“Nano-spring” confined in a shrinkable graphene cage towards self-adaptable high-capacity anodes

High-capacity Li-ion battery anode materials, normally coated with carbons, suffer from the issue of mismatch between the dynamic noncarbon cores and the static carbon shells upon lithiation and de-lithiation. Here, we build a self-adaptable electrical and mechanical carbon network by embedding the carbon nanotubes into a capillary-shrinking graphene hydrogel forming “nano-springs” to robustly connect and buffer the active noncarbon nanoparticles. This produced dense carbon cage can buffer the volume fluctuations of noncarbons and simultaneously retain a dynamic electrical connectivity with expanding/contracting noncarbon nanoparticles during charging and discharging. With this self-adaptable carbon structure for noncarbon nanoparticles (typically the tin oxide and silicon), high volumetric capacities (up to 1920 mAh cm−3) together with long cycle life (up to 600 cycles) and very limited electrode expansion are achieved in the nanosized yet compact noncarbon anode.