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All sources NASA NTRS DOE OSTI

DOE OSTI2020

A redox-active organic cation for safer high energy density Li-ion batteries

Ni-rich layered cathode materials are at the forefront to be deployed in high energy density Li-ion batteries for the automotive market. However, the intrinsic poor structural and interfacial stability during overcharging could trigger violent thermal failure, which severely limits their wide application. To protect the Ni-rich cathode from overcharging, we firstly report a redox-active cation, thioether-substituted diaminocyclopropenium, as an electrolyte additive to limit the cell voltage within the safe value during overcharging. The organic cation demonstrates a record-breaking electrochemical reversibility at ~4.55 V versus Li + /Li and solubility (0.5 M) in carbonate-based electrolyte. The protection capability of the additive was explored in two cell chemistries: a LiNi 0.8 Co 0.15 Al 0.05 O 2 /graphite cell and a LiNi 0.8 Co 0.15 Al 0.05 O 2 /silicon–graphene cell with areal capacities of ~2.2 mA h cm -2 and ~3 mA h cm -2 , respectively. With 0.2 M addition, the LiNi 0.8 Co 0.15 Al 0.05 O 2 /graphite cell survived 54 cycles at 0.2C with 100% overcharge. Moreover, the cell can carry an utmost 4.4 mA cm -2 (2C) with 100% overcharge and a maximum capacity of 7540% SOC at 0.2C.

25 ENERGY STORAGE↗

DOE OSTI2025

Designing Advanced Electrolytes for High-Voltage High-Capacity Disordered Rocksalt Cathodes

Lithium (Li)-excess transition metal oxide materials which crystallize in the cation-disordered rock salt (DRX) structure are promising cathodes for realizing low-cost, high-energy-density Li batteries. However, the state-of-the-art electrolytes for Li-ion batteries cannot meet the high-voltage stability requirement for high-voltage DRX cathodes, thus new electrolytes are urgently demanded. It has been reported that the solvation structures and properties of the electrolytes critically influence the performance and stability of the batteries. In this study, the structure–property relationships of various electrolytes with different solvent-to-diluent ratios are systematically investigated through a combination of theoretical calculations and experimental tests and analyses. This approach guides the development of electrolytes with unique solvation structures and characteristics, exhibiting high voltage stability, and enhancing the formation of stable electrode/electrolyte interphases. These electrolytes enable the realization of Li||Li 1.094 Mn 0.676 Ti 0.228 O 2 (LMTO) DRX cells with improved performance compared to the conventional electrolyte. Specifically, Li||LMTO cells with the optimized advanced controlled-solvation electrolyte deliver higher specific capacity and longer cycle life compared to cells with the conventional electrolyte. Additionally, the investigation into the structure–property relationship provides a foundational basis for designing advanced electrolytes, which are crucial for the stable cycling of emerging high-voltage cathodes.

25 ENERGY STORAGE↗

DOE OSTI2025

Multi-phase characterization of pitch-carbon coated nano-silicon anodes for lithium-ion batteries

Silicon (Si) is a leading next-generation Li-ion battery anode candidate that meets rigorous performance demands for portable power including enhanced power and energy density with robust cycling performance. However, a series of complex and interrelated reactions lead to reduced calendar life in Si-containing systems and therefore challenge practical adoption. In the present work, we probe the mechanisms underlying observed performance improvements by adding a pitch-carbon coating onto nano-Si material. We pair solid-phase (X-ray photoemission spectroscopy, Fourier-transform infrared), semi-volatile phase (solid-phase microextraction-gas chromatography-mass spectrometry), and gas-phase (gas chromatography-flame-ionization detector) characterization signals to comprehensively evaluate the impact of pitch-carbon coating on the evolution of the Si solid-electrolyte interphase (SEI) and the associated impacts on electrode/electrolyte reactivity. The pitch-carbon is found to serve as a physicochemical barrier, reducing the electro-active surface area for Si/electrolyte reactivity and preventing Si oxidation. Further, the pitch-carbon coating promotes the evolution of a more-favorable SEI by subsuming substantial functionality typically associated with the fluoroethylene carbonate (FEC) electrolyte additive - such as alkoxide scavenging and suppression of transesterification pathways - and by shifting the competitive electrolyte degradation pathways' favorability. The multi-phase characterization approach enables holistic end-products evaluation from complex (electro)chemical interfacial reactions, which informs a robust interpretation of the carbon coating's role in electrochemical performance improvements. The present mechanistic evaluation aids the rational design for improved nano-Si materials.

