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Electrochem 2020, 1 238 tubes in the structure. Indeed, high reversible capacity of 1219 mAh g−1 was observed even after 200 cycles at 0.2 C. The low long-term cycling capacity decay of 0.039% per cycle over 500 cycles at 1 C and improvements in rate were also attributed to the benefits endowed by the architecture. Although tremendous effort has been put into developing cathode materials and in devising separator layers, comparably less effort has been extended into devising porous interlayers to be placed between the cathode and the separator. This is another approach to minimize shuttle effects. In one effort in this vein, a porous interlayer was rapidly fabricated of carbon microfibers using centrifugal spinning [51]. A remarkable impact on the cell resistance was observed as a result of the interlayer. Without the interlayer, the cell had a resistance of 55 ohm, whereas the analogous cell with the interlayer had a much lower resistance of 25 ohm. When this interlayer is used, the device exhibits a high 1485 mAh g−1 initial discharge capacity. When operated over 200 cycles (0.2 C), a capacity of 615 mAh g−1. When operated at 1 C, the cell had improved performance from 250 mAh g−1 (without the interlayer) to 600 mAh g−1 with the interlayer. On the basis of these data, an important area of future work may be to evaluate Li-S batteries comprising the most successful cathodic materials and separators with the addition of such interlayers. 4.2.Heterofuatuorme-wDoorkpemdaCybaerbtonevanludatPe-LBi-lSocbkatEtelreimesecnotmMpraistienrgiathlsemostsuccessfulcathodicmaterialsand separators with the addition of such interlayers. Electrochem 2020, 2, FOR PEER REVIEW 14 One way to tune the affinity of carbon for polysulfides is to dope the carbon with heteroatoms [90]. 4.2. Heteroatom-Doped Carbon and P-Block Element Materials If appropriate doping levels using a particular heteroatom is accomplished, the polysulfides can be heldinclosepOrnoexwimayittyotountehtehecoafnfidnuityctoinfcgarcbaornbfonrpnoelyasrutlhfideecsaitshtodoepienthaemcaarnbonnewrsitihmhieltaerotaototmhastprovided [90]. If appropriate doping levels using a particular heteroatom is accomplished, the polysulfides can by Co or Mo sites, for example. Using heteroatoms instead of metals is often more affordable and be held in close proximity to the conducting carbon near the cathode in a manner similar to that more environmentally favorable as well. A recent effort to use heteroatoms employed nitrogen-doped provided by Co or Mo sites, for example. Using heteroatoms instead of metals is often more carbon (NC) or phosphorus and nitrogen co-doped carbon (NPC) at carefully selected ratios [52]. affordable and more environmentally favorable as well. A recent effort to use heteroatoms employed One aim noiftrtohgens-dtuopdeyd, scaurpbopnor(NteCd) borypchaolscpuhloartuisonansd, wniatrsogtoendceot-edrompeidnecatrhboene(xNtePCn)t taot cwarhefiuclhlythe doped selected ratios [52]. One aim of the study, supported by calculations, was to determine the extent to materials could adsorb polysulfides (Figure 10). On the basis of simulations, a carbon nanotube aerogel which the doped materials could adsorb polysulfides (Figure 10). On the basis of simulations, a was prepared using glucosamine as the nitrogen source and elemental phosphorus directly during carbon nanotube aerogel was prepared using glucosamine as the nitrogen source and elemental carbonization. The cell incorporating this layer with a sulfur loading of 3.5 mg cm−2 exhibited an phosphorus directly during carbonization. The cell incorporating this layer with a sulfur loading of −1 −2 −1 initialspe3c.5ifimcgccampaceixthyiboitfed90a0nminiAtiahlsgpeci.fiAccfatpearc4it5y0ofc9y0c0lemsA(h0.g2C.A),ftaerc4a5p0acyccitleysd(0e.2caCy),oafca0p.1ac6it%y/cyclewas decay of 0.16%/cycle was observed. An interesting follow-up to this study would be to screen other observed. An interesting follow-up to this study would be to screen other N/P ratios experimentally to N/P ratios experimentally to assess whether calculations and simulations are effectively predictive in assess whether calculations and simulations are effectively predictive in these cases. these cases. Figure10F.iSgcuhree1m0.aStcihcedmeamticodnemstornasttirnatgintghtehestsrtructurreeooffNNCC(A)(,Asi)x,tsyipxestyopfpeostoenftipaloPte-dnotpiainlgPs-itdesopiningsitesin nitrogen co-doped carbon (NPC) (B), and adsorption of lithium polysulfide species (D, E) to these nitrogen co-doped carbon (NPC) (B), and adsorption of lithium polysulfide species (D,E) to these surfaces. Reprinted with permission from reference [52]. Copyright 2020 American Chemical Society. surfaces. Reprinted with permission from reference [52]. Copyright 2020 American Chemical Society. Another effort employed hollow spheres comprising N-doped carbon having SnS2 nanoparticles on their exteriors [53]. The hollow carbon spheres on their own exhibit high conductivity, and the hypothesis was that this conductivity, coupled with the high specific surface area could serve as an effective host for sulfur. A high sulfur loading of about 3 mg cm−2 was indeed accomplished in the cathode. The purpose of the SnS2 nanoparticles was to absorb polysulfides and facilitate the deposition of Li2S. This cathodic material was effective in devices with a 1344 mAh g−1 discharge capacity (0.2 C), and at 0.5 C they demonstrated reasonable stability for at least 200 cycles. Another example of carefully-designed nanoarchitecture is illustrated by the use of hollowPDF Image | Lithium-Sulfur Batteries: Advances and Trends
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