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finally to the poor performance of Li-S batteries. [1][2][3][4][5][6][7][8][9][10] The state-of-the-art separators used in Li-S batteries are commonly porous polypropylene (PP) films, but their pores are too large to restrict polysulfide shuttling (Figure 1a). Lots of efforts have been made to mitigate this shuttle effect by physical repulsion or chemical adsorption routes such as filling or covering the pores with polymers, [11][12][13][14] metal-organic frameworks (MOFs), [15] metal oxides, [16,17] graphene, [18][19][20] modified carbon nanotubes, [21,22] etc. (Figure 1b). Unfortunately, the filled or covered pores also restrict the transportation of Li + ions, increase the inner resistance, and finally deteriorate the performance of Li-S batteries.In this report, we propose a new strategy to selectively coordinate high-order polysulfides with "tertiary amine layer (TAL)" by which to simultaneously keep the pores of the separator still open to lithium ion's transportation. The construction of the polysulfide tongs is based on the classic "soft and hard acid-base (SHAB) theory." Different from the literature chemical interaction strategies, the anchoring groups to trap polysulfide are chemically grafted onto the PP separator, which is tough and stable. Also, the dissolved high-order Li 2 S x (x = 4, 6, and 8) can be more efficiently grasped when they try to diffuse across the narrowed but opening complex pores (Figure 1c). Li 2 S x species are relatively "soft" acids as the positive charges are mainly dispersed on the surface of the agglomerated polysulfide mole cules. Moreover, after the lithium ions are coordinated by sulfur, there are still "electron cloud holes" in Li 2 S x molecules to accept electrons from other molecules ( Figure S2, Supporting Information). In this regard, if we construct a "soft" base on the separator, the high-order Li 2 S x (x = 4, 6, and 8) soft acid can be grasped when they are further reduced and released in the cathode. On the contrary, lithium ion, which is commonly recognized as "hard" acid because of its small size and concentrated charge density, will be repulsed away by the "soft" base on the separator according to the SHAB theory. The chosen "soft" base for grasping polysulfide tong is tertiary amine (TA) group, which has a dispersed electron cloud and large head volume. TA group do not possess N-hydrogen atom, so we do not need to worry about the potential side reactions between active hydrogen and lithium-related compounds. Also, because the largest binding energy (E b ) between Li 2 S x Rechargeable lithium-sulfur batteries, which use sulfur as the cathode material, promise great potentials to be the next-generation high-energy system. However, higher-order lithium polysulfides, Li 2 S x (x = 4, 6, and 8), regardless of in charge or in discharge, always form first, dissolve subsequently in the electrolyte, and shuttle to the cathode and the anode, which is called "shuttle effect." The polysulfides shuttle effect leads to heavy loss of the active-sulfur materials. Literatu...

The Ti3C2@CF–S cathode features high sulfur loading capacity, strong polysulfide attachment, superior pulverization inhibiting properties, and demonstrates remarkable cycling stability.

High theoretical specific capacity and rich resources in nature make sulfur an ideal cathode material for lithium–metal batteries. However, the shuttle effect and sluggish reduction reaction kinetics of lithium polysulfides (LiPSs) seriously affect the performance of the batteries. Here, we report GO-d-Ti3C2T x MXene aerogels with a novel three-dimensional (3D) reticular structure that served as sulfur host cathode materials for lithium–sulfur batteries (LiSBs), which benefits adsorption/catalytic conversion of LiPSs simultaneously. The dissolved LiPSs can be rapidly captured through chemisorption and then catalyzed into insoluble Li2S by low-coordinated-state Ti on the d-Ti3C2T x MXene surface. The combination of adsorption and catalysis enormously improves the capacity and cycling performance of LiSBs. At an S mass loading of 1.5 mg cm–2, the cell with the S@GM0.4 composite electrode achieves excellent cycling performance. The discharge specific capacity of 1039 mA h g–1 (1.56 mA h cm–2) decays to 542.9 mA h g–1 after 1000 cycles with a capacity fading rate of 0.048% per cycle at 0.5 C. Even at an S mass loading of 4.88 mg cm–2, an areal capacity of 4.3 mA h cm–2 can be achieved at 0.2 C.

Li metal anodes, which possess ultrahigh theoretical capacity, are considered the ultimate solution for high energy density batteries. However, issues regarding safety and rapid electrode degradation due to Li dendrite...