25 ENERGY STORAGE↗

DOE OSTI2022

Self-assembling and self-healing rechargeable Li batteries Final Scientific/Technical Report

PROJECT OBJECTIVE: Investigate formation of lithium halide containing solid electrolyte interface. Characterize the structure and composition of the solid electrolyte interface surface film and morphology of the electrochemically deposited Li. Develop combinations of electrolytes (solvents + salts) and electrolyte additives that produce a highly Li-ion conducting, mechanically robust, and self-healing solid electrolyte interface to suppress Li dendrite formation and improve Coulombic efficiency.

Chiang, Yet-Ming↗

DOE OSTI2024

Surfactant Effects in Porous Electrodes for Microemulsion Redox Flow Batteries

The effect of surfactant additives on electrochemical behavior in porous electrodes was investigated using vanadium redox flow battery half-cells and the dependence of volumetric kinetics and mass transport on electrolyte, surfactant, and electrode type was explored. Without surfactant added, carbon paper electrodes demonstrated greater kinetics and transport compared to carbon felt, for a given electrolyte. Additionally, posolyte kinetics are greater than negolyte kinetics by one to three orders of magnitude, depending on the electrode type. Addition of surfactant increased electrode wettability and possibly electrochemical surface area. However, this was accompanied by a decrease in volumetric mass transport, due to stronger electrolyte-electrode interactions. The presence of sodium dodecyl sulfate (SDS) influenced posolyte and negolyte kinetics differently. Kinetics showed a dependence on electrode type and surfactant. On carbon felt, volumetric kinetics decreased for both posolyte and negolyte with SDS addition. On carbon paper, SDS decreased volumetric kinetics for the posolyte but increased (>2X) kinetics for the negolyte! This kinetic enhancement depends on surfactant chemistry: cetyltrimethylammonium bromide, a cationic surfactant, failed to increase kinetics. Furthermore, SDS did not increase areal specific resistance. Furthermore, these findings show the superior performance of carbon paper compared to carbon felt and suggest SDS as a possible VRFB negolyte additive.

25 ENERGY STORAGE↗

NASA NTRS2012

Electrolytes for Use in High Energy Lithium-ion Batteries with Wide Operating Temperature Range

Met programmatic milestones for program. Demonstrated improved performance with wide operating temperature electrolytes containing ester co-solvents (i.e., methyl butyrate) containing electrolyte additives in A123 prototype cells: Previously demonstrated excellent low temperature performance, including 11C rates at -30 C and the ability to perform well down to -60 C. Excellent cycle life at room temperature has been displayed, with over 5,000 cycles being demonstrated. Good high temperature cycle life performance has also been achieved. Demonstrated improved performance with methyl propionate-containing electrolytes in large capacity prototype cells: Demonstrated the wide operating temperature range capability in large cells (12 Ah), successfully scaling up technology from 0.25 Ah size cells. Demonstrated improved performance at low temperature and good cycle life at 40 C with methyl propionate-based electrolyte containing increasing FEC content and the use of LiBOB as an additive. Utilized three-electrode cells to investigate the electrochemical characteristics of high voltage systems coupled with wide operating temperature range electrolytes: From Tafel polarization measurements on each electrode, it is evident the NMC-based cathode displays poor lithium kinetics (being the limiting electrode). The MB-based formulations containing LiBOB delivered the best rate capability at low temperature, which is attributed to improved cathode kinetics. Whereas, the use of lithium oxalate as an additive lead to the highest reversible capacity and lower irreversible losses.

low temperature batteries↗

DOE OSTI2020

Calculated Reduction Potentials of Electrolyte Species in Lithium–Sulfur Batteries

In this work, reduction potentials of electrolyte molecules in the lithium–sulfur (Li/S) battery and their variations in several solvent environments are studied using the density functional theory method with Dunning’s triple-ζ correlation consistent basis set. Reliable reduction potential values are key for electrolyte additive design needed for suppressing polysulfide dissolution shuttle mechanism, resulting in poor cycle performance and severe self-discharge of the Li/S battery. Although isolated electrolyte molecules have reduction potentials outside the operating voltage range of the Li/S battery, complexation with other electrolyte species enables the electrolyte molecules to be reduced within the operating voltage range. Among the electrolyte species considered in this study, bis(fluorosulfonyl)imide (FSI – ) and fluoroethylene carbonate (FEC) yield reduction potentials within the expected range, suggesting the development of fluorine-containing additives as a promising line of research.

