Review—SEI: Past, Present and Future

Abstract

The Solid-Electrolyte-Interphase (SEI) model for non-aqueous alkali-metal batteries constitutes a paradigm change in the understanding of lithium batteries and has thus enabled the development of safer, durable, higher-power and lower-cost lithium batteries for portable and EV applications. Prior to the publication of the SEI model (1979), researchers used the Butler-Volmer equation, in which a direct electron transfer from the electrode to lithium cations in the solution is assumed. The SEI model proved that this is a mistaken concept and that, in practice, the transfer of electrons from the electrode to the solution in a lithium battery, must be prevented, since it will result in fast self-discharge of the active materials and poor battery performance. This model provides [E. Peled, in "Lithium Batteries," J.P. Gabano (ed), Academic Press, (1983), E. Peled, J. Electrochem. Soc., 126, 2047Soc., 126, (1979.] new equations for: electrode kinetics (i o and b), anode corrosion, SEI resistivity and growth rate and irreversible capacity loss of lithium-ion batteries. This model became a cornerstone in the science and technology of lithium batteries. This paper reviews the past, present and the future of SEI batteries. The PastPrior to the publication of the SEI model (1979), 1,4 researchers used the Butler-Volmer equation, in which direct electron transfer from the electrode to lithium cations in the solution is assumed. It was generally assumed that the rate-determining step (RDS) is the transfer of electrons from the metal to the cations in the solution. Researchers found that the lithium anode is covered by a passivating layer which interferes with the deposition/dissolution process of the anode. Brummer and Newman 2,3 concluded that a passivating anode can offer only a limited cycle life and in order to obtain a deep-discharge high-cycle-life secondary battery, the lithium anode must be free of a passivating layer and kinetically stable with respect to the electrolyte. The SEI model proved that this is a mistaken concept and that, in practice, the transfer of electrons from the electrode to the solution in a lithium battery, except when forming a SEI, must be prevented. The Present, Lithium-Metal and Lithium-Ion BatteriesIntroduction.-It is now generally accepted that the solidelectrolyte interphase (SEI) is essentially for the existence and successful operation of lithium-and sodium-battery systems, as primary and secondary power sources. 4 In 1979, it was proposed by Peled,

Operando Observations of SEI Film Evolution by Mass‐Sensitive Scanning Transmission Electron Microscopy

“…[17] At the initial stage of the lithiation, a SEI layer with inhomogeneous thickness has already formed on the surface of gold anode (Figure 2a), most likely resulting from a quick spontaneous reaction between the gold electrode and the electrolyte since the initial voltage of the liquid cell is −2.18 V versus Au (pseudo) below the reduction potential of the electrolyte (−0.75 V versus Au (pseudo)). [3,[19][20][21] Moreover, the distribution of the Li-Au nanoparticles trapped in the SEI film is also inhomogeneous Adv. The formation of Li-Au alloy can be recognized from the obvious contrast change and local volume expansion in the region at the interface between the gold electrode and SEI layer, which is marked by the black arrow in Figure 2b.…”

“…The contrast of the double-layer SEI film is consistent with previous assumption that the inner layer is comprised of compact inorganic products (e.g., Li 2 CO 3 , LiF, Li 2 O, etc.) [1,3,16,22] The obvious contrast variation of the inner layer indicates inhomogeneous density distribution of the inorganic products. [1,3,16,22] The obvious contrast variation of the inner layer indicates inhomogeneous density distribution of the inorganic products.…”

“…[1][2][3][4] The products by side reactions at the interface between electrode and SEI films. [1][2][3][4] The products by side reactions at the interface between electrode and SEI films.…”

Review—Li Metal Anode in Working Lithium-Sulfur Batteries

“…Some conclusions on the SEI component and structure have been recognized as follows. 60,61 (1) The customarily accepted description pattern on the SEI structure is the mosaic model, meaning that the SEI film is not homogeneous (Figure 5a). 62 Several reductive decompositions proceed on the negatively charged anode surface simultaneously, and a mixture of insoluble multiphase products deposits on the anode.…”

Temperature-Dependence of the Solid-Electrolyte Interphase Overpotential: Part I. Two Parallel Mechanisms, One Phase Transition

“…7 The Young equation seems to be the most prominent and is cited throughout literature from its development in 1961 14 to its proposition for the SEI in 1979 16 and through SEI research and reviews up to today. 6,17 The equation by Young has the form i = prefactor · sinh(zF/RT · a/d · η) 14 with a being the half-jump distance and d the thickness of the film which is intended to describe the hopping of ions through Frenkel and Schottky defects. 14 One can simply challenge the validity of this equation by its limits.…”