Beyond black mass: A critical systems review of lithium-ion and emerging battery recycling — From pre-treatment burden and route chemistry to industrial translation, regulation, and circularity

Battery recycling is no longer only a waste-management issue; it is a strategic industrial capability central to supply security, circular manufacturing, and the sustainability of electrification. Yet the literature remains fragmented. Pyrometallurgy, hydrometallurgy, and direct recycling are frequently compared on inconsistent boundaries; discharge, disassembly, transport, and black-mass quality are acknowledged but often treated as secondary; direct recycling is discussed as though production scrap and end-of-life batteries were equivalent feedstocks; and the implications of rising lithium iron phosphate (LFP), sodium-ion, lithium-sulfur, and solid-state chemistries are often described without being integrated into route-selection logic. This critical review addresses these weaknesses by treating battery recycling as a systems problem rather than a downstream metallurgy problem. A structured review methodology was applied across Scopus, Web of Science Core Collection, Google Scholar, major policy documents, and selected industrial disclosures covering 2018 to June 2026, with earlier foundational sources included where necessary. The article introduces three original analytical contributions. First, it proposes the BRIDGE Framework —Battery/feedstock realism, Route–chemistry compatibility, Impurity and interface burden, Disassembly/logistics burden, Governance and boundary discipline, and End-product circularity retention—as an industrial translation lens. Second, it introduces the Black Mass Penalty Factor (BMPF) , a route-sensitive metric linking black-mass contamination and chemistry heterogeneity to downstream processing burden. Third, it proposes the Dual-Boundary Reporting Protocol (DBRP) , under which quantitative route claims should be reported at both battery-feed and black-mass boundaries to avoid misleading comparisons. The review shows that the principal weakness of the field is not insufficient chemistry but insufficient alignment between feedstock reality, route sensitivity, data transparency, and business constraints. Pyrometallurgy remains the most tolerant route for mixed or poorly sorted feedstocks, but it retains relatively little circular value in lithium and graphite. Hydrometallurgy is the most chemistry-flexible mainstream route and is currently the strongest option for lithium recovery, but it is heavily penalized by reagent demand and black-mass contamination. Direct recycling has the highest circular-value-retention potential, but only when feedstock quality is sufficiently controlled; in practice, direct recycling of manufacturing scrap and direct recycling of end-of-life batteries must be treated as distinct industrial cases. LFP and sodium-ion are likely to shift recycling from value-driven to regulation-driven economics, while sulfide solid-state batteries present a major moisture/H2S pre-treatment challenge that existing recycling infrastructure is poorly prepared to address. The paper concludes with a route–chemistry adaptation matrix, a comparative industrial benchmarking table, and a prioritized roadmap for research and deployment. It is intended as a systems-level reference for sustainability journals, materials researchers, and recycling practitioners who need not only route descriptions, but a reproducible way to judge which route is genuinely scalable and for what feedstock.