Current Status and Future Prospects of Metal–Sulfur Batteries

Abstract

that makes use of intercalation materials as the electrodes (Figure 1), applications involving electric vehicles and smart grids may require rechargeable batteries with new battery chemistries that can generate even higher energy densities for longer driving ranges and higher energy-storage capabilities. [6][7][8] Additionally, the lithiated transition-metal oxides used in commercial lithium-ion battery cathodes tend to be expensive, scarce, or toxic to the environment. Thus, it is desirable to explore new electrode materials that are naturally abundant (and therefore less expensive) as well as environmentally compatible in order to successfully enter the future battery markets. [6,[8][9][10][11] This driving force has promoted the development of batteries with conversionreaction electrodes, in which reversible electrochemical reactions take place and new chemical compounds form during the cycling of the battery. Naturally abundant materials, such as sulfur for the cathode, can be applied as electrodes. Different metallic anodes have shown great potential in coupling with sulfur cathode to generate a high energy density, including lithium metal [3,10,[12][13][14][15][16][17]31] as well as other alkali [18][19][20][21][22][23][24]31] and high-valent metals. [18,[25][26][27][28][29][30][31] As a next-generation energy-storage technology beyond lithium-ion batteries, lithium-sulfur batteries are the most promising low-cost, high-capacity energy-storage device available due to their high charge-storage capacity, low cost, and the wide availability of sulfur. [32][33][34][35] The electrochemical reactions of lithium-sulfur batteries involve reversible conversions between sulfur (S 8 ), lithium polysulfides (Li 2 S x , x = 4-8), and lithium sulfides (Li 2 S 2 and Li 2 S). [33][34][35][36] The conversions between sulfur and lithium polysulfides and lithium sulfides involve phase changes between liquid-state polysulfides and solid-state sulfur and sulfides. [35][36][37][38][39][40] Thus, the conversion reaction of lithium-sulfur battery chemistry has no restriction in maintaining the initial crystal chemistry of the electrode during electrochemical cycling. [39][40][41][42] Therefore, a full twoelectron redox reaction per sulfur atom can occur in a manner that is both reversible and stable, increasing the chargestorage capacity drastically as compared to the currently used insertion-reaction oxide cathodes. [7,[39][40][41][42] As a result, sulfur cathodes possess a high theoretical charge-storage capacity of 1672 mA h g −1 , which is the highest value among solid-state Lithium-sulfur batteries are a major focus of academic and industrial energystorage research due to their high theoretical energy density and the use of low-cost materials. The high energy density results from the conversion mechanism that lithium-sulfur cells utilize. The sulfur cathode, being naturally abundant and environmentally friendly, makes lithium-sulfur batteries a potential next-generation energy-storage technology. The current state of the rese...

A Li2S‐TiS2‐Electrolyte Composite for Stable Li2S‐Based Lithium–Sulfur Batteries

“…[18,19,49,53] Besides enhancing the reaction kinetics, TiS 2 can also immediately adsorb any polysulfides generated from the surrounding Li 2 S, and these stabilized polysulfides can then function as catholyte to benefit the cyclability and high-rate performance of the high-loading cathode. [2,3,[7][8][9] After investigating the obvious morphological differences between the Li 2 S-E and Li 2 S-TiS 2 -E cathodes, we applied different electrochemical analytical tools to explore the activation and cycling performance of the cells (Figure 3). The cycled Li 2 S-E control cathode displays unreacted bulk Li 2 S covered by Adv.…”

“…[22,49] The high impedance brought about by the Li 2 S-E composite causes an obvious diffusion impedance at the low frequency region, [22,45,56] possibly due to the low conductivity of the Li 2 S coating layer formed on the current collector. [2,7,20,30] TiS 2 ameliorates these problems due to Adv. [22,52,53,56] In Figure 3c and Figure S8 (Supporting Information), the cycled Li 2 S-E cathode displays increased resistance from 300 to Adv.…”

“…[1][2][3][4][5] Lithium-sulfur batteries are appealing to fulfill these needs as a result of their high charge-storage capacity and low cost. [1][2][3][4][5] Lithium-sulfur batteries are appealing to fulfill these needs as a result of their high charge-storage capacity and low cost.…”

“…However, nanoparticles are more sensitive to air and moisture and tend to aggregate, [7,[25][26][27] resulting in high resistance. [2,3] A result of these is a low amount of active material in the cathode (e.g., a Li 2 S loading of <2.0 mg cm −2 and Li 2 S content of <60 wt%) and a high amount of electrolyte in the cell (e.g., high electrolyte/Li 2 S ratio of > 20/1). [2,3] A result of these is a low amount of active material in the cathode (e.g., a Li 2 S loading of <2.0 mg cm −2 and Li 2 S content of <60 wt%) and a high amount of electrolyte in the cell (e.g., high electrolyte/Li 2 S ratio of > 20/1).…”

“…[28,29] The degradation of both the anode and the cathode results in a fast capacity fade and short cycle life. [2,3,30] To overcome these challenges, various approaches have been proposed to reduce the overpotential associated with the high activation overpotential of Li 2 S as well as to limit the instability and inefficiency caused by the insulating nature of Li 2 S and the irreversible diffusion of polysulfides. [2,3,30] To overcome these challenges, various approaches have been proposed to reduce the overpotential associated with the high activation overpotential of Li 2 S as well as to limit the instability and inefficiency caused by the insulating nature of Li 2 S and the irreversible diffusion of polysulfides.…”