Novel Thin-Film Solid Nanocomposite Electrolyte for Lithium-Ion Batteries by Combined MLD and ALD

This work reports on the first thin-film solid nanocomposite electrolyte (NCE) for lithium-ion batteries made by combining two gas-phase deposition techniques, molecular layer deposition (MLD) and atomic layer deposition (ALD). The advantage of using these techniques for the fabrication of NCEs comes from the ease of integration in thin-film batteries and the possibility to alter the properties of the oxide matrix and of the Li-compound independently. Moreover, the mesoporous oxide matrix based on an MLD and etching process, provides uniform interfaces with continuous conduction paths. An enhancement in Li-ion conductivity of two orders of magnitude, compared to the pure Li-compound, is obtained for an NCE consisting of a mesoporous Al2O3 matrix filled with Li2CO3. The impact of the oxide matrix on the resulting NCE Li-ion conductivity is considerable, showing four orders of magnitude difference between silica and alumina. Finally, integration of the NCE in a thin-film solid-state battery stack utilizing a Li-metal anode is demonstrated with good coulombic efficiency over a broad temperature range. The current findings and approach can expand the possibilities for development of novel thin-film solid-state electrolytes.