Controlled thermal runaway lets lithium-ion batteries recycle themselves using stored energy, cutting external heat, chemicals, and emissions while improving recovery efficiency and economic viability.
(Nanowerk Spotlight) The clean energy transition depends on batteries, and those batteries are becoming a serious environmental problem. Electric vehicles, consumer electronics, and solar storage systems rely on vast numbers of lithium-ion cells built from metals that are expensive to mine and difficult to recover.
Global demand for these batteries is projected to exceed three terawatt hours by 2030, while most packs last only eight to ten years. That means tens of millions of tons of spent cells will be arriving at recycling plants each year. The world does not have unlimited lithium, nickel, or cobalt, which makes recovery essential.
Every cell contains these metals bound in structures that are difficult to separate once the battery is spent. Without efficient recycling, the push toward electrification risks trading one resource pressure for another.
A paper in Advanced Energy Materials (“Thermal Runaway Induced Battery Recycling”) examines a route that aims to cut energy use, reduce chemicals, and improve yields by changing where the heat for processing comes from.
Thermal runaway-induced battery recycling. a) The process of traditional Pyro and Hydro methods and thermal runaway method. b) Materials change during battery thermal runaway. c) Battery materials (black powder) leaching process. d) Energy and chemical consumptions of reportedmethods and thermal runaway methods. e) Battery temperature during thermal runaway. f) Images of a battery during the thermal runaway process. g) Materials recycling efficiency of different recycling methods. (Image: Reprinted with permission by Wiley-VCH Verlag) (click on image to enlarge)
Industry today relies mainly on two routes. Pyrometallurgy melts batteries at temperatures above 1400 degrees Celsius to form metal alloys, which is robust but energy intensive. Hydrometallurgy dissolves shredded cells in acids at lower temperature, which reduces furnace needs but consumes large quantities of reagents and creates liquid waste. Both require multistep pretreatment, and both depend on external energy. Prior efforts to lower burdens have included sulfur or chlorine roasting agents and carbon assisted activation, but overall consumption remains high.
The new study proposes a different starting point. A charged lithium-ion battery already holds a compact store of chemical energy. Under the wrong conditions that energy can be released quickly in a process known as thermal runaway, where internal reactions feed on one another and generate intense heat. The authors show that by triggering and containing this event, the heat produced inside the cell can take the place of furnaces and reduce the amount of chemicals needed later. In effect, the thermal step moves inside the battery.
Simulations and experiments use a 24 ampere hour cell with a nickel manganese cobalt oxide cathode (LiMn0.64Ni0.29Co0.07O2). The peak temperature during the self-heating pulse depends on the state of charge, meaning how much energy remains in the cell.
At 50 percent charge the internal temperature reaches about 515 degrees Celsius in roughly 50 seconds. At 70 percent it rises to about 1100 degrees. At full charge it approaches 1244 degrees. The heat reaches most of the internal stack because reactions occur throughout the electrodes rather than coming from an external surface.
In practice, many discarded batteries still contain some charge. Recharging them to about 70 percent requires only 0.28 megajoule per kilogram of battery material in the model. A trigger device can initiate the event in one cell, after which the reaction propagates through a pack like a chain. External energy input is minimal. These points matter because furnaces are the dominant energy load in conventional lines.
Although the reaction looks violent, much of the valuable mass remains recoverable. Mass retention after the event stays near eighty percent across the studied charge levels, with most losses coming from the electrolyte that burns and evaporates. Gases produced during the pulse displace oxygen and create an oxygen poor environment, which curbs oxidation and helps reduce the cathode to forms that dissolve readily.
At the optimal seventy percent condition, the anode and cathode foils remain intact. Computed tomography shows more loose particles after the event, a sign that cohesion drops and later separation becomes easier.
The chemistry inside the cell shifts in useful ways. The layered cathode oxides reduce to metals or divalent oxides that leach easily in weak acid. The graphite anode, which stores lithium between carbon layers, partly converts to lithium oxide and salts such as lithium hydroxide and lithium carbonate that dissolve in water.
After cooling, simple grinding and sieving recover all copper foil and about eighty seven percent of aluminum foil. The black powder that remains contains graphite and reduced cathode particles with sizes from hundreds of nanometers to tens of micrometers, and it responds to magnets, which offers another handle for separation.
Material extraction proceeds in two steps. First, water washing removes the soluble lithium salts made during the heat pulse and recovers more than sixty percent of the lithium. Second, dilute hydrochloric acid dissolves the remaining lithium and the transition metals nickel, cobalt, and manganese. At seventy percent state of charge, lithium recovery exceeds ninety three percent and transition metal recovery reaches about ninety five percent. The cleaned graphite left after leaching contains less than a few parts per million of residual metals and delivers typical graphite capacity when tested, which indicates it can reenter battery supply chains.
The paper also evaluates consumption and emissions using the EverBatt 2023 framework. Charging to the target state uses at most a few tenths of a megajoule per kilogram, and subsequent separation requires about 0.8 megajoule, which together yields energy savings of 97.8 percent compared with pyrometallurgy and 96.1 percent compared with hydrometallurgy in the modeled line.
Because the cathode is already activated by internal heating, chemical use drops. Under strict test conditions the process needs at most 0.53 kilogram of hydrochloric acid per kilogram of battery and no hydrogen peroxide. Converting energy, chemicals, and material losses to greenhouse gases gives 1.44 kilogram of emissions per kilogram of battery, which the paper reports as a reduction of about 54.6 percent and 44.5 percent relative to pyrometallurgy and hydrometallurgy. Maximum water use of 18.1 liters per kilogram is lower as well.
Economic results follow the mass balance. Because pyrometallurgy does not recover graphite and aluminum foil, its revenues sit lower even when nickel and cobalt yields are strong. Using measured leaching efficiencies, the modeled revenue for the thermal runaway route is about 4.24 dollars per kilogram of battery. After comparable logistics costs and line costs are included, the reported profits are 1.94 dollars per kilogram for the thermal runaway route, 1.14 dollars for hydrometallurgy, and 0.79 dollars for pyrometallurgy. The paper notes that the advantage holds even for low cobalt chemistries where graphite and lithium become more important to value.
The scope extends beyond one cathode. Cells based on different nickel manganese cobalt oxide ratios reach very high recovery after the event and two step leaching. Reported lithium recovery is 99.7 percent for NCM333, 99.9 percent for NCM532, and 98.5 percent for NCM811 under seventy percent state of charge, with strong transition metal recoveries as well.
On lithium iron phosphate, which contains no nickel or cobalt, water rinsing alone recovers about 87.7 percent of lithium because a large share migrates into graphite and becomes soluble during the event. The team also shows an overcharge route for lithium cobalt oxide that reaches about 580 degrees Celsius and produces nearly complete recovery of lithium and cobalt at high purity.
Practical steps and safety are addressed. The study describes mechanical and electrical triggers, containment to manage hot gases, and a procedure that cools cells before disassembly. Milling, sieving, and staged leaching follow at specified solid to liquid ratios and concentrations. Across the experiments the full sequence totals roughly 335 minutes. These details signal that the method is not only a concept but a process map that could guide pilot work, with exhaust treatment and containment design called out as priorities.
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