Construction of MnO 2 - Mn 3 O 4 heterostructures to facilitate high-performance aqueous magnesium ion energy storage.

MnO 2 -Mn 3 O 4 heterostructure materials are applied in aqueous magnesium ion energy storage for the first time. The heterostructure yields an exceptionally high pseudocapacitance contribution, resulting in a specific capacitance of 313.5 F g -1 at 1 A g -1 , which contrasts with that of MnO 2 (108.8 F g -1 ) and Mn 3 O 4 (123.5 F g -1 ). Additionally, it shows potential for practical applications as a cathode for magnesium ion hybrid supercapacitors (MHS).