Lithium–Sulfur Battery Cathode Design: Tailoring Metal‐Based Nanostructures for Robust Polysulfide Adsorption and Catalytic Conversion

Abstract

portable electronic devices such as laptops and mobile phones. However, with the increasing demand for clean energy and portable electronics, the energy densities powered by the LIB (≈300 mAh g −1 ) are beginning to reach the threshold limit and thus, leading to a need for an alternate environmentally friendly and more economical energy storage technology with higher energy densities. [1] One of the most promising candidates for the LIB replacement is the lithium-sulfur (Li-S) battery, which utilizes the redox reaction between sulfur and lithium. Compared to LIB and other metal-sulfur batteries (Figure 1a), Li-S batteries are profiled as a viable energy storage technology stemming from their high specific energy capacity of 1675 mAh g −1 and superior energy density of around 2670 Wh kg −1 . [1a-d,2] The elemental sulfur, which is used as the cathode material, also has a multitude of auspicious properties such as its inexpensiveness, environmentally friendliness, abundancy and non-toxicity. [2d,3] In addition, another emerging battery system is the metal-air battery, which is a half-open system that utilize oxygen from ambient air as the active cathode material. Thus, Li-S batteries are comparatively safer due to their enclosed system. Apart from that, the influence of CO 2 , H 2 O, and N 2 in ambient air can lead to chemical instability in metal-air batteries. [4] Taking Li-air batteries as an example, the presence of CO 2 leads to the formation of Li 2 CO 3 , which is more chemically stable than Li 2 O 2 and causes a larger charge overpotential, hence leading to decomposition issues of electrolytes. [5] Nevertheless, progress for the real-world usage of Li-S batteries is currently hindered by multiple drawbacks. First, despite its manifold advantages, sulfur and its discharge products (Li 2 S or Li 2 S 2 ) are inherently insulating with low conductivities of 10 −7 to 10 −30 S cm −1 at room temperature, rendering it unbefitting to be directly used as the cathode. [6] Second, the inevitable volume expansion of the electrode (≈80%) due to the contrasting densities of S 8 and Li 2 S causes structural damage during the charge/discharge cycle. [7] Third, the "polysulfide shuttle effect" would occur, whereby the soluble higher order polysulfides (Li 2 S 4 to Li 2 S 8 ) dissolve in the electrolyte and migrate between the anode and the cathode, leading to its Lithium-sulfur (Li-S) batteries have a high specific energy capacity and density of 1675 mAh g −1 and 2670 Wh kg −1 , respectively, rendering them among the most promising successors for lithium-ion batteries. However, there are myriads of obstacles in the practical application and commercialization of Li-S batteries, including the low conductivity of sulfur and its discharge products (Li 2 S/Li 2 S 2 ), volume expansion of sulfur electrode, and the polysulfide shuttle effect. Hence, immense attention has been devoted to rectifying these issues, of which the application of metal-based compounds (i.e., transition metal, metal phosphides, sulfides, oxides, carbides...

A current overview of the oxidative desulfurization of fuels utilizing heat and solar light: from materials design to catalysis for clean energy

“…In the field of catalysis, metal oxides with a Lewis acid characteristic are prominent and inveterate catalysts that speed up most important reactions, such as oxidation and acid-base reactions, compensating for the drawback of poor selectivity. 58,59 Significantly, metal oxides have been advocated to replace precious metals such as Pt 60 and Au 61 in performing ODS to counter the high price and restricted availability that are stumbling blocks to their industrial application. In line with previous research, various relatively economical metal oxides, such as MoO 3 , WO 3 , Co 3 O 4 , MnO 2 and so on, have been highlighted as promising candidates for fuel purification via ODS.…”

Multisize CoS2 Particles Intercalated/Coated‐Montmorillonite as Efficient Sulfur Host for High‐Performance Lithium‐Sulfur Batteries

“…[3,9] In view of this issue, many polar metal-based compounds, such as metal oxides, metal sulfides and metal nitrides, have attracted a lot of attention and have been introduced into sulfur cathodes, which could not only improve the chemisorption of LiPSs, but also accelerate the reaction kinetics of the sulfur-polysulfide-Li 2 S transition, thus effectively inhibiting the shuttle effect. [4,[10][11][12] As a typical transition metal disulfide, cobalt disulfide (CoS 2 ) possesses a high conductivity of up to 6.7 × 10 3 S cm À 1 at 300 K, which greatly exceeds those of most other first-row transition metal disulfides. [13] This high conductivity enables CoS 2 to provide efficient electron pathways and high electrocatalytic activity for LiPSs redox reactions.…”

A Powerful One‐Step Puffing Carbonization Method for Construction of Versatile Carbon Composites with High‐Efficiency Energy Storage

“…[5][6][7][8] Currently, the scientific community is still eager for advanced carbon-based materials to achieve higher efficiency and better utilization of green energy. [9][10][11][12][13] To date, various carbonaceous materials (e.g., graphene, [14][15][16][17][18] carbon nanotubes, [19,20] C 60 , [21] carbon quantum dots [22] and carbon micro/nanofibers [23] ) and their composites have been explored and prepared by different methods including chemical vapor deposition, [23,24] chemical or electrochemical exfoliation, [25] and electrospinning, [26,27] but it is still a great challenge to fabricate versatile advanced carbon-based composites with controlled morphology, adjustable dimension and tunable composition by one-step synthesis process in large scale.The traditional preparation methods (e.g., direct annealing method, chemical vapor deposition (CVD) method, a sputtering method, hydrothermal/ solvothermal methods) for carbon and their composites are always multi-steps, which make it very difficult to precisely control morphology, dimension, and composition at the same time. [28][29][30] Meanwhile, limited by the equipment, the above methods are still suffering from high product cost and low yield, which further hinder their largescale commercial applications.…”