Enhanced Cyclability of Cr(8)O(21) Cathode for PEO-Based All-Solid-State Lithium-Ion Batteries by Atomic Layer Deposition of Al(2)O(3)

Cr(8)O(21) can be used as the cathode material in all-solid-state batteries with high energy density due to its high reversible specific capacity and high potential plateau. However, the strong oxidation of Cr(8)O(21) leads to poor compatibility with polymer-based solid electrolytes. Herein, to improve the cycle performance of the battery, Al(2)O(3) atomic layer deposition (ALD) coating is applied on Cr(8)O(21) cathodes to modify the interface between the electrode and the electrolyte. X-ray photoelectron spectroscopy, scanning electron microscope, transmission electron microscope, and Fourier transform infrared spectroscopy, etc., are used to estimate the morphology of the ALD coating and the interface reaction mechanism. The electrochemical properties of the Cr(8)O(21) cathodes are investigated. The results show that the uniform and dense Al(2)O(3) layer not only prevents the polyethylene oxide from oxidization but also enhances the lithium-ion transport. The 12-ALD-cycle-coated electrode with approximately 4 nm Al(2)O(3) layer displays the optimal cycling performance, which delivers a high capacity of 260 mAh g(−1) for the 125th cycle at 0.1C with a discharge-specific energy of 630 Wh kg(−1).