(Invited) Probing the Ultrafast Molecular Transport Kinetics in Microscopic/Second Scale

Abstract

Today, the electrical power supplies pose increasingly stringent requirements on battery package, for example, ultrafast vehicles charging algorithms and high current power supplies. To enable the optimal combination of energy and power capability, it is essential to understand kinetic barriers at all applicable length scales and time scales. On the length scale, we developed single electrode particles of ~25 µm size of a few nAh and adopted it to zoom in the transport of the molecules within the solid|liquid interface, excluding the complicated factors from typical composite electrode microstructures. The particle level electrodynamic measurements conducted in varied electrolyte compositions, reveal the anion group effects in charge transport, which leads to a significantly higher materials utilization during fast charge/discharge in both the single-particle measurements and on macroscopic composite electrodes. Furthermore, molecular dynamics (MD) simulations identify the preferred solvation structures of the liquid electrolytes, and density functional theory (DFT) calculations of their binding energies reveal the origin of the anion group effect. The anion dependence and the solvation lead to the fast kinetics at the interface. On the time scale, we probed the ultrafast transport algorithm with high-frequency modulation. A modulated DC pulse charging and discharging with high-frequency waveforms (up to ~ MHz) are performed to investigate the interfacial transport. This study reveals a possible mechanism by which ion transport kinetics in a lithium-ion battery are responsive to megahertz frequency excitation. Such algorithms are aiming to improve active material utilization as well as cycle life dramatically. This work was supported as part of the NorthEast Center for Chemical Energy Storage (NECCES), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award # DESC0012583.

How Can the Electrode Influence the Formation of the Solid Electrolyte Interface?

“…However, directly measuring these parameters is difficult because of simultaneous and interlaced interfacial and bulk reactions in batteries. Wen et al separated bulk and interfacial charge transport to obtain the interfacial exchange current density for evaluating the interfacial kinetics of two electrolytes in LIBs 68 and developed a three-electrode single-particle electrochemical cell technique. Furthermore, they used electrodynamic protocols and analysis to investigate the interface in batteries.…”

Influence of Tris(trimethylsilyl)phosphite Additive on the Electrochemical Performance of Lithium-ion Batteries Using Thin-film Ni-rich Cathodes

“…9,10 Therefore, it is important to consider the compatibility between electrolytes and electrodes for better CEI formation and to choose the best combination of organic solvents and lithium salts. 11,12 In addition, searching for effective additives for use in electrolytes is another approach for generating a protective CEI on a cathode. 13,14 According to the literature, tris(trimethylsilyl)phosphite (TMSPi) is oxidized at the cathode due to its higher HOMO level, compared to those of other commonly used solvents, and showed excellent CEI formation.…”

High-Voltage and Wide-Temperature Lithium Metal Batteries Enabled by Ultrathin MOF-Derived Solid Polymer Electrolytes with Modulated Ion Transport

“…38 High stability and solubility of Li-bis(trifluoromethanesulfonyl)imide (LiTFSI) make it to be selected as the lithium salt in SPEs. 39 The introduction of ionic liquids (ILs) into SPEs has been one of the most feasible approaches to increase ionic conductivity and construct reliable interfacial contact within LMBs since 1993. 40−42 In comparison to the conventional organic liquid e l e c t r o l y t e s , 1 -e t h y l -3 -m e t h y l i m i d a z o l i u m bis(trifluoromethylsulfonyl)imide (EMIMTFSI) is advantageous because of its robust ionic conductivity and excellent electrochemical and thermal stability, thus showing great potential in being confined in the SPE.…”