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Abstract BackgroundMechanical degradation of electrodes driven by electrochemical reactions limits battery performance and longevity. While various microstructures of LiNi_xMn_yCo_zO₂(NMC) cathodes have been developed, their comparative mechanical properties and chemomechanical degradation are unknown. ObjectiveThis study measures the mechanical properties of NMC cathode particles of three different microstructures: gravel-type NMC of large grains, gravel NMC of small grains, and rod-shaped NMC. Damage evolution in the NMC particles is simulated using finite element modeling. MethodsWe use flat punch indentation to measure the particle strength, contact modulus, and fracture energy of NMC particles of different microstructures. We also assess the effect of voids on the mechanical properties and damage generation in NMC particles upon cycles. ResultsThe particle strength dictated by grain boundaries is measured to be ~ 200 MPa in the three NMC microstructures. The contact modulus changes nonlinearly during mechanical load. The fracture energy of gravel NMC particles is ~ 0.5 J/m². The presence of voids compromises the mechanical properties of NMC particles, but it helps delocalize stress within the particles and reduces damage generation upon electrochemical cycles. ConclusionsThe combined experiments and modeling provide a comprehensive analysis of the mechanical behaviors and their implications on chemomechanical degradation of NMC cathode particles of various microstructures. 

Morphology control is a key design parameter for sodium-ion layered oxide cathodes, yet achieving uniform precursors with balanced stoichiometry is more challenging than in lithium-ion systems due to the broader range of transition-metal chemistries involved. These complexities highlight the need for systematic comparisons of coprecipitation routes tailored to sodium-ion compositions. Here, we examine how ammonia- and citrate-based coprecipitation methods shape the morphology and composition of equimolar Ni–Fe–Mn hydroxide and oxyhydroxide precursors. We investigate how pH, ligand concentration, and temperature jointly influence precipitation onset, particle shape, and metal incorporation. In the ammonia system, precipitation proceeds readily between pH 10.5–11.5, with pH ≈ 11.0 yielding the most uniform morphology and target Ni:Fe:Mn ≈ 1:1:1 stoichiometry. Higher ammonia levels improve morphology but above ∼1.0 M begin to delay Ni incorporation and introduce phase separation. In contrast, the citrate system shows delayed precipitation (threshold pH ≈ 11.8) but forms dense granular microspheres with narrow size distributions across 0.1–0.6 M citrate, with Fe enrichment emerging at higher ligand concentrations. X-ray diffraction revealsβ-Ni(OH)₂-type hydroxides for ammonia-derived precursors andδ-FeOOH-type oxyhydroxides for citrate-derived ones. Together, these results provide practical guidance for tailoring precursor morphology and composition in Fe- and Mn-rich sodium-ion cathode materials. 

The mechanistic pathways of the high-temperature calcination reaction in a sodium-ion layered oxide, along with its synthesis-microstructure-performance relationship are investigated.