Layered LiCoO2 (LCO) is one of the most important cathodes for portable electronic products at present and in the foreseeable future. It becomes a continuous push to increase the cutoff voltage of LCO so that a higher capacity can be achieved, for example, a capacity of 220 mAh g–1 at 4.6 V compared to 175 mAh g–1 at 4.45 V, which is unfortunately accompanied by severe capacity degradation due to the much‐aggravated side reactions and irreversible phase transitions. Accordingly, strict control on the LCO becomes essential to combat the inherent instability related to the high voltage challenge for their future applications. This review begins with a discussion on the relationship between the crystal structures and electrochemical properties of LCO as well as the failure mechanisms at 4.6 V. Then, recent advances in control strategies for 4.6 V LCO are summarized with focus on both bulk structure and surface properties. One closes this review by presenting the outlook for future efforts on LCO‐based lithium ion batteries (LIBs). It is hoped that this work can draw a clear map on the research status of 4.6 V LCO, and also shed light on the future directions of materials design for high energy LIBs.

Solid‐state batteries (SSBs) are promising for next‐generation energy storage with advantages in both energy density and safety, but are challenged by the poor solid‐to‐solid contact between solid‐state electrolytes (SSEs) and electrodes, particularly the lithium anode. Herein, a facile coordination‐assisted deposition process is employed to build artificial Ta2O5 nanofilms on SSEs, which is lithiophilic and has high stability against metallic lithium, thereby ensuring an intimate and stable interface between SSEs and lithium anode to sustain extended cycles. The feasibility is verified by using Li6.5La3Zr1.5Ta0.5O12 (LLZT), a garnet‐typed SSEs, as a model system. It is shown that a 12 nm Ta2O5 nanofilm is able to significantly decrease the interfacial resistance from 1258 to 9 Ω cm2 with a high critical current density reaching 2.0 mA cm−2 for the assembled symmetric cell, which shows an unprecedented capability to survive long‐term cycling over 5200 h. This control strategy is also able to enable the use of the commercialized cathode materials of LiFePO4 and LiNi0.83Co0.07Mn0.1O2 in SSBs with both high reversible capacity and cycling capability. The study opens up a research avenue for the delicately carved interlayers through a scalable and reliable manufacturing process which can accelerate the commercialization of SSEs.