A voltage control strategy to improve the cycling stability of organic electrode materials: The case of para-dinitrobenzene

Abstract

Small-molecule organic cathode materials (SMOCMs) with high energy density are promising for various energy storage devices including rechargeable lithium batteries, but it is a huge challenge to simultaneously satisfy the demand of cycling stability. Herein, by taking nitro-based para-dinitrobenzene (pDNB) as an example, we propose a simple but effective voltage control strategy to improve the cycling stability, without energy density decrease or cost increase of the system as for many other complicated solutions. The highly reversible two-electron redox reaction of pDNB provides it full utilization of the theoretical capacity (319 mAh g−1) and high discharge plateau at 2.65 V vs Li+/Li, and thus an outstanding energy density of 850 Wh kg−1. Different voltage windows of 1.8/2.4–3.4/3.8 V are applied to test the cycling performance, and 2.4–3.8 V is selected as the optimized one endowing a high capacity retention of 86 % after 100 cycles (as a contrast, only 8 % within 1.8–3.4 V). Various electrochemical analyses and ex-situ characterization methods reveale that the influence is not in the depth of discharge/charge, but in the dissolution–redepostion behavior of active material and thus the electrode structure evolution. This work provides not only a novel strategy to improve the cycling stability of SMOCMs, but also a new perspective to understand the capacity fading mechanism of them.