Ni-rich layered oxide cathodes for lithium-ion batteries exhibit chemomechanical failures, with the consensus attributing this to high-voltage phase transitions. Existing mitigation strategies rely on compositional modifications (for example, doping), nanostructuring (for example, coatings and primary-particle engineering) and microstructure modifications, but these approaches increase synthesis complexity. Here, we demonstrate a simple synthesis strategy that enables exceptionally stable Ni-rich cathodes without doping, coating or concentration gradients. We show that chemomechanical failure is closely linked to microstructural non-uniformity (specifically, nanoscale pores), stemming from limited contact between solid-state reactants during calcination. By increasing the LiOH melting rate, we enhance liquid–solid interfacial contact between precursors, resulting in uniformly evolved microstructures. This uniformity leads to excellent cycle life by dissipating strain energy and mitigating chemomechanical failure even in the presence of high-voltage phase transition. Our findings challenge the prevailing belief that suppressing this phase transition and hierarchal material design are necessary for stable Ni-rich cathodes.