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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1998

Development of High Conductivity Lithium-Ion Electrolytes for Low Temperature Cell Applications

NASA has continued interest in developing power sources which are capable of operating at low temperatures (-20 C and below) to enable future missions, such as the Mars Rover and Lander. Thus, under a program sponsored by the Mars Exploration Program, we have been involved in developing Li-ion batteries with improved low temperature performance. To accomplish this task, the focus of the research has been upon the development of advanced electrolyte systems with improved low temperature properties. This had led to the identification of a carbonate-based electrolyte, consisting of 1.0 M LiPF6 in EC + DEC + DMC (33:33:34), which has been shown to have excellent performance at -20 C in Li-ion AA-size prototype cells. Other groups are also actively engaged in developing electrolytes which can result in improved low temperature performance of Li-ion cells, including Polystor, Yardney, and Covalent. In addition to developing cells capable of operation at -20 C, there is continued interest in systems which can successfully operate at even lower temperatures (less than -30 C) and at high discharge rates (greater than C/2). Thus, we are currently focusing upon developing advanced electrolytes which are highly conductive at low temperatures and will result in cells capable of operation at -40 C. One approach to improve the low temperature conductivity of ethylene carbonate-based electrolytes involves adding co-solvents which will decrease the viscosity and extend the liquid range. Candidate solvent additives include formates, acetates, cyclic and aliphatic ethers, lactones, as well as other carbonates. Using this approach, we have prepared a number of electrolytes which contain methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), ethyl proprionate (EP), and 1,2-dimethoxyethane (DME), some of which have been characterized and reported. Other groups have also reported electrolytes based on mixtures of carbonates and acetates. In the present study, electrolytes which have been identified to have good low temperature conductivity and stability were incorporated into lithium-graphite cells for evaluation. Using various electrochemical methods, including ac impedence and DC micropolarization techniques, the film formation characteristics of graphite electrodes in contact with various lectrolyte formulations was investigated.

Smart, M. C.↗
NASA NTRS2006

Assessment of Lithium-based Battery Electrolytes Developed under the NASA PERS Program

Recently, NASA formally completed the Polymer Energy Rechargeable System (PERS) Program, which was established in 2000 in collaboration with the Air Force Research Laboratory (AFRL) to support the development of polymer-based, lithium-based cell chemistries and battery technologies to address the next generation of aerospace applications and mission needs. The goal of this program was to ultimately develop an advanced, space-qualified battery technology, which embodied a solid polymer electrolyte (SPE) and complementary components, with improved performance characteristics that would address future aerospace battery requirements. Programmatically, the PERS initiative exploited both interagency collaborations to address common technology and engineering issues and the active participation of academia and private industry. The initial program phases focused on R&D activities to address the critical technical issues and challenges at the cell level. A variety of cell and polymeric electrolyte concepts were pursued as part of the development efforts undertaken at numerous governmental, industrial and academic laboratories. Numerous candidate electrolyte materials were developed, synthesized and optimized for evaluation. Utilizing the component screening facility and the "standardized" test procedures developed at the NASA Glenn Research Center, electrochemical screening and performance evaluations of promising candidate materials were completed. This overview summarizes test results for a variety of candidate electrolyte materials that were developed under the PERS Program. Electrolyte properties are contrasted and compared to the original project goals, and the strengths and weaknesses of the electrolyte chemistries are discussed. Limited cycling data for full-cells using lithium metal and vanadium oxide electrodes are also presented. Based on measured electrolyte properties, the projected performance characteristics and temperature limitations of batteries utilizing the advanced electrolytes and components have been estimated. Limitations for the achievement of practical performance levels are also discussed, as well as needs for future research and development.

