Summary

Traditional Certificates of Analysis are most likely to miss five categories of risk in recycled battery metal salts:

• process-derived cations that are not included in the routine metals panel;
• anionic and non-metallic residues that cannot be interpreted from target-metal assay;
• metallic particles whose form and distribution disappear during bulk digestion;
• organic or carbonaceous residues from recycling and purification;
• cross-chemistry markers introduced by changes in battery feedstock.

The issue is not that recycled nickel, cobalt, manganese, or lithium salts are necessarily lower in quality than materials derived from primary resources. A recycled salt can meet its target-metal assay while retaining an impurity fingerprint created by black-mass composition, leaching chemistry, separation reagents, process-water recycling, shared equipment, crystallization, and blending.

For cathode producers evaluating recycled battery chemical raw materials, the relevant question is therefore not simply whether the product is described as battery grade. It is whether the analytical package can detect the impurities that the specific recovery route is capable of introducing.

Why Conventional COAs Are Becoming Less Sufficient

Recovered metals are moving closer to formal battery supply-chain requirements, but regulatory recycled-content rules do not define the impurity limits needed for individual cathode processes.

Article 8 of Regulation (EU) 2023/1542 applies recycled-content requirements from August 18, 2031, to industrial batteries with a capacity greater than 2 kWh, except those with exclusively external storage, as well as electric vehicle batteries and SLI batteries containing cobalt, lead, lithium, or nickel in active materials. For the cathode-related metals discussed here, the minimum recycled shares are 16% cobalt, 6% lithium, and 6% nickel. These requirements are assessed for each battery model per year and per manufacturing plant; they are not chemical specifications for recycled nickel, cobalt, manganese, or lithium salts.

This distinction creates the practical quality problem.

A battery manufacturer may need to increase recovered-metal content without receiving a regulatory answer to questions such as:

• Which sodium result is acceptable for a specific co-precipitation process?
• Should fluorine be controlled as total fluorine or extractable fluoride?
• Can a compliant total copper result hide occasional metallic particles?
• Which feedstock changes require an expanded impurity panel?
• Which qualification tests should remain outside the routine COA?

The existing specification may therefore remain legally usable while becoming technically incomplete.

Published cathode-resynthesis studies are also beginning to show why recovered sulfate streams must be evaluated beyond headline assay. The relevant change is not simply the appearance of more recycled material. It is the need to connect feedstock history, purification chemistry, analytical coverage, and downstream process response.

The Main COA Gaps in Recycled Battery Metal Salts

A conventional COA may report accurate results while still failing to describe the risks created by the recovery route.

Sodium and Other Process-Derived Cations

Sodium is one of the clearest examples of a route marker that may be omitted from a conventional COA.

It can enter a recovered metal stream through sodium hydroxide, sodium carbonate, neutralization, precipitation, washing, or recycled process water. A COA that reports Fe, Cu, Zn, Pb, or a general heavy-metals result may still contain no individual sodium value.

For transition-metal sulfate solutions used in hydroxide precursor co-precipitation, residual sodium may affect:

• washing requirements;
• residual alkali control;
• precipitation conditions;
• mother-liquor management;
• the final precursor impurity profile.

There is no single sodium limit that can be applied to every recycled sulfate. The relevant acceptance level depends on the precursor chemistry, sodium source, washing process, solution recycling, and downstream calcination route.

Potassium, calcium, and magnesium should not automatically become routine release items. They become relevant when process water, neutralization chemistry, filter aids, reagents, or accepted feedstock provide a credible entry path.

A common procurement error is accepting a statement such as “heavy metals comply” without confirming:

• which elements were tested;
• whether results or only limits are reported;
• which method was used;
• whether the value is a specification limit, reporting limit, or typical result.

Fluoride, Chloride, Phosphorus, Sulfur, and Other Non-Metallic Carryover

Recycled battery streams can contain non-metallic residues originating from:

• electrolyte salts and decomposition products;
• fluorinated binders;
• LFP-containing feed;
• leaching acids;
• precipitation and stripping reagents;
• washing chemicals;
• recycled process solutions.

