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The effective recycling of retired LiFePO4batteries serves dual purposes: addressing the resource supply-demand contradiction and mitigating environmental pollution. However, the existing recycling methods for waste LiFePO4batteries often entail high energy consumption, time consumption, complex procedures, or the use of substantial amounts of chemical raw materials, leading to increased recycling costs. Moreover, both methods generate toxic gases or discharge excessive pollutant-containing liquids during the recycling process, posing a risk of secondary pollution. Here, we introduce the application of ultrasound-assisted regeneration in waste LiFePO4cathode material directly. Ultrasound waves generate localized high temperature, high pressure, and intense shock wave jets to repair the lithium vacancy defects and anti-site defects in the waste LiFePO4. Based on the experimental findings, the regeneration of LiFePO4was achieved with impressive results. At an ultrasound power of 500 W and a duration of 50 min, the regenerated LiFePO4displayed a discharge specific capacity of 135.1 mAh∙g−1and an impressive capacity retention of 97 % after 100 cycles at a 1C (1C = 170 mA g−1) current density. This study presents a promising and environmentally friendly approach for recycling and regenerating retired LiFePO4batteries.

Urban water systems are facing various challenges against climate change, impacting cities’ security and their sustainable development. Specifically, there are three major challenges: submersion risk of coastal cities as glaciers melt and sea level rises, more and severe urban flooding caused by extreme weather like intensified storm surge and heavy precipitation, and regional water resource patterns challenged by alteration of spatial distribution of precipitation. Regarding this, two strategies including proactive adaptation and positive mitigation were proposed in this article to realize the reconstruction and optimization of urban water systems, to enhance their resilience, and eventually increase their adaptability and coping ability to climate change. The proactive adaptation strategy consists of 1) construction of sponge cities to accommodate the increased regular rainfall and to balance the alterations of spatial redistribution of precipitation; 2) reconstruction of excess stormwater discharge and detention system to increase capability for extreme precipitation events based on flood risk assessment under future climate change; 3) deployment of forward-looking, ecological, and integrated measures to improve coastal protection capability against inundation risks caused by climate change and sea level rise. The positive mitigation strategy is to employ the systematic concept in planning and design and to adopt advanced applicable energy-saving technologies, processes, and management practices, aiming at reduction in flux of urban water systems, reinforcement in energy conservation and carbon reduction in both water supply systems and wastewater treatment systems, and thus a reduction of greenhouse gas emission from urban water systems.