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Li and Mn-rich (LMR) layered oxide cathode materials can substantially increase battery energy density by facilitating both cation and anion redox energy. However, the cathode material suffers from continuous voltage decay over the charge/discharge cycles and results in capacity loss. Coherent X-ray Diffraction (CXD) techniques are invaluable for investigating the morphology, structural and strain information in crystalline specimens under in-situ and operando conditions [1-2]. In this presentation, Li_1.2Ni_0.13Mn_0.54Co_0.13O₂ is used as a benchmark to explore the origin of structural degradation in LMR cathode materials [3]. In-situ CXD techniques are used to visualize the strain accumulation in the charging process that leads to an abrupt oxygen loss to release the lattice strain. In the meanwhile, a new phase with a trace quantity is observed from the microbeam diffraction that supports the hypothesis of oxygen loss. These results highlight the significance of lattice strain in the voltage decay mechanism and will inspire a wave of efforts that seek novel solutions for eliminating this issue.

[1] Ian Robinson & Ross Harder, Nat. Mater. 8, 291–298 (2009)
[2] Luxi Li, Yingying Xie, Evan Maxey, & Ross Harder J. Synchrotron Rad. 26, 220-229 (2019).
[3] Tongchao Liu, Luxi Li, et al. Nature 606. 305-312 (2022).

Co-Author(s): Tongchao Liu (Argonne National Laboratory), Ian Robinson (Brookhaven National Laboratory), Ross Harder (Argonne National Laboratory), Wonsuk Cha (Argonne National Laboratory)

Luxi Li

Argonne National Laboratory

Appearances