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At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Suspension electrolyte with modified Li + solvation environment for lithium metal batteries

Designing a stable solid–electrolyte interphase on a Li anode is imperative to developing reliable Li metal batteries. In this work, we report a suspension electrolyte design that modifies the Li + solvation environment in liquid electrolytes and creates inorganic-rich solid–electrolyte interphases on Li. Li 2 O nanoparticles suspended in liquid electrolytes were investigated as a proof of concept. Through theoretical and empirical analyses of Li 2 O suspension electrolytes, the roles played by Li 2 O in the liquid electrolyte and solid–electrolyte interphases of the Li anode are elucidated. Also, the suspension electrolyte design is applied in conventional and state-of-the-art high-performance electrolytes to demonstrate its applicability. Based on electrochemical analyses, improved Coulombic efficiency (up to ~99.7%), reduced Li nucleation overpotential, stabilized Li interphases and prolonged cycle life of anode-free cells (~70 cycles at 80% of initial capacity) were achieved with the suspension electrolytes. We expect this design principle and our findings to be expanded into developing electrolytes and solid–electrolyte interphases for Li metal batteries.

25 ENERGY STORAGE↗
DOE OSTI2022

Nonsacrificial Additive for Tuning the Cathode–Electrolyte Interphase of Lithium-Ion Batteries

Solid–electrolyte interphases is essential for stable cycling of rechargeable batteries. The traditional approach for interphase design follows the decomposition of additives prior to the host electrolyte, which, as governed by the thermodynamic rule, however, inherently limits the viable additives. Here we report an alternative approach of using a nonsacrificial additive. This is exemplified by the localized high-concentration electrolytes, where the fluoroethylene carbonate (FEC) plays a nonsacrificial role for modifying the chemistry, structure, and formation mechanism of the cathode–electrolyte interphase (CEI) layers toward enhanced cycling stability. On the basis of ab initio molecular dynamics simulations, we further reveal that the unexpected activation of the otherwise inert species in the interphase formation is due to the FEC–Li + coordinated environment that altered the electronic states of reactants. In conclusion, the nonsacrificial additive on CEI formation opens up alternative avenues for the interphase design through the use of the commonly overlooked, anodically stable compounds.

25 ENERGY STORAGE↗
DOE OSTI2026

Aqueous electrolyte solutions with anion-bridged secondary solvation sheaths for highly efficient zinc metal batteries

Aqueous zinc metal batteries are low-cost electrochemical devices suitable for safe grid energy storage. However, water decomposition and Zn dendrite formation detrimentally affect their coulombic efficiency. Conventional aqueous electrolyte solutions, with a concentration around 1 M, are cost-effective and exhibit high bulk ionic conductivity but cannot form a stable solid electrolyte interphase. Water-in-salt and aqueous-organic hybrid electrolyte solutions can form robust solid electrolyte interphases, but they are not kinetically efficient and cost-effective. Here, to circumvent these issues, we design variously concentrated aqueous electrolyte solutions using several salts with different donor numbers to extend anion coordination into the secondary solvation sheath. We show that salt-derived anions with donor number > 18 enter the Zn2+ first solvation sheath, and ensure a strong binding energy between the Zn2+(H2O)5-anion nanometric clusters and water molecules in the secondary solvation sheath. In particular, 2 M aqueous electrolyte solutions containing fluorinated anions exhibit bulk ionic conductivities of 26-35 mS cm−1 at 25 °C and form a ZnF2-rich solid electrolyte interphase. When tested in Zn||NaV3O8·1.5H2O Swagelok cells, the best-performing electrolyte solution enables an average coulombic efficiency of 99.99% for 1,000 cycles at 1.5 mA cm−2, corresponding to an initial specific energy of 130 Wh kg−1 (based on the combined weight of the positive and negative electrodes).

