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.
Belharouk et al, 2018, Electrochemical Communications – charging limits of NCM811 cathodes and graphite anodes
Bhagat et al, 2018, Electrochimica Acta – charging limits of commercial energy cell
Miller et al, 2017, SAE – charging limits of commercial power cell
In this podcast I discuss the charging rate limits for commercial electrode materials as well as commercial cells. They are faster than you may think.
Currently commercial lithium ion batteries typically charge in 1.5 – 2 hours. ‘Fast charge’ is limited to 30 – 45 minutes and with harsh consequences on cycle life and safety. However, there are battery electrode materials which blur the capacitor/battery line. MoS2 has been claimed by professor Dunn (UCLA) to be such a “pseudocapacitor”. This podcast discusses a patent claiming a pseudocapacitor electrode material which can charge in 2.5 minutes for > 10,000x and with a capacity > 120mAh/g.
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.