Enhancing high-temperature storage performance for the commercial lithium-ion battery via an effective additive strategy

Lithium-ion batteries play an irreplaceable role in energy storage systems. However, the storage performance of the battery, especially at high temperature, could greatly affect its electrochemical performance. Herein, the storage performance of LiCoO2/graphite full cells under 30% state-of-charge (SOC) and 100% SOC at 45 °C are investigated by introducing a methylene methane disulfonate (MMDS) electrolyte additive into the standard electrolyte (STD). The interfacial stability between the electrolyte and the storage electrode is significantly improved after adding the MMDS (1 wt%) additive, as demonstrated by the electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) analysis. As a result, the capacity retention rate and capacity recovery rate of this battery at 30% SOC/100% SOC after 3 months of storage at 45 °C were raised by 2.48%/3.14%, and 2.97%/2%, respectively, compared to the battery with STD. Moreover, the quantitative analysis of the graphite anode showed that the modified electrolyte reduced the content of dead lithium (CODL) and cobalt in the graphite anode by atomic absorption spectrometer (AAS). At 45 °C, after storing for 3 months under 30% SOC, the CODL value decreased from 1.45% to 1.07%, while under 100% SOC and the same storage time, that value only decreased from 1.49% to 1.089%. It indicates that the MMDS additive is a useful electrolyte additive for Li-ion cells in improving its high-temperature storage performance.