Polysulfide Anchoring Mechanism Revealed by Atomic Layer Deposition of V₂O₅ and Sulfur-Filled Carbon Nanotubes for Lithium–Sulfur Batteries

Abstract

Despite the promise of surface engineering to address the challenge of polysulfide shuttling in sulfur-carbon composite cathodes, melt infiltration techniques limit mechanistic studies correlating engineered surfaces and polysulfide anchoring. Here, we present a controlled experimental demonstration of polysulfide anchoring using vapor phase isothermal processing to fill the interior of carbon nanotubes (CNTs) after assembly into binder-free electrodes and atomic layer deposition (ALD) coating of polar VO anchoring layers on the CNT surfaces. The ultrathin submonolayer VO coating on the CNT exterior surface balances the adverse effect of polysulfide shuttling with the necessity for high sulfur utilization due to binding sites near the conductive CNT surface. The sulfur loaded into the CNT interior provides a spatially separated control volume enabling high sulfur loading with direct sulfur-CNT electrical contact for efficient sulfur conversion. By controlling ALD coating thickness, high initial discharge capacity of 1209 mAh/g at 0.1 C and exceptional cycling at 0.2 C with 87% capacity retention after 100 cycles and 73% at 450 cycles is achieved and correlated to an optimal VO anchoring layer thickness. This provides experimental evidence that surface engineering approaches can be effective to overcome polysulfide shuttling by controlled design of molecular-scale building blocks for efficient binder free lithium sulfur battery cathodes.

Surface Functionalization of Carbon Architecture with Nano‐MnO2 for Effective Polysulfide Confinement in Lithium–Sulfur Batteries

“…[11b] The PC/S electrode delivered relativelyl ow rate capabilitiesa tc urrent densities from 0.5 to 4C.I nc ontrast, the M-PC/S electrode showedh igherr eversible discharge capacities of 1163,984, 795, and 422 mA hg À1 as current densities increasef rom 0.5 to 4C,r espectively.I na ddition, the voltage profiles of PC/S and M-PC/S at different current rate showedn oticeable differences in voltage hysteresis. [16] The M-PC/S showedasignificantly small increase of charge transfer from 1 st to 100 th cycle, compared to the PC/S (Figure 4d and 4e). This is ascribed to two main benefits of M-PC:a )physical confinement of polysulfides within the micropores of PC scaffold and b) the furtherc apture of polysulfides via chemical interaction of nano-MnO 2 .T he charge/discharge curves of both PC/S and M-PC/S at the 1 st and 250 th cycles are shown in Figure4ba nd 4c.B oth voltage profiles showedt ypicals ulfur electrode behaviors with two plateau regions( 2.3 and 2.1V ,w hich is contributed from highand low-order polysulfidereduction, respectively).…”

Structure Design and Composition Engineering of Carbon‐Based Nanomaterials for Lithium Energy Storage

“…The classic 1D structure endows exclusive superiority in construction of an effective conducting network with active materials . As a host material, the capillary filling of active materials in CNTs leaves CNT–CNT electrical pathways unimpeded . The self‐weaving behavior of CNTs to construct an interwoven conductive network allows fast transfer of electrons .…”

“…[42] As a host material, the capillary filling of active materials in CNTs leaves CNT-CNT electrical pathways unimpeded. [43] The selfweaving behavior of CNTs to construct an interwoven conductive network allows fast transfer of electrons. [44] A good example is a low-density CNTs foam with high areal loading and areal capacity sulfur cathodes prepared via freeze-drying.…”

Multifunctionality of Carbon-based Frameworks in Lithium Sulfur Batteries

“…Other metal oxides have also been explored for sulfur cathodes, such as NiFe 2 O 4 [191], Al 2 O 3 [192], MgO [193], SiO 2 [194], SnO [195], V 2 O 5 [196], Fe 3 O 4 [197], ZnO [198], CeO 2 [199], and have demonstrated promising properties. For example, Fan et al [191] synthesized a spinel carbonbased hybrid as the sulfur cathode in Li-S batteries which produced high performances by using CNTs to fabricate conductive networks and NiFe 2 O 4 nanosheets to confine polysulfides.…”