Energy storage technologies are required to ensure stability of energy systems when the share of renewable energy forms (wind and solar) is increasing. Liquid air energy storage (LAES) is a promising technology for storing electricity with certain advantages, such as high energy density and being geographically unconstrained. However, one drawback of a standalone LAES is the relatively low round-trip efficiency (RTE). In this work, the performance of a standalone LAES system with different number of compression and expansion stages is studied. All cases are optimized by using a particle swarm optimization (PSO) algorithm. The optimal results show that the highest RTE of 66.7% is obtained when there is a 2-stage compressor and a 3-stage expander in the LAES system. When the number of compression stages is fixed, the highest RTE is obtained when hot and cold streams have close to parallel temperature profiles in the preheaters of the expansion section.