Visual Engineering Achieved with Electronegative Carbon Dots for Highly Efficient Ion Flux Regulation

Abstract Various modification methods for lithium‐metal battery separators have been well explored in the past decades, among which the most common process is to coat modified slurries onto the separators by blade‐coating method. However, the distribution of the slurries is often non‐uniform in this process, while the uniformity usually needs to be detected by electron microscope, which is time and cost‐consuming. To solve this long‐standing technical issue, it focuses on the “visualization” of modification effect with negatively charged carbon dots under UV light, and deeply investigates the ion transport problem caused by the non‐uniform material modification. With this unique “visual engineering” strategy, uniform separator can be easily detected, which further allows for the construction of a uniform negative shielding layer and cation channels. It accelerates the ion transport process, realizes a stable Li stripping and deposition process, and avoids dendrite growth. To this end, in symmetric batteries with different electrolyte compositions, stable operation of 1200 h can be achieved. In addition, negatively charged polysulfide shuttles can be greatly suppressed, thus avoiding the infamous “shuttle effect” in lithium–sulfur batteries. This work provides a new avenue for screening well‐modified separators through “visual engineering”, further accelerating the practical application of series of rechargeable batteries.