Practical Multiphase Transition Kinetics in High-Energy-Density Layered Cathodes

Deciphering the interplay between thermodynamics and kinetics in phase transitions is crucial for the development of high-energy-density Li-ion batteries. However, the microscopic reaction dynamics in practical electrodes, particularly under nonequilibrium conditions, remain elusive. Here, we develop a multiphase transition kinetics framework to elucidate the electrochemical behavior of highly delithiated Ni-rich cathodes. We reveal that the localized degraded domains serve as "phase walls", dynamically steering the evolution of active phases through interfacial mechanical interactions. These phase walls directly control the interplay between the thermodynamically favored phase separation and the kinetically driven solid-solution behavior during the nominal H2-H3 phase transition. Such a fundamental modulation of the reaction pathway is the underlying cause of long-standing challenges, including charge-discharge asymmetry, sluggish kinetics, and progressive capacity fade. Our findings highlight interfacial mechanics as a critical yet underexplored lever in microstructural engineering, offering new design principles for next-generation high-energy-density layered cathodes.