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Solid‐state batteries can ensure high energy density and safety in lithium metal batteries, while polymer electrolytes are plagued by slow ion kinetics and low selective transport of Li+. Metal‐organic frameworks (MOFs) are proposed as emerging fillers for solid‐state poly(ethylene oxide)(PEO) electrolytes, however, developing functionalized MOFs and understanding their roles on ion transfer has proven challenging. Herein, combining computational and experimental results, the functional group regulation in MOFs can effectively change surficial charge distribution and limit anion movement is revealed, providing a potential solution to these issues. Specifically, functionalized 2D MOF sheets are designed through molecular engineering to construct high‐performance composite electrolytes, where the electron‐donating effect of substituents in 2D‐MOFs effectively limits the movement of ClO4− and promotes mechanical properties and ion migration numbers (0.36 up to 0.64) of PEO. As a result, Li/Li cells with composite electrolyte exhibit superior cyclability for 1000 h at a current density of 0.2 mA cm−2. Meanwhile, the solid LiFePO4/Li battery delivers highly reversible capacities of 148.8 mAh g−1 after 200 cycles. These findings highlight a new approach for anion confinement through the use of functional group electronic effects, leading to enhanced ionic conductivity, and a feasible direction for high‐performance solid‐state batteries.

Bi-doped carbon dots with rich polar groups and great compatibility was employed as co-deposition electrolyte additives to homogenize Li+ flux for dendrite-free Li deposition. High coulombic efficiency (99%) and long-term...

Among the solid electrolytes for solid-state Li batteries, polymer electrolytes are actively explored on the basis of the good interfacial contact and easy making, while it is still constrained by slow ionic transport and low lithium ion transference number. Herein, functional carbon dots-based Li + conductor (CD-Li) is designed to improve the dynamics and selectivity of Li + transport in polyethylene oxide (PEO) electrolyte. High ionic conductivity (1.0 × 10 −4 S/cm, 25 °C) and Li + transference number (0.60) were successfully achieved within the CD-Li-based PEO composite electrolyte, which could be attributed to the enhanced chain movement and the limited motion of anion. Moreover, the characteristics of big volume of individual anions of CD-Li can provide more free Li + . As well, benefiting from the existence of F atom in the CD-Li, in-situ constructed LiF-containing interfacial layer is in favor of maintaining the interface stability and facilitating the rapid transmission of Li ions. The composite electrolyte with CD-Li can address the ionic conductivity issues accompanied with strengthening the interfacial stability. The distinctive composite electrolyte realizes the stable cycle performance for Li/LiFePO 4 and Li/LiNi 0.5 Co 0.2 Mn 0.3 O 2 batteries. The exploration of multifunctional carbon dot fillers provides new ideas for the efficient development of composite electrolytes.