A target-metal assay does not answer these questions. A routine metals panel may also fail to identify the chemical form that matters to the downstream process.

For example:

• total phosphorus is not equivalent to soluble phosphate;
• total sulfur does not distinguish residual sulfate from other sulfur-containing matter;
• total fluorine does not show whether the material contains extractable fluoride or another fluorinated residue.

The method should match the quality decision:

• ion chromatography can assess extractable anions;
• combustion-ion chromatography may support broader halogen screening in suitable matrices;
• total elemental analysis may be appropriate when total phosphorus or sulfur is the control parameter;
• residue analysis may be needed when the contaminant is not fully soluble.

The objective is not to place every possible anion on every commercial COA. Testing should be triggered by the feedstock and purification route.

Aluminum, Copper, and Iron Hidden by Total-Metal Results

Aluminum and copper can originate from current collectors. Iron may enter through casings, shredding systems, pipelines, tanks, filters, tools, or shared processing equipment.

Most COAs report these elements after digestion. This provides total concentration but removes information about physical form.

The same total copper result could represent:

• uniformly dissolved Cu²⁺;
• fine copper oxide particles;
• metallic foil fragments;
• a small number of copper-rich particles concentrated in one package.

These forms may behave differently during salt dissolution, precursor precipitation, filtration, calcination, and cathode resynthesis.

Particulate contamination also creates a sampling problem. A small laboratory portion may not contain the rare particles present elsewhere in a drum, bag, or crystallized batch. Tightening the total copper or iron limit will not resolve the risk if sampling remains unrepresentative.

Two questions must therefore be separated:

1. Is the average elemental concentration acceptable?
2. Is the impurity uniformly distributed and present in a tolerable physical form?

When the second question matters, multi-point sampling, filtration of dissolved material, microscopy of retained solids, or SEM-EDS may provide more useful evidence than another bulk digestion result.

Residual Extractants, Diluents, and Carbonaceous Matter

Hydrometallurgical recovery may involve acids, reducing agents, oxidants, precipitants, complexing agents, solvent-extraction systems, diluents, antifoams, and washing chemicals.

Black mass can also introduce:

• electrolyte-solvent residues;
• binder fragments;
• conductive carbon;
• separator-derived matter;
• lubricants;
• contamination from mechanical processing.

A high target-metal assay does not detect these materials. Loss on drying is also an incomplete substitute because non-volatile organics, thermally decomposing matter, and carbonaceous particles may remain after the test.

Testing should be selected according to the suspected source:

• TOC can provide a broad organic-carbon screening signal in suitable solutions;
• targeted GC or GC-MS may be appropriate when a particular extractant, diluent, or solvent is known;
• filter-residue analysis may be more relevant for carbon or polymer particles;
• thermal analysis can support an investigation but does not identify every residue.

TOC should not be interpreted as proof that a salt is free from all organic process residues. It is a screening parameter, not a complete identification method.

Cross-Chemistry Carryover

A facility processing segregated NMC production scrap creates a different impurity profile from one accepting mixed post-consumer batteries.

Possible route markers include:

• phosphorus and iron associated with LFP-containing feed;
• manganese associated with manganese-rich cathode material;
• aluminum from current collectors or aluminum-containing cathodes;
• silicon from silicon-containing anode streams;
• graphite and conductive carbon;
• fluorine, phosphorus, boron, or sulfur associated with electrolyte systems.

One marker does not by itself prove poor segregation because several sources may be possible. However, a change in a group of markers can indicate that the battery feed, mechanical separation, or purification performance has changed.

Feedstock history therefore becomes part of quality control.

A fixed impurity panel should be reviewed when a recycling operation introduces:

• a new battery chemistry;
• a different cell format;
• a new black-mass source;
• a revised leaching reagent;
• a different purification or crystallization sequence.

Chemical Form and Speciation

Total-element analysis answers how much of an element is present. It does not always explain how that element will behave.

Relevant distinctions may include:

• metallic copper versus dissolved copper ions;
• soluble iron versus iron-rich equipment-wear particles;
• extractable fluoride versus other fluorine-containing residues;
• soluble phosphate versus phosphorus-containing solids.

