1 Introduction

Rapidly depleting fossil fuel resources coupled with increasing environmental pollution has accelerated the pace of develo** environmentally sustainable and high-energy–density renewable energy [1,2,3]. Lithium-ion batteries (LIBs), as a new clean energy source, have become important energy storage candidates in the electronic and communication equipment market [4]. However, their restricted energy density (150–240 Wh kg−1) and lack of memory retention render them unsuitable for deployment in grid and hybrid/electric vehicle. Recently, lithium–sulfur (Li–S) batteries, as rechargeable batteries incorporating multi-electron chemistry, have garnered intensive attention [5,6,7]. Their theoretical capacity (1675 mAh g−1) is much higher than that of LIBs (e.g., 274 mAh g−1 for lithium cobalt oxide (LiCoO2)), and even surpasses those of selenium and tellurium-based batteries (678 and 419 mAh g−1, respectively). Moreover, sulfur is abundant and environmentally friendly, making Li–S batteries competitive for widespread deployments [8]. Even though Li–S batteries possess appealing advantages, several challenges still limit their practicality: (i) the intrinsic electrical insulation (5 × 10–30 S cm−1) and volumetric expansion of sulfur; (ii) the reaction between the Li anode and the electrolyte resulting in unstable solid electrolyte interphase formation (SEI) and dendrite formation due to non-homogeneous nucleation at anode; (iii) the shuttling effect initiated by the polysulfides dissolution [9].

To solve the aforementioned problems, improvements have been made to different components of the battery [10,11,12,13,42,43], catalysts with double defects [44,50]. Moreover, tailoring electrolyte systems to construct an anode SEI layer [51] and a cathode solid electrolyte interphase (CEI) layer form on both electrodes by molecular regulation of electrolytes using optimal solvents/co-solvents [51,52,53,54,55], highly concentrated electrolytes (HCE) [56,57,58,59,60,61], and electrolyte additives [62, 63], etc. with various numbers of anchoring sites which significantly improved the stability of the Li anode interface, controlled the kinetics of sulfur redox, and suppressed side reactions toward polysulfides. Consequently, there is an improvement in the retention rate of capacity.

Extensive research has gone into the development of efficient strategies to inhibit the shuttling effect and achieve excellent performance in Li–S batteries [64,65,66]. Several reviews have summarized the design of cathode materials, high-sulfur loading, the inhibition of shuttle effect on the anode or electrolyte [67], etc. However, a comprehensive and systematical review regarding the strategies for suppressing the shuttling effect for all components of Li–S batteries is lacking and desired, especially for their practical application in future commercialization. In this review, we center on the shuttle effect issues and suppressing strategies in Li–S batteries (Fig. 1). We will first discuss the electrochemical principles and shuttle effect of Li–S batteries to give an overview of the mechanism and original of the shuttle effect. The designed principles for prohibiting LPS shuttle will be elaborated, including boosting the sulfur conversion rate of sulfur, confining sulfur or LPS within cathode host, confining LPS in the shield layer, and preventing LPS from contacting the anode, which offers guidance for further design novel materials of Li–S batteries. Then, we summarize the inhibition of shuttle effect from all components in Li–S batteries (cathode, electrolyte, separator and anode) with the above-designed principles. Finally, the prospects for inhibition of the shuttle effect and future development directions in Li–S batteries will be elucidated.

Fig. 1
figure 1

Schematic illustrations of the strategies and operation mechanisms for inhibiting LPS shuttling starting

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2 Electrochemical Principles and Shuttle Effect of Li–S Batteries

A typical half Li–S cell comprises sulfur cathode, separator, electrolyte, and lithium metal anode. And a conversion-type working mechanism is inherited during charge/discharge process. Specifically, each sulfur atom undergoes a complete two-electron redox reaction:

$${\text{S}}_{8} \; + \;16{\text{Li}}^{ + } \; + \;16e^{ - } \; \leftrightarrow \;8{\text{ Li}}_{2} \;{\text{S}}$$
(1)

As shown in Fig. 2a, Li–S batteries typically show two plateaus during discharging, wherein S electrochemically reduces to Li2S via soluble intermediate polysulfides, i.e., Sk−2 (4 ≤ k ≤ 8), relating to a “solid–liquid-solid” process. Specifically, the discharge voltage plateaus at ~ 2.35 V contribute to 25% of the total theoretical specific capacity (419 mAh g−1). The electrochemical reduction of this part goes through two stages. Initially, solid S8 transforms into soluble higher-order Li2S8 upon reaction with migrating Li-ions and electrons, relating to the reaction of converting between solid–liquid [68]. Subsequently, the highly soluble higher-order Li2S8 tends to be disproportionate in the aprotic electrolytes and lower-order polysulfide anions (Sk−2, k > 4) produced by single-phase liquid–liquid reactions. The low discharge voltage plateaus (< 2.1 V) represent a further reduction of these lower-order intermediate polysulfides to solid state products (Li2S2/Li2S), which contributes to the 75% of the total specific capacity (~ 1256 mAh g−1). This part undergoes a two-stage electrochemical reduction as well. In the first stage, soluble lower-order polysulfides are reduced to insoluble Li2S2 or Li2S, and this process is a slow two-phase reaction involving liquid–solid phases [85]. Copyright 2012, Wiley–VCH. (Color figure online)

a XRD pattern and b Fourier-transformed Mo K-edge EXAFS spectrum of 1D chain-like MoS3 [82].

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