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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Unveiling the Thermal Stability of Sodium Ion Pouch Cells Using Accelerating Rate Calorimetry

The thermal stability of ~420 mAh Na 0.97 Ca 0.03 [Mn 0.39 Fe 0.31 Ni 0.22 Zn 0.08 ]O 2 (NCMFNZO)/hard carbon (HC) pouch cells was investigated using accelerating rate calorimetry (ARC) at elevated temperatures. 1 m NaPF 6 in propylene carbonate (PC):ethyl methyl carbonate (EMC) (1:1 by volume) was used as a control electrolyte. Adding 2 wt% fluoroethylene carbonate to the electrolyte improves the cell's thermal stability by decreasing the self-heating rate (SHR) across the whole testing temperature range. The selected states-of-charge (SoC), including 70%, 84%, and 100%, exhibit minimal impact on the exothermic behavior, except for a slight decrease in SHR after ~275 °C at 70% SoC. When compared to traditional lithium-ion batteries operating at 100% SoC, NCMFNZO/HC pouch cells demonstrate inferior thermal stability compared to LiFePO 4 (LFP)/graphite pouch cells, displaying a higher SHR from 220 to 300 °C. LiNi 0.8 Mn 0.1 Co 0.1 O 2 /graphite + SiO x pouch cells exhibit the worst safety performance, with an early onset temperature of ~100 °C and the highest SHR across the entire temperature range. These results offer a direct comparison of the impact of SoC and electrolyte compositions on the thermal stability of SIBs at elevated temperatures, highlighting that there is still room for improvement in SIBs safety performance compared to LFP/graphite chemistry.

42 ENGINEERING↗
DOE OSTI2022

Anomalous Thermal Decomposition Behavior of Polycrystalline LiNi 0.8 Mn 0.1 Co 0.1 O 2 in PEO-Based Solid Polymer Electrolyte

we report that replacing liquid electrolytes (LEs) with polymer electrolytes has been considered a promising approach to developing next-generation lithium-ion batteries (LIBs) with high energy density and superior safety. Nevertheless, compared with the extensive research on the electrochemical stability of the cathode/polymer electrolyte interfaces, reports on their thermal behaviors are rare to date. Herein, this work systematically investigates the thermal stability of two typical layered oxide cathodes, LiCoO 2 (LCO) and LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811), with poly(ethylene oxide) (PEO) electrolyte and with carbonate LEs, respectively. It is found that the oxygen release from the cathodes plays a central role in thermal runaway. Replacing the LE with PEO electrolyte can considerably improve the thermal stability of LCO, but surprisingly, deteriorate that of NMC811. The reason is that the surface of single-crystalline LCO particles can be effectively passivated by the PEO electrolyte during heating, but PEO cannot sufficiently passivate all the primary particles of NMC811 owing to insufficient interface wettability of PEO electrolyte within the polycrystalline secondary NMC811 particles. The findings in this work collectively formulate valuable guidance for improving the safety of polymer-electrolyte-based as well as other types of all-solid-state lithium-ion batteries.

25 ENERGY STORAGE↗
DOE OSTI2026

Mechanistic origin of solvent-dependent thermal stability in sodiated Sn anodes for sodium-ion batteries

Understanding the thermal stability of high-energy density alloy anodes is critical for the safe deployment of sodium-ion batteries (SIBs). Here, accelerating rate calorimetry (ARC), post-mortem characterizations, and density functional theory (DFT) calculations are combined to understand the thermal reactivity of fully sodiated Sn, Sn-hard carbon (HC) blends, and HC anodes in carbonate- and ether-based electrolytes. ARC measurements show that propylene carbonate (PC) causes earlier self-heating rate (SHR) onset and higher reactivity than tetraethylene glycol dimethyl ether (TEGDME), indicating inferior thermal stability. Sodiated Sn exhibits better thermal stability than sodiated HC, while Sn-HC blends show intermediate behavior that improves with increasing Sn content. Post-ARC analyses reveal desodiation of Na15Sn4 to metallic Sn with particle coalescence, whereas Sn-HC blends and HC retain finer morphologies. PC promotes Sn oxidation to SnO, while TEGDME suppresses oxide formation; NaPF6-containing electrolytes additionally form NaF. DFT calculations show that PC adsorption lowers Na extraction energy and enhances interfacial electronic interactions, facilitating Na release and reductive decomposition. These results establish a direct correlation between solvent-dependent reaction pathways and thermal stability in SIB alloy anodes.

