as smartphones, electric vehicles, and energy storage systems depend on LIBs to provide the necessary power for optimal performance. Today, that dependency continues to grow at an exponential rate as the portfolio of electronic devices and vehicles diversifies. The common denominator for the myriad of commercialized devices is the constant demand for high power and long usage time. Accordingly, the frontrunners of today's technology are striving to optimize LIBs to meet such performance demands. While such efforts have extended the usage time of various devices, this direction has also exposed critical issues with current battery technology: safety and cost.The main cause for safety hazards with LIBs is linked to the use of organic electrolytes. In the unfortunate event of a short circuit in a battery, a sudden burst of exothermic reactions is accelerated by the presence of organic solvents, which act as fuel for ensuing fires. This problem is exacerbated in high energy density configurations where materials are densely packed. The risk of fire hazards has prompted a search for alternative battery systems, among which rechargeable aqueous batteries have garnered significant attention as viable candidates for safe batteries. Replacing the organic solvent with water as the electrolyte medium has significant implications. In addition to the benefit of heightened safety, water has a high ionic conductivity compared to conventional organic solvents (2-3 orders of magnitude higher), a useful quality for high C-rate operations. Moreover, the use of water can reduce costs incurred from moisture regulation during manufacturing.Unfortunately, despite these attractive aspects, aqueous electrolytes impose certain barriers. Most critically, the thermodynamic stability window of water is limited to 1.23 V, beyond which detrimental hydrogen and oxygen evolution reactions (HER/OER) occur. As a result, even if kinetic overpotentials are taken into account, the operating potential windows of aqueous batteries are significantly narrower than those of their organic counterparts. This motivates the search for adequate materials that provide maximum energy within such a narrow voltage window. The prevalent layered oxide/graphite system used in conventional LIBs is no longer an option in this system due to such voltage constraints. Instead, on the anode side, zinc (Zn) metal is considered to be a promising candidate. [1] Not only is Zn abundant in nature, nontoxic, and cheap, but its metallic Aqueous zinc ion batteries (AZIBs) are steadily gaining attention based on their attractive merits regarding cost and safety. However, there are many obstacles to overcome, especially in terms of finding suitable cathode materials and elucidating their reaction mechanisms. Here, a mixed-valence vanadium oxide, V 6 O 13 , that functions as a stable cathode material in mildly acidic aqueous electrolytes is reported. Paired with a zinc metal anode, this material exhibits performance metrics of 360 mAh g −1 at 0.2 A g −1 , 92% capacity retention after...
Li-ion batteries have revolutionized the portable electronics industry and empowered the electric vehicle (EV) revolution. Unfortunately, traditional Li-ion chemistry is approaching its physicochemical limit. The demand for higher density (longer range), high power (fast charging), and safer EVs has recently created a resurgence of interest in solid state batteries (SSB). Historically, research has focused on improving the ionic conductivity of solid electrolytes, yet ceramic solids now deliver sufficient ionic conductivity. The barriers lie within the interfaces between the electrolyte and the two electrodes, in the mechanical properties throughout the device, and in processing scalability. In 2017 the Faraday Institution, the UK’s independent institute for electrochemical energy storage research, launched the SOLBAT (solid-state lithium metal anode battery) project, aimed at understanding the fundamental science underpinning the problems of SSBs, and recognising that the paucity of such understanding is the major barrier to progress. The purpose of this Roadmap is to present an overview of the fundamental challenges impeding the development of SSBs, the advances in science and technology necessary to understand the underlying science, and the multidisciplinary approach being taken by SOLBAT researchers in facing these challenges. It is our hope that this Roadmap will guide academia, industry, and funding agencies towards the further development of these batteries in the future.
The intrinsic limitations of lithium-ion batteries (LIBs) with regard to safety, cost, and the availability of raw materials have promoted research on so-called "post-LIBs". The recent intense research of post-LIBs provides an invaluable lesson that existing electrode materials used in LIBs may not perform as well in post-LIBs, calling for new material designs compliant with emerging batteries based on new chemistries. One promising approach in this direction is the development of materials with intercalated water or organic molecules, as these materials demonstrate superior electrochemical performance in emerging battery systems. The enlarged ionic channel dimensions and effective shielding of the electrostatic interaction between carrier ions and the lattice host are the origins of the observed electrochemical performance. Moreover, these intercalants serve as interlayer pillars to sustain the framework for prolonged cycles. Representative examples of such intercalated materials applied to batteries based on Li , Na , Mg , and Zn ions and supercapacitors are considered, along with their impact in materials research.
