Charge‐Transfer Kinetics of The Solid‐Electrolyte Interphase on Li₄Ti₅O₁₂Thin‐Film Electrodes

Abstract

Charge‐transfer kinetics between electrodes and electrolytes critically determines the performance of lithium‐ion batteries (LIBs). Lithium titanate defect spinel (Li4Ti5O12, LTO) is a safe and durable anode material, but its relatively low energy density limits the range of applications. Utilizing the low potential region of LTO is a straightforward strategy for increasing energy density. However, the electrochemical characteristics of LTO at low potentials and the properties of the solid‐electrolyte interphase (SEI) on LTO are not well understood. Here, we investigate the charge‐transfer kinetics of the SEI formed between model LTO thin‐film electrodes and organic electrolytes with distinct solvation ability using AC impedance spectroscopy whereas their stability was assessed by cyclic voltammetry of ferrocene. With the SEI film on LTO, the Li+ desolvation was rate‐determining step but with larger activation energies, which showed a strong dependence on the solvation ability of electrolyte. The activation energies of desolvation for the fluoroethylene carbonate+dimethyl carbonate‐ and ethylene carbonate+diethyl carbonate‐based systems increased from 35 and 55 to 44 and 67 kJ mol−1, respectively, and that for the propylene carbonate‐based system did not noticeably change at around 67 kJ mol−1. In addition, the SEI passivation of LTO was much slower than that of graphite, and the rate also strongly depended on the solvation ability of the electrolyte. Understanding the surface properties of LTO at low potentials opens the door for high‐energy‐density LTO‐based LIBs.

Black Phosphorus-Graphite Material Composites with a Low Activation Energy of Interfacial Conductivity

“…> EC+DEC (1:1) (52-56 kJ mol −1 ) > FEC+DMC (3:7) (33-36 kJ mol −1 ), which is in good agreement with the solvation capacity of the solvent molecules. 20 However, our BP-CSCNT show the same activation energies in all three solvents, suggesting that they are less related to the desolvation process.…”

Clarification on the Gassing Behavior of Carbon‐Coated Li4Ti5O12 at Elevated Temperature: Importance of Coating Coverage

“…The ideal LTO system's CV curve should show symmetric oxidation and reduction peaks. [54] The asymmetric oxidation and reduction peaks, in our case, are because lithiation is the conversion of Ti 4 + to Ti 3 + from the surface to the bulk of the particle, forming a core-shell mechanism, whereas delithiation is a single-step conversion along with the whole particle. [38][39][40][41][42] Figure 6(b) shows the Specific capacity of cLTO, LTO/C-1 h, and LTO/C-3 h with some of the coated LTO (polyimide-modified LTO, [26] C-coated LTO, [55] C-coated LTO [56] ) reported on the literature at various C-rates.…”

Low‐Temperature Electrolyte Design for Lithium‐Ion Batteries: Prospect and Challenges

“…This process is dependent on the electrode-electrolyte interfaces, including the electrolyte component (i. e., the kind of salt, solvent, and additive) and the properties of the SEI and/or CEI. [92] In our opinion, the Li + desolvation process is dominant when the SEI is very conductive or of low activation energy for Li + conduction (e. g., Ohara glass), [93] or there is no or insignificant SEI/CEI on the electrode (e. g., Li 4 Ti 5 O 12 anode, [94] LiFePO 4 cathode [95] ). This viewpoint was confirmed by a recent study, in which the local solvation structure of the electrolyte determines the charge transfer behavior at ultra-low temperatures (e. g., À 40 °C, À 60 °C).…”