Electrochemically Tuned Crystal Tectonics in Crack-Resistant Textured Oxide Cathode Films for Electrochemical Energy Storage

Electro-chemo-mechanical degradation pathways that significantly impact performance of ceramic battery electrodes are a strong function of bulk crystallographic texture, crystal size, and interfacial misorientation angle. Via electrodeposition, deterministic synthesis of textured thick (>10 μm) films of LiCoO₂ having controlled size dispersity and interfaces is demonstrated, enabling study and control of these degradation pathways. The crystal morphogenesis stems from the growth parameters (current density and temperature), resulting in a bouquet of textures and microstructures. Columnar grained ⟨110⟩||ND textured films with a finer crystallite size (<i>f</i>^{4-8 μm} = 0.617) can be synthesized in kinetic regimes of growth (<i>T</i> = 275 °C, supersaturation >0.367), whereas ⟨003⟩||ND films with coarser crystals (<i>f</i>^{8-15 μm} = 0.597) originate in thermodynamic regimes of growth (<i>T</i> = 350 °C, supersaturation independent). Interestingly, Σ3 coincident site lattice (CSL)/twin boundaries are controllably incorporated in the ⟨110⟩||ND films (<i>f</i> = 0.337), whereas ⟨003⟩||ND films only possesses high-angle crystal interfaces (HACIs, <i>f</i> = 1.0). The morpho-structural evolution of the crystal assembly under electro-chemo-mechanical stimuli is rooted in crystal tectonics and corelated anisotropic ionic diffusion differences. Stochastic analysis of microstructures of electrochemically cycled films via electron backscatter diffraction (EBSD) and Raman spectroscopy indicates interface-, size-, and texture-dependent degradation modes. On electrochemical cycling, the ⟨003⟩||ND electrode degrades by both intercrystal and intracrystal cracking (13.3% retention), whereas the ⟨110⟩||ND electrode is only susceptible to intercrystal cleavage (89.2% retention). The cracks initiate at local lithiation heterogeneities near coarser crystals and always propagate along HACIs, with all the CSL boundaries remaining mechanically robust. Our discoveries highlight how careful orchestration of orientation and interfaces leads to unique chemomechanical stabilization strategies.