Explosion of lithium-ion battery vent gas (BVG) has caused catastrophic incidents in confined spaces such as aircraft cargo holds and battery energy storage systems. This study experimentally investigates the premixed explosion behavior of BVG with two representative suppression gases: CO₂ and 2H-Heptafluoropropane (HFC-227ea, CF3CHFCF3). The critical suppression concentration of HFC-227ea is significantly lower than that of CO₂. Unexpectedly, insufficient HFC-227ea were found to increase explosion pressure. Fortunately, this adverse effect was effectively mitigated by the addition of CO₂. Motivated by the intrinsic coupling between kinetics and flame propagation, this study provides new insights into the coexistence of explosion enhancement and suppression. From a flame dynamics perspective, insufficient HFC-227ea exacerbates flame instability and promotes heat transfer. Kinetically, HFC-227ea competes with BVG for O₂, scavenges key radicals, and inhibits reverse reactions that regenerate radicals. However, this also leads to the generation of CO and HF, significantly increasing the total amount of burned gas—a dominant factor in pressure enhancement. Under initial conditions of 300 K and atmospheric pressure (approximately 0.1 MPa), CO₂ mitigates both flame disturbances and product-gas generation, especially when its proportion in the suppressant mixture exceeds 50%. When the volumetric ratios of CO₂ to HFC-227ea are 5:5 and 7:3, the explosion enhancement effect is reduced by 37% and 49%, respectively. Beyond these findings, the proposed numerical framework has been experimentally validated and is extendable to future investigations of BVG explosion across different battery chemistries.