Synthesis And Modification Of Mn₂O₃ Cathode Material For Aqueous Rechargeable Zinc Ion Batteries

Metal-organic-frameworks?MOFs?are increasingly widely used in the field of energy storage.For the first time,we successfully prepared Mn₂O₃ using MnBTC metal-organic framework as precursor,and synthesized three kind of composite materials Mn₂O₃/Al₂O₃,Mn₂O₃/In₂O₃,Mn₂O₃@In₂O₃,respectively according two different kind of compositing methods,in which Mn₂O₃/Al₂O₃ and Mn₂O₃/In₂O₃ were synthesized by calcination of Al³⁺,In³⁺doped MnBTC,respectively,while Mn₂O₃@In₂O₃ was obtained by the coating of In³⁺precursor on the MnBTC followed by a calcination process.X-ray diffraction?XRD?and scanning electron microscopy?SEM?were used to characterize the structures and morphologies of these materials.The electrochemical properties of the materials were studied by charge-discharge test.The following conclusions are drawn:1.MnBTC was prepared by a solvothermal method,and Mn₂O₃ was synthesized by a one step calcination of MnBTC in air.The crystal growth,morphology and electrochemical properties of Mn₂O₃ samples at different calcination temperatures were investigated.The results showed that the products calcined at the temperature range from 400 to 700?for 3hours are all Mn₂O₃,but with different electrochemical performances.Mn₂O₃ obtained at the calcination temperature 400?has the best electrochemical performance.When the current density is 300 mA/g,the discharge specific capacity in the first cycle is 59.2 mAh/g,the discharge specific capacity in the second cycle is 92.9 mAh/g,and the maximum discharge specific capacity can reach 155.7 mAh/g after several cycles.The discharge specific capacity can remain at above 95 mAh/g even after 500 cycles.When the current density rise to 1500mA/g,the specific discharge capacity can still mantain at 90.2 mAh/g after 1000 cycles.2.Al³⁺,In³⁺doped MnBTC were synthesized by a solvothermal method.Mn₂O₃/Al₂O₃and Mn₂O₃/In₂O₃ composites were synthesized by the calcination of metal-doped MnBTC precusors.The composites showed enhanced electrochemical properties.The experimental results showed that the specific discharge capacity of Mn_0.7Al_0.3BTC-400?-3h sample is about 100 mAh/g after 1000 cycles at the current density of 300 mA/g,which is 80 mAh/g higher than that of MnBTC-400?-3h sample.The discharge capacity of sample Mn_0.95In_0.05BTC-400?-3h can maintain a stable value of 205.2 mAh/g at a current density of300 mA/g,after 600 cycles,the cycle stability is better than that of Mn_0.95In_0.05BTC-400?-3h sample.Under the current density of 1500 mA/g,the discharge capacity of Mn_0.95In_0.05BTC-400?-3h can reach about 180 mAh/g after 1000 cycles.Compared with the samples synthesized from Al³⁺,In³⁺doped MnBTC with the same metal doping mole ratio,it was found that both the composites show improved electrochemical properties,which indicated that the existance of Al₂O₃ or In₂O₃ did not change the position of charging and discharging platforms,and effectively prolonged the charging and discharging platforms of the materials.3.Mn₂O₃@In₂O₃ materials was synthesized by a coating method of MnBTC.The effect of different amount of indium chloride coating precursor on the properties of the material was explored.The results showed that the cycly property of the material were obviously improved after coating.When 0.02 g indium chloride was used as the coating precursor,the modified Mn₂O₃ material exhibited good electrochemical performance.The discharge specific capacity can reach 188.7 mAh/g after 600 cycles at a current density of 300 mA/g,and which is 100.2mAh/g higher than that of the pure sample without coating.Compared with Mn₂O₃/In₂O₃reported in last chapter,it was found that two ways of introducing Al₂O₃ can improve the electrochemical property of Mn₂O₃,and material obtained by doping methods shows better performance than that obtained by coating method.