Molecular engineering of carbonyl organic electrodes for rechargeable metal-ion batteries: fundamentals, recent advances, and challenges

Organic carbonyl compounds have achieved great success as prospective electrodes for rechargeable metal-ion batteries for the replacement of commercial inorganic electrodes, since the extensive chemistry of organics allows to vary the structure in an eco-friendly manner to tune electrochemical properties. However, the ease of dissolution in electrolyte, intrinsically poor electronic conductivity, and low volumetric energy density greatly restrict their long-term cyclability and rate capability, impeding their widespread usage, especially for practical battery systems. Considering this, a great number of molecular engineering strategies have been proposed to overcome the above obstacles. In this review, we have summarized several commonly used molecular engineering approaches to reinforce the electrochemical performance of carbonyl organic compounds and simultaneously generalized the advantages and disadvantages of each strategy. Some recent key investigations on the reaction mechanism of carbonyl organic electrodes by using operando and ex situ techniques as well as theoretical calculations have also been highlighted. More importantly, different from most of the previous reviews focused on materials design, some critical challenges and future perspectives of carbonyl organic electrodes for practical battery systems have been evaluated in more depth. Therefore, this review will offer fundamental and useful guidance not only for the rational design of carbonyl electrodes but also for practical carbonyl-based battery systems applicable in the foreseeable future.