59 research outputs found
A framework for integrating supply chain, environmental, and social justice factors during early stationary battery research
The transition to a decarbonized economy will drive dramatically higher demand for energy storage, along with technological diversification. To avoid mistakes of the past, the supply chain implications and environmental and social justice (ESJ) impacts of new battery technologies should be considered early during technological development. We propose herein a systematic framework for analyzing these impacts for new stationary battery technologies and illustrate the framework with a case study. The goal is to promote future development of technologies with secure supply chains and favorable ESJ profiles to avoid expensive corrective actions after substantial resources have been invested. This framework should be a useful tool for public and private researchers and sponsors who want to ensure that supply chain and ESJ concerns are considered and integrated as part of decision making throughout the research and development process
Visualization of lithium-ion transport and phase evolution within and between manganese oxide nanorods.
Multiple lithium-ion transport pathways and local phase changes upon lithiation in silver hollandite are revealed via in situ microscopy including electron diffraction, imaging and spectroscopy, coupled with density functional theory and phase field calculations. We report unexpected inter-nanorod lithium-ion transport, where the reaction fronts and kinetics are maintained within the neighbouring nanorod. Notably, this is the first time-resolved visualization of lithium-ion transport within and between individual nanorods, where the impact of oxygen deficiencies is delineated. Initially, fast lithium-ion transport is observed along the long axis with small net volume change, resulting in two lithiated silver hollandite phases distinguishable by orthorhombic distortion. Subsequently, a slower reaction front is observed, with formation of polyphase lithiated silver hollandite and face-centred-cubic silver metal with substantial volume expansion. These results indicate lithium-ion transport is not confined within a single nanorod and may provide a paradigm shift for one-dimensional tunnelled materials, particularly towards achieving high-rate capability
Discharge, Relaxation, and Charge Model for the Lithium Trivanadate Electrode: Reactions, Phase Change, and Transport
The electrochemical behavior of lithium trivanadate (LiV3O8) during lithiation, delithiation, and voltage recovery experiments is simulated using a crystal-scale model that accounts for solid-state diffusion, charge-transfer kinetics, and phase transformations. The kinetic expression for phase change was modeled using an approach inspired by the Avrami formulation for nucleation and growth. Numerical results indicate that the solid-state diffusion coefficient of lithium in LiV3O8 is ∼10−13 cm2 s−1 and the equilibrium compositions in the two phase region (∼2.5 V) are Li2.5V3O8:Li4V3O8. Agreement between the simulated and experimental results is excellent. Relative to the lithiation curves, the experimental delithiation curves show significantly less overpotential at low levels of lithiation (end of charge). Simulations are only able to capture this result by assuming that the solid-state mass-transfer resistance is less during delithiation. The proposed rationale for this difference is that the (100) face is inactive during lithiation, but active during delithiation. Finally, by assuming non-instantaneous phase-change kinetics, estimates are made for the overpotential due to imperfect phase change (supersaturation)
Modeling the Mesoscale Transport of Lithium-Magnetite Electrodes Using Insight from Discharge and Voltage Recovery Experiments
A multi-scale mathematical model, which accounts for mass transport on the crystal and agglomerate length-scales, is used to investigate the electrochemical performance of lithium-magnetite electrochemical cells. Experimental discharge and voltage recovery data are compared to three sets of simulations, which incorporate crystal-only, agglomerate-only, or multi-scale transport effects. Mass transport diffusion coefficients are determined by fitting the simulated voltage recovery times to experimental data. In addition, a further extension of the multi-scale model is proposed which accounts for the impact of agglomerate size distributions on electrochemical performance. The results of the study indicate that, depending on the crystal size, the low utilization of the active material is caused by transport limitations on the agglomerate and/or crystal length-scales. For electrodes composed of small crystals (6 and 8 nm diameters), it is concluded that the transport limitations in the agglomerate are primarily responsible for the long voltage recovery times and low utilization of the active mass. In the electrodes composed of large crystals (32 nm diameter), the slow voltage recovery is attributed to transport limitations on both the agglomerate and crystal length-scales
The Sabatier principle for Battery Anodes: Chemical Kinetics and Reversible Electrodeposition at Heterointerfaces
How surface chemistry influences reactions occurring thereupon has been a
long-standing question of broad scientific and technological interest for
centuries. Recently, it has re-emerged as a critical question in a
subdiscipline of chemistry - electrochemistry at heterointerphases, where the
answers have implications for both how, and in what forms, humanity stores the
rising quantities of renewable electric power generated from solar and wind
installations world-wide. Here we consider the relation between the surface
chemistry at such interphases and the reversibility of electrochemical
transformations at a rechargeable battery electrode. Conventional wisdom holds
that stronger chemical interaction between the metal deposits and electrode
promotes reversibility. We report instead that a moderate strength of chemical
interaction between the deposit and the substrate, neither too weak nor too
strong, enables highest reversibility and stability of the plating/stripping
redox processes at a battery anode. Analogous to the empirical Sabatier
principle for chemical heterogeneous catalysis, our finding arises from the
confluence of competing processes - one driven by electrochemistry and the
other by chemical alloying. Based on experimental evaluation of metal
plating/stripping systems in battery anodes of contemporary interest, we show
that such knowledge provides a powerful tool for designing key materials in
highly reversible electrochemical energy storage technologies based on
earth-abundant, low-cost metals.Comment: 64 pages. Initially submitted on March 16th, 2021; revised version
submitted on November 14th, 2021 to the same Journa
AgxVOPO4: A demonstration of the dependence of battery-related electrochemical properties of silver vanadium phosphorous oxides on Ag/V ratios
Microwave-Assisted Synthesis of Silver Vanadium Phosphorus Oxide, Ag<sub>2</sub>VO<sub>2</sub>PO<sub>4</sub>: Crystallite Size Control and Impact on Electrochemistry
Silver vanadium phosphorus oxide,
Ag<sub>2</sub>VO<sub>2</sub>PO<sub>4</sub>, is a promising cathode
material for Li batteries due in
part to its large capacity and high current capability. Herein, a
new synthesis of Ag<sub>2</sub>VO<sub>2</sub>PO<sub>4</sub> based
on microwave heating is presented, where the reaction time is reduced
by approximately 100× relative to other reported methods, and
the crystallite size is controlled via synthesis temperature, showing
a linear correlation of crystallite size with temperature. Notably,
under galvanostatic reduction, the Ag<sub>2</sub>VO<sub>2</sub>PO<sub>4</sub> sample with the smallest crystallite size delivers the highest
capacity and shows the highest loaded voltage. Further, pulse discharge
tests show a significant resistance decrease during the initial discharge
coincident with the formation of Ag metal. Thus, the magnitude of
the resistance decrease observed during pulse tests depends on the
Ag<sub>2</sub>VO<sub>2</sub>PO<sub>4</sub> crystallite size, with
the largest resistance decrease observed for the smallest crystallite
size. Additional electrochemical measurements indicate a quasi-reversible
redox reaction involving Li<sup>+</sup> insertion/deinsertion, with
capacity fade due to structural changes associated with the discharge/charge
process. In summary, this work demonstrates a faster synthetic approach
for bimetallic polyanionic materials which also provides the opportunity
for tuning of electrochemical properties through control of material
physical properties such as crystallite size
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