Accelerating rate calorimetry↗
DOE OSTI2024

Stabilizing LiCoO 2 at 4.6 V by regulating anti-oxidative solvents

For LiCoO 2 (LCO) operating at high voltages (>4.5 V vs. Li/Li + ), the intensive side reactions between LCO and traditional ethylene carbonate (EC)-based electrolytes with LiPF 6 salts can produce plenty of corrosive species (such as HF and HPO 2 F 2 ), causing severe surface degradation. Herein, anti-oxidative fluoroethylene carbonate (FEC) and difluoroethylene carbonate (DFEC) were selected as co-solvents to reduce the generation of corrosive species. Besides, PF 6 − anions enrich the Helmholtz plane of the LCO/electrolyte interface and promote the formation of a robust cathode/electrolyte interphase (CEI) featuring LiF/Li x PO y F z /Li 3 PO 4 inorganics and P-containing organics under the synergy of fluorinated solvents, which significantly inhibits the catalysis of highly oxidative Co 4+ /O n− (0 < n < 2). Benefiting from the reduced corrosive species and reinforced CEI, the layered structure of the LCO surface is well preserved during long-term cycling, with a highly reversible O3/H1-3 phase transition. Consequently, a LCO||graphite pouch cell exhibits a remarkable capacity retention of 85.7% after 500 cycles in 3.0–4.55 V. Furthermore, this work provides a new insight into developing advanced functional electrolytes for high-voltage lithium-ion batteries.

Co/O loss↗
DOE OSTI2022

Multimodal quantification of degradation pathways during extreme fast charging of lithium-ion batteries

Enabling fast charging of Li-ion batteries will be a key step towards realizing the technology's full potential in electric vehicles. Currently, fast charging is limited by a variety of processes that reduce cell capacity upon extended cycling. Using a multimodal approach combining incremental capacity analysis (dQ/dV), high energy X-ray diffraction (HEXRD), and mass spectrometry titration (MST), we identify specific degradation mechanisms—including Li plating, dead Li x C 6 formation, Li 2 C 2 formation, solid carbonate solid-electrolyte interphase (SEI) deposition, and loss of positive electrode active material (LAM PE )—that occur during extended fast charge cycling. We find that Li plating is the major source of capacity loss in cells cycled at 6C, while non-carbonate SEI species deposition on the graphite anode is the main source of capacity loss when cycled at 4C. We also study local degradative phenomena by examining specific ~1–5 cm 2 regions of the cells using HEXRD and MST. Here, we find that plated Li is often collocated with dead Li x C 6 , Li 2 C 2 , and solid carbonate SEI species, and these additional species cumulatively account for ~20% of the capacity lost during 6C cycling. Finally, in a cell with an anomalously high amount of LAM PE (quantified via dQ/dV), we find that regions of cathode degradation were accompanied by non-carbonate SEI products on the adjacent region of the anode. We postulate that this phenomenon arises due to crosstalk between the electrodes, wherein soluble electrolyte oxidation products formed at the delithiated cathode migrate to the graphite anode and are ultimately deposited on the graphite surface. This work demonstrates the utility of combining multiple characterization techniques to reveal a more holistic understanding of degradative phenomena that occur across multiple length scales during fast charge.

25 ENERGY STORAGE↗
DOE OSTI2023

Superior metal storage behavior of Zn-containing porous carbon nanostructures for Na and Li metal batteries

Na and Li metals are ideal anodes for high-energy rechargeable batteries. However, their poor coulombic efficiency and the associated safety issues due to dendritic metal deposition and large volume changes during metallic plating/stripping are the major causes that persistently hinder their practical energy-storage applications. Herein, Zn-containing carbon nanostructures derived from typical zeolitic imidazolate framework-8 (ZIF-8) are proposed as advanced metal anode materials for both Na and Li metal batteries. In this study; the three-dimensional interconnected porous surfaces confine metallic Na and Li within the nanostructures, filling the carbon scaffold, and covering the electrode surface to form stable solid electrolyte interphases. Based on the metal nucleation and growth results obtained through various electrochemical tests, Zn incorporation and pore morphology have been revealed to be the key factors that regulate the metal nucleation and metallic plating/stripping during cycling. Thus, the incorporation of Zn in the closed pores of a carbon nanostructure improves the cycle performance, even in carbonate electrolytes, and produces stable Na and Li metallic anodes for next-generation rechargeable batteries.

25 ENERGY STORAGE↗
DOE OSTI2023

Enhancing the activity of Fe-N-C oxygen reduction reaction electrocatalysts by high-throughput exploration of synthesis parameters

Here, the most active class of platinum group metal-free (PGM-free) oxygen reduction reaction (ORR) electrocatalysts in acidic electrolytes are those synthesized by heat treatment of iron, carbon, nitrogen precursors (Fe-N-C). Due to the large number of possible precursor compounds, a small fraction of the synthesis variable space has been explored. Correlation of synthesis variables with Fe speciation and ORR activity has been limited. In this work, an automation platform and a multi-port ball-milling were utilized to evaluate the effects of synthesis variables, such as identity of iron precursor, iron loading, and carbon and nitrogen sources on the ORR activity of iron -nitrogen-carbon catalysts in acidic electrolyte. The ORR activity is correlated with catalyst Fe speciation determined using Fe K-edge X-ray absorption spectroscopy (XAFS).

