Tailoring Cathode-Electrolyte Interface for High-Power and Stable Lithium-Sulfur Batteries

Abstract

Global interest in lithium-sulfur batteries as one of the most promising energy storage technologies has been sparked by their low sulfur cathode cost, high gravimetric, volumetric energy densities, abundant resources, and environmental friendliness. However, their practical application is significantly impeded by several serious issues that arise at the cathode-electrolyte interface, such as interface structure degradation including the uneven deposition of Li₂S, unstable cathode-electrolyte interphase (CEI) layer and intermediate polysulfide shuttle effect. Thus, an optimized cathode-electrolyte interface along with optimized electrodes is required for overall improvement. Herein, we comprehensively outline the challenges and corresponding strategies, including electrolyte optimization to create a dense CEI layer, regulating the Li₂S deposition pattern, and inhibiting the shuttle effect with regard to the solid-liquid-solid pathway, the transformation from solid-liquid-solid to solid-solid pathway, and solid-solid pathway at the cathode-electrolyte interface. In order to spur more perceptive research and hasten the widespread use of lithium-sulfur batteries, viewpoints on designing a stable interface with a deep comprehension are also put forth.

Keywords: Cathode–electrolyte interface; Lithium–sulfur batteries; Reaction pathway; Shuttle effect; Structural enhancement.

Fig. 1

a Radar chart comparing key parameters of LSB and LIB [, –25]. b Network of potential challenges and strategies of cathode–electrolyte interface throughout the reports of LIBs in the past decade

Fig. 2

a Schematic internal configuration illustration of LIBs. Reproduced with permission from Ref. [71], Copyright 2011, Royal Society of Chemistry. b GCD curves of LiCoO₂ cathode of LIBs. Reproduced with permission from Ref. [72], Copyright 2022, Royal Society of Chemistry. c Redox reactions of LiCoO₂ cathode of LIBs [73]. d Schematic internal configuration illustration of LSBs. Reproduced with permission from Ref. [74], Copyright 2018, Royal Society of Chemistry. e Representative GCD curves of LSBs in the ether-based electrolyte. Reproduced with permission from Ref. [75], Copyright 2020, American Chemical Society. f Corresponding redox reactions of S cathode of LSBs. Reproduced with permission from Ref. [76], Copyright 2022, John Wiley and Sons

Fig. 3

a Diagram of CEI formation mechanism and process for SPAN in LPF-carbonate and LFSI-ether electrolytes. Reproduced with permission from Ref. [86], Copyright 2022, American Chemical Society. b Schematic illustration of the evaporation treated, melt-infiltrated composite, and Ketjenblack/S cathode during initial discharge process of CEI formation. Reproduced with permission from Ref. [89], Copyright 2020, John Wiley and Sons. c Schematic illumination of fractured CEI layer with an excessive S content. Reproduced with permission from Ref. [90], Copyright 2022, John Wiley and Sons

Fig. 4

a The “nucleation–proliferation–growth” model of Li₂S. Reproduced with permission from Ref. [91], Copyright 2023, John Wiley and Sons. b Illustration of Li₂S 2D growth. Reproduced with permission from Ref. [95], Copyright 2023, John Wiley and Sons. c Deposition of Li₂S on non-electrocatalytic surface. Reproduced with permission from Ref. [98], Copyright 2022, Elsevier

Fig. 5

a Schematic illustration of shuttle effect. Reproduced with permission from Ref. [99], Copyright 2020, Springer Nature. b Schematic illustration of examples of improper hosts like TiO₂-carbon nanofibers (CNFs)/S and Co/CoN-CNFs/S causing shuttle effect. c Cycling performance with TiO₂-CNFs/S, Co/CoN-CNFs/S, and NC@TiO₂-CNFs/S as host, respectively. b, c Reproduced with permission from Ref. [102], Copyright 2023, John Wiley and Sons

Fig. 6

a Lithiation of the S with graphene hosts and RDFs of S–S atom pairs of lithiation of the S with graphene hosts at different times. Reproduced with permission from Ref. [43], Copyright 2024, Elsevier. b Schematic illustration of the fundamental functions of capacity control on the cycle life evolution of cells. Reproduced with permission from Ref. [106], Copyright 2022, Elsevier. c TFSI⁻ and FSI⁻ anion on FeS₂@3DNPC electrodes. Reproduced with permission from Ref. [112], Copyright 2022, Elsevier. XPS S 2p spectra of polyacrylonitrile (SPAN) cathode cycled in d 1 M LiTFSI and e 1 M LiTFSI-0.5 M LiNO₃ in 1,3-dioxolane (DOL)/1,2-dimethoxyethane (DME). d, e Reproduced with permission from Ref. [109], Copyright 2019, Elsevier. f The schematic illustration of how LiHFDF suppresses dissolution/shuttling of LSBs. Reproduced with permission from Ref. [113], Copyright 2020, John Wiley and Sons. g Schematic structure component of CEI layer formed in 1 M LiFSI/DME-EC. Reproduced with permission from Ref. [114], Copyright 2021, American Chemical Society. h The relationship between the thickness of the CEI layer and LiTFSI concentration. Reproduced with permission from Ref. [115], Copyright 2023, John Wiley and Sons

