Eliminating Solvents and Polymers in High-Performance Si Anodes by Gas-Phase Assembly of Nanowire Fabrics

摘要

Developing sustainable battery electrode manufacturing methods is particularlypressing for alloying-type active materials, such as silicon, whichoften require additional energy-intensive and solvent-based processing toreinforce them with a buffer matrix. This work introduces a new methodto fabricate Si anodes as continuous, tough fabrics of arbitrary thickness,without processing solvents, polymeric binders, carbon additives, or anyreinforcing matrix. The anodes consist of percolated networks of long Sinanowires directly assembled from suspension in the gas phase, where theyare grown via floating catalyst chemical vapor deposition. A high Si contentabove 75 wt. in a textile-like network structure leads to high-performanceelectrode properties. Their gravimetric capacity is 2330 mAh g~(-1) at C/20 forall thicknesses produced, reaching areal capacities above 9.3 mAh cm~(-2) atC/20 and 3.4 mAh cm~(-2) at 1C (with 3.4 mg cm~(-2)). Analysis of rating data givesa high transport coefficient (6.6 × 10~(-1)2 m~2 s~(-1)) due to a high out-of-planeelectrical conductivity (0.6 S m~(-1)) and short solid-state diffusion length. Siremains a percolated network of elongated elements after extended cycling,preserving electrical conductivity and leading to a capacity retention of 80after 100 cycles at C/5 and ≈60 after 500 cycles at C/2. When integratedwith an NMC111 cathode, a full cell gravimetric energy density of 480 Wh kg~(-1)is demonstrated.