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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Long cycle and calendar life of Si-based Li-ion batteries enabled by localized high-concentration electrolytes and their surprising water tolerance

Silicon-based anodes promise an increase in energy density for Li-ion batteries, yet they suffer from a poor calendar life. Researchers have posited that fluorinated lithium salt forms reactive side products that destroy the solid electrolyte interphase (SEI), even without cycling. HF is one such reactive side product formed from trace water contamination in the electrolyte. Some electrolytes, such as localized high concentration electrolytes (LHCEs) may improve cell stability in highly reactive systems, such as Li metal and Si. In the present study, LHCEs containing 200-300 ppm of water retained up to 8% greater capacity (1200-1300 mAh/g Si) in calendar life tests over 200 days compared to dried electrolytes (< 20 ppm water). Calendar aging took place at 100% state of charge. Cells with 200-300 ppm water performed comparably to cells with 20 ppm water in cycle life tests (900-1000 mAh/g Si) . Even adding 1000 ppm water did not lead to rapid capacity fade in cells undergoing cycle life tests. Nano-FTIR spectroscopy revealed chemical and structural differences in the SEI for cells with 1000 ppm water compared to 200-300 ppm water. The SEI differences, including increased Li2O concentration, may have contributed to improved calendar life. This research reveals the capabilities of LHCEs to improve the calendar and cycle life of Si-based Li-ion batteries, despite the presence of a highly reactive contaminant.

25 ENERGY STORAGE↗
NASA NTRS2012

Solid State Multinuclear Magnetic Resonance Investigation of Electrolyte Decomposition Products on Lithium Ion Electrodes

Solid electrolyte interphase (SEI) formation in lithium ion cells prepared with advanced electrolytes is investigated by solid state multinuclear (7Li, 19F, 31P) magnetic resonance (NMR) measurements of electrode materials harvested from cycled cells subjected to an accelerated aging protocol. The electrolyte composition is varied to include the addition of fluorinated carbonates and triphenyl phosphate (TPP, a flame retardant). In addition to species associated with LiPF6 decomposition, cathode NMR spectra are characterized by the presence of compounds originating from the TPP additive. Substantial amounts of LiF are observed in the anodes as well as compounds originating from the fluorinated carbonates.

Li-ion battery electrolytes↗
DOE OSTI2025

Critical Insights into Solvent Choice for High-Voltage Organosulfur Electrolytes

Organosulfur electrolytes are promising candidates for enabling high-voltage cathodes due to their superior oxidative stability compared to conventional carbonate-based systems. However, their viscous nature and inability to passivate the anode necessitate the use of passivating agents and diluents to achieve meaningful charge/discharge rates. In this study, we investigate the use of cyclic fluorinated carbonates (CFCs) to form passivating interphases on electrode surfaces, aiming to optimize electrolyte performance in high-voltage systems. Electrolyte formulations containing 1.2 M LiPF 6 in a CFC:sulfone:1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropylether (TTE) mixture (2/5/3 V/V/V) were assessed in full-cell configurations with a LiNi 0.8 Mn 0.1 Co 0.1 O 2 (FCG-NMC) cathode and a 4.5 V upper cutoff potential. The results reveal that 3-3-3-trifluoropropylene carbonate (TFPC) combined with ethyl methyl sulfone (EMS) optimizes electrolyte performance, resulting in lower resistance buildup and reduced capacity loss compared to commercial electrolytes. We also explore the failure mechanisms of several carbonate/sulfone mixtures and identify key considerations for electrolyte compatibility in high-voltage systems. TFPC enhances cycling stability and lowers overall cell resistance, while fluoroethylene carbonate (FEC) formulations, despite higher ionic conductivity, fail to form adequate passivation layers, leading to rapid capacity loss. Additionally, EMS provides superior physical properties that avoid common failure modes seen with other sulfone solvents like methyl isopropyl sulfone and tetramethylene sulfone. Furthermore, this study underscores the importance of carefully selecting passivating carbonates and sulfone solvents to improve electrolyte performance and expand the viability of high-voltage electrolyte systems.

