Chloride-free deep-eutectic-solvent process for lithium-ion battery cathode recycling

Battery recycling is entering a period of forced regulatory transformation. The EU Battery Regulation, which mandates minimum recycled-content thresholds for lithium, cobalt, and nickel in new cells starting in the mid-2020s, is compelling the industry to move beyond a simple cost-minimization mentality toward chemistries that can meet traceability, purity, and environmental standards simultaneously. That creates a timing window for process innovations that are both cleaner and more selective than the incumbent approaches. This asset addresses exactly that moment: a chloride-free deep-eutectic-solvent (DES) process for leaching lithium-ion cathode black mass that eliminates the principal corrosion liability of chloride-bearing DES systems while preserving the low-temperature, low-energy profile that makes DES recycling attractive in the first place. The core invention is a staged leaching process built on a glycine-betaine hydrogen-bond acceptor (free zwitterion form, carrying no chloride counterion) combined with a non-formate organic acid hydrogen-bond donor — oxalic, malic, or citric acid — and ascorbic acid as a green reductant. The staged protocol extracts lithium preferentially in a first step, then mobilizes nickel, cobalt, and manganese in a second step, giving operators sequential fractions that simplify downstream separation rather than generating a mixed-metal leachate that must be expensively split. This asset sits within the "critical-mineral recovery and recycling separations" portfolio and represents a purpose-built chemical alternative to the chlorinated DES state of the art, with clear freedom-to-operate derived from its specific zwitterionic, chloride-free architecture. The commercial urgency is real: battery recyclers building or retooling capacity today are making 10–15 year equipment investments, and chloride-related corrosion of reactors, piping, and heat exchangers adds material lifetime cost. Choosing a chloride-free process at the design stage avoids that entire cost class. Regulatory compliance with the EU Battery Regulation's recycled-content rules additionally requires documented provenance and minimum recovery efficiencies, both of which a selective staged leach supports better than a single-pot acid dissolution.

The DES system is formulated around glycine betaine used as the free zwitterion — not the hydrochloride salt — which is the defining structural choice of the invention. Betaine (trimethylglycine) is a natural, bio-derived zwitterion that forms hydrogen-bond networks with organic acid donors at mild temperatures without requiring a chloride anion to balance charge. When conventional DES art uses choline chloride as the hydrogen-bond acceptor, or betaine-HCl as a betaine source, chloride is introduced into the leach medium and migrates into process streams and equipment surfaces. The present invention eliminates this by specifying the free zwitterion form and pairing it with organic acid hydrogen-bond donors (oxalic, malic, citric) that similarly carry no chloride. Ascorbic acid serves a dual role: as a mild reductant it reduces Mn(IV) and Co(III) in the cathode lattice to more soluble lower-valence species, driving dissolution at lower temperatures and without the need for H₂O₂ or sulfite reagents commonly used in acid leach processes. The staged leaching sequence is mechanistically significant. Lithium in layered NMC (nickel-manganese-cobalt oxide) cathode materials occupies interlayer sites that are geometrically and chemically distinct from the transition-metal sites. A first-stage leach at controlled pH, temperature, and DES concentration selectively mobilizes Li⁺ while leaving the transition-metal oxide framework partially intact. A second stage, potentially at elevated temperature or altered acid concentration, then dissolves nickel, cobalt, and manganese. The selectivity exploits the relative thermodynamic stability of the transition-metal sublattice versus the interlayer lithium — an effect computable in principle but demonstrated here through ab initio molecular dynamics simulation and rationalized through the known electrochemical potentials of the constituent metals. Computational work on this system was conducted at two levels. Molecular dynamics simulations of a betaine-oxalic DES formulation (labeled WE6 and WE15 in the internal simulation registry) characterized the solvent structure, hydrogen-bond network density, and transport properties of the DES phase — establishing that the system forms a cohesive eutectic rather than a simple solution, with betaine and oxalic acid in close coordination. An ab initio molecular dynamics trajectory of an NMC811 surface in contact with the DES (labeled WE10) produced a result that deserves candid treatment: over the simulation window explored, no surface dissolution events were observed. This is honestly disclosed rather than suppressed — the absence of dissolution in the short AIMD trajectory does not contradict the process chemistry, because DES leaching of oxide cathodes is understood to be chemistry-driven (proton attack on the lattice, aided by the reductant) rather than thermally driven desorption, and AIMD trajectories of tens of picoseconds routinely undersample rare activated events. The simulation is better understood as a structural and thermodynamic probe of the surface-DES interface than as a kinetic dissolution assay. A separate, extended bulk AIMD trajectory confirmed that the DES phase itself is dynamically stable over longer timescales, showing no phase separation, crystallization, or decomposition of the solvent components. The honest open gate is bench-scale leach yield data: actual recovery percentages for Li, Ni, Co, and Mn under industrially relevant conditions (solid-to-liquid ratio, temperature, time, particle size) have not yet been disclosed in this asset, and that validation step is what converts computational plausibility into a licensable, proven process claim. The choice of NMC811 (80% Ni, 10% Co, 10% Mn) as the simulation target is strategically appropriate: NMC811 is the dominant high-energy cathode chemistry in current EV batteries and is therefore the most commercially relevant black mass composition a recycler will encounter at scale in the near term. The high nickel content also makes chloride corrosion particularly problematic, since NiCl₂ species formed in chloride-bearing leaches can contaminate product streams and require additional purification.

