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 LiCoO2 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.