Chemo-Mechanical Characterization of V2O5 Single Crystals via Nanoindentation and In Situ Lithiation

Certain single-crystal materials have shown great promise as next-generation cathodes of lithium-ion batteries due to their high energy density and structural stability. However, single-crystals have anisotropic mechanical, electrochemical, and transport properties that can affect the performance and durability of the battery that must be careful characterized. Furthermore, the impact of mechanical defects, such as cracks, dislocations, twin boundaries, residual lattice stress, and residual lattice strain remains poorly understood and could result in decreased performance during electrochemical cycling. This study aims to provide such understanding in V2O5 single crystals of different phases (alpha, zeta, and gamma) by probing chemo-mechanical interactions during lithiation/delithiation.<br/><br/>Specifically, this study first characterized nano-scale mechanical properties of these single crystals, including hardness, elastic modulus, and fracture toughness, using Berkovich nanoindentation and micro-pillar compression. Additionally, scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and focused ion beam (FIB) sectioning were implemented to capture details of crystal reorientation, texture evolution, and stress-induced lattice rotation associated with the nanoindentation process. This study also explored the impact of plastic deformation (accomplished via nanoindentation) on chemical lithiation/delithiation of the V2O5 single crystals through in-situ optical microscopy and RAMAN spectroscopy. Finally, SEM, FIB, and EBSD were utilized to analyze the interactions between lithiation-induced effects and the defects and plastic zones caused by previous loading (via nanoindentation).