Rechargeable Zn-ion microbatteries emerge as a promising power solution due to their remarkable safety, high capacity, low cost, simple manufacturing, and environmental friendliness. Their fiber-shaped counterparts are particularly attractive due to their lightweight, tiny volume, and mechanical flexibility. However, it is still fundamentally challenging to construct high-performance fiber-shaped Zn-ion microbatteries (FZMB) because of the dendrite growth at the anode, the poor electrical conductivity of current cathode materials, the lack of suitable fiber substrates (high electrical conductivity and strong interaction with cathode materials).

We developed a simple and scalable process to fabricate dendrite-free fiber anodes by sputtering an ultrathin conductive carbon layer on rock-like Zn deposits around carbon fibers (CF) . The carbon layer plays a critical role in suppressing dendrites by uniformizing the surface electric field and provide additional surface and abundant nucleation sites. The obtained CF@Zn@C can stably run over 200h. Plus, we demonstrate a highly conductive and well-interacted fiber cathode, i.e., PEDOT: PSS@PANI core-sheath fiber, with a record high conductivity of 3676 S cm⁻¹. The superior conductivity enables a fast electron transfer which is beneficial to high rate performance. Based on the same PEDOT: PSS platform, we have fabricated the next-generation FZMB by using citriate as electrolyte additives to suppress the dendrite formation. Compared to the carbon layer on the Zn anode, the use of additives in the electrolyte is much easier in production. .