Promoted Deposition of Three-Dimensional Li₂S on Catalytic Co Phthalocyanine Nanorods for Stable High-Loading Lithium–Sulfur Batteries

Abstract

The sulfur redox in Li–S batteries involves a complex sequence of solid–liquid–solid conversions, and reaction catalysis has recently become a focused area for further advancement. The deposition of solid Li2S from liquid Li2S4 contributes to three-quarters of the total theoretical capacity and is therefore of great significance over the entire cathode reaction. This study demonstrates a cathode material composed of carbon nanofibers decorated with catalytic Co phthalocyanine nanorods (CoPc@CNF), which are highly effective in promoting the deposition of Li2S in three-dimensional (3D) fine particles rather than 2D thin films. This significantly alleviates cathode passivation during cell charge and discharge, leading to obviously improved sulfur utilization and cycling stability for high loading cathodes. DFT calculations indicate that the promoted 3D deposition of Li2S is related to the facilitated migration of deposition precursors (Li2S4 and Li-ions) to migrate on the CoPc nanorods. Lithium–sulfur (Li–S) pouch cells were prepared with high specific (954 mAh g–1), areal (4.8 mAh cm–2), and total (235 mAh) capacities achieved at 0.5 C under high sulfur content. As metal phthalocyanines possess a high structural variability, this study provides opportunities to the design of a new class of Li–S cathode materials.

Yolk‐Shell NiCo2PX as a Bidirectional Catalyst for Liquid‐Solid Processes in Advanced Lithium‐Sulfur Batteries

“…In the CV results of symmetrical cells (Figure 5b), NiCo 2 P X /rGO exhibits a higher current response than CoP/rGO and rGO, meaning faster reaction rates and accelerated LiPSs conversion kinetics compared to monometallic phosphides and pure carbon materials. [27] Furthermore, as shown in Figure 5c, the Rct of NiCo 2 P X /rGO is lower than that of CoP/rGO and rGO. It verifies that the NiCo 2 P X increases the charge transfer rate in the process of LiPSs conversion.…”

MXene supported transition metal nanoparticles accelerate sulfur reduction reaction kinetics

“…26 A potentiostatic Li 2 S nucleation test was employed to evaluate the role of TMNPs in regulating the Li 2 S precipitation on the surface of sulfur hosts, using the coin cells with the TMNPs@MXene working electrode, Li foil counter electrode, and Li 2 S 8 -containing electrolyte. These cells were galvanostatically discharged to 2.09 V to transform the Li 2 S 8 into Li 2 S 4 and then kept at 2.08 V to drive the deposition of Li 2 S. The current peak in the potentiostatic discharge curves of the Li 2 S 8 solution is associated with the nucleation and precipitation of Li 2 S. 24,27 As shown in Fig. 2d-f, the current intensity of CoNPs@MXene reaches the peak at 1800 s, which is earlier than the cases of FeNPs@MXene and NiNPs@MXene.…”

Theoretical Insights into the Favorable Functionalized Ti2C-Based MXenes for Lithium–Sulfur Batteries

“…59−62 In accordance with previous studies, herein, we investigate the migration path of Li diffusion on Ti 2 CT 2 (T = −S, −F, −O) surfaces and the corresponding diffusion energy barrier by the LST/QST method. 63,64 Figure 8 shows the migration path and energy profiles for the Ti 2 CS 2 surface (Figure 8a,d), Ti 2 CF 2 surface (Figure 8b,e), and Ti 2 CO 2 surface (Figure 8c,f). On the Ti 2 CS 2 surface, the stable adsorption site of Li, hcp Ti, is marked as the A site (the point is set as the zero energy point).…”