Bypassing desolvation step ensures fast intercalation chemistry for titanate-based capacitors endured at −60 °C

Abstract

Subzero temperature (subzero-T) performance of the sodium-ion hybrid capacitors (SIHCs) is severely limited by the sluggish ion desolvation process of faradic anodes based on intercalation chemistry. To conquer the obstacle, a desolvation-free SIHCs based on co-intercalation chemistry and anion adsorption is constructed, which essentially circumvent the most restrictive desolvation step. The theoretical calculations combined with experimental characterization interprets the co-intercalation possibility of sodium titanate (NTO) and the relationship between oxygen vacancies and co-intercalation chemistry. The redistributed charge in short-range with weakened polarization effect and reduced Fermi level of the entire crystal make Na⁺-diglyme co-intercalation easier and more reversible. Particularly, the disordered “valve” interface significantly reduces diffusion energy barrier, lowers bulk impedance, and generates high-quality SEI film, therefore, the subzero-T working ability of NTO has been sufficiently improved. As expected, the constructed desolvation-free SIHCs exhibit superior temperature compatibility and extraordinary cycling stability, maintaining capacitance retention of 74 % after 20,000 cycles at −40 °C and cycling over 10,000 cycles with a capacitance retention of 78 % at −60 °C. This work extends the understanding of the co-intercalation chemistry in host materials and provides insights for designing a better subzero-T energy storage system.