Cathodes of lithium-ion batteries (LIBs) present stability and performance issues, therefore, the search of new cathodes is still a major concern. Manganese dioxide in delta phase (δ-MnO₂) seems to be a suitable candidate since is low-cost, non-toxic and possesses a theoretical capacity of 308 mAhg⁻¹ for one-electron transfer. In this work, we prepared δ-MnO₂ by a hydrothermal method at two different reaction times. At 2 h, a flower-like nanostructure was obtained, while for a 3 h reaction time, a solid nanostructure was achieved. Both materials were tested as cathode in a LIB, finding that at slow charge-discharge rates (20 mAg⁻¹), a material with homogeneous nanosized morphology is enough in order to obtain good capacities. But, at higher rates, our flower-like structure provides a better discharge capacity.