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/Li3.15Ge0.15P0.85S4/77.5Li(2)S-22.5P(2)S(5)/Li configuration were built and tested using charge-discharge cycles between 3.3 similar to 4.3 V (vs.Li/Li+) at a current density of 45 mu A 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. (C) 2014 The Electrochemical Society. All rights reserved.