A Highly Conductive MOF of Graphene Analogue Ni₃(HITP)₂ as a Sulfur Host for High‐Performance Lithium–Sulfur Batteries

Abstract

Lithium–sulfur (Li–S) batteries have been considered as one of the most promising energy storage systems owing to their high theoretical capacity and energy density. However, their commercial applications are obstructed by sluggish reaction kinetics and rapid capacity degradation mainly caused by polysulfide shuttling. Herein, the first attempt to utilize a highly conductive metal–organic framework (MOF) of Ni3(HITP)2 graphene analogue as the sulfur host material to trap and transform polysulfides for high‐performance Li–S batteries is made. Besides, the traditional conductive additive acetylene black is replaced by carbon nanotubes to construct matrix conduction networks for triggering the rate and cycling performance of the active cathode. As a result, the S@Ni3(HITP)2 with sulfur content of 65.5 wt% shows excellent sulfur utilization, rate performance, and cyclic durability. It delivers a high initial capacity of 1302.9 mAh g−1 and good capacity retention of 848.9 mAh g−1 after 100 cycles at 0.2 C. Highly reversible discharge capacities of 807.4 and 629.6 mAh g−1 are obtained at 0.5 and 1 C for 150 and 300 cycles, respectively. Such kinds of pristine MOFs with high conductivity and abundant polar sites reveal broad promising prospect for application in the field of high‐performance Li–S batteries.

MIL-88A Metal-Organic Framework as a Stable Sulfur-Host Cathode for Long-Cycle Li-S Batteries

“…This phenomenon is seen more clearly in Figure 6b, where the charge and discharge profiles during the first cycles are not well defined. Additionally, charge profiles of the 1 st and 2 nd cycles showed a high polarisation at the beginning of cycling as previously indicated in the first cycle of the CV, which could be caused by the greater resistance that the cell presents until the SEI is formed, as previously observed for MOFs as sulfur hosts in Li-S batteries [78].…”

“…This phenomenon is seen more clearly in Figure 6b, where the charge and discharge profiles during the first cycles are not well defined. Additionally, charge profiles of the 1 st and 2 nd cycles showed a high polarisation at the beginning of cycling as previously indicated in the first cycle of the CV, which could be caused by the greater resistance that the cell presents until the SEI is formed, as previously observed for MOFs as sulfur hosts in Li-S batteries [78]. In order to avoid these harmful effects, the Li/LiTFSI-LiNO3-DOL:DME/MIL-88A@S cell has been studied by a long-term cycling at a moderate constant current of 0.5 C (Figure 7), after two activation cycles performed at 0.1 C. As can be seen, two plateaus at 2.35 V and 2.0 V are clearly observed during the discharge process at 0.5 C, which correspond to the formation of long chain lithium polysulfides (Li2Sx, 4 ≤ x ≤ 8), and short-chain lithium polysulfides (such as Li2S2 and Li2S), The galvanostatic measurements of the Li/LiTFSI-LiNO 3 -DOL:DME/MIL-88A@S cells were carried out by cycling at various currents as well as at a constant C-rate of 0.5 C. The rate capability test (Figure 6a,b) for the MIL-88A@S composite provided an initial capacity of 600 mAh g −1 that was stabilized over the first five cycles, displaying an average discharge capacity of 482 mAh g −1 at 0.1 C. This maximum capacity value gradually decreased to about 395, 374, 333, 274, 152, and 55 mAh g −1 , at 0.125 C, 0.2 C, 0.33 C, 0.5 C, 1 C, and 2 C, respectively, as demonstrated by the cycling trends of Figure 6a.…”

“…This phenomenon is seen more clearly in Figure 6b, where the charge and discharge profiles during the first cycles are not well defined. Additionally, charge profiles of the 1 st and 2 nd cycles showed a high polarisation at the beginning of cycling as previously indicated in the first cycle of the CV, which could be caused by the greater resistance that the cell presents until the SEI is formed, as previously observed for MOFs as sulfur hosts in Li-S batteries [78]. In order to avoid these harmful effects, the Li/LiTFSI-LiNO3-DOL:DME/MIL-88A@S cell has been studied by a long-term cycling at a moderate constant current of 0.5 C (Figure 7), after two activation cycles performed at 0.1 C. As can be seen, two plateaus at 2.35 V and 2.0 V are clearly observed during the discharge process at 0.5 C, which correspond to the formation of long chain lithium polysulfides (Li2Sx, 4 ≤ x ≤ 8), and short-chain lithium polysulfides (such as Li2S2 and Li2S), In order to avoid these harmful effects, the Li/LiTFSI-LiNO 3 -DOL:DME/MIL-88A@S cell has been studied by a long-term cycling at a moderate constant current of 0.5 C (Figure 7), after two activation cycles performed at 0.1 C. As can be seen, two plateaus at 2.35 V and 2.0 V are clearly observed during the discharge process at 0.5 C, which correspond to the formation of long chain lithium polysulfides (Li 2 S x , 4 ≤ x ≤ 8), and short-chain lithium polysulfides (such as Li 2 S 2 and Li 2 S), respectively, and which correspond to the potential values of the cathode peaks obtained in the cyclic voltammetry measurements (Figure 5a).…”

In Situ Coating Graphdiyne for High‐Energy‐Density and Stable Organic Cathodes

“…Additionally, the potential application of organic cathodes can be readily extended in the storage of the diverse alkali metal ions, including Li + , Na + , and K + . [ 4–6 ] It can diversify the energy storage systems, which is the fundamental way to solve the serious resource dependence in the traditional LIBs industry.…”

Ultrafine Co3Se4 Nanoparticles in Nitrogen‐Doped 3D Carbon Matrix for High‐Stable and Long‐Cycle‐Life Lithium Sulfur Batteries

“…Designing sulfur host has been demonstrated to be an effective strategy to improve cycling performance of LSBs, as indicated by our previous works and related literatures. [ 13–15 ] One goal is to ameliorate the conductivity of the electrode considering the large fraction of insulated elemental sulfur (5 × 10 −30 S cm −1 , 25 °C) that hinders redox reactions and limits the sulfur utilization. On the other side, hierarchical pores of sulfur hosts can physically confine sulfur intermediates and increase void spaces in hosts to alleviate large volume variations during charge/discharge process.…”