The Structure Design,Preparation And Its Application Of Manganese-based Compounds For Aqueous Zinc Ion Batteries

Compared with organic lithium-ion batteries,aqueous zinc ion batteries(AZIBs)with the aqueous solution as electrolyte have the advantages of low cost,high safety performance,simple assembly,and so on.They have wide application prospects in large mobile energy storage equipment.At present,there are few kinds of cathode materials available for AZIBs,among which manganese-based cathode materials have the advantages of high energy density,rich resources,and low price.However,during charging and discharging,there are a series of problems,such as poor cycle stability,poor electrical conductivity,and side reaction,which limit its application in AZIBs.In this paper,different synthesis methods and preparation processes such as adjusting its structure,morphology,and carbon coating were used to modify the electrochemical performance of manganese-based cathode materials.The specific research contents are as follows:(1)K_0.17MnO₂ cathode material was synthesized by hydrothermal method with KMnO₄ and Mn SO₄ as raw materials and calcined at 500?for 2h.K_0.17MnO₂ was used as AZIBs cathode material.The results show that the K_0.17MnO₂ microsphere was similar to the cauliflower structure,and the secondary particles were composed of rod-shaped particles with a length of about 200 nm and a diameter of about 25 nm.The cyclic voltammetry showed that the radius of zinc ion was smaller than that of potassium ion,and it was easier to embed into K_0.17MnO₂ cathode material.the initial charge specific capacity of the material is 189.26m Ah/g(at 100 m A/g).When 0.05mol/L Mn SO₄ was added into the electrolyte,the discharge specific capacity was 78.0m Ah/g even at a high current density of 3200m A/g.Compared with the case without Mn SO₄,it showed excellent cycle stability and rapid ion migration rate.(2)MnO@N-C cathode material was synthesized by electrospinning method with Manganese acetate,polyvinylpyrrolidone(PVP),and anhydrous ethanol as raw materials.The effects of spinning solution concentration,voltage,temperature,humidity,receiving distance,injection speed,and calcination temperature on the MnO@N-C of morphology and electrochemical properties were investigated.To investigate the effect of the composite materials on the electrochemical performance of zinc ion battery,the phase composition of the composite materials under different charging States was measured by non in situ XRD,the charge/discharge mechanism was explored,and the pseudo charge was explored by cyclic voltammetry at different scanning rates tolerance behavior.The experimental results show that the MnO@N-C nanofibers are successfully prepared by electrospinning.The electrochemical performance of the composite calcined at 500?is better than that at 700?.MnO@N-C-500-GF After50 and 200 cycles,the reversible capacity is still as high as 171.1mah/g and176.3mah/g.The analysis of pseudocapacitance behavior is mainly controlled by diffusion,and the mechanism analysis shows that it is the combined action of insertion/de-insertion mechanism and deposition/dissolution mechanism.(3)MnO/C@rGO was prepared from manganese acetate,terephthalic acid and GO(graphene oxide)by MOFs and solvothermal method.The effect of r GO coated MnO on the electrochemical properties of the composite and the inhibition effect of r GO coated MnO on the dissolution of Mn in electrolytes were investigated.XRD,Raman spectroscopy,thermogravimetric analysis,XPS,SEM,TEM and other detection methods were used to characterize the MnO/C@r GO.GITT and EIS were used to detect the ion diffusion rate,and cyclic voltammetry of different scanning rates was used to explore the pseudocapacitance behavior The content of Mn²⁺was measured after the electrode was immersed in the electrolyte for 7 days to explore the effect of r GO coated MnO on inhibiting the dissolution of Mn in the electrolyte.The experimental results show that MnO/C@r GO is successfully synthesized by MOFs and the solvothermal method.The results show that MnO composite has no other impurities,and the surface of MnO is uniformly coated with a layer of porous carbon distributed on the graphene layer,which improves the conductivity of MnO and shows excellent electrochemical performance.the discharge specific capacity is as high as 170.6 m Ah/g at 500 m A/g after 300 cycles.The pseudocapacitance analysis shows that it is mainly controlled by diffusion.The results of GITT and EIS show that MnO/C@r GO has ultrafast ion diffusion kinetics.MnO/C@r GO and MnO/C were found in the electrolyte for 7 days It can effectively inhibit the dissolution of manganese ion in electrolytes.(4)MnS/MnO@CF was prepared by electrospinning from manganese acetate,thioacetamide,polyvinylpyrrolidone(PVP)and absolute ethanol.The effects of polymer concentration,voltage,temperature,humidity,receiving distance and injection speed on the fiber morphology were investigated to explore the optimal spinning conditions.The effects of calcination temperature and time on Mn S/MnO@CF were investigated The cyclic and rate properties of the composites were studied.Non-in situ XRD was used to measure the phase composition under different charging States to explore the charge/discharge mechanism,and cyclic voltammetry at different scanning rates to explore the pseudocapacitance behavior.The ion diffusion rate was detected by GITT,and the materials were characterized by XRD,TGA,XPS,SEM,TEM.The experimental results showed that Mn S/MnO@CF was successfully synthesized by electrospinning.The results show that the best calcination temperature is 800?,the three-dimensional interlaced fiber network can be clearly found in SEM,and obvious carbon can be observed in TEM.The cyclic voltammetry curve has an irreversible oxidation peak at 1.14v,which corresponds to the low first-coulomb efficiency and high first discharge specific capacity.The reason is that S^2-in Mn S is oxidized to sulfur to form S vacancy,which is more conducive to the storage of Zn²⁺.After 300 cycles,the specific capacity can reach 203.7m Ah/g(at 500m A/g),and the reversible incapacity can reach 115.5m Ah/g(at 2A/g),showing excellent rate performance and ion diffusion rate.Pseudo capacitance analysis shows that the whole electrode reaction is mainly controlled by diffusion.