Dual-Solvent Li-Ion Solvation Enables High-Performance Li-Metal Batteries
Novel electrolyte designs to further enhance the lithium (Li) metal battery cyclability are highly desirable. Here, fluorinated 1,6-dimethoxyhexane (FDMH) is designed and synthesized as the solvent molecule to promote electrolyte stability with its prolonged -CF2 - backbone. Meanwhile, 1,2-dimethoxyethane is used as a co-solvent to enable higher ionic conductivity and much reduced interfacial resistance. Combining the dual-solvent system with 1 m lithium bis(fluorosulfonyl)imide (LiFSI), high Li-metal Coulombic efficiency (99.5%) and oxidative stability (6 V) are achieved. Using this electrolyte, 20 µm Li||NMC batteries are able to retain ≈80% capacity after 250 cycles and Cu||NMC anode-free pouch cells last 120 cycles with 75% capacity retention under ≈2.1 µL mAh-1 lean electrolyte conditions. Such high performances are attributed to the anion-derived solid-electrolyte interphase, originating from the coordination of Li-ions to the highly stable FDMH and multiple anions in their solvation environments. This work demonstrates a new electrolyte design strategy that enables high-performance Li-metal batteries with multisolvent Li-ion solvation with rationally optimized molecular structure and ratio.
View details for DOI 10.1002/adma.202008619
View details for Web of Science ID 000648495100001
View details for PubMedID 33969571
- Molecular design for electrolyte solvents enabling energy-dense and long-cycling lithium metal batteries NATURE ENERGY 2020
Design Principles of Artificial Solid Electrolyte Interphases for Lithium-Metal Anodes
Cell Reports Physical Science
2020; 1 (7): 100119
View details for DOI 10.1016/j.xcrp.2020.100119
- A Dynamic, Electrolyte-Blocking, and Single-Ion-Conductive Network for Stable Lithium-Metal Anodes JOULE 2019; 3 (11): 2761–76
- Organic Semiconducting Alloys with Tunable Energy Levels JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 2019; 141 (16): 6561–68
- Influence of solution-state aggregation on conjugated polymer crystallization in thin films and microwire crystals GIANT 2021; 7
Potentiometric Measurement to Probe Solvation Energy and Its Correlation to Lithium Battery Cyclability.
Journal of the American Chemical Society
The electrolyte plays a critical role in lithium-ion batteries, as it impacts almost every facet of a battery's performance. However, our understanding of the electrolyte, especially solvation of Li+, lags behind its significance. In this work, we introduce a potentiometric technique to probe the relative solvation energy of Li+ in battery electrolytes. By measuring open circuit potential in a cell with symmetric electrodes and asymmetric electrolytes, we quantitatively characterize the effects of concentration, anions, and solvents on solvation energy across varied electrolytes. Using the technique, we establish a correlation between cell potential (Ecell) and cyclability of high-performance electrolytes for lithium metal anodes, where we find that solvents with more negative cell potentials and positive solvation energies-those weakly binding to Li+-lead to improved cycling stability. Cryogenic electron microscopy reveals that weaker solvation leads to an anion-derived solid-electrolyte interphase that stabilizes cycling. Using the potentiometric measurement for characterizing electrolytes, we establish a correlation that can guide the engineering of effective electrolytes for the lithium metal anode.
View details for DOI 10.1021/jacs.1c03868
View details for PubMedID 34184873
- A Stretchable and Highly Conductive Sulfonic Pendent Single-Ion Polymer Electrolyte Derived from Multifunctional Tri-Block Polyether ACS APPLIED POLYMER MATERIALS 2021; 3 (6): 3254-3263
- Corrosion of lithium metal anodes during calendar ageing and its microscopic origins NATURE ENERGY 2021
- Efficient Lithium Metal Cycling over a Wide Range of Pressures from an Anion-Derived Solid-Electrolyte Interphase Framework ACS ENERGY LETTERS 2021; 6 (2): 816–25
- Polymers in Lithium-Ion and Lithium Metal Batteries ADVANCED ENERGY MATERIALS 2021
Monolithic optical microlithography of high-density elastic circuits.
