Burn it, dissolve it, or keep it whole
Lithium ion battery cathodes, the part of a battery that stores its energy while it charges, can be recycled 3 ways. Pyrometallurgy burns the pack in a furnace to recover metals. Hydrometallurgy dissolves it in acid to separate the metals out. Direct recycling keeps the cathode powder structure intact instead of breaking it down, then adds lithium back into it, a process called relithiation. By the time a commercial electric vehicle battery pack is declared worn out, its cathode has typically lost approximately 20% of its usable lithium, according to Argonne National Laboratory.
The heat treatment that closes the gap
Argonne scientists tested 2 heat treatments for putting that lithium back. A single stage treatment at 650 degrees Celsius restored a used cathode to 150 milliamp hours a gram, a measure of how much energy a battery material can hold and release, against 162 for the same material never used. A two stage treatment, first at 350 degrees then at 650, brought the used cathode to 163 milliamp hours a gram, matching or very slightly beating the never used material, and it held nearly 96% of that capacity after 50 charge and discharge cycles.
Relithiation is the heat treatment step that adds lithium back into a used cathode. Single stage and two stage refer to the number of heat treatment steps used.
Show the numbers
| Never used material | 162 |
| Single stage relithiation | 150 |
| Two stage relithiation | 163 |
Why it stays small
A peer reviewed review published in December 2025 names the reason direct recycling has not spread widely, and it is not the chemistry. A recycling line built for one cathode chemistry loses efficiency fast when fed a different one, and taking the process from a laboratory result to an industrial line remains an open problem across the industry.
The 2 facilities that actually exist
Princeton NuEnergy runs the only facility among the 5 sources confirmed to be operating, in Chester, South Carolina, at 5,000 tons a year of processing capacity as of 6 August 2025. The company plans to reach 15,000 tons a year during 2026 and describes 50,000 tons a year as a possible further step with no date attached. The company reports more than 97% recovery yield and claims a 38% cost reduction and a 69% lower environmental footprint, both against what it calls conventional methods, for its own process at that site.
The middle and right bars are Princeton NuEnergy own stated plan and an unscheduled further step, not measured output. The right bar carries no target date.
Show the numbers
| Operating, August 2025 | 5,000 |
| Planned, 2026 | 15,000 |
| Possible further scale up | 50,000 |
Our team's execution has been exceptional, and this facility is our next major advancement in the battery supply chain space.
Dr. Chao Yan, co founder and chief executive officer of Princeton NuEnergy. Source 5.
A second facility, in Commerce, Georgia, is planned and not yet built. The Department of Energy has awarded Princeton NuEnergy a 50 million dollar grant toward it, matched by 60 million dollars from the company, for a total project cost of 110 million dollars. Once built it is planned to process 3,000 tons a year and is expected to create 70 full time manufacturing jobs plus about 100 construction jobs.