Microstructure–Driven Degradation Mechanisms in High-Nickel NMC Cathodes for Lithium-Ion Batteries
Year: 2026
Type: preprint
Abstract: Mechanical degradation in high-nickel layered oxide cathodes is closely associated with anisotropic lattice-parameter changes during electrochemical cycling, yet how cathode microstructure size influences the resulting crystallographic deformation remains poorly understood. Here, we investigate two LiNi0.90Mn0.05Co0.05O2 (NMC955) cathodes with comparable secondary-particle sizes but different average grain sizes (1.0 and 0.5 µm). The fine-grained cathode delivers 30% higher initial discharge capacity, 40% lower voltage polarization, improved rate capability, and 13% higher capacity retention after 100 cycles. Despite its superior electrochemical performance, the fine-grained material exhibits approximately 1.23 times higher mean kernel average misorientation after 100 cycles, together with higher estimated geometrically necessary dislocation density, indicating greater average local lattice curvature. The coarse-grained cathode shows pronounced localization of crystallographic misorientation near grain boundaries and secondary-particle peripheries, whereas the fine-grained cathode exhibits a more spatially distributed misorientation response. Complementary chemo-mechanical simulations reproduce the grain-size-dependent trends in lattice curvature and reveal differences in the spatial distribution of plastic strain associated with the different grain sizes. After 100 cycles, the coarse-grained cathode undergoes extensive intergranular cracking and secondary-particle fragmentation, while the fine-grained cathode largely preserves its structural integrity. These findings identify the spatial localization of cycling-induced crystallographic misorientation, rather than its average magnitude alone, as a pivotal variable for electrode design.
Source: ChemRxiv
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
Awards: G1341527534, G1735187872
OpenAlex ID: W7221803984