From Recovery to Qualification: Feedstock Disorder and the Battery-Grade Gap in Lithium-Ion Battery Recycling

Lithium-ion battery recycling is commonly judged by recovery efficiency, yet recovery alone does not establish whether recovered materials can re-enter battery manufacturing. This review treats qualification as the decisive challenge through two linked concepts. Feedstock disorder describes the compositional complexity, provenance uncertainty, and variation in degradation state of materials entering the recycling chain, arising from mixed chemistries, cell designs, ageing histories, pretreatment conditions, and contaminant carryover. The qualification gap is the difference between the measured state of a recovered material and the criterion declared for its intended next use, evaluated attribute by attribute at a stated process stage across composition, bulk structure, particle architecture, surface and interphase, processability, and electrochemical performance, with batch reproducibility as a cross-cutting requirement. Because inherited species act according to concentration, lattice site, chemical state, and spatial distribution, controlled incorporation may be tolerable or beneficial, whereas uncontrolled accumulation may become disqualifying. Recycling is therefore treated as a coupled qualification pipeline in which sorting, pretreatment, recovery, regeneration, and characterization each remove, transform, or pass disorder downstream. Comparative entries are classified by Feedstock Realism Level, with undocumented cases recorded as not reported, and a chemistry-specific matrix separates each measurement from the criterion or benchmark it is compared against and the stage at which that comparison is valid. Sorting, multiscale characterization, and data-driven tools are assessed for reconstructing provenance and generating evidence. Across cathode and graphite recycling, recovery and structural restoration are demonstrated more often than qualification against declared criteria, an imbalance that defines the barrier to closed-loop recycling.