NiCo₂O₄ Nanofibers as Carbon‐Free Sulfur Immobilizer to Fabricate Sulfur‐Based Composite with High Volumetric Capacity for Lithium–Sulfur Battery

Abstract

Both the energy density and cycle stability are still challenges for lithium–sulfur (Li–S) batteries in future practical applications. Usually, light‐weight and nonpolar carbon materials are used as the hosts of sulfur, however they struggle on the cycle stability and undermine the volumetric energy density of Li–S batteries. Here, heavy NiCo2O4 nanofibers as carbon‐free sulfur immobilizers are introduced to fabricate sulfur‐based composites. NiCo2O4 can accelerate the catalytic conversion kinetics of soluble intermediate polysulfides by strong chemical interaction, leading to a good cycle stability of sulfur cathodes. Specifically, the S/NiCo2O4 composite presents a high gravimetric capacity of 1125 mAh g−1 at 0.1 C rate with the composite as active material, and a low fading rate of 0.039% per cycle over 1500 cycles at 1 C rate. In particular, the S/NiCo2O4 composite with the high tap density of 1.66 g cm−3 delivers large volumetric capacity of 1867 mAh cm−3, almost twice that of the conventional S/carbon composites.

Sulfiphilic Few‐Layered MoSe2 Nanoflakes Decorated rGO as a Highly Efficient Sulfur Host for Lithium‐Sulfur Batteries

“…In order to investigate the nucleation behaviors of Li 2 S on the two electrode surface, the kinetics of the liquid-solid reaction from polysulfides to Li 2 S is tested. [56,57] The respective resistance of the two electrodes is shown in Table S1 in the Supporting Information. As shown in Figure 6E,F, the cell with MoSe 2 @rGO as cathode reaches the highest potentiostatic current after 6200 s, while the cell with rGO was as long as 21 000 s. The shorter time for MoSe 2 @rGO is related to the faster nucleation process and the shorter "incubation" period.…”

Separator Modified by Cobalt‐Embedded Carbon Nanosheets Enabling Chemisorption and Catalytic Effects of Polysulfides for High‐Energy‐Density Lithium‐Sulfur Batteries

“…[30,38] The interaction between Co-N x @NPC/G and polysulfides was further examined by XPS spectrum of Co-N x @NPC/G after poly sulfides adsorption. [11,40] The Co-N x @NPC/G-modified PP separator (Co-N x @NPC/G-PP) was readily fabricated by vacuum-filtering Co-N x @NPC/G nanosheets on conventional Celgard PP separator (Figure 4b). [39] In addition, the characteristic peaks of N 1s and Co 2p 3/2 XPS spectra shift to higher binding energy and lower binding energy, Adv.…”

Adsorption‐Catalysis Design in the Lithium‐Sulfur Battery

“…According to the density functional theory (DFT), they found much higher binding energy between sulfur species and MnO 2 plane than that with graphitic carbon, which indicates much stronger chemisorption and retention capability of the NGCM spongy framework. [49] From the cycle performance and Coulombic efficiency (Figure 3g), S/NiCo 2 O 4 can deliver a better performance, which indicates NiCo 2 O 4 can accelerate the conversion of LiPSs. Ascribing to the great conductivity produced by porous graphene and the outstanding catalytic ability generated by MnO 2 , the battery exhibited an initial discharge capacity of 1132 and 908 mAh g −1 at 0.2 C and 1 C, respectively.…”

“…[41] In recent investigations, MnO 2 is a vital material to serve as an efficient catalyst to enhance the conversion kinetics for Li-S battery, strenuous effort has been done. [49] Copyright 2019, Wiley-VCH. According to the density functional theory (DFT), they found much higher binding energy between sulfur species and MnO 2 plane than that with graphitic carbon, which indicates much stronger chemisorption and retention capability of the NGCM spongy framework.…”