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

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.