Progress and Prospect of Practical Lithium-Sulfur Batteries Based on Solid-Phase Conversion

Abstract

Lithium–sulfur (Li–S) batteries hold great promise in the field of power and energy storage due to their high theoretical capacity and energy density. However, the “shuttle effect” that originates from the dissolution of intermediate lithium polysulfides (LiPSs) during the charging and discharging process is prone to causing continuous irreversible capacity loss, which restricts the practical development. Beyond the traditional Li–S batteries based on the dissolution-diffusion mechanism, novel Li–S batteries based on solid-phase conversion exhibit superior cycling stability owing to the absolute prevention of polysulfides shuttling. Radically eliminating the formation of polysulfides in cathodes or cutting off their diffusion in electrolytes are the two main ways to achieve solid-phase conversion. Generally, direct transformation of sulfur to final Li2S without polysulfides participation tends to occur in short-chain sulfur polymers or special molecular forms of sulfur substances, while specific regulations of liquid electrolytes with solvating structure or solid-state electrolytes can effectively suppressing the polysulfides dissolution. In this review, we systematically organized and summarized the structures and approaches to achieve solid-phase conversion, introduce their preparation methods, discuss their advantages and disadvantages, and analyze the factors and effects of different structures on battery performances. Finally, the problems demanding a prompt solution for the practical development of solid-phase conversion-based Li–S batteries, as well as their future development direction, are suggested.

Self-Structured Binder Confinement of Sulfur for Highly Durable Lithium-Sulfur Batteries

“…They were then decommissioned at either 2.3 or 2.0 V. These potentials were selected according to the voltage profile of sulfur during discharge with two signature plateaus, as observed in Figure . The upper plateau that appears at 2.3 V corresponds to the onset of the solid-to-liquid transformation in elemental sulfur converting to long-chain polysulfides (Li 2 S x , X = 4, 6, 8), and the lower plateau that appears at 2.0 V corresponds to the liquid-to-solid transformation of the long-chain polysulfides to the short-chain polysulfides (Li 2 S x , X = 1, 2). − Next, the cells were disassembled, and the cathode-facing side of their separators was characterized using Raman spectroscopy. Figure a,b compares the representative Raman spectra of the conventional-doctor blade and CBAD-spray separators at 2.3 and 2.0 V, respectively.…”

The future nickel metal supply for lithium-ion batteries

“…66 Elemental doping is an effective method by introducing small amounts of foreign atoms into a crystal lattice to improve the stability of cathode materials. 67 Elemental doping can strengthen the chemical bond between metal and oxygen, inhibit the rock salt phase formation, decrease oxygen loss, alleviate anisotropic lattice collapse, and restrain cation mixing. Elemental doping consists of cation, anion and multielement co-doping.…”

Reversible Solid–Solid Conversion of Sulfurized Polyacrylonitrile Cathodes in Lithium–Sulfur Batteries by Weakly Solvating Ether Electrolytes

“…In conventional dilute ether electrolytes (using high solvating power ether), conversion of SPAN involves "solid-liquid" transformation, accompanied by the generation and dissolution of polysulfides and obvious shuttle effect. [19][20] Consequently, the SPAN cathode suffers from rapid capacity fading in ordinary ether electrolytes. While SPAN undergoes a reversible "solid-solid" conversion in the carbonate electrolyte (such as ethylene carbonate/diethyl carbonate electrolytes), it directly converts solid phase sulfur into insoluble lithium sulfides (Li 2 S)/ lithium disulfide (Li 2 S 2 ) without the dissolution or shuttling of polysulfides.…”