Bennett, William R.↗
NASA NTRS2010

Lithium-Ion Electrolytes Containing Phosphorous-Based, Flame-Retardant Additives

Future NASA missions aimed at exploring Mars, the Moon, and the outer planets require rechargeable batteries that can operate over a wide temperature range (-60 to +60 C) to satisfy the requirements of various applications. In addition, many of these applications will require improved safety, due to their use by humans. Currently, the state-of-the-art lithium-ion (Li-ion) system has been demonstrated to operate over a wide range of temperatures (-40 to +40 C); however, abuse conditions can often lead to cell rupture and fire. The nature of the electrolyte can greatly affect the propensity of the cell/battery to catch fire, given the flammability of the organic solvents used within. Li-ion electrolytes have been developed that contain a flame-retardant additive in conjunction with fluorinated co-solvents to provide a safe system with a wide operating temperature range. Previous work incorporated fluorinated esters into multi-component electrolyte formulations, which were demonstrated to cover a temperature range from 60 to +60 C. This work was described in Fluoroester Co-Solvents for Low-Temperature Li+ Cells (NPO-44626), NASA Tech Briefs, Vol. 33, No. 9 (September 2009), p. 37; and Optimized Li-Ion Electrolytes Con tain ing Fluorinated Ester Co-Solvents (NPO-45824), NASA Tech Briefs, Vol. 34, No. 3 (March 2010), p. 48. Other previous work improved the safety characteristics of the electrolytes by adding flame-retardant additives such as triphenyl phosphate (TPhPh), tri-butyl phosphate (TBuPh), triethyl phosphate (TEtPh), and bis(2,2,2-trifluoroethyl) methyl phosphonate (TFMPo). The current work involves further investigation of other types of flame-retardant additives, including tris(2,2,2-trifluoroethyl) phosphate, tris(2,2,2-trifluoroethyl) phosphite, triphenylphosphite, diethyl ethylphosphonate, and diethyl phenylphosphonate added to an electrolyte composition intended for wide operating temperatures. In general, many of the formulations investigated in this study displayed good performance over a wide temperature range, good cycle life characteristics, and are expected to have improved safety characteristics, such as low flammability. Of the electrolytes studied, 1.0 M LiPF6 in EC+EMC+DEP (20:75:5 v/v %) and 1.0 M LiPF6 in EC+EMC+DPP (20:75:5 v/v %) displayed the best operation at low temperatures, whereas the electrolyte containing triphenylphosphite displayed the best cycle life performance compared to the baseline solution. It is anticipated that further improvements can be made to the life characteristics with the incorporation of a SET promoters (such as VC, vinylene carbonate), which will likely inhibit the decomposition of the flame-retardant additives.

Smart, Marshall C.↗
NASA NTRS2011

Optimized Li-Ion Electrolytes Containing Triphenyl Phosphate as a Flame-Retardant Additive

A number of future NASA missions involving the exploration of the Moon and Mars will be human-rated and thus require high-specific-energy rechargeable batteries that possess enhanced safety characteristics. Given that Li-ion technology is the most viable rechargeable energy storage device for near-term applications, effort has been devoted to improving the safety characteristics of this system. There is also a strong desire to develop Li-ion batteries with improved safety characteristics for terrestrial applications, most notably for hybrid electric vehicle (HEV) and plug-in hybrid electric vehicle (PHEV) automotive applications. Therefore, extensive effort has been devoted recently to developing non-flammable electrolytes to reduce the flammability of the cells/battery. A number of electrolyte formulations have been developed, including systems that (1) incorporate greater concentrations of the flame-retardant additive (FRA); (2) use di-2,2,2-trifluoroethyl carbonate (DTFEC) as a co-solvent; (3) use 2,2,2- trifluoroethyl methyl carbonate (TFEMC); (4) use mono-fluoroethylene carbonate (FEC) as a co-solvent and/or a replacement for ethylene carbonate in the electrolyte mixture; and (5) utilize vinylene carbonate as a "SEI promoting" electrolyte additive, to build on the favorable results previously obtained. To extend the family of electrolytes developed under previous work, a number of additional electrolyte formulations containing FRAs, most notably triphenyl phosphate (TPP), were investigated and demonstrated in experimental MCMB (mesocarbon micro beads) carbon- LiNi(0.8)Co(0.2)O2 cells. The use of higher concentrations of the FRA is known to reduce the flammability of the electrolyte solution, thus, a concentration range was investigated (i.e., 5 to 20 percent by volume). The desired concentration of the FRA is the highest amount tolerable without adversely affecting the performance in terms of reversibility, ability to operate over a wide temperature range, and the discharge rate capability. The use of fluorinated carbonates, much in the same manner as the incorporation of fluorinated ester-based solvents, was employed to reduce the inherent flammability of mixtures. Thus, electrolyte formulations that embody both approaches are anticipated to have much lower flammability, resulting in enhanced safety.

