Research On Synthesis And Li~+/Na~+ Storage Performance Of Nickel-Cobalt-Manganese-based Anode Materials

Nowadays,Graphite-based materials are the main anode material for current commercial lithium-ion battery(LIB).However,the low theoretical specific capacity of 372 mAh·g-1 and poor rate capability limit its application in next generation high energy density LIB.In this regard,nickel-cobalt-manganese-based anode materials(carbonates and oxides)with high energy density and low cost,have drawn much attention as the desired candidates for anode materials to satisfy the high energy storage requirements.However,similar to most conversion anodes,the poor electrical conductivity and serious volume variation which often lead to the rapid capacity fading and disintegration of architecture during cycling process are still great challenges.To solve the problems and enhance the electrochemical performance of NixCoyMn2CO3(x+y+z=1),in this work,we report a solvothermal method for the successful preparation of well-distributed granular Ni0.8Co0.1Mn0.1CO3 anode materials.The optimized PVP-Ni0.8Co0.1Mn0.1CO3 composite materials,which is carbon-coated anode materials,exhibits excellent rate ability and enhanced cycling performance,which still deliver a stable capacity of about 615.8 mAh·g-1 after 600 cycles,at a current density of 1 A·g-1 with the voltage of 0.01-3.00 V versus Li/Li+ at room temperature,and maintains a stable capacity of about 272.3 mAh·g-1 after 50 cycles at a current density of 0.2 A·g-1 with the voltage of 0.01-3.00 V versus Na/Na+ at room temperature.The excellent electrochemical performance can be attributed to the effect of the carbon coating,which can enhance the electrical conductivity and the Li ion diffusion coefficient to enhance the charge transport kinetics,and alleviate the architectural change originating from the volume expansion during cycling to offer a short stable path for the lithium ions diffusion and electron-transportation.The poor intrinsic electronic conductivity of nickel-cobalt-manganese-based oxides still limits the electron transport kinetics during the process of the redox reaction,and oxides of nickel,cobalt and manganese show rapid capacity fading because of the slow ion-diffusion rates and large volume changes during the cycling process.Herein,in this work,we report a solvothermal method for the successful preparation of well-distributed granular multi-porous materials by using the carbonate precursors,and the primary particle is the tiny nanoparticles.The optimized nickel-cobalt-manganese-based oxides which is synthesised by adding PVP,exhibits excellent rate ability and enhanced cycling performance,which still deliver a stable capacity of about 658.9 mAh·g-1 after 50 cycles,at a current density of 1 A·g-1 with the voltage of 0.01-3.00 V versus Li/Li+ at room temperature.Because the complex oxides have shown better electronic conductivity and higher reversible capacity than those of single-component metal oxides,which could be ascribed to the multiple aliovalent cations and corresponding more versatile redox reactions.Herein,we change process conditions and first report a solvothermal method for the successful preparation of well-distributed hollow multi-porous composite NiMn2O4/NiCo2O4 mesocrystals.The optimal sample with well-distributed hollow multi-porous composite NiMn2O4/NiCo2O4 mesocrystals exhibits excellent rate ability and enhanced cycling performance,which maintains 532.2 mAh·g-1 with 90.4%capacity retention after 100 cycles,and can still deliver a stable capacity of about 360.8 mAh·g-1 after 500 cycles,at a current density of 1 A-g"1.The excellent electrochemical performance can be attributed to the synergistic effect of the composite NiMn2O4/NiCo2O4 structure and the uniform hollow multi-porous architecture.The composite structure can enhance the Li ion diffusion coefficient to enhance the charge transport kinetics.While,the uniform hollow multi-porous architecture can alleviate the architectural change originating from the volume expansion during cycling and facilitate electrolyte penetration.These combined effects make the NiCo1.5Mn0.5O4 a promising anode material for the practical application in EV/HEV and energy storage systems.