Science (New York, N.Y.)
2021; 373 (6550): 88-94
Polymeric electronic materials have enabled soft and stretchable electronics. However, the lack of a universal micro/nanofabrication method for skin-like and elastic circuits results in low device density and limited parallel signal recording and processing ability relative to silicon-based devices. We present a monolithic optical microlithographic process that directly micropatterns a set of elastic electronic materials by sequential ultraviolet light-triggered solubility modulation. We fabricated transistors with channel lengths of 2 micrometers at a density of 42,000 transistors per square centimeter. We fabricated elastic circuits including an XOR gate and a half adder, both of which are essential components for an arithmetic logic unit. Our process offers a route to realize wafer-level fabrication of complex, high-density, and multilayered elastic circuits with performance rivaling that of their rigid counterparts.
View details for DOI 10.1126/science.abh3551
View details for PubMedID 34210882
- Tuning the Mechanical Properties of a Polymer Semiconductor by Modulating Hydrogen Bonding Interactions CHEMISTRY OF MATERIALS 2020; 32 (13): 5700–5714
A New Class of Ionically Conducting Fluorinated Ether Electrolytes with High Electrochemical Stability.
Journal of the American Chemical Society
Increasing battery energy density is greatly desired for applications such as portable electronics and transportation. However, many next-generation batteries are limited by electrolyte selection because high ionic conductivity and poor electrochemical stability are typically observed in most electrolytes. For example, ether-based electrolytes have high ionic conductivity but are oxidatively unstable above 4 V, which prevents the use of high-voltage cathodes that promise higher energy densities. In contrast, hydrofluoroethers (HFEs) have high oxidative stability but do not dissolve lithium salt. In this work, we synthesize a new class of fluorinated ether electrolytes that combine the oxidative stability of HFEs with the ionic conductivity of ethers in a single compound. We show that conductivities of up to 2.7 * 10-4 S/cm (at 30 °C) can be obtained with oxidative stability up to 5.6 V. The compounds also show higher lithium transference numbers compared to typical ethers. Furthermore, we use nuclear magnetic resonance (NMR) and molecular dynamics (MD) to study their ionic transport behavior and ion solvation environment, respectively. Finally, we demonstrate that this new class of electrolytes can be used with a Ni-rich layered cathode (NMC 811) to obtain over 100 cycles at a C/5 rate. The design of new molecules with high ionic conductivity and high electrochemical stability is a novel approach for the rational design of next-generation batteries.
View details for DOI 10.1021/jacs.9b11056
View details for PubMedID 32233433
Multivalent Assembly of Flexible Polymer Chains into Supramolecular Nanofibers.
Journal of the American Chemical Society
Polymeric materials in nature regularly employ ordered, hierarchical structures in order to perform unique and precise functions. Importantly, these structures are often formed and stabilized by the cooperative summation of many weak interactions as opposed to the independent association of a few strong bonds. Here, we show that synthetic, flexible polymer chains with periodically placed and directional dynamic bonds collectively assemble into supramolecular nanofibers when the overall molecular weight is below the polymer's critical entanglement molecular weight. This causes bulk films of long polymer chains to have faster dynamics than films of shorter polymer chains of identical chemical composition. The formation of nanofibers increases the bulk film modulus by over an order of magnitude and delays the onset of terminal flow by more than 100 °C, while still remaining solution processable. Systematic investigation of different polymer chain architectures and dynamic bonding moieties along with coarse-grained molecular dynamics simulations illuminate governing structure-function relationships that determine a polymer's capacity to form supramolecular nanofibers. This report of the cooperative assembly of multivalent polymer chains into hierarchical, supramolecular structures contributes to our fundamental understanding of designing biomimetic functional materials.
View details for DOI 10.1021/jacs.0c07651
View details for PubMedID 32901473
Decoupling of mechanical properties and ionic conductivity in supramolecular lithium ion conductors.
