In this article, we report the effect of using nanoparticles for LiMn2O4 cathode materials in flexible batteries with organic-inorganic hybrid electrolytes. LiMn2O4 nanoparticles for the cathode are prepared by pyro-synthesis. Electrochemical measurement indicated the discharge capacities were 118.41 and 138.12 mA h g-1 and the coulombic efficiencies were 91.50% and 97.28% for the micro- and nano-LMO materials, respectively. This is attributed to the nano-LiMn2O4 material having particle sizes in the nanoscale dimension, and shorter diffusion paths combined with a large contact area at the electrode/ electrolyte interface. Furthermore, the pouch-type cells demonstrated similar properties, with initial discharge capacities of 85.63 and 99.96 mA h g-1 and coulomb efficiencies of 79.27% and 90.27% for the micro- and nano-LMO cells, respectively. Nanoparticles allow Li+ ions to de-intercalate and intercalate very easily because of the very short lithium diffusion distance.