Synthesis And Energy Storage Properties Of Manganese Oxide Composites

Manganese oxides have low electrical conductivity and poor structural stability,so their multiplicative performance and cycling stability are not satisfactory when used as electrode materials.To address these problems,this study uses manganese oxides compounded with conductive polymers and other transition metal oxides,and also investigates the electrochemical properties of these composites.（1）Preparation and energy storage performance of hollow core-shell FeOOH@Mn O₂ compositesThe hollow core-shell FeOOH@Mn O₂ composite exhibits excellent electrochemical properties due to its unique structure and the synergistic effect between the both.The capacitance retention was 75.9%when the current density was increased from 1 A g^-1(924 F g^-1)to 10 A g^-1(702 F g^-1),exhibiting excellent rate performance and retaining 91.2%of the initial capacity after 5000 charge/discharge cycles.Notably,the assembled FeOOH@Mn O₂//AC asymmetric supercapacitor facility possessed an energy density of 53.4 Wh kg^-1 and a power density of 722 W kg^-1,indicating that the hollow core-shell FeOOH@Mn O₂ nanorod composite is a good electrode material for supercapacitors.（2）Preparation and energy storage performance of hollow mesoporous PPy@Mn O₂ compositesIn this work,hollow mesoporous PPy microspheres were prepared by using mesoporous Si O₂ as the hard template,and hollow mesoporous PPy@Mn O₂ composites were successfully synthesized by a low-temperature redox reaction.The unique heterogeneous structure can realize the complementary advantages of the two materials.PPy can be used as the skeleton to support the whole structure,and the design of the hollow structure will further buffer the volume change during cycling.Thus,the synthesized hollow mesoporous PPy@Mn O₂ electrode has outstanding electrochemical properties with a specific capacitance of 713 F g^-1 at 1 A g^-1 and a 92%retention rate after 5000 cycles at 4 A g^-1.The assembled PPy@Mn O₂//AC device achieves a high energy density of 40.8 Wh kg^-1 at a power density of 720 W kg^-1.（3）Preparation and energy storage performance of Fe₃O₄@PPy@Mn O₂ ternary compositesIn this study,Fe₃O₄@PPy@Mn O₂ nanocomposites with porous cores and bilayer shells were successfully prepared using three chemical synthesis methods.The porous core-shell structure of the composite electrode material resulted in shorter diffusion distance of electrolyte ions,accelerated electron transfer,and good synergy between the porous Fe₃O₄ core,the conductive PPy coating and the Mn O₂ nanosheets.Thus,the Fe₃O₄@PPy@Mn O₂ electrode not only exhibits high specific capacitance,but also exhibits excellent cycling stability.Furthermore,the asymmetric supercapacitor devices assembled with Fe₃O₄@PPy@Mn O₂ nanocomosite possess remarkable cycling stability(95.2%after 5000 cycles at 5 A g^-1)and high energy density(71.3 Wh kg^-1).