Dopant Segregation Boosting High‐Voltage Cyclability of Layered Cathode for Sodium Ion Batteries

Abstract

As a widely used approach to modify a material’s bulk properties, doping can effectively improve electrochemical properties and structural stability of various cathodes for rechargeable batteries, which usually empirically favors a uniform distribution of dopants. It is reported that dopant aggregation effectively boosts the cyclability of a Mg‐doped P2‐type layered cathode (Na0.67Ni0.33Mn0.67O2). Experimental characterization and calculation consistently reveal that randomly distributed Mg dopants tend to segregate into the Na‐layer during high‐voltage cycling, leading to the formation of high‐density precipitates. Intriguingly, such Mg‐enriched precipitates, acting as 3D network pillars, can further enhance a material’s mechanical strength, suppress cracking, and consequently benefit cyclability. This work not only deepens the understanding on dopant evolution but also offers a conceptually new approach by utilizing precipitation strengthening design to counter cracking related degradation and improve high‐voltage cyclability of layered cathodes.Improved cyclability of Mg‐doped P2‐NMM layered cathode is mainly due to suppression of cracking. Randomly distributed Mg dopants tend to segregate into precipitates during high‐voltage cycling, which can further strengthen the layered cathode and suppress cracking, leading to superior cycling stability at elevated voltage. Dopant precipitate is a new design concept to improve layered cathode cyclability.