Obtenção de eletrólito sólido vitrocerâmico NaSICON do sistema Na(₁₊ₓ)Ge₂(SiO₄)ₓ(PO₄)₃₋ₓ via power ramp flash crystallization (PRFC)

Abstract

Lithium-ion batteries dominate electronics and vehicles due to their high density and durability, but concerns about safety, lithium scarcity, and high cost are driving the search for alternatives. Solid-state sodium-ion batteries are emerging as promising options; this combination is seen as a sustainable and viable solution to replace lithium without loss of storage capacity. One of the main challenges to enabling this technology is obtaining materials with high ionic conductivity, via synthesis methods that are fast, reliable, and energy-efficient. This work seeks to contribute in this context by exploring the improvement of glass-ceramics of the NaSICON family (“Na Super Ionic Conductor”) of the composition group Na(₁₊ₓ)Ge₂(SiO₄)ₓ(PO₄)₃₋ₓ, known for their crystalline structure favorable to ion transport, which generates excellent ionic conductivity at high temperatures (300 °C). For this, an innovative electric-field-assisted crystallization technique with controlled power increase will be employed. This technique is called power ramp flash crystallization (PRFC). The hypothesis is that it is possible to crystallize NaSICON glass-ceramics in a few minutes using this technique, maintaining or even improving their conductive properties, resulting in materials with ionic conductivity equal to or higher than those obtained by conventional crystallization methods. The samples were crystallized with a power ramp of 0.5 mW mm⁻³ s⁻¹ and variation in final power (22 to 39 mW mm⁻³) and hold time (60 and 300 s). The results demonstrated high conductivities on the order of 10⁻⁵ S cm⁻¹ at 250 °C, similar to values obtained by conventional crystallization. Impedance spectroscopy revealed notable differences in the resistive behavior of the grain and grain boundary between samples obtained via PRFC and conventional crystallization. The results indicate that the PRFC technique is very promising for producing the crystalline phase in reduced processing times.