Metal oxide nanostructures hold enormous potential for electrochemical applications. While thin films of polymer-modified metal oxide electrodes have been widely investigated, there have been a few studies on polymer-modified nanopowders. We report the synthesis of pure molybdenum trioxide (MoO3), pristine and aged nanobelts using hydrothermal method with poly(ethylene glycol) (PEG). Scanning electron microscope (SEM) images reveal the nanobelts to have dimensions of 1–5μm in length and 100–600nm in diameter. The electrochemical measurements show that PEG-used aged MoO3 nanobelts have higher specific charge capacity than the PEG-free MoO3 and PEG-used pristine MoO3 nanobelts.