A Temperature-Controlled Chemoswitching Aqueous Binder and In Situ Binding Strategy for Stabilizing SiOx Anodes of Lithium-Ion Batteries

Silicon oxide (SiO_x), as an anode material of lithium-ion batteries (LIBs), can discharge higher specific energy than graphite, but accommodating the structural damage caused by the stress change of lithiation/delithiation remains a challenge. In this work, poly(acrylic acid) (PAA) and polyethylenimine (PEI) have been used as the main body, where PAA as the initiator triggers the cross-linking reaction with PEI (cross-linker). While ammonia as the chemical switching agent (NH₃·H₂O) and carboxymethyl cellulose (CMC, thickener) served as the chemical switch for the whole cross-linking process, a temperature-controlled chemical switching aqueous binder has been developed for stabilizing SiO_x anodes for lithium batteries. The SiO_x anode with the temperature-controlled chemoswitching aqueous binder gives a reversible capacity of 1310 mAh g^–1 (81% capacity retention) after 400 cycles at 0.5 C. After 300 cycles at 2 C (25 °C) and 1 C (45 °C), the specific capacities are 1060 and 1039 mAh g^–1, respectively. This binding method can form strong intermolecular forces on the SiO_x surface and reduce the energy of lithium-ion diffusion. Quantitative simulations show that the energy to be overcome for lithium ion transfer trajectories is small in PEI@PAA. In addition, it avoids the premature cross-linking of binder precursors, ultimately improves the performance of the SiO_x anode, indicating promising application prospects.