2019; 10 (1): 5384
The emergence of wearable electronics puts batteries closer to the human skin, exacerbating the need for battery materials that are robust, highly ionically conductive, and stretchable. Herein, we introduce a supramolecular design as an effective strategy to overcome the canonical tradeoff between mechanical robustness and ionic conductivity in polymer electrolytes. The supramolecular lithium ion conductor utilizes orthogonally functional H-bonding domains and ion-conducting domains to create a polymer electrolyte with unprecedented toughness (29.3 MJ m-3) and high ionic conductivity (1.2*10-4 S cm-1 at 25°C). Implementation of the supramolecular ion conductor as a binder material allows for the creation of stretchable lithium-ion battery electrodes with strain capability of over 900% via a conventional slurry process. The supramolecular nature of these battery components enables intimate bonding at the electrode-electrolyte interface. Combination of these stretchable components leads to a stretchable battery with a capacity of 1.1 mAh cm-2 that functions even when stretched to 70% strain. The method reported here of decoupling ionic conductivity from mechanical properties opens a promising route to create high-toughness ion transport materials for energy storage applications.
View details for DOI 10.1038/s41467-019-13362-4
View details for PubMedID 31772158
Dynamic single-ion-conductive network as a stable lithium metal artificial solid electrolyte interphase in carbonate electrolyte
AMER CHEMICAL SOC. 2019
View details for Web of Science ID 000525061504597
Scalable and facile preparation of SSNs for lithium metal stabilization
AMER CHEMICAL SOC. 2019
View details for Web of Science ID 000525061501099
Fine-Tuning of Crystal Packing and Charge Transport Properties of BDOPV Derivatives through Fluorine Substitution
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2015; 137 (50): 15947-15956
Molecular packing in organic single crystals greatly influences their charge transport properties but can hardly be predicted and designed because of the complex intermolecular interactions. In this work, we have realized systematic fine-tuning of the single-crystal molecular packing of five benzodifurandione-based oligo(p-phenylenevinylene) (BDOPV)-based small molecules through incorporation of electronegative fluorine atoms on the BDOPV backbone. While these molecules all exhibit similar column stacking configurations in their single crystals, the intermolecular displacements and distances can be substantially modified by tuning of the amounts and/or the positions of the substituent fluorine atoms. Density functional theory calculations showed that the subtle differences in charge distribution or electrostatic potential induced by different fluorine substitutions play an important role in regulating the molecular packing of the BDOPV compounds. Consequently, the electronic couplings for electron transfer can vary from 71 meV in a slipped stack to 201 meV in a nearly cofacial antiparallel stack, leading to an increase in the electron mobility of the BDOPV derivatives from 2.6 to 12.6 cm(2) V(-1) s(-1). The electron mobility of the five molecules did not show a good correlation with the LUMO levels, indicating that the distinct difference in charge transport properties is a result of the molecular packing. Our work not only provides a series of high-electron-mobility organic semiconductors but also demonstrates that fluorination is an effective approach for fine-tuning of single-crystal packing modes beyond simply lowering the molecular energy levels.
View details for DOI 10.1021/jacs.5b11114
View details for Web of Science ID 000367562800054
View details for PubMedID 26619351
A Cofacially Stacked Electron-Deficient Small Molecule with a High Electron Mobility of over 10 cm(2) V-1 s(-1) in Air
2015; 27 (48): 8051-8055
A strong, electron-deficient small molecule, F4 -BDOPV, has a lowest unoccupied molecular orbital (LUMO) level down to -4.44 eV and exhibits cofacial packing in single crystals. These features provide F4 -BDOPV with good ambient stability and large charge-transfer integrals for electrons, leading to a high electron mobility of up to 12.6 cm(2) V(-1) s(-1) in air.
View details for DOI 10.1002/adma.201503803
View details for Web of Science ID 000367839900019
View details for PubMedID 26501491