Crystallinity Regulated Functional Separator Based on Bimetallic Ni_xFe_y Alloy Nanoparticles for Facilitated Redox Kinetics of Lithium–Sulfur Batteries

Abstract

The practical application of lithium–sulfur batteries (LSBs) is limited by the shuttle effect of lithium polysulfides (LiPSs), large volume expansion, and sluggish conversion kinetics of sulfur. Herein, the crystallinity regulation of NixFey alloy anchored on oxidized carbon nanotube/nitrogen‐doped graphene (NixFey@OCNT/NG) for application of a functional separator into LSBs is demonstrated. A low crystalline NixFey@OCNT/NG (LC‐NixFey@OCNT/NG) modified polypropylene separator is systematically compared with its highly crystalline counterpart (HC‐NixFey@OCNT/NG), demonstrating superior LiPS absorbability, redox mediating capability into facilitated conversion kinetics, and uniform flux of Li+ into the anode. Furthermore, theoretical calculations confirm that the LC‐NixFey alloy features high adsorption energies and low diffusion energy barriers toward LiPSs, as well as a decreased energy gap and larger electron density near Fermi level. Accordingly, the LSB cells with LC‐NixFey@OCNT/NG modified separators deliver a high specific capacity of 1379.13 mA h g−1 at 0.1 C and a low decay ratio of 0.04%/cycle over 600 cycles at 5.0 C with a high capacity of 410 mA h g−1. Even under high sulfur loading (5.37 mg cm−2) and lean electrolyte (E/S = 4.9 µL mg−1) conditions, the LSB cells with LC‐NixFey@OCNT/NG/PP deliver a high areal capacity of 4.1 mAh cm−2 at 0.2 C.

Improvement of Redox Kinetics of Dendrite-Free Lithium–Sulfur Battery by Bidirectional Catalysis of Cationic Dual-Active Sites

“…The high areal capacity of 2.7 and 3.8 mAh cm –2 can still be obtained after 100 cycles at a current density of 0.5 mA cm –2 (Figure b). Additionally, recently published studies (Figure c) on modified separators were compared in terms of different aspects. ,− These results further proved that the 3DCS-FMO@C separator can still effectively improve sulfur electrochemistry and inhibit the shuttling of LIPSs in the case of high sulfur loading and poor electrolyte.…”

“…Compared with the highly crystalline HC-Ni x Fe y @OCNT/NG, the low-crystalline and amorphous nanostructure has an unsaturated electronic structure, numerous original random bonds, and abundant defect sites, which can provide effective lithiophilic sites. These features enable the lithium deposition of lithium anode in the process of plating and stripping . However, the active site of these materials is a single site.…”

“…These features enable the lithium deposition of lithium anode in the process of plating and stripping. 25 However, the active site of these materials is a single site. Studies show that dual-active sites are a promising strategy to improve the dynamics of the reaction interface by introducing the synergy of the second site.…”

Aqueous Zinc‐Iodine Batteries: From Electrochemistry to Energy Storage Mechanism

“…[118] It was also reported that separator engineering may catalyze the SRR process and inhibit the shuttle effect of lithium polysulfides in Li─S cells. [119] In view of these outstanding works, separator engineering may be useful in Zn─I 2 batteries to some extent, as it also faces serious problems of Znion batteries and the formidable shuttle effect, and sluggish IRR kinetics.…”

Long-Lasting Zinc–Iodine Batteries with Ultrahigh Areal Capacity and Boosted Rate Capability Enabled by Nickel Single-Atom Electrocatalysts

“…23 Notably, the galvanostatic discharge/charge profiles of Zn−I 2 batteries using NiSAs-HPC/I 2 cathode possessed a lower potential polarization (38 mV) compared with that of the Zn−I 2 batteries using a HPC/I 2 cathode (61 mV). 45,46 The self-discharge behaviors of Zn−I 2 batteries using NiSAs-HPC/I 2 and HPC/I 2 cathodes were also investigated. As displayed in Figure 3f, the open-circuit voltage for the NiSAs-HPC/I 2 cathode delivered ultrahigh stability for ∼100 h with higher voltages, thereby suggesting that polyiodide dissolution and shuttling can be well suppressed.…”