Operando Neutron Imaging of Lithium Flux and Gradient Cathode Design for Enhanced Kinetics in High‐Loading All‐Solid‐State Li─S Batteries

Advanced Materials · 2025-10-25 · 1 citations

Abstract All‐solid‐state Li–sulfur batteries (ASSLSBs) are considered promising candidates for next‐generation energy storage owing to their inherent safety, high energy density, and abundant sulfur resources. However, slow redox kinetics greatly limit sulfur utilization during solid‐solid sulfur reactions, leading to significant challenges to achieve efficient performance in high‐mass‐loading ASSLSBs. Here, operando neutron image is employed to directly visualize, for the first time, that sluggish Li + transport kinetics and the uneven distribution of Li + during cathodic reactions are critical factors limiting sulfur conversion. To address this issue, gradient cathode architectures comprising three and five layers are designed, in which catholyte concentrations are strategically varied to optimize Li‐ion flux and enhance ionic conductivity of the whole composite cathode electrode. Operando neutron imaging distinctly visualizes and confirms that three‐layer gradient approach significantly enhances Li‐ion mobility, resulting in more uniform redox reactions and greatly improved sulfur utilization compared to traditional non‐gradient structures. Consequently, the three‐layer gradient cathode achieves superior rate performance and reduced electrode polarization at high sulfur mass loadings of 4.5 and 6.0 mg cm −2 . Furthermore, the applicability and scalability of this design are demonstrated in a five‐layer gradient cathode architecture, achieving an impressive discharge specific capacity increase from 656 mAh g −1 (three‐layer gradient) to 1232 mAh g −1 at 1/20 C for ultra‐high sulfur loading of 7.5 mg cm −2 . This innovative gradient cathode design offers substantial advancements in understanding and overcoming Li‐ion transport limitations, paving the way toward practical, high‐energy‐density ASSLSBs.

Interplay of Lithium Intercalation and Plating in Graphite Anodes during Fast Charging: Insights from Operando Experiments and Modeling

ECS Meeting Abstracts · 2025-11-24

Fast charging of high-capacity anodes presents significant challenges due to lithium plating, which can cause capacity fade and safety concerns. Therefore, accurately predicting plating onset and gaining deeper understanding of this electrochemical process is essential for new battery designs. However, porous electrode theory models (e.g., the pseudo-2D (p2D) model) used to describe these phenomena are notoriously challenging to calibrate due to mathematical complexity and a large number of input parameters. These challenges limit model predictive power and design capabilities. This work studies the process of fast charging in conventional and architectured graphite electrodes by simultaneously measuring local reaction progression and lithium plating, employing a large number of carefully designed operando and in-situ imaging experiments. Carefully designed models are used to study these processes, and theory is developed to describe both the complex interplay of plating and reaction dynamics. Simple analytical relationships, derived from porous electrode theory, describe key interactions between: material variables (electrode thermodynamics, electrolyte transport, interfacial reactions), multiscale mechanisms (intra-particle and electrode level transport), charging conditions (e.g., C-rate) and electrode geometries (i.e., architectured vs unstructured designs). Numerical and analytical solutions predict experimentally observed reaction distributions and plating onset with high accuracy. Remarkably, it is shown that reaction histories of electrodes of different thicknesses and charged at different rates show self-similar intercalation profiles, confirming theoretical predictions. Experiments and theory study the multiscale behavior of reaction dynamics and plating in high-capacity anodes with various particle sizes. Together, this work reveals underlying simplicity in the complex phenomena underpinning lithium plating and reaction behavior which limit fast charge rate in graphite anodes. Further, it describes a comprehensive methodology for accurately calibrating advanced modeling at high charge rate conditions. Thus, while experimental work is conducted in graphite half-cells, this theoretical analysis is broadly applicable to other electrode and electrolyte materials.

Operando neutron imaging-guided gradient design of Li-ion solid conductor for high-mass-loading cathodes

Nature Communications · 2025-08-18 · 15 citations

High-mass-loading cathodes are crucial for achieving high energy density in all-solid-state batteries from the lab scale to industry. However, as mass-loading increases, electrochemical performance is significantly compromised due to sluggish kinetics. In this work, operando neutron imaging is deployed on a high-mass-loading NMC 811 cathode of 33 mg/cm2 (5.0 mAh/cm2) and directly visualizes the lithiation prioritization of the cathode active material (CAM) from the solid electrolyte membrane side to the current collector side. In addition to the tortuosity, another key limitation on ion transfer in the cathode arises from the mismatch between the uniform distribution of the solid electrolyte (catholyte) in the conventional composite cathode and the non-uniform Li+ flux generated by the faradaic reaction of CAMs. Therefore, we engineer a gradient in the catholyte concentration to match the Li+ flux distribution as a means of eliminating the ion transfer obstacle. This approach demonstrates enhanced rate performance, even with high-mass-loading cathodes. A LiCoO2 composite cathode with 100 mg/cm2 high-mass-loading exhibits an areal capacity of 10.4 mAh/cm2 at a current density of 2.25 mA/cm2. This work provides insight into the ion-transport limitation in thick cathodes and demonstrates an effective gradient design to overcome the kinetic barrier and achieve high battery performance. High-mass-loading electrodes are essential for high-energy all-solid-state batteries but suffer from poor kinetics. Here, authors use neutron imaging to identify ion-transport limitations and introduce a gradient solid electrolyte design that improves battery mass-loading and rate performance.

