Rational design of ZnMn2O4 nanoparticles on carbon nanotubes for high-rate and durable aqueous zinc-ion batteries

ZnMn2O4 (ZMO) is a promising cathode material for aqueous zinc-ion batteries (ZIBs) due to its high capacity, high output voltage and rich abundance. However, the commercial application of ZMO is severely restricted by the rapid capacity decay at high rate resulting from low electrical conductivity and structural degradation. Herein, a commonplace one-step hydrothermal method is applied to rationally synthesize ZMO nanoparticles (similar to 20 nm) on carbon nanotubes (ZMO/CNTs) heterostructure for stable high-rate Zn2+ storage. The high electrical conductive CNTs and such small ZMO benefit from electrons' fast transport, endowing ZMO/CNTs composite with high electrical conductivity. Furthermore, the flexible CNTs network and the strong interface interaction (Mn-O-C bond) between ZMO and CNTs can effectively suppress irreversible structural degradation. As a result, the ZMO/CNTs composite delivers a promising initial capacity of 220.3 mAh g(-1) at 100 mA g(-1) and a high capacity retention of 97.01% after 2000 cycles at 3000 mA g(-1), indicating excellent high-rate long-term cycling stability. Furthermore, the flexible ZIBs are assembled and show stable electrochemical properties at different bending states, demonstrating their potential practical applications.