25 ENERGY STORAGE↗

DOE OSTI2020

Stable Potassium Metal Anodes with an All-Aluminum Current Collector through Improved Electrolyte Wetting

This is the first report of successful potassium metal battery anode cycling with an aluminum-based rather than copper-based current collector. Dendrite-free plating/stripping is achieved through improved electrolyte wetting, employing an aluminum-powder-coated aluminum foil “Al@Al,” without any modification of the support surface chemistry or electrolyte additives. The reservoir-free Al@Al half-cell is stable at 1000 cycles (1950 h) at 0.5 mA cm -2 , with 98.9% cycling Coulombic efficiency and 0.085 V overpotential. The pre-potassiated cell is stable through a wide current range, including 130 cycles (2600 min) at 3.0 mA cm -2 , with 0.178 V overpotential. Al@Al is fully wetted by a 4 m potassium bis(fluorosulfonyl)imide-dimethoxyethane electrolyte (θCA = 0°), producing a uniform solid electrolyte interphase (SEI) during the initial galvanostatic formation cycles. On planar aluminum foil with a nearly identical surface oxide, the electrolyte wets poorly (θCA = 52°). This correlates with coarse irregular SEI clumps at formation, 3D potassium islands with further SEI coarsening during plating/stripping, possibly dead potassium metal on stripped surfaces, and rapid failure. The electrochemical stability of Al@Al versus planar Al is not related to differences in potassiophilicity (nearly identical) as obtained from thermal wetting experiments. Additionally, planar Cu foils are also poorly electrolyte-wetted and become dendritic. The key fundamental takeaway is that the incomplete electrolyte wetting of collectors results in early onset of SEI instability and dendrites.

25 ENERGY STORAGE↗

NASA NTRS1983

Cycle life test and failure model of nickel-hydrogen cells

Six ampere hour individual pressure vessel nickel hydrogen cells were charge/discharge cycled to failure. Failure as used here is defined to occur when the end of discharge voltage degraded to 0.9 volts. They were cycled under a low earth orbit cycle regime to a deep depth of discharge (80 percent of rated ampere hour capacity). Both cell designs were fabricated by the same manufacturer and represent current state of the art. A failure model was advanced which suggests both cell designs have inadequate volume tolerance characteristics. The limited existing data base at a deep depth of discharge (DOD) was expanded. Two cells of each design were cycled. One COMSAT cell failed at cycle 1712 and the other failed at cycle 1875. For the Air Force/Hughes cells, one cell failed at cycle 2250 and the other failed at cycle 2638. All cells, of both designs, failed due to low end of discharge voltage (0.9 volts). No cell failed due to electrical shorts. After cell failure, three different reconditioning tests (deep discharge, physical reorientation, and open circuit voltage stand) were conducted on all cells of each design. A fourth reconditioning test (electrolyte addition) was conducted on one cell of each design. In addition post cycle cell teardown and failure analysis were performed on the one cell of each design which did not have electrolyte added after failure.

Smithrick, J. J.↗

NASA NTRS1983

Cycle life test and failure model of nickel-hydrogen cells

Smithrick, J. J.↗

DOE OSTI2024

Enhancing the dark-state bistability and thermal stability of zinc dynamic windows with nitrile electrolytes

Reversible metal electrodeposition (RME) for dynamic windows is a promising alternative to traditional electrochromics. We explore the reasons behind the bistability of practical RME dynamic windows under a wide temperature range, i.e., how well they maintain their dark state without external power. While Zn dynamic windows with dimethyl sulfoxide electrolytes exhibit adequate bistability at room temperature, their performance degrades at elevated temperatures due to the presence of small amounts of water. Here, to overcome this problem, we developed a set of Zn nitrile electrolytes. The integrated devices can maintain dark-state bistability over at least 1 month at 85°C with 0.1% transmission using a propionitrile (PrCN) electrolyte. Additionally, the PrCN-based Zn dynamic windows possess high optical contrast, color-neutral switching, and promising cyclability, making Zn RME in nitrile electrolytes a promising solution for achieving robust dynamic windows.

