Metallized polymer current collector as “stress acceptor” for stable micron-sized silicon anodes

Micron-sized silicon (μSi) is a promising anode material for next-generation lithium-ion batteries due to its high specific capacity, low cost, and abundant reserves. However, the volume expansion that occurs during cycling leads to the accumulation of undesirable stresses, resulting in pulverization of silicon microparticles and shortened lifespan of the batteries. Herein, a composite film of Cu-PET-Cu is proposed as the current collector (CC) for μSi anodes to replace the conventional Cu CC. Cu-PET-Cu CC is prepared by depositing Cu on both sides of a polyethylene terephthalate (PET) film. The PET layer promises good ductility of the film, permitting the Cu-PET-Cu CC to accommodate the volumetric changes of silicon microparticles and facilitates the stress release through ductile deformation. As a result, the μSi electrode with Cu-PET-Cu CC retains a high specific capacity of 2181 mA h g⁻¹, whereas the μSi electrode with Cu CC (μSi/Cu) exhibits a specific capacity of 1285 mA h g⁻¹ after 80 cycles. The stress relieving effect of Cu-PET-Cu was demonstrated by in-situ fiber optic stress monitoring and multi-physics simulations. This work proposes an effective stress relief strategy at the electrode level for the practical implementation of μSi anodes.