Promoted Li salt dissociation and ion transport of a high-dielectric coating film enable superior lithium battery

Lithium batteries have been widely used in portable appliances and medical and aerospace devices, and further improving the energy density and power density is of great significance to the future development of related technologies. In this work, a high-dielectric polyvinylidene difluoride (PVDF) coating film was designed and realized on Cu foil by a polar solution-induced phase transition method. The PVDF40 coating film prepared at 40 °C displays a high β-phase content (91.68 %) and strong dielectric properties, which can effectively promote the dissociation of Li salt, and exhibits superior ionic conductivity of 4.06 × 10−4 S cm−1 and greatly increased Li transference number of 0.652. The Li-CFx battery with coating film delivers an excellent specific discharge capacity of 947 mAh g−1 at 0.1C, and a superior rate capacity of 634 mAh g−1 even at 5C, attributed to the improved dissociate of lithium salt, Li coordination environment and ion transport. This study demonstrates a dielectric film protection strategy to achieve high-performance lithium batteries.