Self-Dispersing Carbon Nanotubes: Higher Solids, Better Battery Stability?

CNTs are dispersed; “solubility” is usually the wrong development target

For an aqueous CNT product, the useful quantity is the concentration of nanotubes that remain sufficiently dispersed for the intended process. Describing that liquid as a molecular solution can hide differences between individual tubes, small bundles and larger aggregates. A visually uniform black liquid does not establish which population is present.

One self-dispersing route attaches hydrophilic groups to the nanotube surface. When appropriately ionised, surface groups can help resist rebundling in water. Yu and colleagues demonstrated surfactant-free, carboxyl-functionalised individual SWCNT dispersions, with about 80% individual tubes in their characterised sample. Their reported concentration was 0.2 mg/mL after chemical treatment and separation. This supports the feasibility of the route, rather than a universal high-solids specification. [1]

“No added dispersant” is more precise than “additive-free.” Grafted organic groups, counterions and residual processing species may remain. Surface modification also does not automatically eliminate the energy needed to separate CNT bundles; the preparation and purification route must be stated.

Less dispersant does not automatically mean more CNTs per kilogram

Two solids measurements need to be separated:

• CNT concentration in the wet dispersion: nanotube mass divided by total dispersion mass, commonly reported as wt%.
• CNT share of the dried solids: nanotube mass divided by all non-volatile material, which may also include dispersant, grafted groups and other residues.

Consider an illustrative 100 g batch containing 2 g CNT, 1 g dispersant and 97 g water. It contains 2 wt% CNT and 3 wt% total non-volatile material. Replacing the dispersant with water leaves 2 wt% CNT; it only changes the dried composition. Reaching 3 wt% CNT would require adding and successfully processing more nanotubes. This is a mass-balance example, not a proposed product specification.

Higher surfactant-free concentrations have been reported. Wang, Iqbal and Mitra obtained stable aqueous concentrations up to 10 mg/mL after functionalising SWCNTs. That equals 10 g/L or 1% mass/volume; conversion to mass percent requires the dispersion density. Their treatment also shortened the tubes, and the reported membrane conductivity followed thermal annealing. Concentration and retained electrical performance therefore need to be read together. [2]

The practical ceiling is often rheological. Long tubes and bundles can form an entangled network, making a liquid highly shear-dependent or gel-like before a large mass fraction is reached. The relevant target is usable CNT concentration at the customer’s mixing, pumping and coating conditions. SWCNT and MWCNT results should not be pooled as if tube length, diameter and surface area were identical.

Even dispersion efficiency must be measured consistently. Dai and colleagues combined analytical methods to assess dispersed MWCNT concentration and showed why changing the dispersant and the measurement procedure affects the comparison. A nominal amount added to a vessel is not necessarily the amount remaining in the dispersed fraction after separation or storage. [3]

What the battery literature actually establishes

Surface-grafted carbon can improve electrode construction

A 2020 Scientific Reports study used aryl-carboxyl-functionalised carbon, including CNTs, to build conductive coatings on NMC622. The subsequent lithiation of surface groups was part of its design. It reported improved rate performance in lithium-metal cells with a solid polymer electrolyte tested at 50°C. The researchers could not fabricate a satisfactory unmodified-CNT electrode because of aggregation. Consequently, the study is evidence for its combined surface-chemistry and electrode-construction approach; it is not a matched proof that removing dispersant improves commercial-cell cycle life. [4]

Dispersant-free processing has also been explored in NMP

A 2023 Chemical Engineering Journal paper examined oxidation of SWCNTs in a liquid-crystalline phase and subsequent dispersant-free dispersion in NMP for lithium-ion battery applications. Its results support investigating that specific treatment. NMP is not water, however, and the reaction-paste concentration must not be relabelled as the final aqueous product solids. The available evidence does not establish a general water-based concentrate specification. [5]

A useful counterexample: a dispersant can help

A 2025 study used PVP-assisted MWCNT dispersion in a PTFE-fibrillation cathode process, with an ethanol-assisted preparation step. Improved nanotube distribution supported better electrode performance. This is a different processing route, but it directly challenges the claim that every added dispersant is detrimental. The comparison is between complete formulations and electrode structures, not simply “with polymer” versus “without polymer.” [6]

For developers, these papers support a testable hypothesis: a well-designed self-dispersing CNT may form an effective conductive network with fewer free formulation components. They do not establish that the absence of dispersant is, by itself, the cause of better cycling.

