Reserve batteries fulfill a unique role among energy storage technologies in which long-term shelf life (years, decades) is required while ensuring optimal performance upon activation. This is typically achieved through isolation of the electroactive components until battery operation is required. Commonly, the electrolyte is isolated from one or both electrodes, and thus, limiting premature degradation and parasitic side-reactions until battery activation is desired. During the reserve battery activation process, electrolyte is delivered to the electrode(s), which enable ionic conduction between the anode and cathode, and thus permitting normal operations analogous to a non-reserve design. The feasible activation mechanisms are largely determined by battery chemistries and material properties, which give rise to several classifications including: thermal, spin-activated, and gas-activated reserve type batteries. Reserve battery activation under these various classifications require ancillary components and/or specific conditions which contribute excess complexity, weight, and/or volume towards the overall battery design and thus, significant penalties in reliability, specific and/or volumetric densities are incurred. Improvements in reserve battery technology must include strategies for limiting these penalties through innovated electrolyte delivery designs tailored for modern, high-energy, high-power density lithium-based batteries. Herein, we report a novel electrolyte delivery mechanism facilitated by an electrochemical aperture. The electrochemical aperture exists as a physical barrier, isolating the liquid, lithium-containing electrolyte. Reserve battery activation proceeds via lithium transport to/from the electrochemical aperture, thus inducing physical transformations which permit liquid electrolyte permeation and delivery through the aperture and into the appropriate compartment, thus establishing ionic conduction between the anode and cathode. The accompanying figure highlights the lithium electrochemical aperture (LiECA) in a 3-electrode cell. During the inactive period (a), liquid electrolyte is isolated by the LiECA and stored within the cathode compartment. Electrochemical transport of lithium between the LiECA (b) and cathode induces aperture opening and injecting electrolyte into the anode compartment (c), and ultimately resulting in battery activation and operation. Acknowledgements: Faraday Technology acknowledges the technical assistance of Dr. Joseph P. Fellner at the Air Force Research Laboratory, Wright-Patterson AFB (Dayton, OH) under Air Force Contract No. FA8650-19-P2024 (Phase I SBIR program). Figure 1