Abstract：
Recent years have witnessed increasing attempts to track trade flows of critical materials across world regions and along the life cycle for renewable energy and the low carbon transition. Previous studies often had limited spatiotemporal coverage, excluded end-use products, and modeled different life cycle stages as single-layer networks. Here, we integrated material flow analysis and complex network analysis into a multilayer framework to characterize the spatiotemporal and multilayer trade network patterns of the global cobalt cycle from 1988 to 2020. We found substantial growth and notable structural changes in global cobalt trade over the past 30 years. China, Germany, and the United States play pivotal roles in different layers and stages of the global cobalt cycle. The interlayer relationships among alloys, batteries, and materials are robust and continually strengthening, indicating a trend toward synergistic trade. However, cobalt ore-exporting countries are highly concentrated and rarely involved in later life cycle stages, resulting in the weakest relationship between the ore layer and other layers. This causes fluctuations and uncertainty in the global cobalt trade. Our model, linking industrial ecology, supply chain analysis, and network analysis, can be extended to other materials that are critical for the future green transition.
摘要：
近年来，人们越来越多地尝试跟踪世界各地区以及可再生能源和低碳转型生命周期中关键材料的贸易流动。以前的研究通常时空覆盖有限，排除的最终用途产品，并将不同的生命周期阶段建模为单层网络。这里,我们将物质流分析和复杂网络分析整合到多层框架中，以表征1988年至2020年全球钴周期的时空和多层贸易网络模式。我们发现，在过去30年中，全球钴贸易出现了大幅增长和显著的结构性变化。中国,德国,而美国在全球钴周期的不同层次和阶段发挥着举足轻重的作用。合金之间的层间关系，电池,材料坚固耐用，不断加强，表明了协同贸易的趋势。然而,钴矿出口国高度集中，很少参与后期生命周期阶段，导致矿石层与其他层之间的关系最弱。这就造成了全球钴贸易的波动和不确定性。我们的模型，连接工业生态，供应链分析，和网络分析，可以扩展到对未来绿色转型至关重要的其他材料。