LiNi0.8Mn0.1Co0.1O2 cathode↗
DOE OSTI2025

Exploring Fluoropyridine Electrolytes in Li–S Batteries: Balancing Performance and Stability across Temperatures

A novel high-donor 3-fluoropyridine (3FPy) electrolyte has been introduced for use in Li-S batteries, demonstrating an inhibition effect on the polysulfide shuttle, even without the addition of LiNO 3 . In this study, fluoropyridine electrolytes, including 2-fluoropyridine (2FPy) and 3FPy electrolytes, are studied using electrochemical analysis, mass spectrometry (MS), and high-performance liquid chromatography (HPLC) methods. Collision-induced dissociation spectra revealed that Li + preferentially solvates with different fluoropyridines, with 2FPy exhibiting a stronger interaction due to ortho-fluorine's influence, compared to 4FPy and 3FPy. However, MS and HPLC analyses showed that 2FPy is reactive with polysulfides, while 3FPy offers high solubility for polysulfides and sulfur without reacting with them at room temperature. Further, despite 3FPy performing well at room temperature, further electrochemistry studies at elevated (60 °C) and reduced (0 °C) temperatures reveal the challenges. At high temperatures, LiNO 3 is essential to suppress the polysulfide shuttle; and at low temperatures, the performance with the 3FPy electrolyte significantly lags behind that of the ether-based electrolyte.

25 ENERGY STORAGE↗
DOE OSTI2021

Real Time Observation of Lithium Insertion into Pre-Cycled Conversion-Type Materials

Conversion-type electrode materials for lithium-ion batteries experience significant structural changes during the first discharge–charge cycle, where a single particle is taken apart into a number of nanoparticles. This structural evolution may affect the following lithium insertion reactions; however, how lithiation occurs in pre-cycled electrode materials is elusive. In this work, in situ transmission electron microscopy was employed to see the lithium-induced structural and chemical evolutions in pre-cycled nickel oxide as a model system. The introduction of lithium ions induced the evolution of metallic nickel, with volume expansion as a result of a conversion reaction. After pre-cycling, the phase evolutions occurred in two separate areas almost at the same time. This is different from the first lithiation, where the phase change takes place successively, with a boundary dividing the reacted and unreacted areas. Structural changes were restricted at the areas having large amount of fluorine, implying the residuals from the decomposition of electrolytes may have hindered the electrochemical reactions. This work provides insights into phase and chemical evolutions in pre-cycled conversion-type materials, which govern electrochemical properties during operation.

25 ENERGY STORAGE↗
DOE OSTI2023

Catalytic cathode for a lithium-oxygen battery

A metal-air battery includes an anode; a low-dimensional catalyst cathode; and an electrolyte; wherein: the low-dimensional catalyst cathode comprises a functional metal layer on a carbon support overcoated with a catalyst layer; the electrolyte comprises an aprotic solvent that is an ether-based solvent, a fluorinated ether-based solvent, an oligo (ethylene oxide) solvent, or a mixture of any two or more thereof; and the electrolyte is free of carbonate solvents.

25 ENERGY STORAGE↗
DOE OSTI2021

Superior long-term cycling of high-voltage lithium-ion batteries enabled by single-solvent electrolyte

A new single-solvent electrolyte system comprising lithium bis(fluorosuflonyl) imide (LiFSI) and beta-fluorinated sulfone (TFPMS) was designed to enable very stable long-term cycling of high-voltage lithium-ion batteries. Compared to other fluorinated solvents such as alpha-fluorinated sulfone (FMES) and fluorinated carbonate (FEMC), which are prone to reduction on the graphite anode, the LiFSI-TFPMS system displayed outstanding compatibility with graphite. While regular carbonate and sulfone from the LiFSI electrolyte system are compatible with the graphite anode, their high solvating power not only induces severe corrosion on the aluminum cathode current collector at high voltage, but also renders a low aggregation level at a normal salt concentration (about 1.0 M), resulting in the formation of an unstable solid-electrolyte interphase (SEI) on the graphite anode. Owing to the low solvating power of TFPMS, the aggregation level of the LiFSI-TFPMS system is relatively high even at normal salt concentration, which not only facilitates the formation of a robust SEI by the sacrificial decomposition of LiFSI, but also suppresses the aluminum corrosion of the LiFSI electrolyte system at high voltage. Together with the high intrinsic anodic stability of TFPMS, the superior cycling performance of graphite parallel to LiNi 0.6 Co 0.2 Mn 0.2 O 2 cells was achieved by employing the non-flammable LiFSI-TFPMS single-solvent electrolyte system.

