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A high lithium conductive MoS /Celgard composite separator is reported as efficient polysulfides barrier in Li-S batteries. Significantly, thanks to the high density of lithium ions on MoS surface, this composite separator shows high lithium conductivity, fast lithium diffusion, and facile lithium transference. When used in Li-S batteries, the separator is proven to be highly efficient for depressing polysulfides shuttle, leading to high and long cycle stability. With 65% of sulfur loading, the device with MoS /Celgard separator delivers an initial capacity of 808 mAh g and a substantial capacity of 401 mAh g after 600 cycles, corresponding to only 0.083% of capacity decay per cycle that is comparable to the best reported result so far. In addition, the Coulombic efficiency remains more than 99.5% during all 600 cycles, disclosing an efficient ionic sieve preventing polysulfides migration to the anode while having negligible influence on Li ions transfer across the separator. The strategy demonstrated in this work will open the door toward developing efficient separators with flexible 2D materials beyond graphene for energy-storage devices.

Conventional technology for the purification of organic solvents requires massive energy consumption, and to reduce such expending calls for efficient filtration membranes capable of high retention of large molecular solutes and high permeance for solvents. Herein, we report a surface-initiated polymerization strategy through C-C coupling reactions for preparing conjugated microporous polymer (CMP) membranes. The backbone of the membranes consists of all-rigid conjugated systems and shows high resistance to organic solvents. We show that 42-nm-thick CMP membranes supported on polyacrylonitrile substrates provide excellent retention of solutes and broad-spectrum nanofiltration in both non-polar hexane and polar methanol, the permeance for which reaches 32 and 22 l m h bar, respectively. Both experiments and simulations suggest that the performance of CMP membranes originates from substantially open and interconnected voids formed in the highly rigid networks.

are widely used to trap LiPSs via N-Li + interaction, [4,[26][27][28] meanwhile B doping is demonstrated to improve the performance of S/carbon cathode in Li-S batteries due to the strong interaction between PS anions and positively polarized boron in the porous carbon. [29] Despite the fact that heteroatom doping enhances PSs trapping in the cathodes, the trapping efficiency is still limited due to constrained surface area and low doping ratio. In addition, the poor order and broad size distribution of pores in amorphous porous carbons have become major impediment to uniform sulfur distribution and redeposition. In order to get high doping ratio while ensuring high surface area and ordered pore structure for regular sulfur distribution, Tarascon and co-workers pioneered the use of metal-organic frameworks (MOFs) as host materials for sulfur storage, taking advantage of the weak binding between the PSs and the oxygenated framework. [30] Moreover, Zheng et al. [31] and Zhou et al. [32] also reported the Lewis acid-base interactions between PSs and MOFs, which helped decreasing shuttle effect. Nevertheless, the utilization of MOFs is still limited by their poor thermal stability and heavy metal sites, which increase the density of host and thus decrease the energy density of batteries. Recently, Liao et al. proposed utilization of N-doped covalent organic framework (COF) (CTF-1), an organic porous material with low density, small pore size, and large surface area, as host material for sulfur storage. [33] However, this N-doped COF shows only moderate PSs trapping efficiency due to lack of strong interaction between PSs and N-rich pore surface. Considering COFs are porous materials that allow precise control of pore size and surface, as well as homogeneous impregnation of active species in the pores, there is great opportunity to rationally design effective COFs as hosts to store sulfur and fully confine the mobile redox PS species. Although, Lee and co-workers have recently adopted the composite structure of microporous COF-1 grown on mesoporous carbon nanotube as a new interlayer for chemical trapping of PSs in Li-S batteries, the introduction of carbon nanotubes can give rise to complexity to fully probe the electrochemical properties of COFs. [34] Till now, the positive B and negative O double doped boronate ester COFs have never been used as sulfur hosts in Li-S batteries, which is a distinctly different conception from interlayer use.Here, we suggest using boronate ester COFs as the improved trapping matrices for enhanced adsorption of LiPSs. The high density and uniform distribution of positively polarized B and negatively polarized O within the pores guarantee simultaneous adsorption of S x 2− and Li + in soluble LiPSs and thus render sulfur redeposition more uniform. As a result, this new host shows unprecedentedly strong adsorption ability and hence efficiently traps LiPSs within the cathodes. Such unique feature distinguishes boronate ester COF system from other N-doped As one of the most promising energy...