CO3O4 as anode material for thin film micro-batteries prepared by remote plasma atomic layer deposition

Cobalt oxide thin films have been deposited with remote plasma atomic layer deposition (ALD) within a wide temperature window (100–400 °C), using CoCp2 as cobalt precursor and with a remote O2 plasma as oxidant source. The growth rate was relatively high at 0.05 nm per ALD-cycle and resulted in the deposition of high density (~5.8 g cm-3), stoichiometric Co3O4. For the electrochemical analyses, Co3O4 was deposited on a Si substrate covered with an ALD-synthesized TiN layer to prevent Li diffusion. The as-deposited electrodes were investigated in a three-electrode electrochemical cell using constant current (CC) charge/discharge cycling and Galvanostatic Intermittent Titration Technique (GITT) in combination with Electrochemical Impedance Spectroscopy (EIS). Compared to the literature, ALD-deposited Co3O4 exhibited a high electrochemical activity (~1000 mAh g-1) and the formation of a solid electrolyte interface has been identified by EIS.