Tailored Zwitterion Electrolyte-Driven Electric Double Layer Dynamics for Enhanced Ion Retention in Artificial Synapses

Electrolyte-gated organic synaptic transistors (EGOSTs) are promising candidates for next-generation neuromorphic devices due to their low-power operation, tunable conductance, and fast response from ion transport. To realize EGOSTs using conventional organic solvent electrolytes, issues such as unstable electric double layer (EDL) formation and rapid depolarization often arise, resulting in poor ion retention and limited non-volatile performance. In contrast, aqueous electrolytes offer high electrochemical stability, an eco-friendly process, and biocompatibility. However, strategies to precisely regulate ion dynamics in aqueous systems remain insufficiently developed. Here, a zwitterion electrolyte design based on electrostatic inter-ion repulsion is proposed to enhance non-volatile characteristics in aqueous systems. By introducing a symmetrical charge-pair structure into the [Li-TFSI] electrolyte, it is demonstrated that ion back-diffusion can be suppressed, and stable EDL formation maintained, as confirmed by electrochemical impedance spectroscopy, cyclic voltammetry, UV–vis absorption, and real-time FT-IR analysis. The fabricated EGOSTs implement stable synaptic characteristics, including enhanced long-term plasticity and potentiation/depression. Furthermore, artificial neural network simulations using a modified National Institute of Standards and Technology (MNIST) handwritten digit dataset demonstrate a recognition accuracy of 94.88%. These findings provide valuable insights into electrolyte design strategies for stable and efficient neuromorphic devices through the control of inter-ion interactions.