Controllable Synthesis And Electrochemical Lithium Storage Performance Study Of CoFe₂O₄ Solid,Hollow And Multi-Shell Hollow Nanospheres

Ternary transition metal oxides(TTMOs)due to their complex chemical composition,flexible structure and synergic effects of multiple metal species have been extensively used as electrode materials of lithium-ion batteries(LIBs).However,the problems induced by their inherent poor conductivities and structural collapse arising from drastic volume variation during the Li+ repeated charge/discharge process that restricts their practical applications as the anode materials.One efficient strategy to avert the above issue is to design various desirable micro-/nanostructured TTMOs,such as hollow architectures,which have been widely proven.In particular,multi-shell TTMOs hollow architectures are recently attractive,since they can not only inherit all merits of simple hollow structures,but also provide better structural support and possess higher energy density.As a result,many types of multi-shell TTMOs hollow architectures have been successfully synthesized.However,the existing synthetic techniques for multi-shell TTMOs hollow architectures are either in multistep procedures which are time-consuming,unsuitable for large-scale production,or difficultly regulated the morphology and aggregation,especially hard achieved nanosized control.Therefore,it is highly expected to construct nanoscale multi-shell TTMOs hollow structures through a facile one-step method for large-scale production.CoFe2O4(CFO)stands out from the TTMOs due to its natural abundance,eco-friendliness,low cost and ultrahigh theoretical capacity(916 mA h g-1).However,to the best of our knowledge,the literatures concerning the fabrication of nanosized multi-shell CFO hollow structures and its application in LIBs are scarce.In this work,we design for the first time a simple and effective method on a large scale to controllably fabricate CoFe2O4 solid nanospheres(CFO-SNSs),CoFe2O4 hollow nanospheres(CFO-HNSs)and multi-shell CoFe2O4 hollow nanospheres(MS-CFO-HNSs)by just varying the calcination conditions.Compared with CFO-HNSs and CFO-SNSs,as anode materials for LIBs,MS-CFO-HNSs deliver a superior lithium storage capacity,which stabilize at a reversible capacity as high as 1354 mA h g-1 after 500 cycles at a current density of 500 mA g-1.Even under the high current densities of 1000 and 5000 mA g-1,the specific capacity of MS-CFO-HNSs are still up to 1041 and 570 mA h g-1 after 500 cycles,which are superior to all as-reported materials with same structures or components.In short,the simple preparation process toward large-scale production,unique multi-shell structures with nanosized size and superior electrochemical performances render MS-CFO-HNSs to be potentially attractive anode materials for LIBs.