25 ENERGY STORAGE↗
DOE OSTI2025

An Atomistic Study of Reactivity in Solid-State Electrolyte Interphase Formation for Li/Li7P3S11

Lithium metal batteries offer superior volumetric and gravimetric specific capacities compared to those based on traditional graphite anodes. Although advancements in solid-state electrolytes address safety concerns, challenges remain, particularly regarding interphase formation in lithium metal anodes. This work presents a computational framework based on high-throughput first-principles density functional theory and machine-learning interatomic potentials (MLIPs) including automated iterative, active learning to enable robust computational exploration of interphase formation between lithium metal anodes and an inorganic solid-state electrolyte. As a demonstration, we apply the framework to a Li/Li7P3S11 interface and find that it accurately identifies the experimentally observed, thermodynamically stable interphase products as well as their overall spatial arrangement within a heterogeneous, amorphous layered structure, with Li2S domains of nanocrystallinity. Our simulations show two stages, a fast and slow diffusion reaction regime, that corroborate the relative phase formation rate of Li x P, Li2S, and Li3P. Using the Onsager transport theory, we capture time-dependent ionic diffusion within the reacting interface, including cross-correlation effects. We found that cross-correlation effects between Li-P and P-S ionic motion significantly influence P-ion diffusion, making it highly sensitive to the local environment and potentially leading to "kinetic trapping" of Li-P phases. The passivation of the interface is shown as the ionic fluxes all approach zero, effectively halting interphase growth.

Diffusion↗
DOE OSTI2021

Corrosion of lithium metal anodes during calendar ageing and its microscopic origins

Rechargeable lithium (Li) metal batteries must have long cycle life and calendar life (retention of capacity during storage at open circuit). Particular emphasis has been placed on prolonging the cycle life of Li metal anodes, but calendar ageing is less understood. Here, we show that Li metal loses at least 2–3% of its capacity after only 24 hours of ageing, regardless of the electrolyte chemistry. These losses of capacity during calendar ageing also shorten the cycle life of Li metal batteries. Cryogenic transmission electron microscopy shows that chemical corrosion of Li and the continuous growth of the solid electrolyte interphase—a passivation film on Li—cause the loss of capacity. Electrolytes with long cycle life do not necessarily form a solid electrolyte interphase with more resistance to chemical corrosion, so functional electrolytes must simultaneously minimize the rate of solid electrolyte interphase growth and the surface area of electrodeposited Li metal.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Selective NMR observation of the SEI–metal interface by dynamic nuclear polarisation from lithium metal

While lithium metal represents the ultimate high-energy-density battery anode material, its use is limited by dendrite formation and associated safety risks, motivating studies of the solid–electrolyte interphase layer that forms on the lithium, which is key in controlling lithium metal deposition. Dynamic nuclear polarisation enhanced NMR can provide important structural information; however, typical exogenous dynamic nuclear polarisation experiments, in which organic radicals are added to the sample, require cryogenic sample cooling and are not selective for the interface between the metal and the solid–electrolyte interphase. Here we instead exploit the conduction electrons of lithium metal to achieve an order of magnitude hyperpolarisation at room temperature. We enhance the 7 Li, 1 H and 19 F NMR spectra of solid–electrolyte interphase species selectively, revealing their chemical nature and spatial distribution. These experiments pave the way for more ambitious room temperature in situ dynamic nuclear polarisation studies of batteries and the selective enhancement of metal–solid interfaces in a wider range of systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Understanding the Selective Deposition of Li Metal on Nonuniform Electrode Surfaces Using Atomic Force Microscopy

The use of lithium metal in secondary batteries has been impeded by its tendency to form dendrites: branching conductive structures of metal that can lead to capacity loss and, ultimately, internal shorts in the battery. Patterned electrodes, in addition to artificially increasing the current density of cells by increasing the surface area available for reaction, also generate a nonuniform electric field in the vicinity of the electrode surface. This nonuniform electric field, though rapidly screened by the electrolyte, can promote inhomogeneous deposition and Solid Electrolyte Interphase formation. As the consequence of these effects is not theoretically apparent since Solid Electrolyte Interphase volume and conductivity changes can, in principle, offset variations in local current density, we have performed experiments to examine the deposition of Li on nonuniform electrode surfaces using Atomic Force Microscopy. In this work, we measure the local variations in topography, SEI thickness, and composition, and discuss their implications for the formation of dendrites in Li metal.

25 ENERGY STORAGE↗
DOE OSTI2020

Tuning the Anode–Electrolyte Interface Chemistry for Garnet-Based Solid-State Li Metal Batteries

Lithium (Li) metal anode is a promising candidate for high energy density solid-state batteries. However, the interface issues, including large interfacial resistance and Li dendrite generation, have always frustrated the attempt to commercialize solid-state Li metal batteries (SSLBs). Here, we report that infusing the garnet-type solid electrolytes (GSEs) with air-stable electrolyte Li 3 PO 4 (LPO) dramatically reduces the interfacial resistance to ~1 Ω cm 2 and achieves a high critical current density of 2.2 mA cm -2 under ambient condition due to enhanced interfacial stability to Li metal anode. The coated and infused LPO electrolytes not only improve the mechanical strength and Li-ion conductivity of grain boundaries, but also form a stable Li-ion conductive but electron-insulating LPO-derived solid-electrolyte interphase between Li metal and GSEs, and consequently eliminates the Li dendrites growth and prevents the direct reduction of GSEs by Li metal over a long cycle life. This interface engineering approach together with grain-boundary modification on GSEs represents a promising strategy to revolutionize the anode-electrolyte interface chemistry for SSLBs and provides new design strategy for other-types of solid-state batteries.

