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.
Keywords: battery safety; cathode-electrolyte interphase; dual-salt electrolyte; lithium-ion batteries; single crystal.