A Research On The Modification Of Anode And Diaphragm Of High Performance Lithium Sulfur Battery

As the best candidate to replace the traditional lithium-ion battery and meet the development of new energy vehicle industry,lithium-sulfur battery has a theoretical specific energy of 2600 Wh kg^-1 and a theoretical specific capacity of 1675 mAh g^-1.However,due to the volume expansion of the positive electrode,the insulation of sulfur and its discharge product lithium polysulfide,and the"shuttle effect",the capacity of the battery system is decreased,and the ratio and cycle performance of the range are poor.In order to promote the commercial and industrial application of lithium-sulfur battery,the following research work has been carried out in this paper from the two aspects of anode and diaphragm modification:1.NiO/CC,a kind of 3D anode with high conductivity for in-situ growth of transition metal oxides,is designed and prepared as a sulfur carrier to solve the problem of volume expansion of sulfur anode and improve the conductivity of anode,and NiO nanosheets provide more adsorption sites to alleviate the capacity decay caused by shuttle effect.the cells prepared by NiO/CC/S composite positive electrode can provide a high initial capacity of 1154.8 mAh g^-1 at 0.1 and the attenuation rate of 300 cycles is only 0.07%at 1 C.2.Preparation of typical transition metal oxide NiCo₂O₄ as a positive additive,its porous structure provides a large number of active sites for the adsorption of polysulfide,alleviating the shuttle effect.The kinetic diffusion path of NiCo₂O₄{100}surface is determined by DFT calculation,and the calculated energy barrier is 0.15 eV,which increases the rate of rapid Li⁺transport and sulfur utilization,thus improving the rate performance of NiCo₂O₄/S modified cathode,which show the specific capacity of1233.5,1098.4,958.6,859.2,723.9 and 629.2 mAh g^-1 can be achieved at current densities of 0.5,1,2,3,4 and 5 mA cm^-2,respectively,and the initial discharge capacity of 0.2 C is 1207.7 mAh g^-1.3.The transition metal oxide binary composites NiCo₂O₄@rGO were prepared by simple chemical synthesis in this paper,used for membrane modification,plays a synergistic effect.It can accelerate Li⁺migration during chemical reaction,meanwhile,meanwhile,Ni-O and Co-O bonds play a"catalytic"role,to accelerate a series of PS redox reactions.At the same time,rGO has a two-dimensional layered structure,which can provide more electrolyte storage space and ensure the high electrochemical performance of the membrane cell with NiCo₂O₄@rGO/PP under high load and low E/S,exhibiting a high capacity of 7.1 mAh cm^-1 at a high sulfur load of 6 mg_S cm^-22 and a current of 0.4 mA cm^-2?Pure C/S poles only?,which meets the standard of commercial battery and is expected to promote the commercialization of lithium sulfur battery.