Modification of the Solid Electrolyte Interphase on SiGr Electrodes by a Prelithiation Method Using Passivated Lithium Metal Powder

Negative electrode materials with high specific energy, such as SiGr, are essential to decrease battery cell weight and volume while allowing improved range and design flexibilities for electric vehicles. Among different SiGr anode prelithiation methods, the use of passivated lithium metal powder is discussed in terms of cell impedance and its effects on the interphase film formation on SiGr and LiNi0.8Mn0.1Co0.1O2 (NMC-811) electrodes with high mass loadings. Electrochemical impedance spectroscopy analyses show that a less resistive and more effective solid electrolyte interphase (SEI) forms upon prelithiation which also benefits the charge transfer at the SiGr electrode. Scanning electron microscopy images show a thicker interphase layer with less interstitial porosity on the prelithiated SiGr electrodes and a thinner cathode electrolyte interphase on NMC-811 electrode as a result of the lower average cathode potential attained throughout cycling, in comparison with the cells without prelithiation. A more diverse SEI layer, richer in beneficial components such as LiF, is promoted by the prelithiation method as shown by X-ray photoelectron spectroscopy with a sputtering depth of 100 nm. Finally, it is shown that the more robust SEI layer forming upon prelithiation requires less electrolyte consumption for repairing the SEI layer throughout long-term cycling.