Breaking the passivation–conduction deadlock: Al2O3 and TaC as a complementary pair for 4.5 V LiCoO2

LiCoO 2 (LCO) possesses a high volumetric energy density, but commercial LCO delivers a capacity of only 140–165 mAh g −1 at a low voltage of 4.3 V, failing to realize its advantage. When the voltage is increased above 4.4 V, rapid capacity fading occurs due to structural and interfacial instability. This work proposes a simple and industrially compatible mechanical mixing strategy, in which Al 2 O 3 and TaC are directly incorporated into LCO to construct a composite cathode, thereby achieving stable cycling of the LCO cathode at 4.5 V. Al 2 O 3 suppresses side reactions, while TaC constructs an electron/thermal transport pathway that reduces polarization and dissipates localized Joule heat. The modified LCO-TA11 cathode achieves a capacity retention of 84.8% after 200 cycles at 4.5 V, far superior to that of pristine LCO. Even after 200 cycles at 45 °C, the retention remains as high as 79.1%, and a specific capacity of 145.6 mAh g −1 is delivered at a high rate of 10C. When assembled into a pouch cell with a graphite anode, accelerating rate calorimetry (ARC) tests show that the temperature rise during charging and discharging is reduced by 4.43 °C and 6.09 °C, respectively. This work resolves the functional conflict between interfacial passivation and electrical/thermal conduction inherent in single materials through a one-step mechanical mixing strategy, achieving synergistic suppression of side reactions and heat accumulation, and providing a viable pathway toward low-cost, high-safety, and long-life cathode materials for consumer electronic batteries.