The practical application of Li−S batteries has been greatly hindered by severe shuttle effects and sluggish kinetics. Anchoring soluble lithium polysulfides (LiPSs) onto host materials by chemisorption is an effective strategy for extending battery life. In this work, we performed systematic density functional theory calculations to evaluate the anchoring performance of O/F-covered MXene (M 2 TC 2 ) in lithium−sulfur batteries. Our results indicate that the moderate anchoring strength (∼2.5 eV), outstanding sulfur reduction performance (U L > −0.6 V), and low lithium ion diffusion barrier (<0.2 eV) of Mo 2 CF 2 and V 2 CF 2 make them promising host materials for LiPSs. We further revealed the determinants of the strength of binding of LiPSs to M 2 CT 2 . On the basis of the strong correlation among Q M , χ O/F , and E a , we established a "structure−property" equation to reveal the active origin of M 2 CT 2 . We expect that the framework established in this work will accelerate the development of Li−S batteries.
Polyacrylic acid (PAA) is a promising binder for the highcapacity Si anode. However, the one-dimensional structure of PAA could cause the linear molecular chains to slide from the Si surface during the charge− discharge processes, leading to insufficient suppression of the massive volume expansion of the Si anode. Herein, a soft−rigid dual chains' network of PAAsodium silicate (PAA-SS) was successfully constructed by cross-linking PAA and SS in situ at room temperature. The soft chains of PAA and the rigid chains of polysilicic acid synergistically ensure the enhanced adhesion property and mechanical strength. Therefore, the Si electrode with PAA-SS binder delivers a discharge capacity of 1559 mAh/g after 150 cycles at 4.2 A/g (1C) with an initial Coulombic efficiency of 93.2%. Moreover, the PAA-SS based SiC-500 electrode exhibits a discharge capacity of 441 mAh/g with the capacity retention of 88.2% after 500 cycles at 0.5 A/g, implying the PAA-SS binder's great industrial prospect in Si based electrodes.
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