Designing Battery Electrode Architectures Across Length Scales

The design and operation of rechargeable batteries is predicated on orchestrating flows of mass, charge, and energy across multiple interfaces. Understanding such flows requires knowledge of atomistic and mesoscale diffusion pathways and the coupling of ion transport with electron conduction. Using multiple polymorphs of V₂O₅ as model systems, I will discuss our efforts to develop an Ångstrom-level view of diffusion pathways. Topochemical single-crystal-to-single-crystal transformations provide an atomistic perspective of how diffusion pathways are altered by modification of V—O connectivity, pre-intercalation, and high degrees of lithiation. Recently devised multi-step synthetic schemes enable the positioning of Li-ions across four distinct interstitial sites of a V₂O₅ insertion host and allow for deterministic redirection of Li-ion flows through strategic positioning of transition-metal ions.<br/>At higher length scales, scanning transmission X-ray microscopy and ptychography imaging provide a means of mapping the accumulative results of atomic scale inhomogeneities at mesoscale dimensions and further enable tracing of stress gradients across individual particles. I will discuss strategies for the mitigation of diffusion impediments and degradation mechanisms based on controlling the coupling of chemistry, geometry, and mechanics. Some of these strategies include (a) utilization of Riemannian manifolds as a geometric design principle for electrode architectures; (b) atomistic design of polymorphs with well-defined diffusion pathways that provide frustrated coordination; and (c) site-selective modification as a means of tuning lattice incommensurability between lithiated and unlithiated phases.<br/>This research was funded by the National Science Foundation under DMR 1809866.