Alternating Edge‐ and Face‐Sharing Octahedra with Partial Super‐Exchange Enabling High‐Voltage Layered Cathodes

Abstract

ABSTRACT Traditional O3‐type layered oxides with edge‐sharing (ES) octahedra suffer from structural instability under high‐voltage operation. To address this, we propose a stable edge‐sharing coplanar (ESC) O2‐type layered structure. In this structure, Li–O octahedra share edges on one side and faces on the other with Co–O octahedra. This ESC‐configuration effectively suppresses Co migration and enhances intrinsic structural stability. Furthermore, the 180°Ni–O–TM (TM = paramagnetic transition metal) super‐exchange interactions along the edge‐sharing directions are introduced to improve high‐voltage cycling stability. With an optimal amount of Ni, the unit‐cell volume expands, reducing the activation energy for Li‐ion diffusion. As a result, the modified ESC‐cathode delivers a high discharge capacity of 247 mAh g −1 and a capacity retention of 79% at 1 C after 100 cycles between 3.0 and 4.65 V, far exceeding that of conventional edge‐sharing LiCoO 2 (210 mAh g −1 , 26%). Interestingly, unlike in conventional edge‐sharing layered cathodes, where Ni contributes directly to capacity, increasing Ni content in ESC cathodes leads to a decrease in capacity because additional Ni ions enter the Li layer and obstruct Li‐ion diffusion pathways. Overall, this work presents an effective strategy for regulating the local coordination environment of layered oxide cathodes to achieve high performance.