Direct in situ Observation of Interlayer Shear-Based Pull-Out as Crack-Bridging Mechanisms in Nanocomposites of Silicon Nitride and Boron Nitride Nanoplatelets

SSRN Electronic Journal · 2025-01-01

Scaling Models for Coupled Intercalation Dynamics, Electrolyte Depletion, and Lithium Plating during Fast Charging

Journal of The Electrochemical Society · 2025-12-09

Fast charging of high capacity electrodes is an engineering challenge due to lithium plating and electrolyte depletion, which can lead to poor battery life and safety issues. Therefore, accurately predicting thresholds for safe and efficient operation is crucial for robust battery design. While the most commonly used porous electrode theory (PET)-based models (e.g., the pseudo-2D model) can predict detailed behavior of the local electrochemical environment, they are notoriously complex and difficult to calibrate. Scaling-based models provide a simplified means to understand these complex systems, reduce a vast parameter space, and generalize experimental findings. Here, a scaling framework is derived from PET to predict the coupled behavior of electrolyte transport, reaction distribution, and ohmic losses during fast charging. Limits in system operation, including lithium plating onset and electrolyte depletion, are predicted by critical values of four non-dimensional numbers. These critical values provide theoretical limits on C-rates for safe operation from electrode mass loading, and material properties of the electrode and electrolyte. Theoretical predictions are in excellent agreement with experimentally validated measurements of plating onset and a rigorously calibrated fast-charging pseudo-2D model of graphite half-cells. The scaling behavior derived here may be generalized to a range of electrodes, electrolytes and charging conditions.

Interplay of intercalation dynamics and lithium plating in monolithic and architectured graphite anodes during fast charging

Energy & Environmental Science · 2024-01-01 · 26 citations

Fast charging of high-capacity anodes is challenging due to lithium plating reactions, which lead to poor cycling performance and safety concerns.

Unraveling Lithium Plating and SEI Properties during Fast Charging of Li-Ion Batteries

ECS Meeting Abstracts · 2024-11-22

As the electric vehicles market expands rapidly, the need for fast-charging lithium-ion batteries become increasingly imperative. However, the persistence of lithium plating, particularly on graphite negative electrodes in state-of-the-art lithium-ion batteries (LIBs), continues to pose performance degradation and safety hazards. Understanding the dominant limitation mechanism remains a subject of controversy. To evaluate the dominant role among particle-level diffusion and charge-transfer at the electrode interphase, we utilized ultra-thin electrodes with different-size graphite particles in conjunction with a pseudo-2-dimensional (P2D) model to evaluate the most likely plating mechanism. The superior performance of small graphite particles, coupled with well-matched modeling data, indicated that particle-level diffusion is the primary mechanism contributing to plating at high rates. Furthermore, we investigated how fast-charging rates influence the morphology of lithium dendrites and their solid electrolyte interphase (SEI) properties using 1.6 Ah pouch cells featuring a LiNi 0.5 Mn 0.3 Co 0.2 O 2 cathode and graphite anode provided by Nanoramic Laboratories. Our investigation involved a comparative analysis of the aging behavior of NMC/Gr cells subjected to various charging rates — 0.5C, 2C, 4C, and 6C. Through a series of post-mortem characterizations, including electrochemical impedance spectroscopy (EIS), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), we identified distinct dendrite morphologies at the graphite anode under varying charging rates, along with fluorine-richer SEI for faster charging process. These findings provide a comprehensive understanding of lithium plating mechanisms, offering valuable insights into the fast-charging behavior in practical Li-ion battery applications. Acknowledgement This material is based upon work supported by the U. S. Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE) under the Advanced Manufacturing Office, award number DE-EE0009111. This work was mainly conducted at the Cell Analysis, Modeling, and Prototyping Facility at Argonne National Laboratory. We used resources of the Center for Nanoscale Materials, U.S. Department of Energy (DOE) Office of Science User Facilities operated for the DOE Office of Science by Argonne National Laboratory under Contract DE-AC02-06CH11357.

Understanding particle size effect on fast-charging behavior of graphite anode using ultra-thin-layer electrodes

Journal of Energy Storage · 2024-11-17 · 9 citations

Lithium Dendrite Deflection at Mixed Ionic–Electronic Conducting Interlayers in Solid Electrolytes

Advanced Energy Materials · 2024-11-24 · 47 citations

Abstract Solid state lithium metal batteries using garnet solid electrolytes such as LLZTO (Li 6.4 La 3 Zr 1.5 Ta 0.5 O 12 ) promise substantial improvements in energy density and safety. However, practical implementation is hindered by lithium dendrite penetration at high current densities. Recent work shows that internal electrochemically induced mechanical stresses are large enough to propagate lithium dendrites and subsequently fracture solid electrolytes. This study builds on this understanding and demonstrates that stress‐driven dendrite propagation can be controlled via deflection at weakly bonded internal interfaces. This approach, based on a fracture‐mechanics analysis of multilayered composites, is investigated with a variety of interlayer materials that are embedded into LLZTO. The viability and effectiveness of dendrite deflection are most clearly evident with reduced graphene oxide where the critical current density increased from 0.6 to 3.8 mA cm −2 . In this material, both the weak interface with LLZTO and the mixed ionic–electronic conducting nature of the interlayer appear to contribute to the improved performance. Additional insight into the mechanics of multilayered electrolytes is also obtained with finite element modeling. The overall results present a promising proof‐of‐concept demonstration along with important generalized design guidelines for creating multilayered solid electrolyte architectures that can enable high‐performance solid‐state batteries.

Promoting electrochemical rates by concurrent ionic-electronic conductivity enhancement in high mass loading cathode electrode

Energy storage materials · 2024-06-13 · 14 citations