Smart, Marshall C.↗
NASA NTRS2012

Wide Operating Temperature Range Electrolytes for High Voltage and High Specific Energy Li-Ion Cells

A number of electrolyte formulations that have been designed to operate over a wide temperature range have been investigated in conjunction with layered-layered metal oxide cathode materials developed at Argonne. In this study, we have evaluated a number of electrolytes in Li-ion cells consisting of Conoco Phillips A12 graphite anodes and Toda HE5050 Li(1.2)Ni(0.15)Co(0.10)Mn(0.55)O2 cathodes. The electrolytes studied consisted of LiPF6 in carbonate-based electrolytes that contain ester co-solvents with various solid electrolyte interphase (SEI) promoting additives, many of which have been demonstrated to perform well in 4V systems. More specifically, we have investigated the performance of a number of methyl butyrate (MB) containing electrolytes (i.e., LiPF6 in ethylene carbonate (EC) + ethyl methyl carbonate (EMC) + MB (20:20:60 v/v %) that contain various additives, including vinylene carbonate, lithium oxalate, and lithium bis(oxalato)borate (LiBOB). When these systems were evaluated at various rates at low temperatures, the methyl butyrate-based electrolytes resulted in improved rate capability compared to cells with all carbonate-based formulations. It was also ascertained that the slow cathode kinetics govern the generally poor rate capability at low temperature in contrast to traditionally used LiNi(0.80)Co(0.15)Al(0.05)O2-based systems, rather than being influenced strongly by the electrolyte type.

Li-ion Battery↗
DOE OSTI2025

Insight Into Sulfur‐Containing Additive to Boost Anti‐Oxidation Ability of the Ether‐Based Electrolyte for Sodium‐Ion Full Batteries

Ether-based electrolytes are considered as promising candidates for sodium-ion batteries (SIBs) due to their high ionic conductivity and good compatibility with hard carbon (HC) anode. However, they suffer from poor anti-oxidative ability with unstable cathode electrolyte interface, inducing successive electrolyte decomposition and rapid capacity fading. Herein, the sulfur-containing additive (1,3-propanediol cyclic sulfate, PCS) is introduced to boost the stability of the electrode-electrolyte interface (EEI) in ether-based electrolyte. PCS largely participates in the inner Na + sheath, causing more diglyme (G2) molecules and fewer PF 6 - anions to occupy the inner Na + solvation sheath, avoiding the decomposition of G2 molecules at high operation voltage. Moreover, PCS is beneficial for simultaneously constructing thin and robust sulfur-containing EEI on both Prussian blue (PB) cathode and HC anode, maintaining the structural stability of PB and alleviating the dissolution of transition metals. These enable PB||HC pouch cells to deliver a capacity retention of 60.3% after 400 cycles, significantly higher than the 32.1% in PCS-free electrolytes. In conclusion, this work discloses the underlying mechanism of PCS to evoke the anti-oxidation ability of ether-based electrolyte and provides a promising method for realizing advanced sodium-ion full cells.

anti-oxidation ability↗
DOE OSTI2025

Designing Moderately‐Solvating Electrolytes for High‐Performance Lithium–Sulfur Batteries