25 ENERGY STORAGE↗
DOE OSTI2022

Enhancing Cycling Stability and Capacity Retention of NMC811 Cathodes by Reengineering Interfaces via Electrochemical Fluorination

High-capacity cathodes (LiNi 0.8 Mn 0.1 Co 0.1 O 2 ) that can boost the energy density of lithium-ion batteries are promising candidates for vehicle electrification. However, several factors specific to high energy density materials entailing electrode reactions inhibit their application. Fluorination has shown a promising ability to combat the detrimental electrochemical performances of cathode materials, however, it remains difficult to achieve the desired functionality. In this work, a novel electrochemical fluorination (ECF) that demonstrates a promising electrochemical performance enhancement via stabilization of the cathode–electrolyte-interphase (CEI) by forming conformal LiF is proposed. Besides LiF surface layer formation, ECF reduces the degree of fluorination-induced Ni/Li disordering and enhances the layered structural stability as probed by X-ray diffraction. Because of the robust CEI, ECF-NMC811 cathodes deliver 203.0 mAh g -1 first discharge capacity at the current rate of C/10, with ≈98% capacity retention up to 100 cycles. Similarly, it delivers ≈180 mAh g -1 capacity at a 1 C rate with 86.4% capacity retention up to 200 cycles with average coulombic efficiency of > 99.5%. Comprehensive characterization with a multitude of probes reveals that ECF enhances the cycling stability of the electrode without altering bulk structure and morphology.

25 ENERGY STORAGE↗
DOE OSTI2021

Role of Electrolyte in Overcoming the Challenges of LiNiO 2 Cathode in Lithium Batteries

LiNiO 2 (LNO) is a high-capacity and model cathode first discovered in the 1980s that fell out of favor due to its intrinsic instabilities. However, research activities toward LNO are once again on the rise as the push for higher-energy-density cells marches on. Here we demonstrate here that with appropriate modern electrolytes, major performance improvements can be achieved with LNO with no additional modifications. Cells with a localized high concentration electrolyte (LHCE) deliver 92% capacity retention after 200 cycles compared with 56% capacity retention in a baseline carbonate electrolyte, maintain 94% capacity after high-voltage storage compared with 77% capacity, and display a higher onset temperature of thermal runaway of 244 °C compared with 188 °C. These improvements are attributed to the LHCE’s high oxidative stability and its formation of fluorine-rich interphases. Although further characterization of this new class of electrolyte is necessary, this work demonstrates that modern electrolytes can be drop-in enablers of high-capacity, long-cycle-life cells.

25 ENERGY STORAGE↗
DOE OSTI2024

Enhancing Cycling Stability of Lithium Metal Batteries by a Bifunctional Fluorinated Ether

Abstract The lifespan of lithium (Li) metal batteries (LMBs) can be greatly improved by the formation of inorganic‐rich electrode‐electrolyte interphases (EEIs) (including solid‐electrolyte interphase on anode and cathode‐electrolyte interphase on cathode). In this work, a localized high‐concentration electrolyte containing lithium bis(fluorosulfonyl)imide (LiFSI) salt, 1,2‐dimethoxyethane (DME) solvent and 1,2‐bis(1,1,2,2‐tetrafluoroethoxy)ethane (BTFEE) diluent is optimized. BTFEE is a fluorinated ether with weakly‐solvating ability for LiFSI so it also acts as a co‐solvent in this electrolyte. It can facilitate anion decomposition at electrode surfaces and promote the formation of more inorganic‐rich EEI layers. With an optimized molar ratio of LiFSI:DME:BTFEE = 1:1.15:3, LMBs with a high loading (4 mAh cm −2 ) lithium nickel manganese cobalt oxide (LiNi 0.8 Mn 0.1 Co 0.1 ) cathode can retain 80% capacity in 470 cycles when cycled in a voltage range of 2.8–4.4 V. The fundamental understanding on the functionality of BTFEE revealed in this work provides new perspectives on the design of practical high‐energy density battery systems.

