Thanks to their unique intrinsic properties, graphene nanotubes outperform alternatives and offer substantial Li-ion battery performance improvements in terms of energy density, safety, discharge power, and adhesion.
Such performance improvements for Li-ion battery cathodes cannot be demonstrated by any traditional conductive materials, such as carbon black or multi wall carbon nanotubes.
TUBALL™ graphene nanotubes (also known as single wall carbon nanotubes) have a set of unique properties, such as a high length-to-diameter ratio, flexibility, and the ability to create well-developed conductive reinforcing networks inside active materials. It allows TUBALL™ nanotubes to boost Li-ion batteries’ performance even at ultralow working dosages.
As it can be clearly seen in the SEM image, even 0.08% TUBALL™ graphene nanotubes in NCM 811 active material perfectly covers the active material surface and connects the particles together.
Being the most conductive material that can be used in the formulation of Li-ion batteries, even a small amount of TUBALL™ graphene nanotubes is enough to reduce internal battery cell resistance (DCR). Stable TUBALL™ networks are maintained inside the cathode material even after multiple battery charge-discharge cycles and battery storage periods, enabling DCR to be maintained at a low level as well—after high temperature (HT) storage and cycling.
The lower battery DCR results in lower temperature build up, and thus a reduced risk of a battery fire. This is a crucial safety benefit made possible by TUBALL™ graphene nanotubes.
Less than 0.1% TUBALL™ provides higher energy density. This concentration is 10–60 times lower than required when using multi wall carbon nanotubes or carbon black as a conductive material. In a modern EV battery pack, 5 kg of conductive carbon black can be replaced by just 100 g of TUBALL™.
Thanks to the unmatched conductivity of graphene nanotubes compared with other conductive additives, using TUBALL™ in cathodes makes it possible to achieve fast discharging while also increasing the battery’s capacity.
Nanotube networks hold the cathode material particles together, increasing the bond strength between them.
To facilitate the application of graphene nanotubes in LCO, LFP and NCM-based and other types of cathodes, OCSiAl has developed TUBALL™ BATT—a ready-to-use product containing well-dispersed nanotubes in different liquid carriers that can be simply mixed in during standard manufacturing process.
The unmatched conductivity of TUBALL™ enables improved battery safety and energy density. TUBALL™ BATT is now available in an optimized, more cost-efficient dispersion form.
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High thickness and specific capacity leads to areal capacities of up to 45 and 30 mAh cm−2 for anodes and cathodes, respectively. Combining optimized composite anodes and cathodes yields full cells with state-of-the-art areal capacities (29 mAh cm−2) and specific/volumetric energies (480 Wh kg−1 and 1,600 Wh l−1).
Replacing Denka black with SWCNT allows to reduce the carbon content to 0.2 wt% to further increase the energy density, and 2 wt% of PVDF was shown to benefit the cycling stability due to the mitigated PVDF-induced side reactions from its direct contact with NCA particles.
100 μm thick electrodes with mass loadings 2 of ∼15 mg/cm2 were produced. While carbon black or graphene loadings of >10 wt % are required to reach OOP conductivities of 1 S/ m, this level can be achieved with ∼1 wt % of carbon nanotubes.
With minimum inactive components (i.e., binder and conductive agents), the proposed electrode structure delivers good cycling stability and rate capability under high areal loading (as high as 200 mg cm−2).