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Sulfurized polyacrylonitrile (SPAN) is the most promising cathode for next-generation lithium−sulfur (Li−S) batteries due to the much improved stability. However, the molecular structure and reaction mechanism have not yet been fully understood. Herein, we present a new take on the structure and mechanism to interpret the electrochemical behaviors. We find that the thiyl radical is generated after the cleavage of the S−S bond in molecules in the first cycle, and then a conjugative structure can be formed due to electron delocalization of the thiyl radical on the pyridine backbone. The conjugative structure can react with lithium ions through a lithium coupled electron transfer process and form an ion-coordination bond reversibly. This could be the real reason for the superior lithium storage capability, in which the lithium polysulfide may not be formed. This study refreshes current knowledge of SPAN in Li−S batteries. In addition, the structural analysis is applicable to analyze the current organic cathodes in rechargeable batteries and also allows further applications in Al−S batteries to achieve high performance.

Aqueous zinc-ion batteries and capacitors are potentially competitive grid-scale energy storage devices because of their great features such as safety, environmental friendliness, and low cost. Herein, a completely new phenanthroline covalent organic framework (PA-COF) was synthesized and introduced in zinc-ion supercapatteries (ZISs) for the first time. Our as-synthesized PA-COF shows a high capacity of 247 mAh g −1 at a current density of 0.1 A g −1 , with only 0.38% capacity decay per cycle during 10 000 cycles at a current density of 1.0 A g −1 . Although covalent organic frameworks (COFs) are attracting great attention in many fields, our PA-COF has been synthesized using a new strategy involving the condensation reaction of hexaketocyclohexanone and 2,3,7,8-phenazinetetramine. Detailed mechanistic investigations, through experimental and theoretical methods, reveal that the phenanthroline functional groups in PA-COF are the active zinc ion storage sites. Furthermore, we provide evidence for the cointercalation of Zn 2+ (60%) and H + (40%) into PA-COF using inductively coupled plasma atomic emission spectroscopy and deuterium solid-state nuclear magnetic resonance (NMR). We believe that this study opens a new avenue for COF material design for zinc-ion storage in aqueous ZISs.

Covalent organic frameworks (COFs) are potentially promising electrode materials for electrochemical charge storage applications thanks to their pre‐designable reticular chemistry with atomic precision, allowing precise control of pore size, redox‐active functional moieties, and stable covalent frameworks. However, studies on the mechanistic and practical aspects of their zinc‐ion storage behavior are still limited. In this study, a strategy to enhance the electrochemical performance of COF cathodes in zinc‐ion batteries (ZIBs) by introducing the quinone group into 1,4,5,8,9,12‐hexaazatriphenylene‐based COFs is reported. Electrochemical characterization demonstrates that the introduction of the quinone groups in the COF significantly pushes up the Zn2+ storage capability against H+ and elevates the average (dis‐)charge potential in aqueous ZIBs. Computational and experimental analysis further reveals the favorable redox‐active sites that host Zn2+/H+ in COF electrodes and the root cause for the enhanced electrochemical performance. This work demonstrates that molecular engineering of the COF structure is an effective approach to achieve practical charge storage performance.

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Solid electrolyte interphase (SEI)-forming agents such as vinylene carbonate, sulfone, and cyclic sulfate are commonly believed to be film-forming additives in lithium-ion batteries that help to enhance graphite anode stability. However, we find that the film-forming effect and the resultant SEI may not be the only reasons for the enhanced graphite stability. This is because the as-formed SEI cannot inhibit Li + −solvent cointercalation once the additive is removed from the electrolyte. Instead, we show that the Li + solvation structure, which is modified by these additives, plays a critical role in achieving reversible Li + (de)intercalation within graphite. This discovery is confirmed in both carbonate and ether-based electrolytes. We show that the problem of graphite exfoliation caused by Li + −solvent cointercalation can be mitigated by adding ethene sulfate to tune the Li + coordination structure. This work brings new insight into the role of additives in electrolytes, expanding the prevailing thinking over the past 2 decades. In addition, this finding can guide the design of more versatile electrolytes for advanced rechargeable metal-ion batteries.

Most reported carbonaceous anodes of potassium‐ion batteries (PIBs) have limited capacities. One approach to improve the performance of carbon anodes is edge‐nitrogen doping, which effectively enhances the K‐ion adsorption energy. It remains challenging to achieve high edge‐nitrogen doping due to the difficulty in controlling the nitrogen dopant configuration. Herein, a new synthesis strategy is proposed to prepare carbon anodes with ultrahigh edge‐nitrogen doping for high‐performance PIBs. Specifically, self‐assembled supermolecule precursors derived from pyromellitic acid and melamine are directly pyrolyzed. During the pyrolysis process, the amidation and imidization reactions between pyromellitic acid and melamine before carbonization enable the successful carbonization of pyromellitic acid–melamine supermolecule. The obtained 3D nitrogen‐doped turbostratic carbon (3D‐NTC) possesses a 3D framework composed of carbon nanosheets, turbostratic crystalline structure, and an ultrahigh edge‐nitrogen‐doping level up to 16.8 at% (73.7% of total 22.8 at% nitrogen doping). These features endow 3D‐NTCs with remarkable performances as PIB anodes. The 3D‐NTC anode displays a high capacity of 473 mAh g−1, robust rate capability, and a long cycle life of 500 cycles with a high capacity retention of 93.1%. This new strategy will boost the development of carbon anodes for rechargeable alkali‐metal‐ion batteries.

It is a challenge to prepare organic electrodes for sodium-ion batteries with long cycle life and high capacity. The highly reactive radical intermediates generated during the sodiation/desodiation process could be a critical issue because of undesired side reactions. Here we present durable electrodes with a stabilized α-C radical intermediate. Through the resonance effect as well as steric effects, the excessive reactivity of the unpaired electron is successfully suppressed, thus developing an electrode with stable cycling for over 2,000 cycles with 96.8% capacity retention. In addition, the α-radical demonstrates reversible transformation between three states: C=C; α-C·radical; and α-C− anion. Such transformation provides additional Na+ storage equal to more than 0.83 Na+ insertion per α-C radical for the electrodes. The strategy of intermediate radical stabilization could be enlightening in the design of organic electrodes with enhanced cycling life and energy storage capability.