Currently adding a suitable additive in the electrolyte is one of the most effective strategies to improve the electrochemical performance for a lithium-ion battery, especially under high temperature. In this work, N,Ndimethylformamide (DMF) as an electrolyte additive was introduced to improve the battery performance of LiFePO 4 at 60 °C. The addition of DMF can effectively increase the specific capacity, cycling performance, and rate performance of batteries using LiFePO 4 as cathode material. X-ray diffraction results reveal that for the electrode cycled in the electrolyte without additive, Fe 2 O 3 , FePO 4 , and other impurity peaks appear under high temperature. scanning electron microscopy/transmission electron microscopy results indicate that some deposits are generated on the electrode surface without additive under high temperature due to the decomposition of electrolyte in the reaction between electrolyte and electrode materials. The Fourier transform infrared spectroscopy/NMR/X-ray photoelectron spectroscopy results demonstrate that DMF as a lewis base can capture lewis acidic PF 5 from the decomposition of LiPF 6 as well as block the chain reaction of LiFePO 4 with hydrogen fluoride, which alleviates the electrolyte decomposition and electrode dissolution at high temperature.

Severe electrolyte decomposition under high voltage can easily lead to degradation of the performance of lithium-ion batteries, which has become a major obstacle to the practical application of high-energy-density batteries. To solve these problems, a dual-functional electrolyte additive comprising inorganic lithium difluorophosphate (LiDFP) and organic 1,3,6-hexanetrinitrile (HTN) was designed and employed to improve the performance of high-voltage Si@C/LiNi 0.5 Mn 1.5 O 4 full batteries. LiDFP with a lower LUMO energy than the solvent in the electrolyte takes priority in reduction, facilitating the formation of a dense and stable film on the anode, effectively suppressing side reactions of the electrolyte and aiding tolerance to the volume expansion of the Si@C electrode. Additionally, the lower HOMO energy of HTN can improve the oxidation resistance of the electrolyte, with the CN functional group of HTN helping to remove the trace water and the byproduct HF from the electrolyte. The Si@C/LiNi 0.5 Mn 1.5 O 4 full battery with 1 wt % LiDFP and 1 wt % HTN in 1.0 M LiPF 6 traditional electrolyte delivers high capacity retention of 91.57% after 150 cycles at 0.2C, compared to 34.58% capacity retention without any additives. Moreover, the Coulombic efficiency of batteries with electrolyte additives can reach 99.75% on average, compared to their counterparts at ∼96.54%. The synergistic effect of LiDFP and HTN provides a promising strategy for enhancing the performance of high-voltage batteries for practical industrialization.

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1-(2-Cyanoethyl)pyrrole electrolyte additive via a capturing strategy enables high-performance of lithium-ion batteries at high temperature.