Variation characteristics of electrolyte by-product DMDOHC in lithium-ion batteries under overcharge

Lithium-ion batteries will inevitably undergo aging during long-term use. Especially under the condition of overcharged electrical abuse, the electrolyte decomposes to produce a series of aging products. In this paper, 2,5-dioxahexanedioic acid dimethyl ester (DMDOHC) is taken as an example to explore the relationship between the substance and the battery electrochemical aging process under overcharge conditions based on Raman spectroscopy. Firstly, establish a Raman detection platform and prepare electrolyte samples with different concentrations of DMDOHC. Select characteristic peaks through Raman detection for subsequent analysis. On this basis, a LiFePO₄ battery simulation device is used as the experimental basis to conduct cycling experiments on lithium-ion batteries under different charge cut-off potentials and cycle periods. It is found that with the increase of the cut-off voltage, the content of DMDOHC increased (from 144.07 ppm at 3.8 V to 553.28 ppm at 4.4 V), and the capacity decay rate of the battery is accelerated. There is also a positive correlation between the content of DMDOHC and the number of battery cycles, and the DMDOHC content shows the most significant growth at 4.4 V. The experimental results show that the concentration of DMDOHC can be used as an indicator of the battery aging process, which provides a theoretical basis for further health status evaluation of lithium-ion batteries.