Synergistic Dual-Salt Electrolyte for Safe and High-Voltage LiNi₀.₈Co₀.₁Mn₀.₁O₂//Graphite Pouch Cells
2022
Wu, Changjun | Wu, Yu | Xu, Xiaodong | Ren, Dongsheng | Li, Yalun | Chang, Runze | Deng, Tao | Feng, Xuning | Ouyang, Minggao
Concerns about thermal safety and unresolved high-voltage stability have impeded the commercialization of high-energy lithium-ion batteries bearing LiNi₀.₈Co₀.₁Mn₀.₁O₂ (NCM811) cathodes. Enhancing the cathode structure and optimizing the electrolyte formula have demonstrated significant potential in improving the high-voltage properties of batteries while simultaneously minimizing thermal hazards. The current study reports the development of a high-voltage lithium-ion battery that is both safe and reliable, using single-crystal NCM811 and a dual-salt electrolyte (DSE). After 200 cycles at high voltage (up to 4.5 V), the capacity retention of the battery with DSE was 98.80%, while that for the battery with a traditional electrolyte was merely 86.14%. Additionally, in comparison to the traditional electrolyte, the DSE could raise the tipping temperature of a battery’s thermal runaway (TR) by 31.1 °C and lower the maximum failure temperature by 76.1 °C. Moreover, the DSE could effectively reduce the battery’s TR heat release rate (by 23.08%) as well as eliminate concerns relating to fire hazards (no fire during TR). Based on material characterization, the LiDFOB and LiBF₄ salts were found to facilitate the in situ formation of an F- and B-rich cathode-electrolyte interphase, which aids in inhibiting oxygen and interfacial side reactions, thereby reducing the intensity of redox reactions within the battery. Therefore, the findings indicate that DSE is promising as a safe and high-voltage lithium-ion battery material.
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