Electrochemical Performance of Sol-Gel Synthesized NaTi₂(PO₄)₃- Carbon Composites as Aqueous Na-Ion Battery Anodes

Abstract

Aqueous Na-ion based batteries are considered promising candidates for replacing Li-ion technologies, especially in the area of stationary energy storage. Research and development of novel electrode materials remain a central research effort in this field. NASICON-structured NaTi2(PO4)3 phosphate framework has attracted a great deal of attention and remains the most studied negative electrode material for aqueous Na-ion batteries. The active material preparation and carbon composite property tailoring play a critical role in the electrode materials engineering process which governs the performance of an entire electrochemical system. We present a study of a series of aqueous sol-gel synthesized NaTi2(PO4)3—carbon composites using three different sol-gel approaches and three distinct pyrolysis/calcination strategies. The structural and morphological analysis shows that both the sol-gel route as well as the thermal treatment strategy have significant effects on active material purity and degree of crystallinity as well as the content and properties of the carbonaceous phase. Electrochemical investigations of these composites also show strong effects of the materials structure and carbon matrix morphology on the electrochemical performance and degradation of these materials when employed as aqueous Na-ion battery negative electrodes.

Polydopamine Derived NaTi2(PO4)3–Carbon Core–Shell Nanostructures for Aqueous Batteries and Deionization Cells

“…It has also been shown that the growth of an aqueous interphasal layer during cycling is much more pronounced in higher-carbon-content, more-porous structures. 6 ■ CONCLUSIONS…”

“…NASICON-structured NaTi 2 (PO 4 ) 3 (NTP), with a potential of ca. −0.6 V (vs SHE) and a theoretical specific capacity of 133 mAh/g, is one of the most popular and widely studied negative electrode materials for various aqueous electrochemical devices such as Na-ion batteries or Faradaic deionization cells. − The improvement of NTP electronic conductivity is very important for the applications of this material in real electrochemical devices where high currents must be sustained for extended periods of time . Some attempts to enhance the electronic conductivity focused on reducing the particle size, aliovalent doping, and particle coating with various conductive materials. − …”

“…The resulting materials are characterized in terms of their structure, morphology and electrochemical properties. The obtained results are compared to those obtained by a conventional route based on citric acid (CA). − In the latter procedure, NTP particles are simply dispersed in CA solution and then pyrolyzed in inert gas atmosphere . The main differences between the two carbon encapsulation approaches are schematically compared in Figure .…”

Solvothermal Engineering of NaTi2(PO4)3 Nanomorphology for Applications in Aqueous Na-Ion Batteries

“…Various aspects of the sol−gel technique for preparing NTP on the material purity, degree of crystallinity, and properties of carbonaceous phase were recently investigated. 10 Hydro(solvo)thermal synthesis is widely regarded as one of the most suitable soft chemical methods for preparing battery materials yielding high phase purity and crystallinity, narrow particle size distribution, and the ability to finely control particle morphology and agglomeration. 11 All of this allows the design of particles with shorter ionic and electronic transporting paths leading to better electrochemical and charge storage properties.…”

“…On the other hand, sol–gel synthesis is another simple, scalable, and widely used method. Various aspects of the sol–gel technique for preparing NTP on the material purity, degree of crystallinity, and properties of carbonaceous phase were recently investigated . Hydro­(solvo)­thermal synthesis is widely regarded as one of the most suitable soft chemical methods for preparing battery materials yielding high phase purity and crystallinity, narrow particle size distribution, and the ability to finely control particle morphology and agglomeration .…”