Searching for novel solid electrolytes is of great importance and challenge for all-solid-state Mg batteries. In this work, we develop an amorphous Mg borohydride ammoniate, Mg(BH₄)₂·2NH₃, as a solid Mg electrolyte that prepared by a NH₃ redistribution between 3D framework-γ-Mg(BH₄)₂ and Mg(BH₄)₂·6NH₃. Amorphous Mg(BH₄)₂·2NH₃ exhibits a high Mg-ion conductivity of 5 × 10⁻⁴ S cm⁻¹ at 75 ℃, which is attributed to the fast migration of abundant Mg vacancies according to the theoretical calculations. Moreover, amorphous Mg(BH₄)₂·2NH₃ shows an apparent electrochemical stability window of 0–1.4 V with the help of in-situ formed interphases, which can prevent further side reactions without hindering the Mg-ion transfer. Based on the above superiorities, amorphous Mg(BH₄)₂·2NH₃ enables the stable cycling of all-solid-state Mg cells, as the critical current density reaches 3.2 mA cm⁻² for Mg symmetrical cells and the reversible specific capacity reaches 141 mAh g⁻¹ with a coulombic efficiency of 91.7% (first cycle) for Mg||TiS₂ cells.

In recent years, tremendous research interest has been triggered in the fields of flexible, wearable and miniaturized power supply devices and self-powered energy sources, in which energy harvesting/conversion devices are integrated with energy storage devices into an infinitely self-powered energy system. As opposed to conventional fabrication methods, printing techniques hold promising potency for fabrication of power supply devices with practical scalability and versatility, especially for applications in wearable and portable electronics. To further enhance the performance of the as-fabricated devices, the utilization of nanomaterials is one of the promising strategies, owing to their unique properties. In this review, an overview on the progress of printable strategies to revolutionize the fabrication of power supply devices and integrated system with attractive form factors is provided. The advantages and limitations of the commonly adopted printing techniques for power supply device fabrication are first summarized. Thereafter, the research progress on novel developed printable energy harvesting and conversion devices, including solar cells, nanogenerators and biofuel cells, and the research advances on printable energy storage devices, namely, supercapacitors and rechargeable batteries, are presented, respectively. Although exciting advances on printable material modification, innovative fabrication methods and device performance improvement have been witnessed, there are still several challenges to be addressed to realize fully printable fabrication of integrated self-powered energy sources.