25 ENERGY STORAGE↗
DOE OSTI2025

Measuring the buried interphase between solid electrolytes and lithium metal using neutrons

Interfaces are the key to next-generation high-energy batteries including solid-state Li metal batteries. In solid-state batteries, the buried nature of solid–solid electrolyte–electrode interfaces makes studying them difficult. Neutrons have significant potential to non-destructively probe these buried solid–solid interfaces. This work presents a comparative study using both neutron depth profiling (NDP) and neutron reflectometry (NR) to study a model lithium metal–lithium phosphorus oxynitride (LiPON) solid electrolyte system. In the NDP data, no distinct interphase is observed at the interface. NR shows a difference between electrodeposited, and vapor deposited LiPON–Li interfaces but finds both are gradient interphases that are less than 30 nm thick. Additional simulations of the LiPON–Li 2 O–Li system demonstrate that NDP has an excellent resolution in the 50 nm–1 μm regime while NR has an ideal resolution from 0.1–200 nm with different sample requirements. Together NDP and NR can provide a complementary understanding of interfaces between Li metal and solid electrolytes across relevant length scales.

Westover, Andrew S. [Oak Ridge National Laboratory↗
DOE OSTI2023

Unraveling the convoluted and dynamic interphasial mechanisms on Li metal anode

Accurate understanding of the chemistry of solid-electrolyte interphase (SEI) is key to developing new electrolytes for high-energy batteries using lithium metal (Li-0) anodes(1). SEI is generally believed to be formed by the reactions between Li-0 and electrolyte(2,3). However, our new study shows this is not the whole story. Through synchrotron-based X-ray diffraction and pair distribution function analysis, we reveal a much more convoluted formation mechanism of SEI, which receives considerable contributions from electrolyte, cathode, moisture and native surface species on Li-0, with highly dynamic nature during cycling. Using isotope labelling, we traced the origin of LiH to electrolyte solvent, moisture and a new source: the native surface species (LiOH) on pristine Li-0. When lithium accessibility is very limited as in the case of anode-free cells, LiOH develops into plate-shaped large crystals during cycling. Alternatively, when the lithium source is abundant, as in the case of Li||NMC811 cells, LiOH reacts with Li-0 to form LiH and Li2O. While the desired anion-derived LiF-rich SEI is typically found in the concentrated electrolytes or their derivatives, we found it can also be formed in low-concentration electrolyte via the crosstalk effect, emphasizing the importance of formation cycle protocol and opening up opportunities for low-cost electrolyte development.

Polzin, Bryant J.↗
DOE OSTI2025

Surprising Relationship between Silicon Anode Calendar Aging and Electrolyte Components in a Localized High-Concentration Electrolyte System

Although localized high-concentration electrolytes (LHCEs) have been shown to improve the calendar lifetime of silicon anodes, the roles of the electrolyte constituents in calendar aging are not well understood. Here, in this work, we utilize a voltage hold protocol and an LHCE with varying molar ratios of lithium bis(fluorosulfonyl)imide (LiFSI), tetramethylene sulfone (TMS), and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) to probe the component roles during aging. Interestingly, the estimated calendar lifetime and irreversible lithium losses from the V-hold experiments are independent of the electrolyte formulations. Contrarily, the solid electrolyte interphase (SEI) composition depends on the electrolyte formulation. X-ray photoelectron spectroscopy shows that TMS-coordinated species decompose to form insoluble alkanes and lithium hydroxide (LiOH), while lithium fluoride (LiF) originates from the anion-coordination complex. The SEI composition does not appear to play a significant role in the silicon anode passivity, as measured by parasitic current, suggesting that the SEI-electrolyte interactions dictate the calendar aging mechanisms.

