Enhanced Chemical Immobilization and Catalytic Conversion of Polysulfide Intermediates Using Metallic Mo Nanoclusters for High-Performance Li–S Batteries

Abstract

Rechargeable lithium–sulfur batteries have attracted tremendous scientific attention owing to their high energy density. However, their practical application is greatly hindered by the notorious shuttling of soluble lithium polysulfide (LPS) intermediates with sluggish redox reactions and uncontrolled precipitation behavior. Herein, we report a semiliquid cathode composed of an active LPS solution/carbon nanofiber (CNF) composite layer, capped with a carbon nanotube (CNT) thin film decorated with metallic Mo nanoclusters that regulate the electrochemical redox reactions of LPS. The trace amount (0.05 mg cm–2) of metallic Mo on the CNT film provides sufficient capturing centers for the chemical immobilization of LPS. Together with physical blocking of LPS by the compact CNT film, free diffusion of LPS is significantly restrained and the self-discharge behavior of the Li–S cell is thus effectively suppressed. Importantly, the metallic Mo nanoclusters enable fast catalytic conversion of LPS and regular deposition of lithium sulfide. As a result, the engineered cathode exhibits a high active sulfur utilization (1401 mAh g–1 at 0.1 C), stable cycling (500 cycles at 1 C with 0.06% decay per cycle), high rate performance (694 mAh g–1 at 5 C), and low self-discharge rate (3% after 72 h of rest). Moreover, a high reversible areal capacity of 4.75 mAh cm–2 is maintained after 100 cycles at 0.2 C for a cathode with a high sulfur loading of 7.64 mg cm–2. This work provides significant insight into the structural and materials design of an advanced sulfur-based cathode that effectively regulates the electrochemical reactions of sulfur species in high-energy Li–S batteries.

Suppressing the Shuttle Effect and Dendrite Growth in Lithium–Sulfur Batteries

“…[20][21][22][23] Functionalizing both sides of commercially available separators is considered to be a facile/effective strategy in controlling the interfacial reactions of both the multielectron conversion of sulfur/polysulfide and the lithium deposition/dissolution, further boosting the overall battery performance. [24][25][26] For this purpose, some asymmetric separator structures have been developed recently to satisfy the distinct requirements of both the cathode and the anode sides. 20,27,28 However, the majority of these separators has shown difficulties to maintain the inherent pore structures of the separator itself during the charging/discharging process, representing a constraint for the high-flux Li + diffusion.…”

Nano Polymorphism‐Enabled Redox Electrodes for Rechargeable Batteries

“…To date, many types of materials, including metals (e.g., Pt, Fe, Ni, and Co), oxides (e.g., MnO 2 Ti 4 O 7 , VO 2 , Fe 3 O 4 , TiO 2− x , and WO 3− x ), sulfides (e.g., CoS 2 , Mo 6 S 8 , MoS 2 , WS 2 , Sb 2 S 3 , VS 4 , and Co 3 S 4 ), nitrides (e.g., VN, Co 4 N, and TiN), phosphides (e.g., MoP and Ni 2 P), carbides (e.g., TiC, NbC, and W 2 C), metal‐free compounds (e.g., black P, doped carbon, BN, and C 3 N 4 ), and their derived heterostructured materials (e.g., TiO 2 /MXenes) have been studied as effective catalysts for boosting the oxygen vacancy conversion reactions in Li–S batteries. [ 332–340 ] Furthermore, some emerging research directions on this topic include i) the rational design of heterostructured materials (e.g., TiO 2 /Ni 3 S 2 ) as bidirectional catalysts for both oxidation and reduction reactions, [ 341 ] ii) the use of single atom/clusters‐based catalysts (e.g., Zn/MXenes and Mo/CNTs) capable of maximizing catalytic ability, [ 342,343 ] and iii) the design of catalyst–electrolyte interfaces for strong chemisorption and good electrocatalytic activity. [ 344,345 ] Despite the significant progress in the field of Li–S batteries, in‐depth mechanistic investigations on the fundamental polymorphism transition manipulation and catalytic activity in Li–S batteries are lacking, and are expected to be conducted in the future using advanced visual characterization techniques.…”

“…ability, [342,343] and iii) the design of catalyst-electrolyte interfaces for strong chemisorption and good electrocatalytic activity. [344,345] Despite the significant progress in the field of Li-S batteries, in-depth mechanistic investigations on the fundamental polymorphism transition manipulation and catalytic activity in Li-S batteries are lacking, and are expected to be conducted in the future using advanced visual characterization techniques.…”

Metal‐Organic Frameworks Derived Multidimensional CoP/N, P‐Doped Carbon Architecture as an Efficient Electrocatalyst for Overall Water Splitting

“…[17,18] However, their electrocatalytic activity is still not satisfactory due to low active-surface exposure and insufficient electrical conductivity. [19][20][21][22] Hybridizing CoP with low-dimensional carbonaceous nanomaterials (e. g. carbon nanotube, [23][24][25] graphene oxide, [26][27][28][29] porous carbon, [30][31][32] carbon nanofiber [33] ) has been regarded as a "one-stone-two-birds'' strategy to boost the catalytic activity since it not only exposes massive surface-active sites, but also improves electrical conductivity. Some recent studies have pronounced that heteroatom doping (e. g. N and P) is capable of tuning the electronic structure and further enhancing the catalytic performance of CoP/carbon composites.…”

“…Transition‐metal phosphides (TMPs), in particular, cobalt phosphide materials, have shown a hydrogenase‐like catalytic mechanism to be a class of attractive catalysts for water electrocatalysis [17,18] . However, their electrocatalytic activity is still not satisfactory due to low active‐surface exposure and insufficient electrical conductivity [19–22] …”