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

• 1% NaCl is added into electrolyte in this work.
• Discharge capacity at 2 C increases by 20 mAh g− 1, with smaller voltage hysteresis.
• The conductivity of Li+ in electrolyte increases by one time.
• The SEI film is modified to be much uniform containing less resistive LiF.
• NaCl additive enhances lithiation/delithiation reaction during the C/D processes.

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.