SSI-21 is meant to provide an opportunity to discuss all of the areas of Solid State Ionics. For the sake of classification the Symposia, which cover both the fundamental and the applied aspects of Solid State Ionics, are grouped into a few Macro-Areas depending on the practical application of the results.

Nevertheless, all those contributions to SSI-21 that do not find home in any of the Symposia are also welcome and appreciated. If there is any difficulty in hosting your contribution in one of the suggested Symposia/Macro-Areas, please contact directly the Conference Chairmen at ssi21@dii.unipd.it to receive advice on the best accommodation for your contribution.

Macro-Area 1: Ionics in Energy and Environment
These symposia will be focused on the research on solid-state ionic materials (e.g., SEs - solid electrolytes; MIECs - mixed-ionic electronic conductors and electrodes) for energy conversion and storage systems and performance of the corresponding devices, such as fuel cells and electrolyzers (operating both at low and at high temperatures), redox flow batteries, primary and secondary batteries, supercapacitors and ultracapacitors, photovoltaic devices, apparatuses for thermochemical energy storage and water/CO₂ splitting. Research aimed at methods of characterization of materials, devices and processes as well as at the development of sensors will also be included in this macro-area.

Macro-Area 2: Ionics in Communication and Robotics
These symposia will cover all the different aspects of ionics science and technology aimed at the development of advanced materials and systems for application in the ICT (information and communication technology) field, including memristors, switches, conductors, and microelectronic components. This macro-area also covers the applications of ionics science and technology in robotics (e.g., for the development of actuators and other related devices).

Macro-Area 3: Ionics in Biological systems and Life sciences
These symposia will explore the impact of ionics in biological systems, covering areas such as ion transport through membranes, the detection and transduction of stimuli, and the interfacing between biological and artificial systems. This includes also the mimicking of biological operations by electrical circuits including MIECs.

Macro-Area 4: General Aspects, Fundamentals and Theory in ion-conducting materials
SSI-21 will also welcome and emphasize fundamental contributions on several research areas:

• “Cross-effect” phenomena. Some examples include instances where an external stimulus (e.g., a mechanical stress, exposure to light or other radiation) influences the ion-transport mechanism;
• Mesoscale phenomena. A typical case consists in a system where the presence of different domains at the mesoscopic scale strongly affects the macroscopic properties.
• High-field effects. Typical examples include nonlinear optic materials.
• Implementation of advanced characterization techniques.
• Computational modeling and simulations.
• Various topics. Topics relevant to solid state ionics and not included above.