| With the increasing emphasis on energy problems and the advancement of modem technology,the requirements for lithium-ion batteries as energy storage devices are also increasing.However,due to the low capacity and poor rate performance of traditional commercial graphite anode,it is difficult to meet the requirements for rapidly developing energy vehicles and portable electronic devices.Tin oxides and manganese oxides have high theoretical specific capacity,abundant resources and they are environmentally friendly.Therefore,they have been extensively studied and are considered to be the best alternative to graphite as the next generation of lithium ion battery anode materials.However,both oxides have serious volume effect.During the charge and discharge process,the material will be significantly agglomerated and pulverized,and even separated from the current collector,resulting in rapid decline of the battery capacity.In addition,while the development of lithium ions,its short-sightedness is also revealed,inclouding the uneven distribution of lithium resources and the high cost of battery.The sodium resources are abundant,wide distribution across the globe,and the sodium-ion battery has a similar charge and discharge mechanism with lithium-ion battery.But in term of capacity,it is significantly worse than lithium-ion batteries.For sodium-ion battery,a suitable negative electrode material is also one of the key factors in its electrochemistry performance.In this paper,Sn and Mn salts are selected as raw materials,graphene and carbon nanotubes are used as carbon sources,and different complexes are synthesized with the help of freeze-drying technology,which can suppress the volume effect of materials well and obtain good electrochemical performance.The performance difference of the anode material between the lithium/sodium ion batteries was tested.(1)MnOx/graphene composite with a large size of MnOx was synthetized by hydrothermal method.With the help of freeze-drying method,the composite maintains the consistent structure.When the composite work as anode material in lithium-ion battery,the discharge specific capacity of material maintains at 729.1 mAh g-1,and the corresponding coulombic efficiency is as high as 99.3%after cycled for 300 times at current density of 1A g-1.As for sodium-ion battery,after cycle 500 times at current density of 1A g-1,the discharge specific capacity of composite remains at 70 mAh g-1.The performances of composite in lithium/sodium-ion batteries are significantly higher than that of the conventional dried Mnox oxide/graphene material.(2)The MnO/graphene material was synthesized by simple heating and stirring method.MnO dispersed on the graphene in nanometer size.The material exhibits excellent lithium storage performance and rate performance.After cycle 120 times at current density of 5 A g-1,it remains 504.3 mAh g-1 discharge specific capacity.At current density of 15 A g-1,the battery keeps the discharge specific capacity of 191.9 mAh g-1 after 99 cycles.(3)The SnO2/rGO aerogel with three-dimensional porous crosslinked structure obtained in the second experiment,which has better cycle stability and rate performance.After 124 cycles at current density of 1A g-1,the discharge specific capacity of material remains stable and up to at 800 mAh g-1,the coulomb efficiency is close to 100%(LIBs).The discharge specific capacity maintaine at 189.9 mAh g-1 after 260 cycles at current density of 0.5 A g-1,the coulomb efficiency is close to 100%(SIBs).And pouch cell still maintains a discharge specific capacity of 531 mAh g-1 after cycling for 330 cycles at current density of 0.1 A g-1,and the coulomb efficiency is 98.2%.(4)The SnO2/graphene/CNTs material was synthesized by simple heating and stirring method.The CNTs were used to improve the integrity of the material.Finally,the material exhibits good electrochenical performances on both lithium/sodium-ions batteries and pouch cells. |
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