Forward and reverse differential-pulse effects applied in the formation of a solid electrolyte interface to enhance the performance of lithium batteries

Abstract

In Li-ion batteries, the solid electrolyte interface (SEI) plays a crucial role in transferring Li ions into active materials through an electrochemical driving force. SEI is a composite layer containing of inorganic and organic components, which are fabricated by the salt degradation products and partial or complete reduction products of the solvent of the electrolyte at the battery's initial charge-discharge cycle. The chemical properties of SEI and the electrochemical driving force must be mutually optimized so as to strengthen its integrity, while minimizing irreversible SEI formation; thereby suppressing the decomposition at high temperatures. In this study, we investigated a new method of creating the SEI, i.e. the forward and reverse differential-pulse (FRDP) method, which balances the reaction kinetics of SEI formation. Furthermore, the use of the FRDP method also creates a SEI with a modified kinetic reaction route that affects battery performance. Here, we present data from the first charge-discharge and cycle performance at a high rate and a high temperature, obtained using scanning electron microscopy, electrochemical impedance spectroscopy, X-ray photoelectron spectroscopy, and Li+-diffusion kinetics analysis. Our findings indicate that the use of the FRDP method for generating the SEI results in a 58% reduction in the SEI's ionic diffusion activation energy and a 4.5% increase in battery capacity at room temperature, while increasing battery performance at 60°C stability compared to batteries in which the SEI is formed using the constant-current method.