Hierarchical porous silicon structures with extraordinary mechanical strength as high-performance lithium-ion battery anodes

Porous structured silicon has been regarded as a promising candidate to overcome pulverization of silicon-based anodes. However, poor mechanical strength of these porous particles has limited their volumetric energy density towards practical applications. Here we design and synthesize hierarchical carbon-nanotube@silicon@carbon microspheres with both high porosity and extraordinary mechanical strength (>200MPa) and a low apparent particle expansion of 40% upon full lithiation. The composite electrodes of carbon-nanotube@silicon@carbon-graphite with a practical loading (3mAhcm(-2)) deliver 750mAhg(-1) specific capacity, <20% initial swelling at 100% state-of-charge, and 92% capacity retention over 500 cycles. Calendered electrodes achieve 980mAhcm(-3) volumetric capacity density and <50% end-of-life swell after 120 cycles. Full cells with LiNi1/3Mn1/3Co1/3O2 cathodes demonstrate >92% capacity retention over 500 cycles. This work is a leap in silicon anode development and provides insights into the design of electrode materials for other batteries.