Effects of Commonly Evolved Solid-Electrolyte-Interphase (SEI) Reaction Product Gases on the Cycle Life of Li-Ion Full Cells

Abstract

In this work, it is found that cycling full cells in Ar, versus static conditions, significantly reduces their rate of capacity fade, which is attributed to the removal of gaseous reaction products from the cell. The presence of gases evolved in situ can account for a large fraction of the total capacity fade exhibited by the static cells tested. In attempt to understand the role of specific gaseous species commonly evolved during cycling, LiMn 2 O 4 and LiCoO 2 based full cells were further cycled in Ar-H 2 , Ar-CO, Ar-CO 2 , and Ar-CH 4 at reactive gas compositions between 0.5% and 5% and flow rates high enough to rapidly remove any evolved gas. The different electrodes were sensitive to different gases, the effects of gas composition were non-linear, and the effect of mixing gases was not additive. An attempt was made to correlate the degree of capacity fade with the amount of transition metal deposited on the anode, as measured by secondary ion mass spectrometry, but a strong correlation was not found.

Anodic decomposition of surface films on high voltage spinel surfaces—Density function theory and experimental study

“…There is increasing experimental evidence that CEI components on cathode oxides are not static; they continue to evolve and/or become further oxidized as cycling proceeds to high voltages. 15,17,[30][31][32][33][34][35] This finding is not limited to the cathode side; evolution of SEI physical properties and chemical composition on anode surfaces has also been reported. [36][37][38][39] Recent differential and online electrochemical mass spectroscopy (DEMS, OEMS) measurements have proven extremely useful for corre-lating gas release with voltage changes.…”

“…4). CO 2 release should be accompanied by the typical favorable entropy of ∼0.4-0.5 eV at T=300 K at estimated gas pressure of 0.1 atm., 35 which offsets the 0.08 eV endothermicity. In fact, all steps of further EC oxidation we have examined so far with the PBE0 method (Fig.…”

“…This ∆E will not retain CO 2 on the surface because of the ∼0.4 eV entropy gain upon gas release at T=300 K at 0.1 atm. 35 In summary, the more accurate PBE0 method predicts that CO 2 release is not energetically favorable on LMO (001) surfaces at 50% Li-content. Even on LNMO (001) at the same Li-content, which should represent a higher equilibrium potential than 4.3 V, CO 2 release remains energetically and kinetically hindered.…”

Development, retainment, and assessment of the graphite-electrolyte interphase in Li-ion batteries regarding the functionality of SEI-forming additives

“…Generation of gaseous by-products is detected as a source of capacity fade during the evolution processes ( Ma et al., 2018 ). Because a part of the decomposition products is gasses and soluble species, the number of insoluble SEI products can decrease gradually under aging conditions ( Campion et al., 2005 ; Kim et al., 2017 ; Sloop et al., 2003 ; R. Wang et al., 2017 ).…”

A Powerful Protocol Based on Anode-Free Cells Combined with Various Analytical Techniques

“…Decoupling the reactions at the interfaces of both cathode and anode electrodes for rechargeable batteries is one of the essential maneuvers in developing electrochemically stable electrolytes for the performance enhancement of rechargeable batteries. Therefore, it needs to have fundamental understandings of reactions at both cathode and anode interface separately. , However, the cathode||Li protocol is not easy to decouple the reaction at the interface due to the highly reactive nature of Li metal anode. The byproducts generated from cathode||Li cell are mixed, making it technically challenging to distinguish the reactions and products by the concerning electrode from the counter electrode.…”