25 ENERGY STORAGE↗
NASA NTRS2014

Lithium-Ion Electrolytes Containing Flame Retardant Additives for Increased Safety Characteristics

The invention discloses various embodiments of Li-ion electrolytes containing flame retardant additives that have delivered good performance over a wide temperature range, good cycle life characteristics, and improved safety characteristics, namely, reduced flammability. In one embodiment of the invention there is provided an electrolyte for use in a lithium-ion electrochemical cell, the electrolyte comprising a mixture of an ethylene carbonate (EC), an ethyl methyl carbonate (EMC), a fluorinated co-solvent, a flame retardant additive, and a lithium salt. In another embodiment of the invention there is provided an electrolyte for use in a lithium-ion electrochemical cell, the electrolyte comprising a mixture of an ethylene carbonate (EC), an ethyl methyl carbonate (EMC), a flame retardant additive, a solid electrolyte interface (SEI) film forming agent, and a lithium salt.

Smart, Marshall C.↗
DOE OSTI2021

Polyfluorinated carbonate electrolyte for high-voltage lithium batteries

A non-aqueous solvent composition for a lithium battery comprises a fluorinated solvent mixture that consists essentially of a 1,2-difluoroethylene carbonate and a fluoro-substituted dialkyl carbonate in a respective weight ratio of about 1:3 to about 1:1, and optionally up to about 30 wt % of an additional organic solvent. An electrolyte for a lithium ion battery comprises a lithium salt dissolved in a non-aqueous solvent composition comprising the fluorinated solvent mixture.

Zhang, Zhengcheng↗
DOE OSTI2021

Examining CO 2 as an Additive for Solid Electrolyte Interphase Formation on Silicon Anodes

In this study, we demonstrate that the addition of CO 2 to a standard 1.0 M LiPF 6 3:7 wt% ethylene carbonate:ethyl methyl carbonate electrolyte results in the formation of a thinner insoluble solid electrolyte interphase (SEI) that is dominated by the presence of LiF. In contrast, cells without CO 2 result in a thicker insoluble SEI layer containing more organic constituents. The CO 2 is incorporated in the dimethyl carbonate soluble part of the SEI composed primarily of polymeric poly(ethylene oxide) (PEO) on the surface of a thin inorganic layer. This combination of properties from CO 2 addition provides an improved cycling performance through the reduction of irreversible side reactions, leading to higher coulombic efficiency. The results indicate that CO 2 incorporates into the SEI and plays a role similar to additives like fluorinated ethylene carbonate and vinylene carbonate with respect to polymeric components.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Molecular engineering of ethereal electrolyte for ultrastable Si-based high voltage full cells

The successful application of Si-based high-energy Li-ion batteries (LIBs) depends on our ability to tailor electrolyte properties to achieve long-term stability and reliable performance. In this work, we demonstrate our rationale for the molecular design of ethereal solvents to address low anodic stability issues and produce a highly electrochemically stable electrolyte for Si‖LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811) high-energy full cells. Unlike the trimethylsilyl group, the trifluoromethyl (–CF 3 ) group exerts a very strong electron-withdrawing effect on the glycol ether backbone, reducing the highest occupied molecular orbital (HOMO) energy level of the fluorinated glycol ether (FGE) and significantly enhancing its oxidation potential. The FGE-based electrolyte enables stable cycling of Si‖NMC811 full cells, delivering high specific capacity (900 mA h g −1 ) and coulombic efficiency (>99.78%) over extended (500) cycles. The improved electrochemical performance originates from the terminal fluorination of the diglyme backbone, which strengthens anion coordination in the solvation structure, leading to the preferential reduction of the FSI anion and the formation of robust solid electrolyte interphases (SEIs) on the Si surface. Through molecular engineering of ethereal solvents, we have discovered a promising candidate for a next-generation stable electrolyte, paving the way for the design of practical and commercially viable Si batteries.

