Effect of Solvents in Electrospray of Ni-Rich Layered Materials for High-Performance Cathodes in Lithium-Ion Batteries

Electrospray, introduced to the coating process, enables the fabrication of porous electrodes, and electrosprayed cathodes exhibit improved cycle performance. Further, the solvent used in the cathode slurry of the electrospray coating plays a crucial role. This study investigated the effects of various solvents on the electrospray of Ni-rich layered materials for electrode fabrication as an alternative to conventional slurry coating using the doctor-blade method. The electrode performance of a typical doctor blade method using the N-methyl-2-pyrrolidone (NMP) solvent, which has various disadvantages (boiling and autoignition temperature), was compared with that of electrosprayed cathodes using NMP; N,N-dimethylformamide (DMF); and DMF/acetone solvents. The volatility difference between the three solvents resulted in the creation of individual cathodes with different porosities. For the DMF/acetone solvent, which had the highest volatility, the coated cathode showed 75.97% capacity retention after 100 cycles at 1C, which was significantly higher than those of the NMP (62.91%) and DMF (66.25%) solvents. Electrochemical impedance spectroscopy (EIS) showed a stable peak retention during cycling and a low increase in individual resistance for the DMF/acetone solvent cathode. To conclude, optimizing solvent selection in electrosprayed cathodes is highly critical for enhancing the cathode cycling performance, contributing to high-performance lithium-ion batteries.