Uniform pore structure enables negligible degradation in undoped and uncoated Ni-rich cathodes

Ni-rich layered oxide positive electrodes (cathodes) for lithium-ion batteries exhibit chemo-mechanical failures, with the consensus pointing to high-voltage phase transitions as the root cause. To mitigate these issues, compositional modifications (e.g., doping), nanostructuring (e.g., coatings and primary particle engineering), and microstructure modifications are well-established approaches rooted in hierarchal materials design, albeit increasing the synthesis complexity. Here, we demonstrate a simple synthesis strategy that enables exceptionally stable Ni-rich cathodes without doping, coating or concentration gradients. Through extensive multi-scale microscopy, we show that chemo-mechanical failure is closely linked to microstructural non-uniformity (specifically, nanoscale pores), stemming from limited physical contact between solid-state reactants during calcination. Simply by increasing the melting rate of LiOH, we enhance liquid-solid interfacial contact between precursors, resulting in uniformly evolved microstructures. This uniform microstructure leads to excellent cycle life by effectively dissipating strain energy and mitigating chemo-mechanical failure, surprisingly, even in the presence of the high-voltage phase transition. Our findings challenge the widely held belief that suppressing this phase transition and hierarchal material design are necessary for stable Ni-rich cathodes.