Li2MnO3 film synthesized on SrTiO3 substrate with SrRuO3 buffer layer using pulsed laser deposition has demonstrated a high initial charge-discharge capacity. It has been found that the Li2MnO3 crystals were composed of nano-domains with 5 nm in size, which followed a dominant orientation relationship (OR) with respect to the SrRuO3 crystals at the Li2MnO3/SrRuO3 interface. The domain size is in agreement with the calculated critical size, which is determined by the elastic strain originated from the lattice mismatch at the Li2MnO3/SrRuO3 interface. We proposed that the high initial charge-discharge capacity of the Li2MnO3 film is due to the combined effects of (1) being able to release the lattice strain at the Li2MnO3 domain boundaries during (de) intercalation of Li-ions that causes lattice expansion and shrinkage, and (2) crystal structure of the nano-domains and their ORs with respect to the SrRuO3 crystals being well-maintained due to the above strain release. In addition, our observation confirmed the existence of anti-phase domain boundaries and stacking faults in the Li2MnO3 crystals. However, it is considered that their influences on the (de) intercalation of Li-ions are not significant, because these defects do not obstruct the conduction paths of Li atoms that are orderly arranged in the c-planes. (C) The Author(s) 2018. Published by ECS.