Li dendrite‐free growth is achieved by employing glass fiber with large polar functional groups as the interlayer of Li metal anode and separator to uniformly distribute Li ions. The evenly ...distributed Li ions render the dendrite‐free Li deposits at high rates (10 mA cm−2) and high lithiation capacity (2.0 mAh cm−2).
The lithium–sulfur (Li–S) battery is a promising high‐energy‐density storage system. The strong anchoring of intermediates is widely accepted to retard the shuttle of polysulfides in a working ...battery. However, the understanding of the intrinsic chemistry is still deficient. Inspired by the concept of hydrogen bond, herein we focus on the Li bond chemistry in Li–S batteries through sophisticated quantum chemical calculations, in combination with 7Li nuclear magnetic resonance (NMR) spectroscopy. Identified as Li bond, the strong dipole–dipole interaction between Li polysulfides and Li–S cathode materials originates from the electron‐rich donors (e.g., pyridinic nitrogen (pN)), and is enhanced by the inductive and conjugative effect of scaffold materials with π‐electrons (e.g., graphene). The chemical shift of Li polysulfides in 7Li NMR spectroscopy, being both theoretically predicted and experimentally verified, is suggested to serve as a quantitative descriptor of Li bond strength. These theoretical insights were further proved by actual electrochemical tests. This work highlights the importance of Li bond chemistry in Li–S cell and provides a deep comprehension, which is helpful to the cathode materials rational design and practical applications of Li–S batteries.
Lithium bond chemistry in Li–S batteries is probed by sophisticated quantum chemical calculations in combination with 7Li NMR spectroscopy. The chemical shift in 7Li NMR spectroscopy is suggested to be a quantitative descriptor of Li bond strength, propelling the advances in Li–S chemistry through materials genome design and high throughput screening.
Lithium–sulfur (Li–S) battery system is endowed with tremendous energy density, resulting from the complex sulfur electrochemistry involving multielectron redox reactions and phase transformations. ...Originated from the slow redox kinetics of polysulfide intermediates, the flood of polysulfides in the batteries during cycling induced low sulfur utilization, severe polarization, low energy efficiency, deteriorated polysulfide shuttle, and short cycling life. Herein, sulfiphilic cobalt disulfide (CoS2) was incorporated into carbon/sulfur cathodes, introducing strong interaction between lithium polysulfides and CoS2 under working conditions. The interfaces between CoS2 and electrolyte served as strong adsorption and activation sites for polar polysulfides and therefore accelerated redox reactions of polysulfides. The high polysulfide reactivity not only guaranteed effective polarization mitigation and promoted energy efficiency by 10% but also promised high discharge capacity and stable cycling performance during 2000 cycles. A slow capacity decay rate of 0.034%/cycle at 2.0 C and a high initial capacity of 1368 mAh g–1 at 0.5 C were achieved. Since the propelling redox reaction is not limited to Li–S system, we foresee the reported strategy herein can be applied in other high-power devices through the systems with controllable redox reactions.
Lithium–sulfur (Li–S) batteries have been intensively concerned to fulfill the urgent demands of high capacity energy storage. One of the major unsolved issues is the complex diffusion of lithium ...polysulfide intermediates, which in combination with the subsequent paradox reactions is known as the shuttle effect. Nanocarbon with homogeneous nonpolar surface served as scaffolding materials in sulfur cathode basically cannot afford a sufficient binding and confining effect to maintain lithium polysulfides within the cathode. Herein, a systematical density functional theory calculation of various heteroatoms‐doped nanocarbon materials is conducted to elaborate the mechanism and guide the future screening and rational design of Li–S cathode for better performance. It is proved that the chemical modification using N or O dopant significantly enhances the interaction between the carbon hosts and the polysulfide guests via dipole–dipole electrostatic interaction and thereby effectively prevents shuttle of polysulfides, allowing high capacity and high coulombic efficiency. By contrast, the introduction of B, F, S, P, and Cl monodopants into carbon matrix is unsatisfactory. To achieve the strong‐couple effect toward Li2Sx, the principles for rational design of doped carbon scaffolds in Li–S batteries to achieve a strong electrostatic dipole–dipole interaction are proposed. An implicit volcano plot is obtained to describe the dependence of binding energies on electronegativity of dopants. Moreover, the codoping strategy is predicted to achieve even stronger interfacial interaction to trap lithium polysulfides.
