Cycling-induced　cathode　interfacial　degradations　are　usually　attributed　to　chemical　process,　while　the　physical　effect　is　overlooked　to　a　large　extent.　Herein,　we　investigate　the　failure　mechanism　of　LiCoO2　cathode　and　reveal　that　misfit　strain　plays　a　dominant　role　in　the　surface　layer　exfoliation　process.　We　illustrate　that　highly　strained　LiCoO2　surface　can　initiate　massive　surface　cracks,　leading　to　the　LiCoO2　surface　layer　broken　and　exfoliation.　Mechanical　cracking　coupled　with　chemical　etching　aggravates　the　surface　layer　degradation,　leading　to　a　weathering-like　degradation　on　LiCoO2　surface.　Our　work　reveals　that　interfacial　degradation　of　electrode　materials　is　a　complex　physicochemical　process.　[GRAPHICS]　.