Multi-cation engineering of Li₁₂₈Nb₃₂O₁₄₄ anodes via first-principles design for sustainable energy storage

• Trimetallic doping lowers band gap and boosts conductivity • Trimetallic (V/W/Co) doping lowers band gap by 1.13 eV • Strong charge transfer enhances Li storage stability • Improved voltage and structural integrity for LIBs The rational design of stable, high-rate anode materials requires atomic-level control over electronic and ionic transport. Here, we employ a first-principles-guided strategy to engineer hetero-metallic doping in Li-rich lithium niobate based Li 128 Nb 32 O 144 , a promising yet underexplored alternative to conventional anodes. Systematic screening of mono-, bi-, and trimetallic dopants (V, Co, Cr, Bi, As and W) reveals that trimetallic (V/W/Co) doping optimally reduces the band gap by 0.13 eV. Charge density analysis indicates enhanced delocalization around Nb and Li sites, while V/Bi substitution minimizes lattice strain (ΔV < 2%). Phonon spectra and formation energy calculations suggest thermodynamic favorability of mono-doped (Bi, As), bi-doped (V, Bi), and trimetallic (V, W, Bi) variants. Notably, V doping lowers the molar heat capacity by 1.1% (ΔCₚ = 5.8 J/mol·K), indicating improved thermal management. These findings establish a clear hierarchy of dopant effects, demonstrating that tri-metallic systems outperform mono- and bimetallic analogs in terms of mechanical strength (bulk modulus > 150 GPa) and relative phase stability, both of which are critical for fast-charging applications. This work provides a blueprint for leveraging multi-cation doping to unlock the potential of complex oxide anodes.