Ping He | TU Delft Repository

Realizing four-electron conversion chemistry for all-solid-state Li||I2 batteries at room temperature

Journal article (2025) - Zhu Cheng, Hang Liu, Menghang Zhang, Hui Pan, Chuanchao Sheng, Wei Li, Marnix Wagemaker, Ping He, Haoshen Zhou

Rechargeable Li||I2 batteries based on liquid organic electrolytes suffer from pronounced polyiodides shuttling and safety concerns, which can be potentially tackled by the use of solid-state electrolytes. However, current all-solid-state Li||I2 batteries only demonstrate limited capacity based on a two-electron I−/I2 polyiodides chemistry at elevated temperatures, preventing them from rivaling state-of-the-art lithium-ion batteries. Herein, we report a fast, stable and high-capacity four-electron solid-conversion I−/I2/I+ chemistry in all-solid-state Li||I2 batteries at room temperature. Through the strategic use of a highly conductive, chlorine-rich solid electrolyte Li4.2InCl7.2 as the catholyte, we effectively activate the I2/I+ redox couple. This activation is achieved through a robust I-Cl interhalogen interaction between I2 and the catholyte, facilitated by an interface-mediated heterogeneous oxidation mechanism. Moreover, apart from serving as Li-ion conduction pathway, the Li4.2InCl7.2 catholyte is demonstrated to show a reversible redox behavior and contribute to the electrode capacity without compromising its conductivity. Based on the I−/I2/I+ four-electron chemistry, the as-designed all-solid-state Li||I2 batteries deliver a high specific capacity of 449 mAh g-1 at 44 mA g-1 based on I2 mass and an impressive cycling stability over 600 cycles with a capacity retention of 91% at 440 mA g-1 and at 25 °C. ...

Revealing the Impact of Space-Charge Layers on the Li-Ion Transport in All-Solid-State Batteries

Journal article (2020) - Zhu Cheng, Ming Liu, Swapna Ganapathy, Zhaolong Li, Xiaoyu Zhang, Ping He, Haoshen Zhou, Marnix Wagemaker, Chau Li

The influence of space-charge layers on the ionic charge transport over cathode-solid electrolyte interfaces in all-solid-state batteries remains unclear because of the difficulty to unravel it from other contributions to the ion transport over the interfaces. Here, we reveal the effect of the space-charge layers by systematically tuning the space-charge layer on and off between Li _xV ₂O ₅ and Li _1.5Al _0.5Ge _1.5(PO ₃) ₄ (LAGP), by changing the Li _xV ₂O ₅ potential and selectively measuring the ion transport over the interface by two-dimensional (2D) NMR exchange. The activation energy is demonstrated to be 0.315 eV for lithium-ion exchange over the space-charge-free interface, which increases dramatically to 0.515 eV for the interface with a space-charge layer. Comparison with a space-charge model indicates that the charge distribution due to the space-charge layer is responsible for the increased interface resistance. Thereby, the present work provides selective and quantitative insight into the effect of space-charge layers over electrode-electrolyte interfaces on ionic transport. ...

On the dissipation rate of temperature fluctuations in stably stratified flows

Journal article (2020) - Sukanta Basu, Adam W. DeMarco, Ping He

In this study, we explore several integral and outer length scales of turbulence which can be formulated by using the dissipation of temperature fluctuations (χ) and other relevant variables. Our analyses directly lead to simple yet non-trivial parameterizations for both spatially-averaged χ¯ and the structure parameter of temperature (CT2). For our purposes, we make use of high-fidelity data from direct numerical simulations of stratified channel flows. ...

Parametrizing the Energy Dissipation Rate in Stably Stratified Flows

Journal article (2020) - Sukanta Basu, Ping He, Adam W. DeMarco

We use a database of direct numerical simulations to evaluate parametrizations for energy dissipation rate in stably stratified flows. We show that shear-based formulations are more appropriate for stable boundary layers than commonly used buoyancy-based formulations. As part of the derivations, we explore several length scales of turbulence and investigate their dependence on local stability. ...

On the outer length scales of optical turbulence

Conference paper (2020) - Sukanta Basu, Adam W. DeMarco, Ping He

Kolmogorov's 1941 hypothesis on local isotropy is only applicable for scales smaller than the outer length scales (OLS). By utilizing data from direct numerical simulations and wind tunnel experiments, we quantify OLS in stratified flows. ...