Utilization of Al₂O₃Atomic Layer Deposition for Li Ion Pathways in Solid State Li Batteries

Limited interfacial contact area between active material and solid state electrolyte (SSE) in solid state lithium batteries (SSLBs) can be addressed by utilizing a thermally treated Al2O3 atomic layer deposition (ALD) coating as a lithium ion transport pathway. SSLBs with a LiCoO2/Li3.15Ge0.15P0.85S4/77.5Li2S-22.5P2S5/Li configuration were built and tested using charge-discharge cycles between 3.3 ∼ 4.3 V (vs. Li/Li+) at a current density of 45 μA cm−2. An increase of more than 10% in the inital discharge capacity as well as good cycling stability are achieved from SSLBs using LiCoO2 particles coated with 2 and 4 cycles of Al2O3 ALD. The dQ/dV analysis, electrochemical impedance spectroscopy (EIS), and the overpotential study with galvanostatic intermittent titration technique (GITT) were conducted to elucidate the enhancement of Li+ transport through Al2O3 ALD layers surrounding LiCoO2.