Mechanical studies of the solid electrolyte interphase on anodes in lithium and lithium ion batteries

Abstract

A stable solid electrolyte interphase (SEI) layer is key to high performing lithium ion and lithium metal batteries for metrics such as calendar and cycle life. The SEI must be mechanically robust to withstand large volumetric changes in anode materials such as lithium and silicon, so understanding the mechanical properties and behavior of the SEI is essential for the rational design of artificial SEI and anode form factors. The mechanical properties and mechanical failure of the SEI are challenging to study, because the SEI is thin at only ~10–200 nm thick and is air sensitive. Furthermore, the SEI changes as a function of electrode material, electrolyte and additives, temperature, potential, and formation protocols. A variety of in situ and ex situ techniques have been used to study the mechanics of the SEI on a variety of lithium ion battery anode candidates; however, there has not been a succinct review of the findings thus far. Because of the difficulty of isolating the true SEI and its mechanical properties, there have been a limited number of studies that can fully de-convolute the SEI from the anode it forms on. A review of past research will be helpful for culminating current knowledge and helping to inspire new innovations to better quantify and understand the mechanical behavior of the SEI. This review will summarize the different experimental and theoretical techniques used to study the mechanics of SEI on common lithium battery anodes and their strengths and weaknesses.

Microbial pyrazine diamine is a novel electrolyte additive that shields high-voltage LiNi1/3Co1/3Mn1/3O2 cathodes

“…Typically, CEI comprises of inner layer with rigid decomposed inorganic components and soft mesoporous outer layer with decomposed organic components of the electrolyte 41 . Upon electrolyte decomposition at a higher potential, the CEI is usually enriched with organic soft layer with ROCO, ROR, RCO 3 , and P x O y F z species that promote ionic conductivity 42 .…”

“…Upon electrolyte decomposition at a higher potential, the CEI is usually enriched with organic soft layer with ROCO, ROR, RCO 3 , and P x O y F z species that promote ionic conductivity 42 . However, at lower potential, the electrolyte decomposition leads to the formation of a CEI that is rich with inorganic species like Li 2 CO 3 , LiF, and Li x PF y whose excess formation would obstruct an effective ion transport 41 . As suggested by the theoretical studies of DMBAP and proven by oxidative scan during LSV measurements, the presence of DMBAP in the electrolyte must drive the formation of CEI that is rich with organic species because the sacrificial response of DMBAP would increase the potential window of electrolyte decomposition.…”

From lithium to emerging mono- and multivalent-cation-based rechargeable batteries: non-aqueous organic electrolyte and interphase perspectives

“…Among the expected phases, the magnitudes of the moduli follow the order of PEO o LiEC o LiMC o Li 2 EDC o Li 2 CO 3 o LiF, with polymeric o organic o amorphous inorganic components o inorganic crystalline components. 325 However, it is noteworthy to mention that an EEI presenting a large elastic strain limit (e Y ) may favor highly reversible batteries despite its low E. Thus, it is of vital interest to find a trade-off between these two parameters to regulate the mechanical property of the SEI or EEI in general. The maximum elastic deformation energy (U) is proposed to bridge both parameters (U p (E Â e Y ), eqn (15)), thus robustly predicting the stability of the EEI.…”

Review of low‐temperature lithium‐ion battery progress: New battery system design imperative

“…The main cause of ageing during typical temperature cycling has been postulated to be Li depletion because of the continuous formation of SEI on the electrode 20 . The SEI is made up of electrolyte solvent decomposition and salts that form a protective layer around the electrode, which is a complex passivating layer that forms on the electrode 21 and allows Li + transport and block electrons, 22 preventing further electrolyte reduction by preventing direct contact between electrode and electrolyte 23 . The major degradation mechanism in LIBs is SEI development at the anode/electrolyte contact.…”