Catalytic Polysulfide Conversion and Physiochemical Confinement for Lithium–Sulfur Batteries

Abstract

involved, and affordable cost. [1][2][3] However, the commercial application of the sulfur cathode for the Li-S batteries is restrained by several technical barriers [4][5][6] compared with Li-ion battery. [7] First, the poor conductivity of sulfur and its reaction intermediates limit the sulfur utilization, [8] which leads to decreased energy density and power density. Second, during the charge/discharge process, there is a large volume change, resulting in rapid deterioration of the electrode structure. Various strategies have been investigated to increase electrode conductivity and to accommodate the volume expansion. [9][10][11] Last but not least, the dissolution and transport of lithium polysulfides (LiPSs) in the electrolyte result in the fatal "shuttle effect" that causes the deposition of Li 2 S on Li anode and then degrades the cycle performance. This shuttle effect could be mitigated by 1) trapping/confining the soluble LiPSs in the cathode by physical and chemical adsorption, [12][13][14][15] which prevents the transport of soluble LiPSs in the electrolyte, and 2) enhancing the kinetics of LiPS conversion reactions so that the soluble long-chain LiPS could transform to insoluble short-chain LiPS quickly, limiting the lifetime of soluble LiPS. [16,17] Therefore, a superior Li-S battery could be achieved by designing a cathode with high electricalThe lithium-sulfur (Li-S) battery is widely regarded as a promising energy storage device due to its low price and the high earth-abundance of the materials employed. However, the shuttle effect of lithium polysulfides (LiPSs) and sluggish redox conversion result in inefficient sulfur utilization, low power density, and rapid electrode deterioration. Herein, these challenges are addressed with two strategies 1) increasing LiPS conversion kinetics through catalysis, and 2) alleviating the shuttle effect by enhanced trapping and adsorption of LiPSs. These improvements are achieved by constructing double-shelled hollow nanocages decorated with a cobalt nitride catalyst. The N-doped hollow inner carbon shell not only serves as a physiochemical absorber for LiPSs, but also improves the electrical conductivity of the electrode; significantly suppressing shuttle effect. Cobalt nitride (Co 4 N) nanoparticles, embedded in nitrogen-doped carbon in the outer shell, catalyze the conversion of LiPSs, leading to decreased polarization and fast kinetics during cycling. Theoretical study of the Li intercalation energetics confirms the improved catalytic activity of the Co 4 N compared to metallic Co catalyst. Altogether, the electrode shows large reversible capacity (1242 mAh g −1 at 0.1 C), robust stability (capacity retention of 658 mAh g −1 at 5 C after 400 cycles), and superior cycling stability at high sulfur loading (4.5 mg cm −2 ).

Room‐Temperature Sodium–Sulfur Batteries and Beyond: Realizing Practical High Energy Systems through Anode, Cathode, and Electrolyte Engineering

“…For instance, DFT calculations are first performed for materials with potential polysulfide confinement and/or catalytic properties. [ 221–223 ] Electrochemical tests are then carried out, with the reaction mechanisms probed in operando using techniques such as in situ Raman spectroscopy and synchrotron X‐ray diffraction (XRD). [ 134,141,142,224 ] The mechanistic insights gleaned then serve as input for improving subsequent iterations.…”

Strong Chemical Interaction between Lithium Polysulfides and Flame‐Retardant Polyphosphazene for Lithium–Sulfur Batteries with Enhanced Safety and Electrochemical Performance

“…[ 1–3 ] Nevertheless, there are several intractable scientific and technical problems such as the dissolution of lithium polysulfides (LiPS) in electrolyte, non‐electric conductivity and serious volume expansion of sulfur, impeding the practical application of Li–S batteries. [ 4–6 ] To break through these bottlenecks, many strategies have been used to enhance the electrochemical performance of Li–S batteries such as constructing host materials of sulfur cathode, [ 6–9 ] modifying functional separators, [ 10,11 ] introducing interlayers, [ 12–14 ] adding electrolyte additive, [ 15–17 ] and using new binders. [ 18,19 ] Chen and coworkers synthesized a yolk–shelled carbon@Fe 3 O 4 nanoboxes as highly efficient sulfur host for Li–S batteries, delivering high specific capacity, excellent rate capacity, and long cycling stability.…”

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.…”