Optimizing the Microenvironment in Solid Polymer Electrolytes by Anion Vacancy Coupled with Carbon Dots.

The practical application of solid polymer electrolyte is hindered by the small transference number of Li⁺, low ionic conductivity and poor interfacial stability, which are seriously determined by the microenvironment in polymer electrolyte. The introduction of functional fillers is an effective solution to these problems. In this work, based on density functional theory (DFT) calculations, it is demonstrated that the anion vacancy of filler can anchor anions of lithium salt, thereby significantly increasing the transference number of Li⁺ in the electrolyte. Therefore, flower-like SnS₂-based filler with abundant sulfur vacancies is prepared under the regulation of functionalized carbon dots (CDs). It is worth mentioning that the CDs dotted on the surface of SnS₂ have rich organic functional groups, which can serve as the bridging agent to enhance the compatibility of filler and polymer, leading to superior mechanical performance and fast ion transport pathway. Additionally, the in situ formed Li₂S/Li₃N at the interface of Li metal and electrolyte facilitate the fast Li⁺ diffusion and uniform Li deposition, effectively mitigating the growth of lithium dendrites. As a result, the assembled lithium metal batteries exhibit excellent cycling stability, reflecting the superiority of the carbon dots derived vacancy-rich inorganic filler modification strategy.