Poly(benzoquinonyldisulfide) as organic positve electrode for Mg and Li batteries

Long Cycle Life for Rechargeable Lithium Battery using Organic Small Molecule Dihydrodibenzo[c,h][2,6]naphthyridine-5,11-dione as a Cathode after Isoindigo Pigment Isomerization

Sustainability and adaptability in structural design of the organic cathodes present promises for applications in alkali metal ion batteries. Nevertheless, a formidable challenge lies in their high solubility in organic electrolytes, particularly for small molecular materials, impeding cycling stability and high capacity. This study focuses on the design and synthesis of organic small molecules, the isomers of (E)-5,5'-difluoro-[3,3'-biindolinylidene]-2,2'-dione (EFID) and 3,9-difluoro-6,12-dihydrodibenzo [c, h][2,6]naphthyridine-5,11-dione (FBND). While EFID, characterized by a less π-conjugated structure, exhibits subpar cycling stability in lithium-ion batteries (LIBs), intriguingly, another isomer, FBND, demonstrates exceptional capacity and cycling stability in LIBs. FBND delivers a remarkable capacity of 175 mAh g-1 at a current density of 0.05 A g-1 and maintains excellent cycling stability over 2000 cycles, retaining 90% of its initial capacity. Furthermore, an in-depth examination of redox reactions and storage mechanisms of FBND are conducted. The potential of FBND is also explored as an anode in lithium-ion batteries (LIBs) and as a cathode in sodium-ion batteries (SIBs). The FBND framework, featuring extended π-conjugated molecules with an imide structure compared to EFID, proves to be an excellent material template to develop advanced organic small molecular cathode materials for sustainable batteries.

Storing Mg Ions in Polymers: A Perspective

The electrochemical performance of rechargeable Mg batteries (RMBs) is primarily determined by the cathodes. However, the strong interaction between highly polarized Mg²⁺ and the host lattice is a big challenge for inorganic cathode materials. While endowed with weak interaction with Mg²⁺ , organic polymers are capable of fast reaction kinetics. Besides, with the advantages of light weight, abundance, low cost, and recyclability, polymers are deemed as ideal cathode materials for RMBs. Although polymer cathodes have remarkably progressed in recent years, there are still significant challenges to overcome before reaching practical application. In this perspective, the challenges faced by polymer cathodes are critically focused, followed by the retrospection of efforts devoted to design polymers. Some feasible strategies are proposed to explore new structures and chemistries for the practical application of polymer cathodes in RMBs.

Current Design Strategies for Rechargeable Magnesium-Based Batteries

As a next-generation electrochemical energy storage technology, rechargeable magnesium (Mg)-based batteries have attracted wide attention because they possess a high volumetric energy density, low safety concern, and abundant sources in the earth's crust. While a few reviews have summarized and discussed the advances in both cathode and anode materials, a comprehensive and profound review focusing on the material design strategies that are both representative of and peculiar to the performance improvement of rechargeable Mg-based batteries is rare. In this mini-review, all nine of the material design strategies and approaches to improve Mg-ion storage properties of cathode materials have been comprehensively examined from both internal and external aspects. Material design concepts are especially highlighted, focusing on designing "soft" anion-based materials, intercalating solvated or complex ions, expanding the interlayer of layered cathode materials, doping heteroatoms into crystal lattice, size tailoring, designing metastable-phase materials, and developing organic materials. To achieve a better anode, strategies based on the artificial interlayer design, efficient electrolyte screening, and alternative anodes exploration are also accumulated and analyzed. The strategy advances toward Mg-S and Mg-Se batteries are summarized. The advantages and disadvantages of all-collected material design strategies and approaches are critically discussed from practical application perspectives. This mini-review is expected to provide a clear research clue on how to rationally improve the reliability and feasibility of rechargeable Mg-based batteries and give some insights for the future research of Mg-based batteries as well as other multivalent-ion battery chemistries.