Ultrahigh-Areal-Capacity Battery Anodes Enabled by Free-Standing Vanadium Nitride@N-Doped Carbon/Graphene Architecture

Electrochemically Dealloying Engineering toward Integrated Monolithic Electrodes with Superior Electrochemical Li-Storage Properties

Integrated monolithic electrodes (IMEs) free of inactive components demonstrate great potential in boosting energy-power densities and cycling life of lithium-ion batteries. However, their practical applications are significantly limited by low active substance loading (< 4.0 mg cm-2 and 1.0 g cm-3), complicated manufacturing process, and high fabrication cost. Herein, employing industrial Cu-Mn alloy foil as a precursor, a simple neutral salt solution-mediated electrochemical dealloying strategy is proposed to address such problems. The resultant Cu-Mn IMEs achieve not only a significantly larger active material loading due to the in situ generated Cu2O and MnOx (ca. 16.0 mg cm-2 and 1.78 g cm-3), simultaneously fast transport of ions and electrons due to the well-formed nanoporous structure and built-in Cu current collector, but also high structural stability due to the interconnected ligaments and suitable free space to relieve the volume expansion upon lithiation. As a result, they demonstrate remarkable performances including large specific capacities (> 5.7 mAh cm-2), remarkable pseudocapacitive effect despite the battery-type constitutes, long cycling life, and good working condition in a lithium-ion full cell. This study sheds new light on the further development of IMEs, enriches the existing dealloying techniques, and builds a bridge between the two.

Synthesis and Characterization of Vanadium Nitride/Carbon Nanocomposites

The present work focuses on the synthesis of a vanadium nitride (VN)/carbon nanocomposite material via the thermal decomposition of vanadyl phthalocyanine (VOPC). The morphology and chemical structure of the synthesized compounds were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), Fourier transformed infrared spectroscopy (FTIR), X-ray diffraction (XRD), and X-ray photoemission spectroscopy (XPS). The successful syntheses of the VOPC and non-metalated phthalocyanine (H2PC) precursors were confirmed using FTIR and XRD. The VN particles present a needle-like morphology in the VN synthesized by the sol-gel method. The morphology of the VN/C composite material exhibited small clusters of VN particles. The XRD analysis of the thermally decomposed VOPC indicated a mixture of amorphous carbon and VN nanoparticles (VN(TD)) with a cubic structure in the space group FM-3M consistent with that of VN. The XPS results confirmed the presence of V(III)-N bonds in the resultant material, indicating the formation of a VN/C nanocomposite. The VN/C nanocomposite synthesized through thermal decomposition exhibited a high carbon content and a cluster-like distribution of VN particles. The VN/C nanocomposite was used as an anode material in LIBs, which delivered a specific capacity of 307 mAh g-1 after 100 cycles and an excellent Coulombic efficiency of 99.8 at the 100th cycle.

Indium Nitride Nanowires: Low Redox Potential Anodes for Lithium-Ion Batteries

Advanced lithium-ion batteries (LIBs) are crucial to portable devices and electric vehicles. However, it is still challenging to further develop the current anodic materials such as graphite due to the intrinsic limited capacity and sluggish Li-ion diffusion. Indium nitride (InN), which is a new type of anodic material with low redox potential (<0.7 V vs Li/Li+) and narrow bandgap (0.69 eV), may serve as a new high-energy density anode material for LIBs. Here, the growth of 1D single crystalline InN nanowires is reported on Au-decorated carbon fibers (InN/Au-CFs) via chemical vapor deposition, possessing a high aspect ratio of 400. The binder-free Au-CFs with high conductivity can provide abundant sites and enhance binding force for the dense growth of InN nanowires, displaying shortened Li ion diffusion paths, high structural stability, and fast Li+ kinetics. The InN/Au-CFs can offer stable and high-rate Li delithiation/lithiation without Li deposition, and achieve a remarkable capacity of 632.5 mAh g-1 at 0.1 A g-1 after 450 cycles and 416 mAh g-1 at a high rate of 30 A g-1. The InN nanowires as battery anodes shall hold substantial promise for fulfilling superior long-term cycling performance and high-rate capability for advanced LIBs.

Polyaniline-Coated Porous Vanadium Nitride Microrods for Enhanced Performance of a Lithium-Sulfur Battery

To solve the slow kinetics of polysulfide conversion reaction in Li-S battery, many transition metal nitrides were developed for sulfur hosts. Herein, novel polyaniline-coated porous vanadium nitride (VN) microrods were synthesized via a calcination, washing and polyaniline-coating process, which served as sulfur host for Li-S battery exhibited high electrochemical performance. The porous VN microrods with high specific surface area provided enough interspace to overcome the volume change of the cathode. The outer layer of polyaniline as a conductive shell enhanced the cathode conductivity, effectively blocked the shuttle effect of polysulfides, thus improving the cycling capacity of Li-S battery. The cathode exhibited an initial capacity of 1007 mAh g^-1 at 0.5 A g^-1, and the reversible capacity remained at 735 mAh g^-1 over 150 cycles.

High-performance Zn-ion batteries constructed by in situ conversion of surface-oxidized vanadium nitride into Zn3(OH)2V2O7·2H2O with oxygen defects

Surface-oxidized vanadium nitride transforms into Zn3V2O7(OH)2-based materials with oxygen defects by electrochemical conversion, which act as cathodes for high performance aqueous zinc ion batteries.

A free-standing VN/MXene composite anode for high-performance Li-ion hybrid capacitors

The Li-ion hybrid capacitor (LIHC) is considered as a promising candidate for electrochemical energy storage owing to the high energy and power density. However, the sluggish anodic reaction kinetics and high reaction voltage greatly hinder the overall performance of LIHCs. Herein, a free-standing VN/MXene composite anode with high specific capacity and low reaction voltage was prepared by a simple vacuum filtration method. The obtained VN/MXene composite anode shows a high discharge specific capacity of 501.7 mA h g⁻¹ at 0.1 A g⁻¹ and excellent rate capability (191.8 mA h g⁻¹ at 5 A g⁻¹), as well as much extended cycling stability (1500 cycles at 2 A g⁻¹). When combined with an egg white-derived activated carbon (E-AC) cathode, the assembled LIHC delivers a high specific capacity of 59.1 F g⁻¹ and a high energy density of 129.3 W h kg⁻¹ with a power density of 449.7 W kg⁻¹. Even at a high current density of 5 A g⁻¹, the LIHC still maintains an exciting energy density of 42.81 W h kg⁻¹ at 11 249 W kg⁻¹. Meanwhile, the cycling life can be extended to 5000 cycles with a high capacity retention of 98% at 1 A g⁻¹. We believe that this work opens up new possibilities for developing advanced free-standing MXene-based electrodes for Li-ion storage.

The Li-ion hybrid capacitor (LIHC) is considered as a promising candidate for electrochemical energy storage owing to the high energy and power density.