Construction of Sulfone‐Based Polymer Electrolyte Interface Enables the High Cyclic Stability of 4.6 V LiCoO 2 Cathode by In Situ Polymerization

Lithium cobalt oxide (LiCoO 2 ) 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 LiCoO 2 and the electrolyte occur, which adversely impact the battery's cycle performance. The surface‐related issues of LiCoO 2 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 LiCoO 2 from direct contact with the electrolyte. The exploration of novel surface protection strategies for LiCoO 2 remains imperative to address the associated challenges. Herein, introducing a sulfone‐based polymer electrolyte interface is proposed on the surface of LiCoO 2 using methyl vinyl sulfone (MVS) through in situ polymerization. Remarkably, LiCoO 2 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 LiCoO 2 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 LiCoO 2 but also improves its thermal stability. This work presents novel research perspectives for exploring high‐voltage stable LiCoO 2 .