How do you contribute to the development of anode and cathode materials, particularly regarding the use of carbon nanotubes (CNTs)?
Battery electrodes, both cathode and anode, need to be electrically conductive. The addition of Nanocyl carbon nanotube (CNT) as an advanced conductive additive to electrode formulation not only increases its conductivity but also improves its mechanical strength by making a 3D network that stitches electrode particles to each other. Given the low conductivity of silicon-based anodes and challenges related to their volume change during cycles, such properties of carbon nanotubes become even more important when working with silicon-containing anodes. Thanks to the higher conductivity of carbon nanotubes than conventional additives, a much smaller quantity of Nanocyl CNT will be required in electrode formulation to achieve the required conductivity. This opens up the space for the active material in the electrode formulation resulting in an increased energy density. Also, the elevated conductivity by the CNT increases the rate capability of the cell resulting in increased power output. Our CNT is added to both the anode and the cathode formulations to bring superior properties in terms of energy and power output of the cell. Together with our project partners, we also work on developing electrode designs that bring higher compatibility to the gelled system, both in terms of material loading and processing.
How the performance of the CNTs and their dispersions is evaluated? How does NANOCYL optimise the performance of CNTs in the electrodes developed for the NEXTCELL project?
Battery electrode has many different requirements, defining the physical and (electro)chemical properties of its composing materials. Characterizing the carbon nanotubes enables us to evaluate different properties such as purity, density, morphology and active surface area. Regarding the role of CNT as the conductive additive, the film resistance of the electrodes containing different CNTs is also compared to analyse the impacts of CNT type on the resistivity of the electrodes in question. The next level of screening is electrochemical assessment. For instance, together with POLITO as one of the project partners, we studied the electrochemical stability of 3 CNT grades via cyclic voltammetry where the results showed the stability of all grades with no traces of negative interventions to cell chemistry. The electrochemical tests will be completed with cell performance results where the CNT content in electrode formulation could be further optimized. The results of tests on coulombic efficiency, internal resistance and rate capability will provide us with the required indications at the cell level. Since the NEXTCELL project develops a new cell concept based on gelled electrodes using a semi-dry process, the processability of the CNTs is another factor to optimize. We are working on dispersing CNTs in different systems to integrate them better to the electrode processing method. From that aspect, the rheological properties of the dispersions and their particle size distribution are the other parameters that we constantly monitor to increase cell performance by improving the distribution of CNT within the electrode matrix.
What innovative approaches is NANOCYL exploring to enhance the performance and durability of the batteries developed in this project?
In terms of performance, energy, and power advantages the CNT-formulated electrodes are targeted to enhance cell characteristics. Given the expected mechanical improvements in electrode structure, the role of CNT in increasing the cycle life will be followed as well. Nanocyl brings different CNT types with different morphologies to this project. This offers various possibilities in terms of electrode component compatibility. Additionally, we are working on developing the most efficient approach to introducing CNT to the semi-dry electrode process. This includes developing CNT-formulated dispersions for better integration of CNT to the gelled cell. We also work with our partners to develop new processing methods for applying CNT powder in electrode preparation.
