In this work, Bhar et al. review the method of spent lithium batteries from spent batteries collection to black mass recycling. Recently, battery recycling has been a hot research topic for sustainable energy and environmental protection. This work provided a detailed description from spent battery collection, to diagnosis, sorting, discharging, and to black mass recovery. Overall, this work will provide some new insights to the community. Therefore I recommend its publication after minor revision.

1. The first and second order headings should be clear. The use of Font style has some confusing This makes it difficult for the reader to clearly understand the affiliations of the various parts. Please, numbering each order heading.
2. In page 7, the comparison of price in NCM 111 and NCM 811 should be updated. Recent price of each type of battery from 2017 till now should be contrasted.
3. In page 8, different discharging process has been summarised. Authors should not simply describe different technologies. What is the applicable condition of each method? How do we choose the right technology from these approaches in commercial applications?
4. For the recovery of black mass, organic solvents are used at high temperatures or under ultrasonic conditions. Is it worth to recycle black mass? Has the energy consumed by organic solvents and high temperatures far exceeded the economic value of black mass? At the same time, the environmental impact of the use of organic solvents should also be considered.
5. In page 16, the title should be added in the table

The manuscript has been well revised and can be published as is.