Jihui Yang

The phonon dynamics of breathing kagome material Nb ₃ Br ₈ are investigated via linearly polarized Raman spectroscopy and density-functional theory.

This Review explores the status and progress made over the past decade in the areas of raw material mining, battery materials and components scale-up, processing, and manufacturing. While substantial advancements have been achieved in understanding battery materials, the transition to large-scale manufacturing introduces scientific challenges that must be addressed from multiple perspectives. Rather than focusing on new material discoveries or incremental performance improvements, this Review focuses on the critical issues that arise in battery manufacturing and highlights the importance of cost-oriented fundamental research to bridge the knowledge gap between fundamental research and industrial production. Challenges and opportunities in integrating machine learning (ML) and artificial intelligence (AI) to digitalize the manufacturing process and eventually realize fully autonomous production are discussed. The review also emphasizes the pressing need for workforce development to meet the growing demands of the battery industry. Potential strategies are suggested for accelerating the manufacturing of current and future battery technologies, ensuring that the workforce is equipped with the necessary skills to support research, development, and large-scale production.

In this study, we investigate the rate performance limits in LiNi_0.6Mn_0.2Co_0.2O₂ cathodes for lithium-ion batteries, focusing on how cathode thickness, porosity, and threshold voltage impact discharge capacity. By conducting galvanostatic discharge experiments across a wide range of current densities using cathodes of varying thicknesses and porosities, we identify two distinct rate-limiting mechanisms: ionic liquid-diffusion and Ohmic/charge-transfer limitations. Our findings show that thick, dense cathodes are primarily limited by lithium diffusion in the electrolyte, while thinner and more porous cathodes are dominated by Ohmic/charge-transfer limitations, particularly at higher lower cutoff voltages. Crucially, these results allow us to identify the rate-limiting mechanisms in different cathode configurations, offering clear insights into how cathode design can be optimized for improved performance. Understanding these mechanisms is essential for designing next-generation batteries with enhanced rate performance, which is critical for applications such as electric vehicles and renewable energy storage systems.

Measuring and controlling the density of states (DOS) and defect states of two-dimensional van der Waals materials is of profound importance for understanding their unique physical properties, and for advancing their future practical applications. However, probing their defect states typically requires experiments performed at cryogenic temperatures and/or in ultra-high vacuum conditions, severely constraining efforts to monitor the electronic structure evolution of these materials under useful device operating conditions. Here, we develop a new electrochemical quantum capacitance spectroscopy (EQCS) technique for detecting the absolute energies of defect states and band edges in an ambient environment. We demonstrate the viability of this method with a variety of two-dimensional material systems, with the ability to easily extend to many more. The highest energy resolution achieved at room temperature, 116 meV, approaches the theoretical limit of 91 meV (3.5k_BT). The in-situ EQCS platform can be further used to monitor and manipulate the DOS in real-time, enabling a controlled enhancement of electrochemical reactions. Notably, band shifts driven by as little as ≈ 1% mechanical strain can increase of the catalytic activity for hydrogen generation by half an order of magnitude. The EQCS platform provides a powerful new method for probing and manipulating the intrinsic DOS and defect states of 2D materials in ambient environments.

Niobium chloride (Nb₃Cl₈) is a layered two-dimensional semiconducting material with many exotic properties including a breathing kagome lattice, a topological flat band in its band structure, and a crystal structure that undergoes a structural and magnetic phase transition at temperatures below 90 K. Despite being a remarkable material with fascinating new physics, the understanding of its phonon properties is at its infancy. In this study, we investigate the phonon dynamics of Nb₃Cl₈ in bulk and few layer flakes using polarized Raman spectroscopy and density-functional theory (DFT) analysis to determine the material’s vibrational modes, as well as their symmetrical representations and atomic displacements. We experimentally resolved 12 phonon modes, five of which are A _1g modes while the remaining seven are E_g modes, which is in strong agreement with our DFT calculation. Layer-dependent results suggest that the Raman peak positions are mostly insensitive to changes in layer thickness, while peak intensity and full width at half maximum are affected. Raman measurements as a function of excitation wavelength (473–785 nm) show a significant increase of the peak intensities when using a 473 nm excitation source, suggesting a near resonant condition. Temperature-dependent Raman experiments carried out above and below the transition temperature did not show any change in the symmetries of the phonon modes, suggesting that the structural phase transition is likely from the high temperature P 3 m ˉ 1 phase to the low-temperature R 3 m ˉ phase. Magneto-Raman measurements carried out at 140 and 2 K between −2 and 2 T show that the Raman modes are not magnetically coupled. Overall, our study presented here significantly advances the fundamental understanding of layered Nb₃Cl₈ material which can be further exploited for future applications.

Lithium (Li) metal battery technology has attracted world-wide attention because of its high energy density, but its practical application is hindered by several challenges, with one significant issue being the large volume change and cell swelling. While external pressure is known to have a profound effect on cell performance, there are currently no reports exploring the relationship between external pressure and the electroplating of Li+ in large-format pouch cells to enhance overall performance. Here we investigate the influence of externally applied pressure on the electroplating and stripping of lithium metal in 350 Wh/kg pouch cells. A hybrid constant gap and constant pressure design is designed to apply a minimal external pressure for practical application. The self-generated pressures are monitored and quantified which are further correlated to the observed charge-discharge processes. A two-stage cycling process is observed. In the first stage, Li+ ions utilized are mainly supplied by the cathode which shuttle between the cathode and anode with minimal Li loss which minimizes cell swelling but only happens when pressure is applied appropriately. In the second stage, Li from the Li foil anode participates in the reaction and the thickness of the anode gradually increases. However, even after extensive cycling, cell swelling remains less than 10%, comparable to that of state-of-the-art Li-ion batteries. In addition, the pressure distribution along the horizontal direction across the surface of Li metal pouch cell reveals a complex behavior of Li+ migration during the electroplating (charge) process. The external pressure encourages a preferred plating process of Li in the central region, necessitating the development of new strategies to address uneven Li plating and utilization to advance Li metal battery technology.