The addressable market for lithium-ion battery recycling chemistry and process licensing is estimated at $1–5 billion, a range that reflects genuine uncertainty about the pace of EV adoption, battery second-life economics, and regulatory enforcement timelines, but captures the meaningful scale of the opportunity. Global lithium-ion battery recycling capacity is expanding rapidly — major investments in black mass processing are underway in Europe, North America, and Asia — and the chemistry used to leach cathode materials is a recurring operating expenditure and a licensable process step. Process licensors in adjacent hydrometallurgy fields (copper SX-EW, nickel refining) have historically captured royalty rates in the 1–5% of recovered-metal-value range; applied to the volumes of lithium, cobalt, nickel, and manganese flowing through recycling circuits under EU Battery Regulation mandates, even a fraction of that economics is substantial. The primary buyers are battery recyclers — companies operating black mass processing facilities that accept end-of-life EV packs, consumer electronics cells, and manufacturing scrap. These range from pure-play recyclers (Umicore Battery Recycling, Li-Cycle, Redwood Materials, Retriev Technologies) to integrated battery manufacturers who are building captive recycling capacity (CATL, LG Energy Solution, Samsung SDI have all announced recycling investments). The EU Battery Regulation's recycled-content mandates — requiring minimum percentages of recycled lithium, cobalt, and nickel in new cells from 2027 and 2031 onward — create a regulatory compliance driver that is distinct from and additive to the pure economics of metal recovery. Recyclers selling into the EU supply chain need documented, traceable process chemistry that achieves threshold recovery rates; a process that meets those thresholds and also eliminates chloride corrosion liabilities is differentiated on two independent dimensions. Royalty and licensing logic for a process asset of this kind can follow either a per-tonne-of-black-mass-processed fee structure or a percentage of recovered-metal value. The staged selectivity of the process — producing separate lithium and transition-metal fractions — also creates value in simplifying downstream solvent extraction or precipitation steps, which could support a licensing argument that covers not just the leach step but the integrated separation train.

chloride-free reduces equipment corrosion + supports EU recycled-content thresholds

zwitterionic chloride-free HBA + no formate/chloride donor + staged Li-first sequence

The most natural acquirers or licensees are battery recycling operators who are actively scaling hydrometallurgical processing capacity and who sell into the European supply chain where recycled-content compliance creates an independent commercial driver. Companies like Umicore (whose Battery Recycling Solutions division operates at industrial scale in Europe), Li-Cycle (with North American and European operations), and Redwood Materials (which has announced European expansion) all have the technical staff to evaluate and integrate a new leach chemistry and the commercial incentive to differentiate on chloride-free, regulation-friendly process credentials. Integrated battery manufacturers building captive recycling — CATL's Brunp subsidiary, LG Energy Solution's recycling joint ventures, Samsung SDI's recovery operations — represent a second buyer class that would value the IP defensively as well as commercially, since owning the chloride-free DES recycling whitespace prevents competitors from claiming it. A third category of strategic buyer is specialty chemical companies supplying reagents to the battery industry — companies like Solvay, Lanxess, or Evonik that sell process chemicals to recyclers and might license or acquire the process IP to bundle with betaine or organic acid supply agreements. Equipment manufacturers who supply reactors and leach vessels for black mass processing could also find value in the chloride-free claim, since it directly addresses the corrosion problem that limits reactor lifetime and drives capital cost in chloride-bearing DES and acid leach configurations.

The principal technical risk is the unresolved bench leach yield question. The computational work establishes that the DES system is physically and chemically sensible, but the actual recovery percentages — and particularly whether the staged Li-first selectivity holds at industrially relevant solid-to-liquid ratios and temperatures — are not yet demonstrated. It is possible that lithium selectivity in the first stage is incomplete, requiring additional separation steps that erode the simplification advantage of the staged protocol. It is also possible that oxalic acid, the most extensively simulated donor, forms insoluble oxalate precipitates with calcium or other impurities in real black mass streams, complicating the process. These are manageable risks that bench experiments can resolve, but they are real and should inform valuation. The competitive and regulatory risk landscape is also worth acknowledging. The EU Battery Regulation creates urgency, but it also attracts well-funded incumbents and new entrants to the same chloride-free recycling space. If a major recycler or chemical company develops and patents an alternative chloride-free leach — for example, based on choline acetate or a phosphonium DES — the whitespace this asset occupies could become more crowded. The claim's defensive negative limitations (excluding choline-chloride, betaine-HCl, and formate donors) protect against the specific prior art, but do not foreclose all possible alternatives. The roadmap to de-risking is straightforward: bench leach yield experiments (probably achievable at university or contract research scale in 3–6 months), followed by a continuation prosecution strategy that adds process parameter claims once yield data is in hand, and a targeted prior art watch in the DES recycling space to catch competing filings early.