Summary
Machine learning has been heavily researched and widely used in many disciplines. However, achieving high accuracy requires a large amount of data that is sometimes difficult, expensive, or impractical to obtain. Integrating human knowledge into machine learning can significantly reduce data requirement, increase reliability and robustness of machine learning, and build explainable machine learning systems. This allows leveraging the vast amount of human knowledge and capability of machine learning to achieve functions and performance not available before and will facilitate the interaction between human beings and machine learning systems, making machine learning decisions understandable to humans. This paper gives an overview of the knowledge and its representations that can be integrated into machine learning and the methodology. We cover the fundamentals, current status, and recent progress of the methods, with a focus on popular and new topics. The perspectives on future directions are also discussed.
We report a piezoelectric mechanism to stop dendrite growth, which enables inherently safe lithium metal battery. For demonstration, a polarized piezoelectric polyvinylidene fluoride (PVDF) film is used as a separator. When the film is deformed by any local protrusion because of surface instability of the deposited lithium, a local piezoelectric overpotential is generated to suppress lithium deposition on the protrusion. Our optical in situ cell shows that a polarized PVDF film ensures lithium metal depositing to form a flat surface, even when starting from an uneven surface. In contrast, a nonpolarized PVDF film cannot suppress dendrite growth under the same condition, with dendrite penetrating the separator within minutes. Coin cell results further confirm that the piezoelectric mechanism is effective in practical battery applications. Analysis suggests that the effectiveness of piezoelectric mechanism by over-potential is easily 10 4 stronger than the maximum physical limit of mechanical blocking from infinitely stiff blocking materials, suggesting a new direction of material innovation.
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