using hydroxide precursors with a carefully regulated synthetic procedure and preaging steps can significantly affect the lithiation of intermediate phases, leading to superior electrochemical performance. , The electrochemical performance of layered cathode materials is strongly influenced by their reaction pathway during synthesis, making it crucial to characterize the phase fraction during the early stages of synthesis using diffraction analysis.…”

“…Reproduced with permission from ref Copyright 2018 The Electrochemical Society. (e) In situ SANS patterns during the synthesis of LiNi 0.92 Co 0.03 Mn 0.05 O 2 without and with preaging at 250 °C for 6 h. Reproduced with permission from ref Copyright 2024 John Wiley and Sons.…”