New electrolytes are critical for high‐energy lithium (Li)–sulfur (S) batteries (LSBs) to ensure their stability against Li metal anode and polysulfides (PSs) shuttling which hinder the large‐scale application of LSBs. In this study, the design principle of moderately solvating electrolytes (MSEs) for LSBs is demonstrated by using a multiple‐solvent system comprising of a highly solvating solvent, a weakly solvating solvent, and a non‐solvating solvent to create a well‐balanced electrolyte system. This resulting electrolyte significantly improves the cycle life of LSBs, achieving 300 cycles, which is twice as long as that of similar cells with the conventional electrolyte and it also ensures stable calendar life for at least seven months. The optimal MSE forms robust passivation layers enhancing the structural integrity of both S and Li metal electrodes after cycling. These virtues effectively hinder parasitic side reactions and self‐discharge behavior of LSBs. This electrolyte design principle is versatile and can be applied to other battery chemistries, providing a potential path toward the development of a more efficient and stable battery system. By addressing key challenges such as the instability of electrodes and shuttling of polysulfides, this electrolyte approach offers promising solutions for advancing LSB technology.

25 ENERGY STORAGE↗
DOE OSTI2024

Making Plasticized Polymer Electrolytes Stable Against Sodium Metal for High‐Energy Solid‐State Sodium Batteries

Solid polymer electrolytes based on plastic crystals are promising for solid-state sodium metal (Na 0 ) batteries, yet their practicality has been hindered by the notorious Na 0 -electrolyte interface instability issue, the underlying cause of which remains poorly understood. Here, in this study, by leveraging a model plasticized polymer electrolyte based on conventional succinonitrile plastic crystals, we uncover its failure origin in Na 0 batteries is associated with the formation of a thick and non-uniform solid electrolyte interphase (SEI) and whiskery Na 0 nucleation/growth. Furthermore, we design a new additive-embedded plasticized polymer electrolyte to manipulate the Na 0 deposition and SEI formulation. For the first time, we demonstrate that introducing fluoroethylene carbonate (FEC) additive into the succinonitrile-plasticized polymer electrolyte can effectively protect Na 0 against interfacial corrosion by facilitating the growth of dome-like Na 0 with thin, amorphous, and fluorine-rich SEIs, thus enabling significantly improved performances of Na//Na symmetric cells (1,800 h at 0.5 mA cm −2 ) and Na//Na 3 V 2 (PO 4 ) 3 full cells (93.0 % capacity retention after 1,200 cycles at 1 C rate in coin cells and 93.1 % capacity retention after 250 cycles at C/3 in pouch cells at room temperature). Our work provides valuable insights into the interfacial failure of plasticized polymer electrolytes and offers a promising solution to resolving the interfacial instability issue.

25 ENERGY STORAGE↗
DOE OSTI2024

Electrolyte–Electrocatalyst Interfacial Effects of Polymeric Materials for Tandem CO 2 Capture and Conversion Elucidated Using In Situ Electrochemical AFM

Integrating CO 2 capture and electrochemical conversion has been proposed as a strategy to reduce the net energy required for CO 2 regeneration in traditional CO 2 capture and conversion schemes and can be coupled with carbon-free renewable electricity. Polyethylenimine (PEI)-based materials have been previously studied as CO 2 capture materials and can be integrated in these reactive capture processes. PEI-based electrolytes have been found to significantly increase the CO 2 loading, and impact selectivity and rate of product formation when compared to the conventional aqueous electrolytes. However, the influence of these materials at the catalyst–electrode interface is currently not well understood. In this study, PEI-based electrolytes were prepared and their impact on the morphology of a silver electrode performing electrochemical CO 2 reduction (CO 2 R) was studied using in situ electrochemical atomic force microscopy (EC-AFM). The presence of PEI on the electrode surface could be distinguished based on nanomechanical properties (DMT modulus), and changes were observed as negative polarization was applied, revealing a reorganization of the PEI chains due to electrostatic interactions. These changes were impacted by the electrolyte composition, including the addition of supporting electrolyte KHCO 3 salt, as well as CO 2 captured by the PEI-based electrolyte, which minimized the change in surface mechanical properties and degree of PEI alignment on the electrode surface. The changes in surface mechanical properties were also dependent on the PEI polymer length, with higher molecular weight PEI showing different reconfiguration than the shorter polymer brushes. The study highlights that the choice of polymer material, the electrolyte composition, and CO 2 captured impact the nearelectrode environment, which has implications for CO 2 R, and presents EC-AFM as a new tool that can be used to probe the dynamic behavior of these interfaces during electrocatalysis.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Quantitative Analysis of the Semiconductor–Electrolyte Interface Using Cyclic Voltammetry Measurements

