A Review of Functional Binders in Lithium–Sulfur Batteries

Abstract

Lithium–sulfur (Li–S) batteries have received tremendous attention due to their superior theoretical energy density of 2600 Wh kg−1, as well as the abundance of sulfur resources and its environmental friendliness. Polymer binders as an indispensable component in cathodes play a critical role in maintaining the structural integrity and stability of electrodes. Additionally, multifunctional polymer binders have been involved in Li–S batteries to benefit electrochemical performance by mitigating the shuttle effect, facilitating the electron/ion transportation, and propelling the redox kinetics. In the context of the significant impact of binders on the performance of Li–S batteries, recent progress in research on polymer binders in sulfur cathodes is herein summarized. Focusing on the functions and effects of the polymer binders, the authors hope to shed light on the rational construction of robust and stable sulfur cathode for high‐energy‐density Li–S batteries. Perspectives regarding the future research opportunities in Li–S batteries are also discussed.

Rational Design of Binders for Stable Li‐S and Na‐S Batteries

“…[7,12] Na-S battery, which also shows a high theoretical energy density (760 W h kg −1 ), [10,13] is very suitable for grid-scale storage as backup power because of the natural abundance of Na. [19] Driven by a deeper understanding of multi-phase conversion chemistry in the sulfur-based battery system, the role of the binder has shifted from simple mechanical stabilizer to electrochemical regulator which prevents the polysulfide shuttling and facilitates the electron-/ion-transport. This has led to several critical challenges including the physical shedding and electrical isolation of sulfur from current collectors, shuttle effect of polysulfide, low electrical conductivity, and large volumetric change of sulfur during the charge/discharge process that cause the irreversible capacity loss, low Coulombic efficiency, and short cycling life of sulfur cathodes.…”

“…[14][15][16] The cathodic charge/discharge reaction of Li-S and Na-S batteries involves the phase transitions of sulfur to metal sulfides based on the two-electron-transfer mechanism (xM + S 8 + 2e − → xM 2 S), which is largely different from the intercalation chemistry of conventional lithium metal oxide cathodes. [19][20][21] These advances have significantly enhanced the capacity and electrochemical stability of the sulfur cathodes. [15,17] Great efforts have focused on the design of the binder of the sulfur cathode to address the challenges in recent years.…”

Recent progress on biomass‐derived ecomaterials toward advanced rechargeable lithium batteries

“…In addition, as a critical component in electrode, the primary responsibility of polymer binders is to maintain the structural stability and integrity, which is the premise of constructing effective conductive framework and achieving lithiation/delithiation of active materials . Natural polymers are generally insoluble in organic electrolyte solutions.…”

“…Li dendrites can react with and consume limited liquid electrolyte, resulting in infertile and finally dry electrolyte condition in a working Li metal battery. Moreover, the generation and growth of Li dendrites have the possibility of permeating across separator and lead to battery short circuit, causing thermal runaway and final combustion or explosion of batteries . Gel polymer electrolytes that combine the advantages of highly interfacial infiltration of liquid electrolyte and high solidification strength of solid electrolyte have been regard as a promising strategy to mitigate safety hazards .…”

Sulfur‐Deficient TiS2‐x for Promoted Polysulfide Redox Conversion in Lithium‐Sulfur Batteries

“…[8,9] Up till now, advances are making in several respects, such as electrode structure, [10][11][12] electrolyte formulation, [13][14][15][16][17] membrane modification [18,19] and binder chemistry. [20] Thereinto, rational design of sulfur host material has made great strides. [21,22] Encapsulation of sulfur by physical adsorption [23][24][25] (carbon materials) or chemical adsorption [26,27] (polar compounds) is the most widely used method to enhance the electronic/ionic conductivity and stability of sulfur electrode.…”