Lithium insertion/desertion properties of LiFePO₄ cathode in a low temperature electrolyte modified with sodium chloride additive

Sodium chloride (NaCl), as an attractive electrolyte additive, was added in a low temperature electrolyte to investigate its effect on LiFePO₄ electrode. A capacity as high as 115 mAh g^{- 1} was delivered at 2 C, which was 20 mAh g^{- 1} more than its NaCl free counterpart. Cyclic voltammetry (CV) tests showed that the polarization of electrode reaction decreased. SEM and XPS measurements were conducted and the result illustrated that the film was modified by NaCl to be uniform containing less resistive LiF, so the transport of Li⁺ through the film was facilitated. Moreover, the conductivity of Li⁺ through electrolyte was also enhanced in the presence of NaCl. NaCl effectively facilitated lithium ion transport rate to the electrode surface and improved the lithiation/delithiation behavior in the LiFePO₄ electrode.