RME↗

DOE OSTI2023

Tuning Bulk Redox and Altering Interfacial Reactivity in Highly Fluorinated Cation-Disordered Rocksalt Cathodes

Lithium-excess, cation-disordered rocksalt (DRX) materials have been subject to intense scrutiny and development in recent years as potential cathode materials for Li-ion batteries. Despite their compositional flexibility and high initial capacity, they suffer from poorly understood parasitic degradation reactions at the cathode-electrolyte interface. These interfacial degradation reactions deteriorate both the DRX material and electrolyte, ultimately leading to capacity fade and voltage hysteresis during cycling. In this work, differential electrochemical mass spectrometry (DEMS) and titration mass spectrometry are combined to quantify the extent of bulk redox and surface degradation reactions for a set of Mn 2+/4+ -based DRX oxyfluorides during initial cycling with a high-voltage charging cutoff (4.8 V vs Li/Li + ). Increasing the fluorine content from 7.5 to 33.75% is shown to diminish oxygen redox and suppresses high-voltage O 2 evolution from the DRX surface. Additionally, electrolyte degradation processes resulting in the formation of both gaseous species and electrolyte-soluble protic species are observed. Subsequently, DEMS is paired with a fluoride-scavenging additive to demonstrate that increasing fluorine content leads to increased dissolution of fluorine from the DRX material into the electrolyte. Finally, a suite of ex situ spectroscopy techniques (X-ray photoelectron spectroscopy, inductively coupled plasma optical emission spectroscopy, and solid-state nuclear magnetic resonance spectroscopy) are employed to study the change in DRX composition during charging, revealing the dissolution of manganese and fluorine from the DRX material at high voltages. Here this work provides insight into the degradation processes occurring at the DRX-electrolyte interface and points toward potential routes of interfacial stabilization.

25 ENERGY STORAGE↗

DOE OSTI2021

Development of cathode-electrolyte-interphase for safer lithium batteries

Accompanied by the adoption of aggressive cathodes to continuously improve batteries energy density, enhancing their safety is becoming increasingly urgent for the electric vehicle development. In-situ controllable formation of robust cathode-electrolyte interphase (CEI) with high inorganic content seems to be the most promising strategy to address the thermal runaway concerns. Moreover, the in-situ formation strategy via suitable electrolyte replacement or electrolyte additives is extremely simple yet effective, especially for industrial manufacture of batteries. Here, this paper briefly reviews recent advanced CEIs formed by conventional carbonate-based electrolytes, fluorinated electrolytes, concentrated electrolytes, and solid state electrolytes. The focus on the thermal stability of the cathodes after CEI modification, and at the same time conduct safety tests at the material, cell, and module levels for comprehensive evaluation are encouraged. The review will provide inspiration for future developments in battery safety and push forward the practical applications of newly developed high-energy density batteries.

25 ENERGY STORAGE↗

DOE OSTI2020

Tackling the Capacity Fading Issue of Li–S Battery by a Functional Additive—Hexafluorobenzene

Due to the strong electron-withdrawing fluorine groups, the aromatic ring of hexafluorobenzene (HFB) becomes more electron-deficient and strongly interacts with the lone-pair electrons of the medium. When used as an electrolyte additive for Li-S cell, HFB preferably coordinates with low-order lithium sulfides Li 2 S and Li 2 S 2 and subsequently reacts and converts both into active aromatic sulfides-bis(pentafluorophenyl) disulfides and bis-(pentafluorophenyl) polysulfides in situ-thus facilitating the utilization of the electronically insulating Li 2 S and Li 2 S 2 and improving the cycling stability of the Li-S cell. Finally, this research opens a new avenue to tackle the inherent issues associated with the Li-S chemistry.

