Highly Elastic Binders Incorporated with Helical Molecules to Improve the Electrochemical Stability of Black Phosphorous Anodes for Sodium-Ion Batteries

Black phosphorus has aroused attention as an attractive anode for sodium-ion batteries, because of its high theoretical capacity. Nevertheless, its practical application is hindered by the large volume expansion, which results in rapid capacity decay. Herein, we report that this challenge can be addressed by using an elaborately designed binder for the phosphorus-based electrodes. The incorporation of amylose molecules with helical structures endows the linear polyacrylic acid polymer binders with extraordinary stretchability and elasticity under 400 % strain. When it is applied as a binder for black-phosphorus-based anodes for sodium-ion batteries, the adhesion between the electrode and the current collector is much stronger (2.95 N) than that of the polyvinylidene difluoride (PVDF) binder based one (1.90 N). The electrode delivered a capacity as high as 1280 mAh g⁻¹ at 200 mA g⁻¹ after 300 cycles, which is better than the electrode with PVDF binder. Impressively, even after 1000 cycles, the electrode with our binder exhibits a capacity retention of 80 %. Our work sheds light on the significance of the rational design of effective binders and provides a new strategy to further improve the electrochemical performance of phosphorus-based materials for battery applications, which can be added on directly to other new electrode materials development strategies.