Review—From Nano Size Effect to In Situ Wrapping: Rational Design of Cathode Structure for High Performance Lithium−Sulfur Batteries

Abstract

Rechargeable Li-S batteries have become attractive for next-generation energy storage technology due to their high specific energy, low cost, and materials earth abundance. However, the Li-S technology has not been successfully commercialized because of several outstanding challenges including fast capacity fading, low Coulombic efficiency, and limited rate capability. Over the past few years, considerable efforts have been devoted to solving the challenges associated with the sulfur cathode. In this mini review, we summarize our recent advances in Li-S cathodes, such as the understanding of the nano-size effect in sulfur materials, the design of polymer functional additives, and the realization of a novel in situ wrapping approach for Li-S cathodes. The current Li-S technology calls for a rational design of the Li-S cathode that can lead to excellent overall performance of Li-S batteries. Sulfur is a promising cathode material, which is highly earth abundant and with a theoretical specific capacity as high as 1672 mAh g −1 . When the sulfur cathode couples with a lithium metal anode to assemble rechargeable lithium-sulfur (Li-S) batteries, their theoretical specific energy density can reach 2600 Wh kg −1 , which is 3-5 folds higher than those of state-of-the-art Li-ion batteries.1-3 Because of the high energy density and low cost, rechargeable Li-S batteries are promising for applications not only in consumer electronics but also in energy storage and electric vehicles. [4][5][6] Although the research on Li-S batteries has been ongoing for over three decades, two major challenges still remain in this field: one is the low specific capacity due to high electrical resistivity of elementary S and the solid reduction products ((Li 2 S 2 and Li 2 S)) in the cathodes; the other is the fast capacity fading owing to the shuttle effect, i.e. polysulfide intermediates formed during discharge/charge cycles dissolve in the electrolyte, diffuse to the anode, react with Li metal, and form insoluble Li 2 S 2 and Li 2 S at the anodic region, leading to the loss of lithium metal and sulfur cathodic materials. 7,8 In the past few years, researches have mainly focused on designing nanostructured sulfur host materials to address challenges related to poor electrical conductivity of S/Li 2 S 2 /Li 2 S.9-19 A quantum leap for the nanostructure approach was the utilization of ordered mesoporous carbon CMK-3 to trap sulfur, as reported by Nazar et al. in 2009. 20 The conductive mesoporous carbon framework precisely constrains the growth of sulfur within its channels and thus enables fast electronic and ionic transport. Following this work, Cui et al. designed a series of sulfur nanostructures with complicated host materials demonstrating excellent electrochemical performances.9 Various nanostructured host materials, including but not limited to carbon/sulfur, 11,14,16,17,21 polymer/sulfur, [22][23][24] and metal oxide/sulfur composites 12,25,26 have been investigated. These nanostructures provide new merits and opportunities: (1)...

Suppressing the Polysulfide Shuttle Effect by Heteroatom-Doping for High-Performance Lithium–Sulfur Batteries

“…A lot of works have been conducted to depress the shuttle effect, which include cathode design and coating, separator modification, , use of a functional interlayer, , electrolyte adjustment, e.g., solid electrolyte, , “solvent-in-salt” strategy, and use of a functional lithium salt additive . Among all the above strategies, the integration of sulfur and various conductive carbon material, such as three-dimensional porous carbon materials, hollow carbon spheres, graphene oxides, carbon nanotubes (CNTs), microporous carbon, and their hybrids, − is a common strategy to obtain good electrical conductivity, excellent cycling stability, and outstanding rate performance.…”

Towards full demonstration of high areal loading sulfur cathode in lithium–sulfur batteries

“…The dissolution-precipitation of polysulfide intermediates determines the electrochemical performance of a working cell [30,35] . The recent advances in the high areal sulfur loading afford several emerging strategies for practical Li-S batteries [5,45,46] , however, the size of cathode is few mentioned. Herein we found the size of the cathode is an important factor.…”

Multiscale Understanding of Covalently Fixed Sulfur–Polyacrylonitrile Composite as Advanced Cathode for Metal–Sulfur Batteries

“…The porous layer allows the easy access of reactant ions or electrons to trigger active desired electrochemical reactions, while increasing the durability of the SPAN composite. [124][125][126] To increase the performance of the SPAN composite cathode, Hu et al [124] developed an in situ wrapping technique that blocked the polysulfide diffusion into the electrolyte. A mesoporous CMK-3/sulfur composite was initially prepared as the core of this architecture in this technique.…”