Kinetics-Driven MnO2 Nanoflowers Supported by Interconnected Porous Hollow Carbon Spheres for Zinc-Ion Batteries

For rechargeable aqueous zinc-ion batteries (ZIBs), manganese dioxide is one of the most promising candidates as a cathode material because of its cost effectiveness, eco-friendliness, and high specific capacities. However, the ZIBs suffer from poor rate performance and low cycle life due to the weak intrinsic electronic conductivity of manganese dioxide, poor ion diffusion of lump manganese dioxide, and its volumetric expansion during the cycle. Herein, we prepare MnO2@carbon composites (MnO2@ IPHCSs) by in situ growing MnO2 nanoflowers on an interconnected porous hollow carbon spheres (IPHCSs) template. IPHCSs, as excellent conductors, significantly improve the conductivity of the manganese dioxide cathode. The hollow porous carbon framework of IPHCSs can offer more ion diffusion paths to internal MnO2@IPHCS carbon composites and acts as a buffer room to cope with the drastic volume contraction and expansion during charge/discharge cycling. The rate performance tests show that MnO2@IPHCSs with high conductivity have a specific capacity of 147 mA h g-1 at 3 C. MnO2@IPHCSs with hollow and nanoflower structures are shown to have excellent ion diffusion performance (ion diffusion coefficient = 10-11 to 10-10 cm2 s-1) in the electrochemical kinetics of the galvanostatic intermittent titration technique. Long cycle performance testing and in situ Raman characterization reveal that MnO2@IPHCSs have high cycling stability (85.5% capacity retention after 800 cycles) and reversibility due to the enhanced structure and increased conductivity. The excellently conductive manganese dioxide supported by IPHCSs has good rate and cycling performance, which can be used to produce superior-performance ZIBs.

Automated summary

MnO2@carbon composites (MnO2@IPHCSs) are prepared by growing MnO2 nanoflowers on an interconnected porous hollow carbon spheres (IPHCSs) template. IPHCSs significantly improve the conductivity of the MnO2 cathode and provide more ion diffusion paths. MnO2@IPHCSs show high specific capacity and excellent ion diffusion performance, as well as high cycling stability and reversibility due to their enhanced structure and increased conductivity. These properties make MnO2@IPHCSs promising candidates for high-performance ZIBs.