Unusual Site-Selective Doping in Layered Cathode Strengthens Electrostatic Cohesion of Alkali-Metal Layer for Practicable Sodium-ion Full Cell.

P2-type Na0.67 Ni0.33 Mn0.67 O2 is a dominant cathode material for sodium-ion batteries (SIBs) due to its high theoretical capacity and energy density. However, charging P2-type Na0.67 Ni0.33 Mn0.67 O2 to voltages higher than 4.2 V versus Na+ /Na could induce detrimental structural transformation and severe capacity fading. Herein, we achieve stable cycling and moisture resistancy of Na0.67 Ni0.33 Mn0.67 O2 at 4.35 V (versus Na+ /Na) through dual-site doping with Cu ion at transition metal site (2a) and unusual Zn ion at Na site (2d), for the first time. The Cu ion doping in 2a site stabilizes the metal layer, while more importantly, the unusual alkali-metal site doping by Zn ion serves as O2- -Zn2+ -O2- "pillar" for enhancing electrostatic cohesion between two adjacent transition metal layers, preventing the crack of active material along a-b plane and restraining the generation of O2 phase upon deep desodiation. This unique dual-site doped [Na0.67 Zn0.05 ]Ni0.18 Cu0.1 Mn0.67 O2 cathode exhibits a prominent cyclability with 80.6% capacity retention over 2000 cycles at an ultrahigh rate of 10C, demonstrating its great potential for practical applications. Impressively, the full cell devices with [Na0.67 Zn0.05 ]Ni0.18 Cu0.1 Mn0.67 O2 and commercial hard carbon as cathode and anode, respectively, can deliver a high energy density of 217.9 Wh kg-1 and excellent cycle life over 1000 cycles. This article is protected by copyright. All rights reserved.