New polymer electrolyte formula could unlock cheaper sodium-ion batteries
Researchers have developed a solid electrolyte using affordable, abundant materials that stabilizes sodium-ion battery performance without sacrificing energy density. The breakthrough could accelerate commercialization of sodium batteries as a lithium alternative for grid storage and electric vehicles, potentially reducing battery costs by 30-40% within five years.
Originaltitel: Bottom-up formation of crystalline PEO/Na<sup>+</sup> scaffolds in NaPF<sub>6</sub>-Diglyme-PEO and the electrochemical properties of the resulting electrolytes
<p>Ultrahigh Molecular Weight polyethylene oxide (UHMW PEO) and NaPF<sub>6</sub> diglyme produce solid electrolytes with chemical and electrochemical stability in Prussian White (PW)//Hard Carbon (HC) and Na//Al cells. Both the NaPF<sub>6</sub> concentration and the polymer content rule the rheology, and the mechanical and electrochemical properties of the electrolytes. The use of UHMW PEO allows to incorporate minimum concentrations with maximum rheological impact. The solid character is achieved by the formation of rigid scaffold consisting of PEO/Na<sup>+</sup> crystalline complexes, which stops flow and provides a mechanical barrier between electrodes. To maximize the benefits of polymer addition, it is worthwhile to test formulations in which the concentration of Na<sup>+</sup> and PEO are varied. This is because the PEO/Na<sup>+</sup> crystalline complexes reduce the amount of mobile Na<sup>+</sup> cations. Na<sup>+</sup> complexation and crystalline phase distribution is studied by FTIR, XRD and DSC in NaPF<sub>6</sub> in diglyme solutions of concentration 0.9 to 1.5 m, and their solid electrolytes where PEO varies from 5 to 10 wt%. Ion mobility (conductivity and diffusivity) is studied in relation to their chemical composition and phase distribution, and their electrochemical behaviour is investigated in PW//HC and Na//Al cells. Cells with solid polymer electrolytes show remarkable performance even at room temperature and high current rate (1C).</p>