Preparation And Energy Storage Properties Of Manganese-based And Vanadium-based Inorganic Compounds

With the growing demand for energy storage,it is of great significance to explore large-scale energy storage systems with low cost and superior performance.Based on the comprehensive consideration of crustal abundance and electrochemical performance,manganese-based and vanadium-based electrode materials may be ideal for large-scale development and application.In this context,three manganese-based and vanadium-based inorganic compounds with different structural characteristics were prepared by hydrothermal method,and their electrochemical properties were studied.The manganese-based phosphate(MP)were characterized by SEM and XRD,and the lithium ion half-cell was assembled with MP as the anode material to investigate its electrochemical performance.The results show that the sample is a mixture of Mn5(PO3(OH))2(PO4)2(H2O)4,Mn3(PO2)2 and Mn(P4O11),with a sheet-like morphology and a thickness of about 50-150 nm.Sample MP-150 has the best electrochemical performance,the charge and discharge curve has a platform.The charging capacity of the first cycle is 364.5 mAh g-1,after 10th cycles,it is maintained at about 253 mAh g-1;The Li+storage process is dominated by diffusion control,showing good electrochemical reversibility and fast ion diffusion rate.Potassium ions were introduced into the manganese-based phosphate to prepare potassium manganese phosphate(KMP).The samples were characterized by SEM,XRD and EDS,and potassium ion half-cells were assembled using KMP as cathode material to investigate its electrochemical performance.The results show that the main phase of the sample KMP is KMn4(PO4)3,and contains a small amount of impurities K2Mn(P2O7).The morphology is mainly a large rectangular plate with a length and width of about 100?300 ?m.At a current density of 50 mA g-1,The first-cycle discharge specific capacity of KMP-2 electrodes was 5.78 mAh g-1.The first-cycle discharge specific capacity is increased to 44.24 mAh g-1 after the ion exchange method.Two samples of potassium vanadate(KVO-Pre and KVO)were prepared by hydrothermal method.The samples were characterized by SEM,XRD,XPS,and FT-IR,and potassium ion half-cells were assembled using KVO-Pre and KVO as cathode material to investigate their electrochemical performance.The results show that the sample KVO-Pre is a layered K0.5V2O5,which is a long strip of nanosheets with different sizes;the sample KVO is a tunnel structure K2V8O21,which is in the shape of a long rod.At a current density of 20 mA g-1,the discharge specific capacities of KVO-Pre and KVO for the first cycle were 71.4 mAh g-1 and 68.3 mAh g-1,respectively,and the capacity retention rates after 100 cycles are 55%and 59%,respectively.