Accordion Frameworks Enable Free-Standing, High Si Content Anode for Li-ion Batteries

Implementing high-performance silicon (Si) anode in actual processing and application is highly desirable for next-generation, high-energy Li-ion batteries. However, high content of inactive matrix (including conductive agent and binder) is often indispensable in order to ensure local conductivity and suppress pulverization tendency of Si particles, which thus cause great capacity loss based on the mass of whole electrode. Here, we designed an accordion-structured, high-performance electrode with high Si content up to 95%. Si nanoparticles were well anchored into the interlayer spacings of accordion-like graphene arrays, and free-standing electrode was prepared via a simple filtration process without any binder. Conductive accordion framework ensures strong confinement effect of Si nanoparticles and also provides direct, non-tortuous channels for fast electrochemical reaction kinetics. As a consequence, the accordion Si electrodes exhibit ultrahigh, electrode-based capacities up to 3149 mAh g⁻¹ (under Si content of 91%), as well as long-term stability. Also, the accordion electrode can bear extreme condition of over-lithiation and maintains stable in full-cell test. This design provides a significant stride in high Si content toward realistic, high-performance electrodes.