ABSTRACT
Zn anodes of aqueous Zn metal batteries face challenges from dendrite growth and side reactions. Building Zn(002) texture mitigates the issues but does not eradicate them. Zn(002) still faces severe challenges from corrosive electrolytes and dendrite growth, especially after hundreds of cycles. Therefore, it is necessary to have a passivation layer covering Zn(002). Here, Zn(002) texture and surface coating are achieved on Zn foils by an one-step annealing process, as demonstrated by ZnS, ZnSe, ZnF2, Zn3(PO4)2 (ZPO), etc. Using ZPO as a model, the coupling between surface coating and Zn(002) is illustrated in terms of dendrite-suppressing ability and diffusion energy barrier of Zn2+. The modified Zn foils (Zn(002)@ZPO) exhibit the excellent electrochemical performance, far superior to Zn(002) or ZPO alone. In the full cells, the performance is greatly improved even under harsh conditions, i.e., high areal capacity and limited Zn resource. This work achieves crystal engineering and surface coating on Zn anodes simultaneously and discloses the in-depth insights about the synergy of crystal orientation and passivation layers.
ABSTRACT
Increasing the crystal resistivity is critically important for enhancing the signal-to-noise ratio and improving the sensing capability of high-temperature piezoelectric sensors based on langasite-type crystals. The resistivity of structural ordered langasite-type crystals is much higher compared to that of the disordered crystals. Here, we selected structural ordered Ca3TaGa3Si2O14 (CTGS) and disordered La3Ga5SiO14 (LGS) as representatives to investigate the microscopic conduction mechanism and further reveal the origin of the different resistivities of the ordered and disordered langasite-type crystals at elevated temperatures. By combining first-principles calculations and experimental investigations, we found that the different conductivity behaviors of the ordered and disordered crystals originate from different types of point defects formed in the crystal and their different contributions to the conductivity. For the disordered LGS crystal, the oxygen vacancies are apt to be formed at high temperatures, promoting the transition of valence electrons and yielding high conductivity. For the ordered CTGS crystal, the dominant TaGa antisite defects can introduce an electron-hole recombination center in the electronic band gap, significantly shortening the carrier lifetime and thus reducing the conductivity. This provides effective guidance to improve the resistivity performance of langasite-type crystals at high temperatures by optimizing the experimental conditions, such as oxygen atmosphere treatment, antisite defect modification, etc.
ABSTRACT
Disordered crystals have attracted immense attention for the generation of ultrashort laser pulses due to their good thermomechanical characteristics and wide emission bandwidths. In this work, a Gd-based orthophosphate crystal, GdSr3(PO4)3, (GSP), and a Nd3+-doped GdSr3(PO4)3 crystal, (Nd:GSP), were obtained by the Czochralski method. The crystal structure, optical properties, electronic band structure, laser damage threshold, and hardness of the GSP crystal were comprehensively investigated. It exhibited a disordered structure due to the random distribution of Sr and Gd atoms in the same Wyckoff site, which caused inhomogeneous spectral broadening. Additionally, it exhibited a short UV absorption cutoff edge (<200 nm), a large band gap (5.81 eV), and a high laser damage threshold (â¼1850 MW/cm2). The spectral properties and Judd-Ofelt calculations of the Nd:GSP crystals were analyzed. A wide absorption band at 803 nm, with a full width at half-maximum value of 20 nm, makes the Nd:GSP crystal suitable for the efficient pumping of AlGaAs laser diodes. Sub-100-fs pulses could be supported by its 25 nm emission bandwidth. Hence, the GSP crystal could be a promising disordered crystal laser matrix.
