Construction of Sulfone‐Based Polymer Electrolyte Interface Enables the High Cyclic Stability of 4.6 V LiCoO2 Cathode by In Situ Polymerization

Lithium cobalt oxide (LiCoO2) is considered an indispensable cathode material in the realm of consumer electronic batteries due to its high volumetric energy density. However, at a charging cut‐off voltage as high as 4.6 V, significant interfacial side reactions between LiCoO2 and the electrolyte occur, which adversely impact the battery's cycle performance. The surface‐related issues of LiCoO2 at high charge voltages not only constrain its utilization in conventional lithium‐ion batteries with liquid electrolytes but also limit its application in solid‐state batteries. Although traditional coating methods using inert inorganic compounds can partially alleviate this issue, their point‐like coatings fail to completely prevent the surface of LiCoO2 from direct contact with the electrolyte. The exploration of novel surface protection strategies for LiCoO2 remains imperative to address the associated challenges. Herein, introducing a sulfone‐based polymer electrolyte interface is proposed on the surface of LiCoO2 using methyl vinyl sulfone (MVS) through in situ polymerization. Remarkably, LiCoO2 with sulfone‐based polymer electrolyte interface exhibits a capacity retention rate of 83% after 500 cycles when employing a carbonate electrolyte without additives at a charge cut‐off voltage of 4.6 V. Furthermore, the LiCoO2 and polymer electrolyte interface exhibits exceptional cycle stability when paired with polyether solid electrolytes that do not possess high voltage tolerance. Moreover, the incorporation of a polymer electrolyte interface not only enhances the cycle stability of LiCoO2 but also improves its thermal stability. This work presents novel research perspectives for exploring high‐voltage stable LiCoO2. Increasing the operating voltage of lithium cobalt oxide (LiCoO2) can improve the energy density of the battery. In this work, a surface modification method of LiCoO2 suitable for both liquid battery and solid‐state batteries is introduced. A sulfone‐based polymer electrolyte interface introduced on the surface of LiCoO2 by in situ polymerization, which significantly improved the cycle stability.