Nanodiamond‐Assisted High‐Performance Sodium‐Ion Batteries with Weakly Solvated Ether Electrolyte at −40 °C

Realizing high performances of sodium‐ion batteries (SIBs) working at low temperatures is a pressing need for the commercial applications of SIBs. In this work, nanodiamonds (NDs) are introduced in diglyme electrolytes (ND‐Diglyme) to significantly improve the low‐temperature performances of SIBs. The corresponding SIB achieves an initial reversible specific capacity of 324 mA h g−1 at −40 °C (slightly decreased from 357 mA h g−1 at 25 °C) and shows a capacity retention ratio of ≈82% after 100 cycles at 0.1 A g−1. Moreover, it shows a capacity as high as 40 mA h g−1 at 1 A g−1, nearly five times the date of the pure Diglyme electrolyte. Experimentally reveals that introducing NDs is helpful in inhibiting dendrite growth and improving the cyclic stability of anode at LT, because the ND with strong adsorption to sodium ions can not only assist in forming an effective solid electrolyte interface rich with NaF and Na2CO3 but also effectively reduce the activation energy (decreased from 426.68 to 370.51 meV) during the charge transfer processes. Hence, the proposed ND‐assisted weakly ether electrolyte in this study presents a viable electrolyte additive solution to fulfill the rising low‐temperature demands of SIBs.