A Thorough Analysis of Two Different Pre‐Lithiation Techniques for Silicon/Carbon Negative Electrodes in Lithium Ion Batteries

Abstract

AbstractSilicon (Si) is one of the most promising candidates for application as high‐capacity negative electrode (anode) material in lithium ion batteries (LIBs) due to its high specific capacity. However, evoked by huge volume changes upon (de)lithiation, several issues lead to a rather poor electrochemical performance of Si‐based LIB cells. The Coulombic efficiency (CEff) during the first cycle(s), especially when using nano‐sized Si, is relatively low, due to the formation of the solid electrolyte interphase (SEI). Pre‐lithiation approaches can increase the CEff by compensating active lithium losses during the first cycle(s). Here, we evaluate the beneficial impact of pre‐lithiated Si/C electrodes for their application in NCM111||Si/C cells by comparing two approaches, i. e., electrochemical pre‐lithiation and pre‐lithiation by direct contact to Li metal foil. The SEI composition and surface morphology of pre‐lithiated Si/C electrodes as well as the impact of reducing active Li losses on individual electrode potentials over cycling are revealed. For long‐term cycling, both pre‐lithiation techniques lead to a distinct improvement of the overall capacity as well as the CEff for the first 40 cycles due to i) the pre‐formed SEI and ii) a Li reservoir within the anode. Depletion of the active Li from NCM111 is significantly reduced and we can confirm that both pre‐lithiation techniques improve the cycling performance of NCM111||Si/C cells in an almost equal manner.