Self-adaptive Gel Poly(imide-siloxane) Binder Ensuring Stable Cathode-Electrolyte Interface for Achieving High-Performance NCM811 Cathode in Lithium-ion Batteries

Optimizing the cathode-electrolyte interface is critical for Ni0.8Co0.1Mn0.1 O2 (NCM811) of high-energy lithium-ion batteries under the high voltage. Polymer binders that can guarantee the cathode integrity and interfacial stability of NCM811 are supposed to improve electrochemical performance. Here, a gel poly(imide-siloxane) (cPIS) binder is constructed by in-situ crosslinking of rigid polyimide with flexible aminopropyl terminated polydimethylsiloxane (DMS) precursors at room temperature. The rigid polyimide segments function as framework to comply with nonaqueous solvent-based commercial cathode fabrication, while the flexible DMS segments act as buffer to accommodate the stress-strain of cathode during long cycle life. In addition, DMS segments provide more lithium ions transfer sites and electrolyte affinity to boost lithium-ion diffusion. The rigid/flexible modulated 3D network binder with functional groups of amide units cooperatively assists the capability of binder self-adaptation, further guaranteeing the cathode-electrolyte interface integrity. As a result, NCM811 cathode with cPIS binder exhibits lower polarization and faster electrochemical kinetics. At 5 C in the voltage range of 2.5-4.3 V, the NCM811/cPIS cathode delivers a high specific capacity of 149.7 mAh g−1. NCM811/cPIS have capacity retentions of 100%, 87% and 65% after 100 cycles at ultrahigh cut-off voltages of 4.3, 4.5 and 4.7 V, respectively. This novel polymer binder provides a possible application for NCM811 cathode of high-energy lithium-ion batteries at high-voltage.