Si anode↗
DOE OSTI2023

Review on Low-Temperature Electrolytes for Lithium-Ion and Lithium Metal Batteries

Abstract Among various rechargeable batteries, the lithium-ion battery (LIB) stands out due to its high energy density, long cycling life, in addition to other outstanding properties. However, the capacity of LIB drops dramatically at low temperatures (LTs) below 0 °C, thus restricting its applications as a reliable power source for electric vehicles in cold climates and equipment used in the aerospace. The electrolyte engineering has proved to be one of the most effective approaches to mitigate LIB performance degradation at LTs. In this review, we summarize the important factors contributing to the deterioration in Li + transport and capacity utilization at LTs while systematically categorize the solvents, salts and additives reported in the literature. Strategies to improve the Li + transport kinetics, in the bulk electrolyte and across the interphases, are discussed. In particular, the formation mechanism of solid electrolyte interphase and its functionality for LT electrolytes are analyzed. Perspectives on the future evolution of this area are also provided. Graphical abstract

25 ENERGY STORAGE↗
DOE OSTI2020

Low-temperature and high-rate-charging lithium metal batteries enabled by an electrochemically active monolayer-regulated interface

Stable operation of rechargeable lithium (Li)-based batteries at low temperatures is vital for cold-climate applications but is plagued with dendritic Li plating and unstable solid-electrolyte interphase (SEI). Here we report high-performance Li-metal batteries under low-temperature and high-rate-charging conditions. This is realized by utilizing a self-assembled monolayer of electrochemically active molecules on current collectors that regulates the nanostructure and composition of SEI and deposition morphology of Li metal anodes. A multilayer SEI containing a LiF-rich inner phase and amorphous outer layer effectively seals the Li surface in contrast to the conventional impassive SEI at low temperatures. As a result, galvanic Li corrosion and self-discharge were suppressed; stable Li deposition was realized from -60º to 45ºC; and a Li|LiCoO 2 cell with a capacity of 2.0 mAh cm -2 displayed a 200-cycle life at -15ºC with a recharge time of 45 minutes.

25 ENERGY STORAGE↗
DOE OSTI2022

Understanding the Origin of the Nonpassivating Behavior of Si-Based Anodes during the Initial Cycles

In this contribution, we combined electrochemical cycling and X-ray photoelectron spectroscopy (XPS) to understand the nonpassivating behavior of the solid electrolyte interphase (SEI) on Si anodes during the first cycles. Based on galvanostatic measurements, we show that the irreversible capacity loss is reduced after the first cycle, and it stays almost constant from the second cycle onwards. XPS was used to determine the root causes of the Coulombic inefficiency, showing that the rate of decomposition of the organic solvents strongly decreased after the first cycle, whereas the rate of salt decomposition is almost unchanged between cycles. We determine that the inhibition of the decomposition reaction of the organic solvent is responsible for the lower Coulombic loss during the second electrochemical cycle in comparison to the first, whereas the nonpassivating behavior toward the salt decomposition is one of the main causes of capacity loss upon cycling. Here, we further revisit the role of cracking in contributing to capacity loss. Whereas high volumetric expansion remains an issue plaguing the performance of Si anodes, our chronoamperometry studies reveal that the SEI formed on Si anodes does not passivate even when the electrode is fully expanded, and no additional surface is exposed. Overall, our work establishes the need to address the chemical and electrochemical instability of the SEI on the Si anode in addition to the more notorious issue of cracking.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Lithium-ion battery physics and statistics-based state of health model

A pseudo-2d model using COMSOL Multiphysics® software is developed to simulate performance and performance degradation of Li-ion batteries consisting of layered and olivine cathodes with graphite anode when subjected to peak shaving grid service. Multiple degradation pathways are considered, including solid electrolyte interphase (SEI) formation and breakdown at the anode, cathode dissolution and its synergistic effect on SEI formation at the anode. The model is validated by simulating commercial cylindrical cell performance. A global model is developed to simulate performance across all chemistries, along with individual chemistry models using global model parameters as initial values. There is good agreement between these models for various optimization parameters such as SEI equilibrium potential, cathode dissolution exchange current density, solvent diffusivity in the SEI and SEI ionic conductivity. To circumvent time constraints related to the COMSOL model, a 0d global model is developed which fits data well and provides more clarity on differences in cathode dissolution exchange current density. Again, good agreement for various optimization parameters is obtained among the COMSOL global & individual chemistry models and the 0-d model. The lessons learned from the physics-based model is used to develop a top down statistics-based model using current, voltage and anode volumetric change per mole lithium intercalated, along with their interactions as degradation predictors. This model predicts out of sample degradation for multiple grid services and electric vehicle drive cycle with high accuracy and provides the pathway to develop an efficient battery management system combining machine learning and findings from physics-based computationally intensive algorithms.

