There are still essential aspects regarding cathodes requiring a comprehensive understanding. These include identifying the underlying phenomena that prevent reaching the theoretical capacity, explaining irreversible losses, and determining the cut-off potentials at which batteries should be cycled. We address these inquiries by investigating the cell’s capacity and phase dynamics by looking into the transport properties of electrons. This approach underlines the crucial role of electrons in influencing battery performance, similar to their significance in other materials and devices such as transistors, thermoelectrics, or superconductors. We use lithium iron phosphate LFP as a case study to demonstrate that understanding the electrochemical cycling behavior of a battery cell, particularly a Li//LFP configuration, hinges on factors like the total local potentials used to calculate chemical potentials, electronic density of states (DOS), and charge carrier densities. Our findings reveal that the stable plateau potential difference is 3.42 V, with maximum charge and minimum discharge potentials at 4.12 V and 2.80 V, respectively. The study illustrates the dynamic formation of metastable phases at a plateau voltage exceeding 3.52 V. Moreover, we establish that determining the working chemical potentials of elements like Li and Al can be achieved by combining their workfunction and DOS analysis. Additionally, we shed light on the role of carbon black beyond conductivity enhancement. Through Density functional theory (DFT) calculations and experimental methods involving scanning Kelvin probe (SKP) and electrochemical analysis, we comprehensively examine various materials, including Li, C, Al, Cu, LFP, FePO₄, Li_0.25FePO₄, polyvinylidene fluoride, and Li₆PS₅Cl. The insights derived from this study, which solely rely on electrical properties, have broad applicability to all cathodes and batteries. They provide valuable information for efficiently selecting optimal formulations and conditions for cycling batteries.

The nickel-rich NMC955 (LiNi0.90Mn0.05Co0.05O2) cathode, with minimal cobalt, is the zenith of LiNixMnyCo1-x-yO2 (NMC) technology but faces structural and thermal stability challenges, losing an average of 15% of its capacity in the first discharge. Here, by selecting appropriate materials and synthesis methods in an all-solid-state battery cell, this challenge is effectively mitigated. A sustainable fabrication of the LiNMC955 positive electrode, excluding poly(vinylidene fluoride) (PVDF) and using styrene-butadiene rubber, demonstrates high retention in all-solid-state cells, without additional interlayers or pressure, at room temperature. To prevent oxygen release, spurious phase formation, and magnetic frustration, simulations determined optimal cycling thresholds and curve morphologies for a Li0/Li6PS5Cl/NMC955 cell by “following the electrons”. This optimized routine ensures prolonged cycle life and performance demonstrated by sheet resistance/Hall effect, Scanning Electron Microscopy/Energy-Dispersive X-ray Spectroscopy (SEM/EDX), Atomic Force Microscopy/Scanning Kelvin Probe Microscopy, Time-of-Flight Secondary Ion Mass Spectrometry, Raman, calorimetry, and electrochemical analyses. The tailored preparation method and cycling regimen enabled the fabrication of a high-performance cathode, achieving capacities exceeding 110-120 mAh.g-1 at C discharging C-rate, after 200 cycles, with a self-recovering component shifting performance to theoretical capacities (192 mAh.g-1), emphasizing the cathode's pivotal role in all-solid-state performance.

Understanding interfacial energetics and transport mechanisms in transition metal oxides is key to unlocking their potential in microelectronics, memory, and energy harvesting and storage. Here, a unified electrochemical potential scale is established for the group IVB oxides TiO ₂ , ZrO ₂ , and HfO ₂ , combining spatially resolved scanning Kelvin probe microscopy with hybrid and density functional theory (DFT) simulations. These results show good agreement between DFT‐predicted absolute chemical potentials and experimental surface potentials across multiple electrode configurations and surface terminations. ZrO ₂ exhibits unexpected emergent behavior under open‐circuit conditions, forming ordered potential patterns suggestive of internal charge separation and O ^δ ⁻ transport. TiO ₂ shows dynamic sensitivity to contact polarity and termination, while HfO ₂ reveals elevated, orientation‐dependent potentials linked to spontaneous ferroelectricity. Complementary temperature‐dependent conductivity and Hall effect measurements expose thermally activated polaronic transport (Fröhlich model), in all three oxides, including sharp transitions and topological conduction thresholds in HfO ₂ . Simulated charge–discharge cycles further demonstrate field‐tunable conductivity and mobility. These findings redefine these oxides as active electrochemical materials, not merely inert dielectrics, and provide a predictive framework for rational interface design in reconfigurable electronics and ion–electron hybrid devices.

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.

The integration of microstructured current collectors offers a potential pathway to enhance interface properties in solid-state battery architectures. In this work, we investigate the influence of surface morphology on the electrochemical performance of Zn/Na_2.99Ba_0.005OCl/Cu electrodeless pouch cells by fabricating copper thin films on microstructured parylene-C substrates using a combination of colloidal lithography and reactive ion etching. O₂ plasma etching times ranging from 0 to 15 min were used to tune the surface topography, resulting in a systematic increase in root-mean-square roughness and a surface area enhancement of up to ~30% for the longest etching duration, measured via AFM. Kelvin probe force microscopy-analyzed surface potential showed maximum differences of 270 mV between non-etched and 12-minute-etched Cu collectors. The results revealed that the chemical potential is the property that relates the surface of the Cu current collector/electrode with the cell’s ionic transport performance, including the bulk ionic conductivity, while four-point sheet resistance measurements confirmed that the copper layers’ resistivity maintained values close to those of bulk copper (1.96–4.5 µΩ.cm), which are in agreement with electronic mobilities (−6 and −18 cm²V⁻¹s⁻¹). Conversely, the charge carrier concentrations (−1.6 to −2.6 × 10²³ cm⁻³) are indirectly correlated with the performance of the cell, with the samples with lower CCC_bulk (fewer free electrons) performing better and showing higher maximum discharge currents, interfacial capacitance, and first-cycle discharge plateau voltage and capacity. The data were further consolidated with Scanning Electron Microscopy and X-ray Photoelectron Spectroscopy analyses. These results highlight that the correlation between the surface morphology and the cell is not straightforward, with the microstructured current collectors’ surface chemical potential and the charge carriers’ concentration being determinant in the performance of all-solid-state electrodeless sodium battery systems.