Once batteries reach their end-of-life (EoL), they are expected to be collected, dismantled, and shredded into black mass (BM) which includes wealth amounts of critical metals. BM can be regarded as a kind of urban mines, where recyclers extract critical metals and reintroduce them into new battery manufacturing. Focusing on the BM, this article discussed the necessity of BM recovery and current recycling situations. Although the benefits of recycling are commonly agreed upon, there remain still many challenges and issues to overcome. The BM market is still in its infancy, relevant regulatory frameworks need to be updated with the widespread use and advancement of lithium-ion batteries (LIBs). Current BM-producing and processing technologies still have room for large improvements in terms of economic feasibility and sustainability that in the end requires efforts from both researchers and industrial stakeholders with growing interests and patient engagements.