The carbonized melamine foam (MF) was activated by niobium pentachloride (NbCl5) to enrich heteroatoms to obtain polyatomic doped melamine foam-based carbon sponges (NbNOCSs) by heat treatment. NbNOCSs have a good self-supporting three-dimensional network structure. They can be directly used as monolithic electrodes without any additives. The results show that the activation of NbCl5 plays an important role in improving the electrochemical properties of NbNOCSs electrodes. Compared with NbNOCS without NbCl5 activation treatment, NbNOCS-1/3 (NbCl5/MF with a primary carbonization weight ratio of 1∶3) shows better electrochemical performance due to its unique pore structures, rich pseudocapacitive active species, and good ion transfer characteristics. Moreover, it exhibits a high specific capacitance (173.4 F·g −1 at a current density of 0.5 A·g −1 ) and high capacitance retention (59.49% at 50 A·g −1 ), as well as a good electrochemical cyclability (90.78% after 10 000 cycles at 10 A·g −1 ).