Cross-linking γ-Polyglutamic Acid as a Multifunctional Binder for High-Performance SiO_<i>x</i> Anode in Lithium-Ion Batteries

SiO_<i>x</i> is a highly promising anode material for realizing high-capacity lithium-ion batteries owing to its high theoretical capacity. However, the large volume change during cycling limits its practical application. The development of a binder has been demonstrated as one of the most economical and efficient strategies for enhancing the SiO_<i>x</i> anode's electrochemical performance. In this work, a multifunctional binder (T-PGA) is fabricated by cross-linking γ-polyglutamic acid (PGA) and tannic acid (TA) for SiO_<i>x</i> anodes. The introduction of TA into PGA helps to buffer the volume changes of the SiO_<i>x</i> anodes, facilitate diffusion of Li⁺, and construct stable SEI layers. Benefiting from this proposed binder, the SiO_<i>x</i> anode maintains a reversible capacity of 973.0 mAh g^-1 after 500 cycles at 500 mA g^-1 and the full cell, pairing with LiNi_0.5Co_0.2Mn_0.3O₂ cathode, delivers a reversible capacity of 133 mA h g^-1 (73.2% retention) after 100 cycles. This study offers valuable insights into advanced binders that are used in high-performance Li-ion batteries.