Nitrogen-Doped Amorphous Carbon/Dual-Phasic TiO₂ Nanocomposite Electrodes Derived from Ti-Based Metal-Organic Frameworks Designed with a Mixed Linker Combination for High-Rate Lithium Storage

The development of high-capacity and high-rate electrode architectures is key to improving the performance of rechargeable lithium-ion batteries. However, developing an electrode design technology that satisfies the requirements of both high capacity and high rate capability remains challenging. Herein, we propose a creative synthesis design approach that controls the bronze/anatase dual-phasic TiO₂-embedded nitrogen-doped amorphous carbon nanocomposite (DP-TiO₂@NC) architecture, which was derived from a mixed linker NH₂-MIL-125 platform via a unique two-step pyrolysis process. The rationally controlled mixed ligands were based on H₂BDC-NH₂ and H₂BDC and demonstrated the ability to tune the nitrogen-doping configuration of amorphous carbon frameworks, thereby enhancing the electronic conductivity of the carbon frameworks. Remarkably, DP-TiO₂@NC derived from NH₂-MIL-125 using a 5:1 ratio of H₂BDC-NH₂/H₂BDC showed optimized battery performance (595 mA h g^-1@0.1 A g^-1 and 250 mA h g^-1@10 A g^-1) due to the improved electronic conductivity of the amorphous carbon framework and the synergetic storage effect of the nano-heterojunctions in DP-TiO₂. In addition, mixed linker MIL-125-derived DP-TiO₂@NC electrodes showed an excellent capacity retention of 95% even under harsh conduction [10 A g^-1 (≈30 C)] after 6000 cycles. This study demonstrates that the mixed ligand strategy for metal-organic framework-derived electrodes is a highly useful approach for designing efficient electrode architectures.