Hydrothermal Synthesis And Electrochemical Properties Of Mn-spinel Metal Oxide

Lithium-ion battery as a green secondary battery has been widely applied in people’s daily lives.Currently the commercial production of graphite anode can not meet its application in the field of energy storage because of its low theoretical capacity.The transition metal oxides especially manganese spinel metal oxides with high theoretical specific capacity(600-1000 mAh/g)are the hotspots of lithium ion battery anode materials because of their stable structure,low cost of raw materials and environmental friendliness.However,the volumechange during charge and discharge process can easily lead to the collapse of the electrode material structure and the poor conductivity limits its application.Manganese spinel transition metal oxide can be supported on the graphene layer to alleviate the volume change while improving its conductivity.The main contents of this paper are as follows:(Co,Mn)(Co,Mn)2O4/RGO nanocomposites was synthesized first.Graphene oxide was prepared by the improved Hummers method,then the(Co,Mn)(Co,Mn)2O4/RGO was obtained by a simple and mild one-step hydrothermal process without any annealing.For comparsion,pure metal oxide without RGO was prepared as well.The spinel(Co,Mn)(Co,Mn)2O4/RGO nanocomposite has a more uniform particle morphology and better electrochemical performance than the pure metal oxide.The effects of hydrothermal time on the morphology and electrochemical properties of nanocomposites were investigated.The spinel(Co,Mn)(Co,Mn)2O4/RGO nanocomposite with the hydrothermal reaction time of 8 h has the most suitable particle size and the excellent electrochemical performance.The initial discharge capacity was 1486.9 mAh/g,the first coulombic efficiency was 73.7 %,and the capacity after 50 cycles was 743 mAh/g.Then ZnMn2O4/RGO nanocomposites were synthesized by a simple one-step hydrothermal process as well.Compared with pure ZnMn2O4 nanoparticles,ZnMn2O4/RGO nanocomposites have a more uniform morphology and improved electrochemical properties.The effects of hydrothermal time on the morphology and electrochemical properties of nanocomposites were investigated.The ZnMn2O4/RGO nanocomposites with the hydrothermal reaction time of 10 h exhibit the best performances.The average particle size was about 30 nm.The initial discharge capacity was 1279.7 mAh/g under the current density of 100 mA/g,and the specific capacity remained at 796.9 mAh/g after 50 charge and discharge cycles.Compared with the second discharge capacity,the capacity retention rate was 96.07 %.In general,a simple one-step hydrothermal method was successfully used to achieve the crystalline spinel metal oxide attached to the reduced graphene oxide layer without high-temperature annealing.The introduction of reduced graphene oxide can improve the cycle performance and rate capabilities.The method provides a new way to obtain high performance lithium ion battery anode materials.