Fig. 7

a Hydrogen NMR spectra of TFMSA and TFMSA + Li₂S. b Positive effects of the TFMSA additive at electrode–electrolyte interfaces in the LSBs. a, b Reproduced with permission from Ref. [117], Copyright 2022, Elsevier. c Schematic diagram of enhancement effect of SL adding. d High-resolution S 2p XPS spectra of cathode surface with SL in 1 M LiTFSI in DOL/DME with 0.2 M LiNO₃ containing different content of SL. c, d Reproduced with permission from Ref. [118], Copyright 2020, Elsevier. e Schematic illustration of 2D progressive nucleation (2DP)/2D instantaneous (2DI) (BFT models) and 3D progressive (3DP)/3D instantaneous (3DI) (SH models) (x–y is parallel to the substrate; y–z is vertical to the substrate). Reproduced with permission from Ref. [119], Copyright 2019, John Wiley and Sons. f Schematic diagram of 3D growth of Li₂S induced by high donor number (DN) anions. g Comparison of the charge and discharge capacities for 80 charge/discharge cycles at 0.2 C. The electrolyte consists of 0.2 M LiPSs, based on Li₂S₈ and 1 M lithium salt Li_X, X = TFSI⁻, Tf⁻, or Br⁻/0.2 M LiNO₃/DOL: DME (1:1). f, g Reproduced with permission from Ref. [120], Copyright 2019, Springer Nature. h Li₂S deposition morphologies in the cathode for the LiTFSI, LiBr, and LiSCN electrolytes after discharge at 0.05 C and 0.4 C. Reproduced with permission from Ref. [121], Copyright 2023, John Wiley and Sons

Fig. 8

a Schematic illustration of the nucleation behavior of Li₂S on G@MNNPs and b SEM images of G@MNNPs and G@MNNL after potentiostatic 5000 s discharge. a, b Reproduced with permission from Ref. [122], Copyright 2021, John Wiley and Sons. c Schematic conversions from LiPSs to Li₂S on the Mo₂N and SND-Mo₂N surfaces, respectively, and d their long-term cyclability for 550 cycles at 0.5 C. c, d Reproduced with permission from Ref. [123], Copyright 2021, American Chemical Society. e Charge density difference of SA-Cu@N-doped graphene (NG)/Li₂S. f Schematic illustrations of Li₂S deposition process on CNF (top) and N-doped carbon fiber foam (SA-Cu@NCNF) (bottom) substrates. e, f Reproduced with permission from Ref. [124], Copyright 2022, Elsevier. g Schematic illustration of the growing pathway of Li₂S in the absence (blue arrows) and presence (red arrows) of cobaltocene (CoCp₂). Reproduced with permission from Ref. [125], Copyright 2019, John Wiley and Sons

Fig. 9

The schematic of a synthesis procedure and b strong interaction with LiPSs during the charge/discharge process of FeS/N–C@S nanocomposite cathode. a, b Reproduced with permission from Ref. [128], Copyright 2021, Elsevier. c Schematic preparation of F-S@NOC composite. Reproduced with permission from Ref. [130], Copyright 2018, Elsevier. d Schematic comparison between the traditional 2D carbon/S and bubble-like ICFs/nS cathodes. Reproduced with permission from Ref. [131], Copyright 2017, American Chemical Society. e Cycling performance comparison between the HMCS/S composite and HMCS/S@GO cathodes. Reproduced with permission from Ref. [132], Copyright 2022, Royal Society of Chemistry. f Self-caging mechanism for the growth of yolk-shell graphene@S particles. Reproduced with permission from Ref. [133], Copyright 2021, John Wiley and Sons

Fig. 10

a Schematic illustrations of S adsorption and catalyzation on NC, LDH, and PPy@LDH. b Long-term cycling performance of the PPy@LDH-S cathodes with different S loadings in cells. a, b Reproduced with permission from Ref. [141], Copyright 2023, John Wiley and Sons. c Schematic illustrations of synthesis and d LiPSs trapping mechanism of 1 T-MoS₂-S@PPy cathode. c, d Reproduced with permission from Ref. [135], Copyright 2022, Elsevier. e The fabrication process of o-PEDOT modified S cathode. f Cycling performances of Li–S pouch cells with the P2 and PE cathodes, respectively. e, f Reproduced with permission from Ref. [145], Copyright 2023, Elsevier