30 DIRECT ENERGY CONVERSION↗
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↗
DOE OSTI2026

Average hydrodynamic radius analysis reveals critical solvation thresholds in high-concentration lithium electrolytes

Understanding the solvation structures of lithium salts in carbonate- and ether-based electrolytes is central to explaining the exceptional stability of high-concentration electrolytes (HCEs) and localized high-concentration electrolytes (LHCEs). Conventional techniques such as vibrational spectroscopy and one-dimensional NMR provide only limited information, typically restricted to coordination ratios and ion-pair distributions, without revealing the actual size and mass of solution complexes. Here, in this study, we introduce an average hydrodynamic radius (AHR) analysis based on internally referenced DOSY NMR, which enables direct estimation of the average volume and molecular weight of lithium–solvent complexes in solution. Using LiFSI–EMC and LiFSI–EMC–TTE electrolytes, we demonstrate that the onset of effective lithium metal stabilization and aluminum corrosion suppression coincides with the formation of very large complexes, whose average volume exceeds 300 times that of free EMC molecules. This finding supports a new “blocking mechanism,” wherein bulky solvated complexes impede direct solvent access to reactive surfaces. The AHR analysis thus not only clarifies the fundamental origin of HCE and LHCE effectiveness, but also provides a broadly applicable experimental framework for probing complex solvation structures and guiding rational electrolyte design.

Concentrated electrolytes↗
DOE OSTI2024

Trace LiBF 4 Enabling Robust LiF-Rich Interphase for Durable Low-Temperature Lithium-Ion Pouch Cells

Lithium-ion batteries (LIBs) with electrolytes containing lithium tetrafluoroborate (LiBF 4 ) can achieve large capacity retention under low temperature, but the accompanying rapid capacity decay inhibits commercialization. Here, in this study, the impact of LiBF 4 as a supplemental salt to LiPF 6 is systematically investigated using low ethylene carbonate (EC)-content electrolytes, along with a low-melting-point cosolvent. It is found that rational adjustment of the amount of LiBF 4 could not only regulate the interactions of anions and solvents in Li + solvation sheaths but also tune the composition and morphology of solid electrolyte interphase (SEI). It is worth noting that electrolytes with trace amount of LiBF 4 (0.05 M) show synergetic interaction between PF 6 - and Li + and decreased interaction between EC and Li + , achieving a dense and LiF-rich SEI, which enables a 200 mAh pouch cell with less gas generation, long-lived cycling, and higher low-temperature capacity, simultaneously. This work provides new insight into utilizing trace LiBF 4 for stable interface construction of durable low-temperature LIBs.

25 ENERGY STORAGE↗
DOE OSTI2025

Halide segregation to boost all-solid-state lithium-chalcogen batteries

Mixing electroactive materials, solid-state electrolytes, and conductive carbon to fabricate composite electrodes is the most practiced but least understood process in all-solid-state batteries, which strongly dictates interfacial stability and charge transport. Here, we report on universal halide segregation at interfaces across various halogen-containing solid-state electrolytes and a family of high-energy chalcogen cathodes enabled by mechanochemical reaction during ultrahigh-speed mixing. Bulk and interface characterizations by multimodal synchrotron x-ray probes and cryo–transmission electron microscopy show that the in situ segregated lithium halide interfacial layers substantially boost effective ion transport and suppress the volume change of bulk chalcogen cathodes. Various all-solid-state lithium-chalcogen cells demonstrate utilization close to 100% and extraordinary cycling stability at commercial-level areal capacities.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Phosphate tolerance of nitrogen-coordinated-iron-carbon (FeNC) catalysts for oxygen reduction reaction: A size-related hindrance effect

