Fast charge is limited by the reduction (lithiation) potential and nature of the anode. If charged too fast, graphite anodes may be plated with lithium metal because their lithiation potential is too close to the plating potential of lithium. Faster charge can be accomplished with anodes which lithiate at higher potentials (such as NTO). The trade-off is lower cell energy since there will be a smaller voltage difference between anode and cathode. However, there are anode materials which may bypass this energy – fast charge compromise. Listen to my podcast to learn more.
Anodes with silicon active materials may offer more than 2x the capacity of anodes with graphite active materials and improved rates of operation due to a low risk of lithium plating. A 1D architecture consists of ultrathin wires or whiskers as opposed to ultrathin sheets (2D). Emerging from the lab of professor Gleb Yushin, Sila Nanotechnologies focuses on such electron conductive wires (carbon based) decorated with silicon nanoparticles. This concept provides a highly porous secondary structure where the silicon particles have room to expand and contract without cracking the overall anode structure and is claimed to work well with liquid electrolyte systems. This podcast dissects a 2018 patent which claims Sila’s core silicon anode technology.
There is a lot of talk on the subject of fast charging in the electric vehicle world. In principle, you cannot have both high energy density AND fast charging built into the same battery. There are many reasons for this, however, the graphite anode is the main block to fast charging. Currently “power” cells with graphite anodes can charge as fast as 75% in 15 minutes while “energy” cells require >1.5 hours. Future anodes such as silicon may bring larger capacities AS WELL AS faster rates of charging. Enevate discloses how in this patent. Listen to my podcast to learn more.