Separator Design Variables and Recommended Characterization Methods for Viable Lithium–Sulfur Batteries

Abstract

technologies that can outperform Li-ion in at least one index of performance. The lithium-sulfur battery (Li-S) is at the forefront of competing battery technologies that on account of being potentially lighter weight, could find immediate use in emerging applications in aviation, provided that solutions to the low cycle-life and poor power delivery can be devised.Extensive research over the past ten years has yielded marked improvements in our control over this complex battery chemistry, as well as a profound understanding of its failure mechanisms, to the extent that commercialization is now much closer to reality.The fact that the Li-S battery could be commercially realized is now pushing the scientific community to devise more practical approaches for implementing what is proving to be a far-from-straightforward technology. The latter feature is no more apparent than in the development of the sulfur cathode, where the competing themes of high sulfur loading, high rate performance, and the irreversible loss of sulfur's reduction products from the cathode have driven much of the research effort to date. Until recently, then, the cathode literature has been dominated by approaches that, while undoubtedly scientifically clever, also involve exotic materials and/or synthetic pathways, thereby rendering the results industrially impractical. Now, in a series of different perspectives, Kaskel and co-workers, [1] Manthiram and co-workers, [2] and Zhang and coworkers [3] have shown the academic community that if they want to be part of the development process of this revolutionary technology, rapid transfer of lab-scale concepts on the prototype cell level is essential. Manthiram and co-workers have simplified the targets of a practical prototype pouch cell and expressed them as the "five 5 s:" sulfur loading >5 mg cm −2 ; carbon content <5%; E/S ratio <5 mL mg −1 ; E/C ratio <5 mL (mA h) −1 ; and negative/ positive (N/P) ratio <5. The successful implementation of all these considerations should, according to Manthiram and co-workers, dramatically transform how lithium-sulfur battery technology is viewed, bridging the gap between academia and industry. [2] Here, however, it seems that feasibility meets the underlying complexity of the Li-S system-often an attempt to fix a deficit in one aspect sees a compromise arising in another. Clearly then, it seemsThe lithium-sulfur (Li-S) battery is at the forefront of technologies that can outperform lithium-ion in at least one index of performance, provided that solutions to poor cycle-life can be devised. One key component of the Li-S battery is the separator, because it holds tremendous promise for improving cycle-life by mitigating the well-known polysulfide shuttle, enabling lean electrolyte configurations, and restricting solid electrolyte interphase growth at the Li-metal anode. However, in response to the advent of the "functional separator" for Li-S batteries, severe misinterpretations of progress have been made due to the often incomplete presentation of the performanc...

Hierarchically Porous Silica Membrane as Separator for High‐Performance Lithium‐Ion Batteries

“…These results suggest that HMS separators possess the desired mechanical strength, holding the promise of preventing the puncture by Li dendrites. [9,35] The thermal stability of PP, Al 2 O 3 /PP, and HMS separators was evaluated by examining their shrinking behaviors at elevated temperatures for 30 min (Figure S6a, Supporting Information). As expected, PP separators exhibited severe shrinkage at 160 °C and even melted at 180 °C, due to the intrinsically low melting point of polyolefin.…”

“…Commercial polarization, thereby increasing the cell resistance and limiting the delivered capacity. [9] Here, we report the fabrication of hierarchically porous, ultralight SiO 2 separators with low-tortuosity porosity, superior mechanical strength, and sufficiently high electrochemical and thermal stability, based on the self-assembly of hollow mesoporous silica (HMS) particles on the cathode surface. Besides the interstitial macropores between close-packed particles, the rich mesopores and hollow interior of individual HMS particles not only provide additional low-tortuosity pathways for rapid ionic transport, but also effectively redistribute the Li-ion flux for uniform Li deposition.…”

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separators used in LIBs are made of polyolefin such as polypropylene (PP), which typically suffers from low porosity, inferior electrolyte wettability, and poor thermal stability. [8,9] Moreover, the wide pore size distribution of PP separators leads to inhomogeneous Li-ion flux during charging and discharging, which can potentially induce the growth of Li dendrites puncturing the separator, thereby causing the dreadful safety hazard. [10,11] In the past decade, many efforts have been concentrated on designing new separators beyond polyolefin or modifying polyolefin-based separators.

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Recent developments in natural mineral-based separators for lithium-ion batteries

“… 7,9 In lithium–sulfur (Li–S) batteries, in addition to the functions required by the separator in LIBs, the separator needs more functions, such as inhibiting the shuttle effect of polysulfides to ensure the long cycle life of Li–S batteries. 10 Utilizing the electrostatic attraction between cationic polymers and polysulfides, Li and co-workers 11 prepared CNT@cationic polymer/rGO (CNTs@CP/rGO)-functionalized separator to inhibit the shuttle effect of polysulfide, thereby ensuring the long cycle life of Li–S batteries. Liu and co-workers 12 proposed for the first time that cellulose nanocrystals (CNCs) was used as a multifunctional polysulfide stopper in Li–S batteries.…”

Electrochemically-Matched and Nonflammable Janus Solid Electrolyte for Lithium–Metal Batteries

“…1 Thanks to their high energy density, low self-discharge, and long shelf life, they have been dominating the market of portable electronics ever since and have changed the way people communicate and get entertained. 1,2 During recent decades, the electrification of vehicles puts forward higher standards for batteries. To solve the range anxiety, extensive effort has been devoted to further increasing the energy density of LIBs.…”