Small changes in the chemical potential at a semiconductor interface can result in dramatic changes to the space-charge layer that underpins applications in the electronic and photovoltaic industries as well as in photoelectrochemical cells for fuel production. There has hence been great interest in techniques that directly probe the space-charge layer, yet many fail at the semiconductor–electrolyte interface due to the potential drop in the electric double-layer region of the electrolyte. This article demonstrates that photovoltages, obtained from straightforward cyclic voltammetry measurements, provide an experimental and quantitative approach for characterizing the semiconductor–electrolyte interface. Key parameters accessible through this approach include the flat-band potential ( E fb ), the fraction of the total potential that drops across the space-charge layer (γ sc ) and the electric double layer, as well as the surface recombination lifetime (τ s ). Here, we report photovoltage measurements for p -type Si(111) photoelectrodes in contact with electrolytes containing redox-active species with a range of known reduction potentials that exceed the 1.1 eV bandgap. In tetrabutylammonium [NBu 4 ] + electrolyte, the flat-band potential determined for hydrogen-terminated ( p -Si–H), methyl-terminated ( p -Si–CH 3 ), and chemically oxidized ( p -Si–cSiO x ) surfaces were −0.02, −0.31, and 0.30 V vs Fc +/0 , respectively, agreeing well with expected shifts arising from surface dipole modifications. The quantitative analysis also reveals that 67% of the applied bias drops across the space-charge layer for p -Si–H, 73% for p -Si–CH 3 , and only 44% for p -Si–cSiO x . The remaining potential drop is attributed to the interfacial surface layer, which consists of a molecular dipole or oxide overlayer, and the Helmholtz layer within the electrolyte. When the larger [NBu 4 ] + electrolyte was replaced with Li + , the flat-band position showed minimal changes, but the fraction of the potential drop across the space-charge layer increased significantly, consistent with the small cation altering the structure of the electric double layer.

electrolytes↗
DOE OSTI2024

Beyond the Debye–Hückel limit: Toward a general theory for concentrated electrolytes

The phenomenon of underscreening in concentrated electrolyte solutions leads to a larger decay length of the charge–charge correlation than the prediction of Debye–Hückel (DH) theory and has found a resurgence of both theoretical and experimental interest in the chemical physics community. To systematically understand and investigate this phenomenon in electrolytes requires a theory of concentrated electrolytes to describe charge–charge correlations beyond the DH theory. We review the theories of electrolytes that can transition from the DH limit to concentrations where charge correlations dominate, giving rise to underscreening and the associated Kirkwood Transitions (KTs). In this perspective, we provide a conceptual approach to a theoretical formulation of electrolyte solutions that exploits the competition between molecular-informed short-range (SR) and long-range interactions. We demonstrate that all deviations from the DH limit for real electrolyte solutions can be expressed through a single function ΣQ that can be determined both theoretically and numerically. Importantly, ΣQ can be directly related to the details of SR interactions and, therefore, can be used as a tool to understand how differences in representations of interaction can influence collective effects. The precise function form of ΣQ can be inferred through a Gaussian field theory of both the number and charge densities. The resulting formulation is validated by experiment and can accurately describe the collective phenomenon of screening in concentrated bulk electrolytes. Importantly, the Gaussian field theory predictions of the screening lengths appear to be less than ∼1 nm at concentrations above KTs.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Lithium Dendrite-Free Li 7 N 2 I-LiOH Solid Electrolytes for High Energy Lithium Batteries

