Low‐Electronegativity Cationic High‐Entropy Doping to Trigger Stable Anion Redox Activity for High‐Ni Co‐Free Layered Cathodes in Li‐Ion Batteries

Abstract

Abstract LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM‐811) exhibits the highest capacity in commercial lithium‐ion batteries (LIBs), and the high Ni content (80 %) provides the only route for high energy density. However, the cationic structure instability arisen from the increase of Ni content (>80 %) limits the further increase of the capacity, and inevitable O 2 release related to anionic structure instability hinders the utilization of anion redox activity. Here, by comparing various combinations of high‐entropy dopants substituted Co element, we propose a low‐electronegativity cationic high‐entropy doping strategy to fabricate the high‐Ni Co‐free layered cathode (LiNi 0.8 Mn 0.12 Al 0.02 Ti 0.02 Cr 0.02 Fe 0.02 O 2 ) that exhibits much higher capacity and cycling stability. Configurational disorder originated from cationic high‐entropy doping in transition metal (TM) layer, anchors the oxidized lattice oxygen ((O 2 ) n− ) to preserve high (O 2 ) n− content, triggering the anion redox activity. Electron transfer induced by applying TM dopants with lower electronegativity than that of Co element, increases the electron density of O in TM‐O octahedron (TM‐O 6 ) configuration to reach higher (O 2 ) n− content, resulting in the higher anion redox activity. With exploring the stabilization effect on both cations and anions of high‐entropy doping and low‐electronegativity cationic modified anion redox activity, we propose an innovative and variable pathway for rationally tuning the properties of commercial cathodes.