Ammonium vanadate with bronze structure (NH₄V₄O₁₀) is a promising cathode material for zinc-ion batteries due to its high specific capacity and low cost. However, the extraction of $${\text{NH}}_{{4}}^{ + }$$NH 4 + at a high voltage during charge/discharge processes leads to irreversible reaction and structure degradation. In this work, partial $${\text{NH}}_{{4}}^{ + }$$NH 4 + ions were pre-removed from NH₄V₄O₁₀ through heat treatment; NH₄V₄O₁₀ nanosheets were directly grown on carbon cloth through hydrothermal method. Deficient NH₄V₄O₁₀ (denoted as NVO), with enlarged interlayer spacing, facilitated fast zinc ions transport and high storage capacity and ensured the highly reversible electrochemical reaction and the good stability of layered structure. The NVO nanosheets delivered a high specific capacity of 457 mAh g⁻¹ at a current density of 100 mA g⁻¹ and a capacity retention of 81% over 1000 cycles at 2 A g⁻¹. The initial Coulombic efficiency of NVO could reach up to 97% compared to 85% of NH₄V₄O₁₀ and maintain almost 100% during cycling, indicating the high reaction reversibility in NVO electrode.

Piezoelectric nanogenerators (PENGs) that can harvest mechanical energy from ambient environment have broad prospects for multi-functional applications. Here, multi-layered piezoelectric composites with a porous structure based on highly oriented Pb(Zr_0.52Ti_0.48)O₃/PVDF (PZT/PVDF) electrospinning fibers are prepared via a laminating method to construct high-performance PENGs. PZT particles as piezoelectric reinforcing phases are embedded in PVDF fibers and facilitate the formation of polar β phase in PVDF. The multi-layered, porous structure effectively promotes the overall polarization and surface bound charge density, resulting in a highly efficient electromechanical conversion. The PENG based on 10 wt% PZT/PVDF composite fibers with a 220 µm film thickness outputs an optimal voltage of 62.0 V and a power of 136.9 µW, which are 3.4 and 6.5 times those of 10 wt% PZT/PVDF casting film-based PENG, respectively. Importantly, the PENG shows a high sensitivity of 12.4 V·N⁻¹, presenting a significant advantage in comparison to PENGs with other porous structures. In addition, the composites show excellent flexibility with a Young’s modulus of 227.2 MPa and an elongation of 262.3%. This study shows a great potential application of piezoelectric fiber composites in flexible energy harvesting devices.