This study presents a photolithographable electrolyte for deeply rechargeable Zn microbatteries in on-chip devices. The electrolyte is composed of a UV-crosslinked polyacrylamide hydrogel containing ZnSO₄ and caffeine. Caffeine passivates the Zn anode, preventing chemical corrosion, and forms a Zn²⁺-conducting complex with Zn²⁺ ions, which transforms into ZnCO₃ and 2ZnCO₃·3Zn(OH)₂ during cycling. This Zn-rich interphase significantly enhances Zn reversibility. In on-chip microbatteries, the resulting solid-electrolyte interphase allows the Zn||MnO₂ full cell to cycle for over 700 cycles with an 80% depth of discharge. Integrating the photolithographable electrolyte into multilayer microfabrication creates a microbattery with a 3D Swiss-roll structure that occupies a footprint of 0.136 mm². This tiny microbattery retains 75% of its capacity (350 μAh cm⁻²) for 200 cycles at a remarkable 90% depth of discharge. The findings offer a promising solution for enhancing the performance of Zn microbatteries, particularly for on-chip microscale devices, and have significant implications for the advancement of autonomous microscale devices. The study demonstrates that caffeine can be spontaneously adsorbed to the Zn surface, passivating the Zn anode and preventing Zn chemical corrosion. The coordination complex formed between Zn²⁺ ions and caffeine molecules is Zn²⁺-conductive, which gradually transforms into Zn²⁺-conductive solids—ZnCO₃ and 2ZnCO₃·3Zn(OH)₂. This Zn-rich layer brings about a significant enhancement in Zn reversibility, with the Zn foil anode demonstrating remarkable reversibility even at a 90% DOD. The high efficiency of the caffeine additive in improving Zn reversibility was further evidenced in microscale devices. The caffeine additive inhibits the self-discharge of the on-chip Zn||MnO₂ microbattery and renders a cycling stability of >700 cycles at a DOD of 80%. More importantly, the research delves deeper into the realm of microfabrication by integrating the caffeine-containing photolithographable electrolyte into multilayer stacks, thereby enabling the creation of a 3D microbattery with a Swiss-roll architecture achieved through an on-chip self-assembly process. This Swiss-roll microbattery delivers an areal capacity of 350 μAh cm⁻² with a small footprint of 0.136 mm², and maintains an impressive 75% of its capacity over 200 cycles, evenThis study presents a photolithographable electrolyte for deeply rechargeable Zn microbatteries in on-chip devices. The electrolyte is composed of a UV-crosslinked polyacrylamide hydrogel containing ZnSO₄ and caffeine. Caffeine passivates the Zn anode, preventing chemical corrosion, and forms a Zn²⁺-conducting complex with Zn²⁺ ions, which transforms into ZnCO₃ and 2ZnCO₃·3Zn(OH)₂ during cycling. This Zn-rich interphase significantly enhances Zn reversibility. In on-chip microbatteries, the resulting solid-electrolyte interphase allows the Zn||MnO₂ full cell to cycle for over 700 cycles with an 80% depth of discharge. Integrating the photolithographable electrolyte into multilayer microfabrication creates a microbattery with a 3D Swiss-roll structure that occupies a footprint of 0.136 mm². This tiny microbattery retains 75% of its capacity (350 μAh cm⁻²) for 200 cycles at a remarkable 90% depth of discharge. The findings offer a promising solution for enhancing the performance of Zn microbatteries, particularly for on-chip microscale devices, and have significant implications for the advancement of autonomous microscale devices. The study demonstrates that caffeine can be spontaneously adsorbed to the Zn surface, passivating the Zn anode and preventing Zn chemical corrosion. The coordination complex formed between Zn²⁺ ions and caffeine molecules is Zn²⁺-conductive, which gradually transforms into Zn²⁺-conductive solids—ZnCO₃ and 2ZnCO₃·3Zn(OH)₂. This Zn-rich layer brings about a significant enhancement in Zn reversibility, with the Zn foil anode demonstrating remarkable reversibility even at a 90% DOD. The high efficiency of the caffeine additive in improving Zn reversibility was further evidenced in microscale devices. The caffeine additive inhibits the self-discharge of the on-chip Zn||MnO₂ microbattery and renders a cycling stability of >700 cycles at a DOD of 80%. More importantly, the research delves deeper into the realm of microfabrication by integrating the caffeine-containing photolithographable electrolyte into multilayer stacks, thereby enabling the creation of a 3D microbattery with a Swiss-roll architecture achieved through an on-chip self-assembly process. This Swiss-roll microbattery delivers an areal capacity of 350 μAh cm⁻² with a small footprint of 0.136 mm², and maintains an impressive 75% of its capacity over 200 cycles, even