All-solid-state lithium batteries (ASSLBs) hold great potential to improve the safety and energy density of today’s lithium-ion batteries by using non-flammable inorganic solid electrolytes. Solid electrolytes (SEs) are believed to prevent Li dendrite growth because of high mechanical strength and high Li+ transference numbers. Significant advances in SE have been achieved, among which, Li7La3Zr2O12 (LLZO) and Li2S–P2S5 (LPS) are the most promising SEs for bulk-type solid-state lithium batteries because of high ionic conductivities (>10-4 S/cm2). However, in contrast to our expectations, the growth of lithium dendrites is not suppressed but is facilitated in LLZOs and LPSs regardless of dopants, porosity, and crystallinity of the electrolytes. Despite the unity Li transference number and over two-times of shear modulus than that of Li metal, the critical current densities for Li plating and stripping in these SEs are less than 1.0 mA cm-2, which is one-fourth to one-tenth of that in liquid electrolytes at room temperature. The incompatibility between LLZO and LPS with Li metal seriously limits the energy density of all-solid-state batteries. The mechanism for lithium dendrite formation and growth in SEs are still disputable. Lack of understanding of the Li dendrite formation mechanism seriously impeded the development of solid-state lithium batteries. The development of the criterion for Li dendrite suppression is essential for the success of solid electrolyte lithium batteries. In this project, a criterion for Li dendrite suppression will be developed through thermodynamics and kinetics analysis of lithium dendrite nucleation/growth, which will guide the solid-state electrolyte design. Li7N2I-LiOH, Li5NI2-LiOH and Li3YCl6 solid electrolyte with high ionic conductivity and low electronic conductivity were used to validate the criterion for lithium dendrite suppression. Different surface modifications were also explored to enhance the dendrite suppression capability of SSEs.

25 ENERGY STORAGE↗
NASA NTRSDate not supplied

Molten Salt Electrolytes: Computational Analysis of Transport, Electrochemical Properties and Designing New Mixtures

Electric aircraft propulsion has gained a traction over the last decade due to possible high-energy density electrochemistries with reasonable cycle life and identification of non-flammable chemistries that can guarantee much better safety. Commercial Li-ion batteries cannot reach such high capacities because of weight limitations that arise from the widely used intercalation electrodes. Also, use of organic electrolytes make them highly susceptible to fire on exposure to air and humidity. Currently, use of Lithium metal anode along with conversion electrochemistries such as Li-O2 and Li-S are being pursued to achieve such high energy densities. Safer inorganic solid-state electrolytes, recently discovered Water-in-Salt electrolytes, molten salt electrolytes are some of the alternatives being pursued for a safer/non-flammable battery. Of these safer alternatives, molten-salt electrolytes offer some attractive properties: liquid at operating temperatures resulting in better electrode-wetting, stable interface with Li-metal anodes and good ionic conductivity; their only drawback being high operating temperatures. In this talk, we will discuss some of the computational studies, driven via atomistic simulations, of the properties of molten-salt electrolytes including transport mechanism and interface stability. We will also discuss predicting electrochemical properties of these high-temperature electrolytes. Further, we will discuss a thermodynamic approach to predicting new molten-salt eutectics with lower melting points.

