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

Abstract

Silicon (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.