Rational design of stretchable and conductive hydrogel binder for highly reversible SiP₂ anode

The emerging SiP₂ with large capacity and suitable plateau is proposed to be the alternative anode for Li-ion batteries. However, typical SiP₂ still suffers from serious volume expansion and structural destruction, resulting in much Li-consumption and capacity fading. Herein, a novel stretchable and conductive Li-PAA@PEDOT:PSS binder is rationally designed to improve the cyclability and reversibility of SiP₂. Interestingly, such Li-PAA@PEDOT:PSS hydrogel enables a better accommodation of volume expansion than PVDF binder (e.g. 5.94% vs. 68.73% of expansivity). More specially, the SiP₂ electrode with Li-PAA@PEDOT:PSS binder is surprisingly found to enable unexpected structural recombination and self-healing Li-storage processes, endowing itself with a high initial Coulombic efficiency (ICE) up to 93.8%, much higher than PVDF binder (ICE = 70.7%) as well. Such unusual phenomena are investigated in detail for Li-PAA@PEDOT:PSS, and the possible mechanism shows that its Li-PAA component enables to prevent the pulverization of SiP₂ nanoparticles while the PEDOT:PSS greatly bridges fast electronic connection for the whole electrode. Consequently, after being further composited with carbon matrix, the SiP₂/C with Li-PAA@PEDOT:PSS hydrogel exhibits high reversibility (ICE> 93%), superior cyclability (>450 cycles), and rate capability (1520 mAh/g at 2000 mA/g) for LIBs. This highly stretchable and conductive binder design can be easily extended to other alloying materials toward advanced energy storage. © 2023 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences