Thick electrodes, although promising toward high-energy battery systems, suffer from restricted lithium-ion transport kinetics due to prolonged diffusion lengths and tortuous transport pathways. Despite the emerging low-tortuosity designs, capacity retention under higher current densities is still limited. Herein, we employ a modified ice-templating method to fabricate low-tortuosity porous electrodes with tunable wall thickness and channel width and systematically investigate the critical impacts of the fine structural parameters on the thick electrode electrochemistry. While the porous electrodes with thick walls show diminished capability under a C-rate larger than 1.5 C, those with thinner walls could maintain ∼70% capacity under 2.5 C. The superior capacity retention is ascribed to the fast diffusion into the thin lamellar walls compared with their thicker counterparts. This study provides deeper insights into structure-affected electrochemistry and opens up new perspective of 3D porous architectural designs for high-energy and high-power electrodes.

The applications of lithium-ion batteries are limited, as they cannot fulfill the requirements for high power output and reversible energy storage. The main challenges are centered around developing electrode architectures to produce both high energy and power. As one of the key components, conductive fillers play a vital role in battery electrodes, contributing to the electrical conductivity and shaping electrode structures, which significantly determine the rate capability. In this study, the dimensionality effect of conductive fillers on electrochemical performance is elucidated in thick electrodes for scalable energy storage. In particular, three types of conductive fillers: single-walled carbon nanotubes, graphene nanosheets, and Super P, are studied using commercial LiNi1/3Co1/3Mn1/3O2 as the model material. The role of these conductive fillers on electrode morphology, electrical percolation, and electrochemical properties of LiNi1/3Co1/3Mn1/3O2 electrodes is comparatively investigated. Notably, electrodes with single-walled carbon nanotubes exhibit superior rate performance owing to both high electrical conductivity and tight wrapping architecture, which was further revealed by various advanced structural and electrochemical characterization. This work demonstrates the dimensionality effect of conductive fillers on both electrochemistry and electrode architecture and highlights the advantages of 1D conductive filler in thick electrodes, which brings new insights in future high energy/power systems.

Because it has been demonstrated to be effective toward faster ion diffusion inside the pore space, low-tortuosity porous architecture has become the focus in thick electrode designs, and other possibilities are rarely investigated. To advance current understanding in the structure-affected electrochemistry and to broaden horizons for thick electrode designs, we present a gradient electrode design, where porous channels are vertically aligned with smaller openings on one end and larger openings on the other. With its 3D morphology carefully visualized by Raman mapping, the electrochemical properties between opposite orientations of the gradient electrodes are compared, and faster energy storage kinetics is found in larger openings and more concentrated active material near the separator. As further verified by simulation, this study on gradient electrode design deepens the knowledge of structure-related electrochemistry and brings perspectives in high-energy battery electrode designs.

Aqueous Zn/MnO2 batteries (AZMOB) with mildly acidic electrolytes hold promise as potential green grid-level energy storage solutions for clean power generation. Mechanistic understanding is critical to advance capacity retention needed by the application but is complex due to the evolution of the cathode solid phases and the presence of dissolved manganese in the electrolyte due to a dissolution–deposition redox process. This work introduces operando multiphase extended X-ray absorption fine structure (EXAFS) analysis enabling simultaneous characterization of both aqueous and solid phases involved in the Mn redox reactions. The methodology was successfully conducted in multiple electrolytes (ZnSO4, Zn(CF3SO3)2, and Zn(CH3COO)2) revealing similar manganese coordination environments but quantitative differences in distribution of Mnn+ species in the solid and solution phases. Complementary Raman spectroscopy was utilized to identify the less crystalline Mn-containing products formed under charge at the cathodes. This was further augmented by transmission electron microscopy (TEM) to reveal the morphology and surface condition of the deposited solids. The results demonstrate an effective approach for bulk-level characterization of poorly crystalline multiphase solids while simultaneously gaining insight into the dissolved transition-metal species in solution. This work provides demonstration of a useful approach toward gaining insight into complex electrochemical mechanisms where both solid state and dissolved active materials are important contributors to redox activity.

The phase distribution of lithiated LVO in thick (~500 µm) porous electrodes (TPE) designed to facilitate both ion and electron transport was determined using synchrotron-based operando energy dispersive x-ray diffraction...