Nitroaromatics as High-Energy Organic Cathode Materials for Rechargeable Alkali-Ion (Li~+, Na~+, and K~+) Batteries

摘要

Organic cathode materials with existing redox functionalities are attracting increasing attention for rechargeable alkali-ion batteries due to their high theoretical gravimetric capacity, molecular diversity, and sustainability. However, they are still restricted in specific capacity and energy density. The discovery of new multielectron redox-active functionalities that can impart significantly enhanced capacity and energy density is highly desired. Herein, a group of organic nitroaromatic compounds (p-, o-, and m-dinitrobenzene (DNB)) is reported as novel high-energy cathode materials for alkali-ion batteries. For the first time, nitro groups in DNBs are found to undergo an electrochemically reversible two-step two-phase reaction at a voltage above 2 V, rendering a high theoretical capacity of 638 mAh g(-1). A systematic study is undertaken to reveal the reaction mechanism and verify the redox reversibility. By confining the optimum p-DNB within a microporous carbon nanosphere host, record-high reversible capacities of 620, 573, and 536 mAh g(-1) at 50 mA g(-1) are achieved for lithium-, sodium-, and potassium-ion batteries, respectively. Demonstrating nitro as a unique redox-reversible functionality, this work opens a new direction in the development of novel high-performance organic nitroaromatic cathode materials for next-generation alkali-ion batteries.