Ammonium polyphosphate enabling nonflammable practical high-nickel cells: Performance verification and mechanism analysis

High-nickel batteries exhibit prominent thermal safety issues. Low-cost ammonium polyphosphate (APP) flame-retardant additive offers a promising solution. Nonetheless, its effect on the performance and mechanism remains uncertain. Therefore, this study investigates the effects of APP adding in electrolytes on the electrochemical performance, safety, and interface of 1 Ah LiNi_0.9Co_0.05Mn_0.05O₂/Graphite@10%SiO pouch cells. The cell does not catch fire with 10% APP during thermal abuses. The capacity retention rates of the cells with 5% and 10% APP are 96.9% and 96.8% after 137 cycles at 0.5 C. The decrease of the capacity retention rate is primarily due to the thickening of the electrode interface leading to loss of active lithium. When using a 5% addition, the overall performance is better than 10%. This study serves as a simple and promising strategy for mitigating thermal runaway in high-specific-energy power batteries.