One-Step Surface-to-Bulk Modification of High-Voltage and Long-Life LiCoO 2 Cathode with Concentration Gradient Architecture.

Raising the charging cut-off voltage of layered oxide cathodes can improve their energy density. However, it inevitably introduces instabilities regarding both bulk structure and surface/interface. Herein, exploiting the unique characteristics of high-valance Nb 5+ element, we achieved a synchronous surface-to-bulk modified LiCoO 2 featuring Li 3 NbO 4 surface coating layer, Nb-doped bulk, and the desired concentration gradient architecture through one-step calcination. Such a multifunctional structure facilitates the construction of high-quality cathode/electrolyte interface, enhances Li + diffusion, and restrains lattice-O loss, Co migration and associated layer-to-spinel phase distortion. Therefore, a stable operation of Nb-modified LiCoO 2 half-cell is achieved at 4.6 V (90.9% capacity retention after 200 cycles). Long-life 250 Wh/kg and 4.7 V-class 550 Wh/kg pouch-cells assembled with graphite and thin Li anodes are harvested (both beyond 87% after 1600 and 200 cycles). This multifunctional one-step modification strategy establishes a technological paradigm to pave the way for high-energy density and long-life lithium-ion cathode materials. This article is protected by copyright. All rights reserved.