Durable Potassium Storage Achieved by Boron Coordination in a P2-Type Layered Oxide Skeleton

Layered transition-metal (TM) oxides are of high application value as a cathode for potassium (K)-ion batteries toward high energy density. However, the inadequate covalency of the TM–O bond inevitably induces TM migration and subsequent irreversible structural transformation upon operating, which results in poor rate and long cycle reliability. To address this issue, we employed boron coordination chemistry to manipulate the local electronic structure in a prototype P2-layered K_0.5Mn_0.8Ni_0.15B_0.05O₂ (KMNBO). The B ions with high electronegativity reside in the TM slabs to boost TM–O covalency of the layered cathode by attracting an electronic tendency surrounding oxygen, which upgrades the tolerance of the layered structure during the repeated K-ion (de)intercalation process. The sluggish intrinsic K⁺ migration could be simultaneously alleviated by reducing the Coulomb force between K and O. This study breaks the stereotype for a layered crystal lattice and provides new insight into developing long-durability potassium layered cathodes.