Search for: All records

Abstract All‐solid‐state sodium ion batteries (AS³iBs) are highly sought after for stationary energy storage systems due to their suitable safety and stability over a wide temperature range. Hard carbon (HC), which is low cost, exhibits a low redox potential, and a high capacity, is integral to achieve a practical large‐scale sodium‐ion battery. However, the energy density of the battery utilizing this anode material is hampered by its low initial Coulombic efficiency (ICE). Herein, two strategies, namely i) additional pyrolysis and ii) presodiation by thermal decomposition of NaBH₄, are explored to improve the ICE of pristine HC. Raman spectroscopy, X‐ray photoelectron spectroscopy, and electrochemical characterizations elucidate that the thermal treatment increases the C_sp2content in the HC structure, while the presodiation supplies the sodium to occupy the intrinsic irreversible sites. Consequently, presodiated HC exhibits an outstanding ICE (>99%) compared to the thermally treated (90%) or pristine HC (83%) in half‐cell configurations. More importantly, AS³iB using presodiated HC and NaCrO₂as the anode and cathode, respectively, exhibits a high ICE of 92% and an initial discharge energy density of . 

Abstract Non‐equilibrium defects often dictate the macroscopic properties of materials. They largely define the reversibility and kinetics of processes in intercalation hosts in rechargeable batteries. Recently, imaging methods have demonstrated that transient dislocations briefly appear in intercalation hosts during ion diffusion. Despite new discoveries, the understanding of impact, formation and self‐healing mechanisms of transient defects, including and beyond dislocations, is lacking. Here, operando X‐ray Bragg Coherent Diffractive Imaging (BCDI) and diffraction peak analysis capture the stages of formation of a unique metastable domain boundary, defect self‐healing, and resolve the local impact of defects on ionic diffusion in Na_xNi_1−yMn_yO₂intercalation hosts in a charging sodium‐ion battery. Results, applicable to a wide range of layered intercalation materials due to the shared nature of framework layers, elucidate new dynamics of transient defects and their connection to macroscopic properties, and suggest how to control the nanostructure dynamics. 

Abstract All‐solid‐state batteries are emerging as potential successors in energy storage technologies due to their increased safety, stemming from replacing organic liquid electrolytes in conventional Li‐ion batteries with less flammable solid‐state electrolytes. However, all‐solid‐state batteries require precise control over cycling pressure to maintain effective interfacial contacts between materials. Traditional uniaxial cell holders, often used in battery research, face challenges in accommodating electrode volume changes, providing uniform pressure distribution, and maintaining consistent pressure over time. This study introduces isostatic pouch cell holders utilizing air as pressurizing media to achieve uniform and accurately regulated cycling pressure. LiNi_0.8Co_0.1Mn_0.1O₂| Li₆PS₅Cl | Si pouch cells are fabricated and tested under 1 to 5 MPa pressures, revealing improved electrochemical performance with higher cycling pressures, with 2 MPa as the minimum for optimal operation. A bilayer pouch cell with a theoretical capacity of 100 mAh, cycled with an isostatic pouch cell holder, demonstrated a first‐cycle Coulombic efficiency of 76.9% and a discharge capacity of 173.6 mAh g⁻¹(88.1 mAh), maintaining 83.6% capacity after 100 cycles. These findings underscore the effectiveness of isostatic pouch cell holders in enhancing the performance and practical application of all‐solid‐state batteries. 

Abstract The dry process is a promising fabrication method for all‐solid‐state batteries (ASSBs) to eliminate energy‐intense drying and solvent recovery steps and to prevent degradation of solid‐state electrolytes (SSEs) in the wet process. While previous studies have utilized the dry process to enable thin SSE films, systematic studies on their fabrication, physical and electrochemical properties, and electrochemical performance are unprecedented. Here, different fabrication parameters are studied to understand polytetrafluoroethylene (PTFE) binder fibrillation and its impact on the physio‐electrochemical properties of SSE films, as well as the cycling stability of ASSBs resulting from such SSEs. A counter‐balancing relation between the physio‐electrochemical properties and cycling stability is observed, which is due to the propagating behavior of PTFE reduction (both chemically and electrochemically) through the fibrillation network, resulting in cell failure from current leakage and ion blockage. By controlling PTFE fibrillation, a bilayer configuration of SSE film to enable physio‐electrochemically durable SSE film for both good cycling stability and charge storage capability of ASSBs is demonstrated. 

