Nanoscale Interface Modification of LiCoO2by Al2O3Atomic Layer Deposition for Solid-State Li Batteries

Abstract

Cycle stability of solid-state lithium batteries (SSLBs) using a LiCoO₂ cathode is improved by atomic layer deposition (ALD) on active material powder with Al₂O₃. SSLBs with LiCoO₂/Li_3.15Ge_0.15P_0.85S₄/77.5Li₂S-22.5P₂S₅/Li structure were constructed and tested by charge-discharge cycling at a current density of 45 μA cm⁻² with a voltage window of 3.3 ∼ 4.3 V (vs. Li/Li⁺). Capacity degradation during cycling is suppressed dramatically by employing Al₂O₃ ALD-coated LiCoO₂ in the composite cathode. Whereas only 70% of capacity retention is achieved for uncoated LiCoO₂ after 25 cycles, 90% of capacity retention is observed for LiCoO₂ with ALD Al₂O₃ layers. Electrochemical impedance spectroscopy (EIS) and transmission electron microscopy (TEM) studies show that the presence of ALD Al₂O₃ layers on the surface of LiCoO₂ reduces interfacial resistance development between LiCoO₂ and solid state electrolyte (SSE) during cycling.