Carbon Dots Induced Supramolecular Gel Polymer Electrolyte for High‐Performance Lithium Metal Batteries

This study addresses the low ionic conductivity and lithium dendrite issues in polymer electrolytes by introducing a supramolecular strategy using carbon dots. A carbon dot-assembled physical cross-linked gel polymer electrolyte (CDPE) is synthesized, achieving 3.20 mS cm⁻¹ ionic conductivity at 30 °C and enhancing lithium dendrite suppression. The Li||LiFePO₄ battery with CDPE retained 92% capacity after 2000 cycles, demonstrating excellent stability and safety, paving the way for advanced polymer electrolytes.

Abstract

The low ionic conductivity of polymer electrolytes at room temperature, coupled with challenges associated with lithium dendrite formation, has impeded their practical applications. To mitigate these issues, this study employs a supramolecular strategy that utilizes the quantum size effect of carbon dots and the physical cross-linking of their abundant surface functional groups to enhance the electrochemical properties of polymer electrolytes. The carbon dot-assembled physical cross-linked gel polymer electrolytes (CDPE) establish a hydrogen-bonding physical cross-linking network between the carbon dots and the polymer molecular chains, the crystalline phase is suppressed, a diverse and efficient ionic transport pathway is created within the electrolyte. This significantly improves its ionic conductivity up to 3.20 mS cm⁻¹ at 30 °C. Additionally, the interaction between carbon dots and fluoroethylene carbonate facilitates the formation of a multiphase solid-electrolyte interphase, effectively suppressing the growth of lithium dendrites and markedly improving the long-term stability of lithium metal batteries. The Li||LiFePO₄ battery with CDPE demonstrates 92% capacity retention after 2000 cycles at a rate of 2.0 C, revealing superior overall cycling performance compared to covalent cross-linked systems. The carbon-dot-based physical cross-linking strategy proposed in this study paves the way for innovative design and industrial applications of high-performance composite polymer electrolytes.