Nickel-metal hydride (NiMH) batteries are among the most recyclable battery chemistries in commerce: their principal materials are nickel and steel with recoverable cobalt and rare-earth alloys, and the recovery routes are mature at industrial scale. This paper follows a spent NiMH cell from collection bin back to raw material and connects each stage to the requirements of Regulation (EU) 2023/1542.
Separately collected batteries arrive at sorting facilities, where automated and manual sorting separates NiMH from alkaline, NiCd, lithium and lead-acid streams — chemistry purity matters because cross-contamination degrades recovered material quality. NiMH cells are then fully discharged to eliminate residual energy before mechanical processing. Unlike lithium cells, NiMH uses aqueous potassium-hydroxide electrolyte and cannot enter thermal runaway, so handling, shredding and storage carry a lower fire-risk burden, which reduces insurance, bunker and processing costs — one reason treatment facilities accept NiMH streams readily.
Shredding under inert gas or water spray breaks cells into fragments; magnetic separation pulls out nickel-plated steel cans as a clean ferrous fraction; sieving and density separation isolate the electrode fines ("black mass") containing nickel hydroxide, hydrogen-storage alloy and small cobalt content; the potassium-hydroxide electrolyte is neutralised and treated in the water circuit. The output streams — steel, electrode black mass, separator/plastic fraction — are each weighed to compute process yield against Annex XII recovery targets.
Two routes process the electrode fraction. Pyrometallurgy smelts it into a nickel-iron or nickel-cobalt alloy matte, typically feeding stainless steel production — robust and high-throughput, though rare earths report to slag. Hydrometallurgy leaches the black mass in sulfuric acid, removes iron and impurities, then separates nickel, cobalt and rare earths by solvent extraction, ion exchange or selective precipitation, producing nickel sulfate crystals or nickel metal pure enough for battery-grade foam and alloy, and rare-earth concentrates (lanthanum, cerium, neodymium, praseodymium) that return to hydrogen-storage alloy production. Modern integrated lines combine both: pyrometallurgical concentration followed by hydrometallurgical refining, achieving nickel recovery above the 90 % Annex XII target and, in best-practice plants, above 95 %.
Recovered nickel sulfate feeds electrode and foam manufacture; recovered steel re-enters the steel cycle; rare-earth concentrates feed new AB5/AB2 hydrogen-storage alloys. This closes the loop Article 8 rewards: mass-balance-certified recycled nickel becomes the documented recycled content in new covered batteries, counting toward the 6 % (2031) and 15 % (2036) thresholds. For the loop to be creditable, every transfer carries chain-of-custody documentation from licensed treatment facility through refiner to battery maker, and exports of waste follow the waste-shipment regulation — only properly documented recovery counts toward member-state statistics.
Recycling yield is partly decided at the design desk. NiMH design choices that help: standard cell formats that sort cleanly; minimal mixed-metal welding; polymer components identifiable by resin code; avoidance of potting compounds that lock fragments together; clear chemistry and material labeling under Article 13; and Annex XII dismantling information identifying the electrode and current-collector locations. Pack-level protection components (PTC, thermal fuse) should be removable on documented lines. These choices cost little at design time and materially raise end-of-life value.
Weijiang Power designs NiMH cells and packs for clean end-of-life recovery: standard formats, separable construction, documented composition by mass and Annex XII dismantling guidance aligned to the 90/95 % material-recovery targets. Request our recycling dossier with any inquiry — it includes material composition, recommended treatment route, nickel and rare-earth recovery notes and the chain-of-custody information your EU recycling partners ask for.
