Recent Advances on Modification of Separator for Li/S Batteries

Abstract

Significant research efforts have been dedicated to progressing Li/S batteries owing to the active material’s superior capacity and abundancy. Yet, one of the major drawbacks of the Li/S battery relates to the separator part since it is a crucial component that directly influences its electrochemical performance. The reversible capacity, Coulombic efficiency, and cycling stability of Li/S batteries can all be increased by rationally constructing and improving commercially available separators. To date, various modifications on the separator surface have been proposed to enhance the electrochemical performance of Li/S batteries. Thus, this review mainly focuses on major problems of Li/S batteries and their resolving methods by advancing these separators. Enhancement of separators are categorized as physical and chemical based on modification technique types. In the physical modification section, different types of coatings using carbon, polymer, inorganic, and metal–organic framework (MOF) were comprehensively discussed. In contrast, relatively less work on chemical modification has been reported, yet a critical summary has been provided. The perspectives and challenges of separator modification for Li/S battery has been also proposed.

Application of Metal/Covalent Organic Frameworks in Separators for Metal‐Ion Batteries

“…The electrochemical stability of the separators can be evaluated by chronoamperometry, cyclic voltammetry (CV), and linear sweep voltammetry (LSV). [59][60][61] For example, the long-term electrochemical cycling stability of coating separator with NH 2 -MIL-125(Ti) was explored by testing symmetrical Li j Li cells which can sustain stable cycling for more than 1200 h at 1 mA cm À 2 -1 mAh cm À 2 . [62] The cycling performance is favourably comparable to other Li j Li cells reported in research acritical, [63][64][65] showing excellent electrochemical to stable Li metal electrodes.…”

“…Being electrochemically stable is also a critical determining factor to withstand voltage change under the oxidizing and reducing environment during the battery discharging and charging. The electrochemical stability of the separators can be evaluated by chronoamperometry, cyclic voltammetry (CV), and linear sweep voltammetry (LSV) [59–61] . For example, the long‐term electrochemical cycling stability of coating separator with NH 2 ‐MIL‐125(Ti) was explored by testing symmetrical Li|Li cells which can sustain stable cycling for more than 1200 h at 1 mA cm −2 –1 mAh cm −2 [62] .…”

Regulation of Li+ Diffusion via an Engineered Separator to Realize a Homogeneous Lithium Microstructure in Advanced Li-Metal Batteries

“…Li-ion batteries (LIBs) are of significant interest for the development of clean energy storage devices owing to the large growth in consumer electronic devices and electric vehicles. , However, commercial graphite anodes (372 mA h g –1 ) are unable to satisfy the increasing demand for high-energy-density LIBs. , Metallic Li, which possesses the highest theoretical specific capacity (3860 mA h g –1 ), lowest mass density (0.53 g cm –3 ), and low anode potential (−3.04 V vs. standard hydrogen electrode), is considered one of the most promising anode materials to overcome the energy density bottleneck of LIBs. − However, issues induced by the uneven dissolution/deposition behavior of the Li metal anode (LMA), including the growth of a dendritic Li, accumulation of a side-reaction “dead Li”, and infinite volume expansion of the electrode, have limited the practical application of Li-metal batteries (LMBs). − To overcome these problems, numerous strategies have been employed; these include (i) regulation of the electrolyte with functional additives or development of a solid-state electrolyte, − (ii) design of a three-dimensional (3D) structured anode with a large surface area, − (iii) introduction of an artificial solid electrolyte interface (SEI) at the electrode/electrolyte interface, , and (iv) modification of a separator. , …”

Regulating Electrocatalytic Polysulfides Redox Kinetics through Manipulating Surface Electronic Structure of Molybdenum-Based Catalysts for High-Performance Lithium-Sulfur Batteries

“…Lithium-sulfur (Li-S) battery is the most promising candidate for high-efficiency energy storage devices due to the high theoretical specific capacity of the cathode (1672 mAh g –1 ) and energy density of about 2600 Wh kg –1 , as well as abundant resources and environment-friendly sulfur. − Unfortunately, the intrinsic insulative properties of sulfur and lithium sulfides (Li 2 S 2 /Li 2 S), large volume expansion (78%) of the cathode during the charge/discharge process, particularly the serious ″shuttle effect″ of soluble lithium polysulfides (LiPSs) mediators, and the sluggish solid–liquid–solid conversion kinetics of sulfur species make it impossible to guarantee its life span, which impedes the further development of Li-S batteries. − Using electrocatalysts has recently been mentioned as the most powerful strategy to fundamentally solve the intractable issues above. − They can effectively accelerate the electrocatalytic transformation and improve the electrochemical performance of Li-S batteries.…”