Cobalt-free layered oxides have emerged as promising candidates for next-generation cathodes for lithium-ion batteries. However, implementation of these materials has been hindered by their low rate capability, structural instability, and rapid capacity decay during cycling. Recent studies have shown that introducing cation dopants into layered oxides can strongly improve their electrochemical properties, but the underlying atomic-scale mechanisms remain elusive. In this work, we use a combination of atomic-resolution scanning transmission electron microscopy and first-principle calculations to reveal the microscopic origin of enhanced electrochemical properties in LiNi0.5Mn0.5O2 doped with ∼1 atom % Mo. Our results indicate that the Mo dopant hinders Li+/Ni2+ cation mixing and suppresses detrimental phase transformations near the particle surface and at intragranular grain boundaries, which enhances the cathode’s reversible capacity and cycling stability. Overall, this work provides important insights on how cation doping affects the structure and electrochemical properties of layered oxide cathodes.

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