The main goal of the CARiM project is to advance an entirely new concept for triggering a synergism between cationic and anionic redox reactions in layered oxides and MOFs with an aim to reach a colossal intercalation capacity. The dual redox reaction of the cation and anion breaks the paradigm of the intercalation materials for limited number of intercalated ions: instead of the charges of guest intercalated ions to be compensated by the change in the oxidation state of transition metal cations of the host material, the boosting of the anion redox activity enables an extra amount of guest ions to be intercalated. The proof-of-concept is built on the development of experimental and theoretical approaches for surface and structural engineering of oxide materials and metal-organic frameworks. The tight interrelation between the knowledge on the redox reactions of cations and anions and their importance for a plethora of research areas defines the potential of the CARiM project to go beyond the state-of-the-art. In general, the novelty of the project to introduce a unified concept for materials with colossal intercalation capacity has a huge potential to make a breakthrough in the solid state chemistry and physics with an impact far beyond the scientific community.
- Objective 1: To activate redox activity of oxygen in layered oxides through structural engineering. The structural engineering relies on two approaches: (i) the first is focused on the substitution of transition metal ions from the host material with “intercalated” inactive ions; (ii) the second is directed towards the creation of metal vacancies in the transition metal layers. The consistent using of both approaches will also impact the cationic distribution of TM ions inside the layers. All these structural aspects will allow modifying the energy position of oxygen states within the band structure of the host material, thus resulting in triggering the oxygen redox activity.
- Objective 2: To stabilize the redox activity of oxygen by avoiding its surface side reactions. To suppress the surface reactivity, a pioneering concept will be exploited in the CARiM project. The concept consists in surface coating of intercalation oxides with “oxygen-storage” materials. The concept of surface modification has been elaborated by us in respect of protecting the oxide electrodes from aggressive nonaqueous electrolyte in lithium ion batteries. In the CARiM project, the role of oxygen-storage materials is to provide oxygen as a shuttle between two components: the oxygen-storage material will accumulate the oxygen released during the complete alkali ion extraction from the intercalation oxide, and, during the reverse reaction, the oxygen from the oxygen storage material will be transferred to the intercalation oxide.
- Objective 3: To predict and validate a new class of intercalation materials with colossal intercalation capacity. Metal oxides with ionic bonding are not the only systems offering a combination of transition metals and oxygen. Another type of bonding also allows the exploitation of the reversible redox scheme for the massive intercalation of alkaline metals, namely, covalent and coordination bonding in materials combining the attractive properties of transition metals with the redox properties of conjugated organic ligands-linkers for the construction of metal-organic frameworks (MOFs) with tuneable structural and electrochemical parameters. In addition, these systems are light-weight and low-cost. Extensive molecular modelling will be undertaken to design different MOF architectures and the most promising models will be synthesized and tested experimentally for intercalation capacity.
- Objective 4: To elaborate a new concept for materials with colossal intercalation capacity. This is the core of the CARiM project. The unification of in-depth physicochemical, electrochemical and theoretical investigations will bring about new principles that dominate the redox activity of cations and anions. On the other hand, the formulation of new relationships in the complete knowledge-chain “synthesis-structure-intercalation” will pave the road to discovering unprecedented properties of materials.