Abstract Lithium/fluorinated graphite (Li/CF_x) primary batteries show great promise for applications in a wide range of energy storage systems due to their high energy density (>2100 Wh kg^–1) and low self‐discharge rate (<0.5% per year at 25 °C). While the electrochemical performance of the CF_xcathode is indeed promising, the discharge reaction mechanism is not thoroughly understood to date. In this article, a multiscale investigation of the CF_xdischarge mechanism is performed using a novel cathode structure to minimize the carbon and fluorine additives for precise cathode characterizations. Titration gas chromatography, X‐ray diffraction, Raman spectroscopy, X‐ray photoelectron spectroscopy, scanning electron microscopy, cross‐sectional focused ion beam, high‐resolution transmission electron microscopy, and scanning transmission electron microscopy with electron energy loss spectroscopy are utilized to investigate this system. Results show no metallic lithium deposition or intercalation during the discharge reaction. Crystalline lithium fluoride particles uniformly distributed with <10 nm sizes into the CF_xlayers, and carbon with lower sp²content similar to the hard‐carbon structure are the products during discharge. This work deepens the understanding of CF_xas a high energy density cathode material and highlights the need for future investigations on primary battery materials to advance performance. 

Abstract With the rapid growth of the lithium‐ion battery (LIBs) market, recycling and re‐use of end‐of‐life LIBs to reclaim lithium (Li) and transition metal (TM) resources (e.g., Co, Ni), as well as eliminating pollution from disposal of waste batteries, has become an urgent task. Here, for the first time the ambient‐pressure relithiation of degraded LiNi_0.5Co_0.2Mn_0.3O₂(NCM523) cathodes via eutectic Li⁺molten‐salt solutions is successfully demonstrated. Combining such a low‐temperature relithiation process with a well‐designed thermal annealing step, NCM523 cathode particles with significant Li loss (≈40%) and capacity degradation (≈50%) can be successfully regenerated to achieve their original composition and crystal structures, leading to effective recovery of their capacity, cycling stability, and rate capability to the levels of the pristine materials. Advanced characterization tools including atomic resolution electron microscopy imaging and electron energy loss spectroscopy are combined to demonstrate that NCM523's original layered crystal structure is recovered. For the first time, it is shown that layer‐to‐rock salt phase change on the surfaces and subsurfaces of the cathode materials can be reversed if lithium can be incorporated back to the material. The result suggests the great promise of using eutectic Li⁺molten–salt solutions for ambient‐pressure relithiation to recycle and remanufacture degraded LIB cathode materials. 

Haptic devices are in general more adept at mimicking the bulk properties of materials than they are at mimicking the surface properties. Herein, a haptic glove is described which is capable of producing sensations reminiscent of three types of near‐surface properties: hardness, temperature, and roughness. To accomplish this mixed mode of stimulation, three types of haptic actuators are combined: vibrotactile motors, thermoelectric devices, and electrotactile electrodes made from a stretchable conductive polymer synthesized in the laboratory. This polymer consists of a stretchable polyanion which serves as a scaffold for the polymerization of poly(3,4‐ethylenedioxythiophene). The scaffold is synthesized using controlled radical polymerization to afford material of low dispersity, relatively high conductivity, and low impedance relative to metals. The glove is equipped with flex sensors to make it possible to control a robotic hand and a hand in virtual reality (VR). In psychophysical experiments, human participants are able to discern combinations of electrotactile, vibrotactile, and thermal stimulation in VR. Participants trained to associate these sensations with roughness, hardness, and temperature have an overall accuracy of 98%, whereas untrained participants have an accuracy of 85%. Sensations can similarly be conveyed using a robotic hand equipped with sensors for pressure and temperature.