Recycling spent lithium ion batteries by flash joule heating: preferential lithium recovery and Li-phase conversion mechanism under ultra-temperature

• Flash joule heating (FJH) method was developed to recycle spent NCM material. • The Li-phase conversion behavior in a nonequilibrium and high temperature state was firstly revealed. • The phase conversion during FJH reduction process only takes 90 s. • 91.8 % of Li was selectively extracted by water leaching. • The energy consumption of FJH method is 700-fold lower than conventional method. The recovery of spent lithium-ion batteries is crucial for sustainable renewable resources and environmental protection. Low lithium recovery efficiency and high energy consumption are the main problems in current recycling technologies for black mass of spent NCM batteries. This study innovatively applies flash joule heating (FJH) to preferentially recover lithium from industrial raw materials. We firstly revealed the Li-phase conversion behavior under nonequilibrium high temperature state. At the optimal FJH condition (1400 °C, 90 s), main Li-phases convert into Li 2 O and Li 5 AlO 4 , while the transition metals reduce to elemental forms and low-valence oxides. The Li-phase conversion behavior and FJH characteristics matched excellently, enabling 91.8 % selectively lithium extraction by water. Ni, Co, and Mn are recovered via sulfuric acid leaching with over 98 % efficiencies. This innovative method offers a new pathway for recycling spent LIBs in both theory and technology, and extremely appealing for its energy conservation and high recovery efficiency.