Si-anodes with graphene nanotubes: energy density 350 Wh/kg and 1,500 Wh/l, capacity 600 mAh/g, service life 1,500 cycles

Silicon is the key to energy density. Why?

Material with the highest energy density

In order for an EV to have longer range, its battery needs be able to store enough energy and at the same time not weigh too much or take up too much space – high energy density is required.

The cherished goal in the industry is to go beyond 300 Wh/kg and 800 Wh/l, but the best battery cells currently on the market only manage 260 Wh/kg and 700 Wh/l (21700 type). Substantial improvement is required.

In order to reach these energy density goals and go beyond them, it is necessary to use anode and cathode active materials with the highest energy densities.

For cathodes, these are high-nickel-content materials such as NCA, NCM 811, NCM 622, etc. For anodes, silicon is the best, if not the only, option today (and silicon-based materials, such as SiO and SiOx).

Silicon can store more than 10 times the amount of energy than graphite, which was traditionally used as an anode material: 4200 mAh/g vs 370 mAh/g. So, switching from graphite anodes to silicon anodes can boost battery energy density dramatically!

Every Li-ion battery manufacturer would already have been using silicon instead of graphite in their battery cell design but for a fundamental and unresolved problem with silicon.

The fundamental problem with silicon

During a battery’s charging and discharging, silicon substantially expands in volume (up to 300%), which leads to its cracking. Cracks in silicon then cause a loss of contact between silicon anode material particles. As a result, a battery with silicon goes out of service very rapidly.

This problem makes it impossible to use silicon, the best material in terms of energy density, in the recipes of the modern Li-ion batteries.  

TUBALL™ graphene nanotubes – the key to silicon

TUBALL™ graphene nanotubes (also known as single wall carbon nanotubes) solve the key and fundamental problem of silicon-based anodes. Thanks to their unmatched conductivity, high strength, flexibility, record length-to-diameter ratio and ability to form well-developed networks inside the materials at low dosages, TUBALL™ graphene nanotubes, when introduced into silicon-based anodes, cover the surface of the silicon particles and create highly conductive and durable connections between them.

These connections are so dense, long, conductive and strong that, even when the silicon particles in the anode expand and the material starts to crack, the particles stay well connected to each other through the TUBALL™ graphene nanotubes. This prevents the anode from going out of service – the hugely improved cycle life is enough to meet even the most strict EV manufacturers’ requirements.

Working principle

Thanks to their high conductivity, flexibility and a record length-to-diameter ratio, only a tiny quantity of graphene nanotubes is needed to cover the surface of the electrode and facilitate its unmatched conductivity.

How do nanotubes work inside an electrode?

As of today, TUBALL™ is the only efficient solution that can solve the key problem of silicon anodes.

TUBALL™ networks solve the key problem of silicon-based anodes and substantially increase their cycle life up to 4x. TUBALL batteries with high silicon content can meet strict EV/Electronics industry requirements on cycle life. 

Today, silicon anodes = TUBALL™-based anodes

The usage of TUBALL in high-energy silicon anodes becomes the industry standard

Leading Li-ion manufacturers have proven that TUBALL™ nanotubes make it possible today to create anodes with 20% SiO inside and that have 600 mAh/g of capacity and 1500 cycles of service life. 

When utilizing such high-silicon-content anodes in battery designs, record-breaking battery energy densities can now be achieved: 300 Wh/kg and 800 Wh/l.


Results obtained by the OCSiAl R&D team have proven that it’s possible to increase the SiO content in anodes to 90%, which will result in energy densities of 350 Wh/kg and 1350 Wh/l.

E-nable energy

TUBALL™ BATT – a ready-to-use product for application in silicon-based anodes.

TUBALL™ BATT H2O is the first ready-to-use TUBALL™ nanotube-based solution that efficiently solves the key problem of Si/C anodes. TUBALL™ graphene nanotubes enable unmatched conductivity for Si/C anodes starting from just 0.05%. When added to Si/C anodes, the ultra-fine and stable graphene nanotubes in TUBALL™ BATT H2O fully cover and electrically connect the Si/C anode particles during the charge–discharge process of Li-ion batteries, even during the harshest cycling conditions required by EV manufacturers.

For more details on TUBALL™ BATT, click the product card below or contact us.

Related products

Water dispersion of single wall carbon nanotubes with the addition of dispersing agent. Used as a conductive additive for lithium-ion batteries


Energy Storage



Carrier Media

Water, PVP, CMC, PAA, other


Related videos

How do nanotubes work inside an electrode?

Batteries e-nabled by SWCNTs: present and future (Andrey Senyut, OCSiAl Energy)

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