Tailoring Interfaces With Poly(Ionic Liquid)‐Grafted Porous Hybrid Molecular Brushes in Quasi‐Solid‐State Composite Electrolytes Enables Ultrahigh‐Rate and High‐Voltage Lithium Metal Batteries

ABSTRACT

Developing quasi‐solid‐state composite electrolytes (QSCEs) that combine high interfacial stability with rapid ion transport remains a key challenge for constructing long‐life, ultrahigh‐rate lithium metal batteries (LMBs). Herein, a highly interface‐stable and ion‐conductive QSCE (denoted as PSI) is developed by utilizing poly(ionic liquid)‐grafted porous silica hybrid molecular brush (SiO ₂ ‐ g ‐PILDFOB) as a multifunctional filler. The synergistic effect of boron and fluorine in poly(ionic liquid) side chains promotes the formation of a highly stable solid electrolyte interphase (SEI) and cathode electrolyte interphase (CEI), significantly enhancing interfacial compatibility with highly active electrodes. Meanwhile, porous silica provides continuous transport channels for lithium ions, substantially improving lithium‐ion transport efficiency. As a result, the Li|PSI|NCM9055 full cell achieves a long cycle life of 1000 cycles at an ultrahigh rate of 8 C. Moreover, under a high cut‐off voltage of 4.4 V, the Li|PSI|NCM9055 pouch cell with a high cathode loading (6.9 mg cm ⁻² ) exhibits a specific discharge capacity of 200.9 mAh g ⁻¹ at 0.7 C and demonstrates a long lifespan of 500 cycles. A 1.54 Ah pouch cell with an energy density of 413 Wh kg ⁻¹ can also be achieved by using high‐loading cathodes (21 mg cm ⁻² ). This work provides a feasible design strategy for developing ultrahigh‐rate and high‐voltage LMBs.