Ferroelectric materials are poised to drive the next technological leap through their emergent functionalities, including negative capacitance and resistance, charge accumulation without transport, and spontaneous polarization switching. The discovery of ferroionic material-systems that combine room-temperature ferroelectricity and fast ionic conductivity has opened an unprecedented avenue for multifunctional devices that merge the territories of electronics and ionics. These hybrid materials enable the direct coupling of ionic and electronic order parameters, allowing long-range electrostatic interactions, wireless field communication, and energy transduction across solid–solid and solid–air interfaces. Such capabilities offer potential solutions to long-standing challenges, including the Boltzmann limit in transistor subthreshold operation, voltage amplification without power dissipation, and nonvolatile polarization states with ionic reconfigurability. Beyond conventional applications, ferroionics support a new generation of quantum sensors and adaptive devices, spanning optical, electrical, mechanical, thermal, and magnetic domains. This review provides a comprehensive overview of the conceptual foundations, theoretical frameworks, and experimental progress underlying ferroionic systems, highlighting their role as a bridge between ferroelectrics, solid electrolytes, and correlated quantum materials. Finally, perspectives are offered on how ferroionic coupling may reshape device physics and enable sustainable, self-powered information and energy technologies.

This study investigates all-solid-state batteries employing multifunctional metallic current collectors/electrodes that remain electrochemically inert toward an alkali-based Na ion solid electrolyte. Inconel 625 was evaluated as the positive current collector in combination with aluminum as the negative electrode and the ferroelectric electrolyte Na2.99Ba0.005OCl. The inertness of both electrodes enabled the construction of a robust device architecture that behaved as a true battery, exhibiting a two-phase equilibrium discharge plateau at ~1.1 V despite the absence of traditional Faradaic reactions. After a one-month rest period, the cell was sequentially discharged through external resistors and retained full functionality for one year. Cyclic voltammetry confirmed a stable electrochemical response over repeated cycling. The final long-term discharge under a 9.47 kΩ load produced a steady ~0.92 V plateau and delivered a total capacity of 35 mAh (~2.3 mAh·cm⁻²). Post-mortem analyses revealed excellent chemical and mechanical stability of Inconel 625 after extended operation, while aluminum showed superficial surface degradation attributed to residual moisture, with X-ray diffraction indicating the formation of aluminum hydroxide. Scanning Kelvin probe measurements guided electrode selection and provided insight into interfacial energetics, whereas scanning electron microscopy confirmed interface integrity. Complementary density functional theory simulations optimized the crystalline bulk and surfaces of Inconel, demonstrating interfacial stability at the atomic scale. Overall, this work elucidates the fundamental driving forces underlying traditional battery operation by studying a “capacity-less” system, highlighting the central role of interfacial electrostatics in sustaining battery-like discharge behavior in the absence of redox-active electrodes.

Controlling electrostatic potential landscapes at the mesoscale is essential for the advancement of adaptive electronic systems. In edge‐gated electrostatic geometries based on ferroionic Li _2.99 B _a0.005 OCl films, directional spillover fields and polaron pinning effects generate structured, air‐side electrostatic gradients across centimeter‐scale gaps. A combination of piezoresponse force microscopy (PFM), micrometer‐resolution scanning Kelvin probe (µm‐SKP) analysis, electrochemical impedance spectroscopy (EIS), and temperature‐dependent transport measurements, supported by numerical solutions of the Poisson–Nernst–Planck (PNP) equations, shows dynamic coupling between surface polarization and mobile charge carriers. Apparent surface mobilities in the range of 300–500 cm ² V ⁻¹ s ⁻¹ are observed under non‐equilibrium polarization conditions, accompanied by negative static resistance (NSR) and field‐induced carrier asymmetry. These results point to topologically guided conduction paths constrained by interface geometry and electrostatic boundary conditions. Such phenomena enable programmable capacitance zoning and field shaping, with implications for the design of solid‐state transistors and batteries, neuromorphic elements, energy harvesters, and high‐sensitivity sensing platforms.