Amorphous nanosized silicon with hierarchically porous structure for high-performance lithium ion batteries

Silicon is a promising alternative anode material for high-performance lithium ion batteries (LIBs) because of its high specific capacity. However, the practical application is still hampered by poor cycle and rate performance because of the tremendous volume expansions/contractions during the lithium ions insertions/extractions. Here we report a hierarchically porous silicon anode consisting of uniformly dispersed nanoparticles with amorphous structure that has been electrodeposited successfully on the copper foil and been utilized directly for LIBs. The typical size of silicon particle is similar to 100-200 nm, which is beneficial for the fast lithium ions diffusion in a short distance. The hierarchical pores with interconnect channels are easy for the electrolyte filling and ions transports, and can offer sufficient space for the volume expansions of silicon anode during lithium ions insertions. Furthermore, the amorphous feature of the silicon nanoparticles can effectively release the stress from the lithiation-induced large volume expansions and enhance the structure stability, which are beneficial for the long cycling lifetime. Combing the highly conductive copper substrate, the free-standing silicon anode shows high reversible capacity of 1200 mA/g, excellent cycling stability (similar to 1000 mAh/g for 230 cycles) and outstanding rate performance (1000 and 600 mAh/g at 300 and 2000 mA/g, respectively). This study may pave a new way to develop silicon/copper composite materials as binder-free anodes for high-performance LIBs.