Lithium (Li) is the lowest density metal, and therefore an optimal element in most battery designs1,2. With the increasing demand for Li, metallurgical techniques using excess acid leaching of mineral ores are common. However, these techniques are limited by complex, multi-step processes with adverse environmental impacts caused by secondary waste streams1,3. Here, we show that flash Joule heating (FJH) can convert the earth-abundant Li ore, alpha-spodumene, into beta-spodumene in seconds, making LiCl extractable with 1 M HCl (Method A). Even more simply, we show that a one-step FJH of alpha-spodumene under an atmosphere of Cl2 (FJH-Cl2) can afford high-purity and high-yield LiCl in seconds without any acid treatment (Method B). This capitalizes upon the lower DeltaGform of the LiCl over the competing aluminum and silicon chlorides. Spodumene undergoes the FJH-Cl2 reaction at 1550 °C in seconds, whereupon LiCl immediately distills from the remaining non-volatile aluminum oxide and silicon oxide. LiCl with a 96% purity and 94% yield can be achieved in this rapid one-step process, enormously reducing costs and waste emissions. Local processing with FJH-Cl2 can dramatically lessen the complexity and cost in obtaining Li, obviating remote mining, and facilitating the world’s progression toward cleaner renewable energies2,3.

Flash Joule heating has been used as a versatile solid-state synthesis method in the production of a wide range of products, including organic, inorganic, and ceramic products. Conventional flash Joule heating systems are large and customized, presenting significant barriers in the cost of assembly, the expertise needed to operate, and attaining uniformity of results between different systems. Even laboratory-scale flash Joule heating systems struggle to operate above 10-gram capacity, and they suffer poor temperature controllability. We present here the use of commercial off-the-shelf arc welders as a superior alternative to standard flash Joule heating systems due to their low cost ($120), ease of use, compact size, high temperature controllability, and tunability. We demonstrate gram-scale synthesis of a variety of organic and ceramic species using these systems. With the addition of a new reactor configuration for only $260, we scale up synthesis of these products to record rates for laboratory scale, achieving a production rate of 3 kg/h for graphene, and kg/day production rates for SiC, carbon nanotubes, SnSe2, and SnS¬2.

The development of next-generation in-memory and neuromorphic computing can be realized with memory transistors based on two-dimensional (2D) ferroelectric semiconductors. Among these, In2Se3 is the most interesting since it possesses ferroelectricity in 2D quintuple layers. However, synthesis of large amounts of In2Se3 crystals with the desired phase has not been previously achieved. We demonstrate here the gram-scale synthesis of α-In2Se3 crystals using a flash-within-flash Joule heating method. This approach allows the synthesis of single-phase α-In2Se3 crystals regardless of the conductance of precursors in the inner tube and enables the synthesis of gram-scale quantities of α-In2Se3 crystals. We then fabricate and use α-In2Se3 flakes as a 2D ferroelectric semiconductor FET artificial synaptic device platform. By modulating the degree of polarization in α-In2Se3 flakes according to the gate electrical pulses, these devices exhibit distinct essential synaptic behaviors. Their synaptic performances show excellent and robust reliability under repeated electrical pulses. Finally, we demonstrate that the synaptic devices achieve an estimated learning accuracy of up to ~87% for Modified National Institute of Standards and Technology patterns in a single-layer neural network system.

Sustainable manufacturing that prioritizes energy efficiency, minimal water use, scalability, and the ability to generate diverse materials is essential to advance inorganic materials production while maintaining environmental consciousness. However, current manufacturing practices are unable to meet these requirements. Here, we describe a new flash-within-flash Joule heating (FWF)—a non-equilibrium, ultrafast heat conduction method—to prepare 13 transition metal dichalcogenides (TMD) and 9 non-TMD materials, each in under 5 seconds while in ambient conditions. FWF achieves enormous advantages in facile gram scalability and in sustainable manufacturing criteria when compared to other synthesis methods. Also, FWF allows the production of phase-selective and single-crystalline bulk powders, a phenomenon rarely observed by any other synthesis method. Furthermore, FWF-made MoSe2 outperformed commercially available MoSe2 in tribology, showcasing the quality of FWF-made materials. The capability for atom substitution and doping further highlights the versatility of FWF as a general bulk inorganic materials synthesis protocol.

Metal recycling plays a crucial role in mitigating the critical metals shortage and reducing reliance on primary mining. Current liquid hydrometallurgy involves significant water and chemical consumption with troublesome secondary waste streams, while pyrometallurgy lacks selectivity and requires substantial energy input. Here we develop an electrothermal chlorination and carbochlorination process, and a specialized compact reactor, for the selective separation of individual critical metals from electronic waste. Our approach uses programmable, pulsed current input to achieve precise control over a wide temperature range (from room temperature to 2400 °C), short reaction duration of seconds, and rapid heating/cooling rates (103 °C s-1) during the process. The method capitalizes on the differences in the free energy formation of the metal chlorides. Once conversion to a specific metal chloride is achieved, that compound distills from the mixture in seconds. This allows for both thermodynamic and kinetic selectivity for desired metals with minimization of impurities.

Rare earth elements (REEs) are indispensable in modern technologies, but their supply chain faces challenges due to limited geographical availability and political difficulties. Recycling REEs from industrial waste provides a sustainable alternative to mining, promoting a circular economy and reducing environmental impacts. The mainstay approaches for REE recovery, hydrometallurgical and pyrometallurgical methods, can be inefficient, consuming high energy and generating large aqueous and acid waste streams. Here, we introduce flash Joule heating (FJH) combined with chlorination (FJH-Cl2) as an efficient method for REE separation and recovery by capitalizing on the free energies of formation (DGform) of the metal chlorides and the boiling points of those metal chlorides. FJH-Cl2 enables high-purity (>90%) and high-yield (>90%) REE recovery from waste magnets in a single step. Life cycle assessment (LCA) and techno-economic analysis (TEA) show that this process reduces the number of steps by 3x while reducing energy consumption by 87%, greenhouse gas (GHG) emissions by 84%, and operating costs by 54% while eliminating water and acid use by 100% compared to traditional methods. This offers an environmentally friendly and economically viable pathway for sustainable REE recycling and recovery.