Lithium–sulfur (Li–S) batteries have been intensively studied to fulfill the urgent demands of high capacity energy storage. A systematic density functional theory calculation of various heteroatoms‐doped nanocarbon materials is conducted to elaborate the mechanism and guide the future screening and rational design of Li–S cathode for better performance. While B and F doping exhibit lower Eb than undoped carbon, N and O elements offer elevated binding energies with Li2Sx that form a strong anchoring effect to alleviate shuttle effect.
We demonstrate a novel preparative strategy for the well-controlled MnCo2O4.5@MnO2 hierarchical nanostructures. Both δ-MnO2 nanosheets and α-MnO2 nanorods can uniformly decorate the surface of ...MnCo2O4.5 nanowires to form core–shell heterostructures. Detailed electrochemical characterization reveals that MnCo2O4.5@δ-MnO2 pattern exhibits not only high specific capacitance of 357.5 F g−1 at a scan rate of 0.5 A g−1, but also good cycle stability (97% capacitance retention after 1000 cycles at a scan rate of 5 A g−1), which make it have a promising application as a supercapacitor electrode material.
Display omitted
•Manganese cobalt oxide@manganese dioxides hierarchical nanostructures.•Morphology and crystallinity-controlled synthesis.•High specific capacitance of MnCo2O4.5@δ-MnO2: 357.5 F g−1 at current density of 0.5 A g−1.•Good cycle stability: 97% capacitance retention after 1000 cycles at a scan rate of 5 A g−1.
The development of emerging rechargeable batteries is often hindered by limited chemical understanding composing of entangled patterns in an enormous space. Herein, we propose an interpretable hybrid ...machine learning framework to untangle intractable degradation chemistries of conversion‐type batteries. Rather than being a black box, this framework not only demonstrates an ability to accurately forecast lithium‐sulfur batteries (with a test mean absolute error of 8.9 % for the end‐of‐life prediction) but also generate useful physical understandings that illuminate future battery design and optimization. The framework also enables the discovery of a previously unknown performance indicator, the ratio of electrolyte amount to high‐voltage‐region capacity at the first discharge, for lithium‐sulfur batteries complying practical merits. The present data‐driven approach is readily applicable to other energy storage systems due to its versatility and flexibility in modules and inputs.
An interpretable hybrid machine learning framework is designed for post‐lithium‐ion battery (e.g. lithium‐sulfur battery) forecast using lab‐scale battery dataset with compromised quality and tremendous variables. Key knowledge about the complex and dynamic degradation chemistries is extracted to illuminate future battery design and optimization.
Engineering high‐performance electrocatalysts is of great importance for energy conversion and storage. As an efficient strategy, element doping has long been adopted to improve catalytic activity, ...however, it has not been clarified how the valence state of dopant affects the catalytic mechanism and properties. Herein, it is reported that the valence state of a doping element plays a crucial role in improving catalytic performance. Specifically, in the case of iridium doped nickel‐iron layer double hydroxide (NiFe‐LDH), trivalent iridium ions (Ir3+) can boost hydrogen evolution reaction (HER) more efficiently than tetravalent iridium (Ir4+) ions. Ir3+‐doped NiFe‐LDH delivers an ultralow overpotential (19 mV @ 10 mA cm−2) for HER, which is superior to Ir4+ doped NiFe‐LDH (44 mV@10 mA cm−2) and even commercial Pt/C catalyst (40 mV@ 10 mA cm−2), and reaches the highest level ever reported for NiFe‐LDH‐based catalysts. Theoretical and experimental analyses reveal that Ir3+ ions donate more electrons to their neighboring O atoms than Ir4+ ions, which facilitates the water dissociation and hydrogen desorption, eventually boosting HER. The same valence‐state effect is found for Ru and Pt dopants in NiFe‐LDH, implying that chemical valence state should be considered as a common factor in modulating catalytic performance.
The valence state of a doping element is found to play a key role on the catalytic performance. In the case of iridium doped nickel‐iron layer double hydroxide (NiFe‐LDH), Ir3+‐doped NiFe‐LDH delivers an ultralow overpotential (19 mV @ 10 mA cm−2) for hydrogen evolution reaction, which is superior to Ir4+ doped NiFe‐LDH and commercial Pt/C.
