Synthesis Of MnCo-based Spinel Materials And Their Electrochemical Application

Transition metal oxide is a promising material of the anode material of the lithium ion battery due to their high reversible capacity and good rate performance.However,some shortcomings still exists,such as the first irreversible capacity loss and poor cycle ability.To a certain extent,these materials with the nanostructured can improve its electrochemical performance.Form this point,three kinds of nanostructured manganese cobalt spinel materials with different morphologies and the primary structure is nanostructure were synthesized in this work by solvothermal method.The structure of the as-synthesized materials was analyzed by XRD,FTIR,SEM and TEM and their electrochemical properties were also tested.The rose-like MnCo₂O₄ materials with precursors as layerd double hydroxides was synthesized by using PVP as soft template and urea as precipitant.The growth mechanism of the rose-like MnCo₂O₄ materials was reasonably speculated in this work.The initial charge/discharge capacity of as-prepared material is 1502 mA×h×g-1 and 1130 mA×h×g-1,which is higher than its theoretical capacity of 891 mA×h×g-1.With the increasing of the current density,the discharge capacity gradually decreased,surprisingly,when the current density from 1000 mA× g-1 back to 100 mA× g-1,the discharge capacity is still maintained to 1200 mA×h×g-1.The discharge capacity was 81.3% of the first discharge capacity after 80 cycles of charge and discharge test.All the results indicates that the material has a good rate performance and cycling performance.The flower-like Fe-MnCo₂O₄ materials was successfully synthesized by FeSO4 · 7H2 O as the iron source doped rose-like MnCo₂O₄.When tested at the current density of 100 mA×g-1,the measured first charge/discharge capacity of Fe-MnCo₂O₄ materials are 902 mA×h×g-1 and 700 mA×h×g-1,respectively.With the current density increasing,the discharge capacity of the flower-like nanomaterials decreases gradually.But when the current density returns to 100 mA×g-1,the discharge capacity can maintain its initial 900 mA×h×g-1;After 80 cycles of charge and discharge,the discharge capacity of the nanomaterial is 800 mA×h×g-1.It is shown that the Fe-MnCo₂O₄ nano-materials have better rate performance,but the cycling performance and charge/discharge capacity are poor than rose-like MnCo₂O₄ nanomaterials.The cube-aggregated Co Mn₂O₄ material was synthesized by using urea as precipitant and Co0.33Mn0.67CO3 as the precursor.At the current density of 100 mA×g-1,the measured first charge/discharge capacity are 1462 mA×h×g-1 and 1184 mA×h×g-1,respectively.Both are much higher than its theoretical capacity of 691 mA×h×g-1.With the current density increased,the discharge capacity of the cube-aggregated Co Mn₂O₄ materials also decreases gradually,but when its current density returns from the large current density to the small current density,it's found that the discharge/charge capacity remains its initial value and the results shows that the cube-aggregated Co Mn₂O₄ has a better rate performance.The following cycling performance test indicates the performance has a tendency of decaying,and after 80 cycles of charge and discharge,the discharge capacity decreased 61% compared with the first discharge capacity.