Silicon anode↗
DOE OSTI2026

Solvation-guided inhibition of manganese dissolution of lithium- and manganese- rich cathode via cyclic carbonate molecular engineering

Lithium and manganese-rich (LMR) layered oxides represent a leading class of high-energy cathode materials, but their practical realization is fundamentally limited by severe manganese (Mn) dissolution, a process that triggers structural degradation and rapid capacity fade. While mitigation efforts have predominantly focused on interfacial engineering, the intrinsic contribution of bulk electrolyte solvation to this degradation pathway remains largely unexplored, primarily due to the difficulty of deconvolving its effects from concurrent cathode-electrolyte interphase (CEI) formation. Here, we report an experimental design to isolate the role of solvation. We systematically varied the electrolyte solvent solvation power by substituting the strongly coordinating ethylene carbonate (EC) with its weaker coordinating fluorinated derivatives, fluoroethylene carbonate (FEC) and trans-4,5-Difluoro-1,3-dioxolan-2-one (DFEC), while maintaining a consistent interfacial chemistry. Remarkably, the electrolyte formulated with the weakest solvent, DFEC, exhibits superior cycling stability, suppressing Mn dissolution by up to 63% relative to the conventional EC-based system. Post-mortem analysis unequivocally attributes this performance enhancement to the preservation of the LMR cathode's structural integrity, a direct consequence of mitigated Mn dissolution. This work provides conclusive evidence that modulating bulk electrolyte solvation is a potent and direct strategy for stabilizing LMR cathodes, establishing a vital design principle for next-generation battery systems.

25 ENERGY STORAGE↗
DOE OSTI2021

Stable fluorinated alkylated lithium malonatoborate salts for lithium-ion battery applications

The invention is directed in a first aspect to electrolyte salt of the general formula Li+Z−, wherein Z− has the following chemical formula: wherein R1 is an alkyl group (R′) containing at least one and up to twelve carbon atoms, and R2 and R3 are independently selected from fluorine atom, hydrocarbon groups R, alkoxy groups (—OR), and ester groups —OC(O)R, wherein R2 and R3 can optionally interconnect via R functionalities to form a boron-containing ring. The invention is also directed to electrolyte compositions in which the above electrolyte salt is incorporated. The invention is further directed to lithium-ion batteries containing these electrolytes.

Sun, Xiao-Guang↗
DOE OSTI2020

Non-aqueous electrolytes for lithium batteries

An electrochemical cell includes a cathode active material, lithium metal, a separator, and an electrolyte comprising a lithium salt, an organic aprotic solvent and a fluorinated sulfone represented by Formula II:

Su, Chi Cheung↗
DOE OSTI2026

Solvent–Diluent Engineering of Normal-Concentration Organosulfur Electrolytes for High-Voltage Lithium-Ion Batteries

Enabling high‑voltage batteries depends critically on rational electrolyte design. Conventional carbonate electrolytes with LiPF 6 suffer from insufficient oxidative stability, motivating the use of lithium bis(fluorosulfonyl)imide (LiFSI) for its superior high‑temperature and high‑voltage performance. However, LiFSI is relatively costly, and its electrolytes often require high concentrations to suppress aluminum current collector corrosion in cathode architectures and to adequately passivate electrode interfaces. Here, a low‑concentration LiFSI electrolyte is realized by combining a high‑voltage organosulfur solvent, ethyl methyl sulfone (EMS), with a non‑solvating fluorinated diluent, fluorobenzene (FB). Extended cycling of LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811) full cells to 4.5 V reveals substantial long‑term performance advantages over conventional carbonate electrolytes. Comparison with a popular cyclic sulfone, tetramethylene sulfone (TMS), shows that ring‑containing structures such as TMS strongly influence passivation behavior, ultimately limiting performance and narrowing the viable operating window. Overall, EMS is identified as a uniquely stable solvent for LiFSI‑based electrolytes operating at moderately high voltages.

Dato, Michael A. [Argonne National Laboratory (ANL↗