Development of high-performance silicon anode

Lithium ion batteries have attracted much attention since Sony developed the first commercial product in 1990s. Recently, Lithium ion batteries have been used in the field of electric vehicle and energy grid. However, the high cost has become the bottleneck of its further application. There are two ways to low the cost of batteries, namely reducing the bill of the materials (BOM) and lowing the manufacturing cost. Currently, the commercial batteries are produced by slurry casting method (wet method), where active materials, binder and conductive additives are mixed with solvent to make the slurry and then the slurry is casted on to the current collector and then dried through dozens meters length high temperature oven to dry the electrode. In this process, much energy is consumed, which increase the manufacturing cost of the batteries. Another drawback for wet method is the difficulty to fabricate thick electrode(>100um), which can't achieve high energy density. This project has developed new processing of dry method for electrode fabrication. In this process, there was no solvent involved and much energy was saved because it's no need to vaporize the solvent and reduce the manufacturing cost. Another advantage for this process is that electrode with high thickness (>200um) was fabricated successfully, which reduced the bill of materials and increased the energy density simultaneously.

This project has developed new process for solvent free electrode fabrication. For Beyonder, this will be an important step to providing next-generation energy storage devices to renewable and transport industries, while for the University of Stavanger it will provide important knowledge of energy storage in order to build their competence in this field. The impacts of this work will be the availability of high-capacity, high-rate anodes capable of providing power and load-levelling to several industries, including shipping and wind. This will lower the costs, both economic and environmental of these industries; and in the case of renewables increase reliability. Further, the technology will be integrated into cells produced at Beyonder's pilot plant and factory, which is to be built in Rogaland, Norway. This factory will help to provide jobs and growth to the region.

This project aims to develop a high-performance silicon anode to displace commercial graphite anode, thus enhancing the cell performance. There are two critical R&D challenges in this project. The first one is how to enhance the cyclic stability of silicon anode from less than 1000 cycles to 2000 cycles. Silicon electrode suffers fast capacity fading due to its large volume expansion and shrinking during charge and discharge. This causes the electrode pulverization and continuous electrolyte consumption thus a fast capacity fading. The proposed solutions here are to select carbon coated silicon nanoparticles, a flexible polymer binder, and the electrode microstructure optimization. Another challenge is how to shorten the charge and discharge time to 20 min. Nowadays, the charge and discharge time of commercial cells are in the range of one to a few hours. The proposed solution here is to use a combination of zero- and two-dimension conductive additives to enhance the electrode conductivity and optimize the porosity of the electrode to enhance the electrolyte wettability. The developed silicon electrode will be employed as anode for Beyonder Li-ion capacitor development and manufacturing. The high-performance silicon electrode is critical for the Beyonder's product development. Additionally, the high-performance silicon electrodes can be also used for next-generation fast charging and high energy density Li-ion batteries.