Full speciation should not become a routine release requirement without a technical reason. It is better used during qualification or deviation investigation when similar total-element results produce different precipitation, filtration, calcination, or cathode outcomes.

A practical rule is:

Use total-element testing for routine control, but investigate physical form or chemical species when total concentration does not explain downstream behavior.

What the NMC811 Evidence Actually Shows

A paper first published in December 2025 and included in the 2026 volume of the Journal of Materials Chemistry A evaluated NMC811 cathodes resynthesized from metal sulfates recovered from spent lithium-ion battery black mass.

One resynthesized material reached 99.6% overall purity while containing higher sulfur, sodium, and iron than commercial references. The recovered-material cathodes showed comparable composition and crystal structure, together with technically promising electrochemical performance. However, the study also associated the residual impurity profile with changes in primary and secondary particle formation, broader particle-size distributions, less compact morphology, and lower packing efficiency.

The study does not show that 99.6% purity is inadequate, nor does it establish universal impurity limits for recycled NMC materials.

It supports a narrower and more useful conclusion:

Overall purity and the process effect of specific residual impurities are separate quality questions.

A recycled salt can therefore pass its headline assay and still require process-level validation before routine cathode use.

Where COA Gaps Create the Highest Validation Risk

Transition-Metal Sulfates Used in Co-Precipitation

Nickel sulfate, cobalt sulfate, and manganese sulfate enter directly into precursor synthesis.

Route-derived cations, anions, particles, or organic residues may affect:

• solution preparation;
• metal complexation;
• precipitation stability;
• filtration and washing;
• particle-size distribution;
• precursor morphology;
• residual sodium or sulfur.

An incoming sulfate may meet assay while the precursor process moves outside its established operating window.

The more useful qualification signal may therefore be a change in precipitation or precursor behavior rather than a failure in the incoming assay.

Recycled Lithium Carbonate and Lithium Hydroxide

Recovered lithium salts require additional screening only where the recovery route creates a credible risk.

Possible checks can include:

• sodium, potassium, calcium, or magnesium;
• chloride and sulfate;
• moisture or hydration state;
• insoluble matter;
• transition-metal carryover.

The intended cathode route determines which of these parameters matter.

Lithium dosing and calcination consistency can be affected by hydration state, carbonate-to-hydroxide balance, moisture uptake, and insoluble contamination. These should not be described as universal defects in recycled lithium salts. They are qualification questions that need to be confirmed against the actual recovery and cathode processes.

High-Nickel and Mixed-Chemistry Production

Ni-rich cathode routes can be sensitive to uncontrolled changes in precursor morphology, surface residues, cation distribution, and calcination behavior.

This does not justify one universal recycled-salt specification for all high-nickel materials. It justifies connecting the incoming impurity profile with the sensitivity of the intended process.

Facilities handling NMC, LFP, LMO, anode material, or multiple black-mass streams face another type of exposure: cross-contamination through shared tanks, filters, dryers, packaging systems, and cleaning operations.

In these plants, impurity control may require:

• campaign sequencing;
• line-clearance criteria;
• wash verification;
• segregated storage;
• retained samples;
• targeted testing after feedstock changes.

A COA cannot compensate for undefined segregation or cleaning controls.

Sample Validation, Trial Production, and Commercial Supply Require Different Evidence

Approving a recycled salt after one laboratory sample passes analysis and cell testing is a significant procurement error.

The risk changes as the material moves from a selected sample to a production campaign and then to routine commercial supply.

Laboratory Sample

The first sample should establish whether the material is technically plausible. It should not be treated as proof of commercial consistency.

Recycled and primary salts should be compared using matched:

• sample preparation;
• digestion or extraction methods;
• reporting units;
• analytical sensitivity;
• application tests.

A measurable difference is not automatically a failure. The objective is to determine whether the difference is controlled and relevant to the intended process.

For transition-metal sulfates, precursor precipitation may provide more useful evidence than an isolated salt analysis. For recovered lithium salts, lithium dosing and calcination response may be the more relevant next step.

Trial Production

Trial production should expose the material to realistic process volume, residence time, mixing, filtration, washing, transfer, storage, and calcination.

