Princeton NuEnergy ($21M for lithium battery recycling)

Princeton NuEnergy develops lithium-ion battery recycling solutions. It was spun out of Princeton University in 2019 and has received $21M in total funding. The company aims to develop a closed-loop, domestic supply chain for lithium-ion batteries and manufactures battery components using recycled batteries.

Challenges: lithium battery recycling

Lithium ion batteries have become the battery of choice for rapidly expanding electric vehicles markets. This increases the demand for lithium, graphite, cobalt, and nickel, which may exceed the availability of virgin materials.

Recycling spent batteries is a crucial step in addressing stringent environmental regulations and conserving resources, as well as minimizing the negative effects of mining/brine extractions for virgin metals, raw material transportation, and energy consumption. Therefore, there is a significant interest in the development of new technologies for recycling and recovering valuable materials from used lithium ion batteries.

Currently, industrial recycling of lithium ion batteries relies on high temperature pyrometallurgical or hydrometallurgical methods to recycle valuable elements such as Li, Ni, and Co. These methods involve high temperatures and intensive chemical processes, which result in substantial energy consumption, chemical waste, and expensive operating cost. Thus, there remains a need for new strategies that enable sorting, purification, and regeneration of cathode materials from used lithium ion batteries, as well as the addition of new functionality to improve cathode material performance.

Princeton NuEnergy’s solution

Princeton NuEnergy developed a lithium ion battery recycling technology that combines a low-temperature plasma-assisted separation and purification process with a gas-phase material regeneration process. The technology enables sorting, plasma purification, and regeneration of aged cathode materials without completely destroying the compounds, and it drastically reduces energy and chemical consumption, recycling time, and costs in comparison to current industrial pyrometallurgical and hydrometallurgical processes.

Princeton NuEnergy lithium ion battery recycling process
Princeton NuEnergy lithium ion battery recycling process.

Particle separation and purification system

Low-temperature plasma-assisted separation and purification system is depicted in the following figure.

Princeton NuEnergy cyclone-plasma separator.

The system consists of the following elements:

The jet mill is fed shredded lithium ion batteries and gas to produce a mixture of material particles and gas. Before plasma treatment, material aggregation is broken up by jet milling.

Between the jet milling equipment and the plasma reactor, a cyclone separator (cyclone separator I) is used to increase the solid to gas mass ratio and decrease pressure by removing the majority of the gas produced by the jet milling apparatus. This high mass loading and low pressure create favorable conditions for enhancing plasma uniformity and treatment efficiency. The concentrated materials in the remaining flow exit the separator’s bottom and then enter the  cyclone-plasma reactor.

A dust remover removes excess gas from cyclone separator I.

A gas exchanger supplies heated gas that is combined with the output of  cyclone separator I’s bottom.

The concentrated and heated particle gas mixture is delivered to a plasma reactor integrated within a cyclone separator (cyclone separator II). Plasma is capable of removing surface impurities from particles.

A vortex finder coupled to the cyclone separator II receives a mixture of a small quantity of nanoparticles and gas. Nanoparticles are collected for the subsequent material recovery procedures.

At the bottom of the cyclone separator II, a large portion of the microparticles are collected for the subsequent material recovery procedures.

Particles recovery systems

Long-term cycling degrades the cathode materials of lithium-ion batteries (e.g., ion mixing in the crystal structure, growth of inactive phase, physical detachment from the current collector, and particle cracking). Before the full capacity can be recovered, the collected nanoparticles from the vortex finder need to be reprocessed to restore their morphology and crystallinity.

In addition, long-term cycling gradually increases the amount of trapped lithium, diminishing the battery’s capacity. The collected particles are lithium-deficient. Material structural changes also occur due to the site mixing of lithium and nickel, oxygen loss, or the degradation of the surface layers. Therefore, the collected materials from the cyclone-plasma separator need to be regenerated.

Princeton NuEnergy developed a new gas-phase process that is suited for morphology restoration, chemistry modification, and relithiation.

As shown in the following figure, the reactor system consists of a spray injector, a particle-gas preheating chamber, and a cyclone separator with an optional plasma discharge at the bottom of the cyclone.

Princeton NuEnergy material recovery reactor
Princeton NuEnergy material recovery reactor.

A spray pyrolysis reactor is equipped with a jet stirring system. A plurality of jet nozzles supply hot air jets along the path of the droplet jet for drying the droplets. The hot gas jets can generate a rapid turbulent motion to mix the hot gas and droplets uniformly, enabling uniform heating and reducing the adhesion of wet particles to the wall. In the particle-gas preheating chamber, the particles are dried before being delivered to the cyclone.

As the particle approaches the bottom of the cyclone, friction with the wall causes it to gradually lose momentum. A high-temperature plasma torch is discharged at the bottom of the cyclone separator. The slowed particle movement increases the plasma processing time and efficiency. A concurrent gas jet  is applied at the end of the cyclone to prevent the particles from adhering on the wall. It also aids in mixing gas and particles evenly for uniform plasma discharge.

