Periodic Reporting for period 1 - HIDDEN (HINDERING DENDRITE GROWTH IN LITHIUM METAL BATTERIES)
Reporting period: 2020-09-01 to 2022-02-28
The project brings together a strong interdisciplinary consortium of seven partners, industry and research balanced, with state-of-the-art background in battery chemistry and physics, materials modelling and analysis, upscaling of novel technologies by printing and coating, as well as in industrial assembling of battery cells. This is complemented by external advisory board with representation of key industry end-users.
One of the topics where we have recently focused on is processing of the novel self-healing batteries. The liquid crystalline electrolyte and the piezoelectric separator require special processing methods, as the standard Li-ion manufacturing processes are not optimal as such for the HIDDEN materials. Our goal is to be able to manufacture self-healing batteries in a way, which is scalable and safe, and which does not require too complicated processing steps. This would enable adoption of the self-healing functionalities in commercial cells in future, even though the project, as well as the whole Battery 2030+ initiative, operates at low TRL. The results look promising so far, as we have been able to coat our model liquid crystalline electrolyte on top of the NMC electrode and infiltrate it into the cathode as well. We are now proceeding from coin cell test to pouch cells, which requires also good practices for cutting of the electrodes. Laser cutting of the combined NMC and solid electrolyte layer, as well as the Li metal anode, seems to be working for these materials. Regarding the piezoelectric separator, we have found ways to control the porosity of the layer and upscaling of the coating process is planned.
The piezoelectric effect is the ability of certain materials to accumulate electric charge in response to a mechanical stress. HIDDEN will use this phenomenon in a separator. When growing dendrites will eventually reach the separator, it will bend, and generate a local electric field. This will guide the Li+ cations to deposit smoothly between the growing dendrites, and not on top of them, increasing the cell cycle life. HIDDEN has tried two methods for enabling piezoelectric separator – casting a porous self-standing poly(vinylidene fluoride) (PVDF) separator, and coating the porous PVDF layer on a commercial polypropylene (PP) separator. Both were successful, but the later cannot be efficiently poled with an external field. So, the porous PVDF separator is taken forward for battery cycling.
Several cell characterization techniques were screened out and some selected to be suitable for detecting dendrite growth. The validation results show that specific parameters allow detecting degradation in the tested Li-metal batteries. The results have been shared in a public report, found from the project website. The tested detection techniques can be implemented in embedded systems to sense degradation, activate self-healing methods, and assess the overall benefits. Some techniques are easier than others, but in general all the non-invasive techniques proposed can be implemented in battery management systems (BMSs), except (till date) for coulombic efficiency. The consortium sees also potential in the use of sensors developed by Spartacus, Sensibat or Instabat, which could be ultimately integrated with the BMS.
The HIDDEN project will increase the quality, reliability and lifetime of Li-metal batteries, paving the way for electrification of transportation. In addition, we expect to generate industrial opportunities for the next generation battery industry in Europe.