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.