A Robust Ion-Conductive Biopolymer as a Binder for Si Anodes of Lithium-Ion Batteries

Binders have been reported to play a key role in improving the cycle performance of Si anode materials of lithium-ion batteries. In this study, the biopolymer guar gum (GG) is applied as the binder for a silicon nanoparticle (SiNP) anode of a lithium-ion battery for the first time. Due to the large number of polar hydroxyl groups in the GG molecule, a robust interaction between the GG binder and the SiNPs is achieved, resulting in a stable Si anode during cycling. More specifically, the GG binder can effectively transfer lithium ions to the Si surface, similarly to polyethylene oxide solid electrolytes. When GG is used as a binder, the SiNP anode can deliver an initial discharge capacity as high as 3364 mAh g(-1), with a Coulombic efficiency of 88.3% at the current density of 2100 mA g(-1), and maintain a capacity of 1561 mAh g(-1) after 300 cycles. The study shows that the electrochemical performance of the SiNP anode with GG binder is significantly improved compared to that of a SiNP anode with a sodium alginate binder, and it demonstrates that GG is a promising binder for Si anodes of lithium-ion batteries.