The circularly polarized organic light‐emitting diodes (CP‐OLEDs) demonstrate promising application in 3D display due to the direct generation of circularly polarized electroluminescence (CPEL). But ...the chiral luminescence materials face challenges as intricated synthetic route, enantiomeric separation, etc. Herein, fresh CP‐OLEDs are designed based on chiral hole transport material instead of chiral emitters. A pair of hole transport enantiomers (R/S‐NPACZ) exhibit intense dissymmetry factors (|gPL|) about 5.0 × 10−3. With R/S‐NPACZ as hole transport layers, CP‐OLEDs are fabricated employing six achiral phosphorescence and thermally activated delayed fluorescence (TADF) materials with different wavelengths, in consistence with the generated CPEL spectra. The CP‐OLEDs based on achiral red, green, and blue iridium(III) complexes exhibit external quantum efficiencies (EQEs) of 14.9%, 30.7%, and 14.1% with |gEL| factors of 8.8 × 10−4, 2.3 × 10−3, and 2.0 × 10−3, respectively. Moreover, the devices using achiral blue, blueish‐green, and green TADF materials display EQEs of 24.1%, 17.9%, and 25.4% with |gEL| factors of 1.0 × 10−3, 3.6 × 10−3, and 2.2 × 10−3, respectively. As far as known, it is the first example of CP‐OLEDs based on chiral hole transport materials, which act as the organic circularly polarizers and have potential to generate CPEL from achiral luminescence materials.
A pair of hole transport enantiomers are applied in fabrication of circularly polarized organic light‐emitting diodes first time with achiral luminescent materials as emitters, where the chiral hole transport enantiomers act as the organic circularly polarizers in principle. All devices exhibit symmetric circularly polarized electroluminescent spectra with dissymmetry factors ranging from 8.8 × 10−4 to 3.6 × 10−3.
Lithium–sulfur (Li–S) batteries are regarded as promising high‐energy‐density energy storage devices. However, the cycling stability of Li–S batteries is restricted by the parasitic reactions between ...Li metal anodes and soluble lithium polysulfides (LiPSs). Encapsulating LiPS electrolyte (EPSE) can efficiently suppress the parasitic reactions but inevitably sacrifices the cathode sulfur redox kinetics. To address the above dilemma, a redox comediation strategy for EPSE is proposed to realize high‐energy‐density and long‐cycling Li–S batteries. Concretely, dimethyl diselenide (DMDSe) is employed as an efficient redox comediator to facilitate the sulfur redox kinetics in Li–S batteries with EPSE. DMDSe enhances the liquid–liquid and liquid–solid conversion kinetics of LiPS in EPSE while maintains the ability to alleviate the anode parasitic reactions from LiPSs. Consequently, a Li–S pouch cell with a high energy density of 359 Wh kg−1 at cell level and stable 37 cycles is realized. This work provides an effective redox comediation strategy for EPSE to simultaneously achieve high energy density and long cycling stability in Li–S batteries and inspires rational integration of multi‐strategies for practical working batteries.
A redox comediation strategy is proposed for promoting the cathode redox kinetics and simultaneously retaining the anode protection capability of lithium–sulfur batteries using encapsulating lithium polysulfide electrolyte. A 1.5 Ah lithium–sulfur pouch cell realizes a high initial energy density of 359 Wh kg−1 and 37 stable cycles following the above strategy.
The reversible formation of chemical bonds has potential for tuning multi‐electron redox reactions in emerging energy‐storage applications, such as lithium−sulfur batteries. The dissolution of ...polysulfide intermediates, however, results in severe shuttle effect and sluggish electrochemical kinetics. In this study, quinonoid imine is proposed to anchor polysulfides and to facilitate the formation of Li2S2/Li2S through the reversible chemical transition between protonated state (NH+
) and deprotonated state (N). When serving as the sulfur host, the quinonoid imine‐doped graphene affords a very tiny shuttle current of 2.60 × 10−4 mA cm−2, a rapid redox reaction of polysulfide, and therefore improved sulfur utilization and enhanced rate performance. A high areal specific capacity of 3.72 mAh cm−2 is achieved at 5.50 mA cm−2 on the quinonoid imine‐doped graphene based electrode with a high sulfur loading of 3.3 mg cm−2. This strategy sheds a new light on the organic redox mediators for reversible modulation of electrochemical reactions.
Quinonoid imine (NH+) is proposed for anchoring polysulfides and facilitating the formation of Li2S2/Li2S in a working cell. The adsorption and redox activities of polysulfides are significantly enhanced, while the shuttle effect is largely mitigated. This provides not only new insight into the anchoring of intermediate in a working cell, but also a strategy to enhance the redox reactions on nitrogen‐containing functional groups.
