Lithium, the lightest and most electronegative metallic element, has long been considered the ultimate choice as a battery anode for mobile, as well as in some stationary applications. The high ...electronegativity of Li is, however, a double-edged sword-it facilitates a large operating voltage when paired with essentially any cathode, promising a high cell-level energy density. It is also synonymous with a high chemical reactivity and low reduction potential. The interfaces a Li metal anode forms with any other material (liquid or solid) in an electrochemical cell are therefore always mediated by one or more products of its chemical or electrochemical reactions with that material. The physical, crystallographic, mechanical, electrochemical, and transport properties of the resultant new material phases (
interphases
) regulate all interfacial processes at a Li metal anode, including electrodeposition during battery recharge. This Review takes recent efforts aimed at manipulating the structure, composition, and physical properties of the solid electrolyte interphase (SEI) formed on an Li anode as a point of departure to discuss the structural, electrokinetic, and electrochemical requirements for achieving high anode reversibility. An important conclusion is that while recent reports showing significant advances in the achievement of highly reversible Li anodes,
e.g.
as measured by the coulombic efficiency (CE), raise prospects for as significant progress towards commercially relevant Li metal batteries, the plateauing of achievable CE values to around 99 ± 0.5% apparent from a comprehensive analysis of the literature is problematic because CE values of at least 99.7%, and preferably >99.9% are required for Li metal cells to live up to the potential for higher energy density batteries offered by the Li metal anode. On this basis, we discuss promising approaches for creating purpose-built interphases on Li, as well as for fabricating advanced Li electrode architectures for regulating Li electrodeposition morphology and crystallinity. Considering the large number of physical and chemical factors involved in achieving fine control of Li electrodeposition, we believe that achievement of the remaining ∼0.5% in anode reversibility will require fresh approaches, perhaps borrowed from other fields. We offer perspectives on both current and new strategies for achieving such Li anodes with the specific aim of engaging established contributors and newcomers to the field in the search for scalable solutions.
Rational approaches for achieving fine control of the electrodeposition morphology of Li are required to create commercially-relevant rechargeable Li metal batteries.
Aqueous zinc batteries are attracting interest because of their potential for cost-effective and safe electricity storage. However, metallic zinc exhibits only moderate reversibility in aqueous ...electrolytes. To circumvent this issue, we study aqueous Zn batteries able to form nanometric interphases at the Zn metal/liquid electrolyte interface, composed of an ion-oligomer complex. In Zn||Zn symmetric cell studies, we report highly reversible cycling at high current densities and capacities (e.g., 160 mA cm
; 2.6 mAh cm
). By means of quartz-crystal microbalance, nuclear magnetic resonance, and voltammetry measurements we show that the interphase film exists in a dynamic equilibrium with oligomers dissolved in the electrolyte. The interphase strategy is applied to aqueous Zn||I
and Zn||MnO
cells that are charged/discharged for 12,000 cycles and 1000 cycles, respectively, at a current density of 160 mA cm
and capacity of approximately 0.85 mAh cm
. Finally, we demonstrate that Zn||I
-carbon pouch cells (9 cm
area) cycle stably and deliver a specific energy of 151 Wh/kg (based on the total mass of active materials in the electrode) at a charge current density of 56 mA cm
.
Understanding cation (H+, Li+, Na+, Al3+, etc.) intercalation/de‐intercalation chemistry in transition metal compounds is crucial for the design of cathode materials in aqueous electrochemical cells. ...Here we report that orthorhombic vanadium oxides (V2O5) supports highly reversible proton intercalation/de‐intercalation reactions in aqueous media, enabling aluminum electrochemical cells with extended cycle life. Empirical analyses using vibrational and x‐ray spectroscopy are complemented with theoretical analysis of the electrostatic potential to establish how and why protons intercalate in V2O5 in aqueous media. We show further that cathode coatings composed of cation selective membranes provide a straightforward method for enhancing cathode reversibility by preventing anion cross‐over in aqueous electrolytes. Our work sheds light on the design of cation transport requirements for high‐energy reversible cathodes in aqueous electrochemical cells.
Made‐to‐last: Highly reversible proton intercalation/de‐intercalation reactions in vanadium oxides (V2O5) enable aqueous aluminum batteries with extended cycle life. The composition and pH of the electrolyte are reported to control the selectivity of H+ intercalation in V2O5 in electrolytes containing other cations.
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The propensity of metals to form irregular and nonplanar electrodeposits at liquid-solid interfaces has emerged as a fundamental barrier to high-energy, rechargeable batteries that use metal anodes. ...We report an epitaxial mechanism to regulate nucleation, growth, and reversibility of metal anodes. The crystallographic, surface texturing, and electrochemical criteria for reversible epitaxial electrodeposition of metals are defined and their effectiveness demonstrated by using zinc (Zn), a safe, low-cost, and energy-dense battery anode material. Graphene, with a low lattice mismatch for Zn, is shown to be effective in driving deposition of Zn with a locked crystallographic orientation relation. The resultant epitaxial Zn anodes achieve exceptional reversibility over thousands of cycles at moderate and high rates. Reversible electrochemical epitaxy of metals provides a general pathway toward energy-dense batteries with high reversibility.
