The hydrothermal synthesis of single-crystalline β-MnO2 nanorods and their chemical conversion into single-crystalline LiMn2O4 nanorods by a simple solid-state reaction were reported. This method has the advantages of producing pure, single-phase and crystalline nanorods. The LiMn2O4 nanorods have an diameter of about 300 nm. The discharge capacity and cyclic performance of the batteries were investigated. The LiMn2O4 nanorods show better cyclic performance with a capacity retention ratio of 86.2% after 100 cycles. Battery cyclic studies reveal that the prepared LiMn2O4 nanorods have high capacity with a first discharge capacity of 128.7 mA·h/g.