Electrolytes that reduce electro-osmotic drag improve fast charging of lithium-ion batteries
Zhao Chang-xin, Zeyi Wang, David L. Jacobson, Yue Li, Boris Khaykovich, Sean Fayfar, Lei Zheng, Jacob M. LaManna, Xilin Chen, Daniel S. Hussey, Fu Chen, Gabriel M. Veith, Chunsheng Wang
Abstract
Fast charging (at rates greater than 4 C) is essential for high-energy lithium-ion batteries in electric vehicles yet remains challenging owing to a lack of understanding of fast-charging barriers. Conventional optimization strategies concentrate on shortening lithium-ion transport pathways through electrode structure modification, which often compromises energy densities. In this work, we demonstrate that thick-electrode fast charging is constrained by solvent withdrawal within porous electrodes and the resulting electro-osmotic drag polarization, which is driven by cation-induced electro-osmotic drag. To reduce electro-osmotic drag polarization, we designed electrolytes with weak cation solvation and strong anion solvation, where a difluorinated solvent weakens lithium-cation solvation and its difluoromethyl hydrogen atoms enhance anion solvation through hydrogen bonding. This electrolyte enables thick-electrode, energy-dense batteries to achieve 80% charge within 13 minutes.