The greatest challenges facing the large – scale commercialization of the intermediate temperature phosphoric acid fuel cell (PAFC) technology are: (i) the high cost of Pt catalyst that is required to overcome the slow kinetics of oxygen reduction reaction (ORR) on the PAFC cathode, and (ii) deactivation of the Pt catalyst by exposure to the phosphoric acid electrolyte. Inexpensive carbon-based materials, particularly iron- spectroscopy is used to explore the phenomenon of phosphate poisoning nitrogen-coordinated carbon supported catalysts (FeNC), are promising cathodes for PAFCs. The higher ORR activation energy and phosphate poisoning resistance of FeNC present a clear advantage over the Pt-based commercial catalysts that are easily susceptible to deactivation after exposure to phosphate anions. While the immunity of FeNC catalysts to phosphate anion poisoning has been reported previously, this work explores the counter-intuitive and conditional nature of this poisoning resistance based on the properties of the carbon support used in the preparation of the FeNC catalyst. Additionally, a combination of electrochemical measurements with characterization experiments performed using X-ray photoelectron spectroscopy, infrared spectroscopy and in-situ X-ray absorption on FeNC catalysts synthesized from two different carbon supports. Results from these studies reveal a “size-related hindrance effect” wherein the ORR active Fe centers in FeNC remain inaccessible to larger anions such as phosphate when the Fe sites are present deeper inside the pores of a carbon support with high porosity. However, FeNC catalyst is poisoned by phosphate anions when synthesized using a carbon support with low porosity. This work helps gain insights into the nature of active sites in FeNC catalysts that will be useful in designing precious-metal free ORR catalysts for intermediate temperature fuel cell technologies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

High voltage window electrolyte for supercapacitors

A supercapacitor according to the present invention includes a negative carbon-comprising electrode which does not intercalate sodium, and a positive carbon-comprising electrode. An electrolyte composition comprises sodium hexafluorophosphate and a non-aqueous solvent comprising at least one selected from the group consisting of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether. The supercapacitor has an electrochemical voltage window of from +0.0 V to 3.5 V (full cell voltage). The electrolyte has an electrochemical voltage window of from +0.05 V to 3.9 V vs. Na/Na+. A method of making and a method of operating a supercapacitor is also disclosed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

High voltage window electrolyte for supercapacitors

A supercapacitor according to the present invention includes a negative carbon-comprising electrode which does not intercalate sodium, and a positive carbon-comprising electrode. An electrolyte composition comprises sodium hexafluorophosphate and a non-aqueous solvent comprising at least one selected from the group consisting of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether. The supercapacitor has an electrochemical voltage window of from +0.0 V to 3.5 V (full cell voltage). The electrolyte has an electrochemical voltage window of from +0.05 V to 3.9 V vs. Na/Na+. A method of making and a method of operating a supercapacitor is also disclosed.

25 ENERGY STORAGE↗
DOE OSTI2020

Sweeping potential regulated structural and chemical evolution of solid-electrolyte interphase on Cu and Li as revealed by cryo-TEM

A fundamental understanding of solid-electrolyte interphase (SEI) is paramount importance for controlling the cycling performance of rechargeable lithium metal batteries. The structural and chemical evolution of SEI with respect to electrochemical operating condition remains barely established. Here we develop a unique method for imaging the evolution of SEI formed on the Cu foil under sweeping electrochemical potential. By using cryogenic TEM imaging combined with energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy electronic structure analyses, we reveal that, for the vinylene carbonate (VC)-free electrolyte, the SEI formed at 1.0 V is a monolithic amorphous structure, which evolves to amorphous matrix embedded with Li 2 O particles as the voltage decreases to 0 V. In the case of VC-containing electrolyte, the SEI is featured by an amorphous matrix with Li 2 O particles from 1.0 V to 0 V. The thickness of SEI formed on Cu foil increases with decreasing voltage. Associated with the localized charge modulation by the surface topographic feature and defects in the Cu foil, the SEI layer shows direct spatial correlation with these structural defects in the Cu. In addition, upon Li deposition, the SEI formed on the Li metal has similar thickness with, but different composition from the SEI formed on the Cu foil at 0 V. Furthermore, those results provide insight toward SEI engineering for enhanced cycling stability of Li metal.

25 ENERGY STORAGE↗
DOE OSTI2025

Reactive Suspension Electrolytes for Lithium Metal Batteries

Lithium metal batteries (LMBs) suffer from dendrite growth and capacity loss, which compromise safety and cycle life. Here, we present a simple reactive suspension electrolyte (RSE) strategy. When metal oxide (MO x ) nanoparticles are dispersed in the liquid electrolyte, in situ formation of Li 2 O and Li–M phases occurs at the lithium metal anode. By studying two different types of RSEs, Type 1 RSEs (i.e., CuO RSE) without metal-Li alloying and Type 2 RSEs (i.e., ZnO RSE and In 2 O 3 RSE) with metal-Li alloying capability, we elucidate the roles of each reaction compound. Here, we find that Li 2 O can improve reversibility of Li metal anode by stabilizing the interphase while Li–M alloy phases guide uniform Li metal plating. Compared to the carbonate-type reference electrolyte, RSEs demonstrate reduced nucleation overpotential, lower interfacial impedance, and higher Coulombic efficiency, leading to an extended cycle life in Li|Li 1 Ni 0.8 Co 0.1 Mn 0.1 O 2 full cells.

Lee, Junyoung [Stanford Univ., CA (United States)]↗