Preparation And Lithium Storage Performance Studies Of Carbon-coated Transition Metal Oxides/phosphatides

Lithium-ion batteries?LIBs?have been generally used in portable electronic devices and electric vehicles because of high energy density,no memory effect and long cycling life.At present,graphite carbon-based materials as anodes have become increasingly difficult to meet demand for large capacity of batteries due to their low theoretical capacity.Developing high-efficiency anode materials has become the key to promote the rapid development of LIBs technology.It is shown that the theoretical specific capacity of transition metal oxide/phosphide is more higher than that of graphite anodes.Among them,manganese oxide/ferric phosphide attracts extensive attention of researchers as anode materials for LIBs due to its high theoretical capacity,environmental friendliness and natural abundance.However,the poor electrical conductivity of these two electrode materials will cause drastic volume changes during repeated lithium insertion/extraction processes,which will seriously affect their electrochemical properties.In this paper,we focus on the shortcomings of manganese oxide and iron phosphide,which have poor conductivity and large volume change rate during charging and discharging.The lithium storage performance was improved by coating high conductivity carbon material and changing its micro-morphology.The main results are as follows:?1?The smooth surface and uniform particle size of MnCO₃ microspheres were synthesized by simple coprecipitation method.After hydrothermal and carbonization treatment,we design and prepare pomegranate-like microspheres of nano-sized MnO particles with gaps among them as core and porous carbon as shell.In such unique PCMS@MnO,the nano-sized MnO particles with gaps among them confined in porous carbon shell can effectively prevent the aggregation and pulverization of active materials.As an anode material for LIBs,the PCMS@MnO exhibits remarkable high reversible capability?935 mAh/g at 100 mA/g?and cycling stability?527 mAh/g of 2000 mA/g after 2000 cycles?.?2?We have successfully designed porous 3DG/metal organic framework composite by an excessive metal-ion-induced combination and spatially confined Ostwald ripening strategy.We obtain carbon-coated ferric phosphide encapsulated within 3DG composites by annealing the sodium phosphite and the 3DG wrapped Prussian blue composites.The 3DG/FeP@C aerogel integrates the hierarchical structure with highly interpenetrated omnibearing conductive network and contact between graphene and porous FeP,which improves electrical conductivity and reinforces the structural robustness of FeP during electrochemical processes.The flexible electrodes are not need to set fluid,conductive carbon black,and binder of affect the electrode material performance.The flexible 3DG/FeP@C aerogel electrode directly used as anode material for LIBs delivered ultrahigh reversible capacities of736 mAh/g at 100 mA/g after 100 cycles,excellent rate performance,and superior cycling stability of 604 mAh/g after 400 cycles at a high current density of 500 mA/g.