Decoupling Li-ion conduction and solvation structure in deep eutectic electrolytes for high-voltage lithium-ion batteries.

As a promising deep eutectic quasi-solid electrolyte (DES) for Li-ion batteries, the application of dimethyl sulfone (DMS) is limited by its stability at the electrode-electrolyte interface. A common strategy to address this issue involves introducing additional anions into the Li-ion (Li) solvation sheath to stabilize the interphase. However, this approach often comes at the expense of ionic conductivity, which can negatively impact battery performance. In this work, a strategy to decouple Li conduction and coordination structure is proposed. The introduction of lithium difluoroxalate borate (LiDFOB) promotes an anion-rich Li solvation sheath, which facilitates the formation of stable interphases. More importantly, the incorporation of polyvinylidene fluoride (PVDF) frameworks regulates localized coordination structures and constructs fast Li transport channels, liberating the movement of Li from the constraints of their sluggish solvation clusters. As a result, this hierarchical regulation strategy not only achieves improved ionic conductivity, enabling high-rate operation, but also ensures the formation of stable interphases on 4.6 V LiCoO cathode and graphite anode, exhibiting exceptional high-voltage operation stability for DESs. This work presents a promising approach to addressing critical challenges of DESs by achieving a balance between conductivity and interfacial stability, providing significant insights for their practical application.