Unity of Opposites between Soluble and Insoluble Lithium Polysulfides in Lithium–Sulfur Batteries

Abstract

Rechargeable batteries based on Li–S chemistry show promise as being possible for next‐generation energy storage devices because of their ultrahigh capacities and energy densities. Research over the past decade has demonstrated that the morphology of lithium polysulfides (LPSs) in electrolytes (soluble or insoluble) plays a decisive role in battery performance. Early studies have focused mainly on inhibiting the dissolution of LPSs and invested considerable effort to realize this objective. However, in recent years, a completely different view that the dissolution of LPSs during battery discharge/charge should be promoted has emerged. At this critical juncture in the large‐scale application of Li–S batteries, it is time to summarize and discuss both sides of the contradiction. Herein, an overview of these two opposite views pertaining to soluble and insoluble LPSs, including their historical environment, classical strategies, advantages, and disadvantages. Finally, the future morphology of LPSs in Li–S batteries is predicted based on a multiangle review of research studies conducted thus far, and the reasoning behind this conjecture is thoroughly discussed.

Low Concentration Electrolyte Enabling Cryogenic Lithium–Sulfur Batteries

“…However, the uniform redistribution of active sulfur can be facilitated after multiple cycles of solid-liquid conversion between long-chain polysulfides and elemental sulfur. [21] Then the limited redox reactions can be carried out owing to the improved interface kinetics involving the ion and electron contact, [23] leading to the presence of the second plateaus in discharge curves (Figure 4b, the 60th cycle). While for the cell using LCE at 0.2 C, it liberates a high discharge capacity of 711 mAh g −1 at 1st cycle and 652.9 mAh g −1 at 80th cycle, providing a clear second voltage plateau with smaller polarization (Figure 4a,b).…”

Building Better Lithium‐Sulfur Batteries—A Reassessment of the Working Mechanism

“…In addition, we notice that considerable amounts of excellent research has been devoted to suppressing the shuttle effect of neutral LiPSs by using adsorption strategy in the past few decades. [27] It is worth noting that the adsorption strategy generally include the design of polar S host materials, which has been considered as a prospective avenue for the shuttle behavior of neutral LiPSs. Obviously, the perspective of this work is contradictory with those design of positively charged polar materials that can effectively adsorb the neutral LiPSs.…”

Nickel vacancy tuning to tame polysulfide for Li–S batteries

“…To suppress the shuttle effect and enhance the electrochemical properties of Li–S batteries, researchers have focused on chemisorption and catalytic conversion of the LiPSs in recent years. 11 Carbon materials, 12 for example, with the introduction of polar hosts (heteroatoms, 13–17 polar functional groups, 18,19 metal–organic frameworks, 20,21 and covalent organic frameworks), 22–24 combine the advantages of high conductivity and surface polarity, thus enhancing the chemical absorption of polar LiPSs and confining the shuttle effect. Compared with modified carbon materials, transition metal alloys, 25,26 oxides, 27 hydroxides, 28 sulfides, 29,30 nitrides, 31–33 borides, 34 and carbides 35 demonstrate better catalytic ability to accelerate the kinetic conversion of LiPSs.…”