25 ENERGY STORAGE↗

DOE OSTI2024

Accelerating Computational Materials Discovery with Machine Learning and Cloud High-Performance Computing: from Large-Scale Screening to Experimental Validation

High-throughput computational materials discovery has promised significant acceleration of the design and discovery of new materials for many years. Despite a surge in interest and activity, the constraints imposed by large-scale computational resources present a significant bottleneck. Furthermore, examples of large-scale computational discovery carried through experimental validation remain scarce, especially for materials with product applicability. In this paper, we demonstrate how this vision became reality by first combining state-of-the-art artificial intelligence (AI) models and traditional physics-based models on cloud high performance computing (HPC) resources to quickly navigate through more than 32 million candidates and predict around half a million potentially stable materials. Focusing on solid-state electrolytes for battery applications, our discovery pipeline further identified 18 promising candidates with new compositions and rediscovered a decade’s worth of collective knowledge in the field as a byproduct. By employing around one thousand virtual machines in the cloud, this process took less than 80 hours. We then synthesized and experimentally characterized the structures and conductivities of our top candidates, the Na x Li 3-x YCl 6 (0.5 ≤ x ≤ 2.5) series, demonstrating the potential of these compounds to serve as solid electrolytes. Additional candidate materials are currently under experimental investigation that could offer more examples of the computational discovery of new phases of Li- and Na-conducting solid electrolytes. We believe this unprecedented approach of synergistically integrating AI models and cloud HPC not only accelerates materials discovery but also showcases the potency of AI-guided experimentation in unlocking transformative scientific breakthroughs with real-world applications.

36 MATERIALS SCIENCE↗

NASA NTRS1982

Pore size engineering applied to starved electrochemical cells and batteries

To maximize performance in starved, multiplate cells, the cell design should rely on techniques which widen the volume tolerance characteristics. These involve engineering capillary pressure differences between the components of an electrochemical cell and using these forces to promote redistribution of electrolyte to the desired optimum values. This can be implemented in practice by prescribing pore size distributions for porous back-up plates, reservoirs, and electrodes. In addition, electrolyte volume management can be controlled by incorporating different pore size distributions into the separator. In a nickel/hydrogen cell, the separator must contain pores similar in size to the small pores of both the nickel and hydrogen electrodes in order to maintain an optimum conductive path for the electrolyte. The pore size distributions of all components should overlap in such a way as to prevent drying of the separator and/or flooding of the hydrogen electrode.

Abbey, K. M.↗

DOE OSTI2024

Spatial Progression of Polysulfide Reactivity with Lithium Nitrate in Li–Sulfur Batteries

LiNO 3 is a commonly used electrolyte additive in Li-S batteries, but the intricacies of its stabilizing effect on these batteries are not well-understood due to the complex chemical nature of Li-S electrolytes. This complexity often hampers clear characterization and interpretation of data. In this study, we explore the reactivity of LiNO 3 in Li-S batteries through in operando sulfur K-edge spectroscopy. To remove ambiguities, a sulfur-free electrolyte with LiNO 3 as the sole salt is used. This allows a precise elucidation of the reaction mechanism between LiNO 3 and polysulfides. Here, we observe that the reaction is chemical in nature and progresses spatially, influenced by the polysulfide concentration gradient across the electrolyte. Polysulfides are electrochemically generated in situ on the cathode side, leading to high local concentration. As a result, they cannot be fully oxidized by LiNO 3 and forms sulfites initially which are gradually further oxidized into sulfonates and sulfates. Conversely, polysulfides on the anode side have lower local concentration as they are not generated in situ but diffused from the cathode side. Their reaction with LiNO 3 leads to highly oxidized species like sulfonates and sulfates. These reaction products are not reduced during electrochemically cycling, suggesting their capabilities of passivating the electrodes and contributing to the cycle stabilities of Li-S batteries.

25 ENERGY STORAGE↗

DOE OSTI2024

Lithium ion cells with high performance electrolyte and silicon oxide active materials achieving very long cycle life performance

Improved negative electrodes can comprise a silicon based active material blended with graphite to provide more stable cycling at high energy densities. In some embodiments, the negative electrodes comprise a blend of polyimide binder mixed with a more elastic polymer binder with a nanoscale carbon conductive additive. Electrolytes have been formulated that provide for extended cycling of cells incorporating a mixture of a silicon-oxide based active material with graphite active material in negative electrodes that can be matched with positive electrodes comprising nickel rich lithium nickel manganese cobalt oxides to cells with unprecedented cycling properties for large capacity cell based on a silicon negative electrode active material.

Dong, Yingnan↗