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.
Conspectus Future advances in energy storage systems rely on identification of appropriate target materials and deliberate synthesis of the target materials with control of their physiochemical ...properties in order to disentangle the contributions of distinct properties to the functional electrochemistry. This goal demands systematic inquiry using model materials that provide the opportunity for significant synthetic versatility and control. Ideally, a material family that enables direct manipulation of characteristics including composition, defects, and crystallite size while remaining within the defined structural framework would be necessary. Accomplishing this through direct synthetic methods is desirable to minimize the complicating effects of secondary processing. The structural motif most frequently used for insertion type electrodes is based on layered type structures where ion diffusion in two dimensions can be envisioned. However, lattice expansion and contraction associated with the ion movement and electron transfer as a result of repeated charge and discharge cycling can result in structural degradation and amorphization with accompanying loss of capacity. In contrast, tunnel type structures embody a more rigid framework where the inherent structural design can accommodate the presence of cations and often multiple cations. Of specific interest are manganese oxides as they can exhibit a tunneled structure, termed α-MnO2, and are an important class of nanomaterial in the fields of catalysis, adsorption–separation, and ion-exchange. The α-MnO2 structure has one-dimensional 2 × 2 tunnels formed by corner and edge sharing manganese octahedral MnO6 units and can be readily substituted in the central tunnel by a variety of cations of varying size. Importantly, α-MnO2 materials possess a rich chemistry with significant synthetic versatility allowing deliberate synthetic control of structure, composition, crystallite size, and defect content. This Account considers the investigation of α-MnO2 tunnel type structures and their electrochemistry. Examination of the reported findings on this material family demonstrates that multiple physiochemical properties influence the electrochemistry. The retention of the parent structure during charge and discharge cycling, the material composition including the identity and content of the central cation, the surface condition including oxygen vacancies, and crystallite size have all been demonstrated to impact electrochemical function. The selection of the α-MnO2 family of materials as a model system and the ability to control the variables associated with the structural family affirm that full investigation of the mechanisms related to active materials in an electrochemical system demands concerted efforts in synthetic material property control and multimodal characterization, combined with theory and modeling. This then enables more complete understanding of the factors that must be controlled to achieve consistent and desirable outcomes.
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IJS, KILJ, NUK, PNG, UL, UM
The global shift to electricity as the main energy carrier will require innovation in electrochemical energy storage (EES). EES systems are the key to the “electron energy economy,” minimizing losses ...and increasing reliability between energy supply and demand. However, steep challenges such as cost, cycle/calendar life, energy density, material availability, and safety limit widespread adoption of batteries for large-scale grid and vehicle applications. Battery innovation that meets today’s challenges will require new chemistries, which can originate from understanding charge transport phenomena at multiple time and length scales. The advancement of
operando
characterization can expedite this progress as changes can be observed during battery function. This article highlights progress in bulk and interfacial
operando
characterization of batteries. Specifically, a case study involving Fe
3
O
4
is provided demonstrating that combining X-ray absorption spectroscopy and isothermal microcalorimetry can provide real-time characterization of productive faradaic redox processes and parasitic interfacial reactions during (de)lithiation.
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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
Vanadium dioxides exist as a variety of polymorphs, each with differing structural and electrochemical capabilities. The monoclinic to rutile transition is an interesting system for study as the ...transition temperature is easily accessible at moderate temperature and corresponds to an increase in electrical conductivity by 2 orders of magnitude. The transition from monoclinic to rutile is characterized structurally herein using synchrotron-based X-ray diffraction and related to lithium-ion electrochemistry using electrochemical impedance spectroscopy and intermittent pulsatile galvanostatic discharge tests. The experimental results indicate a decrease in ohmic resistance for lithium-based cells tested under higher temperatures. Complementary density functional theory calculations described the experimentally measured intercalation voltages and identified a possible Li-induced Li x VO2(M) to Li x VO2(R) phase transition during the discharging process rationalizing the favorable impact on the function of a lithium-based electrochemical cell. To our knowledge, this is the first observation of the metal–insulator transition of VO2 in a full electrochemical cell.
