The grain sizes of solid electrolyte interphase (SEI) and solvation structure of electrolytes can affect Li⁺ ion transport across SEI and control the desolvation kinetics of solvated Li⁺ ions during fast-charging of Li-ion batteries (LIBs). However, the impact of the geometric structure of SEI grains on the fast charging capability of LIBs is rarely examined. Here, the correlation between the SEI grain size and fast charging characteristics of cells is explored, and the desolvation kinetics is controlled by replacing the strongly binding ethylene carbonate (EC) solvent with a weakly binding nitrile-based solvent under fast charging conditions. The evolution of small grains of SEI to provide sufficient paths for Li⁺ ion supply can be achieved by the modification of solvation structure in the electrolyte. Additionally, the less resistive SEI composition and low viscosity of isoBN-containing electrolyte enable a more rapid charging of LiNi_0.8Co_0.1Mn_0.1O₂/graphite full cells by facilitating the SEI crossing of Li⁺ ions with less Li plating at a charging rate of 4 C at 25 °C. This work sheds light on solvation structure and interface engineering to enhance the fast charging cycle stability of LIBs for tailorable adoption in transportation sectors.