Application And Performance Study Of Inorganic Poiymer-Based Binder In Lithium-Suifur Battery

Lithium-sulfur(Li-S)batteries are considered to be an optimal solution for addressing the capacity limitation of commercial lithium batteries due to their higher theoretical capacity,environmental friendliness,and enhanced safety.In present-day society,there is a critical need for the rapid advancement of efficient electrode materials specifically for Li-S batteries.The binder is a key factor in improving the energy density,rate performance,and cycle life of Li-S batteries.While the traditional organic binder polyvinylidene fluoride(PVDF)has been widely used with the development of technology,the requirement for toxic solvent N-methylpyrrolidone(NMP)increases the cost and results in severe environmental pollution.Accordingly,there is a worldwide research effort to develop sustainable inorganic binder alternatives for PVDF.The inorganic polymer binder can effectively adsorb polysulfide and inhibit the volume expansion of sulfur cathodes,which provides ideas for the future application and performance research of Li-S batteries.In addition,inorganic polymer binder also has the advantages of cheap and easy to obtain,green environmental protection.Therefore,this dissertation mainly focuses on the design and properties of inorganic polymer-based binders as follows:(1)The shuttle effect of polysulfide and mechanical instability of the sulfur cathode during the cycle significantly impede the development of Li-S batteries.The construction of a robust affinity oxide host is an effective approach for anchoring polysulfide.Oxide hosts that contain sulfur-active materials require additional binders to maintain contact between the positive material and the collector fluid,and their ability to inhibit sulfur cathode volume changes is inadequate.This dissertation proposes the use of a bi-functional lithium polysilicate(Li2O·n Si O2,LSO)as an effective binder and anchor host for improving the longevity and performance of Li-S batteries.Additionally,the density functional theory(DFT)calculation results show that LSO has a significant adsorption effect on polysulfide.Moreover,LSO exhibits superior bonding functionality and adsorption effect,which makes it a favorable binder for Li-S batteries and enhances the mechanical stability of sulfur cathodes.The sulfur cathode that utilizes LSO as an efficient binder and anchor host is cycled 500 cycles at 0.5 C with each cycle exhibiting only 0.076% capacity attenuation,thus demonstrating substantial cycle stability.This work presents a new direction for improving the electrochemical performance and mechanical stability of sulfur cathodes.(2)Inorganic polymer LSO binder has the characteristics of being environmentally friendly and low-cost,and possesses abundant polar Si-O and Si=O bonds,which can effectively adsorb polysulfide.Nonetheless,due to its short chain structure,it cannot play a better role in high-loading Li-S batteries.We studies a natural plant macromolecular polysaccharide,Tamarind polysaccharide gum(TPG),which has abundant-OH bonds that can form hydrogen bonds with strong mechanical properties,thereby maintaining the integrity of sulfur cathodes in high-loading Li-S batteries.Consequently,the two are crosslinked and combined with the advantages to form a three-dimensional mesh binder c-LSO-TPG.The second part of this dissertation consists of experimental inquiries and an analysis of the performance of Li-S battery with respect to the S@c-LSO-TPG electrode.The results show that the cLSO-TPG binder can maintain the integrity of sulfur cathode and inhibit volume expansion based on stripping experiments and scanning electron microscopy(SEM)characterization.The atomic force microscopy(AFM)and contact angle tests also demonstrate that the c-LSO-TPG binder has the most suitable Young’s modulus and wettability.Particularly,under the high load of 6.1 mg cm-2,it can cycle 100 cycles steadily,and the final specific capacity is still maintained at 576.1 m Ah g-1.This provides a new avenue for the research and development of binders for high-loading and long-lifespan Li-S batteries.