Ultra-efficient polymer binder for silicon anode in high-capacity lithium-ion batteries

As a highly promising anode material for high-capacity lithium-ion batteries (LIBs), the low electronic conductivity and large volume variation of silicon (Si) make the slurry-coating Si based electrode requiring high content of “inert” materials and suffering rapid capacity fading. Herein, a polyimine, synthesized via one-step condensation reaction, has been demonstrated as an ultra-efficient polymer binder that can resolve the above issues. The polyimine binder containing Si electrode delivers superior electrochemical performance: a delithiation specific capacity of 804.4 mAh g⁻¹ with capacity retention of 82.4% after 1000 cycles at the current density of 2 A g⁻¹. The high efficiency of polyimine binder for Si electrode has also been demonstrated with ultrahigh weight ratio of “active” material to “inert” material (R_A/I). The electrode with 95 wt% of Si (95Si/Polyimine, R_A/I = 19) reveals a reversible delithiation capacity of 2114 mAh g⁻¹ (capacity retention ~ 80.4%) over 200 cycles at the current density of 400 mA g⁻¹. Even at the high current density of 2 A g⁻¹, a delithiation capacity of 1087.8 mAh g⁻¹ after 500 cycles can be obtained. Molecular simulations and atomic force microscopy (AFM) indentation are utilized to investigate the ultra-efficiency of polyimine binder. With simple manufacturing process and ultra-efficient binder performance, the designed polyimine binder will be definitely meaningful in achieving low-cost and high-capacity LIBs with prolonged cycle life.