Charge Distribution Guided By Grain Crystallographic Orientations in Polycrystalline Battery Materials

Abstract

Charge propagation and distribution determine the electronic, mechanical, and thermal properties of polycrystalline battery materials. There has been rapidly growing research interest to engineer the grain crystallographic orientation to modulate the charge distribution and chemomechanical properties for enhancing the cycle life, safety, and energy density of alkali metal ion batteries. However, establishing the relationship between charge distribution and grain crystallographic orientation remains a daunting challenge. In this work, we spatially measure the charge distribution in nickel-rich Li layered oxides as a function of the grain crystallographic orientation and establish a model to quantify the charge heterogeneity in the polycrystalline secondary particles. While the holistic “shrinking-core” charge propagation prevails in polycrystalline layered oxide particles, the orientation-guided charge propagation governs the charge distribution in local nanodomains. Compared to the randomly orientated grains, the radially aligned grains create less tortuous Li ion pathways, which improves the charge homogeneity as statistically quantified from over 20 million nanodomains, thus allowing for lower voltage hysteresis and higher capacity retention upon battery cycling. Our results suggest that tuning the grain crystallographic orientation may mitigate the stress buildup in secondary particles and increase the active particle utilization in practical batteries. The present study provides a fundamental guidance for managing the chemomechanical properties of polycrystalline battery materials through engineering the grain crystallographic properties.