On The Pollution Content of China’s Trade: Clearing the Air?

This study compares alternative measures of the potential and actual pollution content of China’s trade using an environmental I-O methodology. Using the conventional, potential measure adopted by other researchers, we find that China ‘saves’ on local environmental resources by exporting goods that on average embody less pollution content than imports would if they were produced locally in China. A less positive, assessment of the environmental impact of China’s trade emerges, however, if the assumption of a common technology for producing exports and imports is dropped. Using an actual pollution content methodology for measuring the pollutants embodied in the production of both exports and imports, we find that China is actually a net exporter of embodied pollutants.Trade, pollution content, China

Nanoscale Voltage Enhancement at Cathode Interfaces in Li-ion Batteries

Interfaces are ubiquitous in Li-ion battery electrodes, occurring across compositional gradients, regions of multiphase intergrowths, and between electrodes and solid electrolyte interphases or protective coatings. However, the impact of these interfaces on Li energetics remains largely unknown. In this work, we calculated Li intercalation-site energetics across cathode interfaces and demonstrated the physics governing these energetics on both sides of the interface. We studied the olivine/olivine-structured LixFePO4/LixMPO4 (x=0 and 1, M=Co, Ti, Mn) and layered/layered-structured LiNiO2/TiO2 interfaces to explore different material structures and transition metal elements. We found that across an interface from a high- to low-voltage material the Li voltage remains constant in the high-voltage material and decays approximately linearly in the low-voltage region, approaching the Li voltage of the low-voltage material. This effect ranges from 0.5-9nm depending on the interfacial dipole screening. This effect provides a mechanism for a high-voltage material at an interface to significantly enhance the Li intercalation voltage in a low-voltage material over nanometer scale. We showed that this voltage enhancement is governed by a combination of electron transfer (from low- to high-voltage regions), strain and interfacial dipole screening. We explored the implications of this voltage enhancement for a novel heterostructured-cathode design and redox pseudocapacitors