Design And Application Of Mesoporous Silica Functional Interlayer Materials For Lithium-Sulfur Batteries

With the continuous development of the economy,people's demand for energy is increasing,and traditional non-renewable energy sources are in short supply and environmental pollution.Therefore,it is urgent to develop advanced energy storage technologies to solve the current energy storage problems.Lithium-sulfur batteries with a theoretical specific capacitance of 1675 m Ah g^-1and an energy density of 2600 Wh kg^-1have the advantages of being environment-friendly,cheap,and are expected to replace lithium-ion batteries as the next generation energy storage system.However,its commercialization has been hindered by many problems.Among them,the shuttle effect caused by polysulfides generated during the charge and discharge process and the formation of lithium dendrites has led to the most severe safety impact.This dissertation employed functionalized mesoporous silica nanospheres to prepare high-performance nano-functional interlayer materials.The effects of functional interlayers on the inhibition of polysulfide shuttle effect,lithium dendrite growth and electrochemical performance were investigated.The research results obtained are as follows:(1)A spin coating approach was employed to alternately coat positively and negatively modified mesoporous silica to prepare LBL functional interlayers.Among them,the ordered mesoporous silica porous structure can promote electrolyte absorption and lithium-ion diffusion,thereby reducing the interface impedance,and its positive and negative interactions on the surface can effectively block the shuttle of polysulfides.The battery with this functional interlayer has a capacity retention rate of 74%of the initial capacity at 0.5 C,and can stably cycle 200 times at 1 C,and the capacity decay rate is as low as 0.076%per turn.(2)Mesoporous silica with opposite charges was applied to both sides of a commercial polypropylene separator by a simple and mass-produced doctor blade coating method.Among them,the synergy of different charges on both sides of the separator can effectively inhibit the shuttle of polysulfides,and its porous structure promotes rapid diffusion of lithium ions between interlayers,reduces the consumption of lithium ions,and makes it uniformly deposited on the surface of lithium metal and the rigid skeleton is beneficial to inhibit the growth of lithium dendrites.The functional interlayer coating on the separator achieves the synergistic protection of the sulfur positive electrode and the lithium negative electrode.The battery using the functional interlayer coating separator exhibits excellent cycle stability,can stably cycle 2000 cycles at 1 C,and the capacity decay rate is as low as0.024%circle and has good rate performance,high sulfur-loaded cycle stability,and excellent self-discharge resistance.The overall preparation process has low energy consumption,easy operation,and environmental friendliness,and is easy to be prepared and applied on a large scale by engineering.