Superelastic air-bubbled graphene foam monoliths as structural buffer for compressible high-capacity anode materials in lithium-ion batteries

Superelastic porous graphene foam monoliths (GFMs) constraining high-capacity anode electrode materials of GeO₂ nanoparticles (NPs) have been prepared by simple solution-processed approach and studied in lithium-ion batteries (LIBs). Through an optimization of GeO₂ content in the composite as 40% by weight, the GeO₂-NPs@GFM-2 anode shows a constant compressive stress of 14 kPa at a high strain of 90% for 200 cycles and simultaneously features a high specific capacity of 900 mAh g⁻¹ for at least 350 cycles. Based on its excellent flexibility and electrochemical properties, a compressible LIB is fabricated as a proof-of-concept when the GeO₂-NPs@GFM-2 is directly used as the binder-free anode and paired with a lithium metal. This compressive half cell is capable to deliver pressure-sensible power output under a range of compressive strains up to 90%, setting a new benchmark in area-specific capacity (5.76 mAh cm⁻²) for compressible/flexible LIBs with an energy density of 224.7 Wh kg⁻¹. Furthermore, we demonstrate the universality of this approach by replacing GeO₂ with Si nanoparticles to prepare compressible Si-NPs@GFM anode materials with high capacity and stability, validating GFMs as a general and efficient structure buffer for high-capacity anode materials in LIBs.