Innovative rechargeable carbon-free zinc-air cells

Work Packages 1 and 2 will be developed in parallel. They have an identical general strategy aiming at studying and developing the two main components of the zinc-air cell - the electrodes. The activities will start in m. 6, in the presence of internal standards. Three groupс of carbon free gas diffusion electrode will be developed in and tested: GDE obtained by ceramic technology; composite GDE based on catalyst (Сo3О4; NiCo2O4) and Ni, obtained by chermical reduction and mechanically mixture, cold or/and hot pressed, respectively improved zinc electrodes using several approaches: selecting the ratio of the main components (Zn and ZnO); new additives that inhibit passivation and corrosion; current collector and separator improvements.

The activities will pass throw three optimization cycles of "fabrication - characterization / testing / analysis". After month 18, electrochemical characterization and testing will continue in a full cell configuration in WP4 with the best electrodes.

In Work Package 3 innovative research is organized and/or developed for electrochemical testing of samples prepared in WP 1, WP2. The aim is to develop algorithms that provide reliable information about the degradation mechanisms which determine the cell life cycle, including the cell components. Lifetime of the cell is determined experimentally by the number of charge/discharge cycles. at low-current testing simulating real conditions, testing would be problematic due to the long duration of the experiments. Based on the analysis performed ,acceleration is envisaged in the Work Program by increasing the current densities. The conditions of the accelerated tests should not cause irreversible changes in the system. The activities include: (1) establishment of acceptable experimental conditions under which accelerated testing will not change the state of the system, and (2) preparation of testing protocols for both electrodes (in half cell configuration) and full cell. Experimental verification will be performed with the internal standards.

The assessment of the life time and state of health as well as reliable information on degradation mechanisms using another algorithm, the so called "Differential Resistance Analysis (DRA)" based on the combination of innovative analysis of volt-ampere (i-V) characteristics and impedance analysis at specifically selected working points. The method is developed by IEES and it has been tested on fuel cells. Within the INOVI project it will be approbated on batteries where the measurement conditions for obtaining comparative information have to be considered with the state of charge of the zinc-air system.

The bifunctional catalysts will be investigated at atomic level using neutron scattering techniques. Generally, neutron scattering techniques provide unique information about the structures and dynamics of molecular processes in catalysis, and have connection with many of the most important and up-to-date catalytic systems and processes, including microporous and nano-structured catalysts. Particular attention will be paid on the perovskite structured oxides used firstly in SOFC, as there is no information about their application for reversible zinc-air cells. The relationship between structure and catalytic activity will be used. Comparative analysis of samples will be performed at different stages of charge/discharge, in the beginning and the end of their life.

The studies in Work Package 4 begin in m. 19 and are performed in full cell configuration using the optimized in WP 1 and WP2 electrodes. The aim of this package is to study the degradation processes with two sets of working parameters: (1) cell architecture (Task 4.1) and (2) charge/ discharge rate and discharge depth The research activities include microstructural and electrochemical characterization and focusес on the methods developed in WP3. Two optimization cycles of "design/characterization/ testing/ analysis" will be provided for the best combination of parameters obtained after the first investigation cycle.

In recent years, efforts have been made to merge the area of catalyst characterization with activity/selectivity testing by developing in situ / operando characterization methods that provide both structural and kinetic information for catalysts with hughly developed syrface. This potential opportunity is beyond the tasks of INOVI, but taking into account the interest of the Research Centers, a basis for further activities in this direction can be established.