<p>This study proposes a novel coupled energy storage system operating in coordination with coal-fired power plants (CFPPs), aiming to enhance power system peak-shaving capability and operational flexibility. By effectively integrating Brayton-cycle-based thermal energy storage with compressed air energy storage, the proposed system enables graded utilization of thermal energy and synergistic storage of pressure energy, achieving a high overall efficiency within a limited land footprint. A comprehensive thermodynamic model is developed, and integrated energy, exergy, economic, and environmental analyses are conducted. The results indicate that the system achieves a round-trip efficiency of 65.23%. Exergy analysis reveals that the total exergy losses during the charging and discharging processes are 21.2 MW and 12.2 MW, respectively, with compression and throttling processes identified as the dominant sources of irreversibility. From an economic perspective, the system exhibits a net present value of 308.5×10⁶ USD and a dynamic payback period of 6.6 years, demonstrating favorable economic feasibility. In terms of environmental benefits, the proposed system extends the operational load range of CFPPs to 0%–119.4%, facilitating the integration of 525 MWh of renewable energy under a typical daily scenario and reducing CO₂ emissions by approximately 268.8 tons. Parametric sensitivity analysis further shows that system efficiency improves with enhanced component performance and optimized operating parameters, while the selection of the split ratio requires a trade-off between efficiency improvement and air storage capacity. This study provides an environmentally friendly energy storage solution for improving thermal power flexibility and supporting high renewable energy penetration.</p>