Quantifying Lattice–Crack–Electrochemical Transport Coupling for Durable, Fast‐Charging Battery Cathodes

ABSTRACT Single‐crystal (SC) cathodes have rapidly emerged as a transformative architecture in next‐generation lithium‐ion batteries, offering superior structural stability and extended cycle life by eliminating intergranular boundaries. Yet a critical question remains—can single‐crystal particles truly match the fast‐charging performance of polycrystalline (PC) cathodes which continue to dominate commercial batteries due to their high tap density and ease of synthesis? The answer has remained elusive because the quantitative roles of grains, grain boundaries, and cracks in Li + transport are not fully understood. Here, a unified quantitative framework is established that links apparent diffusivity and exchange current density to crack‐generated interfaces under near‐surface diffusion conditions. Applied to compositionally identical SC‐ and PC‐NMC811 and integrated with ab initio calculations, machine‐learning molecular dynamics, and finite‐element fracture modeling, this framework reveals identical intrinsic lattice and interfacial kinetics prior to cracking. The apparent kinetic advantage of PC arises from electrolyte infiltration into intergranular cracks that both create new electrochemically active interfaces and shorten diffusion pathways. Particle size–rate modeling, validated experimentally, further demonstrates that downsized SC particles can achieve PC‐like fast‐charging performance while retaining mechanical integrity. These findings quantitatively resolve the long‐standing SC–PC rate paradox and provide mechanistic guidance for designing durable, high‐rate cathodes.