Designing better electrolytes Meng, Y Shirley; Srinivasan, Venkat; Xu, Kang
Science (American Association for the Advancement of Science),
12/2022, Volume:
378, Issue:
6624
Journal Article
Peer reviewed
Electrolytes and the associated interphases constitute the critical components to support the emerging battery chemistries that promise tantalizing energy but involve drastic phase and structure ...complications. Designing better electrolytes and interphases holds the key to the success of these batteries. As the only component that interfaces with every other component in the device, an electrolyte must satisfy multiple criteria simultaneously. These include transporting ions while insulating electrons between the electrodes and maintaining stability against electrodes of extreme chemical natures: the strongly oxidative cathode and the strongly reductive anode. In most advanced batteries, the two electrodes operate at potentials far beyond the thermodynamic stability limits of electrolytes, so the stability therein has to be realized kinetically through an interphase formed from the sacrificial reactions between electrolyte and electrodes.
Electrochemical capacitors and lithium-ion batteries have seen little change in their electrolyte chemistry since their commercialization, which has limited improvements in device performance. ...Combining superior physical and chemical properties and a high dielectric-fluidity factor, the use of electrolytes based on solvent systems that exclusively use components that are typically gaseous under standard conditions show a wide potential window of stability and excellent performance over an extended temperature range. Electrochemical capacitors using difluoromethane show outstanding performance from -78° to +65°C, with an increased operation voltage. The use of fluoromethane shows a high coulombic efficiency of ~97% for cycling lithium metal anodes, together with good cyclability of a 4-volt lithium cobalt oxide cathode and operation as low as -60°C, with excellent capacity retention.
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The recent proliferation of renewable energy generation offers mankind hope, with regard to combatting global climate change. However, reaping the full benefits of these renewable energy sources ...requires the ability to store and distribute any renewable energy generated in a cost‐effective, safe, and sustainable manner. As such, sodium‐ion batteries (NIBs) have been touted as an attractive storage technology due to their elemental abundance, promising electrochemical performance and environmentally benign nature. Moreover, new developments in sodium battery materials have enabled the adoption of high‐voltage and high‐capacity cathodes free of rare earth elements such as Li, Co, Ni, offering pathways for low‐cost NIBs that match their lithium counterparts in energy density while serving the needs for large‐scale grid energy storage. In this essay, a range of battery chemistries are discussed alongside their respective battery properties while keeping metrics for grid storage in mind. Matters regarding materials and full cell cost, supply chain and environmental sustainability are discussed, with emphasis on the need to eliminate several elements (Li, Ni, Co) from NIBs. Future directions for research are also discussed, along with potential strategies to overcome obstacles in battery safety and sustainable recyclability.
Sodium‐ion batteries (NIBs) are touted as an attractive grid storage technology due to their elemental abundance, promising electrochemical performance and environmentally benign nature. Herein, sodium cathodes are analyzed with respect to performance, full cell costs, and environmental sustainability. Future directions for NIB full cell research and potential strategies to overcome obstacles in battery safety and sustainable recyclability are discussed.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Thermoregulation has substantial implications for energy consumption and human comfort and health. However, cooling technology has remained largely unchanged for more than a century and still relies ...on cooling the entire space regardless of the number of occupants. Personalized thermoregulation by thermoelectric devices (TEDs) can markedly reduce the cooling volume and meet individual cooling needs but has yet to be realized because of the lack of flexible TEDs with sustainable high cooling performance. Here, we demonstrate a wearable TED that can deliver more than 10°C cooling effect with a high coefficient of performance (COP > 1.5). Our TED is the first to achieve long-term active cooling with high flexibility, due to a novel design of double elastomer layers and high-ZT rigid TE pillars. Thermoregulation based on these devices may enable a shift from centralized cooling toward personalized cooling with the benefits of substantially lower energy consumption and improved human comfort.
