Lithium Storage Behaviors Of Rod-like Porous MnO@C Prepared By T-shaped Microchannel Reactor

Recently,MnO has been intensively investigated because of its high capacity,low electric potential,abundant resources and low cost.However,its practical application is limited by the poor rate performance and cycle-stability due to the low conductivity and the structural collapse caused by the volume expansion during the charging and discharging process.To overcome the shortcomings of MnO,a T-shaped microchannel reactor was used to prepared manganese oxalate precursor using MnSO4·H₂O and?NH4?2C2O4·H₂O as raw materials,and then MnO@C can be obtained by sintering the mixture of manganese oxalate precursor and glucose.The effects of the processes parameters on the structure,morphology,electrochemical performance and Li+ intercalation/deintercalation of the prepared samples were investigated by X-ray diffraction?XRD?,field emission scanning electron microscope?SEM?,cyclic voltammetry?CV?,electrochemical impedance spectroscopy?EIS?and galvanostatic charge-discharge test.When the feed flow rate and the concentration of the raw materials increase,the size of the precursor and MnO@C first decreases and the increases,while the capacity and the cycle-stability of MnO@C first increase and then decrease.The cycle-stability of MnO@C increases with the increase of the amount of glucose,but its capacity decreases.As the aging time prolongs,the precursor and the prepared MnO@C evolve from rod-like structure to the agglomerated bulk particles,leading to poor electrochemical properties.As the feed flow rate,the concentration of the raw materials and the amount of glucose increase,the activation energy values of the interfacial electrochemical reaction and the Li+ diffusion in the bulk material first decrease and then increase.However,the activation energy of the diffusion in the SEI membrane decreases with the increase of the amount of glucose,and the feed flow rate and the concentration of the raw materials have little influences on the activation energy of the diffusion in the SEI membrane.On the basis of the above results,we can get the preparation conditions of MnO@C:The rod-like MnC2O4·2H₂O can be prepared mixing MnSO4 solution?0.2 mol·L-1?and?NH4?2C2O4 solution?0.2 mol·L-1?at 70 ml·min-1 in T-shaped microchannel reactor.The MnC2O4·2H₂O precursor was mixed with glucose at the mass ratio for 10:4.After sintered at 450 ? for 6h,the mixture transforms to rod-like MnO@C with a diameter of 3 nm.The synthesized MnO@C has porous structure with an average pore size of 7.70 nm,and its specific surface area is as high as 147.48 m3·g-1.When used as an anode for lithium ion battery,the prepared porous MnO@C rod delivers a discharge capacity of 844.6 mAh g-1 after 100 cycles at 2 C.Even when charged/discharged at 5 C,this sample still gives a discharge capacity of 699 mAh g-1,showing good cycling stability and rate performance.The improved performance can be ascribed to the carbon coated 1D porous structure that alleviates the volume expansion of MnO in the Li+ intercalation/deintercalation process and improves the migration rate of electrolyte penetration,lithium ion and electron.