Crawford, Aladsair J.↗
DOE OSTI2022

Resolving Graphite‐Electrolyte Interphase of Lithium‐Ion Batteries using Air‐Tight Ambient Mass Spectrometry

Abstract The formation of a stable solid electrolyte interphase (SEI) at graphite electrode is necessary for lithium‐ion batteries (LIB) to prevent excessive degradation of electrolytes. Until now, the exact organic composition of SEI has not been decisively determined with lithium ethylene mono‐carbonate (LEMC) being one of the debated components. An air‐tight ambient mass spectrometry (MS) platform is developed to directly characterize the air‐sensitive organic components present in SEI. Ionization occurs via a solvent‐free field‐induced process at atmospheric pressure. Our experimental data, based on tandem MS analysis, revealed LEMC to be the major organic component in SEI. This result resolves a long‐standing mystery surrounding the composition of native SEI in LIB, where no trace of the other debated compound, lithium ethylene dicarbonate, was detected. The energetics of fragmentation of LEMC and the corresponding stabilities of various ionic species detected during the air‐tight ambient MS analysis were calculated using density functional theory (DFT). Our findings confirmed favorable protonation energies and suggested the molecular structures for many of the detected species. Solvent (i. e., ethylene carbonate)‐induced stabilization effects observed during the ionization process were also confirmed by DFT. The reported study encourages the routine use of ambient mass spectrometry to characterize both anodic and cathodic electrodes of all battery types as well as to study other air‐sensitive materials in their native state.

25 ENERGY STORAGE↗
DOE OSTI2021

Rejuvenating dead lithium supply in lithium metal anodes by iodine redox

Inactive lithium (more frequently called dead lithium) in the forms of solid-electrolyte interphase and electrically isolated metallic lithium is principally responsible for the performance decay commonly observed in lithium metal batteries. A fundamental solution of recovering dead lithium is urgently needed to stabilize lithium metal batteries. In this paper, we quantify the solid-electrolyte interphase components, and determine their relation with the formation of electrically isolated dead lithium metal. We present a lithium restoration method based on a series of iodine redox reactions mainly involving I 3 - /I - . Using a biochar capsule host for iodine, we show that the I 3 - /I - redox takes place spontaneously, effectively rejuvenating dead lithium to compensate the lithium loss. Through this design, a full-cell using a very limited lithium metal anode exhibits an excellent lifespan of 1,000 cycles with a high Coulombic efficiency of 99.9%. We also demonstrate the design with a commercial cathode in pouch cells. Cycling lithium batteries often results in inactive lithium that no longer participates in redox reactions, leading to performance deterioration. Here the authors use an iodic species to react with inactive lithium, bringing it back to life and thus making batteries last longer.

25 ENERGY STORAGE↗
DOE OSTI2021

High Interfacial-Energy and Lithiophilic Janus Interphase Enables Stable Lithium Metal Anodes

The stability of solid electrolyte interphase (SEI) layers is critical for developing lithium (Li) metal batteries. However, the fabrication of stable SEI layers is plagued by un-controlled structures, properties, and functions. In this work a controllable design of an ordered LiF-rich and lithiophilic hybrid Janus interphase (LiF-HJI) is reported using organic fluorination reagent as a functional SEI precursor. The LiF-HJI with a lower crystalline LiF layer and an upper Li organosulfide layer provides high interfacial energy with the Li metal and strong Li-ion affinity, allows homogenous Li-ion distribution, fast and uniform Li-ion transport, and excellent mechanical and passivation properties, enabling stable Li metal anodes under harsh conditions, such as high deposition capacities (6 mA h cm -2 ), current densities (10 mA cm -2 ), and rates (5 C). Stable LiF-HJI@Li greatly improves cycling stability and capacity retention (80.1% after 300 cycles) of Li||LiNi 0.8 Co 0.1 Mn 0.1 O 2 cells at a commercial-level areal capacity (≈4.2 mA h cm -2 ). Even under a lean-electrolyte condition of 3 g Ah -1 , 80% capacity retention can be maintained after 100 cycles, demonstrating excellent cycling performance under such harsh conditions.

25 ENERGY STORAGE↗