According to the US Department of Energy’s Energy Infomation Administration (EIA) (International Energy Outlook 2017), world energy consumption will increase 28% between 2015 and 2040, rising from ...575 quadrillion Btu (∼606 quadrillion kJ) in 2015 to 736 quadrillion Btu (∼776 quadrillion kJ) in 2040. EIA predicts increases in consumption for all energy sources (excluding coal, which is estimated to remain flat)—fossil (petroleum and other liquids, natural gas), renewables (solar, wind, hydropower), and nuclear. Although renewables are the world’s fastest growing form of energy, fossil fuels are expected to continue to supply more than three-quarters of the energy used worldwide. Among the various fossil fuels, natural gas is the fastest growing, with a projected increase of 43% from 2015 to 2040. As the use of fossil fuels increases, the EIA projects world energy-related carbon dioxide emission to grow from ∼34 billion metric tons in 2015 to ∼40 billion metric tonnes in 2040 (an average 0.6% increase per year).
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Although layered lithium oxides have become the cathode of choice for state‐of‐the‐art Li‐ion batteries, substantial gaps remain between the practical and theoretical energy densities. With the aim ...of supporting efforts to close this gap, this work reviews the fundamental operating mechanisms and challenges of Li intercalation in layered oxides, contrasts how these challenges play out differently for different materials (with emphasis on Ni–Co–Al (NCA) and Ni–Mn–Co (NMC) alloys), and summarizes the extensive corpus of modifications and extensions to the layered lithium oxides. Particular emphasis is given to the fundamental mechanisms behind the operation and degradation of layered intercalation electrode materials as well as novel modifications and extensions, including Na‐ion and cation‐disordered materials.
Li intercalation in layered‐oxide cathodes involves a complex interplay between many thermodynamic and kinetic phenomena. This review summarizes the fundamental mechanisms and challenges, and how these play out for different layered‐oxide cathode materials. Special emphasis is given to Ni–Co–Al and Ni–Mn–Co alloys as well as novel modifications and extensions, including Na‐ion and cation‐disordered materials.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
During the current pandemic shutdown, everyone has had to make decisions—many of which haven't been easy. For the first time in my life, I experienced what were previously unthinkable—airplanes being ...grounded, cars being off the roads, all classes and meetings being held virtually. The surreal experience has propelled me to think more deeply about what I do and why it is so important to push forward with doing better materials science to enable breakthroughs in energy technologies and to ensure a robust supply chain of relevant materials for the world.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Deviation between thermodynamic and experimental voltages is one of the key issues in Li-ion conversion-type electrode materials; the factor that affects this phenomenon has not been understood well ...in spite of its importance. In this work, we combine first principles calculations and electrochemical experiments with characterization tools to probe the conversion reaction voltage of transition metal difluorides MF2（M = Fe, Ni, and Cu）. We find that the conversion reaction voltage is heavily dependent on the size of the metal nanoparticles generated. The surface energy of metal nanoparticles appears to penalize the reaction energy, which results in a lower voltage compared to the thermodynamic voltage of a bulk-phase reaction. Furthermore, we develop a reversible CuF2 electrode coated with NiO. Electron energy loss spectroscopy （EELS） elemental maps demonstrate that the lithiation process mostly occurs in the area of high NiO content. This suggests that NiO can be considered a suitable artificial solid electrolyte interphase that prevents direct contact between Cu nanoparticles and the electrolyte. Thus, it alleviates Cu dissolution into the electrolyte and improves the reversibility of CuF2.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The performance of many technologies, such as Li- and Na-ion batteries as well as some two-dimensional (2D) electronics, is dependent upon the reversibility of stacking-sequence-change phase ...transformations. However, the mechanisms by which such transformations lead to degradation are not well understood. This study explores lattice-invariant shear as a source of irreversibility in stacking-sequence changes, and through an analysis of crystal symmetry shows that common electrode materials (graphitic carbon, layered oxides, and layered sulfides) are generally susceptible to lattice-invariant shear. The resulting irreversible changes to microstructure upon cycling (“electrochemical creep”) could contribute to the degradation of the electrode and capacity fade.
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IJS, KILJ, NUK, PNG, UL, UM
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