Considering the safety problem that is caused by liquid electrolytes and Li dendrites for lithium batteries, a new quasi-solid-state polymer electrolyte technology is presented in this work. A layer of 1,4-phenylene bridged polysilsesquioxane (PSiO) is synthesized by a sol-gel way and coated on the electrospun polyacrylonitrile (PAN) nanofiber to prepare a PAN@PSiO nanofiber composite membrane, which is then used as a quasi-solid-state electrolyte scaffold as well as separator for lithium batteries (LBs). This composite membrane, consisting of the three-dimensional network architecture of the PAN nanofiber matrix and a mesoporous PSiO coating layer, exhibited a high electrolyte intake level (297 wt%) and excellent mechanical properties. The electrochemical analysis results indicate that the ionic conductivity of the PAN@PSiO-based quasi-solid-state electrolyte membrane is 1.58 × 10−3 S cm−1 at room temperature and the electrochemical stability window reaches 4.8 V. The optimization of the electrode and the composite membrane interface leads the LiFePO4|PAN@PSiO|Li full cell to show superior cycling (capacity of 137.6 mAh g−1 at 0.2 C after 160 cycles) and excellent rate performances.
China’s Belt and Road Initiative is a significant regional economic cooperation. This paper uses the Belt and Road Initiative (BRI) as a quasi-natural experiment to investigate the impact of regional economic cooperation on environmental quality. Using difference-in-differences (DID) and a series of robustness checks, we find that regional economic cooperation like BRI deteriorates environmental quality in countries along the Belt and Road. The main reason is that the improving effects on environmental quality in the BRI countries are smaller than in the non-BRI countries after the BRI. The ecological impacts of the BRI exist differences in different countries. The results show that the BRI improves environmental quality in South Asia, and Europe and Central Asia. However, the BRI negatively affects environmental quality in East Asia and Pacific, developing and non-OECD countries. We found that, unlike the BRI, the Green BRI improves environmental quality in countries along the Belt and Road. We also discuss the mechanism of the BRI on environmental quality from foreign direct investment (FDI).
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