Solid-state batteries (SSBs) have received attention as a next-generation energy storage technology due to their potential to superior deliver energy density and safety compared to commercial Li-ion batteries. One of the main challenges limiting their practical implementation is the rapid capacity decay caused by the loss of contact between the cathode active material and the solid electrolyte upon cycling. Here, we use the promising high-voltage, low-cost LiNi0.5Mn1.5O4 (LNMO) as a model system to demonstrate the importance of the cathode microstructure in SSBs. We design Al2O3-coated LNMO particles with a hollow microstructure aimed at suppressing electrolyte decomposition, minimizing volume change during cycling, and shortening the Li diffusion pathway to achieve maximum cathode utilization. When cycled with a Li6PS5Cl solid electrolyte, we demonstrate a capacity retention above 70% after 100 cycles, with an active material loading of 27 mg cm–2 (2.2 mAh cm–2) at a current density of 0.8 mA cm–2.
<div><div><div><p>The high voltage (4.7 V vs. Li+ /Li) spinel lithium nickel manganese oxide (LiNi0.5 Mn1.5 O4 , LNMO) is a promising candidate for the next-generation of lithium ion batteries due to its high energy density, low cost and environmental impact. However, poor cycling performance at high cutoff potentials limits its commercialization. Herein, hollow structured LNMO is synergistically paired with an ionic liquid electrolyte, 1M lithium bis(fluorosulfonyl)imide (LiFSI) in N-propyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide (Pyr1,3 FSI) to achieve stable cycling performance and improved rate capability. The optimized cathode-electrolyte system exhibits extended cycling performance (>85% capacity retention after 300 cycles) and high rate performance (106.2mAhg–1 at 5C) even at an elevated temperature of 65 ◦C. X-ray photoelectron spectroscopy and spatially resolved x-ray fluorescence analyses confirm the formation of a robust, LiF-rich cathode electrolyte interphase. This study presents a comprehensive design strategy to improve the electrochemical performance of high-voltage cathode materials.</p></div></div></div>
The electrochemical (de)intercalation reactions of lithium ions are initiated at the electrode surface in contact with an electrolyte solution. Therefore, substantial structural degradation, which shortens the cycle life of cells, is frequently observed at the surface of cathode particles, including lithium–metal intermixing, phase transitions, and dissolution of lithium and transition metals into the electrolyte. Furthermore, in contrast to the strict restriction of moisture in lithium‐ion cells with nonaqueous organic electrolytes, electrode materials in aqueous‐electrolyte cells are under much more reactive environments with water and oxygen, thereby leading to serious surface chemical reactions on the cathode particles. The present article presents key results regarding structural and composition variations at the surface of oxide‐based cathodes in both high‐performance nonaqueous and recently proposed aqueous lithium‐ion batteries; in particular, focusing on direct atomic‐scale observations preformed by means of scanning transmission electron microscopy. Precise identification of surface degradation at the atomic level is thus emphasized because it can provide significant insights into overcoming the limitations of current lithium‐ion batteries.
Platinum single-site catalysts (SSCs) are a promising technology for the production of hydrogen from clean energy sources. They have high activity and maximal platinum-atom utilization. However, the bonding environment of platinum during operation is poorly understood. In this work, we present a mechanistic study of platinum SSCs using operando, synchrotron-X-ray absorption spectroscopy. We synthesize an atomically dispersed platinum complex with aniline and chloride ligands onto graphene and characterize it with ex-situ electron microscopy, X-ray diffractometry, X-ray photoelectron spectroscopy, X-ray absorption near-edge structure spectroscopy (XANES), and extended X-ray absorption fine structure spectroscopy (EXAFS). Then, by operando EXAFS and XANES, we show that as a negatively biased potential is applied, the Pt–N bonds break first followed by the Pt–Cl bonds. The platinum is reduced from platinum(II) to metallic platinum(0) by the onset of the hydrogen-evolution reaction at 0 V. Furthermore, we observe an increase in Pt–Pt bonding, indicating the formation of platinum agglomerates. Together, these results indicate that while aniline is used to prepare platinum SSCs, the single-site complexes are decomposed and platinum agglomerates at operating potentials. This work is an important contribution to the understanding of the evolution of bonding environment in SSCs and provides some molecular insights into how platinum agglomeration causes the deactivation of SSCs over time.
Layered lithium cobalt oxide (LiCoO2, LCO), which serves as a structural motif for the widely adopted layered cathodes in lithium-ion batteries, has a long history, and its unstable phase transition during high-voltage operation (∼4.5 V) remains an intractable problem. Many research strategies, such as surface coating and immobile ion doping, have been proposed to address this issue, but a clear understanding of the effects has not been demonstrated because of various potential parameters (e.g., particle size, shape, and dopant content). Herein, we report a molten salt synthesis method that produces sphere-like single-crystal magnesium (Mg)-doped LCO. In situ X-ray diffraction and X-ray absorption fine structure analyses confirmed that the lattice strain was effectively alleviated by the effects of both the particle shape and Mg doping compared to the plate-like and sphere-like single-crystal LCO samples. Furthermore, the preference for Mg doping in the Co site (3b) rather than in the Li site (3a) in the LCO framework is systematically revealed, and a clear understanding of Mg doping that suppresses the monoclinic phase transition is discussed in detail.
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