In Situ Construction of Crumpled Ti3C2Tx Nanosheets Confined S-Doping Red Phosphorus by Ti-O-P Bonds for LIBs Anode with Enhanced Electrochemical Performance

Red phosphorus (RP) with a high theoretical specific capacity (2596 mA h g-1) and a moderate lithiation potential (∼0.7 V vs Li+/Li) holds promise as an anode material for lithium-ion batteries (LIBs), which still confronts discernible challenges, including low electrical conductivity, substantial volumetric expansion of 300%, and the shuttle effect induced by soluble lithium polyphosphide (LixPPs). Here, S-NRP@Ti3C2Tx composites were in situ prepared through a phosphorus-amine-based method, wherein S-doped red phosphorus nanoparticles (S-NRP) grew and anchored on the crumpled Ti3C2Tx nanosheets via Ti-O-P bonds, constructing a three-dimensional porous structure which provides fast channels for ion and electron transport and effectively buffers the volume expansion of RP. Interestingly, based on the results of adsorption experiments of polyphosphate and DFT calculation, Ti3C2Tx with abundant oxygen functional groups delivers a strong chemical adsorption effect on LixPPs, thus suppressing the shuttle effect and reducing irreversible capacity loss. Furthermore, S-doping improved the conductivity of red phosphorus nanoparticles, facilitating Li-P redox kinetics. Hence, the S-NRP@Ti3C2Tx anode demonstrates outstanding rate performance (1824 and 1090 mA h g-1 at 0.2 and 4.0 A g-1, respectively) and superior cycling performance (1401 mAh g-1 after 500 cycles at 2.0 A g-1).

Polysulfide Rejection Strategy in Lithium-Sulfur Batteries Using an Ion-Conducting Gel-Polymer Interlayer Membrane

Lithium-sulfur batteries (LiSBs) are emerging as promising alternative to conventional secondary lithium-ion batteries (LiBs) due to their high energy density, low cost, and environmental friendliness. However, preventing polysulfide dissolution is a great challenge for their commercial viability. The present work is focused on preparing a lithium salt and ionic liquid (IL) solution (SIL) impregnated ion (lithium ion)-conducting gel-polymer membrane (IC-GPM) interlayer to prevent polysulfide migration toward the anode by using an electrostatic rejection and trapping strategy. Herein, we introduce an SIL-based freestanding optimized IC-GPM70 (70 wt % SIL) interlayer membrane with high lithium-ion conductivity (2.58 × 10^-3 S cm^-1) along with excellent thermal stability to suppress the migration of polysulfide toward the anode and prevent polysulfide dissolution in the electrolyte. Because of the coulombic interaction, the anionic groups, -CF₂ of the β-phase polymer host PVdF-HFP, TFSI^- anion of IL EMIMTFSI, and anion BOB^- of LIBOB salt, allow hopping of positively charged lithium ions (Li⁺) but reject negatively charged and relatively large-sized polysulfide anions (S_x^-2, 4 <x <8). The cationic group EMIM⁺ of the IL is electrostatically able to attract and trap the polysulfides in the interlayer membrane. Since the shuttle effect of lithium polysulfides in LiSBs has been suppressed by the prepared IC-GPM70 interlayer, the resulting lithium-sulfur cell exhibits significantly higher cycling stability (1200 cycles), rate performance (1343, 1208, 1043, 875, and 662 mAh g^-1 at 0.1C, 0.2C, 0.5C, 1C, and 2C, respectively), and structural integrity during cycling than its counterpart without the IC-GPM70 interlayer. The interlayer membrane has been found to improve the performance and durability of LiSBs, thus making them a viable alternative to conventional LiBs.