title: A pomegranate-inspired nanoscale design for large-volume-change lithium battery anodes.
abstract: Silicon is an attractive material for anodes in energy storage devices, because it has ten times the theoretical capacity of its state-of-the-art carbonaceous counterpart. Silicon anodes can be used both in traditional lithium-ion batteries and in more recent Li-O2 and Li-S batteries as a replacement for the dendrite-forming lithium metal anodes. The main challenges associated with silicon anodes are structural degradation and instability of the solid-electrolyte interphase caused by the large volume change (∼300%) during cycling, the occurrence of side reactions with the electrolyte, and the low volumetric capacity when the material size is reduced to a nanometre scale. Here, we propose a hierarchical structured silicon anode that tackles all three of these problems. Our design is inspired by the structure of a pomegranate, where single silicon nanoparticles are encapsulated by a conductive carbon layer that leaves enough room for expansion and contraction following lithiation and delithiation. An ensemble of these hybrid nanoparticles is then encapsulated by a thicker carbon layer in micrometre-size pouches to act as an electrolyte barrier. As a result of this hierarchical arrangement, the solid-electrolyte interphase remains stable and spatially confined, resulting in superior cyclability (97% capacity retention after 1,000 cycles). In addition, the microstructures lower the electrode-electrolyte contact area, resulting in high Coulombic efficiency (99.87%) and volumetric capacity (1,270 mAh cm(-3)), and the cycling remains stable even when the areal capacity is increased to the level of commercial lithium-ion batteries (3.7 mAh cm(-2)).
authors: 1] Department of Chemistry, Stanford University, Stanford, California 94305, USA [2].
authors: Nian
authors: N
authors: Liu
authors: 1] Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, USA [2].
authors: Zhenda
authors: Z
authors: Lu
authors: Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, USA.
authors: Jie
authors: J
authors: Zhao
authors: Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, USA.
authors: Matthew T
authors: MT
authors: McDowell
authors: Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, USA.
authors: Hyun-Wook
authors: HW
authors: Lee
authors: Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, USA.
authors: Wenting
authors: W
authors: Zhao
authors: 1] Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, USA [2] Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA.
authors: Yi
authors: Y
authors: Cui