The surface modification must earn its place in the electrode

Covalent functionalisation changes the CNT surface and can introduce defects into its conjugated structure. More hydrophilic functionality may improve wetting while changing electrical behaviour. The 2020 study’s Raman and thermal analyses demonstrate substantial grafting and structural change. The right development target is therefore sufficient dispersion with an effective dried conductive network, rather than the greatest possible degree of functionalisation. [4]

The alternative also deserves optimisation. A Langmuir study published online in 2023 and in its 2024 issue achieved effective individual-SWCNT stabilisation with much lower surfactant concentration than conventional formulations, using a specific surfactant-exchange route. Its roughly 0.08% mass/volume figure refers to the surfactant, not CNT solids. That work is dispersion research, not battery cycling evidence. [7]

For a battery formulation, tube length and junction resistance matter alongside surface chemistry. Residual catalyst metals, ash, acidity, counterions and moisture also belong in the specification. A coating made from an aqueous dispersion must meet the electrode process’s drying requirements before cell assembly. A stable concentrate should additionally be tested after mixing with the actual binder, active material and other slurry components.

How to establish whether a self-dispersing CNT is better

The following is a proposed development comparison, rather than a claim about an existing AIC CNT product:

1. Start with a controlled material comparison. Use the same starting CNT grade where practical. Record processing history, tube-length distribution, functionalisation and purification. Include both the current dispersant-assisted reference and the self-dispersing candidate.
2. Measure usable concentration. Report CNT mass fraction separately from total non-volatile solids, with a method that accounts for grafts and residues. Compare viscosity over relevant shear rates, yield behaviour, ageing and redispersibility at matched CNT concentration before raising it.
3. Inspect the tubes and network. Use microscopy for bundles and tube dimensions, Raman for structural change, and dried-film or electrode conductivity. A single spherical-equivalent D50 value does not fully describe a long nanotube population.
4. Build comparable electrodes. Control active material, CNT loading, binder, areal loading, thickness and porosity. Assess coating quality and electrical performance after the same drying and processing route.
5. Test comparable cells. Match electrolyte, voltage window, temperature, formation and cycling protocol; use replicate cells. Report first-cycle efficiency, capacity retention and impedance, and distinguish half-cell screening from full-cell validation.

The most valuable outcome may be a higher concentration at acceptable viscosity, lower CNT loading for the same electrode conductivity, or more reproducible processing. Any of those could justify development. A battery-life improvement should be claimed only when the cell results establish it.

AIC’s commercial work in self-dispersed aqueous pigment colorants provides a reason to examine surface-controlled dispersion. CNT conductive additives are a separate material-development problem: colourant stability data cannot substitute for battery-grade purity, conductive-network and electrochemical measurements.

Related reading: Inkjet in solar cell and battery manufacturing: Ricoh’s perovskite move.

References and evidence boundaries

Literature checked on 28 October 2026. Reported concentrations belong to the cited preparation methods; the trials proposed above are not measured AIC product results.

1. Yu et al.: Gram-scale preparation of surfactant-free, carboxylic acid groups functionalized, individual single-walled carbon nanotubes in aqueous solution, Langmuir, 26, 1221–1225 (2010); published online in 2009.
2. Wang, Iqbal and Mitra: Rapidly functionalized, water-dispersed carbon nanotubes at high concentration, Journal of the American Chemical Society, 128, 95–99 (2006).
3. Dai et al.: A systematic investigation of dispersion concentration and particle size distribution of multi-wall carbon nanotubes in aqueous solutions of various dispersants, Colloids and Surfaces A, 589, 124369 (2020).
4. Facile formulation and fabrication of the cathode using a self-lithiated carbon for all-solid-state batteries, Scientific Reports (2020).
5. Highly efficient oxidation of single-walled carbon nanotubes in liquid crystalline phase and dispersion for applications in Li-ion batteries, Chemical Engineering Journal, 458, 141350 (2023). Publisher abstract and indexed excerpts; no final aqueous concentration is inferred.
6. Dispersion-assisted carbon nanotubes as a conductive agent for dry-processed cathode for lithium-ion battery, Chemical Engineering Journal, 509, 161183 (2025).
7. Wang et al.: Surfactant-Aided Stabilization of Individual Carbon Nanotubes in Water around the Critical Micelle Concentration, Langmuir, 40, 159–169 (2024); published online in 2023.