A laboratory experiment may not reveal:

• solids accumulating in a transfer line;
• slower filtration at production scale;
• particle segregation during storage;
• mother-liquor recycling effects;
• cleaning interactions with shared equipment;
• gradual impurity effects over a longer campaign.

The trial should have a defined sampling map, reference material, deviation criteria, and approval rule before production begins.

Commercial Supply

Commercial approval requires evidence that the recovery and purification route remains controlled as feedstock, production volume, campaign length, and upstream sources change.

Routine release can use a narrower panel than initial qualification when:

• critical route markers have been identified;
• routine and periodic tests are separated;
• multi-lot trend data are available;
• change-notification triggers are defined;
• investigation methods are agreed for unexplained deviations.

The established high-purity battery chemical quality controls remain relevant, but recycled salts require an additional connection between feedstock route, impurity fingerprint, sampling, and cathode-process response.

Which Tests Should Appear on the Routine COA?

Identifying a possible impurity does not mean it should become a release test for every batch.

A parameter should enter routine release only when the buyer can explain:

1. how it can enter the material;
2. which process or product risk it represents;
3. which method measures it adequately;
4. what evidence supports the acceptance limit;
5. whether every-lot testing adds meaningful control.

This prevents an extended qualification study from becoming an unnecessarily expensive routine COA.

Decision Framework for Recycled Battery Metal Salts

Independent Industry Judgment: Control the Recycled Input, Not Only the Final Assay

Industry discussions often ask whether recycled metal can match the purity of material derived from primary resources. That is necessary, but it is not the most useful qualification question.

A cathode plant does not purchase isolated nickel, cobalt, manganese, or lithium atoms. It purchases a solution, crystal, or powder that reflects dismantling, separation, leaching, purification, crystallization, blending, drying, packaging, and transport.

The target element may be chemically identical, but the impurity pathways are not.

Qualification Work Will Rise Before Sourcing Risk Falls

My judgment is that increasing recycled content will initially increase qualification work.

Buyers will need broader screening during qualification, more representative sampling, controlled production trials, and stronger change management before a recovered stream can enter routine procurement.

That additional effort is not evidence that recycled material is inherently unsuitable. It is the normal cost of qualifying a different production route for a process-sensitive raw material.

Final-Blend Compliance Can Hide Upstream Drift

Blending primary and recovered salts may help control final composition and introduce recycled content progressively. It can also conceal changes in the recovered component.

A final blend may remain within specification while sodium, phosphorus, metallic particles, or organic residues in the recycled input are increasing. The primary stream can dilute the change until the recycled share rises or the primary source changes.

Final-product testing should therefore be supported by:

• trend data for the recovered input;
• an agreed final-blend specification;
• a defined recycled-content range;
• rules for changing the blend ratio;
• requalification triggers after feedstock or process changes.

The overlooked control point is often the recovered component before dilution.

Avoid Turning Every Detected Impurity into a Batch Limit

Once a possible contaminant is identified, buyers may be tempted to specify the lowest available reporting limit for every lot.

That approach can increase testing cost and delay release without proving that the tighter requirement improves precursor or cathode performance.

A more defensible sequence is:

1. identify a credible entry route;
2. measure representative lots;
3. compare results with process behavior;
4. establish a technically justified acceptance range;
5. assign the test to routine release, periodic monitoring, qualification, or investigation.

The long-term value of recycled salts will depend less on passing one optimized sample and more on maintaining a stable impurity fingerprint while feed composition and production volume change.

What Buyers Should Include in the RFQ

A recycled metal salt RFQ should focus on the information that changes the qualification decision:

• accepted feedstock categories and battery chemistries;
• the recovery and purification route;
• the point at which recovered and primary streams are blended;
• routine and periodic impurity panels with methods;
• representative multi-lot trend data;
• notification triggers for feedstock, reagent, equipment, process, or site changes.

The request should also state whether the material is intended for laboratory screening, trial production, or routine commercial supply. Each stage requires different evidence.

Buyers can submit the intended cathode route, feedstock restrictions, impurity requirements, sampling plan, validation stage, and commercial-lot expectations through ChemicalCell’s chemical raw material RFQ.