An official website of the United States government
The shuttling of polysulfides with sluggish redox kinetics has severely retarded the advancement of lithium–sulfur (Li–S) batteries. In this work oxygen-deficient titanium dioxide (TiO 2 ) has been investigated as a novel functional host for Li–S batteries. Experimental and first-principles density functional theory (DFT) studies reveal that oxygen vacancies help to reduce polysulfide shuttling and catalyze the redox kinetics of sulfur/polysulfides during cycling. Consequently, the resulting TiO 2 /S composite cathode manifests superior electrochemical properties in terms of high capacity (1472 mA h g −1 at 0.2C), outstanding rate capability (571 mA h g −1 at 2C), and excellent cycling properties (900 mA h g −1 over 100 cycles at 0.2C). The present strategy offers a viable way through vacancy engineering for the design and optimization of high-performance electrodes for advanced Li–S batteries and other electrochemical devices.
more »
« less
A Janus protein-based nanofabric for trapping polysulfides and stabilizing lithium metal in lithium–sulfur batteries
The shuttling of polysulfides and uncontrollable growth of lithium dendrites remain the most critical obstacles deteriorating the performance and safety of lithium–sulfur batteries. The separator plays a key role in molecule diffusion and ion transport kinetics; thus, endowing the separator with functions to address the two abovementioned issues is an urgent need. Herein, a protein-based, low-resistance Janus nanofabric is designed and fabricated for simultaneously trapping polysulfides and stabilizing lithium metal. The Janus nanofabric is achieved via combining two functional nanofabric layers, a gelatin-coated conductive nanofabric (G@CNF) as a polysulfide-blocking layer and a gelatin nanofabric (G-nanofabric) as an ion-regulating layer, into a heterostructure. The gelatin coating of G@CNF effectively enhances the polysulfide-trapping ability owing to strong gelatin–polysulfide interactions. The G-nanofabric with exceptional wettability, high ionic conductivity (4.9 × 10 −3 S cm −1 ) and a high lithium-ion transference number (0.73) helps stabilize ion deposition and thus suppresses the growth of lithium dendrites. As a result, a Li/Li symmetric cell with the G-nanofabric delivers ultra-long cycle life over 1000 h with very stable performance. Benefiting from the synergistic effect of the two functional layers of the Janus nanofabric, the resulting Li–S batteries demonstrate excellent capacity, rate performance and cycling stability ( e.g. initial discharge capacity of 890 mA h g −1 with a decay rate of 0.117% up to 300 cycles at 0.5 A g −1 ).
more »
« less
- Award ID(s):
- 1929236
- PAR ID:
- 10191474
- Date Published:
- Journal Name:
- Journal of Materials Chemistry A
- Volume:
- 8
- Issue:
- 15
- ISSN:
- 2050-7488
- Page Range / eLocation ID:
- 7377 to 7389
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract The development of practical lithium–sulfur (Li–S) batteries with prolonged cycle life and high Coulombic efficiency is limited by both parasitic reactions from dissolved polysulfides and mossy lithium deposition. To address these challenges, here lithium trithiocarbonate (Li2CS3)‐coated lithium sulfide (Li2S) is employed as a dual‐function cathode material to improve the cycling performance of Li–S batteries. Interestingly, at the cathode, Li2CS3forms an oligomer‐structured layer on the surface to suppress polysulfide shuttle. The presence of Li2CS3alters the conventional sulfur reaction pathway, which is supported by material characterization and density functional theory calculation. At the anode, a stable in situ solid electrolyte interphase layer with a lower Li‐ion diffusion barrier is formed on the Li‐metal surface to engender enhanced lithium plating/stripping performance upon cycling. Consequently, the obtained anode‐free full cells with Li2CS3exhibit a superior capacity retention of 51% over 125 cycles, whereas conventional Li2S cells retain only 26%. This study demonstrates that Li2CS3inclusion is an efficient strategy for designing high‐energy‐density Li–S batteries with extended cycle life.more » « less
-
Rechargeable lithium–sulfur batteries have emerged as a viable technology for next generation electrochemical energy storage, and the sulfur cathode plays a critical role in determining the device performance. In this study, we prepared functional composites based on polypyrrole-coated MnO 2 nanotubes as a highly efficient sulfur host (sulfur mass loading 63.5%). The hollow interior of the MnO 2 nanotubes not only allowed for accommodation of volumetric changes of sulfur particles during the cycling process, but also confined the diffusion of lithium polysulfides by physical restriction and chemical adsorption, which minimized the loss of polysulfide species. In addition, the polypyrrole outer layer effectively enhanced the electrical conductivity of the cathode to facilitate ion and electron transport. The as-prepared MnO 2 -PPy-S composite delivered an initial specific capacity of 1469 mA h g −1 and maintained an extremely stable cycling performance, with a small capacity decay of merely 0.07% per cycle at 0.2C within 500 cycles, a high average coulombic efficiency of 95.7% and an excellent rate capability at 470 mA h g −1 at the current density of 3C.more » « less
-
Abstract The lithium–sulfur (Li–S) battery is a promising candidate for next‐generation high‐density energy storage devices because of its ultrahigh theoretical energy density and the natural abundance of sulfur. However, the practical performance of the sulfur cathode is plagued by fast capacity decay and poor cycle life, both of which can be attributed to the intrinsic dissolution/shuttling of lithium polysulfides. Here, a new built‐in magnetic field–enhanced polysulfide trapping mechanism is discovered by introducing ferromagnetic iron/iron carbide (Fe/Fe3C) nanoparticles with a graphene shell (Fe/Fe3C/graphene) onto a flexible activated cotton textile (ACT) fiber to prepare the ACT@Fe/Fe3C/graphene sulfur host. The novel trapping mechanism is demonstrated by significant differences in the diffusion behavior of polysulfides in a custom‐designed liquid cell compared to a pure ACT/S cathode. Furthermore, a cell assembled using the ACT@Fe/Fe3C/S cathode exhibits a high initial discharge capacity of ≈764 mAh g−1, excellent rate performance, and a remarkably long lifespan of 600 cycles using ACT@Fe/Fe3C/S (whereas only 100 cycles can be achieved using pure ACT/S). The new magnetic field–enhanced trapping mechanism provides not only novel insight but unveils new possibilities for mitigating the “shuttle effect” of polysulfides thereby promoting the practical applications of Li–S batteries.more » « less
-
Lithium–sulfur (Li–S) batteries are regarded as one of the most promising next-generation electrochemical cells. However, shuttling of lithium polysulfide intermediates and sluggish kinetics in random deposition of lithium sulfide (Li 2 S) have significantly degraded their capacity, rate and cycling performance. Herein, few-layered MoS 2 nanosheets enriched with sulfur vacancies are anchored inside hollow mesoporous carbon (MoS 2−x /HMC) via S–C bonding and proposed as a novel functional mediator for Li–S batteries. Ultrathin MoS 2 sheets with abundant sulfur vacancies have strong chemical affinity to polysulfides and in the meantime catalyze their fast redox conversion with enhanced reaction kinetics as proved by experimental observations and first-principles density functional theory (DFT) calculations. At a current density of 1C, the MoS 2−x /HMC-S composite cathode exhibits a high initial capacity of 945 mA h g −1 with a high retained capacity of 526 mA h g −1 and a coulombic efficiency of nearly 100% after 500 cycles. The present work sheds light on the design of novel functional electrodes for next-generation electrochemical cells based on a simple yet effective vacancy engineering strategy.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/d0ta01989e
