PVD Customized 2D Porous Amorphous Silicon Nanoflakes Percolated with Carbon Nanotubes for High Areal Capacity Lithium Ion Batteries
Integrating nanostructured Si materials into a freestanding membrane with high mechanical strength and continuous conductive network is a promising but challenging route to achieve high energy density lithium ion batteries (LIBs). Herein, we demonstrate that physical vapor deposition (PVD) customized two-dimensional (2D) porous amorphous Si nanoflakes, reinforced with ultralong multiwalled carbon nanotubes (MWCNTs), can be integrated into freestanding film electrode with high volumetric/areal capacity and energy density. Owing to the special 1D/2D nanotube/nanoflake entangled architecture, the freestanding Si-MWCNT film is highly porous, electrically conductive, and mechanically robust. Moreover, the interconnected MWCNT network functions as a spacer to prevent adjacent Si nanoflakes from restacking, and the 2D porous Si nanoflakes provide large electrode/electrolyte contact area, both of which enable fast Li+ transportation. Due to the existence of abundant pores in both amorphous Si nanoflakes (mesopores) and Si-MWCNT electrode (macropores), the volume change is significantly suppressed, resulting in stable electrodes with tunable mass loadings from 1.7 to 5.4 mg cm-2. When directly used as the anode electrode, the Si-MWCNT film with mass loading of 2.9 mg cm-2 exhibits a high specific capacity of 1556 mAh g-1 and areal capacity of 4.5 mAh cm-2. Remarkably, when coupling this freestanding anode with a commercial LiNi1/3Co1/3Mn1/3O2 (NCM) cathode, the full battery delivers a high gravimetric energy density of ~484.7 Wh kg-1. This study offers a promising and general route to design the freestanding electrodes by percolating CNTs with PVD generated 2D porous nanoflakes and provides significant insights for developing high energy battery systems.