Fig. 11

a Binding energy scope of categorized adsorbents to LiPSs. Reproduced with permission from Ref. [148], Copyright 2022, John Wiley and Sons. b Adsorption configuration of Li₂S on anatase-TiO₂ (101) surface. Reproduced with permission from Ref. [154], Copyright 2016, Royal Society of Chemistry. c Schematic preparation of the S@TCP/MCs electrode. Reproduced with permission from Ref. [155], Copyright 2023, John Wiley and Sons

Fig. 12

a Schematic illustration of the synthesis of 3D S-CNT@MXene cage spheres. b UV/vis spectra of the Li₂S₆, CNT with Li₂S₆ and CNT@MXene with Li₂S₆. a, b Reproduced with permission from Ref. [162], Copyright 2021, Elsevier. Reduction of Li₂S₈/Li₂S₆ and precipitation of Li₂S during potentiostatic discharge of the Li₂S₈/tetraglyme catholyte on c CC and d Ti₃C₂T_x@CC at 2.05 V. c, d Reproduced with permission from Ref. [163], Copyright 2021, Elsevier

Fig. 13

a CV curves of the Li-SPAN half cells in 1 M LiFSI/DME and 1 M LiFSI/DME-EC electrolytes, respectively. Reproduced with permission from Ref. [114], Copyright 2021, American Chemical Society. b Solvate structure illustrations of the HCE (left) of LiTFSI + DEC and the LHCE (right) of LiTFSI + DEC + TTE, in which the LiTFSI, DEC, and TTE are used as examples for salt, solvent, and diluent, respectively. c Schematic illustration of the in situ formation of the CEI layer on the KB/S surfaces in the localized high-concentration carbonate-based electrolyte. d S K-edge spectra of KB/S electrodes in the carbonate LHCE at given discharge/charge steps and the corresponding GCD curve of the cell; XPS spectra of the electrode at given discharge states: S 2p, C 1s. b-d Reproduced with permission from Ref. [166], Copyright 2021, John Wiley and Sons. e The superiorities of the proposed DPGDME electrolyte toward both electrodes. Reproduced with permission from Ref. [169], Copyright 2022, Elsevier. f Illustration of Li⁺-solvent interactions. g Conversion mechanism of SPAN in weakly solvating ether electrolyte. f, g Reproduced with permission from Ref. [170], Copyright 2023, John Wiley and Sons

Fig. 14

a Schematic diagram of alucone coating on carbon/S (ring-S₈) cathode and b proposed reaction mechanism in the carbonate electrolyte. a, b Reproduced with permission from Ref. [171], Copyright 2018, Springer Nature. c D-SEIs are formed on the interfaces of the anode and cathode. Reproduced with permission from Ref. [172], Copyright 2021, Springer Nature. d Schematic diagram of the SGPOF with a short S-chain. Reproduced with permission from Ref. [173], Copyright 2021, American Chemical Society. e Schematic structures of S/C cathode following solid–liquid–solid reaction with LiPSs dissolution (above) and the organosulfur cathode (below) following solid–solid reaction with eliminated shuttle effect, as well as the structural reorganization of organosulfur cathode during the reaction process. Reproduced with permission from Ref. [174], Copyright 2023, Elsevier. f Calculation of energy changes of possible lithiation reactions, bond length, and reaction formula for CH₃–S–S–S–CH₃ (Reaction 1) and CH₃–S–S–CH₃ (Reaction 2), and their proposed electrochemical conversions. Reproduced with permission from Ref. [175], Copyright 2022, Elsevier

Fig. 15

The challenges, strategic examples, and novel visions of the electrode–electrolyte interface of LSBs. Reproduced with permission from Ref. [177], Copyright 2023, Elsevier; Ref. [178], Copyright 2021, Elsevier; Ref. [179], Copyright 2019, American Chemical Society; Ref. [115], Copyright 2023, John Wiley and Sons; Ref. [180], Copyright 2022, American Chemical Society; Ref. [181], Copyright 2016, American Chemical Society; Ref. [128], Copyright 2021, Springer Nature; Ref. [182], Copyright 2023, MDPI; Ref. [183], Copyright 2020, Springer Nature; Ref. [184], Copyright 2018, Springer Nature; Ref. [160], Copyright 2019, Springer Nature; Ref. [185], Copyright 2023, Springer Nature; Ref. [186], Copyright 2023, Springer Nature; Ref. [187], Copyright 2018, Springer Nature; Ref. [176], Copyright 2019, Springer Nature; and Ref. [188], Copyright 2019, Springer Nature