Development, Essence, and Application of a Metal-Catalysis Battery

ConspectusIn the pursuit of maximizing the energy supply and sustainable energy development, high-energy-density energy storage systems beyond lithium-ion batteries are surging. The metal-catalysis battery, composed of a metal anode, electrolyte, and redox-coupled electrocatalyst cathode with gas, liquid, or solid as active reactants, is regarded as a promising energy storage and conversion system due to its dual functions of energy storage and chemical production. In this system, with the assistance of a redox-coupled catalyst, during discharging, the reduction potential energy of the metal anode is converted into chemicals along with electrical energy generation, while the external electrical energy is translated to the reduction potential energy of the metal anode and the oxidation potential energy of the reactants during charging. In this loop, the electrical energy and sometimes chemicals can be generated simultaneously. Although intensive effort has been devoted to the exploration of redox-coupled catalysts, the essence of the metal-catalysis battery, which is the prerequisite for further development and application, has been overlooked.In this Account, we present the journey of the metal-catalysis battery from development to essence and application and propose that the metal-catalysis battery system, which combines energy storage and electrocatalytic redox reactions with the characteristics of temporal decoupling and spatial coupling and an energy-conversion paradigm from electrical energy to chemicals via electrochemical energy storage, is achieved. First, inspired by the Zn-air/Li-air battery, we developed and realized Li-CO2/Zn-CO2 batteries and enriched the functions of the metal-catalysis battery from energy storage to chemical production. Based on OER/ORR and OER/CDRR catalysts, we have further explored OER/NO3-RR and HzOR/HER coupled catalysts and developed Zn-nitrate and Zn-hydrazine batteries. By extending the redox-coupled electrocatalyst systems from O, C species to N species and others, the metal-catalysis battery systems would develop from metal-Ox, Cx to metal-Nx and other batteries. Then, from Zn-CO2 and Zn-hydrazine batteries, we found that the overall reaction is decoupled into two separate reduction and oxidation reactions via the cathodic discharge and charge processes, and we further extracted the essence of the metal-catalysis battery, namely, the temporal-decouple and spatial-couple (TD-SC) mechanism, which is completely opposite to the conventional temporal couple and spatial decouple in electrochemical water splitting. Based on the TD-SC mechanism, we developed various applications of metal-catalysis batteries for the green and efficient synthesis of fine chemicals by modifying the metal anode and redox-coupled catalysts and electrolytes, including the Li-N2/H2 battery for NH3 synthesis and the organic Li-N2 battery for fine chemical synthesis. Finally, the main challenges and the possible opportunities for the metal-catalysis battery are discussed, including the rational design of highly efficient redox-coupled electrocatalysts and green electrochemical synthesis. The deep insight into the metal-catalysis battery will provide an alternative approach to energy storage and chemical production.