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

Abstract

Cathode materials are vital to the performance of alkali-ion batteries. Inorganic transitional metal oxides with insertion chemistry, such as LiCoO 2 , LiFePO 4 , and LiNi x Co y Mn 1−x−y O 2 , have been the predominant cathode materials in conventional LIBs. Constructed with heavy metallic elements, conventional inorganic cathode materials typically have restricted specific energy capacity (theoretical: <300 mAh g −1) with little room for further improvements. [1,2] Meanwhile, their applicability in SIBs and KIBs is often hindered due to kinetic and stability issues, where their rigid lattice structures can restrict diffusion/storage of Na + and K + ions of larger sizes than Li +. [7] In addition, produced from minerals with limited availabilities, the use of inorganic cathode materials is neither sustainable nor environmentally benign. In this regard, organic cathode materials have recently attracted increasing attention. Relative to conventional inorganic cathode materials, they show distinct advantages, including higher theoretical capacity due to their construction from abundant light elements, structural diversity with tunable electrochemical properties, rational synthesis from sustainable stocks and low costs. In addition, their less-rigid structures are beneficial for the storage and mobility of larger-sized Na + and K + ions. [8,9] With organic materials, energy storage is achieved through the reversible reaction of alkali ions with their redox-active functional groups. To date, a large family of organic cathode materials incorporating various redox-active functional groups have been developed, which have been well summarized in several recent comprehensive reviews. [10-16] The predominant redoxactive functional groups reported thus far include carbonyl (CO) functionalities, [8,9,17-25] imine (CN) functionalities, [26-29] disulfides (SS), [30-33] radicals, [34-39] and azo (NN), [40-42] with the first two types most heavily focused on. Despite the significant progress, the majority of organic cathode materials developed to date, however, still has restricted specific capacity (generally <300 mAh g −1), energy density (<750 Wh kg −1 for LIBs), and/or cycle life. [10-16] It is thus imperative to explore and discover new redox functionalities that render higher-energy multielectron organic cathode materials with high cyclic stability. We report in this work a new group of nitroaromatic compounds, para-, ortho-, and meta-dinitrobenzene (p-, o-, and m-DNB, respectively) containing dual two-electron accepting nitro groups, as reversible high-energy multielectron organic cathode 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 i...

A nitroaromatic cathode with an ultrahigh energy density based on six-electron reaction per nitro group for lithium batteries

“…Two characteristic nitro stretching bands at 1,495 cm −1 and 1,338 cm −1 are displayed for the pristine electrodes. At the fully discharged state of 2.0 V, those peaks disappear, and a new peak at 1,384 cm −1 appears, indicating the formation of lithiated nitro anions ( 43 ). A reverse change behavior is observed with the reformation of nitro groups upon charging.…”

“…( D ) Performance comparison of 1,5-DNN with reported organic/inorganic electrode materials in terms of energy density, specific capacity and voltage. Cathodes for comparison (references): 1, p -DNB ( 43 ); 2, Li 2 C 6 O 6 ( 49 ); 3, P14AQ ( 50 ); 4, PTO ( 51 ); 5, 3Q ( 31 ); 6, AQ ( 44 ); 7, C 6 O 6 ( 41 ); 8, o -DNB ( 43 ); 9, m -DNB ( 43 ); 10, 4,5-PhenQ ( 51 ); 11, C4Q ( 52 ); 12, LiCoO 2 ( 53 ); 13, LiFePO 4 ( 54 ); 14, NCA ( 55 ); 15, NCM-811 ( 56 ); 16, Li-rich ( 57 ); 17, CF x ( 21 ); 18, MnO 2 ( 58 ); 19 SOCl 2 ( 59 ), 20 SO 2 ( 24 ); 21, S ( 60 ).…”

Hetero-architectured core–shell NiMoO4@Ni9S8/MoS2 nanorods enabling high-performance supercapacitors

“…Arising markets of high-energy density electronics and various electrical cars have prompted the production of efficient, cheap, and environmentally benign energy storage technologies and devices [ 1 ]. Among them, supercapacitors (SCs) have been attracted wide-ranging research interests because of their outstanding energy density, rating performance and superior cycling durability [ 2 ].…”

Organic Negative Electrode Materials for Metal‐Ion and Molecular‐Ion Batteries: Progress and Challenges from a Molecular Engineering Perspective

“…This has enabled building a broad database of electroactive compounds for both positive and negative electrode applications. Organic positive electrode materials (OPEMs) certainly benefit from larger attention since there are more possibilities to explore, for example, conducting polymers, [38,39] nitroxides, and other stable organic radicals, [40][41][42][43] sulfur compounds, [11] as well as conjugated amines, [44][45][46] conjugated sulfonamides, [47] nitro-aromatics, [48] and carbonyls. [49,50] The latter being certainly the most explored category owing to major advances attained so far but also to opportunities for further improvements to attain simultaneously high energy and power densities combined with good cycling stability.…”