An official website of the United States government
Abstract Intercalation pseudocapacitance has emerged as a promising energy storage mechanism that combines the energy density of intercalation materials with the power density of capacitors. Niobium pentoxide was the first material described as exhibiting intercalation pseudocapacitance. The electrochemical kinetics for charging/discharging this material are surface‐limited for a wide range of conditions despite intercalation via diffusion. Investigations of niobium pentoxide nanostructures are diverse and numerous; however, none have yet compared performance while adjusting a single architectural parameter at a time. Such a comparative approach reduces the reliance on models and the associated assumptions when seeking nanostructure–property relationships. Here, a tailored isomorphic series of niobium pentoxide nanostructures with constant pore size and precision tailored wall thickness is examined. The sweep rate at which niobium pentoxide transitions from being surface‐limited to being diffusion‐limited is shown to depend sensitively upon the nanoscale dimensions of the niobium pentoxide architecture. Subsequent experiments probing the independent effects of electrolyte concentration and film thickness unambiguously identify solid‐state lithium diffusion as the dominant diffusion constraint even in samples with just 48.5–67.0 nm thick walls. The resulting architectural dependencies from this type of investigation are critical to enable energy‐dense nanostructures that are tailored to deliver a specific power density.
more »
« less
Understanding Rapid Intercalation Materials One Parameter at a Time
Abstract Demand for fast, energy‐dense storage drives the research into nanoscale intercalation materials. Nanomaterials accelerate kinetics and can modify reaction path thermodynamics, intercalant solubility, and reversibility. The discovery of intercalation pseudocapacitance has opened questions about their fundamental operating principles. For example, are their capacitor‐like current responses caused by storing energy in special near‐surface regions or rather is this response due to normal intercalation limited by a slower faradaic surface‐reaction? This review highlights emerging methods combining tailored nanomaterials with the process of elimination to disambiguate cause‐and‐effect at the nanoscale. This method is applied to multiple intercalation pseudocapacitive materials showing that the timescales exhibiting surface‐limited kinetics depended on the total intercalation length scale. These trends are inconsistent with the near‐surface perspective. A revised current‐model without assuming special near‐surface storage fits experimental data better across wide timescales. This model, combined with tailored nanomaterials and the process of elimination, can isolate material‐specific effects such as how amorphization/defect‐tailoring modifies both insertion and diffusion kinetics. Avenues for both faster intercalation pseudocapacitance and increased energy density are discussed. A relaxation time argument is suggested to explain the continuum between battery‐like and pseudocapacitive behaviors. Future directions include synthetic methods emphasizing tailored defects and analytical methods that minimize assumptions.
more »
« less
- Award ID(s):
- 1752615
- PAR ID:
- 10446173
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Functional Materials
- Volume:
- 32
- Issue:
- 31
- ISSN:
- 1616-301X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract Pseudocapacitors promise to fill the gap between traditional capacitors and batteries by delivering reasonable energy densities and power densities. In this work, pseudocapacitive charge storage properties are demonstrated for two isostructural oxides, Sr2LaFeMnO7and Sr2LaCoMnO7. These materials comprise spatially separated bilayer stacks of corner sharing BO6units (B=Fe, Co or Mn). The spaces between stacks accommodate the lanthanum and strontium ions, and the remaining empty spaces are available for oxide ion intercalation, leading to pseudocapacitive charge storage. Iodometric titrations indicate that these materials do not have oxygen‐vacancies. Therefore, the oxide ion intercalation becomes possible due to their structural features and the availability of interstitial sites between the octahedral stacks. Electrochemical studies reveal that both materials show promising energy density and power density values. Further experiments through fabrication of a symmetric two‐electrode cell indicate that these materials retain their pseudocapacitive performance over hundreds of galvanostatic charge‐discharge cycles, with little degradation even after 1000 cycles.more » « less
-
Herein, the effect of structure on pseudocapacitive properties in alkaline conditions is demonstrated through the investigation of isoelectronic oxides Ca2LaMn2O7and Sr2LaMn2O7, where the difference in ionic radii of Ca2+and Sr2+leads to a change in structure and lattice symmetry, resulting in an orthorhombicCmcmstructure for the former and a tetragonalI4/mmmstructure for the latter. While calcium and strontium do not make a direct contribution to the near‐surface faradaic processes that are essential to the pseudocapacitive properties, their effect on the structure leads to a change in the oxygen intercalation process and the associated pseudocapacitive energy storage. It is shown that Sr2LaMn2O7has a significantly greater specific capacitance than Ca2LaMn2O7. In addition, the former shows a considerably higher‐energy density compared to the latter. Furthermore, these materials show highly stable energy‐storage properties, and retain their specific capacitance over 10 000 cycles of charge–discharge in a symmetric pseudocapacitive cell. Importantly, these findings show the structure–property relationships, where a change in the structure and lattice symmetry can result in a significant change in pseudocapacitive charge–discharge properties in isoelectronic systems.more » « less
-
The ever-increasing global energy demand necessitates the development of efficient, sustainable, and high-performance energy storage systems. Nanotechnology, through the manipulation of materials at the nanoscale, offers significant potential for enhancing the performance of energy storage devices due to unique properties such as increased surface area and improved conductivity. This review paper investigates the crucial role of nanotechnology in advancing energy storage technologies, with a specific focus on capacitors and batteries, including lithium-ion, sodium–sulfur, and redox flow. We explore the diverse applications of nanomaterials in batteries, encompassing electrode materials (e.g., carbon nanotubes, metal oxides), electrolytes, and separators. To address challenges like interfacial side reactions, advanced nanostructured materials are being developed. We also delve into various manufacturing methods for nanomaterials, including top–down (e.g., ball milling), bottom–up (e.g., chemical vapor deposition), and hybrid approaches, highlighting their scalability considerations. While challenges such as cost-effectiveness and environmental concerns persist, the outlook for nanotechnology in energy storage remains promising, with emerging trends including solid-state batteries and the integration of nanomaterials with artificial intelligence for optimized energy storage.more » « less
-
Sodium- and potassium-ion batteries are one of the most promising electrical energy storage devices at low cost, but their inferior rate and capacity have hampered broader applications such as electric vehicles and grids. Carbon nanomaterials have been demonstrated to have ultrafast surface-dominated ion uptake to drastically increase the rate and capacity, but trial-and-error approaches are usually used to find desired anode materials from numerous candidates. Here, we developed guiding principles to rationally screen pseudocapacitive anodes from numerous candidate carbon materials to create ultrafast Na- and K-ion batteries. The transition from pseudocapacitive to metal-battery mechanisms on heteroatom-doped graphene in charging process was revealed by the density functional theory methods. The results show that the graphene substrate can guide the preferential growth of K and Na along graphene plane, which inhibits dendrite development effectively in the batteries. An intrinsic descriptor is discovered to establish a volcano-shaped relationship that correlates the capacity with the intrinsic physical qualities of the doping structures, from which the best anode materials could be predicted. The predictions are in good agreement with the experimental results. The strategies for enhancing both the power and energy densities are proposed based on the predictions and experiments for the batteries.more » « less
