Design And Synthesis Of Micro-nano Heterogeneous Phase Co-Mn-Sn Oxide/Alloy Hybrid And Lithium Storage Properties

Rechargeable lithium-ion batteries?LIBs?have received general scientific research worker attention due to their high energy density,long cycle life,and good power performance.The transition metal oxides and their alloy composites have become a new generation of LIBs anode materials with great development potential for the advantages of high theoretical capacity,low cost,environmental friendliness and structural diversity.However,its industrialization is limited by the problems of volume expansion and poor conductivity during charging and discharging.In order to solve the above problems,this paper mainly regulates the design and synthesis of micro-nano heterogeneous phases Co-Mn-Sn oxide or alloy materials.On this basis,the electrochemical properties of these materials were studied.The specific research content is as follows:?1?Synthetic Sn-Mn heterogeneous phase composites were controlled by sacrificial template method.On this basis,uniform Sn-Mn/GO composites were synthesized by adding graphene oxide aqueous solution as the carrier.After calcination in nitrogen,four kinds of composite materials were obtained:SnO2/Mn3O4-B,SnO2/Mn3O4-E,Mn3O4/SnO2-700,and Mn2SnO4/RGO.The materials prepared above were used as the anode of LIBs,showing excellent electrochemical properties.Among them,at the current density of 0.2 A g^-1,SnO2/Mn3O4-B deliver a capacity of 835 mA h g^-1 after350 cycles,SnO2/Mn3O4-E exhibit the specific capacities of 980 mA h g^-1 after 450cycles,and Mn3O4/SnO2-700 maintained a specific capacity of 1045 mA h g^-1 after400 cycles.In addition,as an anode for lithium ion batteries,Mn2SnO4/RGO exhibits a specific capacity of 845 mA h g^-1 after 350 cycles at 0.2 A g^-1.The excellent electrochemical properties are mainly attributed to the synergistic effect of composite materials in the charging and discharging process.?2?Porous?Co,Mn??Co,Mn?2O4-based microspheres?CM-11-Ms?and core-shell microspheres?CM-11-CSMs?were firstly synthesized via controlling pyrolysis of CoMn-precursor microspheres at different temperatures in nitrogen.Among them,the specific capacities of CM-11-Ms and CM-11-CSMs maintained at 745 mA h g^-1 and2173.8 mA h g^-1 respectively after 1000 cycles with a current density of 1A g^-1.The results show that CM-11-CSMs has much better lithium storage performance than CM-11-Ms,which can be attributed to the unique core-shell structure that can adapt to volume change and reactivate electrode materials,and has the synergistic effect between?Co,Mn??Co,Mn?2O4,Co3O4 and MnO.?3?Porous mutli-component heterogeneous MnSnO3-MC400 and MnSnO3-MC500microspheres have been fabricated using CoSn?OH?6 nanocubes as template via controlling pyrolysis of CoSn?OH?6/Mn0.5Co0.5CO3 precursors at different temperature in nitrogen.Among them,the MnSnO3-CM500 exhibit the specific capacities of 750mA h g^-1 after 750 cycles at a current density of 1A g^-1 without an obvious capacity decay until 1000 cycles.And MnSnO3-CM400 can provide a specific capacity of1030 mA h g^-1 after 560 cycles at a current density of 1A g^-1 with no significant capacity attenuation until 1000 cycles.The results show that the appropriate pore size and content ratio of MnCo2O4/?Co,Mn??Co,Mn?2O4 in MnSnO3-CM400 material are conducive to the improvement of lithium storage performance.?4?According to the synthesis method of the above?3?,MnSnO3/Co3Sn2-CM500 was prepared by adding appropriate carbon sources.Among them,the MnSnO3/Co3Sn2-MC500 microspheres deliver a reversible capacity of 1070.3 mAh g^-1 up to 1500^th cycle at high rate of 1 A g^-1,exhibiting an outstanding long cycling stability at high rate,owing to the conversion of some Co-Sn oxides into Co3Sn2 alloy which is beneficial to the improvement of the lithium capacity of heterogeneous structural materials.