Abstract: Battery energy storage devices serve as the core for secure and stable operation of distribution networks, yet their large-scale deployment raises significant safety concerns. To address the lack of systematic testing and quantitative analysis regarding the thermal runaway suppression effects of single-sided/double-sided ceramic-coated separators in large-capacity lithium iron phosphate (LFP) cells under typical abuse conditions, this research is carried out to fill the gap. Taking 280 A·h LFP cells equipped with single-sided and double-sided ceramic-coated separators respectively as research objects, three categories of abuse-induced thermal runaway tests are systematically implemented, including nail penetration, overheating (ignition/non-ignition comparison), and overcharge (ignition/non-ignition comparison). Based on thermal runaway theory, characteristic indicators such as voltage evolution, temperature rise, gas generation, mass loss, and heat release are measured to quantitatively compare the suppression performance. The results show that cells with double-sided ceramic-coated separators exhibit remarkably superior safety performance compared with those adopting single-sided ceramic separators. Under the 6 mm nail penetration condition: the thermal runaway duration is extended by 85 s, the peak surface temperature decreases by 18 ℃, and a self-cutting effect characterized by voltage drop–recovery is observed. For overheating tests: under non-ignition conditions, thermal runaway duration increases by 57 s, peak temperature drops by 73 ℃, and the concentration of flammable gases is reduced; under ignition conditions, the duration extends by 102 s, peak temperature falls by 104 ℃, the peak heat release rate decreases by 45 kW, and the mass loss rate drops substantially. Voltage rebound is captured in both cases. For overcharge tests: under non-ignition conditions, thermal runaway duration increases by 12 s and peak temperature reduces by 19 ℃; under ignition conditions, the duration extends by 14 s, peak temperature drops by 20 ℃, and the peak heat release rate declines by 45 kW. Moreover, the peak overcharge voltage rises by up to 24.4 V, and the accumulated charged capacity before internal short circuit is significantly lowered. It can be concluded that the double-sided ceramic-coated separator can effectively suppress the initiation and propagation of early micro-short circuits inside batteries. These findings can provide reliable experimental support and theoretical basis for the safety design of large-capacity energy storage batteries, and bears significant engineering value for ensuring the safe operation of energy storage systems on distribution network side.