Molten Salt Electrolytes↗
DOE OSTI2024

Polysilaketals: High‐Performance Polyether‐Based Electrolytes with Tunable Disubstituted Silane Linkers

Abstract Polymer electrolytes exhibit higher energy density and improved safety in lithium‐ion batteries relative to traditionally used liquid electrolytes but are currently limited by their lower electrochemical performance. Aiming to access polymer electrolytes with competitive electrochemical properties, we developed the anionic ring‐opening polymerization (AROP) of cyclic silaketals to synthesize amorphous silicon‐containing polyether‐based electrolytes with varying substituent bulk of the general formula [OSi(R) 2 (CH 2 CH 2 O) 2 ] n (R=alkyl, phenyl). As opposed to previously reported uncontrolled polycondensation routes toward low molecular weight polysilaketals, AROP allows access to targeted molecular weights above the entanglement threshold of the polymers. The polysilaketal with the lowest steric bulk (P(OSi Me,Me ‐2EO)) exceeds the conductivity of poly(ethylene oxide) (PEO), a leading polymer electrolyte. To the best of our knowledge, this is the first solid polymer electrolyte to achieve this benchmark. Steric bulk in polysilaketals was found to impart stability and two bulkier polysilaketals, P(OSi Et,Et ‐2EO) and P(OSi Me,Ph ‐2EO), exhibited higher current fractions than PEO over a wide range of salt loadings. Moreover, the efficacy of P(OSi Et,Et ‐2EO) was competitive with that of PEO. Taken together, the tunable and competitive electrochemical properties of polysilaketals validate the systematic incorporation of silyl groups as a strategy to access high performance polymer electrolytes.

Rugh, Haley J.↗
DOE OSTI2025

Polysilaketals: High‐Performance Polyether‐Based Electrolytes with Tunable Disubstituted Silane Linkers

Polymer electrolytes exhibit higher energy density and improved safety in lithium-ion batteries relative to traditionally used liquid electrolytes but are currently limited by their lower electrochemical performance. Aiming to access polymer electrolytes with competitive electrochemical properties, we developed the anionic ring-opening polymerization (AROP) of cyclic silaketals to synthesize amorphous silicon-containing polyether-based electrolytes with varying substituent bulk of the general formula [OSi(R)2(CH2CH2O)2]n (R=alkyl, phenyl). As opposed to previously reported uncontrolled polycondensation routes toward low molecular weight polysilaketals, AROP allows access to targeted molecular weights above the entanglement threshold of the polymers. The polysilaketal with the lowest steric bulk (P(OSiMe,Me-2EO)) exceeds the conductivity of poly(ethylene oxide) (PEO), a leading polymer electrolyte. To the best of our knowledge, this is the first solid polymer electrolyte to achieve this benchmark. Steric bulk in polysilaketals was found to impart stability and two bulkier polysilaketals, P(OSiEt,Et-2EO) and P(OSiMe,Ph-2EO), exhibited higher current fractions than PEO over a wide range of salt loadings. Moreover, the efficacy of P(OSiEt,Et-2EO) was competitive with that of PEO. Taken together, the tunable and competitive electrochemical properties of polysilaketals validate the systematic incorporation of silyl groups as a strategy to access high performance polymer electrolytes.

Rugh, Haley J↗
DOE OSTI2025

Highly Stable and Conductive 1,3‐Dioxolane/Hydrocarbon Based Electrolyte Solvent for Advanced Lithium‐Sulfur Batteries

Abstract Developing effective electrolytes is crucial for boosting the performance of Lithium‐Sulfur (LiS) rechargeable battery. Recent improvements in electrolyte formulations have enhanced cyclability by increasing electrochemical stability at the electrode interfaces. However, achieving both high ionic conductivity (σ) and stability at these interfaces simultaneously remains a significant challenge. In this study, we utilized a strategy to suppress polysulfide dissolution by employing a mixture of 1,3‐dioxolane (DOL) and hydrocarbon solvents with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) electrolyte salt. Compared to the conventional electrolyte solution, which is 1 M LiTFSI salt in a 50/50 vol % mixture of DOL and dimethoxy ethane (DME), the LiTFSI electrolyte with DOL/hydrocarbon solvents demonstrate better cycling stability, compatibility with the Li‐metal anode, and a high specific discharge capacity (Csp). Among the various DOL/hydrocarbon and LiTFSI electrolyte salts, the combination of DOL and n‐hexane, a linear hydrocarbon, with LiTFSI electrolyte salt, (DnH40LiTFSI) exhibits remarkable σ (6.5×10 −3 S/cm at 30 °C), compatibility with the Li‐metal anode, an initial Csp of ca. 1264 mAh/g, cycling stability (Csp and Coulombic efficiency are 811 mAh/g and 98.09 % after 120 cycles) at 0.1 C by forming a good protective layer on the Li‐metal surface and preventing polysulfide dissolution.

