High-voltage and High-capacity Organic Cathodes for Zinc Ion Batteries through Structure Regulation and Electrolyte Modification

Description

The generation and supply of sustainable energy are the main tasks facing humanity in the twenty-first century. To a certain extent, the current commercial success of lithium-ion batteries (LIBs) satisfies the energy demand, but the flammability of the organic electrolytes has led to a recurrence of safety concerns including fires and explosions. Aqueous zinc-ion batteries (AZIBs) efficiently minimize safety risks by using inexpensive, non-combustible water as the electrolyte in place of flammable organic electrolytes. Finding appropriate cathode materials, however, is a critical issue that must be resolved. Due to their low toxicity, high theoretical capacity, predictable synthesis, good structural variety, and affordability, organic materials (OMs) are suitable cathode materials for AZIBs and adhere to the idea of environmental sustainability. However, high potential organic electrodes are uncommon, and the majority of reported organic cathode based AZIBs have voltages of less than 1.2 V. Therefore, the low output voltage and poor specific energy density of OMs-based AZIBs are their main drawbacks. The development of widely used OMs-based AZIBs is dependent on the synergistic improvement of the voltage and capacity, according to the energy equation E=QV. For p-type OMs, the energy change of the reaction process can be split into two-step reactions according to the reaction scheme. The first step is the removal of electrons from the p-conjugated structure through the oxidation of p-type organics. Step 2: Anions from the electrolyte balance the positive charge still on the organics. Cathode potential is inversely proportional to the Gibbs free energy (cathode potential=-DG/nF). The secret to improving energy is controlling the energy shift at each stage to improve the voltage of OMs.  In this project, we suggest adding electron-withdrawing groups to OMs to reduce their electron loss energy and investigate the connection between OM structure and the electrochemical performance to create high-voltage, high-capacity organic cathodes for AZIBs. Surfactants will also be added to the electrolyte from the standpoint of electrolyte control to boost the de-solvation energy and widen the water decomposition window, which will enhance battery cycle stability. To create high-performance OMs, we will also investigate the physical/chemical immobilization of high-capacity OMs using high-voltage halogens (Br2). In addition, machine learning will be used for the high-throughput screening of high-performance OMs, paving the way for the development of high-performance OMs.