1000 Wh L-1 lithium-ion batteries enabled by crosslink-shrunk tough carbon encapsulated silicon microparticle anodes

Microparticulate silicon (Si), normally shelled with carbons, features higher tap density and less interfacial side reactions compared to its nanosized counterpart, showing great potential to be applied as high-energy lithium-ion battery anodes. However, localized high stress generated during fabrication and particularly, under operating, could induce cracking of carbon shells and release pulverized nanoparticles, significantly deteriorating its electrochemical performance. Here we design a strong yet ductile carbon cage from an easily processing capillary shrinkage of graphene hydrogel followed by precise tailoring of inner voids. Such a structure, analog to the stable structure of plant cells, presents 'imperfection-tolerance' to volume variation of irregular Si microparticles, maintaining the electrode integrity over 1000 cycles with Coulombic efficiency over 99.5%. This design enables the use of a dense and thick (3 mAh cm(-2)) microparticulate Si anode with an ultra-high volumetric energy density of 1048 Wh L-1 achieved at pouch full-cell level coupled with a LiNi0.8Co0.1Mn0.1O2 cathode.

Automated summary

This study presents a method to enhance the electrochemical performance of microparticulate silicon by designing a strong and ductile carbon cage using capillary shrinkage of graphene hydrogel. The stable structure, similar to plant cells, shows 'imperfection-tolerance' to irregular volume variation of Si microparticles, maintaining electrode integrity over 1000 cycles with high Coulombic efficiency. The dense and thick microparticulate Si anode achieved an ultra-high volumetric energy density of 1048 Wh L-1 at pouch full-cell level.