Organic cathode materials are attractive for rechargeable lithium-ion batteries due to their advantages in sustainability and designability of molecular structure as well as the high upper limit of theoretical capacity....

The magnetic properties of CoZr magnetic thin films with stripe domains are investigated. The nanocrystalline grain size of 21.2 nm of CoZr thin film was obtained by x-ray diffraction spectra. The rotatable stripe-domain structure of the samples can be clearly observed from the magnetic force microscopy images. From the results of the M-H loop, the typical loops with domain structure of the samples can also be seen. The saturation magnetic fields of the thin films increase as a function of stripe half period in static magnetic properties. In dynamic magnetic properties, we find two precession modes, which include one traditional uniform precession mode with the resonance peak position in the low-frequency band and the other as the non-uniform precession mode with the resonance peak position in the high-frequency band. The ferromagnetic resonance frequencies of the non-uniform procession mode, which are driven by the exchange coupling between adjacent domains, show a decrease in behavior from 5.11to 3.52 GHz in the zero-field dynamic permeability spectra with the stripe domain's half period increasing, while the ferromagnetic resonance frequencies of the uniform procession mode nearly remain constant. Similar behavior of exchange coupling can be found by analyzing the field-dependent dynamic permeability spectra of CoZr films, which indicates that the main contribution of the thickness-dependent resonance frequency is the exchange coupling between neighboring stripe domains.

Benefiting from the proton's small size and ultrahigh mobility in water, aqueous proton batteries are regarded as an attractive candidate for high‐power and ultralow‐temperature energy storage devices. Herein, a new‐type C4N polymer with uniform micropores and a large specific surface area is prepared by sulfuric acid‐catalyzed ketone amine condensation reaction and employed as the electrode of proton batteries. Multi‐walled carbon nanotubes (MWCNT) are introduced to induce the in situ growth of C4N, and reaped significantly enhanced porosity and conductivity, and thus better both room‐ and low‐temperature performance. When coupled with MnO2@Carbon fiber (MnO2@CF) cathode, MnO2@CF//C4N‐50% MWCNT full battery shows unprecedented cycle stability with a capacity retention of 98% after 11 000 cycles at 10 A g−1 and even 100% after 70 000 cycles at 20 A g−1. Additionally, a novel anti‐freezing electrolyte (5 m H2SO4 + 0.5 m MnSO4) is developed and showed a high ionic conductivity of 123.2 mS cm−1 at ‐70 °C. The resultant MnO2@CF//C4N‐50% MWCNT battery delivers a specific capacity of 110.5 mAh g−1 even at ‐70 °C at 1 A g−1, the highest in all reported proton batteries under the same conditions. This work is expected to offer a package solution for constructing high‐performance ultralow‐temperature aqueous proton batteries.

Despite their high specific capacity and low cost, small-molecule organic cathodes usually suffer from fast capacity decay due to the unavoidable dissolution in the electrolytes, which largely impede their practical...

Recently, carbon nitrides and their carbon-based derivatives have been widely studied as anode materials of lithium-ion batteries due to their graphite-like structure and abundant nitrogen active sites. In this paper, a layered carbon nitride material C3N3 consisting of triazine rings with an ultrahigh theoretical specific capacity was designed and synthesized by an innovative method based on Fe powder-catalyzed carbon–carbon coupling polymerization of cyanuric chloride at 260 °C, with reference to the Ullmann reaction. The structural characterizations indicated that the as-synthesized material had a C/N ratio close to 1:1 and a layered structure and only contained one type of nitrogen, suggesting the successful synthesis of C3N3. When used as a lithium-ion battery anode, the C3N3 material showed a high reversible specific capacity up to 842.39 mAh g–1 at 0.1 A g–1, good rate capability, and excellent cycling stability attributed to abundant pyridine nitrogen active sites, large specific surface area, and good structure stability. Ex situ XPS results indicated that Li+ storage relies on the reversible transformation of −C=N– and −C–N– groups as well as the formation of bridge-connected −C=C– bonds. To further optimize the performance, the reaction temperature was further increased to synthesize a series of C3N3 derivatives for the enhanced specific surface area and conductivity. The resulting derivative prepared at 550 °C showed the best electrochemical performance, with an initial specific capacity close to 900 mAh g–1 at 0.1 A g–1 and good cycling stability (94.3% capacity retention after 500 cycles at 1 A g–1). This work will undoubtedly inspire the further study of high-capacity carbon nitride-based electrode materials for energy storage.