Manganese dioxide/cabon nanotubes (MnO2/CNTs) composites with tunable density of MnO2 nanosheets on the surface of CNTs were synthesized by a facile room temperature solution method. When applied in lithium-ion batteries (LIBs) as anode materials, the spacial density of MnO2 nanosheets in the MnO2/CNT composite was verified to be crucial for the lithium storage performance. The optimized composite with moderate spatial density of MnO2 nanosheets delivered a reversible capacity of 903mAhg−1 at the current rate of 0.24Ag−1. Moreover, this composite exhibited a high stable capacity of 540mAhg−1 even at a high current density of 2.4Ag−1 after 1500 cycles, demonstrating its potential for applications in LIBs with long cycling life and high power density. The enhanced electrochemical performance of the optimized composite was ascribed to sufficient space between the MnO2 nanosheets on the CNTs, which not only allows the effective electrical contact between the CNT backbones and the conductive carbon but also accommodates the large volume changes upon repeated lithiation/delithiation.