There are two reasons why Princeton NuEnergy’s reactor systems are innovative:

  1. The particle-gas preheating chamber is equipped with gas jets that induce vortices in four distinct directions. The vortices improve mixture uniformity and residence time distribution significantly. This uniform mixing and heating contribute to the production of high-quality, spherical particles with a narrow size distribution.
  2. Instead of applying a plasma torch or jet at the beginning of the droplets/aerosols spray, as is common with other technologies developed for material synthesis, Princeton NuEnergy’s plasma jet is placed at the bottom of the cyclone to treat materials. Direct coupling to a plasma jet to the spray is inefficient because most of  the plasma’s energy is wasted in drying the droplets and discharging the gas phase. In Princeton NuEnergy’s innovative solution, the preheating chamber is intended to dry the particles using hot gasses (150-200°C), and the cyclone removes the gasses (>95%) from the particle stream.

Morphology recovery and chemistry modification

To recover the morphology of nanomaterials, a spray solution containing nanoparticles and Li precursors, such as LiOH and LiNOs, is prepared and used.

A suspension solution containing chemical precursors, such as nickel and cobalt precursors, and particles is prepared and sprayed if the reactor is used for chemistry adjustment.

After the droplets from the spray nozzle enter the jet-stirred heating zone, the solvent in the droplet evaporates under control. Solid spherical particles can be produced at low temperatures (150-250°C) and residence times of 5-10 seconds. The newly formed solid particles are composed of small nanoparticles and precursor compounds that bind the nanoparticles together.

After the particles are dried, they are carried by the gas stream to the cyclone separator, where they are separated from the gasses and then transferred to a plasma torch zone.

In the plasma treatment region, the thermal energy from the plasma torch can cause the decomposition of the precursor compounds in the particles into oxides, which can form strong binding to bind all the small nanoparticles within the particle. After decomposition, the precursor particles become amorphous or less crystalline.

In order to improve crystallinity and increase the particle size, the particles are annealed at a higher temperature of 700-800°Cin a tube furnace.


A spray solution containing Li precursors, such as LiOH and LiNOs, and microparticles is prepared and used.

After the droplets enter the jet-stirred heating zone, the solvent in the droplet evaporates under control. Solid spherical particles can generally be obtained at low temperatures (150-250°C) and residence times of 5-10 seconds. The Li precursor coated cathode materials are collected by a cyclone separator under low working pressure.

After evaporation of the solvent, the dried particles further undergo a two-step annealing process in a rotating furnace for relithiation.

The particles are first heated at moderately high temperature (150-500°C) for 30 mins to 5 hours in air or oxygen flow. The Li precursors melt on the surface of microparticles and a thin layer of molten shell is formed. The relithiation normally takes several hours. Rotating of the molten Li precursor coated cathode materials improves the heating uniformity for a better relithiation. This diffusion of Li ions from the surface to the subsurface is driven by the thermal energy and chemical potentials of the highly concentrated Li at the molten shell.

After relithation, the heating temperature rises to 700-800°C. This high temperature treatment normally takes 5 to 10 hours. After thermal treatment, the crystal structure and morphology are recovered. Oxygen flow is typically required to oxidize the aged cathode materials (Ni2+, Co2+) to the higher oxidation states (Ni3+, Co3+).

Compared to other relithiation processes, this micro-molten shell technology has the following benefits:

  1. Uniform and deep relithiation: the uniform coating layer ensures the shortest distance for surface Li to diffuse to subsurface Li-defect sites;
  2. Low cost and easy processing step: since only a stoichiometric amount of Li is needed to form the shell, the Li utilization efficiency is high. No washing or separation processes are needed to remove excess Li . The conventional molten salt relithiation method requires significantly more Li to form a liquid phase. The handling of regular molten salt is difficult, thus not a good option for the industrial scale process. The micro-molten shell method overcomes this drawback without forming a bulk liquid phase.

Princeton NuEnergy Patent

  • WO2022109453A1 Systems and methods for lithium ion battery cathode material recovery, regeneration, and improvement

Princeton NuEnergy Products

Princeton NuEnergy produces high quality cathode and anode materials by recovering and regenerating battery batteries from aged lithium-ion batteries. The products including commonly used LCO, LFP, NCM, NCA materials, and graphite, exhibit similar or even better performance than commercially available materials. Additionally, the materials can be further modified and upgraded via a surface coating, doping, and up-cycling. Princeton NuEnergy’s novel recycling process also produces other products, including copper, aluminum, and plastics.

Princeton NuEnergy Funding

Princeton NuEnergy has raised a total of $21.4M in funding over 4 rounds, including two Grant rounds, an Angel round, and a Seed round. Their latest funding was raised on Nov 18, 2022 from a Grant round.

The funding types of Princeton NuEnergy.
The funding types of Princeton NuEnergy.
The cumulative raised funding of Princeton NuEnergy.
The cumulative raised funding of Princeton NuEnergy.

Princeton NuEnergy Investors

Princeton NuEnergy is funded by 8 investors, including Wistron Corporation, Technology Development Fund, WorldQuant Ventures LLC, AIBasis Fund, Cleantech Open, Shell Ventures, Greenland Technologies Holding, and US Department of Energy. Wistron Corporation and US Department of Energy are the most recent investors.

The funding rounds by investors of Princeton NuEnergy.
The funding rounds by investors of Princeton NuEnergy.

Princeton NuEnergy Founder

Chao Yan is Founder.

Xiaofang Yang, Yiguang Ju, and Bruce E. Koel are Co-Founder.

Princeton NuEnergy CEO

Chao Yan is CEO.

Princeton NuEnergy Board Member and Advisor

Yiguang Ju and Bruce E. Koel are Advisor.

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