Evolution characteristics of a Kerr black hole (BH) are investigated by considering the coexistence of disc accretion with the Blandford–Znajek process (the BZ process) and magnetic coupling of the BH with the surrounding disc (MC process). (i) The rate of extracting energy from the rotating BH in the BZ process and that in MC process are expressed by a unified formula, which is derived by using an improved equivalent circuit. (ii) The mapping relation between the angular coordinate on the BH horizon and the radial coordinate on the disc is given in the context of general relativity and conservation of magnetic flux. (iii) The power and torque in the BZ process are compared with those in MC process in detail. (iv) Evolution characteristics of the BH and energy extracting efficiency are discussed by using the characteristic functions of BH evolution in the corresponding parameter space. (v) Power dissipation on the BH horizon and BH entropy increase are discussed by considering the coexistence of the above energy mechanisms.

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Lithium ion batteries have been undergoing rapid development in the global market due to their superior performance. However, the soaring number of lithium ion batteries in the market presents serious disposal challenges at the end of life. Moreover, continuous mining processes are harmful to the environment. From the viewpoint of cleaner production and green chemistry, the efficient recovery and reutilization of spent lithium ion batteries are necessary. In this perspective, the overall process of lithium ion battery recycling, especially the recent advances of hydrometallurgical methods, are summarized, focusing on the leaching, separation, and purification processes. The proper disposal of the waste discharged during the recycling process is proposed, highlighting the mitigation of secondary pollution. In addition, the environmental impact of recycling processes is summarized and thoroughly evaluated by recent life cycle assessment studies, revealing the key role of recycling strategic metal elements toward sustainability in an anthropogenic cycle. Finally, the current challenges in this area are pointed out and perspectives on sustainable approaches, cleaner production, and life cycle assessment are proposed.

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