Ahmed, Faiz↗
DOE OSTI2026

Distinct Melt Infusion Architectures of Antiperovskite Solid Electrolytes

Antiperovskite solid electrolytes are an emerging class of lithium‐ion conductors distinguished by their unusually low melting points, enabling scalable, low‐temperature processing routes not accessible to most solid electrolytes. In this work, we synthesize phase‐pure chloride (Cl), bromide (Br), and mixed halide (ClBr) variants of antiperovskites and investigate their ionic conductivities in both powder and hot‐pressed forms. Hot pressing significantly enhances conductivity across all compositions, while energy‐dispersive X‐ray spectroscopy (EDS) of the mixed halide system reveals halide surface migration during densification. We further investigate the melt‐infiltration behavior of these electrolytes into substrates relevant to solid‐state battery architectures, including Al and Cu current collectors, conventional NMC and LFP cathodes, and a foamed NMC cathode with a highly porous architecture. The foamed cathode enables deep and uniform electrolyte penetration, highlighting the role of electrode architecture in facilitating melt infiltration. Across all substrates, electrolyte halide chemistry strongly influences wetting behavior, penetration depth, and resulting microstructural morphology. Together, these results establish clear processing–structure relationships for melt‐infiltrated antiperovskite solid electrolytes and demonstrate how electrolyte chemistry and electrode architecture govern interfacial morphology during integration, providing practical guidelines for processing and structural design in solid‐state battery systems.

antiperovskite↗
DOE OSTI2025

Electrochemical Oxidation in Garnet-Type Solid Electrolyte by Formation of Point Defects

All-solid-state batteries hold greater promise for improving safety and energy density over conventional battery technology employing organic liquid electrolytes. One of the required features of a Li + conducting solid electrolyte is electrochemical stability, attained thermodynamically or kinetically, within the targeted operating voltage and temperature ranges. Therefore, understanding of the oxidative or reductive degradation mechanism is important to allow the design of stable solid electrolyte materials. This work contributes to building an understanding of the oxidative degradation mechanism in lithium solid electrolytes at cell operating conditions. Here, we have focused on resolving the oxidative decomposition mechanism of Al-doped lithium garnet Li 6.28 Al 0.24 La 3 Zr 2 O 12 (LLZO) as a state-of-the-art inorganic ceramic electrolyte. By combining experimental and computational analyses, we show that oxidation of LLZO occurs by simultaneous loss of oxygen and lithium from the structure, resulting in substoichiometric LLZO, at a moderate temperature (80 °C) and a high electrode potential (4.3 V vs Li/Li + ). Based on X-ray absorption and diffraction analyses, we find that the zirconium coordination shells in LLZO contract while the crystal structure experiences positive chemical strain upon electrochemical oxidation. The results from ex situ structural characterization of both the local structure and crystal symmetry are supported by a substoichiometric LLZO with lithium and oxygen vacancies, modeled by density functional theory (DFT) calculations. These chemical and structural changes in LLZO suppress effective lithium-ion conductivity by an order of magnitude. Formation of lithium and oxygen vacancies in LLZO upon electrochemical oxidation is different from prior thermodynamic predictions of phase decomposition of LLZO. The difference here is that the experiments were conducted at near-room temperature, which can hinder the kinetics of phase separation, and thus, the resultant LLZO solid electrolyte is still single-phase but substoichiometric in Li and O. In conclusion, these findings contribute an important degradation mechanism of the electrolyte, relevant for practical operational conditions of solid-state batteries.

36 MATERIALS SCIENCE↗