Carbon nanotubes (CNTs) are allotropes of carbon with a cylindrical nanostructure. There are two main types of CNTs: multi-walled carbon nanotubes (MWCNTs) and single-walled carbon nanotubes (SWCNTs). MWCNTs have multiple layers of graphite sheets rolled up into concentric cylinders. They typically have diameters ranging from 2 to 100 nanometers and lengths up to several centimeters. Some key properties of MWCNTs include:
- Excellent electrical conductivity
- High thermal conductivity
- High tensile strength
- Low density
- High aspect ratio
Due to their unique structure and properties, MWCNTs have potential applications in a wide range of areas:
- Energy storage – MWCNTs can improve electrode materials in lithium-ion batteries and supercapacitors.
- Polymer composites – Adding MWCNTs can enhance mechanical, electrical and thermal properties of plastics and polymers.
- Electronics – MWCNTs have semiconductor properties useful for devices and circuits.
- Sensors – Sensitivity to chemical and mechanical changes enable MWCNT sensor applications.
- Aerospace – High strength and low weight make MWCNTs suitable for lightweight aircraft components.
| Application | Uses and benefits of MWCNTs |
|---|---|
| Batteries | Increased charge capacity, faster charging |
| Polymer composites | Improved strength, conductivity |
| Electronics | Flexible displays, touch sensors |
| Sensors | Gas, chemical, pressure sensing |
The unique properties and broad application potential have driven strong interest and demand for MWCNTs globally. However, challenges remain in cost-effective commercial-scale production of high purity MWCNT materials.
MWCNT market growth and drivers
The global market for multi-walled carbon nanotubes (MWCNTs) has seen strong renewed growth in recent years. This is being driven by rising demand and commercialization in key end-user segments.
- Energy storage – Growing electric vehicle market is boosting demand for MWCNTs as conductive additives in lithium-ion batteries. Major EV makers like Tesla, BYD and LG Chem are adopting silicon-graphite anodes incorporating MWCNTs.
- Electronics – Miniaturization and flexible electronics require MWCNTs for semiconductor and conductive applications in chips, displays, sensors and more.
- Aerospace – Use of MWCNT reinforced composites in airframes and components for strength and weight reduction.
Some key factors spurring increased MWCNT adoption:
- Falling prices and improving purity of MWCNTs enabling viability in cost-sensitive applications.
- Developments in functionalization, manipulation and compatibility enhancing processability of MWCNTs with materials like polymers.
| End User Segment | Estimated MWCNT demand by 2028 |
|---|---|
| Li-ion batteries | 34 kilotons |
| Polymer composites | 31 kilotons |
| Electronics | 12 kilotons |
| Aerospace | 5 kilotons |
Key market and technology trends shaping MWCNT growth:
- Transition to silicon-containing anodes to increase Li-ion battery energy density, enabled by MWCNTs.
- Lightweighting and improved efficiency in aerospace, automotive, wind turbines utilizing MWCNT composite materials.
- Printed, flexible and stretchable sensors and electronics enabled by transparent CNT films and inks.
Major MWCNT manufacturers like LG Chem, Cabot Corporation and JEIO are rapidly expanding production capacities to meet rising demand. The market outlook remains very positive driven by proliferation of MWCNT applications.
MWCNT production trends and capacities
The production process for multi-walled carbon nanotubes (MWCNTs) has seen significant improvements in yield, scale and cost-efficiency over the past decade. This has enabled increased availability of high purity MWCNTs at reduced prices.
MWCNT synthesis methods include:
- Chemical vapor deposition (CVD) – Most common method depositing MWCNTs on substrates using hydrocarbon gas precursors. Allows control of diameter and number of walls.
- Arc discharge – Produces high quality but expensive MWCNTs, useful for niche applications.
- Laser ablation – Allows precise diameter and structure control, but low yields and high costs limit usage.
Advances in CVD synthesis have increased yields while lowering costs. For example:
- Fluidized bed CVD reactors improve precursor gas utilization and enable continuous mass production.
- Using aluminum oxide templates in CVD can control nanotube dimensions.
- Adding molybdenum or tungsten can reduce impurities.
Purification processes like microfiltration, oxidation, and acid reflux remove impurities like amorphous carbon, catalyst particles and more. This improves product consistency and expands applications.
Global MWCNT production capacity has rapidly increased from around 3,000 metric tons in 2011 to over 25,000 tons in 2021. Further capacity expansions are underway:
- LG Chem – Expanding from 4,000 to 6,100 tons/year by 2024.
- Cabot – Adding 15,000 tons/year capacity by 2025.
- JEIO – Increasing from 120 to 6,000 tons/year.
| Company | 2021 MWCNT Capacity | Planned Expansion |
|---|---|---|
| LG Chem | 4,000 tons/year | +2,100 tons by 2024 |
| Cabot | 10,000 tons/year | +15,000 tons by 2025 |
| JEIO | 1,000 tons/year | +5,000 tons by 2023 |
Rising production has enabled improved commercial availability and cost reductions. Further improvements in synthesis methods, purification, and scale will drive down MWCNT prices, supporting adoption across industries.
MWCNT applications in batteries and energy storage
One of the most promising and rapidly growing application areas for multi-walled carbon nanotubes (MWCNTs) is in lithium-ion batteries (Li-ion) and other energy storage technologies.
Adding MWCNTs to Li-ion battery electrodes as conductive additives provides several benefits:
- Increased charge capacity and energy density.
- Faster charging and discharging capability.
- Improved lifespan and stability over charge/discharge cycles.
- Allows use of higher capacity silicon-based anodes.
MWCNT benefits for Li-ion batteries:
- High conductivity enables efficient electron transfer in electrodes.
- Large surface area increases active sites for electrochemical reactions.
- Nanotube networks provide mechanical support and bind active materials.
- Enables stable battery performance with high-capacity silicon anodes.
Global Li-ion battery demand is forecast to grow from ~500 GWh currently to over 2000 GWh by 2030, driven by electric vehicles and energy storage. This is spurring huge demand for MWCNT conductive additives:
- LG Chem targets over 34,000 tons/year MWCNTs for Li-ion batteries by 2028.
- Use of MWCNTs allows transition to silicon-containing anodes for higher energy density batteries.
- MWCNT loadings of 1-2% in electrodes amplifies demand.
| Battery Application | MWCNT Demand Factor |
|---|---|
| Electric Vehicles | High energy density needs |
| Grid Storage | Cost and performance |
| Consumer Electronics | Stable longevity |
MWCNTs also show promise as electrode materials for advanced battery concepts like lithium-air and lithium-sulfur, as well as in supercapacitor energy storage.
The battery industry represents the largest current demand driver for MWCNTs. Further advances in nanotube synthesis, functionalization and battery integration will expand adoption.