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IJS, KILJ, NUK, PNG, UL, UM
Future advances in energy storage systems rely on identification of appropriate target materials and deliberate synthesis of the target materials with control of their physiochemical properties in ...order to disentangle the contributions of distinct properties to the functional electrochemistry. This goal demands systematic inquiry using model materials that provide the opportunity for significant synthetic versatility and control. Ideally, a material family that enables direct manipulation of characteristics including composition, defects, and crystallite size while remaining within the defined structural framework would be necessary. Accomplishing this through direct synthetic methods is desirable to minimize the complicating effects of secondary processing. The structural motif most frequently used for insertion type electrodes is based on layered type structures where ion diffusion in two dimensions can be envisioned. However, lattice expansion and contraction associated with the ion movement and electron transfer as a result of repeated charge and discharge cycling can result in structural degradation and amorphization with accompanying loss of capacity. In contrast, tunnel type structures embody a more rigid framework where the inherent structural design can accommodate the presence of cations and often multiple cations. Of specific interest are manganese oxides as they can exhibit a tunneled structure, termed α-MnO
, and are an important class of nanomaterial in the fields of catalysis, adsorption-separation, and ion-exchange. The α-MnO
structure has one-dimensional 2 × 2 tunnels formed by corner and edge sharing manganese octahedral MnO
units and can be readily substituted in the central tunnel by a variety of cations of varying size. Importantly, α-MnO
materials possess a rich chemistry with significant synthetic versatility allowing deliberate synthetic control of structure, composition, crystallite size, and defect content. This Account considers the investigation of α-MnO
tunnel type structures and their electrochemistry. Examination of the reported findings on this material family demonstrates that multiple physiochemical properties influence the electrochemistry. The retention of the parent structure during charge and discharge cycling, the material composition including the identity and content of the central cation, the surface condition including oxygen vacancies, and crystallite size have all been demonstrated to impact electrochemical function. The selection of the α-MnO
family of materials as a model system and the ability to control the variables associated with the structural family affirm that full investigation of the mechanisms related to active materials in an electrochemical system demands concerted efforts in synthetic material property control and multimodal characterization, combined with theory and modeling. This then enables more complete understanding of the factors that must be controlled to achieve consistent and desirable outcomes.
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Available for:
IJS, KILJ, NUK, PNG, UL, UM
Battery electrodes are complex mesoscale systems comprising an active material, conductive agent, current collector, and polymeric binder. Although significant research on composite electrode ...materials for Li-ion batteries focuses on the design, synthesis, and characterization of the active particles, the binder component has been shown to critically impact stability and ensure electrode integrity during volume changes induced upon cycling. Herein, we explore the ability of water-soluble, carboxylated conjugated polymer binders to aid in electron and ion transport in magnetite-based anodes. Specifically, poly3-(potassium-4-butanoate)thiophene (PPBT) and a potassium carboxylate functionalized 3,4-propylenedioxythiophene (ProDOT)-based copolymer (WS-PE2) were investigated and evaluated against the control, potassium salt form of poly(acrylic acid) (PAA-K). When used in conjunction with a polyethylene glycol (PEG) surface coating for the magnetite active material, PPBT provided for overall improved electrode performance as a result of more favorable intermolecular interactions between the composite constituents. The ProDOT-based copolymer WS-PE2 exhibited comparable cycling performance to PPBT, whereas PAA-K and PPBT were similar with respect to rate capability. This investigation compares and contrasts a series of carboxylated polymers to elucidate the roles of different functional groups and identify materials chemistry-based structural parameters that can be manipulated to assist overall electrochemical performance of composite Li-ion battery anodes.
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IJS, KILJ, NUK, PNG, UL, UM
Rational design of battery systems with specific performance characteristics are needed to meet the growing, diverse needs of energy storage as batteries penetrate a range of sectors from automobiles ...to consumer electronics, among others. Here, we surface modified magnetite particles with distinct molecular entities containing different electronic and ionic conductivities and investigated how the local surface environment affected key battery characteristics such as capacity retention, rate capability, and electrode impedance. Herein, direct covalent attachment of poly 3-(4-carboxypropyl)thiophene onto magnetite nanoparticles via a Fischer esterification scheme was shown to create robust anodes with low charge transfer resistances, excellent charge capacity retention at 0.3 C, and robust charge capabilities/specific capacities. The functionalization strategies used here rely on manipulating the native hydroxide layer of the active material, and thus can be applied to various conversion-type electrode materials. This work contributes to the growing toolset of chemical techniques to modify active materials to create battery systems with specific performance characteristics.
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Electron transfer and ion transport occurs over multiple-length scales ranging from the atomic to mesoscale within battery materials and electrodes. Micro-X-ray fluorescence (µ-XRF) is an important ...characterization tool as it can resolve structural, compositional, and redox information while providing insight into the spatial distribution of an electroactive material. In this work, µ-XRF mapping is used to probe the distribution of iron within thin planar slurry-based and thick porous carbon nanotube (CNT)-based magnetite (Fe
3
O
4
) electrodes. Notably, the porous CNT-based electrode showed homogenous distribution of Fe within the electrode whereas the planar electrode demonstrated distinct Fe aggregates. This information was used to rationalize the electrochemistry observed by cyclic voltammetry and galvanostatic cycling. The thick porous electrode delivered 215% more capacity per gram of magnetite during the first discharge, consistent with increased electrode homogeneity enabling effective ion access and electron transfer.
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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
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