Abstract
Lithium metal is a promising anode for energy-dense batteries but is hindered by poor reversibility caused by continuous chemical and electrochemical degradation. Here we find that by ...increasing the Li plating capacity to high values (
e.g
., 10–50 mAh cm
−2
), Li deposits undergo a morphological transition to produce dense structures, composed of large grains with dominantly (110)
Li
crystallographic facets. The resultant Li metal electrodes manifest fast kinetics for lithium stripping/plating processes with higher exchange current density, but simultaneously exhibit elevated electrochemical stability towards the electrolyte. Detailed analysis of these findings reveal that parasitic electrochemical reactions are the major reason for poor Li reversibility, and that the degradation rate from parasitic electroreduction of electrolyte components is about an order of magnitude faster than from chemical reactions. The high-capacity Li electrodes provide a straightforward strategy for interrogating the solid electrolyte interphase (SEI) on Li —with unprecedented, high signal to noise. We find that an inorganic rich SEI is formed and is primarily concentrated around the edges of lithium particles. Our findings provide straightforward, but powerful approaches for enhancing the reversibility of Li and for fundamental studies of the interphases formed in liquid and solid-state electrolytes using readily accessible analytical tools.
This paper reports facile synthesis of nitrogen‐doped mesoporous carbon nanospheres (MCNSs) with average diameters of around 300 nm and well‐controlled pore sizes ranging from 8 to 38 nm, by ...employing polystyrene‐b‐poly(ethylene oxide) (PS‐b‐PEO) diblocks with different PS block lengths as the soft templates and dopamine as the carbon‐rich precursor. For the first time, a linear equation is achieved for the quantitative control of the average pore size of MCNSs by simply adjusting a block length of diblock copolymer. The resultant MCNSs possess high surface areas of up to 450 m2 g−1 and nitrogen doping contents of up to ≈3 wt%. As electrode materials of supercapacitors, the MCNSs exhibit excellent electrochemical performance with high specific capacitances of up to 350 F g−1 at 0.1 A g−1, superior rate capability, and cycling stability. Interestingly, the specific capacitance of the MCNSs reduces linearly with increasing pore size, whereas the normalized capacitance by specific surface area remains invariable. This represents a new spectrum of the relationship between electrochemical capacitance and pore size (>5 nm) for porous carbons, which makes a complement to the existing spectra focusing on pore diameters of <5 nm.
A simple linear equation for the quantitative control of the average pore size of mesoporous carbon nanospheres by simply adjusting a block length of diblock copolymer, and also affords a new spectrum of the relationship between electrochemical capacitance and pore size for porous carbons.
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As a kind of natural disasters, geological hazards pose serious threats to the ecological security and socio-economic development of human society. Evaluating the sensitivity of regional geological ...hazards is essential for making disaster-preventing/mitigating strategies and land use plans. Based on multisource remote sensing data, this study evaluates the geological hazard sensitivity in Liaoning Province by using the method of spatial principal component analysis and spatial autocorrelation finding that such sensitivity is generally moderate, with an average value of 5.25, and is mainly concentrated in three levels: Mild sensitivity, moderate sensitivity and insensitivity, accounting for more than 67% of the total area. Liaodong Mountain Area and Liaoxi Hilly Area are found with the highest sensitivity of geological hazards, showcasing obvious spatial differences and aggregations, mainly because these areas have large terrain fluctuations, poor stability of rock and soil bodies, and strong erosion by precipitation. The main factors affecting the sensitivity of geological hazards include land use mode, elevation, slope, and lithology. Among them, the land use mode has the highest contribution rate to the first principal component, reaching 0.86. This study provides a theoretical reference for the prevention and control over geological hazards and the protection of ecological security in Liaoning Province.
Metals use a chemotaxis-like process to overcome diffusion limitations and prevent dendritic electrodeposition in batteries.
The propensity of metal anodes of contemporary interest (e.g., Li, Al, Na, ...and Zn) to form non-planar, dendritic morphologies during battery charging is a fundamental barrier to achievement of full reversibility. We experimentally investigate the origins of dendritic electrodeposition of Zn, Cu, and Li in a three-electrode electrochemical cell bounded at one end by a rotating disc electrode. We find that the classical picture of ion depletion–induced growth of dendrites is valid in dilute electrolytes but is essentially irrelevant in the concentrated (≥1 M) electrolytes typically used in rechargeable batteries. Using Zn as an example, we find that ion depletion at the mass transport limit may be overcome by spontaneous reorientation of Zn crystallites from orientations parallel to the electrode surface to dominantly homeotropic orientations, which appear to facilitate contact with cations outside the depletion layer. This chemotaxis-like process causes obvious texturing and increases the porosity of metal electrodeposits.
•Advanced aberration-corrected TEM has been applied to investigate the precipitation in Mg-Gd binary alloy.•The growth of β′ precipitates at the early stage follows y (nm)=1.53x−2.68 (nm).•The ...long-range diffusion of Gd solutes prefers to occur along <101¯0>Mg directions and protrusions are formed.
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In the present study, nanoscale precipitation and phase growth in Mg-15Gd(wt%) binary alloy are comprehensively studied by atomic-resolution high angle annular dark field - scanning transmission electron microscopy (HAADF-STEM). Various nanoscale precipitate structures, including βH, β′, βT′, βM and β′′-like structure, assembled by the “basic unit” as building block, are observed, reconstructed and discussed in detail. In the early stage of precipitation, the precipitate growth basically follows y (nm)=1.53x−2.68 (nm) and protrusions start to grow when the size of a precipitate reaches a threshold value. Long-range diffusion of Gd solute preferentially proceeds along <101¯0>Mg directions and protrusions are formed. A large number of fine β′ precipitates exist and act as the key strengthening structures. The formation of precipitate-free zones in the over-age condition is attributed to the intertwining of precipitates.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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