Preparation And Electrochemical Properties Of Manganese Oxygen-Porous Composites

Aqueous zinc ion batteries?AZIBs?have received increasing attention because of their low cost,environmental benefits and material abundance.However,the intercalation of zinc ions in the cathode materials is challenging and complex.To tackle the above-mentioned issue,this paper firstly introduces AZIBs,and the research progress of metal-organic coordination polymers?MOCP-H?,manganese oxides/manganese oxide?MnO_x/NCm?composites and porous carbon material/manganese dioxide?MnO₂/MCMs?composites is briefly summarized,and the research focus of this paper is put forward:the use of materials with excellent conductivity to modify some water-based zinc ion battery electrode materials To achieve the purpose of improving the electrochemical performance of the electrode material.The main contents of this paper are:?1?The flake MOCP-H material was successfully synthesized by hydrothermal method,using SEM,XRD and surface area and porosity analyzer for MOCP-H.We demonstrate AZIBs system which consists of MOCP-H nanosheets cathode,a Zn foil anode,and a ZnSO₄/MnSO₄ solution electrolyte.The zinc cell delivers a high reversible capacity of 240.3 mA h g^-1 at 150 mA g^-1 and an excellent capacity retention of approximately 100%over 1500 cycles at 600 mA g^-1.The superior electrochemical performance is ascribed to the addition of MnSO₄,which results in the formation of MnO₂,and the MnO₂ can enhance the electrochemical performance of the AZIBs.The synergy effects between MOCP-H and MnO₂ may open new opportunities for the development of low-cost,high performance rechargeable aqueous batteries.?2?Manganese hydroxide/polyaniline?MnOOH/PANI?composites were successfully prepared by one-pot hydrothermal method.?-MnO₂/N-doped carbon matrix?NCm?or Mn₅O₈/NCm composites were obtained by different calcination temperatures.The morphology and structure of MnOOH/PANI,?-MnO₂/NCm and Mn₅O₈/NCm composites were characterized by SEM and XRD.The energy dispersive X-ray spectroscopy?EDX?results of?-MnO₂/NCm and Mn₅O₈/NCm show that the nitrogen-doped carbon matrix is uniformly distributed throughout the structure,and NCm provides higher conductivity and reduces battery capacity attenuation.At current densities of 200 mA g^-1,the?-MnO₂/NCm electrode delivered a higher discharge capacity of 331 mAh g^-1 comparing with 185 mAh g^-1 for the pure?-MnO₂ electrode.Besides,the Mn₅O₈/NCm electrode could provide a discharge capacity of 266 mAh g^-1.Therefore,the approach in this study may pave the way on preparing manganese oxides/NCm materials for AZIBs.?3?MnO₂/MCMs were prepared by using litchi shell as carbon source and template.The optimal activation ratio of MCMs by SEM was 1:4?MCM4?in litchi shell and potassium hydroxide?KOH?.The specific surface area and porosity analyzer showed that the specific surface area was 735.785 m²/g.At current densities of 60 mA g^-1,the reversible specific capacity after cycling for 50 weeks is still maintained at160.191 mAh g^-1,and the capacity decays faster.The energy dispersive X-ray spectroscopy?EDX?results of MnO₂/MCM4 demonstrate that carbon and manganese elements are uniformly distributed throughout the structure,and MCMs provide higher conductivity.The reversible specific capacity after 150 cycles at a current density of 200 mA g^-1 remained at 263 mAh g^-1 with almost no attenuation.